Isomerization Of Hydrocarbons Research Articles

Quantum-chemical calculation of reactions involving concerted 1,2 migration of a CH3 group and 1,3(3,1)-H exchange in the propane molecule

1. Quantum-chemical calculation by the MINDO/3 method revealed the possibility of the occurrence of concerted 1,2 migration of a CH3 group and the less favorable 1,3(3,1)-H exchange in the propane molecule, which proceed through transition states of the pseudocyclopropane type. 2. The discovered principles of model intramolecular rearrangements in two- and threecarbon fragments are in agreement with the known experimental principles of thermocatalytic reactions involving the skeletal isomerization of saturated hydrocarbons.

The aromatization and isomerization of hydrocarbons and the thermal and subsidence history of the Nova Scotia margin : Mackenzie, A.S., C. Beaumont, R. Boutilier and J. Rullkötter, 1985. Phil. Trans. R. Soc., (A)315(1531):203–232

The aromatization and isomerization of hydrocarbons and the thermal and subsidence history of the Nova Scotia margin : Mackenzie, A.S., C. Beaumont, R. Boutilier and J. Rullkötter, 1985. Phil. Trans. R. Soc., (A)315(1531):203–232

Laboratory models for aromatization and isomerization of hydrocarbons in sedimentary basins

With increasing depth in the Earth's crust, changes take place in the sedimentary distributions of aromatic steroid hydrocarbons and of stereoisomers of certain types of alkanes1,2. The changes occur before and during the early stages of hydrocarbon generation and have been interpreted as resulting from aromatization and configurational isomerization reactions respectively3. We have now brought about an aromatization reaction and an isomerization reaction in the laboratory under free radical conditions, sulphur being chosen as a convenient source of radicals, and have extracted rate constants from the absolute concentration–time functions of the organic substrates. The activation energies and pre-exponential factors were then deduced from the temperature dependence of the rate coefficients. The values of these activation parameters show that, in the laboratory, the aromatization is more temperature dependent than the isomerization reaction, as suggested previously from the distributions of steroidal compounds in sedimentary basins3–5.

The aromatization and isomerization of hydro carbons and the thermal and subsidence history of the Nova Scotia margin

The temperature and burial histories of the sediments deposited on the continental margin off Nova Scotia have been modelled. A good match between predicted and observed present-day bottom-hole temperatures is only achieved when the thermal conductivities of sediments are derived from laboratory measurements of representative samples; values commonly quoted in the literature predict too low a geothermal gradient. The temperature history is used to predict the extents of geochemical reactions involving steroid hydrocarbons together with previously derived reaction constants. The reaction extents were measured on 33 samples. In general, agreement between observations and predictions is good. The reactions in some samples, however, appear to have progressed anomalously far for their depths. This is thought to be the result of impregnation of these sediments with oil, which has migrated from depth. The good general agreement between model predictions and observations encourages extrapolation of the model to areas of no sample control, and the reconstruction of the temperature and burial history of the margin. Tentative reconstruction of oil generation from the principal oil source rock of the region may also be attempted. The top of the oil-generation zone currently lies 4 km below the shallow regions of the continental shelf. Model predictions suggest that the Verrill Canyon formation and its equivalents are mature but that younger sediments are not. Maturation of deeper regions of the Verrill Canyon started in the Early Cretaceous, but significant volumes of sediment only entered the oil-generation zone during the Tertiary.

Isomerization of alkylaromatic hydrocarbons of aluminosilicate catalysts modified with composite compounds of nickel and copper: N. S. Kozlov, Ye. S. Osinovik, N. Ya. Pryakhina, G. M. Sen'kov and M. F. Gorbatse vich, Neftekhimiya 25, No. 2, 163–166, 1985

Isomerization of alkylaromatic hydrocarbons of aluminosilicate catalysts modified with composite compounds of nickel and copper: N. S. Kozlov, Ye. S. Osinovik, N. Ya. Pryakhina, G. M. Sen'kov and M. F. Gorbatse vich, Neftekhimiya 25, No. 2, 163–166, 1985

