Showing papers on "Hydrocarbon published in 1995"

Dehydrogenation of methane on supported molybdenum oxides. Formation of benzene from methane

Abstract: The dehydrogenation of methane on MoO3 supported on various oxides has been investigated under non-oxidizing conditions in a fixed bed, continuous flow reactor. Detailed measurements were performed with MoC3/SiO2. The reaction of methane was observed above 923 K after a significant time lag, when a partial reduction of Mo6+ occurred, the reduced phase being characterized by X-ray photoelectron spectroscopy (XPS). The initial gaseous products are CO2, H2O, H2 and CO. But this stage is followed by the dehydrogenation of methane and coupling of hydrocarbon fragments to various hydrocarbons. A possible pathway of the formation of benzene, the main product of reaction with selectivities ranging from 26 to 56%, is suggested.

Interfacial tension in high-pressure carbon dioxide mixtures

Abstract: High-pressure interfacial- and surface-tension phenomena govern the migration and recovery of oil and gas from hydrocarbon reservoirs. The phenomena are of particular relevance to phase separation and mass transfer in light hydrocarbon fractionation plants and in propane deasphalting in lubricating oil refining. Interfacial tensions of carbon dioxide-water-alcohol mixtures were measured at temperatures in the range 5--71 C and pressures 0.1--18.6 MPa, using the capillary rise method. The alcohols were methanol (0.136 mf), ethanol (to 0.523 mf), and isopropyl alcohol (to 0.226 mf). Interfacial tension (IFT) decreased linearly with both temperature and pressure din the low-pressure range (gaseous CO{sub 2}) but was largely independent of pressure at high pressure (liquid or supercritical CO{sub 2}). There was a zone in the vicinity of the critical pressure of CO{sub 2}-as much as 20 C below and 10 C above the carbon dioxide critical temperature--where IFT became small. This is attributed to the formation of a second CO{sub 2}-rich phase. The isotherms exhibited a crossover pressure near 3 MPa for all systems examined.

Physical properties of insect cuticular hydrocarbons: The effects of chain length, methyl-branching and unsaturation

Abstract: The waterproofing abilities of insect cuticular lipids, consisting mainly of hydrocarbons, are thought to depend upon their biophysical properties. However, little is known regarding the effects of specific structural changes upon cuticular lipid properties. We examined the phase behavior of pure hydrocarbons differing in chain length, methyl-branching pattern, and unsaturation, using Fourier transform infrared spectroscopy. Melting temperatures ( T m ) of 21–40 carbon n -alkanes increased by 1–3°C for an increase in backbone chain length of one carbon atom. The effects of methyl-branching on hydrocarbon properties depended upon the location of the methyl group along the molecule. Melting temperatures of 25-carbon long methylpentacosanes decreased by over 30°C as the location of the methyl moiety was shifted from the terminal portion of the molecule to more internal positions. Addition of a second methyl branch had additional effects on T m . Unsaturation decreased T m by 50°C or more.

