Inducing effect of hydrogen peroxide on synchronous oxidation reaction is accompanied by the occurrence of two interconnected and interacting reactions. The reaction of Н2О2 decomposition (primary) generates the leading active OH and HO 2 free radicals in a system. During the interaction of active and free radicals with the substrate, the conversion of the substrate occurs in the secondary reaction, coherently-synchronized with the primary one. The mechanism of such coherently synchronized reactions is being examined in the process of cyclohexane oxidation with hydrogen peroxide in homogeneous and heterogeneous systems. The process of coupling dehydrogenation of cyclohexane to cyclohexene and cyclohexadiene with hydrogen peroxide was carried out without catalyst. This process was also carried out at a fairly low temperature in a heterogeneous catalytic system. Biomimetic catalyst, which simulates the basic functions of the enzyme group of oxidoreductase - catalase and monooxygenase, was used as the catalyst here. Characterised by its highly active and selective action these biomimetic catalysts are synthesized based on iron-porphyrin complexes simulating the active component of cytochrome P-450. Based on this experimental researches, the complex reaction, consisting of parallel-sequential oxidation and dehydrogenation reactions, which are coherently synchronized, proceeds during the process of cyclohexane oxidation with biomimetic catalyst. Depending on the reaction parameters it is possible to deliberately adjust the direction of oxidation reaction and reaction rate.
Introduction
Basis
Importance
Classification
Homogeneous catalysis
Mechanism
Example
Heterogeneous catalysis
Mechanism
Examples
Promoters
Catalytic Poisoning
Autocatalysis
Enzyme catalysis
Enzymes
References
Catalyst: -
The substances that alter the rate of a reaction but itself remains chemically unchanged at the end of the reaction is called a Catalyst.
The process is called Catalysis.
prop-
A catalyst cannot start the reaction by itself.
Catalytic activity increases as surface area of catalyst increases.
Catalysts are thermolabile, this effect is very well pronounced in enzymes.
Catalytic activity is maximum at a catalyst’s optimum temperature.
A catalyst does not alter the position of the equilibrium, instead it helps in achieving the equilibrium faster.
Reaction of aniline with ammonium persulphate and concentrated hydrochloric a...Maciej Przybyłek
In this paper, the reaction of aniline with ammonium persulphate and concentrated HCl was studied. As a result of our experimental studies, 2,4,6-trichlorophenylamine was identified as the main product. This shows that a high concentration of HCl does not favour oxidative polymerisation of phenylamine, even though the ammonium persulphate/HCl system is widely used in polyaniline synthesis. On the basis of the experimental data and density functional theory for reaction path modelling, we proposed a mechanism for oxidative chlorination of aniline. We assumed that this reaction proceeded in three cyclically repeated steps; protonation of aniline, formation of singlet ground state phenylnitrenium cation, and nucleophilic substitution. In order to confirm this mechanism, kinetic, thermochemical, and natural bond orbital population analyses were performed.
V mn-mcm-41 catalyst for the vapor phase oxidation of o-xylenesunitha81
The role of V and Mn incorporated mesoporous molecular sieves was
investigated for the vapor phase oxidation of o-xylene. Mesoporous monometallic
V-MCM-41 (Si/V = 25, 50, 75 and 100), Mn-MCM-41 (Si/Mn = 50) and bimetallic
V-Mn-MCM-41 (Si/(V ? Mn) = 100) molecular sieves were synthesized by
a direct hydrothermal (DHT) process and characterized by various techniques such
as X-ray diffraction, DRUV-Vis spectroscopy, EPR, and transmission electron
microscopy (TEM). From the DRUV-Vis and EPR spectral study, it was found that
most of the V species are present as vanadyl ions (VO2?) in the as-synthesized
catalysts and as highly dispersed V5? ions in tetrahedral coordination in the calcined
catalysts. The activity of the catalysts was measured and compared with each other
for the gas phase oxidation of o-xylene in the presence of atmospheric air as an
oxidant at 573 K. Among the various catalysts, V-MCM-41 with Si/V = 50
exhibited high activity towards production of phthalic anhydride under the experimental
condition. The correlation between the phthalic anhydride selectivity and
the physico-chemical characteristics of the catalyst was found. It is concluded that
V5? species present in the MCM-41 silica matrix are the active sites responsible for
the selective formation of phthalic anhydride during the vapor phase oxidation of
o-xylene.
Introduction
Basis
Importance
Classification
Homogeneous catalysis
Mechanism
Example
Heterogeneous catalysis
Mechanism
Examples
Promoters
Catalytic Poisoning
Autocatalysis
Enzyme catalysis
Enzymes
References
Catalyst: -
The substances that alter the rate of a reaction but itself remains chemically unchanged at the end of the reaction is called a Catalyst.
The process is called Catalysis.
prop-
A catalyst cannot start the reaction by itself.
Catalytic activity increases as surface area of catalyst increases.
Catalysts are thermolabile, this effect is very well pronounced in enzymes.
Catalytic activity is maximum at a catalyst’s optimum temperature.
A catalyst does not alter the position of the equilibrium, instead it helps in achieving the equilibrium faster.
Reaction of aniline with ammonium persulphate and concentrated hydrochloric a...Maciej Przybyłek
In this paper, the reaction of aniline with ammonium persulphate and concentrated HCl was studied. As a result of our experimental studies, 2,4,6-trichlorophenylamine was identified as the main product. This shows that a high concentration of HCl does not favour oxidative polymerisation of phenylamine, even though the ammonium persulphate/HCl system is widely used in polyaniline synthesis. On the basis of the experimental data and density functional theory for reaction path modelling, we proposed a mechanism for oxidative chlorination of aniline. We assumed that this reaction proceeded in three cyclically repeated steps; protonation of aniline, formation of singlet ground state phenylnitrenium cation, and nucleophilic substitution. In order to confirm this mechanism, kinetic, thermochemical, and natural bond orbital population analyses were performed.
