This document describes a study that used ultrahigh-resolution mass spectrometry to characterize a weathering series of crude oil from the Deepwater Horizon spill. The study found an increase in oxygenated compounds in more weathered oils, suggesting the formation of acidic, ketonic, and quinonic compounds through oxidation processes during weathering. The use of multiple ionization modes was able to provide more comprehensive characterization by accessing different functional groups in the complex oil mixtures.
Production of Hydrocarbons from Palm Oil over NiMo Catalystdrboon
This document summarizes a study on the hydrodeoxygenation of palm oil over a NiMo catalyst. Key findings include:
1. Palm oil was converted to hydrocarbons ranging from C15 to C18 under various reaction conditions in a continuous stirred tank reactor.
2. The amount of desired hydrocarbon products increased with reaction temperature up to 628K but decreased at higher temperatures likely due to cracking reactions.
3. Selectivity to C16 and C18 hydrocarbons was higher than C15 and C17, respectively, and the Cn+1/Cn ratio decreased with increasing temperature indicating more decarbonylation/decarboxylation.
4. In the presence of the
Kinetics and feasibility studies of thiol oxidation using magnetically separa...Pawan Kumar
This work describes kinetic studies of the catalytic oxidation of thiols (RSHs) found in kerosene to disulphides
using a magnetically separable iron oxide coated Mg-Al layered double hydroxide supported tetra-sulphonated
cobalt phthalocyanine (CoPcS/LDH@Fe3O4) catalyst in an alkali-free environment. Using 1-octanethiol as a representative
RSH, we investigated the effects of different experimental parameters on RSH oxidation kinetics, including
catalyst concentration, temperature (30–60 °C), and initial thiol concentration ([RSH]0, 100–300 ppm).
The catalyst concentration was varied so that the [RSH]0/[Co]tot molar ratio ranged from 45 to 180. Based on
the results, we propose a mechanistic rate expression to explain the observed oxidation of RSH in the presence
of the CoPcS/LDH@Fe3O4 catalyst. The proposed rate law resembles double substrate Michaelis-Menten kinetics,
however, for commonly encountered industrial conditions, we were able to simplify it to a linear form. This rate
law for RSH oxidation can be used to design industrial reactors for an alkali-free sweetening process.
This document provides an overview of petroleum geology, including:
1. It defines petroleum geology as the study of the origin, generation, migration, and accumulation of hydrocarbons, with the goal of exploring for and producing oil and gas.
2. Petroleum can occur as liquid (crude oil), gas (natural gas), or solid/semi-solid forms like asphalt or bitumen. Natural gas exists as either associated or non-associated gas.
3. Crude oils vary in properties like specific gravity, viscosity, pour point, and optical activity. The origin of petroleum is now widely accepted to be organic rather than inorganic.
Kinetics and feasibility studies of thiol oxidation using magnetically separa...Pawan Kumar
This research article studies the kinetics of catalytic oxidation of thiols to disulfides using a novel magnetically separable catalyst. The catalyst contains cobalt phthalocyanine grafted onto an iron oxide-coated layered double hydroxide supported on magnetic iron oxide nanoparticles. Experiments were conducted to investigate the effects of various parameters on thiol oxidation kinetics, including catalyst concentration, temperature, and initial thiol concentration. Kinetic data was analyzed to propose a rate law that could be used to design industrial reactors for an alkali-free sweetening process.
This document provides information about the composition of crude oil, including:
1. Crude oil is composed primarily of hydrocarbon compounds like alkanes, cycloalkanes, and aromatic hydrocarbons. It also contains smaller amounts of other organic compounds containing sulfur, nitrogen, and oxygen, as well as trace metals.
2. The specific molecular composition varies between crude sources, but on average crude oil is 83-87% carbon, 10-14% hydrogen, and contains 0.1-6.0% sulfur and 0.1-2.0% nitrogen.
3. Other hydrocarbon groups found in crude include paraffins (alkanes), naphthenes (cycloalkanes), and aromatic
This document provides information on the composition of crude oil. It discusses that crude oil is a mixture of hydrocarbons that is liquid underground but varies in color from yellow to black. It is composed primarily of carbon and hydrogen. The main components are paraffins, naphthenes, and aromatics. Crude oil also contains smaller amounts of other elements and compounds like sulfur. The document also describes different methods of classifying crude oils based on their chemical composition and geological parameters.
Crude oil, also known as black gold, is a complex mixture of hydrocarbons found in sedimentary rocks. It is believed to have formed from the remains of ancient plants and animals over millions of years. Crude oil is composed mainly of paraffin hydrocarbons, along with other components like naphthenes, aromatics, asphaltenes and various chemical elements. The four main categories of hydrocarbon types in crude oil are paraffins, olefins, naphthenes and aromatics, which have varying molecular structures and properties. Crude oil can also contain small amounts of sulfur, nitrogen, oxygen and heavy metal compounds.
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.
Production of Hydrocarbons from Palm Oil over NiMo Catalystdrboon
This document summarizes a study on the hydrodeoxygenation of palm oil over a NiMo catalyst. Key findings include:
1. Palm oil was converted to hydrocarbons ranging from C15 to C18 under various reaction conditions in a continuous stirred tank reactor.
2. The amount of desired hydrocarbon products increased with reaction temperature up to 628K but decreased at higher temperatures likely due to cracking reactions.
3. Selectivity to C16 and C18 hydrocarbons was higher than C15 and C17, respectively, and the Cn+1/Cn ratio decreased with increasing temperature indicating more decarbonylation/decarboxylation.
4. In the presence of the
Kinetics and feasibility studies of thiol oxidation using magnetically separa...Pawan Kumar
This work describes kinetic studies of the catalytic oxidation of thiols (RSHs) found in kerosene to disulphides
using a magnetically separable iron oxide coated Mg-Al layered double hydroxide supported tetra-sulphonated
cobalt phthalocyanine (CoPcS/LDH@Fe3O4) catalyst in an alkali-free environment. Using 1-octanethiol as a representative
RSH, we investigated the effects of different experimental parameters on RSH oxidation kinetics, including
catalyst concentration, temperature (30–60 °C), and initial thiol concentration ([RSH]0, 100–300 ppm).
The catalyst concentration was varied so that the [RSH]0/[Co]tot molar ratio ranged from 45 to 180. Based on
the results, we propose a mechanistic rate expression to explain the observed oxidation of RSH in the presence
of the CoPcS/LDH@Fe3O4 catalyst. The proposed rate law resembles double substrate Michaelis-Menten kinetics,
however, for commonly encountered industrial conditions, we were able to simplify it to a linear form. This rate
law for RSH oxidation can be used to design industrial reactors for an alkali-free sweetening process.
This document provides an overview of petroleum geology, including:
1. It defines petroleum geology as the study of the origin, generation, migration, and accumulation of hydrocarbons, with the goal of exploring for and producing oil and gas.
2. Petroleum can occur as liquid (crude oil), gas (natural gas), or solid/semi-solid forms like asphalt or bitumen. Natural gas exists as either associated or non-associated gas.
3. Crude oils vary in properties like specific gravity, viscosity, pour point, and optical activity. The origin of petroleum is now widely accepted to be organic rather than inorganic.
Kinetics and feasibility studies of thiol oxidation using magnetically separa...Pawan Kumar
This research article studies the kinetics of catalytic oxidation of thiols to disulfides using a novel magnetically separable catalyst. The catalyst contains cobalt phthalocyanine grafted onto an iron oxide-coated layered double hydroxide supported on magnetic iron oxide nanoparticles. Experiments were conducted to investigate the effects of various parameters on thiol oxidation kinetics, including catalyst concentration, temperature, and initial thiol concentration. Kinetic data was analyzed to propose a rate law that could be used to design industrial reactors for an alkali-free sweetening process.
This document provides information about the composition of crude oil, including:
1. Crude oil is composed primarily of hydrocarbon compounds like alkanes, cycloalkanes, and aromatic hydrocarbons. It also contains smaller amounts of other organic compounds containing sulfur, nitrogen, and oxygen, as well as trace metals.
2. The specific molecular composition varies between crude sources, but on average crude oil is 83-87% carbon, 10-14% hydrogen, and contains 0.1-6.0% sulfur and 0.1-2.0% nitrogen.
3. Other hydrocarbon groups found in crude include paraffins (alkanes), naphthenes (cycloalkanes), and aromatic
This document provides information on the composition of crude oil. It discusses that crude oil is a mixture of hydrocarbons that is liquid underground but varies in color from yellow to black. It is composed primarily of carbon and hydrogen. The main components are paraffins, naphthenes, and aromatics. Crude oil also contains smaller amounts of other elements and compounds like sulfur. The document also describes different methods of classifying crude oils based on their chemical composition and geological parameters.
Crude oil, also known as black gold, is a complex mixture of hydrocarbons found in sedimentary rocks. It is believed to have formed from the remains of ancient plants and animals over millions of years. Crude oil is composed mainly of paraffin hydrocarbons, along with other components like naphthenes, aromatics, asphaltenes and various chemical elements. The four main categories of hydrocarbon types in crude oil are paraffins, olefins, naphthenes and aromatics, which have varying molecular structures and properties. Crude oil can also contain small amounts of sulfur, nitrogen, oxygen and heavy metal compounds.
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.
This document provides an overview of petroleum refinery engineering. It discusses the origin and composition of crude oil, refinery processes like distillation, cracking and reforming, and auxiliary operations. It also lists recommended books and introduces concepts like crude oil properties, hydrocarbon groups, non-hydrocarbon compounds, origin of hydrocarbons, exploration techniques, and physical properties of crude oil.
Physical and chemical properties of petroleumkhurasani
Petroleum is a naturally occurring liquid found beneath the Earth's surface that is refined into fuels. It consists mainly of hydrocarbons like alkanes, naphthenes, and aromatics. Petroleum forms from the thermal maturation of buried organic matter over millions of years. It varies in composition but is largely made up of carbon and hydrogen, with other elements like sulfur, oxygen, and nitrogen present in smaller amounts. The type of petroleum depends on factors like the organic material it formed from and temperature/pressure conditions during formation.