Photodegradation of Water Pollutants

Abstract: Introduction: Advanced Oxidation Processes. Mechanisms: eaq-, 102, .OH and Peroyxy Radicals. Sensitized Excitation. Semiconductor Promoted Photooxidation. Experimental Techniques. Inorganic Ions and Molecules: Water and Hydrogen Peroxide. Halide Ions. Nitrogen Compounds. Phosphorus Oxyanions. Sulfur Oxyanions and Sulfide. Heavy Metal Ions. Organo-Metallic Compounds. Hydrocarbon Derivatives: Aliphatic Compounds. Aromatic and Other Cyclic Compounds. Long-Chain Compounds. Photo-induced Nitrosation and Nitration. Halocarbons: Aliphatic Halocarbons. Aromatic and Other Cyclic Compounds. Organic Nitrogen Compounds: Triazines. Amines, Amides, and Carbamates. Nitrobenzene and Nitrophenols. Bromoxynil and Choroxynil. Thymine. Triclopyr. Fenarimol. Flavins. Catecholamines. Dyes. Polycyclic Aromatic Nitrogen Heterocycles. Organic Phosphorus Compounds: Homogenous Photolysis. Heterogenous Photodegradation. Organic Sulfur Compounds Natural and Waste Waters: Natural Transformations in Freshwater and Oceans. Treatment of Polluted Groundwater. Treatment of Waste Water. Photodynamic Sterilization. Concentrated Sunlight. Evaluation and Future Trends: Photodegradation Compared with Other Methods. Cost estimates, Energetics, and Conclusions. References Index THis TOC has 3 levels: Introduction Advanced Oxidation Processes Mechanisms: eaq-, 102, .OH and Peryoxy Radicals Sensitized Excitation Semiconductor-Promoted Photooxidation Primary Reaction Steps Kinetic Models Role of Oxygen Direct and Indirect Photodegradations Zeta Potentials and Surface Properties Catalyst Preparations Surface Density of OH Groups in TiO2 Particles Quantum Yields and Turnover Numbers Experimental Techniques Reactor Design Laser and Excimer Light Sources Light-Dark Cycling Concentrated Sunlight Photoelectrochemical Reactions Inorganic Ions and Molecules Water and Hydrogen Peroxide Halide Ions Nitrogen Compounds Phosphorus Oxyanions Sulfur Oxyanions and Sulfide Heavy Metal Ions Organo-Metallic Compounds Hydrocarbon Derivatives Aliphatic Compounds Homogenous Photolysis Heterogenous Photodegradation Aromatic and Other Cyclic Compounds Homogenous Photolysis Heterogenous Photodegradation Oil Spills Long-Chain Compounds Surfactants Lignin Sulfonates and Kraft Wastewater Phthalate Esters Polymers Photoinduced Nitrosation and Nitration Halocarbons Aliphatic Halocarbons Aromatic and Other Cyclic Halocarbons Haloaromatics Halogenophenols Polychlorinated Dioxins, Dibenzofurans, and Biphenyls Halocarbon Pesticides Organic Nitrogen Compounds s-Triazines Amines, Amides, and Carbamates Nitrobenzene and Nitrophenols Bromoxynil and Chloroxynil Thymine Triclopyr Fenarimol Flavins Catecholamines Dyes Azo Dyes Tannery Dyes Dyes in Municipal Wastewater Methyl Violet Methyl Viologen Polycyclic Aromatic Nitrogen Heterocycles Organic Phosphorus Compounds Homogenous Photolysis Heterogenous Photodegradation Organic Sulfur Compounds Natural and Waste Waters Natural Transformations in Freshwater and Oceans Treatment of Polluted Groundwater Treatment of Wastewater Photodynamic Sterilization Concentrated Sunlight Evaluation and Future Trends Photodegradation Compared with Other Methods Ozonation Biodegradation Radiolysis Ultrasonics Corona Discharge Electrochemical Oxidation Oxidation in Supercritical Water Cost Estimates, Energetics, and Conclusions Cost Estimates Energy Requirement Evaluation Future Trends References Index

Hydrogen atom bond increments for calculation of thermodynamic properties of hydrocarbon radical species

Abstract: Hydrogen atom bond increments (HBI) are defined and a data base is derived for accurately estimating AH°29s, S°298, and CP(T) (300 < 77K < 1500) on generic classes of hydrocarbon (HC) radical species relevant to combustion and atmospheric chemistry, using these thermodynamic property increments. The HBI group technique is based on known thermodynamic properties of the parent molecule and calculated changes that occur upon formation of a radical via loss of a H atom. The HBI approach incorporates (i) evaluated literature bond energies, (ii) calculated entropy and heat capacity increments resulting from loss and/or change in vibrational frequencies including frequencies corresponding to inversion of the radical center, (iii) increments from changes in barriers to internal rotation, and (iv) spin degeneracy. Twenty five HBI groups corresponding to alkyl (primary, secondary, and tertiary), vinyl, allenic, allylic, benzyl, acetylenic, and other conjugated hydrocarbon radicals are defined, and their group values are calculated. The HBI groups, when coupled with thermodynamic properties of the appropriate “parent” molecule, yield accurate thermodynamic properties for the respective radicals.

Microbial degradation in soil microcosms of fuel oil hydrocarbons from drilling cuttings.

Abstract: The biodegradation of the fuel oil hydrocarbons contained in drilling cuttings was studied in soil microcosms during a 270-day experiment. Concentration and chemical composition of residual hydrocarbons were periodically monitored by quantitative capillary gas chromatography. The decrease in hydrocarbon concentration was logarithmic with time. At the end of the experiment, the fuel oil was 75% degraded. In the saturated fraction, normal and branched alkanes were almost totally eliminated in 16 days ; 22% of the cycloalkanes were not assimilated. The aromatic fraction was 71% degraded ; some polycyclic aromatics were persistent. The resin fraction (10% of the initial weight) was completely refractory to biodegradation. The inorganic part of drilling cuttings had no influence on the biodegradation rates of hydrocarbons. Biogenic hydrocarbons and traces of degradable fuel oil hydrocarbons were protected from microbial activity by the soil and cuttings matrix. Enumerations of total heterotrophic bacteria and hydrocarbon-utilizing bacteria showed a strong stimulation in both populations. Hydrocarbon-degrading strains of bacteria and fungi were isolated and identified at the generic or specific level.

