This document discusses using HZSM-5 modified with citric acid as a heterogeneous acid catalyst for biodiesel production via esterification of oleic acid. The study evaluates the effect of citric acid treatment conditions on the structural, textural and acidity properties of HZSM-5. Citric acid is used to selectively remove aluminum from the external layers of the zeolite crystal. Characterization techniques show the treatment improves the external acidity and creates mesoporosity, benefiting the esterification reaction which occurs on the external surface. The modified catalysts show improved performance in esterifying oleic acid compared to the untreated HZSM-5.
Sulfonic-based precursors (SAPs) for silica mesostructures: Advances in synth...Iranian Chemical Society
This document summarizes recent advances in the synthesis and applications of sulfonic acid-based precursors (SAPs) for functionalizing silica mesostructures. It discusses four main methods for preparing SAPs and incorporating them into mesoporous silica, with a focus on propylsulfonic acid and sulfamic acid precursors. Applications of SAP-functionalized mesoporous silicas include catalysis of organic reactions like esterification, Friedel-Crafts alkylation, and multi-component syntheses. The document highlights efforts to control the surface activity and hydrophobicity of SAP-functionalized silica catalysts to improve their reactivity and recyclability.
Synthesis And Evaluation of Different Numbers of Phosphonate Group Containing...inventionjournals
Oil fields were seriously affected by the mineral scale formation, mainly calcium deposition. This paper focused on the synthesis and scale prevention of oilfield scaling, especially carbonates scale and sulfate scale. Scale can cause loss of production due to blockages in the near-well formation, in the tubing or in the surface facilities. Phosphonates are widely accepted as the most effective inhibitors for calcium carbonate and calcium sulfate, also are widely used in many water treatment applications. Most good scale inhibitors should work at dosage levels between 5 and 25 ppm on most production systems depending on calcium concentration. The treatment rates can be affected by contaminants which take the scale inhibitor out of solution. Six different compounds of phosphonate containing groups have been synthesized and evaluated for scale inhibition property. Evaluation of synthetic phosphonate compounds as scale inhibitors has been done by using NACE Standard TM-0374-2001. From the results clear that one and two phosphonate group containing compounds do not show any characteristic of prevention of scales of either calcium carbonate or calcium sulphate. The compounds which have phosphonate group three or more show characteristics of prevention of both types of scales.
Starch is a natural polymer that is renewable and biodegradable. However, it has poor processability and mechanical properties on its own. This document discusses how starch can be combined with synthetic biodegradable polymers like polylactide (PLA) and polycaprolactone (PCL) to create completely biodegradable polymer materials with improved properties. The polymers are blended physically or chemically modified starch is combined. These starch-based completely biodegradable polymers (SCBP) have potential applications in biomedical and environmental fields due to their low cost, biodegradability and ability to reduce consumption of petroleum resources.
1) The document describes a study that investigates the esterification of palm fatty acid distillate (PFAD) using a heterogeneous sulfonated microcrystalline cellulose catalyst and compares it to using sulfuric acid as the catalyst.
2) The solid catalyst was characterized and tested under various conditions of catalyst loading, temperature, and fatty acid to methanol ratio. Sulfuric acid performed better but the solid catalyst allows for easier recovery and reusability.
3) The kinetics of the esterification reaction were analyzed considering the biphasic liquid-liquid nature of the system that forms, with the two phases reaching equilibrium, in both catalyst systems.
This research article investigates carboxymethyl starch (CMS) as a pH-responsive excipient for delayed drug delivery systems. Two forms of CMS - sodium CMS and protonated CMS - were synthesized and formulated into monolithic and dry-coated tablets with three model drugs. In vitro dissolution tests showed that protonated CMS tablets were more stable in simulated gastric fluid, while both forms provided gastric protection when in dry-coated tablets. Drug release mechanisms in simulated intestinal fluid differed between the two CMS forms and were affected by the addition of pancreatic enzymes. Overall, both sodium and protonated CMS dry-coated tablets demonstrated good gastric protection and controlled drug release up to 4-5 hours, indicating potential as a solvent-free enteric coating
Ionic liquids as novel surfactants for the potential use in enhanced oil reco...Khalid Al-Khidir
Ionic liquids as novel surfactants for potential use in enhanced oil recovery
Mohammed Said Benzagouta*,†, Inas Muen AlNashef**, Wimpy Karnanda*, and Khalid Al-Khidir*
*Department of Petroleum and Natural Gas Eng, King Saud University,
**Department of Chemical Engineering, King Saud University, Kingdom of Saudi Arabia
(Received 15 May 2013 • accepted 27 July 2013)
Abstract−The screening and use of benign chemicals for enhanced oil recovery (EOR) applications is important
because of their properties and relationship to the embedded fluids. We investigated a special type of ionic liquids (ILs) called ‘‘Ammoeng” for potential use in surfactant EOR to replace the currently used surfactants that have many disadvantages. The interfacial tension (IFT) between a representative oil sample from Saudi reservoirs and solutions of AmmoengTM ILs at different concentrations in 10 wt% NaCl aqueous solutions were measured as a function of temperature. It was found that the IFT values decreased with the increase of IL concentration. However, the effect of temperature
on the IFT depended on the type of IL. AmmoengTM 102 gave the lowest IFT values among the screened ILs.
The comparison of the results to those resulting from TritonX100, a commercially used surfactant, showed that theIFT values using AmmoengTM 102 were smaller than the corresponding values when TritonX100 was used at the sameconditions. The possibility of having a synergetic effect when using a mixture of AmmoengTM 102 and Triton X 100 was also investigated. The results showed that the IFT values depended on the total concentration, the surfactant toIL mass ratio, and the temperature.
Utilization of jarosite generated from leadtp jayamohan
Large quantities of industrial waste by-products are produced in India by different type of industries viz. Jarosite, Jarofix, Copper slag, Zinc slag, Red mud, Steel slag and Coal ash. For many years these materials were considered as waste and were dumped haphazardly near the producing plants. Efforts are being carried out by research studies to utilize these materials in embankment, sub base and base layers of road construction. Experimental studies have been also carried out to investigate their feasibility as an additive in cement concrete. Jarosite material is produced during extraction of zinc ore concentrate by hydrometallurgy operation. When zinc ore concentrate is roasted at 9000 C and subjected to leaching, Jarosite is formed as a waste material. The Jarosite material is mixed with 2 % lime and 10 % cement and transported to the disposal area as a Jarofix material.
This document describes the synthesis and characterization of a series of anionic liposaccharide derivatives intended to act as absorption enhancers and improve oral bioavailability of drugs. The liposaccharides were designed with a lipophilic lipid side chain and a hydrophilic head containing glucose and glutamic acid. Isothermal titration calorimetry was used to determine the critical aggregation concentrations and thermodynamic profiles of the liposaccharides. Two liposaccharides formed nanoparticles below 100 nm and had critical aggregation concentrations below 0.325 mM, indicating favorable aggregation in aqueous solution driven by entropy.
Sulfonic-based precursors (SAPs) for silica mesostructures: Advances in synth...Iranian Chemical Society
This document summarizes recent advances in the synthesis and applications of sulfonic acid-based precursors (SAPs) for functionalizing silica mesostructures. It discusses four main methods for preparing SAPs and incorporating them into mesoporous silica, with a focus on propylsulfonic acid and sulfamic acid precursors. Applications of SAP-functionalized mesoporous silicas include catalysis of organic reactions like esterification, Friedel-Crafts alkylation, and multi-component syntheses. The document highlights efforts to control the surface activity and hydrophobicity of SAP-functionalized silica catalysts to improve their reactivity and recyclability.
Synthesis And Evaluation of Different Numbers of Phosphonate Group Containing...inventionjournals
Oil fields were seriously affected by the mineral scale formation, mainly calcium deposition. This paper focused on the synthesis and scale prevention of oilfield scaling, especially carbonates scale and sulfate scale. Scale can cause loss of production due to blockages in the near-well formation, in the tubing or in the surface facilities. Phosphonates are widely accepted as the most effective inhibitors for calcium carbonate and calcium sulfate, also are widely used in many water treatment applications. Most good scale inhibitors should work at dosage levels between 5 and 25 ppm on most production systems depending on calcium concentration. The treatment rates can be affected by contaminants which take the scale inhibitor out of solution. Six different compounds of phosphonate containing groups have been synthesized and evaluated for scale inhibition property. Evaluation of synthetic phosphonate compounds as scale inhibitors has been done by using NACE Standard TM-0374-2001. From the results clear that one and two phosphonate group containing compounds do not show any characteristic of prevention of scales of either calcium carbonate or calcium sulphate. The compounds which have phosphonate group three or more show characteristics of prevention of both types of scales.
Starch is a natural polymer that is renewable and biodegradable. However, it has poor processability and mechanical properties on its own. This document discusses how starch can be combined with synthetic biodegradable polymers like polylactide (PLA) and polycaprolactone (PCL) to create completely biodegradable polymer materials with improved properties. The polymers are blended physically or chemically modified starch is combined. These starch-based completely biodegradable polymers (SCBP) have potential applications in biomedical and environmental fields due to their low cost, biodegradability and ability to reduce consumption of petroleum resources.
1) The document describes a study that investigates the esterification of palm fatty acid distillate (PFAD) using a heterogeneous sulfonated microcrystalline cellulose catalyst and compares it to using sulfuric acid as the catalyst.
2) The solid catalyst was characterized and tested under various conditions of catalyst loading, temperature, and fatty acid to methanol ratio. Sulfuric acid performed better but the solid catalyst allows for easier recovery and reusability.
3) The kinetics of the esterification reaction were analyzed considering the biphasic liquid-liquid nature of the system that forms, with the two phases reaching equilibrium, in both catalyst systems.
This research article investigates carboxymethyl starch (CMS) as a pH-responsive excipient for delayed drug delivery systems. Two forms of CMS - sodium CMS and protonated CMS - were synthesized and formulated into monolithic and dry-coated tablets with three model drugs. In vitro dissolution tests showed that protonated CMS tablets were more stable in simulated gastric fluid, while both forms provided gastric protection when in dry-coated tablets. Drug release mechanisms in simulated intestinal fluid differed between the two CMS forms and were affected by the addition of pancreatic enzymes. Overall, both sodium and protonated CMS dry-coated tablets demonstrated good gastric protection and controlled drug release up to 4-5 hours, indicating potential as a solvent-free enteric coating
Ionic liquids as novel surfactants for the potential use in enhanced oil reco...Khalid Al-Khidir
Ionic liquids as novel surfactants for potential use in enhanced oil recovery
Mohammed Said Benzagouta*,†, Inas Muen AlNashef**, Wimpy Karnanda*, and Khalid Al-Khidir*
*Department of Petroleum and Natural Gas Eng, King Saud University,
**Department of Chemical Engineering, King Saud University, Kingdom of Saudi Arabia
(Received 15 May 2013 • accepted 27 July 2013)
Abstract−The screening and use of benign chemicals for enhanced oil recovery (EOR) applications is important
because of their properties and relationship to the embedded fluids. We investigated a special type of ionic liquids (ILs) called ‘‘Ammoeng” for potential use in surfactant EOR to replace the currently used surfactants that have many disadvantages. The interfacial tension (IFT) between a representative oil sample from Saudi reservoirs and solutions of AmmoengTM ILs at different concentrations in 10 wt% NaCl aqueous solutions were measured as a function of temperature. It was found that the IFT values decreased with the increase of IL concentration. However, the effect of temperature
on the IFT depended on the type of IL. AmmoengTM 102 gave the lowest IFT values among the screened ILs.
The comparison of the results to those resulting from TritonX100, a commercially used surfactant, showed that theIFT values using AmmoengTM 102 were smaller than the corresponding values when TritonX100 was used at the sameconditions. The possibility of having a synergetic effect when using a mixture of AmmoengTM 102 and Triton X 100 was also investigated. The results showed that the IFT values depended on the total concentration, the surfactant toIL mass ratio, and the temperature.
Utilization of jarosite generated from leadtp jayamohan
Large quantities of industrial waste by-products are produced in India by different type of industries viz. Jarosite, Jarofix, Copper slag, Zinc slag, Red mud, Steel slag and Coal ash. For many years these materials were considered as waste and were dumped haphazardly near the producing plants. Efforts are being carried out by research studies to utilize these materials in embankment, sub base and base layers of road construction. Experimental studies have been also carried out to investigate their feasibility as an additive in cement concrete. Jarosite material is produced during extraction of zinc ore concentrate by hydrometallurgy operation. When zinc ore concentrate is roasted at 9000 C and subjected to leaching, Jarosite is formed as a waste material. The Jarosite material is mixed with 2 % lime and 10 % cement and transported to the disposal area as a Jarofix material.