This document summarizes a study investigating ultra-deep adsorptive desulfurization of diesel fuel over supported TiO2−CeO2 adsorbents. Key findings include:
1) Light irradiation of diesel fuel prior to adsorption treatment resulted in a 30-fold increase in desulfurization capacity compared to untreated fuel, achieving sulfur removal to below 1 ppmw.
2) Sulfur K-edge XANES analysis identified sulfones as the primary sulfur species on spent adsorbents, suggesting light irradiation chemically transforms original sulfur compounds.
3) Adsorption selectivity tests showed higher removal of indole and sulfones compared to thiophenes and poly
The document provides instructions for experiments to qualitatively analyze unknown samples of carbohydrates. It includes the theory, procedures, observations, and conclusions for tests to identify monosaccharides, disaccharides, and polysaccharides. Students are asked to perform a series of chemical tests on provided carbohydrate samples and unknowns to determine their identities based on color changes and precipitate formations.
Visible light assisted photocatalytic reduction of CO2 using a graphene oxide...Pawan Kumar
A new heteroleptic ruthenium complex containing 2-thiophenyl benzimidazole ligands was synthesized
using a microwave technique and was immobilized to graphene oxide via covalent attachment. The synthesized
catalyst was used for the photoreduction of carbon dioxide under visible light irradiation without
using a sacrificial agent, which gave 2050 μmol g−1 cat methanol after 24 h of irradiation
Visible light assisted photocatalytic reduction of CO2 using a graphene oxide...Pawan Kumar
A new heteroleptic ruthenium complex containing 2-thiophenyl benzimidazole ligands was synthesized
using a microwave technique and was immobilized to graphene oxide via covalent attachment. The synthesized
catalyst was used for the photoreduction of carbon dioxide under visible light irradiation without
using a sacrificial agent, which gave 2050 μmol g−1 cat methanol after 24 h of irradiation
Organic chemistry revision notes cover the formation of fossil fuels like oil from dead marine organisms under heat and pressure. Crude oil is separated into fractions like gasoline and kerosene through fractional distillation, and combustion produces pollution like carbon monoxide and nitrogen oxides. The energy released during combustion can be measured using a calorimeter. Homologous series are families of compounds with the same functional group and general formula that differ by CH2. Main series include alkanes, alkenes, and alcohols, which are named based on their carbon chain and functional group.
This study investigated the polymerization of lactic acid as a model for prebiotic peptide formation via ester-amide exchange. Lactic acid was polymerized in a closed system at 85°C over various time points. HPLC and 1H-NMR were used to analyze the polymers and determine degree of polymerization (DP) and total lactic acid units. DP was found to increase with time while total units decreased, showing polymer regeneration. Methods showed consistent results within 10-15% error. Further studies will compare kinetics to a computer simulation to determine rate constants and model polymerization from various monomers.
Phase transfer catalysis involves using a catalyst to transfer a reactant from one immiscible liquid phase to another where the reaction takes place. Common phase transfer catalysts are quaternary ammonium and phosphonium salts. The catalyst forms an ion pair with the reactant anion, transporting it into the organic phase where it undergoes nucleophilic substitution or other reactions. Phase transfer catalysis allows reactions between ions and organic molecules that would otherwise not interact due to being in separate phases. It has many applications in organic synthesis and pharmaceutical manufacturing.
The document describes Ishmael Masesane's research journey from classical chemistry to transfer hydrogenation of alkenes using palladium catalysis and various organic acids. It then discusses the development of enantioselective versions of this reaction using chiral organic acids like mandelic acid and tartaric acid. Finally, it outlines Masesane's approaches to synthesizing cyclic beta-amino acid derivatives using Diels-Alder reactions of furan with acrylates or maleic anhydride to form oxanorbornyl intermediates.
Synthesis of Oxygenated Fuel Additives via Acetylation of Bio-Glycerol over H...DanesBlake
Abstract
Growing global biodiesel production demands valorization of bio-glycerol derived from biodiesel, which is crucial to make biorefinery process economical. Hence, a series of H2SO4 modified sulfonated Montmorillonite K10 catalysts were synthesized, characterized, and evaluated for acetylation of bio- glycerol with acetic acid to produce mono acetin (MAG), di acetin (DAG), tri acetin (TAG), and di-glycerol tri-acetate (DGTA), which are the oxygenated fuel additives and facilitate the economic viability of biodiesel production so the biorefinery. The synthesized catalysts were characterized by a compressive suite of characterization techniques such as powder X-ray diffraction (XRD), low temperature N2 physisorption, temperature-programmed ammonia desorption (TPAD), and Fourier transform infrared (FTIR). The glycerol conversion and product distribution results were found to correlate with the acidity and textural properties of the catalyst. 20% (w/w) SO4/K10 was revealed to be a promising catalyst for glycerol acetylation with 99% glycerol conversion and with respective yield towards MAG, DAG, TGA and DGTA of 23%, 59%, 15%, and 2%. Moreover, 20% (w/w) SO4/K10 catalyst
was found to maintain the stable catalytic activity for three reaction cycles. However, the partial catalyst deactivation was observed after third reaction cycle, partly due to deposition of coke and loss of active sites during the reaction. https://crimsonpublishers.com/pps/fulltext/PPS.000501.php
Synthesis of Oxygenated Fuel Additives via Acetylation of Bio-Glycerol over H...crimsonpublisherspps
1) The document discusses the acetylation of glycerol, a byproduct of biodiesel production, using sulfonated montmorillonite K10 catalysts.
2) A series of H2SO4-modified sulfonated montmorillonite K10 catalysts were synthesized and characterized. They were then evaluated for catalyzing the acetylation of glycerol with acetic acid to produce oxygenated fuel additives.
3) The 20% (w/w) SO4/K10 catalyst achieved 99% glycerol conversion and respective yields of 23% for MAG, 59% for DAG, 15% for TAG, and 2% for DGTA. This catalyst also maintained
Biomass to olefins cracking of renewable naphthapxguru
This document discusses cracking renewable naphtha produced from biomass to produce light olefins like ethylene and propylene. The biomass is first converted to a renewable naphtha fraction using a two-step process involving hydrodeoxygenation and hydrocracking. Comprehensive characterization of the renewable naphtha showed it consists mainly of paraffins suitable for steam cracking. Steam cracking this naphtha in a pilot plant yielded high amounts of ethylene (31 wt%) and propylene (17.5 wt%) while producing small amounts of byproducts. Experimental coking studies also showed this naphtha feed has attractive coking properties. Simulations predict higher run lengths compared to fossil n
Meulepas, 2010, Biotechnological Aspects Of Sulfate Reduction With Methane As...roelmeulepas
This review paper discusses the biotechnological aspects of using methane as an electron donor for sulfate reduction. Sulfate reduction is an important process in the carbon and sulfur cycles in nature. It can be used to remove and recover oxidized sulfur compounds from waste streams. Traditionally, hydrogen and ethanol are used as electron donors but methane would be more attractive due to lower costs. The paper reviews the microbial pathways and thermodynamics of sulfate reduction with methane, as well studies using bioreactors. Further research is needed to improve the extremely low growth rates of the responsible microorganisms to enable practical applications.
Crude oil is a complex mixture of hydrocarbons that are separated into useful fractions via fractional distillation. It is formed from the remains of ancient microorganisms and plants that were deposited under intense heat and pressure over millions of years. The key fractions obtained include liquid petroleum gas, gasoline, kerosene, diesel, and fuel oils of varying viscosity. When burned as fuels, the hydrocarbon molecules in crude oil and its fractions react with oxygen to produce carbon dioxide, water vapor, and other emissions.
This document describes the synthesis and characterization of a manganese(III) complex intended to mimic the active site of superoxide dismutase (SOD) enzymes. A tetradentate ligand containing two quinoline groups (DQEA) was synthesized and characterized using NMR and IR spectroscopy. This ligand was then reacted with manganese(III) acetate to form the Mn(III) complex. The ability of this complex to catalyze the dismutation of superoxide, mimicking SOD activity, was confirmed using the Fridovich assay. Overall, the goal was to develop a low molecular weight SOD mimic that could function as a potential pharmaceutical for reducing oxidative stress.
Physical and Chemical Properties of HydricarbonsMasoom Shani
The document discusses the physical and chemical properties of petroleum. It defines various types of hydrocarbons such as oil, natural gas, condensates, and their classification. It describes the composition of natural gas and crude oil. It also discusses the key terms used in petroleum geology such as source rock, reservoir rock, seal rock, and the refining process.
Petroleum, also known as crude oil, is a naturally occurring liquid found beneath the Earth's surface. It is composed primarily of hydrocarbons such as carbon and hydrogen. Crude oil is extracted from the ground through oil wells, either because it flows naturally due to underground pressures or through mechanical pumping. There are several theories for the origin of petroleum, but the modern theory is that it formed from the decomposition of marine organisms and terrestrial plant material over millions of years. Once extracted, crude oil undergoes processing to remove impurities and separate it into useful petroleum products through distillation. These products include fuels like gasoline, diesel and jet fuel, as well as other commodities like lubricating oils, asphalt and
This document summarizes a study that analyzed model petroleum compounds using high-resolution mass spectrometry with atmospheric pressure photoionization (APPI), atmospheric pressure chemical ionization (APCI), and electrospray ionization (ESI) in order to better understand the ionization efficiency of different compound classes. The study found that APPI was able to ionize the widest range of compounds, including two-ring PAHs, oxygenated PAHs, and anhydrides. APCI and ESI were more limited in the compounds they could ionize. Factors like size, structure, functional groups, heteroatom content, and methylation level affected ionization efficiency across the sources. Alkanes could not be ion
This document provides an overview of coal gasification. It discusses the purposes and benefits of converting coal to gas. Integrated coal gasification combined cycle is highlighted as an important application due to its high efficiency and potential to meet emission standards. The document outlines coal gasification reactions, thermodynamics, and kinetics. It also describes several categories of gasification processes and provides details on key moving bed, fluidized bed, and entrained bed gasification technologies.
