Showing papers on "Hydrocarbon published in 1984"

The active site of acidic aluminosilicate catalysts

Abstract: The availability of solid acidic catalysts based on zeolite ZSM-5 make possible observations on the nature and the absolute rate behaviour of the individual protonic sites. Tetrahedral aluminium atoms are the highly reactive ingredients, even at levels of parts per million, or less. Turnover numbers for several hydrocarbon reactions equal and exceed familiar enzymatic turnover values. Intensive catalytic activities can result from aluminium levels likely to be ignored by the experimenter.

Liquid and supercritical carbon dioxide as organic solvents

Abstract: The nature of carbon dioxide in its liquid and supercritical states as a solvent for organic compounds was explored. Visible spectroscopy of solvatochromic dyes, ir spectroscopy of ketones and pyrrole, and the exo:endo ratio of a Diels-Alder reaction in CO/sub 2/ solutions were employed as probes of solvent polarity. For both liquid and supercritical CO/sub 2/, E/sub t/(30) similarly ordered 33.8 kcal/mol and Omega similarly 0.50; ..pi.. is near -0.5. Thus, CO/sub 2/ in these states behaves very much like a hydrocarbon solvent with very low polarizability. 52 references, 6 tables.

Process for the preparation of polyketones

Abstract: A process for the preparation of polyketones by polymerizing a mixture of CO and an alkenically unsaturated hydrocarbon in the presence of a Group VIII metal catalyst containing ligands, which comprise hydrocarbon groups that are bonded to an element from groub Vb, characterized in that, as catalyst, a complex compound is used that is obtained by reacting a palladium, cobalt or nickel compound, an anion of an acid with a pKa of less than 2, provided it is neither a hydrohalogenic acid nor carboxylic acid and a bidentate ligand of the general formula R 1 R 2 -M-R-M-R 3 R 4 , in which M represents phosphorus, arsenic or antimony, R represents a divalent organic bridging group having at least two carbon atoms in which the bridge, none of these carbon atoms carrying substituents that may cause steric hindrance and in which R 1 , R 2 , R 3 and R 4 are identical or different hydrocarbon groups.

Simultaneous recovery of crude from multiple zones in a reservoir

Abstract: A method for simultaneous recovery of crude oil from multiple zones in a reservoir is disclosed wherein multiple wells, each in fluid communication with at least two hydrocarbon zones separated by an impermeable barrier, are used to produce oil in an enhanced recovery process. The end product from recovery in one zone is used to augment the recovery process in another zone.

Carbon isotope composition of low molecular weight hydrocarbons and monocarboxylic acids from Murchison meteorite

Abstract: Carbon isotopic compositions have been measured for individual hydrocarbons and monocarboxylic acids from the Murchison meteorite, a C2 carbonaceous chondrite which fell in Australia in 1969. With few exceptions, notably benzene, the volatile products are substantially isotopically heavier than their terrestrial counterparts, signifying their extraterrestrial origin. For both classes of compounds, the ratio of C-13 to C-12 decreases with increasing carbon number in a roughly parallel manner, and each carboxylic acid exhibits a higher isotopic ratio than the hydrocarbon containing the same number of carbon atoms. These trends are consistent with the kinetically controlled synthesis of higher homologues from lower ones. The results suggest the possibility that the production mechanisms for hydrocarbons and carboxylic acids may be similar, and impose constraints on the identity of the reactant species.

Photocatalytic reactions of hydrocarbons and fossil fuels with water. Hydrogen production and oxidation

Abstract: Photocatalytic H/sub 2/ production from several aliphatic and aromatic compounds with water was investigated with powdered Pt/TiO/sub 2/ catalyst suspended in solution. Various fossil fuels such as coal, tar sand, and pitch also reacted with water, producing both H/sub 2/ and CO/sub 2/ from an early stage of irradiation. The photocatalytic oxidations of their model compounds, especially a linear hydrocarbon and benzene, were studied in the presence of silver ion as an electron acceptor. For aliphatic hydrocarbons, they are oxidized to alcohols, aldehydes, and carboxylic acids, successively. CO/sub 2/ was found to be formed through the photo-Kolbe type of reaction of carboxylic acids produced, which explained well the result of the complete decomposition of n-hexadecane. For benzene, we could detect phenol, catechol, hydroquinone, and muconic acid. On the basis of these results, the possibility of the direct oxidation of benzene by photogenerated holes and its ring-opening process peculiar to the photocatalytic reaction are discussed. The main reaction path for CO/sub 2/ production was suggested in which the benzene ring opens not by way of phenol and catechol, but by way of the intermediates whose reactivities are much larger than that of benzene. 41 references, 5 figures, 4 tables.