This document describes the synthesis and characterization of a series of anionic liposaccharide derivatives intended to act as absorption enhancers and improve oral bioavailability of drugs. The liposaccharides were designed with a lipophilic lipid side chain and a hydrophilic head containing glucose and glutamic acid. Isothermal titration calorimetry was used to determine the critical aggregation concentrations and thermodynamic profiles of the liposaccharides. Two liposaccharides formed nanoparticles below 100 nm and had critical aggregation concentrations below 0.325 mM, indicating favorable aggregation in aqueous solution driven by entropy.
2009 Alburquerque et al al composting and humficationGermán Tortosa
The document evaluates the composting of "alperujo", a wet solid byproduct of the Spanish olive oil industry, using different bulking agents and aeration strategies. It finds that composting performance was most influenced by the type of bulking agent added and number of turnings. Cotton waste and fresh cow bedding performed best as bulking agents, improving organic matter degradation and leading to quality compost. Forced ventilation alone was insufficient. The resulting composts had good nutrient content and stability, with low heavy metals, demonstrating that composting can treat "alperujo" and produce safe, beneficial organic amendments.
1) CHEMAF's cobalt plant in the Democratic Republic of Congo was experiencing decreased cobalt carbonate grade and increased reagent consumption due to rising magnesium levels in the ore feed, as dolomite concentration increased.
2) Laboratory tests evaluated different precipitation pH levels and precipitants to improve cobalt grade and reduce costs. Dual precipitation using sodium carbonate and sodium hydroxide improved filtration capacity by 30% and cobalt grade and drying capacity by 50%, while reducing reagent use by 22%.
3) Implementing precipitate seed recycle in the plant further increased magnesium rejection by 40%, cobalt grade from 20% to 25%, and reduced reagent consumption. Process changes successfully overcame challenges from high magnesium in
Phytosiderophores are organic compounds secreted by plants like grasses to chelate and absorb iron from the soil. They have a structure of two α-aminocarboxylate binding centers and a single α-hydroxycarboxylate unit which gives them a high selectivity for iron. Iron deficiency is common in calcareous soils due to the low solubility of iron compounds. Phytosiderophores help solubilize iron and transport it to the plant roots and tissues through nicotianamine. They are composed of mugineic acid family compounds and are synthesized from S-adenosyl methionine through nicotianamine. Phytosiderophores also help plants withstand heavy metal stress by
This document discusses a density functional theory study of the epimerization of glucose to mannose catalyzed by Sn-beta zeolite and borate salts. The study finds that the tetrahedral borate ion forms a complex with glucose that inhibits competitive isomerization. The stannanol group of Sn-beta catalyzes glucose ring opening, followed by enolization catalyzed by the silanol group. Epimerization then proceeds via an intramolecular 1,2 carbon shift, which is the rate-limiting step. Tin is found to be the most active metal center, and the proximity of the silanol group to the stannanol group enhances catalytic activity. The study aims to understand the cooperative roles of
Microemulsion – A Potential Carrier for Improved BioavailabilityBRNSS Publication Hub
This document summarizes microemulsions and their potential as drug delivery systems to improve oral bioavailability. Key points:
- Microemulsions are thermodynamically stable mixtures of oil, water, and surfactant that can solubilize poorly water-soluble drugs. Their small droplet size (<100 nm) allows improved drug absorption.
- Around 40% of new drug candidates have poor water solubility, resulting in low bioavailability. Microemulsions may help overcome this issue by enhancing solubility and permeability.
- Factors like surfactant concentration, oil/surfactant properties, and temperature can affect microemulsion phase behavior and transition between oil-in-water
Aluminum doped sba 15 silica as acid catalyst for the methanolysis of sunflow...Solange Quintella
The document summarizes research on using aluminum-doped SBA-15 silica materials as solid acid catalysts for the methanolysis (biodiesel production) of sunflower oil. Different Si/Al molar ratios were tested after post-synthesis alumination of SBA-15 silica. The catalyst with a Si/Al ratio of 20 achieved 96% biodiesel yield using only 10% catalyst at 200°C over 4 hours and showed good stability and recyclability. The catalysts were able to simultaneously catalyze transesterification of triglycerides and esterification of free fatty acids, even with 9% free fatty acids present.
This document provides a short review of chemical modification of the marine polysaccharide alginate via free-radical graft copolymerization. It discusses how alginate can be readily modified chemically due to the presence of functional groups on its molecular chains. Graft copolymerization, particularly the "grafting from" method of generating free radicals using thermal initiators or redox systems, is an often used technique for attaching synthetic polymers to alginate's backbone. The review compiles studies on this chemical modification of alginate and the potential applications of the resulting graft copolymers.
Understanding the adsorption mechanisms in nanostructured polymer films has become crucial for their use in technological applications, since film properties vary considerably with the experimental conditions utilized for film fabrication. In this paper, we employ small-angle X-ray
scattering (SAXS) to investigate solutions of polyanilines and correlate the chain conformations with morphological features of the nanostructured films obtained with atomic force microscopy (AFM). It is shown that aggregates formed already in solution affect the film morphology; in
particular, at early stages of adsorption film morphology appears entirely governed by the chain conformation in solution and adsorption of aggregates. We also use SAXS data for modeling poly(o-ethoxyaniline) (POEA) particle shape through an ab initio procedure based on simulated
annealing using the dummy atom model (DAM), which is then compared to the morphological features of POEA films fabricated with distinct pHs and doping acids. Interestingly, when the derivative POEA is doped with p-toluene sulfonic acid (TSA), the resulting films exhibit a fibrillar morphology—seen with atomic force microscopy and transmission electron microscopy—that is consistent with the cylindrical shape inferred from the SAXS data. This is in contrast with the globular morphology observed for POEA films doped with other acids.
This document summarizes a study on the behavior of alkali-activated fly ash-based geopolymer concrete when subjected to thermal activation. Samples of geopolymer concrete cubes were thermally activated at 200°C, 400°C, and 650°C. Fourier transform infrared spectroscopy revealed that most molecular water was removed at 200°C, while crystalline -OH remained even at 650°C. X-ray diffraction showed the samples retained their mineralogical composition up to 650°C. Despite thermal activation up to 650°C, the geopolymer concrete maintained good compressive strength. The intrinsic chemistry of the geopolymer binder allows it to withstand high temperatures without losing structural integrity.
Crystal Engineering Applied to the Development of Novel Pharmaceutical Solid Forms with Improved Bioavailability: the Co Crystals Case by Javier Ellena in Advancements in Bioequivalence & Bioavailability
Pharmaceutical co crystal technology has emerged as a promising strategy to enhance bioavailability of poorly water soluble drugs. This mini review presents a brief overview of pharmaceutical co crystals with particular focus on co crystal design, characterization techniques and impacts on drug bioavailability.
https://crimsonpublishers.com/abb/fulltext/ABB.000514.php
BIOCEMENTATION FOR SAND USING WASTE (CONTAIN CALCIUM SOURCE)Aniket Pateriya
This document summarizes a seminar presentation on using bi cementation for sand through microbial induced calcite precipitation. It discusses using waste materials like eggshells and limestone as calcium sources for the MICP reaction. Methods are presented for producing soluble calcium from eggshells and limestone by dissolving them in acid solutions. Factors that influence calcium solubility like particle size and acid concentration are examined. Methods for testing bi cementation on sand samples include measuring permeability reduction and strength increases from precipitated calcite. Results showed eggshell and limestone both increased sand strength and decreased permeability, improving soil properties in an eco-friendly way.
Evaluation of Performance of Geopolymer Concrete in Acid EnvironmentIRJET Journal
This document evaluates the performance of geopolymer concrete and Portland cement concrete in acid environments. Specimens of both concretes were immersed in 2% sulfuric acid and hydrochloric acid solutions for periods of 28, 56, and 112 days. The weight change and compressive strength of the specimens were measured to analyze their resistance to acid attack. The results showed that geopolymer concrete exhibited higher resistance to both acids compared to Portland cement concrete, with lower weight loss and strength reduction when immersed. Geopolymer concrete therefore has potential for use in acid-prone environments where conventional concrete is vulnerable.
Global Journal of Environmental Science and Management (GJESM)
Application of amorphous zirconium (hydr)oxide/MgFe layered double hydroxides composite in fixed-bed column for phosphate removal from water.
The document describes a study that prepared porous alumina ceramics as supports for hydrogen gas separation membranes. Four formulations of alumina, polyvinyl alcohol, and magnesium nitrate were used to create 18 porous alumina supports. The supports were characterized by measuring their fired weight, soaked weight, suspended weight, porosity, water absorption, and bulk density. An analysis of variance test was used to determine if properties differed significantly between formulations.
This document summarizes a study evaluating amendments to improve the effectiveness of biowalls used for groundwater remediation at sites with high sulfate concentrations. The biowall at Altus Air Force Base in Oklahoma was experiencing reduced performance due to sulfide toxicity. Laboratory tests evaluated different iron sources that could be combined with emulsified vegetable oil amendments to precipitate sulfide and buffer toxicity. Field tests at a pilot biowall compared vegetable oil alone to vegetable oil combined with ferrous lactate and nano hematite. Preliminary results are being analyzed to assess enhancement of reductive dechlorination from the iron additives and determine if they should be included in biowall rejuvenation at high-sulfate sites.
Increment of carbohydrate concentration of Chlorella minutissima microalgae f...IJERA Editor
Microalgae, like any other microorganism react to changes in the external environment with changes in their
intracellular environment. Thus, the manipulation of cultivation conditions, especially the presence or absence
of certain nutrients, stimulates the biosynthesis of compounds of interest. Their carbohydrates can be used to
produce bioethanol. The objective of this study was to evaluate the effect of the medium and the concentrations
of nitrogen and phosphate components used in the culture medium of the microalgae Chlorella minutissima in
the carbohydrate concentration of the same. Box-Behnken Planning was used, totaling 15 trials. The cultivations
were carried out until early stationary phase of growth of the microalgae in closed 2 L reactors. At the end of the
cultivation, the carbohydrate concentrations of dry biomass (%) and yield in carbohydrates (g.L-1
.d-1
) were
determined. According to the analysis of effects, the microalgae Chlorella minutissima cultivated in Basal
medium, with the addition of 0.125 gL-1
of the nitrogenized component (KNO3) and without addition of
phosphatized components (K2HPO4 and KH2PO4) had a higher yield in carbohydrates in the cultivation (0,030 ±
0.002 g.L-1
.d-1
).
Production and Utilization of Retarder from Hardwood Sawdustijtsrd
In this study, production of retarding admixture ASTM C494 Type B from hardwood sawdust and utilization on concrete by using various dosage of admixture was studied. In production of retarder as a local product lignosulphonates based retarding admixture was produced to investigate differences of test results by using admixtures. In this project, selected raw material was Pyin Ka do sawdust and sodium sulphite Na2SO3 was used as a cooking aid chemical liquor by heating at 110°C based on pulp and paper sulphite process. The mechanisms of action of lignosulphonate admixture in cement water systems are prescribed by five different types interaction between retarder and cement grains i Reduction in surface tension of water ii Adsorption iii Electrical repulsion iv Dispersion and v Deflocculation. These reactions cause delaying in setting time.In utilization of retarder on concrete, setting time of hydraulic cement paste, compressive strength of mortar and concrete were considered by using produced admixture dosage of 0.5 , 1 , 1.5 by weight of cement. The setting time testing of cement paste was made by using vicat needle penetration test, and compressive strength was tested with standard cubes. The test results of produced admixture were compared with ASTM C494 1993 . Compressive strength of mortar was tested with 3 inches cube and that of concrete was tested by 6 inches standard cube. For comparison of cost and results of produced admixture, commercial admixture 0.5 by weight of cement was tested. Nay Myo Kyaw Thu | Swe Swe Khaing "Production and Utilization of Retarder from Hardwood Sawdust" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd27911.pdfPaper URL: https://www.ijtsrd.com/engineering/civil-engineering/27911/production-and-utilization-of-retarder-from-hardwood-sawdust/nay-myo-kyaw-thu
This document summarizes a study that used tetrahydrofuran (THF) as a co-solvent to enhance the production of fuel precursors like furfural, hydroxymethylfurfural (HMF), and levulinic acid from maple wood biomass. Key findings include:
1) THF allowed over 90% of lignin to be extracted from maple wood while hydrolyzing it to sugars, achieving higher yields of fuel precursors than water alone.