Structural properties of vegetable oil thermosets effect of crosslinkers, mo...吉成 朴
This document discusses structural properties of vegetable oil thermosets and the effect of crosslinkers, modifiers, and oxidative aging. Specifically, it examines tung oil-based biopolymers prepared using different comonomers (styrene, divinylbenzene, methyl ester of tung oil) or a modifier (acrylated epoxidized soybean oil). It analyzes the chemical aging of the fatty acid segments through Fourier transform infrared spectroscopy, dynamic mechanical analysis, positron annihilation lifetime spectroscopy, and thermogravimetric analysis. The results show values for glass transition temperature, storage moduli, tanδ, and free nanohole volumes change over one year of aging at room temperature and
Soot production and particle size distribution from in situ burning of crude ...Vasilis Vasou
ABSTRACT:
In situ burning has proven to be an effective response for oil spills in Arctic conditions. However the incomplete combustion of oil, due to an incomplete chemical reaction between the fuel and oxygen, lead to the production of solid and gaseous products, such as particulate matter (soot), polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs). Several studies have suggested a link between the presence of these compounds and several diseases; of high concern are the particles smaller than 10 μm (PM10) that can penetrate deep in the lungs, hence the importance to understand the key parameters affecting particulate production and size. The aim of this study was to evaluate the influence of oil viscosity, pool size
diameter and the presence of ice on the production of soot and size of the particles emitted. Two oils were used: DUC and REBCO, with a viscosity of 5 cP and 16 cP respectively. The scale effect was studied on two pools with diameters of 15 and 26 cm. The analysis was divided in three phases: a first outdoor phase performed in Greenland, where in situ burning experiments were performed using both oils and pools, in fresh and salt water and with the presence of ice. The smoke was collected on 2 μm pore size filters and later analysed. The same experiments were later performed in indoor conditions and the concentration of carbon monoxide was measured using optical analysis. In the last phase, the soot collected on the filters was observed with the help of the
scanning electron microscope (SEM). A positive correlation between the pool size and the amount of soot produced was observed, connected with a peak in carbon monoxide production during the vigorous burning phase, while viscosities has shown different behaviour depending on the pool size. The particles size seems to be independent of both the viscosity and the pool diameter. However the presence of PM10 was observed during combustion in ice affected water.
This document provides an overview of petroleum refinery engineering. It discusses the origin and composition of crude oil, refinery processes like distillation, cracking and reforming, and auxiliary operations. It also lists recommended books and introduces concepts like crude oil properties, hydrocarbon groups, non-hydrocarbon compounds, origin of hydrocarbons, exploration techniques, and physical properties of crude oil.
Physical and chemical properties of petroleumkhurasani
Petroleum is a naturally occurring liquid found beneath the Earth's surface that is refined into fuels. It consists mainly of hydrocarbons like alkanes, naphthenes, and aromatics. Petroleum forms from the thermal maturation of buried organic matter over millions of years. It varies in composition but is largely made up of carbon and hydrogen, with other elements like sulfur, oxygen, and nitrogen present in smaller amounts. The type of petroleum depends on factors like the organic material it formed from and temperature/pressure conditions during formation.
This document summarizes a study investigating ultra-deep adsorptive desulfurization of diesel fuel over supported TiO2−CeO2 adsorbents. Key findings include:
1) Light irradiation of diesel fuel prior to adsorption treatment resulted in a 30-fold increase in desulfurization capacity compared to untreated fuel, achieving sulfur removal to below 1 ppmw.
2) Sulfur K-edge XANES analysis identified sulfones as the primary sulfur species on spent adsorbents, suggesting light irradiation chemically transforms original sulfur compounds.
3) Adsorption selectivity tests showed higher removal of indole and sulfones compared to thiophenes and poly
The document provides instructions for experiments to qualitatively analyze unknown samples of carbohydrates. It includes the theory, procedures, observations, and conclusions for tests to identify monosaccharides, disaccharides, and polysaccharides. Students are asked to perform a series of chemical tests on provided carbohydrate samples and unknowns to determine their identities based on color changes and precipitate formations.
Visible light assisted photocatalytic reduction of CO2 using a graphene oxide...Pawan Kumar
A new heteroleptic ruthenium complex containing 2-thiophenyl benzimidazole ligands was synthesized
using a microwave technique and was immobilized to graphene oxide via covalent attachment. The synthesized
catalyst was used for the photoreduction of carbon dioxide under visible light irradiation without
using a sacrificial agent, which gave 2050 μmol g−1 cat methanol after 24 h of irradiation
Visible light assisted photocatalytic reduction of CO2 using a graphene oxide...Pawan Kumar
A new heteroleptic ruthenium complex containing 2-thiophenyl benzimidazole ligands was synthesized
using a microwave technique and was immobilized to graphene oxide via covalent attachment. The synthesized
catalyst was used for the photoreduction of carbon dioxide under visible light irradiation without
using a sacrificial agent, which gave 2050 μmol g−1 cat methanol after 24 h of irradiation
Organic chemistry revision notes cover the formation of fossil fuels like oil from dead marine organisms under heat and pressure. Crude oil is separated into fractions like gasoline and kerosene through fractional distillation, and combustion produces pollution like carbon monoxide and nitrogen oxides. The energy released during combustion can be measured using a calorimeter. Homologous series are families of compounds with the same functional group and general formula that differ by CH2. Main series include alkanes, alkenes, and alcohols, which are named based on their carbon chain and functional group.
This study investigated the polymerization of lactic acid as a model for prebiotic peptide formation via ester-amide exchange. Lactic acid was polymerized in a closed system at 85°C over various time points. HPLC and 1H-NMR were used to analyze the polymers and determine degree of polymerization (DP) and total lactic acid units. DP was found to increase with time while total units decreased, showing polymer regeneration. Methods showed consistent results within 10-15% error. Further studies will compare kinetics to a computer simulation to determine rate constants and model polymerization from various monomers.
Phase transfer catalysis involves using a catalyst to transfer a reactant from one immiscible liquid phase to another where the reaction takes place. Common phase transfer catalysts are quaternary ammonium and phosphonium salts. The catalyst forms an ion pair with the reactant anion, transporting it into the organic phase where it undergoes nucleophilic substitution or other reactions. Phase transfer catalysis allows reactions between ions and organic molecules that would otherwise not interact due to being in separate phases. It has many applications in organic synthesis and pharmaceutical manufacturing.
The document describes Ishmael Masesane's research journey from classical chemistry to transfer hydrogenation of alkenes using palladium catalysis and various organic acids. It then discusses the development of enantioselective versions of this reaction using chiral organic acids like mandelic acid and tartaric acid. Finally, it outlines Masesane's approaches to synthesizing cyclic beta-amino acid derivatives using Diels-Alder reactions of furan with acrylates or maleic anhydride to form oxanorbornyl intermediates.
Synthesis of Oxygenated Fuel Additives via Acetylation of Bio-Glycerol over H...DanesBlake
Abstract
Growing global biodiesel production demands valorization of bio-glycerol derived from biodiesel, which is crucial to make biorefinery process economical. Hence, a series of H2SO4 modified sulfonated Montmorillonite K10 catalysts were synthesized, characterized, and evaluated for acetylation of bio- glycerol with acetic acid to produce mono acetin (MAG), di acetin (DAG), tri acetin (TAG), and di-glycerol tri-acetate (DGTA), which are the oxygenated fuel additives and facilitate the economic viability of biodiesel production so the biorefinery. The synthesized catalysts were characterized by a compressive suite of characterization techniques such as powder X-ray diffraction (XRD), low temperature N2 physisorption, temperature-programmed ammonia desorption (TPAD), and Fourier transform infrared (FTIR). The glycerol conversion and product distribution results were found to correlate with the acidity and textural properties of the catalyst. 20% (w/w) SO4/K10 was revealed to be a promising catalyst for glycerol acetylation with 99% glycerol conversion and with respective yield towards MAG, DAG, TGA and DGTA of 23%, 59%, 15%, and 2%. Moreover, 20% (w/w) SO4/K10 catalyst
was found to maintain the stable catalytic activity for three reaction cycles. However, the partial catalyst deactivation was observed after third reaction cycle, partly due to deposition of coke and loss of active sites during the reaction. https://crimsonpublishers.com/pps/fulltext/PPS.000501.php
Synthesis of Oxygenated Fuel Additives via Acetylation of Bio-Glycerol over H...crimsonpublisherspps
1) The document discusses the acetylation of glycerol, a byproduct of biodiesel production, using sulfonated montmorillonite K10 catalysts.
2) A series of H2SO4-modified sulfonated montmorillonite K10 catalysts were synthesized and characterized. They were then evaluated for catalyzing the acetylation of glycerol with acetic acid to produce oxygenated fuel additives.
3) The 20% (w/w) SO4/K10 catalyst achieved 99% glycerol conversion and respective yields of 23% for MAG, 59% for DAG, 15% for TAG, and 2% for DGTA. This catalyst also maintained
Biomass to olefins cracking of renewable naphthapxguru
This document discusses cracking renewable naphtha produced from biomass to produce light olefins like ethylene and propylene. The biomass is first converted to a renewable naphtha fraction using a two-step process involving hydrodeoxygenation and hydrocracking. Comprehensive characterization of the renewable naphtha showed it consists mainly of paraffins suitable for steam cracking. Steam cracking this naphtha in a pilot plant yielded high amounts of ethylene (31 wt%) and propylene (17.5 wt%) while producing small amounts of byproducts. Experimental coking studies also showed this naphtha feed has attractive coking properties. Simulations predict higher run lengths compared to fossil n
Meulepas, 2010, Biotechnological Aspects Of Sulfate Reduction With Methane As...roelmeulepas
This review paper discusses the biotechnological aspects of using methane as an electron donor for sulfate reduction. Sulfate reduction is an important process in the carbon and sulfur cycles in nature. It can be used to remove and recover oxidized sulfur compounds from waste streams. Traditionally, hydrogen and ethanol are used as electron donors but methane would be more attractive due to lower costs. The paper reviews the microbial pathways and thermodynamics of sulfate reduction with methane, as well studies using bioreactors. Further research is needed to improve the extremely low growth rates of the responsible microorganisms to enable practical applications.