Predictive model for estimating the extent of petroleum hydrocarbon biodegradation in contaminated soils.

Abstract: A series of solid- and slurry-phase soil bioremediation experiments involving different crude oils and refined petroleum products were performed in order to investigate the factors which affect the maximum extent of total petroleum hydrocarbon (TPH) biodegradation. Utilizing a comprehensive petroleum hydrocarbon characterization procedure involving group type separation analyses, boiling point distributions, and hydrocarbon typing by field desorption mass spectroscopy, initial and final concentrations of specified hydrocarbon classes were determined in each of the seven bioremediation treatments

Method for inhibiting hydrate formation

Abstract: A method for inhibiting the formation of clathrate hydrates in a fluid (e.g. natural gas) having hydrate-forming constituents is disclosed. The hydrate inhibitors used in the method are substantially water soluble polymers formed from an N-substituted acrylamide having two nitrogen substituent groups, R1 and R2, where R1 is a hydrocarbon group having from one to ten carbon atoms and zero to four heteroatoms selected from the group consisting of nitrogen, oxygen, sulfur, and combinations thereof, and R2 is a hydrogen atom or a hydrocarbon group having from one to ten carbon atoms and zero to four heteroatoms selected from the group consisting of carbon, nitrogen, oxygen, and sulfur. Alternatively, R1 and R2 may be linked to produce a cyclic ring having ten atoms comprising a combination of between three and ten carbon atoms and zero to four heteroatoms selected from the group consisting of nitrogen, oxygen, sulfur, and combinations thereof. Some examples of such inhibitors include poly(N-ethylacrylamide), poly(N,N-diethylacrylamide), poly(N-methyl, N-acrylamide), poly(iso-propylacrylamide), poly(N-propylacrylamide), poly(N-cyclopentylacrylamide), poly(N-cyclohexylacrylamide), poly(acryloylpyrrolidine), poly(acryloylpiperidine), poly(acryloylmorpholine) and various N-substituted acrylamide copolymers.

Catalytic Dimerization of Propene by Nickel-Phosphine Complexes in 1-Butyl-3-methylimidazolium Chloride/AlEtxCl3-x (x = 0, 1) Ionic Liquids

Abstract: The dimerization of propene was catalyzed by cationic nickel complexes in a two-phase solvent system using organochloroaluminate ionic liquids as the solvent for the catalyst. In ionic liquids containing an excess of strongly coordinating chloride ions, i.e., basic, no activity was observed. In contrast, melts containing an excess of alkylchloroaluminum species, i.e., acidic, stabilized the active cationic nickel species. The reaction products separate as an organic layer. Molecular organochloroaluminum species were extracted, and the composition of the salt was strongly modified. This was circumvented using a salt which contains an excess of aluminum chloride. The propene dimers obtained by this way can be transformed either into ethers or into alkanes to produce high octane number additives for gasoline. The effects of phosphine ligands coordinated on nickel and operating variables were investigated in order to maximize the octane number of the corresponding alkanes and ethers.

Lubricating base oil preparation process

Abstract: A process for the preparation of lubricating base oils comprising subjecting a waxy raffinate to a pour point reducing treatment, and recovering lubricating base oil therefrom, which waxy raffinate has been prepared by contacting a hydrocarbon product with hydrogen in the presence of a hydroconversion catalyst, comprising a catalytically active metal having hydrogenation/dehydrogenation activity supported on a refractory oxide carrier, under conditions such that hydrocracking and hydroisomerisation of the hydrocarbon product occur to yield the waxy raffinate, wherein the hydrocarbon product has been prepared by: (a) contacting a mixture of carbon monoxide and hydrogen with a hydrocarbon synthesis catalyst at elevated temperature and pressure to prepare a substantially paraffinic hydrocarbon wax; and (b) contacting the hydrocarbon wax so-obtained with hydrogen in the presence of a hydrogenation catalyst under conditions such that substantially no isomerisation or hydrocracking of the hydrocarbon wax occurs to yield the hydrocarbon product.