2) A maximum overall yield of 87% of theoretical fuel precursors from C5 and C6 sugars was achieved using a THF to water ratio of 1:1.
3) Solids remaining after THF treatment were highly digestible
Graphene oxide is used as an efficient and recyclable catalyst for ultrasound-mediated multi-component reactions to synthesize biologically active α-aminophosphonates and 3,4-dihydropyrimidin-2-ones under solvent-free conditions. Reactions using aromatic and aliphatic aldehydes, amines, and diethyl phosphite or urea provide the products in excellent yields within short reaction times. Optimization studies found the best results using 10 mg of graphene oxide under ultrasonic irradiation for 5 minutes, with yields over 96%. The graphene oxide catalyst can be reused for multiple cycles without significant loss of activity.
Lipase catalyzed process for biodiesel production protein engineering and lip...Melike Şeyma Kadayıfçı
This review document discusses the use of lipases in biodiesel production. It covers lipase engineering approaches like directed evolution and rational design to improve properties such as thermostability and activity. It also discusses lipase production methods like host strain selection and metabolic engineering. The goal is to develop high-performance lipases through these techniques to enable large-scale commercialization of lipase-catalyzed biodiesel production as an alternative to fossil fuels.
2009 Alburquerque et al al composting and humficationGermán Tortosa
The document evaluates the composting of "alperujo", a wet solid byproduct of the Spanish olive oil industry, using different bulking agents and aeration strategies. It finds that composting performance was most influenced by the type of bulking agent added and number of turnings. Cotton waste and fresh cow bedding performed best as bulking agents, improving organic matter degradation and leading to quality compost. Forced ventilation alone was insufficient. The resulting composts had good nutrient content and stability, with low heavy metals, demonstrating that composting can treat "alperujo" and produce safe, beneficial organic amendments.
1) CHEMAF's cobalt plant in the Democratic Republic of Congo was experiencing decreased cobalt carbonate grade and increased reagent consumption due to rising magnesium levels in the ore feed, as dolomite concentration increased.
2) Laboratory tests evaluated different precipitation pH levels and precipitants to improve cobalt grade and reduce costs. Dual precipitation using sodium carbonate and sodium hydroxide improved filtration capacity by 30% and cobalt grade and drying capacity by 50%, while reducing reagent use by 22%.
3) Implementing precipitate seed recycle in the plant further increased magnesium rejection by 40%, cobalt grade from 20% to 25%, and reduced reagent consumption. Process changes successfully overcame challenges from high magnesium in
Phytosiderophores are organic compounds secreted by plants like grasses to chelate and absorb iron from the soil. They have a structure of two α-aminocarboxylate binding centers and a single α-hydroxycarboxylate unit which gives them a high selectivity for iron. Iron deficiency is common in calcareous soils due to the low solubility of iron compounds. Phytosiderophores help solubilize iron and transport it to the plant roots and tissues through nicotianamine. They are composed of mugineic acid family compounds and are synthesized from S-adenosyl methionine through nicotianamine. Phytosiderophores also help plants withstand heavy metal stress by
This document discusses a density functional theory study of the epimerization of glucose to mannose catalyzed by Sn-beta zeolite and borate salts. The study finds that the tetrahedral borate ion forms a complex with glucose that inhibits competitive isomerization. The stannanol group of Sn-beta catalyzes glucose ring opening, followed by enolization catalyzed by the silanol group. Epimerization then proceeds via an intramolecular 1,2 carbon shift, which is the rate-limiting step. Tin is found to be the most active metal center, and the proximity of the silanol group to the stannanol group enhances catalytic activity. The study aims to understand the cooperative roles of
Microemulsion – A Potential Carrier for Improved BioavailabilityBRNSS Publication Hub
This document summarizes microemulsions and their potential as drug delivery systems to improve oral bioavailability. Key points:
- Microemulsions are thermodynamically stable mixtures of oil, water, and surfactant that can solubilize poorly water-soluble drugs. Their small droplet size (<100 nm) allows improved drug absorption.
- Around 40% of new drug candidates have poor water solubility, resulting in low bioavailability. Microemulsions may help overcome this issue by enhancing solubility and permeability.
- Factors like surfactant concentration, oil/surfactant properties, and temperature can affect microemulsion phase behavior and transition between oil-in-water
Aluminum doped sba 15 silica as acid catalyst for the methanolysis of sunflow...Solange Quintella
The document summarizes research on using aluminum-doped SBA-15 silica materials as solid acid catalysts for the methanolysis (biodiesel production) of sunflower oil. Different Si/Al molar ratios were tested after post-synthesis alumination of SBA-15 silica. The catalyst with a Si/Al ratio of 20 achieved 96% biodiesel yield using only 10% catalyst at 200°C over 4 hours and showed good stability and recyclability. The catalysts were able to simultaneously catalyze transesterification of triglycerides and esterification of free fatty acids, even with 9% free fatty acids present.
This document provides a short review of chemical modification of the marine polysaccharide alginate via free-radical graft copolymerization. It discusses how alginate can be readily modified chemically due to the presence of functional groups on its molecular chains. Graft copolymerization, particularly the "grafting from" method of generating free radicals using thermal initiators or redox systems, is an often used technique for attaching synthetic polymers to alginate's backbone. The review compiles studies on this chemical modification of alginate and the potential applications of the resulting graft copolymers.
Understanding the adsorption mechanisms in nanostructured polymer films has become crucial for their use in technological applications, since film properties vary considerably with the experimental conditions utilized for film fabrication. In this paper, we employ small-angle X-ray
scattering (SAXS) to investigate solutions of polyanilines and correlate the chain conformations with morphological features of the nanostructured films obtained with atomic force microscopy (AFM). It is shown that aggregates formed already in solution affect the film morphology; in
particular, at early stages of adsorption film morphology appears entirely governed by the chain conformation in solution and adsorption of aggregates. We also use SAXS data for modeling poly(o-ethoxyaniline) (POEA) particle shape through an ab initio procedure based on simulated
annealing using the dummy atom model (DAM), which is then compared to the morphological features of POEA films fabricated with distinct pHs and doping acids. Interestingly, when the derivative POEA is doped with p-toluene sulfonic acid (TSA), the resulting films exhibit a fibrillar morphology—seen with atomic force microscopy and transmission electron microscopy—that is consistent with the cylindrical shape inferred from the SAXS data. This is in contrast with the globular morphology observed for POEA films doped with other acids.
This document summarizes a study on the behavior of alkali-activated fly ash-based geopolymer concrete when subjected to thermal activation. Samples of geopolymer concrete cubes were thermally activated at 200°C, 400°C, and 650°C. Fourier transform infrared spectroscopy revealed that most molecular water was removed at 200°C, while crystalline -OH remained even at 650°C. X-ray diffraction showed the samples retained their mineralogical composition up to 650°C. Despite thermal activation up to 650°C, the geopolymer concrete maintained good compressive strength. The intrinsic chemistry of the geopolymer binder allows it to withstand high temperatures without losing structural integrity.
Crystal Engineering Applied to the Development of Novel Pharmaceutical Solid Forms with Improved Bioavailability: the Co Crystals Case by Javier Ellena in Advancements in Bioequivalence & Bioavailability
Pharmaceutical co crystal technology has emerged as a promising strategy to enhance bioavailability of poorly water soluble drugs. This mini review presents a brief overview of pharmaceutical co crystals with particular focus on co crystal design, characterization techniques and impacts on drug bioavailability.
https://crimsonpublishers.com/abb/fulltext/ABB.000514.php
BIOCEMENTATION FOR SAND USING WASTE (CONTAIN CALCIUM SOURCE)Aniket Pateriya
This document summarizes a seminar presentation on using bi cementation for sand through microbial induced calcite precipitation. It discusses using waste materials like eggshells and limestone as calcium sources for the MICP reaction. Methods are presented for producing soluble calcium from eggshells and limestone by dissolving them in acid solutions. Factors that influence calcium solubility like particle size and acid concentration are examined. Methods for testing bi cementation on sand samples include measuring permeability reduction and strength increases from precipitated calcite. Results showed eggshell and limestone both increased sand strength and decreased permeability, improving soil properties in an eco-friendly way.
Evaluation of Performance of Geopolymer Concrete in Acid EnvironmentIRJET Journal
This document evaluates the performance of geopolymer concrete and Portland cement concrete in acid environments. Specimens of both concretes were immersed in 2% sulfuric acid and hydrochloric acid solutions for periods of 28, 56, and 112 days. The weight change and compressive strength of the specimens were measured to analyze their resistance to acid attack. The results showed that geopolymer concrete exhibited higher resistance to both acids compared to Portland cement concrete, with lower weight loss and strength reduction when immersed. Geopolymer concrete therefore has potential for use in acid-prone environments where conventional concrete is vulnerable.
Global Journal of Environmental Science and Management (GJESM)
Application of amorphous zirconium (hydr)oxide/MgFe layered double hydroxides composite in fixed-bed column for phosphate removal from water.
The document describes a study that prepared porous alumina ceramics as supports for hydrogen gas separation membranes. Four formulations of alumina, polyvinyl alcohol, and magnesium nitrate were used to create 18 porous alumina supports. The supports were characterized by measuring their fired weight, soaked weight, suspended weight, porosity, water absorption, and bulk density. An analysis of variance test was used to determine if properties differed significantly between formulations.
This document summarizes a study evaluating amendments to improve the effectiveness of biowalls used for groundwater remediation at sites with high sulfate concentrations. The biowall at Altus Air Force Base in Oklahoma was experiencing reduced performance due to sulfide toxicity. Laboratory tests evaluated different iron sources that could be combined with emulsified vegetable oil amendments to precipitate sulfide and buffer toxicity. Field tests at a pilot biowall compared vegetable oil alone to vegetable oil combined with ferrous lactate and nano hematite. Preliminary results are being analyzed to assess enhancement of reductive dechlorination from the iron additives and determine if they should be included in biowall rejuvenation at high-sulfate sites.
Increment of carbohydrate concentration of Chlorella minutissima microalgae f...IJERA Editor
Microalgae, like any other microorganism react to changes in the external environment with changes in their
intracellular environment. Thus, the manipulation of cultivation conditions, especially the presence or absence
of certain nutrients, stimulates the biosynthesis of compounds of interest. Their carbohydrates can be used to
produce bioethanol. The objective of this study was to evaluate the effect of the medium and the concentrations
of nitrogen and phosphate components used in the culture medium of the microalgae Chlorella minutissima in
the carbohydrate concentration of the same. Box-Behnken Planning was used, totaling 15 trials. The cultivations
were carried out until early stationary phase of growth of the microalgae in closed 2 L reactors. At the end of the
cultivation, the carbohydrate concentrations of dry biomass (%) and yield in carbohydrates (g.L-1
.d-1
) were
determined. According to the analysis of effects, the microalgae Chlorella minutissima cultivated in Basal
medium, with the addition of 0.125 gL-1
of the nitrogenized component (KNO3) and without addition of
phosphatized components (K2HPO4 and KH2PO4) had a higher yield in carbohydrates in the cultivation (0,030 ±
0.002 g.L-1
.d-1
).
