Showing papers on "Hydrocarbon published in 1996"

Reduction of CO2 during serpentinization of olivine at 300 °C and 500 bar

Abstract: CO 2 reduction processes occurring during experimental serpentinization of olivine at 300 °C and 500 bar confirm that ultramafic rocks can play an important role in the generation of abiogenic hydrocarbon gas. Data reveal that conversion of Fe(II) in olivine to Fe(III) in magnetite during serpentinization leads to production of H 2 and conversion of dissolved CO 2 to reduced-C species including methane, ethane, propane, and an amorphous carbonaceous phase. Hydrocarbon gases generated in the process fit a Schulz-Flory distribution consistent with catalysis by mineral reactants or products. Magnetite is inferred to be the catalyst for methanization during serpentinization, because it has been previously shown to accelerate Fischer-Tropsch synthesis of methane in industrial applications involving mixtures of H 2 and CO 2 . The carbonaceous phase was predominantly aliphatic, but had a significant aromatic component. Although this phase should ultimately be converted to hydrocarbon gases and graphite, if full thermodynamic equilibrium were established, its formation in these experiments indicates that the pathway for reduction of CO 2 during serpentinization processes is complex and involves a series of metastable intermediates.

Catalytic Cleavage of the C-H and C-C Bonds of Alkanes by Surface Organometallic Chemistry: An EXAFS and IR Characterization of a Zr-H Catalyst

Abstract: The catalytic cleavage under hydrogen of the C & singlebond;H and C & singlebond;C bonds of alkanes with conventional catalysts requires high temperatures Room-temperature hydrogenolysis of simple alkanes is possible on a well-defined and well-characterized zirconium hydride supported on silica obtained by surface organometallic chemistry The surface structure resulting from hydrogenolysis of (≡SiO)Zr(Np)3 (Np, neopentyl) was determined from the extended x-ray absorption fine structure (EXAFS) and 1H and 29Si solid-state nuclear magnetic resonance and infrared (IR) spectra A mechanism for the formation of (≡SiO)3Zr-H and (≡SiO)2SiH2 and the resulting low-temperature hydrogenolysis of alkanes is proposed The mechanism may have implications for the catalytic formation of methane, ethane, and lower alkanes in natural gas

Quantitative analysis of fuel-related hydrocarbons in surface water and wastewater samples by solid-phase microextraction.

Abstract: Solid-phase microextraction (SPME) parameters were examined on water contaminated with hydrocarbons including benzene and alkylbenzenes, n-alkanes, and polycyclic aromatic hydrocarbons (PAHs). Abso...

Conversion of methane to benzene over Mo2C and Mo2C/ZSM-5 catalysts

Abstract: The activation and dehydrogenation of CH2 on Mo2C and MO2C/ZSM-5 have been investigated under non-oxidizing conditions. Unsupported Mo2C exhibited very little activity towards methane decomposition at 973 K. The main reaction pathway was the decomposition of methane to give hydrogen and carbon with a trace amount of ethane. Mixing Mo2C with ZSM-5 support somewhat enhanced its catalytic activity, but did not change the products of the reaction. A dramatic change in the product formation occurred on partially oxidized Mo2C/ZSM-5 catalyst; besides some hydrocarbons benzene was produced with a selectivity of 70–80% at a conversion of 5–7%. Carburization of highly dispersed MoO3 on ZSM-5 also led to a very active catalyst: the conversion of methane at the steady state was 5–6% and the selectivity of benzene formation was 85%.