Actions of a versatile fluorene-degrading bacterial isolate on polycyclic aromatic compounds.

Abstract: Pseudomonas cepacia F297 grew with fluorene as a sole source of carbon and energy; its growth yield corresponded to an assimilation of about 40% of fluorene carbon. The accumulation of a ring meta-cleavage product during growth and the identification of 1-indanone in growth media and washed-cell suspensions suggest that strain F297 metabolizes fluorene by mechanisms analogous to those of naphthalene degradation. In addition to fluorene, strain F297 utilized for growth a wide variety of polycyclic aromatic compounds (PACs), including naphthalene, 2,3-dimethylnaphthalene, phenanthrene, anthracene, and dibenzothiophene. Fluorene-induced cells of the strain also transformed 2,6-dimethylnaphthalene, biphenyl, dibenzofuran, acenaphthene, and acenaphthylene. The identification of products formed from those substrates (by gas chromatography-mass spectrometry) in washed-cell suspensions indicates that P. cepacia F297 carries out the following reactions: (i) aromatic ring oxidation and cleavage, apparently using the pyruvate released for growth, (ii) methyl group oxidations, (iii) methylenic oxidations, and (iv) S oxidations of aromatic sulfur heterocycles. Strain F297 grew with a creosote-PAC mixture, producing an almost complete removal of all aromatic compounds containing 2 to 3 rings in 14 days, as demonstrated by gas chromatography analysis of the remaining PACs recovered from cultures. The identification of key chemicals confirmed that not only are certain compounds depleted but also the anticipated reaction products are found.

Vapor + Liquid Equilibria for the Ternary System Methane + Ethane + Carbon Dioxide at 230 K and Its Constituent Binaries at Temperatures from 207 to 270 K

Abstract: Vapor-liquid equilibrium data for the binary system methane + carbon dioxide were measured at 230, 250, and 270 K. The ethane + carbon dioxide system was studied at 207, 210, 213, 230, 250, and 270 K, and the methane + ethane system was studied at 210, 230, 250, and 270 K. Ternary vapor-liquid equilibria for the methane + ethane + carbon dioxide system were measured at 230 K over the pressure range from 1.15 to 6.59 MPa. The Peng-Robinson equation of state was used to model the systems, and binary interaction coefficients are reported.

Polynuclear Aromatic Hydrocarbons Hydrogenation. 1. Experimental Reaction Pathways and Kinetics

Abstract: The relationship between molecular structure and hydrogenation reactivity in heavy oil hydroprocessing was sought via the elucidation of the controlling reaction pathways and kinetics of one-, two-, three-, and four-fused ring compounds. Hydrogenation reactions of o-xylene, tetralin, naphthalene, phenanthrene, anthracene, pyrene, and chrysene and their multicomponent mixtures were studied in cyclohexane solvent using a presulfided CoMo/Al[sub 2]O[sub 3] catalyst in a 1-liter batch autoclave at P[sub H[sub 2]] = 68.1 atm and T = 350 C. Quantitative network analysis allowed estimation of 45 hydrogenation rate parameters and an equal number of equilibrium ratios for 36 aromatic and hydroaromatic compounds. These values were then used in the evaluation of five adsorption parameters for aromatic ring number-based lumps from the multicomponent mixture experiments. Three classes of hydrogenation were discerned, based on the magnitude of numerator rate parameters. The adsorption parameters clearly increased with increasing aromatic ring number.

Chemical Characterization of Crude Oil Residues from an Arctic Beach by GC/MS and GC/FID.

Abstract: A complete `total oil analysis method` suitable for monitoring chemical composition changes and studying the fate of 12-year-old weathered oil residues from an arctic beach is described. The characterizations not only are through analyses of individual aliphatic, aromatic, and biomarker compounds but also are through `pattern recognition` plots involving more than 100 important oil components and component groupings. The weathered percentages of residual oil in Baffin Island oil spill samples are quantified using C{sub 29} and C{sub 30} {alpha}{beta}-hopane in the fresh` source oil as internal oil references. The values of the weathered percentages show excellent correlation to the total solvent-extractable materials (TSEM), total petroleum hydrocarbons (TPH), aliphatic, aromatic, and biomarker compound analysis results. Biodegradation is demonstrated to have played an important role in the degradation and removal of the residual oil. Twelve years after the spill, the composition changes due to weathering progress much more slowly, and this slower rate of change will continue under these arctic conditions. 31 refs., 8 figs., 5 tabs.