Production and Utilization of Retarder from Hardwood Sawdustijtsrd
In this study, production of retarding admixture ASTM C494 Type B from hardwood sawdust and utilization on concrete by using various dosage of admixture was studied. In production of retarder as a local product lignosulphonates based retarding admixture was produced to investigate differences of test results by using admixtures. In this project, selected raw material was Pyin Ka do sawdust and sodium sulphite Na2SO3 was used as a cooking aid chemical liquor by heating at 110°C based on pulp and paper sulphite process. The mechanisms of action of lignosulphonate admixture in cement water systems are prescribed by five different types interaction between retarder and cement grains i Reduction in surface tension of water ii Adsorption iii Electrical repulsion iv Dispersion and v Deflocculation. These reactions cause delaying in setting time.In utilization of retarder on concrete, setting time of hydraulic cement paste, compressive strength of mortar and concrete were considered by using produced admixture dosage of 0.5 , 1 , 1.5 by weight of cement. The setting time testing of cement paste was made by using vicat needle penetration test, and compressive strength was tested with standard cubes. The test results of produced admixture were compared with ASTM C494 1993 . Compressive strength of mortar was tested with 3 inches cube and that of concrete was tested by 6 inches standard cube. For comparison of cost and results of produced admixture, commercial admixture 0.5 by weight of cement was tested. Nay Myo Kyaw Thu | Swe Swe Khaing "Production and Utilization of Retarder from Hardwood Sawdust" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd27911.pdfPaper URL: https://www.ijtsrd.com/engineering/civil-engineering/27911/production-and-utilization-of-retarder-from-hardwood-sawdust/nay-myo-kyaw-thu
This document summarizes a study that used tetrahydrofuran (THF) as a co-solvent to enhance the production of fuel precursors like furfural, hydroxymethylfurfural (HMF), and levulinic acid from maple wood biomass. Key findings include:
1) THF allowed over 90% of lignin to be extracted from maple wood while hydrolyzing it to sugars, achieving higher yields of fuel precursors than water alone.
2) A maximum overall yield of 87% of theoretical fuel precursors from C5 and C6 sugars was achieved using a THF to water ratio of 1:1.
3) Solids remaining after THF treatment were highly digestible
Graphene oxide is used as an efficient and recyclable catalyst for ultrasound-mediated multi-component reactions to synthesize biologically active α-aminophosphonates and 3,4-dihydropyrimidin-2-ones under solvent-free conditions. Reactions using aromatic and aliphatic aldehydes, amines, and diethyl phosphite or urea provide the products in excellent yields within short reaction times. Optimization studies found the best results using 10 mg of graphene oxide under ultrasonic irradiation for 5 minutes, with yields over 96%. The graphene oxide catalyst can be reused for multiple cycles without significant loss of activity.
Lipase catalyzed process for biodiesel production protein engineering and lip...Melike Şeyma Kadayıfçı
This review document discusses the use of lipases in biodiesel production. It covers lipase engineering approaches like directed evolution and rational design to improve properties such as thermostability and activity. It also discusses lipase production methods like host strain selection and metabolic engineering. The goal is to develop high-performance lipases through these techniques to enable large-scale commercialization of lipase-catalyzed biodiesel production as an alternative to fossil fuels.
This document discusses the use of enzymes in the synthesis of bioactive compounds. It begins by noting the advantages of enzymes as catalysts such as their selectivity and ability to work under mild conditions. However, their narrow substrate specificity and instability have limited their application. Advances in biocatalysis over the last 20 years have helped address these drawbacks through immobilization, use of enzymes in non-aqueous solvents, and directed evolution. The document then discusses various applications of enzymes including in non-aqueous solvents, immobilization, directed evolution to modify substrate specificity and stability, synthesis of carbohydrates and chiral drugs, and their use in combinatorial chemistry.
This document describes research into using encapsulated mixed enzymes from Bacillus subtilis and Burkholderia cepacia to produce biodiesel from waste cooking oil via interesterification. Response surface methodology and a central composite experimental design were used to optimize reaction parameters including enzyme loading, oil to methyl acetate ratio, temperature, and reaction time. The optimal conditions found were 2 g enzyme loading, a 1:12 oil to methyl acetate ratio, 60 hours reaction time, and 35°C temperature, yielding 93.61% biodiesel. Immobilizing the enzymes allowed them to be reused for 20 cycles without loss of activity. Producing biodiesel from waste cooking oil via this enzymatic method provides an ecofriendly and cost
Use of surface modified bentonite clay catalyst for esterification of maleic ...eSAT Journals
Abstract Inorganic clays are being exploited as solid catalysts support for vide verity of organic reactions. Surface modified (SM) clay was synthesized by sulfuric acid treatment of raw bentonite clay. Acid treated clay was characterized by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The esterification of maleic acid with ethanol using SM clay catalyst was carried out to study an effect of various parameters viz. speed of agitation, catalyst loading, mole ratio of reactants and temperature. SM bentonite shows better catalytic activity towards maleic acid-ethanol esterification. A Pseudo-homogeneous kinetic model was used to validate the experimental data. Kinetic parameter such as rate constant and activation energy was estimated for the reaction. Keywords: Esterification, maleic acid, SM bentonite, rate constant, activation energy.
This thesis focuses on the catalytic production of diesel from biomass, emphasizing the conversion of waste vegetable oils and fats. Two established methods are transesterification/esterification of oils and fats with methanol to produce fatty acid methyl esters (FAME), and hydrodeoxygenation of oils and fats to produce straight-chain alkanes. Other potential routes include upgrading and deoxygenation of pyrolysis oils or sludge, aqueous reforming of sugars, and Fischer-Tropsch synthesis of alkanes from gasified biomass. The thesis tests various acidic catalysts for esterification in a model fat mixture and develops a sulphonated pyrolysed sucrose catalyst. Organic bases
This document summarizes research on alternative fuels for diesel engines. It discusses various alternative fuels used in diesel engines worldwide, including alcohols, bioethanol, biogas, biodiesel from vegetable oils, and hydrogen. Biodiesel from rapeseed oil methyl esters is most commonly used in Europe and Poland due to climate and agriculture. While biodiesel has benefits like being renewable and having similar properties to diesel, it also has some drawbacks like potential damage to engine components from high viscosity. The document compares properties of diesel, rapeseed oil, and rapeseed oil methyl ester biodiesel. It also discusses effects of biodiesel on engine emissions and potential issues like filter blocking.
Catalytic cracking of polypropylene waste over zeolite betaAlexander Decker
This document summarizes a study that investigated the catalytic cracking of polypropylene (PP) waste using zeolite beta (BEA) catalysts. BEA catalysts with different Si/Al ratios were synthesized from mesoporous silica and tested for their ability to crack PP waste at various temperatures. The BEA catalyst with Si/Al ratio of 12.5 showed 95% conversion of PP waste at 400°C. Catalytic cracking led to higher conversions and more valuable products compared to thermal cracking. The used BEA catalyst could be regenerated with similar activity to the fresh catalyst.
This document provides an overview of biodiesel production methods and their impact on emissions. It discusses the advantages of heterogeneous catalysts over homogeneous catalysts for biodiesel production. The document then reviews several studies on biodiesel production from waste cooking oil using transesterification with various catalysts and production methods. Key findings from these studies include higher biodiesel yields from transesterification at 60°C and reductions in emissions like CO and smoke when using biodiesel blends compared to diesel fuel. The document concludes by stating that biodiesel production from waste oils helps address issues of decreasing oil reserves, environmental pollution, and high fuel prices.
KINETICS OF ESTERIFICATION REACTION USING ION-EXCHANGE RESIN CATALYSTJournal For Research
This document summarizes a study on the kinetics of the esterification reaction between n-butanol and acetic acid using an ion-exchange resin catalyst. The research was conducted in a batch reactor at temperatures of 353-356K, varying catalyst loads and reactant ratios. The activation energy for the reaction was determined to be 622.28 kJ/mol. Kinetic parameters were estimated by fitting the experimental data to reaction mechanisms. The results showed good agreement between the modeled and experimental results, validating the reaction mechanism.
The document discusses aqueous phase reforming of sorbitol to produce value-added chemicals. It describes background studies on sorbitol and its potential for hydrogen production. The objectives are to identify value-added chemicals produced from reforming sorbitol over a Ni/Al2O3 catalyst promoted with Ca, and to synthesize and characterize the catalyst. The methodology involves preparing the catalyst using incipient wetness impregnation, characterizing it using TGA, SEM, and H2-TPR, and evaluating its performance in reforming sorbitol to identify products.
SiO2 beads decorated with SrO nanoparticles for biodiesel production finalAlex Tangy
This document summarizes a study on the development of a heterogeneous solid base catalyst comprising strontium oxide deposited on silica beads (SrO@SiO2) for the conversion of waste cooking oil to biodiesel under microwave irradiation. The catalyst was synthesized by depositing strontium carbonate nanoparticles on silica beads via a microwave irradiation method. The catalyst preparation was optimized with respect to irradiation time, calcination time and temperature, and the ratio of strontium precursor to silica beads. Characterization techniques confirmed the deposition of strontium oxide nanoparticles on the silica beads. Testing showed the SrO@SiO2 catalyst achieved waste cooking oil conversions as high as 99.4% in just 10 seconds of
This document discusses using high ionicity ionic liquids (HIILs) based on 1-ethyl-3-methylimidazolium ethyl sulphate for separating ethanol from n-heptane mixtures. Three HIILs were prepared with different amounts of ammonium thiocyanate added to increase ionicity. Liquid-liquid equilibria experiments were conducted on ternary mixtures of n-heptane, ethanol, and each HIIL. The HIILs were able to break the azeotrope and their selectivity and distribution coefficients were correlated to ionicity. Compared to the neat ionic liquid, the HIILs showed improved extraction performance due to their higher ion
This presentation summarizes the role of pretreatment processes in enhancing anaerobic digestion of municipal solid waste. Various pretreatment methods including mechanical, thermal, chemical and combinations are discussed. A case study on microbial pretreatment of lignocellulosic waste showed improved biogas and methane production. Pretreatments can increase biodegradability, biogas yields, degradation rates and reduce retention times compared to untreated processes. Thermal pretreatments at low temperatures are often most cost-effective.
The document summarizes research on aromatic carboxylic acids and their conversion to amides. It describes various methods for synthesizing amides, including the reaction of carboxylic acids with isocyanates. The document reports on a study investigating this amidation reaction using ionic liquids (ILs) as solvents. It finds that ILs provide higher yields of amides than traditional solvents, without side products. The properties and reactions of aromatic carboxylic acids are also discussed.
Hexamolybdenum clusters supported on graphene oxide: Visible-light induced ph...Pawan Kumar
Hexamolybdenum (Mo6) cluster-based compounds namely Cs2Mo6Bri
8Bra6
and
(TBA)2Mo6Bri
8Bra
6 (TBA = tetrabutylammonium) were immobilized on graphene oxide (GO)
nanosheets by taking advantage of the high lability of the apical bromide ions with
oxygen-functionalities of GO nanosheets. The loading of Mo6 clusters on GO nanosheets
was probed by Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron
spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM) and elemental
mapping analyses. The developed GO-Cs2Mo6Bri
8Bra
x and GO-(TBA)2Mo6Bri
8Bra
x
composites were then used as heterogeneous photocatalysts for the reduction of CO2 under
visible light irradiation. After 24 h visible light illumination, the yield of methanol was
found to be 1644 and 1294 lmol g1 cat for GO-Cs2Mo6Bri
8Bra
x and GO-(TBA)2Mo6Bri
8Bra
x,
respectively. The quantum yields of methanol by using GO-Cs2Mo6Bri
8Bra
x and
GO-(TBA)2Mo6Bri
8Bra
x as catalysts with reference to Mo6 cluster units presented in 0.1 g
amount of catalyst were found to be 0.015 and 0.011, respectively. The role of immobilized
Mo6 clusters-based compounds on GO nanosheets is discussed to understand the
photocatalytic mechanism of CO2 reduction into methanol.
Hexamolybdenum clusters supported on graphene oxide: Visible-light induced ph...Pawan Kumar
This document summarizes a study on immobilizing hexamolybdenum clusters on graphene oxide nanosheets for photocatalytic reduction of carbon dioxide into methanol. Specifically, Cs2Mo6Bri8Bra6 and (TBA)2Mo6Bri8Bra6 clusters were immobilized on graphene oxide through replacement of apical bromide ions with oxygen functional groups on the graphene oxide surface. The developed GO-Cs2Mo6Bri8Brax and GO-(TBA)2Mo6Bri8Brax composites were then used as heterogeneous photocatalysts for CO2 reduction under visible light, producing methanol yields of 1644 and 1294 μmol g−1cat, respectively
This document reviews recent advances in hydrodeoxygenation (HDO) processes for converting biomass-derived platform chemicals into hydrocarbon fuels. It discusses strategies for removing oxygen from highly oxygenated biomass compounds through dehydration, hydrogenation, hydrogenolysis and other reactions. It also covers increasing the carbon chain length of products through C-C coupling reactions. The key role of HDO catalyst design is emphasized to effectively transform biomass molecules into fuels with reduced oxygen and improved hydrogen-to-carbon ratios. Recent developments in HDO catalysts for the upgrading of compounds like 5-hydroxymethylfurfural are also summarized.