Crude oil is a complex mixture of hydrocarbons that are separated into useful fractions via fractional distillation. It is formed from the remains of ancient microorganisms and plants that were deposited under intense heat and pressure over millions of years. The key fractions obtained include liquid petroleum gas, gasoline, kerosene, diesel, and fuel oils of varying viscosity. When burned as fuels, the hydrocarbon molecules in crude oil and its fractions react with oxygen to produce carbon dioxide, water vapor, and other emissions.
This document describes the synthesis and characterization of a manganese(III) complex intended to mimic the active site of superoxide dismutase (SOD) enzymes. A tetradentate ligand containing two quinoline groups (DQEA) was synthesized and characterized using NMR and IR spectroscopy. This ligand was then reacted with manganese(III) acetate to form the Mn(III) complex. The ability of this complex to catalyze the dismutation of superoxide, mimicking SOD activity, was confirmed using the Fridovich assay. Overall, the goal was to develop a low molecular weight SOD mimic that could function as a potential pharmaceutical for reducing oxidative stress.
Physical and Chemical Properties of HydricarbonsMasoom Shani
The document discusses the physical and chemical properties of petroleum. It defines various types of hydrocarbons such as oil, natural gas, condensates, and their classification. It describes the composition of natural gas and crude oil. It also discusses the key terms used in petroleum geology such as source rock, reservoir rock, seal rock, and the refining process.
Petroleum, also known as crude oil, is a naturally occurring liquid found beneath the Earth's surface. It is composed primarily of hydrocarbons such as carbon and hydrogen. Crude oil is extracted from the ground through oil wells, either because it flows naturally due to underground pressures or through mechanical pumping. There are several theories for the origin of petroleum, but the modern theory is that it formed from the decomposition of marine organisms and terrestrial plant material over millions of years. Once extracted, crude oil undergoes processing to remove impurities and separate it into useful petroleum products through distillation. These products include fuels like gasoline, diesel and jet fuel, as well as other commodities like lubricating oils, asphalt and
This document summarizes a study that analyzed model petroleum compounds using high-resolution mass spectrometry with atmospheric pressure photoionization (APPI), atmospheric pressure chemical ionization (APCI), and electrospray ionization (ESI) in order to better understand the ionization efficiency of different compound classes. The study found that APPI was able to ionize the widest range of compounds, including two-ring PAHs, oxygenated PAHs, and anhydrides. APCI and ESI were more limited in the compounds they could ionize. Factors like size, structure, functional groups, heteroatom content, and methylation level affected ionization efficiency across the sources. Alkanes could not be ion
This document provides an overview of coal gasification. It discusses the purposes and benefits of converting coal to gas. Integrated coal gasification combined cycle is highlighted as an important application due to its high efficiency and potential to meet emission standards. The document outlines coal gasification reactions, thermodynamics, and kinetics. It also describes several categories of gasification processes and provides details on key moving bed, fluidized bed, and entrained bed gasification technologies.
Structural properties of vegetable oil thermosets effect of crosslinkers, mo...吉成 朴
This document discusses structural properties of vegetable oil thermosets and the effect of crosslinkers, modifiers, and oxidative aging. Specifically, it examines tung oil-based biopolymers prepared using different comonomers (styrene, divinylbenzene, methyl ester of tung oil) or a modifier (acrylated epoxidized soybean oil). It analyzes the chemical aging of the fatty acid segments through Fourier transform infrared spectroscopy, dynamic mechanical analysis, positron annihilation lifetime spectroscopy, and thermogravimetric analysis. The results show values for glass transition temperature, storage moduli, tanδ, and free nanohole volumes change over one year of aging at room temperature and
Soot production and particle size distribution from in situ burning of crude ...Vasilis Vasou
ABSTRACT:
In situ burning has proven to be an effective response for oil spills in Arctic conditions. However the incomplete combustion of oil, due to an incomplete chemical reaction between the fuel and oxygen, lead to the production of solid and gaseous products, such as particulate matter (soot), polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs). Several studies have suggested a link between the presence of these compounds and several diseases; of high concern are the particles smaller than 10 μm (PM10) that can penetrate deep in the lungs, hence the importance to understand the key parameters affecting particulate production and size. The aim of this study was to evaluate the influence of oil viscosity, pool size
diameter and the presence of ice on the production of soot and size of the particles emitted. Two oils were used: DUC and REBCO, with a viscosity of 5 cP and 16 cP respectively. The scale effect was studied on two pools with diameters of 15 and 26 cm. The analysis was divided in three phases: a first outdoor phase performed in Greenland, where in situ burning experiments were performed using both oils and pools, in fresh and salt water and with the presence of ice. The smoke was collected on 2 μm pore size filters and later analysed. The same experiments were later performed in indoor conditions and the concentration of carbon monoxide was measured using optical analysis. In the last phase, the soot collected on the filters was observed with the help of the
scanning electron microscope (SEM). A positive correlation between the pool size and the amount of soot produced was observed, connected with a peak in carbon monoxide production during the vigorous burning phase, while viscosities has shown different behaviour depending on the pool size. The particles size seems to be independent of both the viscosity and the pool diameter. However the presence of PM10 was observed during combustion in ice affected water.
Petroleum geology relates to the origin, migration, and accumulation of oil and gas. Key points in the document include:
- Early discoveries were near oil seeps at the surface. The anticline theory proposed that oil would accumulate in structural folds.
- Subsurface geology studies helped trace lateral changes in rock layers. Geophysics tools like seismography and gravity measurements aided exploration.
- Modern methods include direct hydrocarbon detection, which identifies gas reservoirs as bright spots on seismic data, and seismic stratigraphy for tracing facies.
The document discusses the origin, composition, and types of organic matter found in sediments and rocks. It describes how organic matter originates from organisms and is preserved in anoxic environments. The main types of organic matter discussed are kerogen and bitumen. Kerogen makes up the majority of sedimentary organic matter and has varying potential to generate hydrocarbons upon heating. Bitumen represents the soluble fraction and includes compounds such as asphaltenes and maltens. The document also introduces different types of kerogen that vary in their composition and hydrocarbon generating ability.
This document discusses the environmental impacts of the oil industry and proposes control measures. It notes that while oil provides economic benefits, the extraction, refining, and combustion processes release various effluents that harm the environment. Effluents from drilling mud, gaseous emissions, and oil spills are toxic and increase pollution. This leads to issues like global warming, ocean acidification, and acid rain. The document proposes ways to reduce effluents, such as using biodegradable drilling fluids, emissions controls, carbon sequestration, and oil spill cleanup methods. Overall it argues that industries must follow regulations while greater research into mitigation is also needed to protect the environment.
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.
USE OF MICROBES IN MINERAL BENEFICIATION AND OIL RECOVERY AEsam Yahya
The document discusses microbial enhanced oil recovery (MEOR) techniques. It describes four main MEOR mechanisms: 1) reduction of oil-water interfacial tension through surfactant production, 2) selective plugging of high permeability zones by microbial biomass, 3) reduction of oil viscosity, and 4) permeability increase through production of acids. The document also outlines various microbial products involved in MEOR, including biosurfactants, biopolymers, bio solvents, acids, and bio gases.
This document provides a comprehensive review of foam-enhanced oil recovery (foam-EOR) techniques. It discusses the problems with conventional gas-EOR methods, such as gravity override and poor sweep efficiency. Foam-EOR aims to improve sweep efficiency by generating foam to restrict gas mobility and create a uniform displacement front. The review covers foam characterization, factors impacting foam stability and oil recovery, and mechanisms of foam generation. It analyzes laboratory and field implementations of foam-EOR and highlights recent developments to improve foam generation and stability under reservoir conditions.
Synthesis and characterization of antioxidant resin modified Alexander Decker
This document summarizes the synthesis and characterization of antioxidant resins modified from bisphenol A and formaldehyde. Bisphenol A was condensed with formaldehyde to form a methylolic resin (Resin I) which was then converted to alkoxy derivatives (Resins II, III, IV). The resins were characterized using techniques like IR spectroscopy, NMR, elemental analysis and thermogravimetric analysis. The resins showed good thermal stability and low volatility. When added to lubricating oil at concentrations up to 0.5%, Resins II, III and IV significantly improved the oxidation stability of the oil as measured by reduced acidity, carbonyl index and viscosity change over 12 hours of oxidation testing compared to oil
Monitoring and interpreting of insitu combustionGowtham Dada
This document discusses using carbon isotope analysis to monitor and interpret in situ combustion processes. It provides background on in situ combustion, carbon isotopes, and carbon isotope analysis. Different carbon isotope values are expected from various combustion reactions. Field data and combustion tube experiments can be interpreted using carbon isotope signatures to understand the temperature of reactions and identify communication between injectors and producers. Carbon isotope analysis is a useful tool when combined with gas analysis to distinguish reaction sources and burning characteristics during in situ combustion.