Hydrocarbon Activation via Reversible 1,2-RH-Elimination from (tBu3SiNH)3ZrR: Synthetic, Structural, and Mechanistic Investigations

Abstract: Hydrocarbyl complexes, (tBu3SiNH)3ZrR (1-R), were prepared via metatheses of (tBu3SiNH)3ZrCl (1-Cl) with RMgX or RLi (R = Me, Et, Cy, CH2Ph, allyl, CHCH2, Ph, CH2tBu, C⋮CPh, C⋮CtBu), through addition of isobutylene, H2CCCMe2, and acetylene to 1-H (R = iBu, dma, or CHCH2), and by CH-bond activation; thermal 1,2-RH-elimination from 1-R produced putative (tBu3SiNH)2ZrNSitBu3 (2), which was subsequently trapped by R‘H. Thermolysis of 1-R (∼100 °C, R = Me or Cy) in the presence of H2, c-C3H6, and CH4 in cyclohexane or neat C6H6, mesitylene, and toluene afforded 1-R (R = H, cPr, Me, Ph, CH2-3,5-Me2C6H3) and a mixture of 1-CH2Ph and 1-C6H4Me, respectively. Exposure of 1-Cy to C2H4 or C6H6 in cyclohexane provided 1-CHCH2 or 1-Ph, respectively, but further reaction produced 12-(trans-HCCH) and 12-(p-C6H4) through double CH-bond activation. Thermolysis of (tBu3SiND)3ZrCH3 (1-(ND)3-CH3) in C6H6 or C6D6 yielded CH3D, and 1C6H5 or 1-(ND)3C6D5, through reversible benzene activation. Thermolysis of 1-Cy in neat cyclohex...

Kinetic Aspects of Surfactant Solubilization of Soil-Bound Polycyclic Aromatic Hydrocarbons

Abstract: The effect of nonionic polyoxyethylene (POE) surfactants on the solubilization rate of individual polycyclic aromatic hydrocarbons (PAHs) from a weathered, coal tar-contaminated soil obtained from a manufactured gas plant (MGP) site was studied. The release of PAHs upon surfactant washing were measured with time. Time-varying adsorption of PAHs to Tenax resin was also studied. Because of its large sorption coefficients for organic solutes, Tenax maintained near-zero concentrations of aqueous PAHs, thereby maximizing transfer of PAHs at the soil−water interface. The release of PAHs from the MGP soil exhibited a nonequilibrium behavior, typical of such soils. Surfactants significantly enhanced the rate of PAH solubilization, the amount solubilized being dependent upon the structure of the surfactant. It is postulated that the enhancement of PAH release by surfactants occurs by two mechanisms: (1) micellar solubilization by increased concentration gradient at the soil/tar−water interface and (2) sorption an...

The effect of the ζ potential on the stability of a non-polar oil-in-water emulsion

Abstract: The aim of this work was to investigate the electrophoretic properties of emulsion droplets of aliphatic hydrocarbons containing C6 to C16 carbon atoms in hydrocarbon chains. As it was observed experimentally, the emulsion droplets of hydrocarbons C9 to C16 revealed a completely different course of changes of the zeta potential due to pH than the n-alkanes of shorter hydrocarbon chains (C6 to C8). They revealed a negative value of the zeta potential, lower by almost twice. The zeta potentials of emulsion droplets of the n-alkanes, from n-nonane to n-hexadecane, do not practically depend on the length of the hydrocarbon chain but, first of all, on the pH of aqueous solutions. The cause of the origin of the negative zeta potential of n-alkane droplets lies in the selective adsorption of -OH ions, causing the gathering of the excessive negative charge at the oil-water interface. As it was assumed, the stability of oil-in-water emulsion droplets in the solution, i.e., the time of collection of liquid hydrocarbons C6H28 on the surface of aqueous solutions, is the criterion of the life of emulsion droplets of n-alkanes. The observations indicate a close correlation between the emulsion droplets stability of the tested aliphatic hydrocarbons in water and the value changes of the zeta potential.