Selective Dehydration of Lactic Acid to Acrylic Acid in the Gas Phase by Jona...Brown Fellows Program
This document summarizes research into selectively dehydrating lactic acid into acrylic acid using modified zeolite Na-Y catalysts. Lactic acid is a renewable feedstock that can be converted into acrylic acid, an important plastic precursor typically derived from petroleum. Previous work achieved 72.3% selectivity using modified Na-Y zeolites. The current work prepares zeolite catalysts through wet impregnation and tests them in a fixed-bed reactor with integrated evaporator to selectively dehydrate vapor-phase lactic acid. The goal is to better understand how different cation modifications impact the catalyst's acidic and basic properties and ability to selectively produce acrylic acid from lactic acid. Improved catalysts could
This document presents a kinetic model for the lipase-catalyzed conversion of ascorbic acid and oleic acid to the liposoluble vitamin C ester ascorbyl oleate. Experimental data were fitted to a ping-pong bi-bi kinetic model with substrate inhibition by excess ascorbic acid. Kinetic constants were determined under optimized reaction conditions. The model was then expanded to include terms describing ester hydrolysis, and kinetic constants for the reverse reaction were estimated. The calculated constants revealed that lipase has the highest affinity for ascorbyl oleate and slightly lower activity for ascorbic acid, with the lowest activity for oleic acid.
International Conference on NLP, Artificial Intelligence, Machine Learning an...gerogepatton
International Conference on NLP, Artificial Intelligence, Machine Learning and Applications (NLAIM 2024) offers a premier global platform for exchanging insights and findings in the theory, methodology, and applications of NLP, Artificial Intelligence, Machine Learning, and their applications. The conference seeks substantial contributions across all key domains of NLP, Artificial Intelligence, Machine Learning, and their practical applications, aiming to foster both theoretical advancements and real-world implementations. With a focus on facilitating collaboration between researchers and practitioners from academia and industry, the conference serves as a nexus for sharing the latest developments in the field.
Understanding Inductive Bias in Machine LearningSUTEJAS
This presentation explores the concept of inductive bias in machine learning. It explains how algorithms come with built-in assumptions and preferences that guide the learning process. You'll learn about the different types of inductive bias and how they can impact the performance and generalizability of machine learning models.
The presentation also covers the positive and negative aspects of inductive bias, along with strategies for mitigating potential drawbacks. We'll explore examples of how bias manifests in algorithms like neural networks and decision trees.
By understanding inductive bias, you can gain valuable insights into how machine learning models work and make informed decisions when building and deploying them.
Presentation of IEEE Slovenia CIS (Computational Intelligence Society) Chapte...University of Maribor
Slides from talk presenting:
Aleš Zamuda: Presentation of IEEE Slovenia CIS (Computational Intelligence Society) Chapter and Networking.
Presentation at IcETRAN 2024 session:
"Inter-Society Networking Panel GRSS/MTT-S/CIS
Panel Session: Promoting Connection and Cooperation"
IEEE Slovenia GRSS
IEEE Serbia and Montenegro MTT-S
IEEE Slovenia CIS
11TH INTERNATIONAL CONFERENCE ON ELECTRICAL, ELECTRONIC AND COMPUTING ENGINEERING
3-6 June 2024, Niš, Serbia
A SYSTEMATIC RISK ASSESSMENT APPROACH FOR SECURING THE SMART IRRIGATION SYSTEMSIJNSA Journal
The smart irrigation system represents an innovative approach to optimize water usage in agricultural and landscaping practices. The integration of cutting-edge technologies, including sensors, actuators, and data analysis, empowers this system to provide accurate monitoring and control of irrigation processes by leveraging real-time environmental conditions. The main objective of a smart irrigation system is to optimize water efficiency, minimize expenses, and foster the adoption of sustainable water management methods. This paper conducts a systematic risk assessment by exploring the key components/assets and their functionalities in the smart irrigation system. The crucial role of sensors in gathering data on soil moisture, weather patterns, and plant well-being is emphasized in this system. These sensors enable intelligent decision-making in irrigation scheduling and water distribution, leading to enhanced water efficiency and sustainable water management practices. Actuators enable automated control of irrigation devices, ensuring precise and targeted water delivery to plants. Additionally, the paper addresses the potential threat and vulnerabilities associated with smart irrigation systems. It discusses limitations of the system, such as power constraints and computational capabilities, and calculates the potential security risks. The paper suggests possible risk treatment methods for effective secure system operation. In conclusion, the paper emphasizes the significant benefits of implementing smart irrigation systems, including improved water conservation, increased crop yield, and reduced environmental impact. Additionally, based on the security analysis conducted, the paper recommends the implementation of countermeasures and security approaches to address vulnerabilities and ensure the integrity and reliability of the system. By incorporating these measures, smart irrigation technology can revolutionize water management practices in agriculture, promoting sustainability, resource efficiency, and safeguarding against potential security threats.
Advanced control scheme of doubly fed induction generator for wind turbine us...IJECEIAES
This paper describes a speed control device for generating electrical energy on an electricity network based on the doubly fed induction generator (DFIG) used for wind power conversion systems. At first, a double-fed induction generator model was constructed. A control law is formulated to govern the flow of energy between the stator of a DFIG and the energy network using three types of controllers: proportional integral (PI), sliding mode controller (SMC) and second order sliding mode controller (SOSMC). Their different results in terms of power reference tracking, reaction to unexpected speed fluctuations, sensitivity to perturbations, and resilience against machine parameter alterations are compared. MATLAB/Simulink was used to conduct the simulations for the preceding study. Multiple simulations have shown very satisfying results, and the investigations demonstrate the efficacy and power-enhancing capabilities of the suggested control system.
6th International Conference on Machine Learning & Applications (CMLA 2024)ClaraZara1
6th International Conference on Machine Learning & Applications (CMLA 2024) will provide an excellent international forum for sharing knowledge and results in theory, methodology and applications of on Machine Learning & Applications.
DEEP LEARNING FOR SMART GRID INTRUSION DETECTION: A HYBRID CNN-LSTM-BASED MODELgerogepatton
As digital technology becomes more deeply embedded in power systems, protecting the communication
networks of Smart Grids (SG) has emerged as a critical concern. Distributed Network Protocol 3 (DNP3)
represents a multi-tiered application layer protocol extensively utilized in Supervisory Control and Data
Acquisition (SCADA)-based smart grids to facilitate real-time data gathering and control functionalities.
Robust Intrusion Detection Systems (IDS) are necessary for early threat detection and mitigation because
of the interconnection of these networks, which makes them vulnerable to a variety of cyberattacks. To
solve this issue, this paper develops a hybrid Deep Learning (DL) model specifically designed for intrusion
detection in smart grids. The proposed approach is a combination of the Convolutional Neural Network
(CNN) and the Long-Short-Term Memory algorithms (LSTM). We employed a recent intrusion detection
dataset (DNP3), which focuses on unauthorized commands and Denial of Service (DoS) cyberattacks, to
train and test our model. The results of our experiments show that our CNN-LSTM method is much better
at finding smart grid intrusions than other deep learning algorithms used for classification. In addition,
our proposed approach improves accuracy, precision, recall, and F1 score, achieving a high detection
accuracy rate of 99.50%.
DEEP LEARNING FOR SMART GRID INTRUSION DETECTION: A HYBRID CNN-LSTM-BASED MODEL
Tiempo de contacto
1. Use of HZSM-5 modified with citric acid as acid heterogeneous catalyst
for biodiesel production via esterification of oleic acid
Sara S. Vieira a
, Zuy M. Magriotis a,⇑
, Maria Filipa Ribeiro b
, Inês Graça b
, Auguste Fernandes b
,
José Manuel F.M. Lopes b
, Sabrina M. Coelho a
, Nadiene Ap.V. Santos a
, Adelir Ap. Saczk a
a
Departamento de Química, Universidade Federal de Lavras, 37.200-000 Lavras, MG, Brazil
b
IBB, Institute for Biotechnology and Bioengineering, Centre for Biological and Chemical Engineering, Instituto Superior Técnico – Universidade de Lisboa, Av. Rovisco Pais,
1049-001 Lisboa, Portugal
a r t i c l e i n f o
Article history:
Received 16 June 2014
Received in revised form 1 September 2014
Accepted 5 September 2014
Available online 16 September 2014
Keywords:
Biodiesel
Esterification
HZSM-5
Dealumination
Citric acid
a b s t r a c t
In this study, the efficiency of citric acid as dealumination agent was evaluated in the case of zeolite
HZSM-5 by varying the experimental conditions, namely concentration (0.5, 1.0 and 2.0 mol LÀ1
) and
treatment temperature (60 and 80 °C). The effect of the CA treatment on structural, textural and acidity
properties of the starting HZSM-5 material was monitored using XRD, N2 sorption and FTIR (pyridine and
collidine) measurements. Heptane and methylcyclohexane cracking model reactions were used to eval-
uate the catalytic behavior of the modified materials, in terms of acid strength and active sites accessi-
bility. The modified catalysts were tested in the esterification reaction, using oleic acid as reagent and
different oleic acid/methanol molar ratios. All the results show the beneficial effect of the citric acid treat-
ment on the physicochemical properties of the final materials, with an improvement of the external acid-
ity, a crucial parameter for the reaction considered, i.e. the oleic acid esterification.
Ó 2014 Elsevier Inc. All rights reserved.
1. Introduction
Increasing concerns related to, mainly, environmental issues
have led to enhanced interest in the search for renewable sources
in the field of transportation fuels production [1,2]. A remarkable
intensified research has been directed, in fact, to biomass derived
fuels, aiming to gradually reduce the dependence from crude oil
and carbon dioxide emissions [3,4]. Additionally, relevant benefits
should result from the absence of sulfur compounds in the biofuel
[5]. In practice, biodiesel increased, in recent years, its market
share through blending with petrodiesel.
Biodiesel is a mixture of long chain fatty acid alkyl esters,
obtained from the transesterification of triglycerides and esterifi-
cation of free fatty acids (FFA) with alcohols [3,6,7], contained in
vegetable oils and other types of fat feedstocks. It is currently pro-
duced using homogeneous mineral, acid or basic (NaOH) catalysts,
presenting these processes interesting reaction rates for triglycer-
ides transesterification and some undesired features: corrosion
problems; expensive process steps of catalyst/products separation;
need to remove FFA and water from the feedstock, in order to pre-
vent catalyst consumption and aqueous quenching [8].
Many efforts have been then carried out in order to develop
more eco-friendly heterogeneous processes effective for biodiesel
production [2,9], either basic or acid solids being potentially inter-
esting recyclable catalysts. Several studies report the attempting
use of rare-earth and other types of oxides [10–16], clays [17]
and zeolites [16,18,19]. Some minimization of the homogeneous
process drawbacks can effectively result by using heterogeneous
base-catalyzed systems: easy separation processes, possibility of
use continuous flow reactors, catalyst recycling, etc. Solid acid cat-
alysts have shown to be more interesting [20], as they combine the
advantages of the solid materials and the mineral acids [21]. They
revealed to be able to simultaneously promote the esterification
and transesterification reactions [21], which is especially interest-
ing for the transformation of oils containing high amounts of FFA,
the feedstock pretreatment becoming unnecessary, thus involving
reduced costs. However, some limitations of the solid acid cata-
lyzed biodiesel production still remain, such as the promotion of
secondary reactions and the observed kinetics.
The specific research concerning the production of biodiesel
from long chain FFA esterification has been also intensified [22].
The oleic acid, present in several vegetable oils, despite being one
of the most common FFA, has been used in few esterification
http://dx.doi.org/10.1016/j.micromeso.2014.09.015
1387-1811/Ó 2014 Elsevier Inc. All rights reserved.
⇑ Corresponding author. Tel.: +55 35 38291889; fax: +55 35 38291812.
E-mail addresses: saraufla@yahoo.com.br (S.S. Vieira), zuy@dqi.ufla.br
(Z.M. Magriotis), filipa.ribeiro@ist.utl.pt (M.F. Ribeiro), ines.sofia.graca@ist.utl.pt
(I. Graça), auguste.fernandes@ist.utl.pt (A. Fernandes), jmlopes@ist.utl.pt
(J.M.F.M. Lopes), sabrina10mcoelho@yahoo.com.br (S.M. Coelho), nadi.ene@
hotmail.com (N.Ap.V. Santos), adelir@dqi.ufla.br (A.Ap. Saczk).