COD reduction of aromatic polluted waste water by Advanced Oxidation Process ...Wade Bitaraf
In most petrochemical complexes and oil refineries the wastewater contains the aromatic compounds among which Benzene, Toluene, Ethyl Benzene and Xylene (BTEX) have harmful effects on environment and human health. The present work mainly deals with the UV-based advanced oxidation processes (AOPs), UV/H2O2 were tested in batch reactor systems to evaluate the removal efficiencies and optimal conditions for the photodegradation of BTEX in order to wastewater treatment. The efficiency of this method was analyzed by evaluating the Chemical Oxygen Demand (COD) as a pollution criterion through the COD reactor. The influence of the basic operational parameters such as initial concentration of H2O2, pH, Temperature, irradiation time and UV amount on the photo degradation of BTEX were also studied. The oxidation rate of BTEX and respectively the reduction rate of COD were low when the oxidation was carried out in the absence of H2O2 or UV light. The addition of proper amount of hydrogen peroxide improved the degradation, while the excess hydrogen peroxide could quench the formation of hydroxyl radicals (•OH). The optimal conditions of suspended slurry with 1.11(g/l) initial concentration of H2O2 and pH value of 3.1 were obtained under three UV lights illumination (6 W). Under the optimal conditions, COD reduction during the initial period of 180 min in UV/H2O2 systems reached about 90%.
Cosolvent Transesterification of Jatropha Curcas Seed OilZX7
This document presents a study on the cosolvent transesterification of Jatropha curcas seed oil. The key findings are:
1) Jatropha oil was characterized and found to contain mainly palmitic, oleic, linoleic and stearic acids.
2) Tetrahydrofuran was used as the cosolvent to create a single miscible phase for the transesterification reaction between Jatropha oil and methanol.
3) Optimum conditions for transesterification were found to be 40°C, 200 rpm, 4:1 methanol-to-oil ratio, 1:1 cosolvent-to-methanol ratio, 0.5
This document provides an overview of methanol production and applications. It discusses the history of methanol production beginning with wood distillation in the 1660s. Major developments include the BASF process in 1923, which was the dominant industrial production method for over 45 years. Currently, about 90% of methanol is produced from natural gas via steam reforming or autothermal reforming to produce synthesis gas, which is then converted to crude methanol and distilled for purification. The chapter examines methanol production from various feedstocks and its various applications as a fuel, chemical building block, and more.
Activation of Spent Bleaching Earth for Dehumidification Application World-Academic Journal
This document summarizes research on activating spent bleaching earth (SBE) for use in dehumidification applications. The researchers conducted experiments to regenerate SBE through three steps: 1) solvent extraction with hexane to remove entrained oil, extracting up to 25% of oil; 2) oxidation with hydrogen peroxide to remove remaining carbonaceous materials; and 3) heat reactivation at 550°C to remove hydrocarbons and open clay adsorption sites. Batch experiments tested the regenerated SBE and found sorption capacities of 27.07-26.63% at activation temperatures of 550-650°C, higher than commercial clay desiccants. The regenerated SBE shows potential as a low-
The document describes a new methodology for desalination of heavy crude oils. It involves using a developed desalting apparatus to wash crude oil samples with deionized water and demulsifiers at 60°C with continuous stirring. This removes over 99% of salt content. Key parameters like total sulfur, acid number and conductivity are monitored before and after the desalination process to evaluate changes in oil quality. The new method reduces these parameters by around 30% and is faster than standard methods, taking about 80 minutes for four wash cycles to effectively desalt heavy crude oils.
Determination of vanadium, nickel, copper and iron as complexes of bis acetyl...Alexander Decker
This document describes a study that used high performance liquid chromatography (HPLC) to determine the concentrations of vanadium, nickel, copper, and iron in Nigerian crude oil samples. The researchers analyzed samples from 5 oil wells, both onshore and offshore. They found that nickel generally had the highest concentration, while copper had the lowest. Concentration levels ranged from 210-1620 ppb for nickel, 975-1125 ppb for iron, 225-1060 ppb for vanadium, and 54-138 ppb for copper. The results were consistent with previous studies on metals in Nigerian crude oils. The study provides data on heavy metal concentrations that can help assess the environmental and economic impacts of Nigerian crude
Righi et al_climate_impact_of_biofuels_in_shipping-global_model_studies_og_th...www.thiiink.com
ABSTRACT: Aerosol emissions from international shipping
are recognized to have a large impact on the Earth’s radiation
budget, directly by scattering and absorbing solar radiation and
indirectly by altering cloud properties. New regulations have
recently been approved by the International Maritime Organi-
zation (IMO) aiming at progressive reductions of the maximum
sulfur content allowed in marine fuels from current 4.5% by
mass down to 0.5% in 2020, with more restrictive limits already
applied in some coastal regions. In this context, we use a global
bottom-up algorithm to calculate geographically resolved emis-
sion inventories of gaseous (NOx, CO, SO2) and aerosol (black
carbon, organic matter, sulfate) species for different kinds of
low-sulfur fuels in shipping. We apply these inventories to study the resulting changes in radiative forcing, attributed to particles from shipping, with the global aerosol-climate model EMAC-MADE. The emission factors for the different fuels are based on measurements at a test bed of a large diesel engine. We consider both fossil fuel (marine gas oil) and biofuels (palm and soy bean oil) as a substitute for heavy fuel oil in the current (2006) fleet and compare their climate impact to that resulting from heavy fuel oil use. Our simulations suggest that ship-induced surface level concentrations of sulfate aerosol are strongly reduced, up to about 40-60% in the high-traffic regions. This clearly has positive consequences for pollution reduction in the vicinity of major harbors. Additionally, such reductions in the aerosol loading lead to a decrease of a factor of 3-4 in the indirect global aerosol effect induced by emissions from international shipping.
Biodiesel production via transesterification of palm oilKátia Gabriel
The document summarizes research into producing biodiesel via transesterification of palm oil using sodium hydroxide loaded onto alumina (NaOH/Al2O3) catalysts. NaOH/Al2O3 catalysts were prepared by impregnating alumina with sodium hydroxide solutions then calcining. The catalysts were characterized and found to have basic sites suitable for transesterification. Parameters like methanol to oil ratio, catalyst amount, temperature and time were varied to determine optimum conditions. With the optimum conditions, a 99% conversion of palm oil to biodiesel was achieved.
This document summarizes a study that characterized the producer gas from an open top downdraft gasifier. The study compared different approaches for analyzing tar in the gas, including GC-MS and gravimetric methods. GC-MS analysis found that tar mainly consisted of light aromatic compounds like benzene and toluene. Gravimetric tar measurements were around one order of magnitude lower than total tar detected by GC-MS. The study also found similar gravimetric tar contents when operating the gasifier with different biomass feedstocks, and that the open top reactor design resulted in low tar contents of 50-80 mg N m-3 in the raw gas.
2. 1. Introduction
In a society that is highly dependent on energy derived from petro-
leum, constant crude oil extraction and transportation lead to virtually
unavoidable releases into the environment (Wang et al., 2013). On
April 20, 2010, a turbulent mixture of gas and a light, sweet (Macondo
type) crude oil was released into the Gulf of Mexico as a result of the
Deepwater Horizon (DWH) drilling rig incident in the Mississippi Canyon
Block 252 (MC252) (Camilli et al., 2012; McNutt et al., 2012; Aeppli
et al., 2012). In the days following the accident, some of the escaped
Macondo oil rose 1500 m to the surface of the ocean, creating oil slicks
some of which ultimately reached the coast (Liu et al., 2012). In the
event of crude oil discharges into marine environments, weathering
processes such as dissolution, dispersion, emulsification, evaporation,
biodegradation, and photo-oxidation (Wang et al., 2013; Aeppli et al.,
2012) constantly modify the oil composition (Wang et al., 2013;
Jordan and Payne, 1980). Weathering, thus, adds compositional com-
plexity to what is already one of the most complex natural mixtures
known to mankind (Hsu et al., 2011). The thousands of compounds
present in crude oil can be divided into four main classes: saturated hy-
drocarbons (straight, branched, and cyclic alkanes), aromatic com-
pounds (containing one or more rings), resins (relatively high
molecular weight and polar compounds, which are soluble in the oil,
and contain heteroatoms such as nitrogen, sulfur, and oxygen), and
asphaltenes (highest molecular weight and most polar compounds,
also containing heteroatoms such as nitrogen, oxygen and sulfur but un-
like resins insoluble in the oil) (Garrett et al., 1998; Speight, 2004).
These different compound types are affected differently by oil
weathering as each of the weathering processes is selective towards
specific compounds. For example, evaporation and emulsification de-
plete the oil of its volatile compounds, while water washing removes
water-soluble compounds (Mansuy et al., 1997), and biodegradation af-
fects primarily n-alkanes followed by branched and cyclic hydrocar-
bons, closely followed by naphthenic compounds (Wang et al., 2013).
Photo-oxidation has been shown to primarily modify select polycyclic
aromatic hydrocarbons (PAHs), and in addition to other oxidation
mechanisms (including biodegradation) to be responsible for the in-
crease of the oxygen content in the remaining oil (McKenna et al.,
2013; Prince et al., 2003). Since several constituents in crude oil have
been associated with some degree of toxicity, the characterization of
fresh and especially of the modified weathered crude oil is crucial in
order to understand the potential environmental effects.
Conventional oil characterization by gas chromatography flame
ionization detection (GC–FID), or gas chromatography mass spectrom-
etry (GC–MS) (Maki et al., 2001), has been able to elucidate weathering
related compositional changes of hydrocarbons and PAHs. However,
coelution and the inability to analyze polar, nonvolatile, or thermally
unstable compounds (Wang et al., 2013; Garrett et al., 1998; McKenna
et al., 2013; Burns, 1993; Charrie-Duhaut et al., 2000), limit the amount
and type of analytes that can be detected (McKenna et al., 2013). Conse-
quently, both techniques tend to overlook the analysis of oxygenated
hydrocarbons (Aeppli et al., 2012), which is particularly problematic
for weathered oil that has a lower amount of low-boiling and non-
polar compounds that are GC amenable, and has a higher amount of
high-boiling and polar compounds (Aeppli et al., 2012). The character-
istic oil “hump” or unresolved complex mixture (UCM), which is a
raised baseline due to the coelution of numerous compounds and is ob-
served in GC analysis and is most prominent in weathered oils, is an in-
dication of the limitations of these previously described techniques
(Gough and Rowland, 1990). In order to resolve a larger fraction of
the components present in oil, more advanced techniques need to be
used, such as two-dimensional gas chromatography mass spectrometry
(GC×GC–MS) or Fourier transform mass spectrometry (FT–MS).