The design and testing of an autothermal reactor for the conversion of light hydrocarbons to hydrogen I. The kinetics of the catalytic oxidation of light hydrocarbons

Abstract: The catalytic oxidation of methane, ethane and propane on a Pt/δ-Al2O3 catalyst has been studied as part of the design of an autothermal reactor in which exothermic oxidation and endothermic steam reforming are combined. Light-off temperatures and the kinetics of oxidation of the hydrocarbons have been determined. The power rate law kinetics are found to approximate to first order in hydrocarbon and to show a negative order with respect to oxygen. The dependence of rate on oxygen pressure has been shown to be non-monotonic. The kinetics of methane oxidation is best described by a Langmuir-Hinshelwood model in which molecular adsorbed hydrocarbon reacts with adsorbed atomic oxygen. Pt-based catalysts are shown to be more active than Ni-based catalysts for hydrocarbon oxidation.

Method of treating sour gas and liquid hydrocarbon

Abstract: Reaction of 1,3,5-tri-substituted-hexahydro-1,3,5- triazine is accelerated in H2S scavenging by the addition of quaternary ammonium compound. The preferred hexahydro triazines are 1,3,5-tri-methyl-hexahydro-1,3,5-triazines and 1,3,5-tri-methoxypropyl-hexahydro-1,3,5-triazines. The blend of the hexahydro triazine and quaternary ammonium compounds can be used to treat sour gases and liquids (e. g. sour kerosene, crude oil, fuel oils, heating oils, distillate fuels, bunker fuel oil, and the like.

Geopressuring Mechanism of Organic Matter Cracking: Numerical Modeling

Abstract: Since the 1950s, hydrocarbon generation has been considered as one of the most important abnormal pressuring mechanisms. Hydrocarbon generation effects on pore-pressure evolution: (1) it increases the pore fluid volume through the conversion of solid kerogen into liquid or gaseous hydrocarbon, and (2) it decreases the sediment permeability because hydrocarbons remain an immiscible phase in pore water. In this paper, the two products of organic matter decomposition, liquid hydrocarbon (oil) and gaseous hydrocarbon (methane), are assumed to occur in sequence as a supplementary phase in pores as a basis for evaluating the effect of this pressuring mechanism. A simplified three-stage first-order kinetic reaction model is applied to simulate the generation of oil and gas. We u e a numerical basin model with a two-phase hydrodynamic formulation to calculate the effect of organic maturation on geopressure evolution. Oil generation does not play an important role except when the organic matter content of rocks is relatively large (>5%); however, the generation of gas has a large influence. The results show that beneath a certain depth, oil-to-gas cracking strongly influences overpressuring. The effect of this mechanism becomes more important with increasing organic matter content of rocks. Several environmental conditions, such as kerogen type, temperature gradient, and lithological characteristics, influence to various degrees the effect of organic matter maturation on overpressure development.

Solvent-Augmented Mineralization of Pyrene by a Mycobacterium sp.

Abstract: The biodegradation of polycyclic aromatic hydrocarbon pollutants is constrained, in part, by their solid physical state and very low water solubility. Searching for ways to overcome these limitations, we isolated from soil a bacterium capable of growing on pyrene as a sole source of carbon and energy. Acid-fast stain, morphology, and fatty acid profile identified it as a Mycobacterium sp. In a mineral salts solution, the isolate mineralized 50% of a 250-(mu)g/ml concentration of [(sup14)C]pyrene in 2 to 3 days. Detergent below the critical micelle concentration increased the pyrene mineralization rate to 154%, but above the critical micelle concentration, the detergent severely inhibited pyrene mineralization. The water-miscible solvent polyethylene glycol was inhibitory. The hydrophobic solvents heptamethylnonane, decalin, phenyldecane, and diphenylmethane were also inhibitory at several concentrations tested, but the addition of paraffin oil, squalene, squalane, tridecylcyclohexane, and cis-9-tricosene at 0.8% (vol/vol) doubled pyrene mineralization rates by the Mycobacterium sp. without being utilized themselves. The Mycobacterium sp. was found to have high cell surface hydrophobicity and adhered to the emulsified solvent droplets that also contained the dissolved pyrene, facilitating its mass transfer to the degrading bacteria. Cells physically adhering to solvent droplets metabolized pyrene 8.5 times as fast as cells suspended in the aqueous medium. An enhanced mass transfer of polycyclic aromatic hydrocarbon compounds to microorganisms by suitable hydrophobic solvents might allow the development of solvent-augmented biodegradation techniques for use in aqueous or slurry-type bioreactors.