V mn-mcm-41 catalyst for the vapor phase oxidation of o-xylenesunitha81
The role of V and Mn incorporated mesoporous molecular sieves was
investigated for the vapor phase oxidation of o-xylene. Mesoporous monometallic
V-MCM-41 (Si/V = 25, 50, 75 and 100), Mn-MCM-41 (Si/Mn = 50) and bimetallic
V-Mn-MCM-41 (Si/(V ? Mn) = 100) molecular sieves were synthesized by
a direct hydrothermal (DHT) process and characterized by various techniques such
as X-ray diffraction, DRUV-Vis spectroscopy, EPR, and transmission electron
microscopy (TEM). From the DRUV-Vis and EPR spectral study, it was found that
most of the V species are present as vanadyl ions (VO2?) in the as-synthesized
catalysts and as highly dispersed V5? ions in tetrahedral coordination in the calcined
catalysts. The activity of the catalysts was measured and compared with each other
for the gas phase oxidation of o-xylene in the presence of atmospheric air as an
oxidant at 573 K. Among the various catalysts, V-MCM-41 with Si/V = 50
exhibited high activity towards production of phthalic anhydride under the experimental
condition. The correlation between the phthalic anhydride selectivity and
the physico-chemical characteristics of the catalyst was found. It is concluded that
V5? species present in the MCM-41 silica matrix are the active sites responsible for
the selective formation of phthalic anhydride during the vapor phase oxidation of
o-xylene.
OXIDATION OF POLYETHYLENE GLYCOL-200 BY POTASSIUM PERIODATE IN ALKALINE MEDIU...Ratnakaram Venkata Nadh
Kinetics of PEG-200 oxidation by potassium periodatewas studied in alkaline medium. First-order dependence of
reaction on periodate was observed. Rate of the reaction was found to be independent of substrate concentration.
An inverse fractional order with respect to alkaliwas shown. Arrhenius parameters were calculated. Rate law was
postulated taking into consideration of experimental results.
Formulation and operation of a Nickel based methanation catalystSakib Shahriar
The objective of this experiment was to get a firsthand experience of the preparation of a catalyst for methanation reaction and to evaluate the performance of the catalyst in a fixed bed tubular reactor. In the first part of the experiment a nickel-based catalyst was synthesized. The catalyst will have nickel as the active component and alumina as the support. the catalyst precursor was prepared by co-precipitation from a solution of nitrate salts of nickel and aluminum. The precipitate was filtered out, washed, dried and calcined to obtain the catalyst. In the second part, the catalyst was activated and performance analysis was done alone with loaded in a fixed bed reactor. The percentage conversion of CO to CH4 was 96.38% and the selectivity of CH4 production to CO2 production was 3.348.
CYCLOHEXANE – PHENOL BINARY LIQUID MIXTURE: BEHAVIOR AND PARAMETERS AT CRITIC...ijrap
A new liquid binary cyclohexane - phenol mixture was prepared. The dynamic shear viscosity coefficients of this liquid mixture, for different phenol concentrations and temperatures, were investigated by capillary viscometer made from glass. The dynamic shear viscosity showed an anomaly close to the critical temperature 푇푐 = 17.0 ℃. The anomaly behavior was observed at critical weight concentration of phenol, 푥푐 = 2.70 %. At temperatures above critical one, the experimental data were fitted using mode Coupling Theory. It was found that the dynamic shear viscosity non-critical background had a value of 휂0 = 0.8174 cP. Also, using a pycnometer of 10 ml, density measurements were performed. The expected law for mass density above critical temperature was the power law. The noncritical mass density part was found to have a value of 휌0 = 0.7357 푔푚 푐푚3 . In addition, The isobaric thermal expansion coefficient at critical temperature (훼푝푐) was also deduced and found to have a value of 2.07 × 10−6 ℃−1 . Finally, the derivative of critical temperature with respect to pressure (푇푐 ′ ) was found to have a value 1.22 × 10−4 퐾 푃푎 .
Kinetic And Mechanism of Oxidation of Cobalt Metal Complex By Acidic Potassiu...IJMERJOURNAL
ABSTRACT: The Kinetic of oxidation of Cobalt derived from 8-hydroxy quinolone and salicylaldehyde by potassium permanganate has been studied in the presence of acidic medium. The overall reaction is first order with respect to KMnO4, Substrate acid and temperature. No effect of salts has been found suitable mechanism is given.
CONVERSION OF DIMETHYL-NITROBENZENE TO DIMETHY L ANILINE, EFFECT OF SOME PROC...Berklin
The catalytic transfer hydrogenation of dimethyl-nitrobenzene (DN) to Dimethyl-aniline (DA) was studied
in the temperature range 343–403 K
o
, pressure range of 4–10 bar H2 and ethanol as solvent using Pd/C
as catalyst above agitation speed 800 rpm. The substrate feed concentration was varied in the range from
0.124 to 0.745 kmol/m3
while catalyst loading was in the range 4–12% (w/w) of dimethyl-nitrobenzene.
Dimethyl-aniline was the only reaction product, generated through the hydrogenation of the Nitro group of
dimethyl-nitrobenzene. The effects of hydrogen partial pressure, catalyst loading, dimethyl-nitrobenzene
concentration and temperature on the reaction conversion have been reported. Near first-order
dependence on dimethyl-nitrobenzene concentration and hydrogen pressure were observed for the initial
rate of dimethyl-nitrobenzene hydrogenation over the 5% Pd/C catalyst. Furthermore, an increase in the
catalytic activity as the reaction temperature, pressure and weight of catalysts was observed. Conventional
Arrhenius behavior was exhibited by catalyst, Pd/C showed activation energies of 614 J/mol.