Microporous and Mesoporous Materials 201 (2015) 160–168
Contents lists available at ScienceDirect
Microporous and Mesoporous Materials
journal homepage: www.elsevier.com/locate/micromeso
2. studies [19]. Similarly to other cases [2,21], the conversion of oleic
acid revealed to be efficiently promoted by solid acid catalysts
[19,23]. Several features of these materials should be determinant,
such as high strength and concentration of acid sites and high sur-
face area with hydrophobic character [2,21]. These and other prop-
erties constitute important and well-known characteristics of
zeolites, which are microporous crystalline aluminosilicates widely
used in heterogeneous catalysis [24]. Additionally, the acid/base
properties, the hydrophilic/hydrophobic character, the porous net-
work properties, of zeolites can be finely tuned, so that specific lev-
els of Brønsted/Lewis acid sites strength and concentration,
hydrophobic selective adsorption ability, etc., can be achieved, thus
allowing possible activity and selectivity enhancements towards
esterification reactions [25].
Zeolites ZSM-5 and Mordenite have shown to be interestingly
active in the esterification of oleic acid with methanol [19], with
special emphasis for ZSM-5 [23]. This catalyst presents an internal
pore network with apertures of approximately 5.5 Å, thus prevent-
ing the inner penetration of oleic acid, and also very strong
Brønsted acid sites located in a generally hydrophobic surface.
Several post-synthesis treatments have been widely applied
over zeolites, and specifically over ZSM-5, namely the controlled
dealumination [25–27], searching for more efficient catalysts.
The typical Brønsted acidity present in zeolites arises from the
hydroxyl (Si–(OH)–Al) groups bridging two adjacent tetrahedra,
SiO4 and AlO4
À
, of its aluminosilicate framework. The concentration
of these sites, as well as, in many cases, their acid strength, would
be directly related to the aluminum content of the structure. The
removal of framework aluminum by dealumination treatments,
which may be performed by steaming or acid leaching, for exam-
ple, will then change the amount (and eventually the strength) of
Brønsted acid sites, and possibly create some Lewis sites. Simulta-
neously, some mesoporosity is usually generated, promoting in
this way an enhancement of the remaining acid sites accessibility,
which will be of particular relevance when testing large molecules
transformation over ZSM-5 zeolite. The hydrophobic character of
the zeolite surface will be also modified, by controlling the nega-
tive charge in the structure associated with framework Al species
[28].
Inorganic strong acids, such as HCl or HNO3, are generally used
in zeolites Al leaching. However, depending on the severity of the
treatment and the characteristics of the zeolite, serious damage of
the zeolite structure may occur. The use of citric acid as dealumi-
nation agent seems to be of special interest in order to produce
the mentioned modifications in the more relevant external layer
of the catalyst particles, since the transformation of the oleic acid
promoted by ZSM-5 will proceed over the external surface of the
zeolite crystal. In fact, due to the large dimensions of this acid mol-
ecule, it was reported that even over a larger pore USY zeolite, the
dealumination took place gradually from the outer to inner sites of
the crystallite. The preferential mesopore generation at the exter-
nal surface of the solid particle has been pointed out as a positive
factor [29].
The main goal of the present study is to produce interesting
modifications on a HZSM-5 zeolite by citric acid (CA) treatment,
so that its catalytic properties towards the oleic acid esterification
with methanol, a model reaction that is used to simulate the bio-
diesel production, could be improved. A detailed characterization
of the parent and treated zeolite samples was pursued, in order
to monitor the induced modifications, namely, in the nature, num-
ber and strength of the acid sites, as well as in their accessibility,
trying then to correlate it with the catalytic changes. The Brønsted
acidity was characterized by infrared spectroscopy (FTIR) of the OH
stretching groups; the total (and external) acidity was character-
ized by pyridine (and collidine) adsorption followed by FTIR; the
textural properties were evaluated from nitrogen sorption studies.
Additionally, the HZSM-5 samples have been tested in the model
reactions of heptane and methylcyclohexane cracking, searching
for monitoring, in reaction conditions, also the acidity of the sam-
ples and the sites accessibility. In fact, heptane transformation
demands higher strength of the acid sites than methylcyclohexane,
since the corresponding intermediary carbenium ions involved in
the cracking mechanism are less stable in the former case [30].
On the other side, heptane can penetrate much more easily inside
the HZSM-5 porous network than methylcyclohexane, which is a
bulky molecule.
2. Experimental
2.1. Preparation of catalysts
Zeolite HZSM-5 (MFI structure) used in this work as parent
sample was supplied by Zeochem (reference n° V1148.4) with a
Si/Al ratio of 14. It was then modified using citric acid (CA). The
effect of both treatment temperature (60 and 80 °C) and CA con-
centration (0.5; 1.0 e 2.0 mol LÀ1
) was evaluated. Typically, a sus-
pension of zeolite sample into an aqueous solution containing CA
(with the appropriate concentration) was prepared and the mix-
ture was then heated under stirring for 3 h [31]. Afterwards, the
final product was recovered by filtration, washed several times
with distillated water and finally dried in an oven at 100 °C for
24 h. The resulting solid was calcined at 500 °C in a quartz reactor
for 4 h (heating rate of 10 °C minÀ1
), under synthetic air flow
(100 mL minÀ1
). Hereafter, the samples will be referred to as HZ/
X/Y where X and Y stand for, respectively, CA concentration and
treatment temperature.
2.2. Characterization of catalysts
The chemical composition of the different materials, i.e. the Si/
Al molar ratio, was determined by XRF analysis performed on a
Spectrometer X-ray Philips PW1480 (Rh Tube Anode), using a cal-
ibration curve obtained from different zeolite references (different
Si/Al ratios).
The structural characterization of the parent and modified HZ
samples was carried out by Powder X-ray diffraction using a D8
Advance diffractometer from Bruker, equipped with a graphite
monochromator using Cu-Ka radiation (1.5406 Å) as incident
beam and operating at 40 kV and 40 mA. The diffraction patterns
were obtained from 5° to 65° (2h), with a step size of 0.05 and a
time per step of 3 s.
Textural characterization of the solids was carried out by means
of N2 sorption measurements isotherms at À196 °C, performed in
an automatic apparatus Micromeritics ASAP 2010, where the sam-
ples were outgassed at 350 °C during 4 h under vacuum before N2
sorption measurements. The micropores volume (Vmicro) and exter-
nal surface (Sext) area were determined using t-plot method. Total
pores volume (Vpore) was determined at pressure P/P0 of 0.97
(adsorption branch).
The samples acidity was characterized by pyridine and collidine
(basic probe molecules) adsorption followed by IR spectroscopy,
using a Nicolet Nexus spectrometer. The samples were pressed into
thin wafers (10–20 mg cmÀ2
) and pre-treated in an IR quartz cell at
450 °C for 3 h under secondary vacuum (10À6
mbar). The samples
were then cooled down to 150 °C and contacted with the probe
molecule. After that, the excess of probe molecule was evacuated
for 30 min under secondary vacuum and then IR spectra were
recorded (64 scans with a resolution of 4 cmÀ1
). The background
spectrum, always recorded under identical conditions without
sample and performed before each spectrum acquisition, was auto-
matically subtracted. In what concerns pyridine experiment, the
S.S. Vieira et al. / Microporous and Mesoporous Materials 201 (2015) 160–168 161
3. samples were subsequently heated at 250, 350 and 450 °C under
vacuum (30 min for each temperature) and the respective spectra
acquired.
For quantification purposes, the spectrum of the sample after
pretreatment was subtracted from the spectra obtained after the
probe molecule adsorption and subsequent desorption. Brønsted
and Lewis acid sites concentrations were determined from
pyridine adsorption, using areas of bands at 1545 and 1450 cmÀ1
,
respectively. Molar absorptivity used were 1.13 and
1.28 cm lmolÀ1
for pyridine interacting with Brønsted and Lewis
centers, respectively [32]. Total external acidity was evaluated
using collidine as probe molecule. Quantification was carried out
using the integrated area in the region 1600–1700 cmÀ1
; molar
absorptivity used was 10.1 cm lmolÀ1
[33].
2.3. Heptane and methylcyclohexane catalytic tests
HZSM-5 samples obtained through citric acid dealumination
were also characterized in what concerns their acidity and accessi-
bility by performing two model hydrocarbon transformations, the
heptane transformation, a linear alkane whose transformation is
extremely dependent on the acidity strength, and the methylcyclo-
hexane transformation, a bulky molecule for which diffusion into
the HZSM-5 porous network is limited [34,35].
Before the reaction, all catalysts were pre-treated at 450 °C
under nitrogen flow (60 mL minÀ1
) for 8 h. The catalytic tests were
carried out in a Pyrex fixed-bed reactor, at 450 °C, under atmo-
spheric pressure. The reactor feed was composed by 10 mol% of
reactant (heptane or methylcyclohexane, Merck, 99%) and
90 mol% of N2. The reactant flow rate was maintained constant
(4 mL hÀ1
) with a B. Braun compact perfusor and the nitrogen flow
(120 mL minÀ1
) was controlled by a Brooks Instrument controller.
The reactor effluent samples were taken for different time-
on-stream (TOS): 2, 5, 10, 15, 30 and 60 min, using a 10-position
valve supplied by Vici. The first TOS value was the time necessary
to get a stable reactant pressure in the reactor. The tests were
performed for a contact time (s = 1/WHSV) of 4 min, using about
200 mg of catalyst. The reaction products were analyzed by a
Shimadzu GC-14B gas chromatograph with a Plot Al2O3/KCl fused
silica capillary column (50 m), using a flame ionization detector
(FID) and nitrogen as carrier gas. The heptane and methylcyclohex-
ane conversions were estimated using the areas of the chromato-
graphic peaks (A):
Conversion ð%Þ ¼ 1 À
AReactant
ATotal
 100
2.4. Oleic acid esterification catalytic tests
In order to simulate the biodiesel production by esterification,
the oleic acid conversion into methyl oleate (methylic route) in
presence of methanol was used as model reaction. The experi-
ments were performed under autogenous pressure, in a 20 mL
glass batch reactor at 100 °C. Increased quantities of oleic acid
(Vetec, 99%) were added to 5 mL of methanol (J.T. Baker, 99.9%),
in order to change the oleic acid/alcohol ratio: 1:10, 1:20, and
1:45. The system was maintained under continuous stirring and
the reaction temperature was kept constant using a silicon bath.
The conditions used to obtain the highest oleic acid conversion
were: 10% of catalyst relatively to the quantity of oleic acid used
and 4 h. To determine the conversion, 10 lL of the reaction mixture
were collected and diluted into 1 mL of hexane (Synth, 98.5%), and
50 lL of an internal standard (Tricaprylin – Sigma Aldrich, 99%)
were added. Then, the solution was analyzed in an Agilent
Technology 7890A gas chromatograph, equipped with a FID
detector. The capillary column used was an HP-5 Agilent
(30 m  0.320 mm  0.25 lm), with a polar phase composed by
5% phenyl methyl siloxane. The quantification was performed by
internal standard. The conversions of oleic acid were determined
according to:
Conversion ð%Þ ¼ 1 À
NFinal-ester
NTotal-ester
 100
where NTotal-ester is the total number of moles of methyl oleate that
should be formed according to the reaction stoichiometry and
NFinal-ester the total number of moles of methyl oleate quantified
by CG/FID after 4 h. It is important to refer that the methyl oleate
was the only product detected in the reactor effluent.
3. Results and discussion
3.1. Catalysts characterization
The Si/Al ratio determined from XRF analysis are listed in
Table 1. Logically, parent HZ zeolite shows the lower Si/Al value
(11.4), i.e. the higher amount of aluminum, while all the acid-
treated samples show slightly higher Si/Al ratios (13.9–15.0). For
commodity, XRF results will be discussed more in details together
with the others physicochemical and catalytic results.
Fig. 1 presents the X-ray powder diffractogram obtained for
sample HZ. The latter presents a set of diffraction peaks that corre-
sponds to MFI structure [36]. The peaks are well defined and very
intense, suggesting a high crystalline sample.
Table 1 presents the percentage of crystallinity calculated for
the different samples, using the area of the peaks between 22°
and 25° (2h) and comparing with the area corresponding to the
sample HZ, considered as a reference. The range considered for
the peaks integration, in the case of zeolites with MFI structure,
was used to minimize the influence of sample hydration [37]. It
can be seen that treatment with citric acid does not influence dras-
tically the crystallinity of the different samples, as values between
90% and 100% are obtained.