GC×GC–MS somewhat expands the accessible analytical window and
allows for isomer differentiation (McKenna et al., 2013); however, it is
still limited to volatile compounds that are GC amenable (up to C45).
FT–MS, on the other hand, provides the possibility to extend this
range up to C100 (McKenna et al., 2013), and to analyze nonvolatile
and/or highly polar compounds (Qian et al., 2001a, 2001b; Mapolelo
et al., 2009). Moreover, FT–MS analysis provides ultrahigh-resolution
(Kaiser et al., 2011; Podgorski et al., 2013), and mass accuracy of less
than 1 ppm (with internal calibration) (Savory et al., 2011), which
leads to the possibility of assigning elemental compositions (Rodgers
et al., 2005). The ability to couple several different ionization techniques
to FT-MS is also crucial in the analysis of complex and diversified mix-
tures such as crude oil. Common sources that have been used are
electrospray ionization (ESI) and atmospheric pressure photo ionization
(APPI) (McKenna et al., 2013), but others such as atmospheric pressure
chemical ionization (APCI) (Roussis and Fedora, 2002), and atmospher-
ic pressure laser ionization (APLI) (Schrader et al., 2008) have also been
employed. APPI is particularly useful to characterize nonpolar or slightly
polar species, while ESI offers the advantage of accessing more polar
species while avoiding interferences of the hydrocarbon matrix. As a re-
sult, comprehensive characterizations of weathered oils must be
achieved by a combination of multiple techniques, aimed at accessing
the maximum possible number of compounds.
A big portion of the previous studies on the Macondo oil released
during the DWH accident have focused mainly on common analytes
that are GC amenable, such as PAHs, alkanes, and hopane and sterane
biomarkers (Aeppli et al., 2012; McKenna et al., 2013). Unsurprisingly,
reports have shown that, with increased weathering, the oil was deplet-
ed of most of its saturated and aromatic compounds (Aeppli et al., 2012;
Atlas and Hazen, 2011; Carmichael et al., 2012; Kostka et al., 2011; Lima
et al., 2005; Liu et al., 2012). However, McKenna et al. (2013) estimated
that in surface slicks only about 40% of the total mass of hydrocarbons
could be analyzed by conventional GC-based techniques, while Reddy
et al. (2012) estimated that for weathered Macondo oil traditional
analytes only account for less than 25% of the oil mass. Moreover, an
increase in oxygenated hydrocarbons with a concurrent decrease in
saturated hydrocarbons and aromatics was reported in weathered oil
deposited at the shoreline (Aeppli et al., 2012). Hall et al. (2013) further
predicted by GC×GC–MS analysis that this oxygenated fraction is large-
ly due to the oxidation of saturates, which has only recently been shown
to be a significant process during oil weathering (Hall et al., 2013). FT-
ICR analysis of oiled sands has shown a similar trend, more specifically
detecting the possible formation of carboxylic acids, ketones, and alco-
hols (Ruddy et al., 2014), all being consistent with photo-oxidation
and biodegradation transformation products. However, a significant
portion of the currently available knowledge originates from GC×GC–
MS analysis, and thus only applies to a limited amount of compounds.
Data currently available from ultrahigh-resolution mass spectrometry
(UHRMS) is limited, which evidences a strong need to expand the
knowledge on weathering products of the Macondo crude oil by FT–
MS techniques. This study, therefore, aims to characterize and identify
compositional changes that occurred in a weathering series (fresh
crude oil, two distinct oil slicks, and a beached oil mat) of the Macondo
crude oil. UHRMS coupled with APPI and ESI in both positive and nega-
tive ionization mode are used in order to expand the range and type of
compounds that can be detected.
2. Materials and methods
2.1. Samples and preparation
Four different field-collected oils were characterized in this study.
The unweathered Macondo oil (denoted as Massachusetts oil from
hereon) was collected by a production vessel on August 15, 2010 direct-
ly at the MC-252 wellhead, and transferred to the Massachusetts oil
barge. Two weathered oils originating from two distinct surface slicks
were skimmed from the Gulf of Mexico, and were collected by the
USCG Cutter Juniper and Barge No. CTC02404 on July 19, 2010 and
July 29, 2010, respectively (referred to as Juniper and CTC oil from
601A.K. Huba, P.R. Gardinali / Science of the Total Environment 563–564 (2016) 600–610
3. now on). The last oil was buried in the shoreline of Elmer's Island (Lou-
isiana), was exposed after hurricane Isaac, and was subsequently col-
lected in August 2012 (denoted as Elmer's Island mat from hereon). A
20,000 ppm oil stock solution was then created for the four oils by dis-
solving approximately 1 g of crude oil in 50 mL of methylene chloride.
The stock solutions were then diluted twofold to a final concentration
of 10,000 ppm for GC–FID and GC–MS analyses. GC–MS samples were
spiked with 100 μL of a PAH surrogate standard mixture (naphtha-
lene-d8, acenaphtene-d10, phenanthrene-d10, and perylene-d12), as
well as 100 μL of a PAH internal standard mixture (fluorene-d10 and
benzo(a)pyrene-d12). GC–FID samples, on the other hand, were spiked
with 100 μL of an aliphatic surrogate (n-dodecane-d26, n-eicosane-d42,
n-triacontane-d62, p-terphenyl-d14) as well as 100 μL of an aliphatic in-
ternal standard (5α androstane and n-hexadecane-d34). For UHRMS
analysis 50 μL of oil stock was left to air dry, and was subsequently
reconstituted into 50:50 toluene/methanol to a final concentration of
2500, 5000, 5000, and 10,000 ppm for Massachusetts, CTC, Juniper,
and Elmer's Island mat, respectively. The final solutions were spiked
with 1% formic acid, and 1% ammonium hydroxide for positive and neg-
ative ionization mode, respectively. An internal standard (tetradecanoic
14,14,14-d3 acid, 11.6 ppm) was added to all UHRMS samples. For
the model compound study, Elmer's Island mat was spiked with
ten standards covering a range of functional group types: phenol, 2-
ethylphenol, 4-isopropylphenol, coprostane, coprostan-3-one, choles-
terol, tetradecanoic 14,14,14,-d3 acid (all at approximately 10 ppm),
coprostan-3-ol (1 ppm), tetracosanol (2 ppm), and tetracosanoic acid
(5 ppm). All the solvents used were Optima LC/MS grade and were pur-
chased from Fisher Scientific (Fair Lawn, NJ, USA).
2.2. GC–FID analysis
GC–FID analysis was carried out on a Thermo Trace 1310 GC-FID, fitted
with an Rxi®-5Sil fused silica capillary column (30 m × 0.25 mm ×
0.25 μm). A sample volume of 2 μL was injected (in splitless mode) into
the instrument. The inlet temperature was held at 325 °C, and the carrier
gas was set at a constant flow rate of 2.4 mL/min. The starting oven tem-
perature was 40 °C, followed by an initial 7.5 °C/min ramp to 215 °C, and a
second 10 °C/min ramp to 320 °C, and then a final hold of 13 min.
2.3. GC–MS analysis
GC–MS analysis was carried out in electron impact mode (70eV) on
a Thermo Finnigan Ultra trace TSQ Quantum XLC GC–MS operated in
selected ion monitoring (SIM) mode. The GC–MS was fitted with an
Rxi®-5Sil fused silica capillary column (30 m × 0.25 mm × 0.25 μm),
and helium was used as the carrier gas and set at a constant flow of
1.7 mL/min. A sample volume of 2 μL was introduced (in splitless
mode) into the injector which was held at 300 °C. The initial oven tem-
perature was 40 °C, followed by a 7.5 °C/min ramp to 295 °C, and an
eight minute hold.
2.4. Ultrahigh-resolution mass spectrometric analysis
Analysis was carried out on a Q Exactive Orbitrap (Thermo Scientific,
NJ, USA) by direct infusion through a 500 μL syringe (Thermo Scientific,
NJ, USA) at a typical flow rate of 30 μL/min. In addition to the acquisition
of the sample, each infusion data file contained acquisitions of a mobile
phase background, and a solvent background. Data were acquired in full
scan mode over a mass range of 80–1200 m/z, and the instrument was
operated at a resolution of 140,000 FWHM. The automatic gain control
(AGC) target was set to 1 × e6
, while the maximum injection time was
set to 50 ms. External mass calibration provided a mass accuracy of
5 ppm. The APPI ionization source (Thermo Scientific, NJ, USA) was
equipped with a krypton UV gas discharge lamp (Syagen Technology,
Inc, Tustin, CA) that produces 10–10.2 eV photons (120 nm). N2 sheath
gas at 40 psi was used to facilitate the ionization, while the auxiliary
Fig. 1. GC–FID chromatograms of the weathering series (Mass, CTC, Juniper, and Elmer's Island mat), highlighting the decrease of overall signal, as well as the disappearance of low
molecular weight compounds and the formation of the UCM.
602 A.K. Huba, P.R. Gardinali / Science of the Total Environment 563–564 (2016) 600–610
4. port remained closed. The heated vaporizer region was held at 350 °C,
while the capillary temperature was set to 300 °C, for both positive
and negative mode. For the ESI analysis a heated electrospray (HESI)
source (Thermo Scientific, NJ, USA) was used, and typical conditions
for positive mode were a spray voltage of 5.20 V, a heated vaporizer re-
gion at 300 °C, capillary temperature of 300 °C, and sheath and auxiliary
gas at 40 and 5 psi, respectively. For negative mode, the typical condi-
tions were a spray voltage of 4.50 V, a heated vaporizer region at
300 °C, capillary temperature of 200 °C, and sheath and auxiliary gas
at 35 and 30 psi, respectively.