PTC IS THE PHASE TRANSFER CATALYSIS HERE TYPES OF PTC ARE DISCUSSED , THEORIES OF CATALYSIS AND MECHANISM OF PTC, ADVANTAGES OF PTC, APPLICATION OF PTC
This slide completely describes you about the stuff include in it and also everything about chemical engineering. Fluid Mechanics. Thermodynamics. Mass Transfer Chemical Engineering. Energy Engineering, Mass Transfer 2, Heat Transfer,
Chemical reduction technique for the synthesis of nickel nanoparticlesIJERA Editor
Chemical reduction technique was used to synthesize nickel powder using hydrazine hydrate as reducing agent,
nickel chloride hexahydrate as precursor and polyvinylpyrrolidone (PVP) as capping agent in ethylene glycol
medium. Experiments were carried out with mole ratios 13:1 and 20:1 of hydrazine to nickel chloride
hexahydrate by keeping the amounts of ethylene glycol and NaOH as constant. Variation of capping agent
concentration and temperature was also studied. X-ray diffraction (XRD) analysis was performed and the crystal
size was calculated using Debye-Scherrer equation. XRD peaks where corresponds to that of the face-centered
cubic nickel crystals, in accordance with the literature. Likewise, no oxygen peaks were found in XRD pattern,
which confirm the absence of oxide formation in nickel. Morphological studies were performed using scanning
electron microscopy (SEM) and the elemental composition was determined using energy dispersive X-ray
analysis. The elemental composition was found to be nickel with small traces of oxygen.
Effect of Operating Conditions on CSTR performance: an Experimental StudyIJERA Editor
In this work, Saponification reaction of ethyl acetate by sodium hydroxide is studied experimentally in a continuous stirred tank reactor at 1 atmospheric pressure. The aim of this study is to investigate the influence of operating conditions on the conversion and specific rate constant. The parameters considered for analysis are temperature, feed flow rate, residence time, volume of reactor and stirrer rate. The steady state conversion of 0.45 achieved after a period of 30 minutes. Conversion decreases with increase of reactant flow rate due to decrease of residence time. The stirrer rate has a positive effect on the conversion and rate constant. Specific rate constant and conversion increase with temperature within the studied temperature range. Within the range of reactor volume selected for analysis, conversion increases with increase in reactor volume. The results obtained in this study may be helpful in maximizing the conversion of ethyl acetate saponification reaction at industrial scale in a CSTR.
Study of the Influence of Nickel Content and Reaction Temperature on Glycerol...IJRESJOURNAL
ABSTRACT: La2O3-SiO2-supported nickel catalysts were evaluated in glycerol steam reforming. The samples (30wt% La and 5, 10 and 15wt% of Ni on 70wt% commercial SiO2), prepared by the simultaneous impregnation method, were characterized by EDX, nitrogen physisorption, XRD, in-situ XRD, XANES and TPR. The analyses revealed NiO species weakly interact with the support and the different metallic surface areas of the catalysts. Catalytic tests were performed in a fixed bed reactor at 600oC and 15Ni catalyst, which showed the best performance, was also evaluated at 500oC and 700oC. According to the results, the Ni content on the catalyst surface interferes in the distribution of gaseous products H2, CO, CO2 and CH4. The increase in the Ni content increases the carbon formation during reaction. The reaction temperature affected the catalytic performance and the best results were obtained with the 15Ni catalyst at 600oC, which was also tested for 20 hours for the analysis of its stability.
OXIDATION OF POLYETHYLENE GLYCOL-200 BY POTASSIUM PERIODATE IN ALKALINE MEDIU...Ratnakaram Venkata Nadh
Kinetics of PEG-200 oxidation by potassium periodatewas studied in alkaline medium. First-order dependence of
reaction on periodate was observed. Rate of the reaction was found to be independent of substrate concentration.
An inverse fractional order with respect to alkaliwas shown. Arrhenius parameters were calculated. Rate law was
postulated taking into consideration of experimental results.
Formulation and operation of a Nickel based methanation catalystSakib Shahriar
The objective of this experiment was to get a firsthand experience of the preparation of a catalyst for methanation reaction and to evaluate the performance of the catalyst in a fixed bed tubular reactor. In the first part of the experiment a nickel-based catalyst was synthesized. The catalyst will have nickel as the active component and alumina as the support. the catalyst precursor was prepared by co-precipitation from a solution of nitrate salts of nickel and aluminum. The precipitate was filtered out, washed, dried and calcined to obtain the catalyst. In the second part, the catalyst was activated and performance analysis was done alone with loaded in a fixed bed reactor. The percentage conversion of CO to CH4 was 96.38% and the selectivity of CH4 production to CO2 production was 3.348.
CYCLOHEXANE – PHENOL BINARY LIQUID MIXTURE: BEHAVIOR AND PARAMETERS AT CRITIC...ijrap
A new liquid binary cyclohexane - phenol mixture was prepared. The dynamic shear viscosity coefficients of this liquid mixture, for different phenol concentrations and temperatures, were investigated by capillary viscometer made from glass. The dynamic shear viscosity showed an anomaly close to the critical temperature 푇푐 = 17.0 ℃. The anomaly behavior was observed at critical weight concentration of phenol, 푥푐 = 2.70 %. At temperatures above critical one, the experimental data were fitted using mode Coupling Theory. It was found that the dynamic shear viscosity non-critical background had a value of 휂0 = 0.8174 cP. Also, using a pycnometer of 10 ml, density measurements were performed. The expected law for mass density above critical temperature was the power law. The noncritical mass density part was found to have a value of 휌0 = 0.7357 푔푚 푐푚3 . In addition, The isobaric thermal expansion coefficient at critical temperature (훼푝푐) was also deduced and found to have a value of 2.07 × 10−6 ℃−1 . Finally, the derivative of critical temperature with respect to pressure (푇푐 ′ ) was found to have a value 1.22 × 10−4 퐾 푃푎 .