Fig. 2 presents the sorption isotherm of N2 performed at
À196 °C for the parent HZSM-5 and some samples modified. As
the other modified HZSM-5 samples present similar profiles, they
have not been shown.
The isotherm in Fig. 2 shows the simultaneous presence of
micropores (high initial N2 uptake at P/P0 0.1) and mesopores
that can be evidenced by the presence of a hysteresis loop at higher
P/P0 (close to 1) [38]. The total uptake at high P/P0 can be controlled
by three mechanisms (1) intracrystalline filling at low P/P0; the
multilayer adsorption on the external surface area; and (3) capil-
lary condensation within a secondary pore structure [39]. This type
of isotherm has been assigned by the presence of interparticle mes-
opores created by agglomeration of small crystallites. The surface
of these mesopores (external surface of the crystallites) can contain
active centers [40]. The experimental data were treated according
to [41] (t-plot method) and allowed to provide external area (Sext),
micropores volume (Vmicro) and total pore volume (Vpore) of the dif-
ferent samples.
The results are presented in Table 1. First, it can be seen that HZ
dealumination with citric acid has almost no influence on the final
micropores volumes. However, samples modified with citric acid
show slightly higher total pore volumes (except HZ/0.5/80) and
external surface areas. For HZSM-5, the mesopores contribution
was estimated about 25% to the total pore volume [42]. A similar
trend was verified in a previous study [31] where the authors con-
clude that optimal dealumination conditions were acid citric con-
centration of 1.0 mol LÀ1
and 80 °C. Indeed, textural properties
modifications need to be balanced with the amount of final acid
162 S.S. Vieira et al. / Microporous and Mesoporous Materials 201 (2015) 160–168
4. sites as a too severe dealumination could destroy partially the
structure, leaving only a few strong acid sites necessary for the
reaction studied.
Also, Xin-Mei et al. [29] showed that during acid treatment of Y
zeolite, citric acid molecules formed complexes with Al, giving rise
to the widening of the micropores opening essentially at the exter-
nal surface (because of the size of the citric acid) and that an opti-
mal acid concentration was also needed to optimize the final
zeolite textural and acidic properties.
Regarding the temperature at which the acid treatment was
carried out, it may be inferred that this parameter has no influence
in what concerns HZ dealumination, except for the treatment at
1.0 mol LÀ1
. As referred above, sample HZ/1.0/60 showed the high-
est improvement in terms of external surface area (77 m2
gÀ1
).
Fig. 3 presents the infrared spectra obtained for the different
samples, in the region of the OH groups (3900–3400 cmÀ1
). Differ-
ent OH species can be observed: bridging hydroxyls (Si–(OH)–Al)
(3608 cmÀ1
), terminal silanols Si–OH (3743 cmÀ1
) [43], and finally
OH groups originated from Al species, extra-framework aluminum
species (EFAL) and tri-coordinated Al species connected to struc-
ture oxygen atoms (respectively 3662 and 3780 cmÀ1
) [44,45],
thus indicating the existence of an important amount of EFAL spe-
cies in these samples. Normally, these EFAL species are related to
Lewis acid centers and do not interfere with the other acid sites,
i.e. Brønsted sites, although Al Lewis species have been shown to
enhance the acid strength of the protonic centers [46].
From what it can be observed in Fig. 3, CA treatment using dif-
ferent concentrations and temperatures originates small altera-
tions but detectable. Concerning the band at 3608 cmÀ1
, one can
observe a slight decrease of the band with the acid treatment, i.e.
a decrease of (Si(OH)–Al) groups; in the case of HZ/1.0/80 sample,
this decrease is about 23%, which means that temperature has,
here, an important effect. For the other samples, the decrease of
the band at 3608 cmÀ1
is less pronounced: 9%, 3% and 1% for HZ/
0.5/60, HZ/1.0/60 and HZ/2.0/60, respectively, indicating that
temperature of 60 °C has no or small effect on the intensity of
the (Si–(OH)–Al) band.
Also, it may be noted that band at 3743 cmÀ1
, relative to iso-
lated silanols (Si–OH) groups increases logically with CA treat-
ment, as more surface is created [47] during dealumination
(except for HZ/1.0/80). OH bands related to extra-framework Al
species (3662 and 3780 cmÀ1
) also suffered slight reduction during
dealumination as citric acid can remove EFAL species by complex-
ation and thus reopens channels and pores of the HZ structure [48].
In Fig. 3, it can be also seen how the OH region of the modified
HZ catalysts is altered after pyridine adsorption. For example, the
band at 3608 cmÀ1
disappears completely, confirming the acidic
character of the bridging Si–(OH)–Al species. On the other hand,
the band from EFAL species (3668 cmÀ1
) decreases, but not
completely. Indeed, the band remaining at about 3680 cmÀ1
after
pyridine adsorption might correspond to specific EFAL species pre-
senting a different acidic character and/or accessibility. Logically,
the band from isolated silanols (weak acid sites) at 3743 cmÀ1
seems to be unaffected, or a little, by the presence of adsorbed
pyridine. Finally, the band at 3780 cmÀ1
, corresponding to OH from
tri-coordinated Al species, (also Lewis acid centers) vanishes
completely.
Table 1
Si/Al ratio, percentage of crystallinity and textural parameters calculated for the different samples.
Catalyst Si/Ala
Crystallinity (%) Vmicro (cm3
gÀ1
)b
Vpore (cm3
gÀ1
)b
Sext (m2
gÀ1
)b
HZ 11.4 100 0.14 0.45 69
HZ/0.5/60 14.4 97 0.15 0.49 71
HZ/0.5/80 14.6 97 0.14 0.46 73
HZ/1.0/60 13.9 95 0.15 0.50 77
HZ/1.0/80 14.6 96 0.15 0.49 73
HZ/2.0/60 14.0 94 0.14 0.49 74
HZ/2.0/80 15.0 95 0.15 0.48 72
a
From XRF analysis.
b
From t-plot.
10 20 30 40 50 60
(HZ/1.0/80)
(HZ/1.0/60)
(HZ/0.5/60)
2θ (degree)
Countspersecond
(HZ)
Fig. 1. Powder X-ray pattern of parent HZSM-5 and treated samples.
HZ
50 cm
3
g
-1
Adsorbedvolume(cm3
g-1
)STP
HZ/0.5/60
HZ/1.0/60
HZ/1.0/80
P/P0
0.0 0.2 0.4 0.6 0.8 1.0
Fig. 2. N2 adsorption–desorption isotherm obtained for parent HZ sample: being -
h- adsorption isotherm and -s- desorption isotherm.
S.S. Vieira et al. / Microporous and Mesoporous Materials 201 (2015) 160–168 163
5. Fig. 4 shows the spectra of parent HZSM-5 sample after pyridine
adsorption and subsequent desorption at different temperatures,
in the zone of the pyridine ring frequencies (1700–1350 cmÀ1
).
The spectra of the other samples modified by CA treatment also
show the same set of bands, although with different intensities.
In the spectrum a) (Fig. 4), bands from pyridinium ions (interaction
with Brønsted acid sites) at 1630 and 1540 cmÀ1
and from pyridine
adsorbed onto Al Lewis sites at 1620–1600 and 1455 cmÀ1
can
be observed. The band observed at about 1490 cmÀ1
is common
to the two pyridine species [49,50]. Using the integrated areas of
the bands at 1545 and 1455 cmÀ1
, respectively, allowed the quan-
titative determination of the number of Brønsted and Lewis acid
sites presents in each sample. The molar absorptivity (e) used were
taken from literature [32]. The pyridine desorption at different
temperatures allowed to evaluate the strength of the respective
acid sites. Collidine (2,4,6-trimethylpyridine) was also used in
order to determine quantitatively the amount of Brønsted acid
sites presents at the external surface of the materials [33]; in fact
the larger size of collidine when compared with pyridine (hin-
drance effect), does not allow the molecule to either interact with
Lewis acid sites or with Brønsted acid sites present at the interior
of the MFI structure pores [51].
Table 2 summarizes the different quantitative parameters cal-
culated, namely Brønsted and Lewis acid sites concentration ([B]
and [L] from pyridine), overall Brønsted to Lewis ratio [B]/[L], ratios
B]450/[B]150 and [L]450/[L]150 to evaluate acid sites strength and
finally external acidity concentration (from collidine).
3900 3800 3700 3600 3500 3400
Wavenumber (cm
-1
)
Absorbance(a.u.)
3780 3743 3662
HZ
HZ/0.5/60
HZ_2.0_60
HZ/1.0/80
HZ/1.0/60
3608
3850 3800 3750 3700 3650 3600 3550
Wavenumber (cm
-1
)
Absorbance(a.u.)
a
b
HZ
3850 3800 3750 3700 3650 3600 3550
Absorbance(a.u.)
Wavenumber (cm
-1
)
HZ/0.5/60
b
a
3850 3800 3750 3700 3650 3600 3550
Wavenumber (cm
-1
)
Absorbance(a.u.)
HZ/1.0/60
b
a
3850 3800 3750 3700 3650 3600 3550
Absorbance(a.u.)
Wavenumber (cm
-1
)
HZ/1.0/80
b
a
3850 3800 3750 3700 3650 3600 3550
Wavenumber (cm
-1
)
Absorbance(a.u.)
b
a
HZ/2.0/60
Fig. 3. FTIR spectra in the region of the OH groups and Py-FTIR spectra in the region of the hydroxyl groups of HZ and modified CA samples (a) before and (b) after adsorption
of pyridine at 150 °C.
1700 1650 1600 1550 1500 1450 1400 1350
Absorbance(a.u.)
Wavenumber (cm
-1
)
d
c
b
a
HZ
Fig. 4. FTIR spectra in the region 1700–1350 cmÀ1
after saturation with pyridine
and subsequent desorption at 150 °C (a), 250 °C (b), 350 °C (c) and 450 °C (d) for the
parent HZ.
164 S.S. Vieira et al. / Microporous and Mesoporous Materials 201 (2015) 160–168
6. From Table 2, it can be observed that dealumination caused a
reduction of both Brønsted and Lewis acid sites which is in line
with XRF analysis that showed an increase of the Si/Al ratio, i.e. a
decrease of Al content, for all the materials modified with CA treat-
ment. Comparing the samples obtained for the CA treatment per-
formed at 60 °C, one can see that sample HZ/0.5/60 shows the
most important reduction (21% less acid sites when compared with
the parent zeolite), while for sample HZ/1.0/60, the reduction is
only 7%. This is well in line with XRF results as HZ/0.5/60 shows
the higher Si/Al value of 14.4. It can be concluded that, although
the number of acid sites always decreases with the CA treatment,
this reduction is not linear with the CA concentration used. Con-
cerning the effect of the treatment temperature, we can see that
higher temperature (80 against 60 °C) leads to a higher reduction
of the number of the acid sites (about 30% when comparing with
the parent zeolite). Indeed HZ/1.0/80 shows the highest Si/Al value,
i.e. 14.6.
In what concerns Lewis acidity, we can see that samples
HZ/1.0/60 and HZ/1.0/80 are those where a significant decrease
of Lewis acid sites is observed, that is, there exist optimal condi-
tions (concentration and temperature) for the removal of EFAL Al
species.
An interesting fact is about the external acidity calculated from
collidine adsorption measurements. In Table 2, it can be seen that
external acidity is higher for samples modified with CA treatment,
compared with parent HZ sample, being the maximum attained for
the CA treatment performed at 60 °C (about 29% increase). This
increase of external acidity for the samples modified may be
explained by the increase of external surface area during CA
treatment that allow new acid sites to be accessible for collidine
molecule. This assumption is confirmed in Fig. 5 where a linear
relationship is observed between the external surface area
obtained from N2 adsorption (t-plot method) and the external
acidity determined by collidine adsorption for the different
samples.
3.2. Heptane and methylcyclohexane transformations
Fig. 6a shows the initial heptane conversions (after 2 min TOS)
found for the parent and dealuminated samples. It can be seen that,
despite the slight increase of the total pore volume observed for all
the dealuminated samples (Table 1) and, so, the improved mole-
cules diffusion inside the zeolite porous network, the dealumina-
tion treatment induced a decrease of the conversion for the HZ/
0.5/60 and HZ/1.0/80 zeolites. This can be explained by the much
more important reduction of the concentration of the Brønsted
acid sites observed for these samples, when compared with the
parent zeolite and with the other dealuminated samples (Fig. 6b).