2.4.1. Data analysis
Mass spectra were obtained by averaging a selected range of consec-
utively acquired infusion spectra. A background spectrum acquired in
the same infusion run as the sample was subtracted to account for ex-
ternal contamination. Data processing was performed by using the
Composer 1.0.6 software (Sierra Analytics, CA, USA), which relies on
petroleum specific composition assignment algorithms. Criteria used
for peak detection and molecular formula assignments included: a
m/z range of 80–1000 Da, a match tolerance of 5 ppm for formula
assignments, a DBE range from −0.5 to 65, and element ranges of
C ≤ 200, H ≤ 1000, O ≤ 5, N ≤ 4, S ≤ 2. The setting for the minimum relative
peak abundance accepted was sample specific in order to adjust for the
variable nature of the samples.
3. Results and discussion
3.1. GC-FID and GC–MS analysis, and weathering studies
Initially, the characterization of the weathering series was per-
formed by visual inspection of the chromatograms obtained by GC-FID
analysis. The characteristic trend in depletion of volatile compounds
(predominantly alkanes, and to a lesser amount aromatics) for the
weathered oils was observed and is shown in Fig. 1. A clear loss of all
the front-end compounds (which represent the low molecular weight
and thus volatile hydrocarbons and aromatics), and an appearance
and increase of the characteristic oil UCM (which is due to hydrocarbon
species that coelute in chromatographic analysis) is clearly noticeable
when going from Massachusetts to the weathered oils (CTC, Juniper,
and Elmer’s Island mat). The specific order of the oils in the weathering
series is shown by the disappearance of more and more alkanes, and an
overall decrease in signal. Massachusetts is shown to be a relatively
fresh oil, while out of the two surface slick oils Juniper appears to be
more weathered than CTC (which agrees with previous studies on
total PAH depletion(BP, 2014), and the Elmer's Island mat is shown to
be the most weathered. Further characterization studies of the same
oils (shown in Fig. 2) were conducted in order to perform a more in-
depth characterization of the weathering series based on processes
other than dissolution and evaporation. GC–FID and GC–MS analyses
and subsequent quantifications of specific alkanes and PAHs,
Fig. 2. Ratios of the concentrations of chrysene/benz(a)anthracene (top) and n-C18/phytane (bottom) for the weathering series, showing an increase in photodegradation and
biodegradation, respectively. The top ratio was obtained from GC–MS data, while the bottom ratio used GC–FID data.
603A.K. Huba, P.R. Gardinali / Science of the Total Environment 563–564 (2016) 600–610
5. respectively, showed results that reinforce the previously determined
weathering order, showing an increase in both biodegradation as well
as photodegradation going from Massachusetts, to CTC, to Juniper, to
the Elmer's Island mat. Fig. 2 illustrates these results, and shows plots
of two degradation ratios (chrysene/benz(a)anthracene (Plata et al.,
2008; Lemkau et al., 2010; Yim et al., 2011; Behymer and Hites, 1988)
and n-C18/phytane (Lemkau et al., 2010; Yim et al., 2011; Wang et al.,
1995a, 1998)) that have previously been used as good indicators of
crude oil photodegradation and biodegradation, respectively. The ratio
of chrysene/benz(a)anthracene increases for the weathering series,
Fig. 4. (−) APPI spectra of the oil weathering series, with the zoomed in spectra shown on the right emphasizing the shift towards higher molecular weight.
Fig. 3. (−) ESI spectra of the oil weathering series, highlighting the three distinct areas of major changes, and a relative increase of higher molecular weight compounds with weathering.
604 A.K. Huba, P.R. Gardinali / Science of the Total Environment 563–564 (2016) 600–610
6. indicating an increase in photodegradation of the oils. On the other
hand, the n-C18/phytane ratio decreases, which is an indication of
increased biodegradation. This strongly suggests that this is a true
weathering series (going from Massachusetts, to CTC, to Juniper, to
the Elmer's Island mat), and likely includes both photodegradation
and biodegradation, in addition to other weathering processes such as
dissolution and evaporation. An interesting fact that is noticeable is
that, based on the results here obtained, the degree of weathering
does not appear to be strictly time or location dependent, but mainly as-
sociated to the oil’s path and the environmental factors related with
it (such as temperature, nutrients, salinity, pH, sun incidence, and
currents). Having a series of weathered oils is, therefore, essential in
order to achieve a more comprehensive understanding of the dynamic
changes that affect crude oil in a marine environment. This understand-
ing is the fundamental basis to any oil toxicity estimations.
3.2. Ultrahigh-resolution mass spectrometric analysis
Since GC–FID and GC-MS analyses pose significant limitations in a
comprehensive oil characterization, in order to expand the analytical
window of compounds detected, ultrahigh-resolution mass spectro-
metric analysis of the four oils was performed by means of an Orbitrap
Q Exactive instrument. The four oils were analyzed in both (±) ESI as
well as (±) APPI, in order to target a broader range of compounds
(polar and nonpolar). The resulting mass spectra show significant
changes, which can be seen particularly well in the negative mode spec-
tra provided in Figs. 3 and 4. Overall, a common trend independent of
the ionization source or mode, is the relative increase in higher molecu-
lar weight compounds. The (−) ESI spectra shown in Fig. 3, for example,
clearly show this trend as the first section of the spectrum significantly
decreases, while the second section increases with weathering. More-
over, a completely new series of compounds appears in the third section
of the Elmer's Island mat spectrum, which illustrates the additional
compositional complexity of beached oils (that may have incorporated
exogenous materials). Compared to the ESI data shown in Fig. 3, the
(−) APPI data shown in Fig. 4 show less dramatic changes, but also ap-
pear to present a slight shift towards higher molecular weight com-
pounds, which is especially visible in the magnified spectra shown in
the inserts. Furthermore, it can be seen that the APPI spectra appear to
contain a much larger amount of individual masses. This evidences the
more selective nature of the ESI ionization source towards more polar
compounds, as it eliminates the background hydrocarbon interference
that dominates the APPI spectrum. This is a good illustration of how
these two ionization techniques are complementary and how a compre-
hensive crude oil characterization must use a combination of both.
In order to confirm these visually apparent changes, class distribu-
tion plots were created by categorizing all the assigned molecular for-
mulae (CvHwNxOySz) into specific heteroatom classes (O1, O2, NO, NO2,
Fig. 5. Class distributions for (+) APPI (top) and (+) ESI (bottom) for samples of the weathering series (Massachusetts, CTC, Juniper, Elmer's Island mat). Full arrows depict a consistent
trend over the whole weathering series, while dashed arrows depict trends in which the Elmer’s Island mat is an exception. Compounds showing as protonated ions are denoted by the
(H), others are radical ions.
605A.K. Huba, P.R. Gardinali / Science of the Total Environment 563–564 (2016) 600–610
7. etc.), and by plotting the relative abundance of each of these classes.
These graphs are shown in Figs. 5 and 6, and show the presence of
large compositional diversity among the four oils and the two ionization
methods. Fig. 5 depicts the differences between ESI and APPI in positive
ionization mode. The most dominant class detected in (+) APPI is the
hydrocarbon class (protonated molecules are denoted by the (H)).
(+) ESI, on the other hand, is dominated by nitrogen containing com-
pounds, while the hydrocarbon portion is much smaller. Another inter-
esting concept shown in these two plots is that while ESI ionization
requires protonation, APPI provides the possibility to ionize other
species by charge transfer owing to the presence of dopant molecules
(toluene). This creates radical compound classes for the hydrocarbon,
nitrogen, and oxygen classes that become fairly prominent. Fig. 5 also
shows a clear increase in oxygenated species (O1, O2, O3), with a con-
current reduction in hydrocarbons as the weathering degree of the
oils increases. Some of the classes of the Elmer's Island mat are an ex-
ception to this trend, which could be due to the differing nature of
beached oils. The increase in oxidation with weathering that is observed
corroborates data from other studies (Aeppli et al., 2012; Hall et al.,
2013; Ruddy et al., 2014). Negative mode data (shown in Fig. 6) extends
the compositional coverage to highly oxygenated species (O4 and O5).
However, unlike for positive mode where all the oxygenated classes in-
creased with weathering, in negative mode there seems to be a decrease
in lower oxygenated species (O1 for APPI, and O1 and O2 for ESI) with a
concurrent increase in higher oxygenated species (O2–O5 for APPI, and
O3–O5 for ESI).
In order to more clearly depict the changes in hydrocarbons and ox-
ygenated compounds, Kendrick mass defect plots were created
(Kendrick mass = IUPAC mass×(14.00000/14.01565)). Such graphs
plot the Kendrick Mass Defect vs. the Nominal Kendrick Mass (differ-
ence between the nominal and the exact Kendrick masses), and can
be used in order to simplify the visualization of data originating from
complex matrices, and to better visualize compositional changes. An
example of such plots is given in Fig. 7 for (−) APPI data, and shows a
significant increase in oxygenated hydrocarbons (O1 to O5), with an
especially large increase in compounds in the mid-mass range (m/z
300–500) for weathered oils. This correlated to a reduction of the hy-
drocarbon component, which mainly lost its higher molecular weight
(m/z 350 and up) compounds.
The results so far have shown an overall increase in oxygenated hy-
drocarbons (mostly in the mid to high molecular weight range), but
have given little insight into the changes occurring within the specific
oxygen classes. Double bond equivalent (DBE) plots were created by
plotting the DBEs (number of rings and double bonds) versus the
carbon number, in order to visualize changes happening in individual
classes and get a better understanding on the saturation level of the
compounds involved. The (+) APPI plots are shown in Fig. 8 as an ex-
ample of the results that were obtained. The appearance of oxygenated
Fig. 6. Heteroatom class distributions for (−) APPI (top) and (−) ESI (bottom) of the weathering series (Massachusetts, CTC, Juniper, Elmer's Island mat). Full arrows depict a consistent
trend over the whole weathering series, while dashed arrows depict trends in which the Elmer's Island mat is an exception. Compounds showing as protonated ions are denoted by the
(H), others are radical ions.