Kinetic And Mechanism of Oxidation of Cobalt Metal Complex By Acidic Potassiu...IJMERJOURNAL
ABSTRACT: The Kinetic of oxidation of Cobalt derived from 8-hydroxy quinolone and salicylaldehyde by potassium permanganate has been studied in the presence of acidic medium. The overall reaction is first order with respect to KMnO4, Substrate acid and temperature. No effect of salts has been found suitable mechanism is given.
CONVERSION OF DIMETHYL-NITROBENZENE TO DIMETHY L ANILINE, EFFECT OF SOME PROC...Berklin
The catalytic transfer hydrogenation of dimethyl-nitrobenzene (DN) to Dimethyl-aniline (DA) was studied
in the temperature range 343–403 K
o
, pressure range of 4–10 bar H2 and ethanol as solvent using Pd/C
as catalyst above agitation speed 800 rpm. The substrate feed concentration was varied in the range from
0.124 to 0.745 kmol/m3
while catalyst loading was in the range 4–12% (w/w) of dimethyl-nitrobenzene.
Dimethyl-aniline was the only reaction product, generated through the hydrogenation of the Nitro group of
dimethyl-nitrobenzene. The effects of hydrogen partial pressure, catalyst loading, dimethyl-nitrobenzene
concentration and temperature on the reaction conversion have been reported. Near first-order
dependence on dimethyl-nitrobenzene concentration and hydrogen pressure were observed for the initial
rate of dimethyl-nitrobenzene hydrogenation over the 5% Pd/C catalyst. Furthermore, an increase in the
catalytic activity as the reaction temperature, pressure and weight of catalysts was observed. Conventional
Arrhenius behavior was exhibited by catalyst, Pd/C showed activation energies of 614 J/mol.
PTC IS THE PHASE TRANSFER CATALYSIS HERE TYPES OF PTC ARE DISCUSSED , THEORIES OF CATALYSIS AND MECHANISM OF PTC, ADVANTAGES OF PTC, APPLICATION OF PTC
This slide completely describes you about the stuff include in it and also everything about chemical engineering. Fluid Mechanics. Thermodynamics. Mass Transfer Chemical Engineering. Energy Engineering, Mass Transfer 2, Heat Transfer,
Chemical reduction technique for the synthesis of nickel nanoparticlesIJERA Editor
Chemical reduction technique was used to synthesize nickel powder using hydrazine hydrate as reducing agent,
nickel chloride hexahydrate as precursor and polyvinylpyrrolidone (PVP) as capping agent in ethylene glycol
medium. Experiments were carried out with mole ratios 13:1 and 20:1 of hydrazine to nickel chloride
hexahydrate by keeping the amounts of ethylene glycol and NaOH as constant. Variation of capping agent
concentration and temperature was also studied. X-ray diffraction (XRD) analysis was performed and the crystal
size was calculated using Debye-Scherrer equation. XRD peaks where corresponds to that of the face-centered
cubic nickel crystals, in accordance with the literature. Likewise, no oxygen peaks were found in XRD pattern,
which confirm the absence of oxide formation in nickel. Morphological studies were performed using scanning
electron microscopy (SEM) and the elemental composition was determined using energy dispersive X-ray
analysis. The elemental composition was found to be nickel with small traces of oxygen.
Effect of Operating Conditions on CSTR performance: an Experimental StudyIJERA Editor
In this work, Saponification reaction of ethyl acetate by sodium hydroxide is studied experimentally in a continuous stirred tank reactor at 1 atmospheric pressure. The aim of this study is to investigate the influence of operating conditions on the conversion and specific rate constant. The parameters considered for analysis are temperature, feed flow rate, residence time, volume of reactor and stirrer rate. The steady state conversion of 0.45 achieved after a period of 30 minutes. Conversion decreases with increase of reactant flow rate due to decrease of residence time. The stirrer rate has a positive effect on the conversion and rate constant. Specific rate constant and conversion increase with temperature within the studied temperature range. Within the range of reactor volume selected for analysis, conversion increases with increase in reactor volume. The results obtained in this study may be helpful in maximizing the conversion of ethyl acetate saponification reaction at industrial scale in a CSTR.
Study of the Influence of Nickel Content and Reaction Temperature on Glycerol...IJRESJOURNAL
ABSTRACT: La2O3-SiO2-supported nickel catalysts were evaluated in glycerol steam reforming. The samples (30wt% La and 5, 10 and 15wt% of Ni on 70wt% commercial SiO2), prepared by the simultaneous impregnation method, were characterized by EDX, nitrogen physisorption, XRD, in-situ XRD, XANES and TPR. The analyses revealed NiO species weakly interact with the support and the different metallic surface areas of the catalysts. Catalytic tests were performed in a fixed bed reactor at 600oC and 15Ni catalyst, which showed the best performance, was also evaluated at 500oC and 700oC. According to the results, the Ni content on the catalyst surface interferes in the distribution of gaseous products H2, CO, CO2 and CH4. The increase in the Ni content increases the carbon formation during reaction. The reaction temperature affected the catalytic performance and the best results were obtained with the 15Ni catalyst at 600oC, which was also tested for 20 hours for the analysis of its stability.
Biomass is considered as a potential source of energy production.Gasification can be employed to convert
dilute biomass energy source in to gaseous products holding concentrated form of energy. A steady state model for fluidized
bed biomass gasifier is developed based on reaction kinetics and hydrodynamic aspects of fluidization. The presence of
sorbent for absorption of carbon dioxide from the product gas is also incorporated in the model.The developed model
predicts the variation of syngas composition, temperature, pressure and velocity along the height of gasifier. Experiments
were carried out in a lab scale fluidized bed biomass gasifier and the results were used to validate the model.An increase of
50.35% in H2 mole fraction and a decrease of 50.88 % in CO2 mole fraction were observed when CaO was used as the
sorbent.