Therefore, for these two samples, due to the acid demanding char-
acter of the heptane transformation, the impact on the conversion
of the decrease of the Brønsted acid sites amount prevails upon the
beneficial effect of enhancing the total pore volume and the acidity
strength of the active sites (Table 2). On the other hand, for the HZ/
1.0/60 and HZ/2.0/60 samples, an increase of the conversion was
noticed, relatively to the parent zeolite. In this case, as the decrease
the number of Brønsted acid sites caused by the dealumination
was not as significant as for the other two dealuminated zeolites
and as the HZ/1.0/60 and HZ/2.0/60 zeolites are the samples pre-
senting the highest Brønsted acidity strength (Table 2) and the
greatest improvement of the total pore volume (Table 1), better
conversion values were obtained.
On the other hand, concerning the results obtained with meth-
ylcyclohexane (Fig. 7), it can be seen that, in spite of the decrease of
the total number of Brønsted acid sites with the dealumination
(Table 2), there is an increase of the activity for all dealuminated
samples (Fig. 7a), which can be mainly correlated with the
enhancement of the external acidity due to the acid treatment, as
it can be seen in Fig. 7b. This is not strange considering that the dif-
fusion of bulky molecules, such as methylcyclohexane, through the
HZSM-5 zeolites channels is, usually, limited by the space avail-
able, i.e. the dimensions of the channels. In fact, methylcyclohex-
ane has a kinetic diameter (5.8 Å) that is slightly higher than the
size of the HZSM-5 pore openings (5.4 Â 5.6 Å–5.1 Â 5.4 Å). This
can also explain the much lower conversion values found for meth-
ylcyclohexane than for heptane, considering that, in absence of
diffusional constraints, methylcyclohexane, being a more reactive
molecule, should present higher conversions [35]. In addition, it
can be observed that the improvement of the conversion for the
dealuminated zeolites depends on the conditions of the treatment,
higher conversions being obtained for the HZ/1.0/60 and HZ/2.0/60
samples than for the HZ/0.5/60 and HZ/1.0/80 zeolites.
Therefore, through the analysis of the heptane and methylcyclo-
hexane results, it can be concluded that HZ/1.0/60 and HZ/2.0/60
dealuminated zeolites appear to be the samples with the most
appropriated properties in terms of acidity and accessibility.
Table 2
Evaluation of Brønsted and Lewis (overall) acidity and external acidity of the different catalysts.
Catalyst Total acidity (lmol gÀ1
) External acidity (lmol gÀ1
)
[B]a
(lmol gÀ1
) [L]b
(lmol gÀ1
) [B]/[L] [B]450/[B]150 [L]450/[L]150
HZ 351 236 1.48 0.13 0.49 34
HZ/0.5/60 275 232 1.18 0.19 0.52 –
HZ/1.0/60 327 194 1.68 0.21 0.57 44
HZ/1.0/80 243 152 1.60 0.16 0.53 40
HZ/2.0/60 298 256 1.17 0.21 0.51 44
a
[B] concentration of Brønsted acid sites.
b
[L] concentration of Lewis acid sites.
30 32 34 36 38 40 42 44 46 48 50
66
68
70
72
74
76
78
80
HZ/1.0/60
HZ/2.0/60
HZ/1.0/80
HZ
Externalsurfacearea(m
2
g
-1
)
External acidity (µmol g
-1
)
Fig. 5. External surface area obtained from N2 adsorption isotherm as a function of
external acidity determined by collidine adsorption.
S.S. Vieira et al. / Microporous and Mesoporous Materials 201 (2015) 160–168 165
7. 3.3. Oleic acid esterification
Fig. 8 presents the results obtained for oleic acid conversion into
methyl oleate with the parent and dealuminated zeolites, for dif-
ferent oleic acid/methanol ratios. It is important to refer that some
catalytic tests were also carried out in absence of catalyst, under
the same operating conditions, in order to evaluate the extent of
the thermal conversion and, so, the contribution of the catalyst
for the final conversion. Actually, it is claimed that temperature
alone can have a great effect on the conversion of the oleic acid
[18]. The conversions obtained without catalysts were about 34%,
35% and 27% for the 1:45, 1:20 and 1:10 M ratios, respectively,
meaning that, effectively, the temperature can significantly influ-
ence the results. This behavior may be explained by the presence
of Brønsted acidity in the fatty acids.
Analyzing the results found in presence of catalysts, it can be
seen that the parent HZSM-5 was active for the conversion of the
oleic acid into methyl oleate and that the conversions attained
were higher than those obtained in absence of catalyst, confirming
the beneficial effect of using a catalyst. Moreover, it can be noticed
that, whatever the acid oleic/methanol molar ratio, there is a
further improvement of the oleic acid conversion when using
0
5
10
15
20
25
Conversionofheptane(%)
HZ/2.0/60HZ/1.0/80HZ/1.0/60HZ/0.5/60HZ
(a)
100 150 200 250 300 350
0
4
8
12
16
20
24
28
Conversionofheptane(%)
Brønstedacidsites (µmol g
-1
)
HZ/1.0/80 HZ/0.5/60
HZ/1.0/60
HZ
HZ/2.0/60
(b)
Fig. 6. (a) Heptane initial conversion (2 min TOS) for the parent and dealuminated zeolites and (b) evolution of the heptane initial conversion with the number of Brønsted.
0
2
4
6
8
10
HZ/2.0/60HZ/1.0/80HZ/1.0/60HZ/0.5/60HZ
Conversionofmethylcyclohexane(%)
(a)
30 35 40 45 50
0
2
4
6
8
10
HZ/1.0/60
HZ/2.0/60
HZ/1.0/80
HZ
External acidity (μmol g
-1
)
Conversionofmethylcyclohexane(%)
(b)
Fig. 7. (a) Methylcyclohexane initial conversion (2 min TOS) for the parent and dealuminated zeolites and (b) evolution of the methylcyclohexane initial conversion with
external acidity.
Fig. 8. Oleic acid conversions obtained for the different oleic acid/methanol ratios.
166 S.S. Vieira et al. / Microporous and Mesoporous Materials 201 (2015) 160–168
8. dealuminated zeolites, which is dependent on the dealumination
degree. The maximum oleic acid conversions were obtained for
the HZ/1.0/60 zeolite. This clearly shows that the zeolites when
treated with citric acid can lead to better results for the esterifica-
tion reaction.
The increase of the oleic acid conversion with the dealumina-
tion can be a result of several effects. According to Chung and Park
[19], who studied the oleic acid esterification on different acid zeo-
lites (HMFI, HMOR, HFAU and HBEA), both the quantity and
strength of acid sites can have an important role in the oleic acid
conversion, the latter parameter being the most relevant. For the
dealuminated zeolites of the present study, it was observed a
decrease of the total number of Brønsted acid sites, but this was
accompanied by an enhancement of their acid strength (Table 2),
which could, so, result in an increase of the conversion.
Nevertheless, the improved acidity strength should only explain
in part the better oleic acid conversions obtained with the treated
zeolites. In fact, in this analysis, it is also important to consider that
the oleic acid molecule presents a kinetic diameter (5.5 Å, Gaussian
09 program) that is very close to the size of the HZSM-5 pore open-
ing (5.4 Â 5.6 Å–5.1 Â 5.4 Å). This means that most of the oleic acid
molecules are not able to enter and diffuse within the HZSM-5 zeo-
lite channels, even more at low reaction temperature. Therefore,
the reaction should mainly take place on the outer surface of the
zeolites. Consequently, the evolution of oleic acid conversion with
the external surface area and the total external acidity was evalu-
ated (Fig. 9). It can be seen that, effectively, the higher these
parameters, the greater the conversion values obtained, confirming
that, for this particular zeolite, the oleic acid conversion is mainly
governed by the enhancement of the zeolite external surface prop-
erties. Actually, the treatment with citric acid, can lead to a higher
external surface and, so, to an increase of the number of acid sites
accessible to oleic acid molecules.
Hence, globally, the best oleic acid conversion results were
obtained for both the HZ/1.0/60 and HZ/2.0/60 dealuminated sam-
ples, as they registered the smallest loss of Brønsted acid sites and
the highest increase of the acidity strength, external surface area
and external acidity. The improved characteristics of these two
zeolites were also confirmed by methylcyclohexane and heptane
transformations data.
Another important remark is that the increase of the catalysts
efficiency with the dealumination treatment seems to be even
more significant at higher acid oleic/methanol molar ratios
(Fig. 8). For the parent HZSM-5 zeolite, a decrease of about 37%
in conversion can be observed with the increase of the acid oleic/
methanol molar ratios to 1:45 from 1:10, whereas, for the dealumi-
nated samples, only 2–20% of reduction was noticed. Indeed, the
enhanced molecules diffusion and the higher number of molecules
reaching the acid sites on the dealuminated samples could enhance
the esterification reaction kinetics, without being necessary to use
higher methanol amounts to improve thermodynamics. Thus, the
possibility to operate with lower quantities of methanol using dea-
luminated zeolites could be important at an industrial point of
view, since it would allow using smaller size equipment and lower
energy inputs. Table 3 presents studies using zeolites as catalysts
for biodiesel production via esterification.
4. Conclusion
The results indicated that mild dealumination treatments
performed on HZSM-5 zeolites with citric acid are beneficial for
68 70 72 74 76 78 80
50
55
60
65
70
75
80
85
90
HZ/2.0/60
HZ/0.5/60 HZ/1.0/80
HZ/1.0/60
HZ
External area (m
2
g
-1
)
Conversionofoleicacid(%)
(a)
30 32 34 36 38 40 42 44 46 48 50
50
55
60
65
70
75
80
85
90
HZ/1.0/60
HZ/2.0/60
HZ/1.0/80
External acidity (µmol g-1
)
HZ
Conversionofoleicacid(%)
(b)
Fig. 9. Evolution of the oleic acid conversion with (a) external surface area and (b) external acidity.
Table 3
Comparison of maximum esterification conversions using zeolites and those obtained in this study.
Catalysts Reaction conditions Conversion (%) References
Temperature (°C) Catalysts (%) Molar ratio Time (h)
HZ 100 10 1:45 4 55 Present study
HZ/1.0/60 100 10 1:45 4 83 Present study
HZSM-5 100 10 1:45 7 80 [16]
La2O3/SO4
2À
/HZSM-5 100 10 1:45 7 100 [16]
HBEA 130 2 1:3 1 35 [18]
HMOR 130 2 1:3 1 50 [18]
HZSM-5 130 2 1:3 1 40 [18]
HY 130 2 1:3 1 35 [18]
HMFI 60 5.5 1:15 1 80 [19]
HMOR 60 5.5 1:15 1 80 [19]
HFAU 60 5.5 1:15 1 75 [19]
HBEA 60 5.5 1:15 1 70 [19]
USY 200 10 1:6 2 73.9 [52]
WO3/USY 200 10 1:6 2 80 [52]
S.S. Vieira et al. / Microporous and Mesoporous Materials 201 (2015) 160–168 167
9. esterification reaction of oleic acid into methyl oleate. The materi-
als modified with citric acid treatments, using different concentra-
tions and temperatures, evidenced as slight increase of external
surface areas and a reduction of both Brønsted and Lewis acid sites
which is in line with the increase of the Si/Al ratio from 11 to 15.
The samples treated at 60 °C presented the highest Brønsted acid-
ity strength and the greatest improvement of external surface area
which explains the increase of external acidity measured by
collidine adsorption followed by FTIR. These samples present the
most appropriated properties in terms of acidity and accessibility
for promoting the oleic acid conversion that appears to be mainly
governed by the enhancement of the zeolite external surface
properties. The results also showed that whatever the acid oleic/
methanol molar ratio, there is a further improvement of the oleic
acid conversion when using dealuminated zeolites.
Acknowledgment
The authors thank CAPES for granting the scholarship, FAPEMIG
and CNPq for financial support, LGRQ/UFLA for chromatographic
analyses, Instituto Superior Técnico (IST, Lisbon) for materials
characterization, in particular Prof. Teresa Duarte for access to
the XRD facility (CONC-REEQ/670/2001) and Zeochem by HZSM-
5 sample.
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