606 A.K. Huba, P.R. Gardinali / Science of the Total Environment 563–564 (2016) 600–610
8. species that was previously observed with weathering is mostly con-
firmed by these plots; moreover, it becomes evident that for (+) APPI
mode the newly formed or enriched oxygenated compounds are mostly
unsaturated or aromatic compounds (DBE 5-15) with 15–40 carbons.
ESI and negative ionization mode results (not shown) have shown sim-
ilar ranges, and since PAHs are compounds that fall in that range, these
results may suggest that PAHs and their derivatives could be a signifi-
cant portion of the compounds that undergo oxidation during the
weathering process.
This possibility is confirmed by the results of Fig. 9, which shows a
Van Krevelen diagram (that plots H/C versus O/C and indicates
unsaturation and oxidation, respectively) for the unweathered
Fig. 8. DBE vs. carbon number for the O1–O3 containing hydrocarbons detected in the weathering series in (+) APPI mode.
Fig. 7. Kendrick Mass Defect (KMD) vs. Nominal Kendrick Mass contour plots for oxygen containing hydrocarbons (left) and hydrocarbons (right) obtained using (−) APPI conditions.
607A.K. Huba, P.R. Gardinali / Science of the Total Environment 563–564 (2016) 600–610
9. Massachusetts oil (top) and the weathered Juniper oil (bottom) in
(+) APPI mode. This plot depicts all the peaks that were assigned
a molecular formula containing at least one oxygen, and evidences
a drastic increase in the number and in the relative intensity of oxygenat-
ed compounds present in the weathered oil. The areas of major changes
(shown by the red rectangles) contain compounds with a H/C in the
range of 0.5–1.5. Completely saturated hydrocarbons would have a H/C
ratio of 2, while completely aromatic species would have a H/C of b1
(with benzene starting at 1, and the H/C decreasing with increasing num-
ber of rings, so that chrysene would have a H/C of about 0.67). The nature
of the compounds whose detected ions are enhanced is therefore either
completely aromatic in nature (when H/C b1), or contain some kind of
unsaturation and aromaticity if they fall in the H/C between 1 and 2.
All these different types of plots are essential in visualizing gen-
eral trends in data sets containing thousands of assigned compounds.
However, they do not provide unequivocal information on the functional
group types of the molecules. Some information regarding what specific
types of molecules are present can be inferred from ionization studies elu-
cidating selective ionization mechanisms or preferential ionization of in-
dividual heteroatoms. Figs. 5 and 6, show how the relative abundances
of the different oxygen classes vary based on the ionization source and
mode, and suggest that different functional group types may be involved.
For example, in negative ionization mode (Fig. 6) for weathered oils there
is a substantial prevalence of O2 species with respect to O1 species. This
agrees with previous reports (Mapolelo et al., 2009, 2011; Ruddy et al.,
2014), and has been attributed to a preferential ionization of carboxylic
acid species that can be easily deprotonated. For the unweathered oil
this is not always true as in (−) APPI the O1 species represent a larger rel-
ative fraction compared to the O2 species. This could either mean that the
O1 fraction (such as alcohols, phenols, ketones) is large enough to domi-
nate a preferential ionization of acidic O2 species, or that there are singly
oxygenated compounds mostly present in the unweathered oil that are
similarly well ionized as the carboxylic acids. In positive ionization
mode, on the other hand, there is a prevalence of O1 over O2 compounds
Fig. 10. (−) APPI spectrum of the Elmer's Island mat fortified with several individual model compounds used to test ionization efficiency, and Kendrick mass defect plot of the O1 and O2
classes of the same sample showing the corresponding detection and correct assignment of the model compounds.
Fig. 9. Van Krevelen plots of source (Massachusetts) and weathered (Juniper) oils obtained in (+) APPI mode, showing the relative increase of aromatic and unsaturated oxidation
products.
608 A.K. Huba, P.R. Gardinali / Science of the Total Environment 563–564 (2016) 600–610
10. (shown in Fig. 5), which is most likely due to the preferential ionization of
some O1 species (such as alcohols, phenols, or ketones) with respect to O2
compounds.
In order to gain a better understanding of the nature of specific oxy-
genated classes and the significance of these results, a systematic ioniza-
tion study was conducted by spiking several compounds into an Elmer's
Island mat sample. These model compounds spanned a wide range of
functional group types, including: hydrocarbons, phenols, alcohols, ke-
tones, and acids. The sample infused in APPI positive ionization mode fa-
vored the formation of the ketone functional group (coprostan-3-one),
while phenols and hydrocarbons were only weakly ionized, and straight
chain alcohols and acids showed no ionization. Negative ionization
mode, on the other hand, preferentially ionized the acids and phenols,
while none of the other compounds were detected. The mass spectrum
and Kendrick Mass Defect plot of the (−) APPI data for the Elmer's Is-
land mat are presented in Fig. 10, and show the phenols (in blue) and
the acid (in pink) that were ionized and correctly assigned. ESI results
from the same spiked sample (results not shown) mostly corroborated
the same preferential ionizations (ketones and to a lesser extent phe-
nols in positive mode, and carboxylic acids and phenols in negative
mode). These results clearly show that both the APPI and ESI sources
ionize only certain functional group types (and out of those some
much better than others) depending on the ionization mode, and this
has to be accounted for when interpreting heteroatom class assign-
ments plots from high-resolution mass spectrometric analyses. The
preferential ionization of singly oxygenated ketones in positive ioniza-
tion mode with respect to doubly oxygenated carboxylic acids suggests
that ketones could be a significant portion of the O1 class that dominates
(+) ESI and (+) APPI generated spectra, and this seems to corroborate
previous reports that have suggested ketones as oxidation products in
crude oil weathering (Ruddy et al., 2014). Phenols have shown to be
somewhat ionized and could therefore also contribute to the O1 class,
while the lack of ionization of straight chain alcohols makes them an
unlikely contributor. The O2 class (and other higher oxygen classes)
may be combinations of functional group types, and most likely contain
well ionizable groups such as ketones. In negative mode, acids are being
preferentially ionized by deprotonation, and are thus the most likely
contributor to the large relative fraction of the O2 classes, and the
acidification of crude oil compounds with weathering and especially
biodegradation has been previously reported (Charrie-Duhaut et al.,
2000; Ruddy et al., 2014; Watson et al., 2002). Moreover, based on the
H/C and DBE values detected, it is clear that the possible acidic fraction
consist of both an unsaturated and aromatic hydrocarbon backbone.
The model compound study has also shown that phenols, in addition
to acids, are a class that is well ionized in negative ionization mode,
and the abundant O1 class in the source oil could be largely due to phe-
nolic compounds, which have been proposed as intermediates in
photodegradation of PAHs (McConkey et al., 2002; Wang et al., 1995b;
Chen et al., 2006; Kong and Ferry, 2003). These compounds have been
shown to undergo further photo-oxidation, being converted to ketonic
and quinonic compounds (McConkey et al., 2002; Wang et al., 1995b;
Chen et al., 2006; Kong and Ferry, 2003). This could explain why the
O1 class in negative ionization mode decreases (oppositely to all other
oxygenated classes), as singly oxygenated phenols are converted to
doubly oxygenated quinones (see Fig. 6). GC×GC-TOF data on the
same weathering series show the enrichment of straight chain ketones
and acids and the depletion of phenols, strengthening the conclusions
on possible functional group types that are being transformed during
the weathering process (Ding and Gardinali, 2015). The higher oxygen-
ated fractions (O2 and up) are likely combinations of functional group
types and contain the well ionized carboxylic acid and phenolic groups.
The ionization study has also illustrated that since straight chain alco-
hols were not (or very poorly) ionized in any of the ionization tech-
niques, they are not likely to give a significant contribution to any
observed O1 class. This part of the study, overall, emphasized the need
to gain more in-depth knowledge on the ionization of crude oil
compounds, and offered valuable insight into the possible functional
group types that are making up the O1, O2 and higher oxygenated hy-
drocarbon classes that exhibit significant changes with weathering.
4. Conclusion
This study presented the first ultrahigh-resolution mass spectromet-
ric characterization of an oil weathering series, including the fresh
Macondo oil, two differently weathered surface slick oils, and a beached
oil tar. Preliminary GC–MS and GC–FID studies have confirmed the four
oils to be a true weathering series, and ratios of nC18/phytane and
chrysene/benz(a)anthracene have further shown the oils to be likely
biodegradation and photodegradation series. Studying a complete
weathering sequence provides the opportunity to achieve a better un-
derstanding of the type of weathering processes that were most signif-
icant in the DWH oil release, and consequently how these mechanisms
affected the composition of the oil. Ultrahigh-resolution results from
this study have shown an increase in oxygenated compounds as the
Macondo oil weathered, additionally suggesting a gain of ketones,
quinones, and acidic compounds, with a concurrent decrease in pheno-
lic compounds. The separate ionization study that was conducted by
spiking model compounds into an oil sample also helped put the results
into a new perspective and further point out serious defects in current
interpretations, as results from this study clearly showed how out of
the nine spiked compounds some were not ionized while others were
fully ionized. This proves that compound class assignment plots might
have relative intensities largely skewed by preferential ionization,
while some compounds could be abundant but poorly ionized and
thus be underestimated. Future work will include a more extensive
study of ionization mechanisms of several crude oil model compounds,
spanning a wide size range, and including more functional groups,
as well as heteroatom containing compounds. Results of such a study
will be necessary in order to make more conclusive compound assign-
ments. This will ultimately help to expand the understanding of the
type of weathering processes that have played a significant role in the
Deepwater Horizon accident, which will be fundamental in evaluating
the long-term fate and toxicity of the oil that was released.
Acknowledgments
This work was supported by BP Exploration & Production Inc. and
the BP Gulf Coast Restoration Organization through FIU project
800001596. This is contribution number 999 from the Southeast Envi-
ronmental Research Center (SERC) at Florida International University.
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