Rh/CeO2 Thin Catalytic Layer Deposition on Alumina Foams: Catalytic Performan...CarmenMoncada10
The application of ceramic foams as structured catalyst supports is clearly expanding due to faster mass/heat transfer and higher contact efficiency than honeycomb monoliths and, mainly, packed beds. In this paper, alumina open-cell foams (OCFs) with different pore density (20, 30 and 40 ppi) were coated with Rh/CeO2 catalyst via a two steps synthesis method involving: (i) the solution combustion synthesis (SCS) to in-situ deposit the CeO2 carrier and (ii) the wet impregnation (WI) of the Rh active phase. The catalytic coatings were characterized in terms of morphology and adhesion properties by SEM/EDX analysis and ultrasounds test. Permeability and form coefficient were derived from pressure drop data. Catalytic performance was evaluated towards biogas Steam Reforming (SR) and Oxy-Steam Reforming (OSR) processes at atmospheric pressure by varying temperature (800–900 °C) and space velocity (35,000–140,000 NmL·g−1·h−1). Characteristics time analysis and dimensionless numbers were calculated to identify the controlling regime. Stability tests were performed for both SR and OSR over 200 h of time-on-stream (TOS) through consecutive start-up and shut-down cycles. As a result, homogenous, thin and high-resistance catalytic layers were in situ deposited on foam struts. All structured catalysts showed high activity, following the order 20 ppi < 30 ppi ≈ 40 ppi. External interphase (gas-solid) and external diffusion can be improved by reducing the pore diameter of the OCF structures. Anderson criterion revealed the absence of internal heat transfer resistances, as well as Damköhler and Weisz-Prater numbers excluded any internal mass transfer controlling regime, mainly due to thin coating thickness provided by the SCS method. Good stability was observed over 200 h of TOS for both SR and OSR processes.
Visible Light Photocatalytic Degradation of Methylene Blue and Malachite Gree...IJEAB
A facile solid state metathesis synthesis of barium tungstate (BaWO4) followed by ball milling and subsequent preparation of barium tungstate-graphene oxide (BaWO4–GO) nano composite using a colloidal blending process and its application as a visible light photocatalyst for the degradation of Malachite green and Methylene blue dyes. The morphology and composition of barium tungstate (BaWO4) nano composite have been characterized using X-Ray Diffraction (XRD), UV–Visible Diffuse Reflectance Spectra (UV-DRS), Raman Spectra, Field Emission Scanning Electron Microscopy (FESEM) – EDAX and UV Visible Spectroscopy. This composite material is found to be a wide band gap semiconductor with band gap of 4.3 eV. The sample shows poor transmittance in ultraviolet region while it has maximum transmittance in visible-near infrared regions. It shows an increase in range and intensity of light absorption and the reduction of electron–hole pair recombination in BaWO4 with the introducing of GO on to it.
Sunlight induced removal of Rhodamine B from water through Semiconductor Pho...Hariprasad Narayanan
Application of Advanced Oxidation Processes (AOP) for the removal of toxic pollutants from water has been receiving increasing
attention in recent times. Photocatalysis using semiconductor oxides is one such AOP which is being investigated extensively for
the degradation of dyes in effluent water. This paper reports our findings on the sunlight induced photocatalytic removal of the
hazardous xanthene dye Rhodamine B from water, mediated by TiO2 and ‘platinum deposited TiO2’ (Pt/TiO2).Unlike in the case of
photocatalytic degradation of many organic pollutants which are driven by UV light, Rhodamine B can be removed in presence of
TiO2 even by visible light. Pt/TiO2 is ~5 times more active than TiO2 alone for the solar photocatalytic degradation of the dye,
which is attributed to extension of the absorption of light to the visible range and retardation of the recombination of
photogenerated electrons and holes. The dye itself can absorb visible light and act as a photo sensitizer to activate TiO2. The
effects of various parameters such as catalyst loading, concentration of the dye, pH, Pt concentration in Pt/TiO2, externallyadded
H2O2 etc on the adsorption and /or degradation of the dye are evaluated. The degradation of the dye proceeds through
intermediates and complete removal of Total Organic Carbon (TOC) is achieved many hours after the decolorisation of the dye.
The rate of degradation decreases beyond a critical concentration of the dye, possibly due to reduction in the path length of
photons in deeply colored solution. The higher degradation in alkaline pH is explained in terms of the ionization state of the
catalyst surface and the enhanced adsorption facilitated by the electrostatic attraction between the negatively charged catalyst
surface and the zwitter ionic form of the dye. H2O2, upto a critical concentration, accelerates the degradation. The observations are
critically analysed and suitable mechanism for the photocatalytic mineralisation of RhB is proposed.
Supercritical water oxidation for the treatment of various organic wastes: A ...AI Publications
The removal of complex organic and chemical industrial wastes is not accessible using conventional treatment methods. Incineration and hydrothermal oxidation under supercritical conditions are two options for dealing with a wide range of hazardous wastes. Incineration is an effective treatment for removing hazardous waste. The main disadvantages of incineration are a source of unwanted emissions and high operating costs. Supercritical water oxidation (SCWO) is considered a green technology for destroying organic waste with friendly environmental emissions. The removal efficiency reached 99.99% within a short residence time. In this review, the treatment of organic waste by SCWO is shown using co-fuel and catalysts to enhance the performance of SCWO.
Similar to Kinetics and Mechanism of the Reaction of Coherently Synchronized Oxidation and Dehydrogenation of Cyclohexane by Hydrogen Peroxide (20)
Harnessing WebAssembly for Real-time Stateless Streaming PipelinesChristina Lin
Traditionally, dealing with real-time data pipelines has involved significant overhead, even for straightforward tasks like data transformation or masking. However, in this talk, we’ll venture into the dynamic realm of WebAssembly (WASM) and discover how it can revolutionize the creation of stateless streaming pipelines within a Kafka (Redpanda) broker. These pipelines are adept at managing low-latency, high-data-volume scenarios.