Heterogeneous photocatalytic reactions of organic acids and water. New reaction paths besides the photo-Kolbe reaction

Abstract: The heterogeneous photocatalytic reactions of acetic, propionic, and butyric acids were studied on several kinds of powdered semiconductors, mainly TiO/sub 2/. The influence of Ag/sup +/ as an electron acceptor, and the dependence of the reactions on the kind of semiconductor and pH, were investigated. The ratio of yields of hydrogen to hydrocarbon depends strongly on pH. At neutral or alkaline pH, hydrocarbon stops being evolved and only hydrogen is evolved. It is concluded that the pH dependence of the valence band position of the semiconductor and the concentration of OH/sup -/ ion control the reaction paths. From the pH dependence of methane production from acetic acid the valence band of anatase is estimated to be located more deeply by 0.1 eV than that of rutile. The results of product analysis and the complete decomposition of acetic acid to CO/sub 2/ show that there exist new reaction paths in which water is an oxidizing agent. Reaction schemes of these organic acids are proposed.

Generation and migration of light hydrocarbons.

Abstract: Light hydrocarbons (containing from 1 to 14 carbon atoms) are formed from disseminated organic matter in sediments at the parts-per-billion level by biological and low-temperature ( 50°C) cracking reactions. The cooler reactions produce mainly branched hydrocarbons, whereas the hotter reactions yield more straight chains. Hydrocarbon generation zones in the subsurface can be recognized on the basis of hydrocarbon distribution patterns. Hydrocarbons with tertiary carbon atoms form at lower temperatures than those with quaternary carbons. Methane and ethane migrate vertically through fine-grained shales by diffusion and solution, whereas many of the C3+ hydrocarbons show little or no vertical migration. Concentrations of light hydrocarbons, including methane, in fine-grained source rocks decrease to low values in deep, high-temperature (>200°C) sediments. This decrease may be one reason why no economic accumulation of gas has been found to date deeper than 8.2 kilometers (27,000 feet).

Effect of Water Washing on C15+ Hydrocarbon Fraction of Crude Oils from Northwest Palawan, Philippines

Abstract: Recognition and subsequent correlation of biodegraded and/or water-washed oils with their unaltered counterparts has been a long-recognized problem in petroleum geochemistry. Because water washing and biodegradation can occur concurrently, it is difficult to delineate the individual effects of these two oil-altering processes, especially on the C15+ hydrocarbon fraction. Both processes can cause an oil to become enriched in sulfur and to have a lower API gravity owing to loss of the more volatile components. Thus, the altered oil may appear to be a high-sulfur crude of low maturity. Altered and unaltered oil fractions extracted from cores of a water-washed carbonate reservoir offshore northwest Palawan were studied to observe the effect of alteration on correla ion parameters. Water washing resulted in the following changes: (1) depletion of 13C in the C15+ branched-cyclic alkane fraction, whereas virtually no change occurred in isotope composition of the aromatic fraction; (2) selective loss of dibenzothiophenes followed by loss of aromatic hydrocarbons; and (3) virtually no change in steranes or tricyclic and pentacyclic terpanes, with the exception of enhancement of 17^agr(H) norhopane and decrease of 18^agr(H) trisnorhopane. In situations of severe water washing, mild biodegradation also occurred, as indicated by the loss of n-alkanes (and possible selective loss of n-alkanes having less than 25 carbon atoms) relative to branched alkanes, cycloalkanes, and aromatic components. Because cycloalkanes and aromatic hydrocarbons are not generally preferentially utilized by bacteria as long as n-alkanes are present, the changes observed in these two fractions most likely result from water washing. Because of the potential for extreme compositional changes in the n-alkane and aromatic fractions, the most useful correlation parameters between the altered and unaltered oils are sterane and terpane distributions. Stable carbon isotope ratios are also useful; however, more studies of oils in which water washing is known to have occurred need to be made to explain the general response (or various responses) of the isotopic composition of oils to water washing.

Catalytic conversion of olefins to higher hydrocarbons

Abstract: CATALYTIC CONVERSION OF OLEFINS TO HIGHER HYDROCARBONS Abstract An improved continuous process for converting lower olefinic hydrocarbon feedstock to C5+ liquid hydrocarbons by contacting vapor phase olefinic feedstream with acid zeolite catalyst in the presence of recycled diluent stream rich in C3-C4 hydrocarbons in an enclosed reactor at elevated temperature and pressure. The improved technique comprises a system for cooling reactor effluent to recover a heavier hydrocarbon stream containing a mixture of C3-C4 hydrocarbons and C5+ hydrocarbons and debutanizing the heavier hydrocarbons below reactor pressure to obtain a C5+ product stream and a condensed C3-C4 hydrocarbon stream. Operating efficiencies are realized in the heat exchange system by reboiling the debutanized C5+ hydrocarbon product stream by heat exchange with hot reactor effluent, and by recycling and combining at least a portion of the condensed C3-C4 hydrocarbon stream to dilute the liquid olefin hydrocarbon feedstock. By increasing pressure on the liquid olefinic hydrocarbon feedstock and liquid recycle stream to at least the elevated reactor pressure in the liquid state prior to vaporization, energy is conserved. An apparatus arrangement for conducting such a process is also disclosed.