Studies on the Catalytic Conversion of Canola Oil to Hydrocarbons: Influence of Hybrid Catalysts and Steam

Abstract: The conversion of canola oil (used as a representative feed material for waste oils and fats) was studied in the presence and absence of steam using silica-alumina, HZSM-5, and 4 Hybrid catalysts. The hybrid catalysts were prepared by adding H-Y to silica-alumina in the weight ratios 1:3 and 3:1 and HZSM-5 to silica-alumina in the weight ratios 1:3 and 3:1. The conversions were performed at atmospheric pressure, a temperature range of 400-550 °C, and weight hourly space velocities of 1.8 and 3.6 h -1 (WHSV) in a fixed bed reactor. The objective was to investigate the production of both liquid and gaseous hydrocarbon products from the catalytic conversion of canola oil. In addition, it was intended to study the effect of steam on the product selectivities. The conversions were high on all the catalysts and ranged between 81 and 100%. Conversion to an organic liquid product (OLP) varied significantly with temperature and space velocity. The yields were between 22-53 wt % with silica-alumina and between 23 and 63 wt % with HZSM-5 catalyst. In most cases, hydrocarbons formed the major components in the OLP. HZSM-5 provided a high selectivity for aromatic hydrocarbons than silica-alumina catalyst, while the selectivity for aliphatic hydrocarbons was higher with silica-alumina than HZSM-5 catalyst in the OLP products. The olefin/paraffin ratio in the gas products was low but it increased tremendously in the presence of steam, indicating that dehydrogenation reactions were predominant in the presence of steam. The gas yield increased with temperature and decreased with increase in WHSV. Ethylene, propylene, isobutylene, propane, and n-butane were some of the major components of the gas products. Prolonged catalyst life (decrease in coke formation) and enhanced olefin formation were the main advantages of cofeeding steam during conversion. When zeolite catalysts were added to silica-alumina catalyst, the coke formation and OLP yields decreased whereas the gas yields increased. With silica-alumina-H-Y hybrid catalysts, the aromatic content of OLP increased, resulting in an overall increase in the hydrocarbon content of the OLP. On the other hand, the aromatic hydrocarbon content increased at the expense of aliphatic hydrocarbons. With silica-alumina-HZSM-5 hybrid catalysts, the hydrocarbon content of the OLP was similar to those obtained with pure HZSM-5 catalyst; i.e., they were composed mostly of aromatic hydrocarbons and only small fractions of aliphatic hydrocarbons. In general, cracking and aromatization reactions increased significantly with addition of H-Y or HZSM-5 to silica-alumina.

Hydrogen sulfide scavenging process

Abstract: The levels of hydrogen sulfide and organic sulfides present in gaseous or liquid hydrocarbon streams or mixtures thereof are reduced by contacting the streams with a composition comprising the reaction product of a dialdehyde having two carbonyl groups; and an alkanolamine having at least one hydrogen atom bonded directly to a nitrogen atom. The amounts of dialdehyde and alkanolamine provide between about 1.5 and about 3 equivalents of hydrogen atoms bonded directly to a nitrogen atom in the alkanolamine for every equivalent of carbonyl groups in the dialdehyde. The reaction product thus formed is substantially free of triazines.

Fate of microbial metabolites of hydrocarbons in a coastal plain aquifer: the role of electron acceptors.

Abstract: A combined field and laboratory study was undertaken to understand the distribution and geochemical conditions that influence the prevalence of low molecular weight organic acids in groundwater of a shallow aquifer contaminated with gasoline. Aromatic hydrocarbons from gasoline were degraded by microbially mediated oxidation-reduction reactions, including reduction of nitrate, sulfate, and Fe(III). The biogeochemical reactions changed overtime in response to changes in the hydrogeochemical conditions in the aquifer. Aliphatic and aromatic organic acids were associated with hydrocarbon degradation in anoxic zones of the aquifer. Laboratory microcosms demonstrated that the biogeochemical fate of specific organic acids observed in groundwater varied with the structure of the acid and the availability of electron acceptors. Benzoic and phenylacetic acid were degraded by indigenous aquifer microorganisms when nitrate was supplied as an electron acceptor. Aromatic acids with two or more methyl substituents on the benzene ring persisted under nitrate-reducing conditions. Although iron reduction and sulfate reduction were important processes in situ and occurred in the microcosms, these reactions were not coupled to the biological oxidation of aromatic organic acids that were added to the microcosms as electron donors.