Using recycled concrete aggregates (RCA) for pavements is crucial to achieving sustainability. Implementing RCA for new pavement can minimize carbon footprint, conserve natural resources, reduce harmful emissions, and lower life cycle costs. Compared to natural aggregate (NA), RCA pavement has fewer comprehensive studies and sustainability assessments.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
We have compiled the most important slides from each speaker's presentation. This year’s compilation, available for free, captures the key insights and contributions shared during the DfMAy 2024 conference.
NUMERICAL SIMULATIONS OF HEAT AND MASS TRANSFER IN CONDENSING HEAT EXCHANGERS...ssuser7dcef0
Power plants release a large amount of water vapor into the
atmosphere through the stack. The flue gas can be a potential
source for obtaining much needed cooling water for a power
plant. If a power plant could recover and reuse a portion of this
moisture, it could reduce its total cooling water intake
requirement. One of the most practical way to recover water
from flue gas is to use a condensing heat exchanger. The power
plant could also recover latent heat due to condensation as well
as sensible heat due to lowering the flue gas exit temperature.
Additionally, harmful acids released from the stack can be
reduced in a condensing heat exchanger by acid condensation. reduced in a condensing heat exchanger by acid condensation.
Condensation of vapors in flue gas is a complicated
phenomenon since heat and mass transfer of water vapor and
various acids simultaneously occur in the presence of noncondensable
gases such as nitrogen and oxygen. Design of a
condenser depends on the knowledge and understanding of the
heat and mass transfer processes. A computer program for
numerical simulations of water (H2O) and sulfuric acid (H2SO4)
condensation in a flue gas condensing heat exchanger was
developed using MATLAB. Governing equations based on
mass and energy balances for the system were derived to
predict variables such as flue gas exit temperature, cooling
water outlet temperature, mole fraction and condensation rates
of water and sulfuric acid vapors. The equations were solved
using an iterative solution technique with calculations of heat
and mass transfer coefficients and physical properties.
Kinetics and Mechanism of the Reaction of Coherently Synchronized Oxidation and Dehydrogenation of Cyclohexane by Hydrogen Peroxide
1. S. Aghamammadova et al. Int. Journal of Engineering Research and Application www.ijera.com
ISSN : 2248-9622, Vol. 7, Issue 2, ( Part -2) February 2017, pp.36-40
www.ijera.com DOI: 10.9790/9622- 0702023640 36 | P a g e
Kinetics and Mechanism of the Reaction of Coherently
Synchronized Oxidation and Dehydrogenation of Cyclohexane by
Hydrogen Peroxide
S. Aghamammadova 1
, I. Nagieva 2
, L. Gasanova 1
, T. Nagiev 1, 2, a
1
Nagiev Institute of Catalysis and Inorganic Chemistry, National Academy of Sciences of Azerbaijan
2
Baku State University, Azerbaijani Republic
ABSTRACT
Inducing effect of hydrogen peroxide on synchronous oxidation reaction is accompanied by the occurrence of
two interconnected and interacting reactions. The reaction of Н2О2 decomposition (primary) generates the
leading active OH
and
2HO free radicals in a system. During the interaction of active and free radicals with the
substrate, the conversion of the substrate occurs in the secondary reaction, coherently-synchronized with the
primary one.
The mechanism of such coherently synchronized reactions is being examined in the process of cyclohexane
oxidation with hydrogen peroxide in homogeneous and heterogeneous systems.
The process of coupling dehydrogenation of cyclohexane to cyclohexene and cyclohexadiene with hydrogen
peroxide was carried out without catalyst. This process was also carried out at a fairly low temperature in a
heterogeneous catalytic system.
Biomimetic catalyst, which simulates the basic functions of the enzyme group of oxidoreductase - catalase and
monooxygenase, was used as the catalyst here. Characterised by its highly active and selective action these
biomimetic catalysts are synthesized based on iron-porphyrin complexes simulating the active component of
cytochrome P-450.
Based on this experimental researches, the complex reaction, consisting of parallel-sequential oxidation and
dehydrogenation reactions, which are coherently synchronized, proceeds during the process of cyclohexane
oxidation with biomimetic catalyst. Depending on the reaction parameters it is possible to deliberately adjust the
direction of oxidation reaction and reaction rate.
I. INTRODUCTION
Inducing effect of hydrogen peroxide on
synchronous oxidation reaction is accompanied by
the occurrence of two interconnected and interacting
reactions [1, 2]. The reaction of Н2О2 decomposition
(primary) generates the leading active OH
and
2HO
free radicals in a system. During the interaction of
active and free radicals with the substrate, the
conversion of the substrate occurs in the secondary
reaction, coherently-synchronized with the primary
one [3].
The mechanism of such coherently
synchronized reactions is being examined in the
process of cyclohexane oxidation with hydrogen
peroxide in homogeneous and heterogeneous
systems. The cyclohexane oxidation is the most
commonly studied process, where the valuable for
organic synthesis compounds are achieved during
oxidative dehydrogenation or during oxidation [4-7].
The implementation of thermodynamically hindered
reactions is of great interest for petrochemical and
organic synthesis. Among them the reactions of
partial dehydrogenation of cyclohexane to
cyclohexene and cyclohexadiene should be
mentioned.
kJ/mol,G
2106126 HHCHC 39.88
286106 HHCHC 115.37
It is of course more beneficial in terms of
energy to carry out such reactions in conjunction
with other reactions, in this case, with the reaction of
hydrogen peroxide decomposition.