Sooting Correlations for Premixed Flames

Abstract: —Using a Bunsen-type burner in which the name temperature was controlled by nitrogen addition, the tendency of hydrocarbon fuels to form soot has been determined systematically. The effective sooting equivalence ratio reported is based on the stoichiometric relation in which the carbon and hydrogen in the fuel are converted to carbon monoxide and water. respectively, rather than the conventional equivalence ratio or the C/O ratio. The temperature effect is clearly shown by plotting the log of the effective equivalence ratio versus the reciprocal of the (adiabatic) flame temperature, and this dependency is similar for all fuels examined and is relatively weak. At a given flame temperature, an increase in either the number of carbon atoms or the C/H ratio in the fuel molecule increases the tendency to soot. These effects are attributed to the increased pyrolysis rate and the decreased oxidative attack, respectively. No significant effects are found with regard to the structure of the fuel molecule....

Relative gas-phase acidities of the alkanes

Abstract: : In the gas phase alkyl trimethyl silanes are cleaved by hydroxide ions to siloxides with loss of methane or alkane. The alkane to methane loss ratio in this reaction is proposed as a measure of the relative acidity of RH and CH4. A linear correlation is established for loss of substituents of known acidity (CH4, H2, C2H4, C6H6). This relationship allows the acidity of several alkanes to be predicted, as well as the electron affinity of the corresponding alkyl radicals. Ethane and the secondary position in propane are predicted to be less acidic than methane, and the ethyl, isopropyl and t-butyl radicals are predicted to have negative electron affinities.

Degradation of crude oil by a mixed population of bacteria isolated from sea-surface foams

Abstract: A mixed bacteria population (EM4) was isolated from foams formed on the surface of a zone chromically polluted by hydrocarbons (Gulf of Fos, French Mediterranean coast, October 1981). The population was able to degrade crude oil very effectively in the presence of sea water supplemented with nitrogen, phosphorus and iron. The percentage of hydrocarbon degradation was 81% at 30°C, pH 8, and partial oxygen pressure of 100%. After 12 d incubation, 92 and 83% of satured and aromatic compounds (mono-, di- and triaromatics) were degraded, respectively, as well as 63% of polar products and 48.5% of asphaltenes. Maximum degradation was attained at a sodium chloride concentration of between 400 and 800 mM with Population EM4, which is constituted of 8 strains, four of which are weak halophiles. Bacterial growth on hydrocarbons induces the production in the culture medium of surface-active agents which are able to emulsify the substrate. There is high specificity between the nature of the growth substrate and such emulsifying activity, particularly as far as petroleum is concerned: only the culture medium from Population EM4 is able to emulsify petroleum. These surface-active agents contain sugars and lipids (fatty acids, mono- and diglycerides). The foams, which always contain a high concentration of both hydrocarbons (100 to 180 mgl-1) and bacteria that are able to grow on these types of substrates, have a strong emulsifying activity. Our results would seem to demonstrate the importance of biosurfactants in the elimination of hydrocarbons from polluted biotopes.

Three-phase solid-liquid-gas equilibria for three carbon dioxide-hydrocarbon solid systems, two ethane-hydrocarbon solid systems, and two ethylene-hydrocarbon solid systems

Abstract: The pressure-temperature trace of the three-phase solid-liquid-gas curve starting at the melting point of the heavy solid and terminating at the upper critical end point was determined for CO/sub 2/-octacosane, CO/sub 2/-biphenyl, CO/sub 2/-naphthalene, ethane-octacosane, ethane-biphenyl, ethylene-octacosane, and ethylene-biphenyl. The results of this study are discussed in relation to previous studies of solid solubilities in supercritical fluids.

Heats of solution of gaseous hydrocarbons in water at 25°C

Abstract: The heats of solution at 25°C for a number of hydrocarbon gases are reported as measured by a calorimetric method. There is excellent agreement between the standard enthalpy changes of solution measured calorimetrically and those derived from high precision temperature dependent solubility measurements. However the calorimetrically determined standard enthalpies of solution of a number of gases are greatly improved over values obtained from low precision temperature dependent solubility measurements. A method is presented to readily estimate the standard errors in the standard enthalpy change for any process derived from the temperature dependence of the equilibrium constant for the process. Comparison of the standard enthalpies and entropies of solution of hydrocarbon gases in water shows that the standard free energies of solution for all hydrocarbon gases investigated are dominated by unfavorable entropy contributions. A strong linear correlation between the standard entropy of solution and the number of hydrogens in the hydrocarbon molecule is found. This correlation suggests that the hydrocarbon hydrophobic effect is regulated by the number of allowable configurations of a water molecule in contact with each C−H group.

Novel electrocatalytic procedure for the oxidation of alcohols, aldehydes, cyclic ketones, and carbon-hydrogen bonds adjacent to olefinic or aromatic groups

Abstract: Utilisation du complexe cationique [Ru(IV)(O)(terpyridine)(bipyridyle)] comme catalyseur pour l'oxydation electrocatalytique d'alcools, aldehydes, cyclohexanones, toluene dans des solutions aqueuses

Surface enhanced Raman vibrational studies at solid/gas interfaces

Abstract: Fundamentals of surface enhanced Raman scattering.- Experimental.- Pyridine adsorption.- Hydrocarbon adsorption.- Carbon monoxide exposure and carbonaceous deposits.- Oxygen exposure.- Water adsorption.- Other adsorbates.- Selected applications and related surface enhanced phenomena.- Summary and outlook.