FTIR studies on the selective oxidation and combustion of light hydrocarbons at metal oxide surfaces. Part 2.—Propane and propene oxidation on Co3O4

Abstract: The interaction of propane and propene and of C3, C2 and C1 oxygenates (propane-1-ol, propan-2-ol, allyl alcohol, acetone, propanal, acrolein, acrylic, propionoic, acetic and formic acids and CO2) on oxidized Co3O4 +x has been studied by FTIR spectroscopy, with the aim to collect data on the mechanism of hydrocarbon catalytic combustion. Propene is already oxidized to acrylate species at RT and burns completely starting from 473 K. Propane already gives rise to acetate, propanoate and acrylate species below 373 K. A reaction scheme for catalytic propane oxidation is proposed. The behaviour of Co3O4 +x combustion catalyst surfaces are compared with those of MgCr2O4 +x, previously investigated. In both cases nucleophilic oxygen species (lattice O2– anions at the oxidized surface) are thought to be involved in catalytic combustion, which occurs via overoxidation of adsorbed partially oxidized compounds.

Formation of Hydrocarbons from the Reduction of Aqueous CO2 by Zero-Valent Iron

Abstract: The reduction of aqueous CO2 by zero-valent iron was studied in batch and column experiments. Ten hydrocarbons up to C5 were identified as products of the reduction process and were shown to have Anderson−Schulz−Flory (ASF) product distributions. A direct consequence of the ASF product distribution is that a significant mass of hydrophobic hydrocarbons may remain sorbed to the iron surface. Based on a reaction mechanism proposed for the electroreduction of aqueous CO2 with nickel electrodes, iron acts as both a reactant by corroding to supply electrons and as a catalyst by promoting the formation and growth of hydrocarbon chains. Water is also a reactant in the system. When iron is used to enhance the dechlorination of chlorinated organic compounds, the slow desorption of the hydrocarbon products may become the rate-limiting step in the reaction.

Olefin separation membrane and process

Abstract: A membrane and process for separating unsaturated hydrocarbons from fluid mixtures. The membrane and process differ from previously known membranes and processes, in that the feed and permeate streams can both be dry, the membrane need not be water or solvent swollen, and the membrane is characterized by a selectivity for an unsaturated hydrocarbon over a saturated hydrocarbon having the same number of carbon atoms of at least about 20, and a pressure-normalized flux of said unsaturated hydrocarbon of at least about 5×10 -6 cm 3 (STP)/cm 2 ·s·cmHg, said flux and selectivity being measured with a gas mixture containing said unsaturated and saturated hydrocarbons, and in a substantially dry environment.

Molybdenum based catalysts. I. MoO2 as the active species in the reforming of hydrocarbons

Abstract: The XPS spectra of bulk MoO2 and MoO3 are reported. Commercial MoO2 reveals the presence of multilayers of MoO3 covering bulk MoO2. In situ reduction of bulk MoO3 by H2 at temperatures equal to 623 K and less than 673 K reduces the superficial layer(s) to mainly MoO2. Such phase is characterised by a certain density of states in terms of the free 4d, 5s electrons localised mainly on the Mo atoms and observed in the valence band energy region at the Fermi-level in the XP spectrum of this system. Catalytic reactions on the MoO2 phase of 2-methylpentane at atmospheric pressure using a mixture of the hydrocarbon (5 Torr) with hydrogen (755 Torr) yield 3-methylpentane andn-hexane as the main products in roughly equal amounts. These results are interpreted in terms of dual sites on the MoO2 surface.