II. RESULTS AND DISCUSSION
The process of coupling dehydrogenation of
cyclohexane to cyclohexene and cyclohexadiene
with hydrogen peroxide was carried out without
catalyst [8].
The reaction was examined at a temperature
range of 450-650 ºC at various flow rates and ratios
of starting reactants. The process was of sequential
and autocatalytic nature with the period of self-
acceleration (kinetic curves for cyclohexadiene and
benzene), as shown in Figure 1. Under optimum
conditions, the yield of cyclohexene was up to
RESEARCH ARTICLE OPEN ACCESS
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19.4%, of cyclohexadiene was 3.4% and benzene
2.4%.
Figure 1. Kinetic curves for coupling
dehydrogenation of cyclohexane:
1-cyclohexane; 2-cyclohexene; 3-benzene; 4-
cyclohexadiene
Kinetic curves show that the accumulation
of cyclohexene as an intermediate product at the
initial stage of the process increases up until the rate
of its consumption and the rate of accumulation at
the conventional contact time equal to τ = 4.2c,
becomes equal, and cyclohexene concentration
reaches a maximum value. Cyclohexene yield
decreases with the further increase in contact time.
The rate of formation of cyclohexene and
cyclohexadiene initially increases, and reaches its
maximum at the inflection point, which is typical for
sequential reactions.
At a temperature range of 450-500 ºC the
cyclohexene is formed, with the increase in
temperature range between 560 ºC and 650 ºC
dehydrogenation products contain cyclohexadiene
and benzene along with cyclohexene. These data also
suggest that with further increase in temperature the
ring-opening decomposition reaction of the
cyclohexane occurs along with the process of the
dehydrogenation. The consequence is the formation
of gaseous products such as Н2, СО2, СН4, С2Н4...
These experimental data aggregate show
that in the studied range of variations by reaction
parameters under the best conditions reaction
proceeds in the direction of the oxidative
dehydrogenation of cyclohexane achieving the yield
of desired products C6H10, C6H8 и C6H6 – 19,4%;
3.4% and 2.4% respectively.
It is necessary to identify the nature of the
interaction of Н2О2 with the hydrocarbon, resulting
with the formation of unsaturated compound under
high-temperature oxidation conditions in order to
identify the mechanism of dehydrogenation of
cyclohexane.
A prerequisite for the coherently
synchronized reactions to proceed in the reaction
system is its quantitative characteristic defined by the
determinant equation [1]:
1
21 )//(
асас rrrrD
where r1 and r2 – consumption rate of an actor (Н2О2)
in the primary and secondary reactions respectively,
rac - consumption rate of an acceptor (С6Н12), ν -
stoichiometric factor (in our case ν = 1). The value of
the determinants calculated by using experimental
data D≈0.1 indicates the induced nature of
dehydrogenation of cyclohexane.
Under the conditions of the high-
temperature cyclohexane gas-phase oxidation with
hydrogen peroxide, the reaction proceeds by a free
radical mechanism, where active OH
and
2HO
radicals are formed in the primary reaction - in the
reaction of Н2О2 decomposition, and they are
consumed in the secondary one - in the
dehydrogenation of cyclohexane. Considering that at
a high temperature the concentration of
2HO
radicals in the reaction system is much higher than
the concentration of OH
radicals [9], the
2HO
radicals play a key role in the mechanism of the
dehydrogenation:
chain initiation
kJ/mol9,217222
OHOH
chain propagation
kJ/mol9,66
kJ/mol6,104
kJ/mol17,40
kJ/mol7,107
266286
2862106
21062126
2222
OHOHHCHOHC
OHOHHCHOHC
OHOHHCHOHC
OHHOOHOH
chain termination
)(
)(
22 adsHOwallHO
adsOHwallOH
Each successive reaction of oxidative
dehydrogenation of cyclohexane is a combination of
chain initiation, propagation and termination stages.
The system of kinetic equations, adequately
describing the experimental data, is as follows [10]:
]][[/][ 221261126 OHHCkdHCd eff
]][[]][[/][ 221062221261106 OHHCkOHHCkdHCd effeff
]][[]][[/][ 2286322106286 OHHCkOHHCkdHCd effeff
where
smolsmRTk eff /)264000exp(10
39,24
1
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smolsmRTk eff /)222000exp(10
39,23
2
smolsmRTk eff /)205000exp(10
38,22
3
Examination of the process of coherently
synchronized cyclohexane oxidation with hydrogen
peroxide was carried out also at a fairly low
temperature in a heterogeneous catalytic system.
Biomimetic catalyst [11], which simulates the basic
functions of the enzyme group of oxidoreductase -
catalase and monooxygenase, was used as the
catalyst here. Characterised by its highly active and
selective action these biomimetic catalysts are
synthesized based on iron-porphyrin complexes
simulating the active component of cytochrome P-
450 [12].
The process of cyclohexane gas phase
oxidation was carried out with heterogeneous
biomimetic catalysts per-FTPhPFe(III)/Al2O3 and
PPFe(III)/Al2O3 at a temperature of 130 – 250 ºС
and a molar ratio С6Н12: Н2О2 = 1:1.7 with 25%
aqueous Н2О2 solution. The results of these studies
are shown in Figure 2.