Hydrocarbon/hydrogen mixed gas permeation in poly(1‐trimethylsilyl‐1‐propyne) (PTMSP), poly(1‐phenyl‐1‐propyne) (PPP), and PTMSP/PPP blends

Abstract: The gas permeation properties of poly(1-trimethylsilyl-1-propyne) (PTMSP), poly(1-phenyl-1-propyne) (PPP), and blends of PTMSP and PPP have been determined with hydrocarbon/hydrogen mixtures. For a glassy polymer, PTMSP has unusual gas permeation properties which result from its very high free volume. Transport in PPP is similar to that observed in conventional, low-free-volume glassy polymers. In experiments with n-butane/hydrogen gas mixtures, PTMSP and PTMSP/PPP blend membranes were more permeable to n-butane than to hydrogen. PPP, on the other hand, was more permeable to hydrogen than to n-butane. As the PTMSP composition in the blend increased from 0 to 100%, n-butane permeability increased by a factor of 2600, and n-butane/hydrogen selectivity increased from 0.4 to 24. Thus, both hydrocarbon permeability and hydrocarbon/hydrogen selectivity increase with the PTMSP content in the blend. The selectivities measured with gas mixtures were markedly higher than selectivities calculated from the corresponding ratio of pure gas permeabilities. The difference between mixed gas and pure gas selectivity becomes more pronounced as the PTMSP content in the blend increases. The mixed gas selectivities are higher than pure gas selectivities because the hydrogen permeability in the mixture is much lower than the pure hydrogen permeability. For example, the hydrogen permeability in PTMSP decreased by a factor of 20 as the relative propane pressure (p/psat) in propane/hydrogen mixtures increased from 0 to 0.8. This marked reduction in permanent gas permeability in the presence of a more condensable hydrocarbon component is reminiscent of blocking of permanent gas transport in microporous materials by preferential sorption of the condensable component in the pores. The permeability of PTMSP to a five-component hydrocarbon/hydrogen mixture, similar to that found in refinery waste gas, was determined and compared with published permeation results for a 6-A microporous carbon membrane. PTMSP exhibited lower selectivities than those of the carbon membrane, but permeability coefficients in PTMSP were nearly three orders of magnitude higher. © 1996 John Wiley & Sons, Inc.

Infrared spectroscopy studies of the mechanism of the selective reduction of NOx over Cu-ZSM-5 catalysts

Abstract: The adsorption and subsequent reaction of nitric oxide, propene, molecular oxygen and combinations of these gases has been studied on samples of Cu-ZSM-5 catalysts of high activity in the selective reduction of NO by hydrocarbons, using infrared spectroscopy. When only propene is adsorbed, it first forms an adsorbed allyl and then undergoes stepwise oxidation to adsorbed acrolein, car☐ylic acid species and carbon oxides. Since no gas phase oxygen is present, these oxidations involve extra-lattice oxygen from the zeolite. These steps highlight the importance of small, oxygen containing copper clusters in the reaction. Exposure of a fresh catalyst to NO and propene results in the formation of an organic nitro compound, as well as the species observed for propene alone. No co-ordinated NO or dimeric species, of the sort that are important in the absence of hydrocarbon, are observed. Continued exposure of the nitro compound to propene results in the formation of nitrile species, which we have reported previously. Almost identical results are observed for the full gas mixture of propene, NO and oxygen, in helium. To probe the possible role of nitro species in the reaction pathway, the interaction of nitromethane with the catalyst has been studied. Nitromethane decomposes selectively, liberating nitrogen in the presence of oxygen over both Cu-ZSM-5 and H-ZSM-5 catalysts. We propose that organic nitro compounds are important intermediates in the reaction, and speculate on a decomposition pathway to nitrogen, based on known organic chemistry, which passes through azoxy or dinitroso species. Nitriles are proposed to form under reducing conditions, but these may also decompose on exposure to oxygen, liberating nitrogen.