Figure 2. The dependence of the reaction yield of cyclohexane coherently synchronized oxidation with bio simulator per-
Table 1. The dependence of the reaction yield of cyclohexanol coherently synchronized oxidation with bio simulator per-
FTPhPFe(III)/Al2O3 on the temperature: [H2O2]=20%,
22 OHV =1,41 mL/h, 126 HCV =0,9 mL/h, C6H11ОН:H2O2=1:1
Composition of feedstock, % Composition of obtained reaction yield, %
t, 0
C C6H11OH
2-methyl
cyclohex
anol
Hexanoi
c acid
Hexanoic
acid
cyclohexy
l ester
C6H11OH C6H10
1,2 cyclo
hexane
diol
1,3
cyclohexa
diene
2-methyl
cyclohexa
nol
other
oxygena
tes
Conversi
on
150
180
200
230
97,524
97,524
97,524
97,524
0,481
0,481
0,481
0,481
0,712
0,712
0,712
0,712
0,845
0,845
0,845
0,845
83,921
78,186
67,494
55,255
2,321
7,841
16,688
30,374
2,248
2,875
2,887
2,0
0,105
0,145
0,279
0,1
0,093
0,583
0,295
0,641
9,405
10,753
10,652
10,271
14,079
19,814
30,506
42,745
As shown in Figure 2 at the temperature up
to150-160 ºС the reaction that mainly proceeds is
cyclohexane oxidation reaction, forming
cyclohexanol and cyclohexanone. At the temperature
above 180°C the reaction of oxidative
dehydrogenation of cyclohexane to cyclohexene
(curve 4, Figure 2) begins to accelerate, respectively,
the yield of cyclohexanol and cyclohexanone
decreases. The sharp increase in the yield of
cyclohexene along with the decrease in the yield of
formed cyclohexanol indicates that at the
temperature of 230 ºС or higher cyclohexanol can
also be converted into cyclohexene at lower
concentrations of Н2О2 in the reaction system. This
conclusion is confirmed by the results of
experimental studies of the process of cyclohexanol
oxidation with hydrogen peroxide at a lower
concentration (20%) with the biomimetic catalyst,
where at elevated temperature (200-230 ºС) the
cyclohexene yield is high (16-30%).
The experiments on the effect of the Н2О2
concentration at a constant temperature (200 ºС) and
contact time were conducted. As shown in Figure 3,
increased Н2О2 concentration in the reaction zone
contributes to the increase of oxidation reaction rate,
which results with the increase of cyclohexanone
yield and decrease of cyclohexene yield.
Such results are obtained in a pilot study of
cyclohexane oxidation over biomimetic depending
on the С6H12 : H2O2 ratio at different temperatures.
The results of the effect of the С6H12 : H2O2
ratio on the cyclohexane oxidation reaction at a
moderate temperature (t = 150 °C), where
cyclohexanol and cyclohexanone are the main
reaction products are shown in Figure 3.
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As it can be seen from the Figure 4 the
reaction rate of oxidative dehydrogenation is higher
than oxidation reaction rate and the yield of
cyclohexane increases at the highest temperature (t =
230 °C).
Figure 3. The dependence of the reaction yield of
cyclohexane coherently synchronized oxidation with
bio simulator per-FTPhPFe(III)/Al2O3 on
concentration Н2О2: t=2000
C, 22 OHV =1,41 mL/h,,
126 HCV =0,9 mL/h,,
1- conversion; 2- cyclohexanol; 3- cyclohexanone; 4-
cyclohexene; 5- cyclohexadiene; 6- O2 yield
Figure 4. The dependence of the reaction yield of
cyclohexane coherently synchronized oxidation over
per-FTPhPFe(III)/Al2O3catalyst on С6H12 : H2O2ratio
at the temperature t=1500
C,
22 OH
V =1,41mL/h,, 126 HC
V =0,9mL/h,,
1- conversion; 2- cyclohexanol;
3- cyclohexanone; 4- O2yield
Figure 5. The dependence of the reaction yield of
cyclohexane coherently synchronized oxidation over
per-FTPhPFe(III)/Al2O3catalyst on С6H12 : H2O2ratio
at the temperature t=2300
C,
22 OH
V =1,41mL/h,, 126 HC
V =0,9mL/h,,
1- conversion; 2- cyclohexanol; 3- cyclohexanone; 4-
cyclohexene; 5- cyclohexadiene; 6- O2 yield
Thus, the complex reaction, consisting of
parallel-sequential oxidation and dehydrogenation
reactions, which are coherently synchronized,
proceeds during the process of cyclohexane
oxidation with biomimetic catalyst. Depending on
the reaction parameters it is possible to deliberately
adjust the direction of oxidation reaction and reaction
rate.
It should be noted that in terms of the
mechanism of each stage of this complex reaction of
cyclohexane parallel-sequential oxidation with
hydrogen peroxide with biomimetics, each oxidation
reaction is carried out under inducing effect of
hydrogen peroxide intermediates and consists of two
coherently synchronized reactions - 1) catalase (Н2О2
decomposition reaction) and 2) monooxygenase
(cyclohexane oxidation reaction) with biomimetic
catalyst.
The probable mechanism of cyclohexane
coherently synchronized oxidation, considering the
parallel-sequential nature of oxidation and
dehydrogenation, can be expressed by the general
scheme [3]:
The mechanism of primary and secondary
reactions proceeding over biomimetic catalyst is
given:
1
2
H2O + O2
react. prod. (С6H11OH;
C6H10O; C6H10; C6H8;
C6H6)
С6Н12; C6H10; C6H8; С6H11OH
ImtOH
ImtOOHH2O
H2O2
H2O2
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1) Mechanism of catalase reaction
2) The mechanism of reaction of cyclohexane
oxidation to cyclohexanol
H2C
H2C CH2
C
CH2H2C
H
H
OH
OFe
H2C
H2C
H2C CH2
C
CH2
H
OH
B
B
H
A
H
A
Fe OH
III. CONCLUSION
The scheme shows that formed active
intermediate complex of hydroperoxide (ImtOOH),
as in the case of free radical
2HO , is the key active
centre for coherent synchronization of catalase
(primary) and monooxygenase (secondary) reactions.
Coherently synchronized nature of the cyclohexane
oxidation reaction follows from the experimental
data (Figure 2 and 3). The changes in the catalase
reaction rate (curve 6) and the rate of cyclohexane
oxidation consumption (curve 1) are shown by the
kinetic curves of Figures 2 and 3.
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