Isomerization and Aromatization of Hydrocarbons and the Paleothermometry and Burial History of Alberta Foreland Basin

The hydrocarbon fractions extracted from 34 Cretaceous shales from a cross section of the Alberta basin have been analyzed using gas chromatography-mass spectrometry. Particular attention has been paid to the extents to which three temperature-dependent geochemical reactions have occurred: isomerization of steranes at C-20; isomerization of hopanes at C-22; and aromatization of C-ring monoaromatic steroid hydrocarbons. Estimates of the kinetic constants of these reactions have been published previously; therefore, constraints may be put on the maximum temperature experienced by the sediments and the time for which this temperature existed. The subsidence history of the Alberta basin is simulated using a lithospheric flexural model in which the lithosphere is downwarped by the loading of overthrusts in the adjacent Cordilleran orogene. When overthrusting ceases, erosion of the overthrusted region lightens the load and the lithosphere rebounds, causing uplift and erosion of the foreland basin. Major overthrusting and therefore deep burial occurred during the Laramide orogeny of Late Cretaceous to mid-Tertiary time. The extent of chemical reactions suggests that the present maturity of the Cretaceous shales is almost entirely a reflection of burial and heating during the Laramide orogeny in a manner that is consistent with the lithospheric flexural model for the basin. The chemical reactions suggest that the paleogeothermal gradient increased systematically away from the foothills of the Rocky Mountains along the profile studied. That a similar trend exists today suggests this situation has persisted at least since the early stages of the Laramide orogeny. This variation is best explained by advective heat transfer. Water entering the basin in the faulted and topographically higher foothills is heated at depth, thereby depressing the geothermal gradient. This hot water then migrates updip and away from the foothills to enhance the geothermal gradients in the Edmonton area and beyond. The route of the migrating hot water is similar to that taken by hydrocarbons from Devonian and Cretaceous source rocks in the deep basin, updip to the oil and tar-sand accumulations of Alberta.

Polymeric phosphinocarborane Rh(I) complexes as catalysts for the hydrogenation and isomerization of unsaturated hydrocarbons

Polymeric phosphinocarborane Rh(I) complexes as catalysts for the hydrogenation and isomerization of unsaturated hydrocarbons

Catalytic isomerization of ethylenic hydrocarbons: XVIII. Effect of drying and reaction temperature on the isomerization of deuterated butenes over magnesium oxide

The isomerization of selectively deuterated cis-2-butenes was investigated at 60 and 250 °C on magnesium oxide predried between 300 and 550 °C. A rise in the drying temperature increases the number of active sites, but modifies neither their nature, nor their strength. The working temperature has a marked influence on the reactions observed. At 60 °C, magnesium oxide catalyzes only double-bond migration without exchange of hydrogen between the olefin and the catalyst; at 250 °C, a multiple exchange of hydrogen occurs during double-bond migration. In both cases the active sites are basic O 2− ions associated with weak acid Mg 2+ ions, but adjacent OH groups participate in the reaction at 250 °C. Some strong basic O 2− ions are also active at 250 °C, but they deactivate very rapidly: on these sites, double-bond migration and cis-trans isomerization, both without exchange, are observed.

Organic reactions as indicators of the burial and temperature histories of sedimentary sequences

AbstractThree organic reactions which affect individual compounds present in most organic-rich sedimentary rocks have been identified—configurational isomerization and aromatization of steroid hydrocarbons, and configurational isomerization of hopanes. The extents to which these reactions have occurred can be assessed by gas chromatographic-mass spectrometric analysis of the organic extracts of the sediment samples; they provide sensitive indicators of thermal maturation. When combined with the model of sedimentary basin formation by extension of the lithosphere, this molecular approach to the maturation of organic material can be used to constrain the temperature-time histories of sedimentary sequences. This temperature history may be used to integrate the relevant Arrhenius’ and rate equations governing the reaction rates. Each rate equation has three constants—the activation energy, frequency factor and the ratio of forward reaction to backward reaction. These have been estimated using analyses of samples whose temperature-time history is well constrained. The resulting estimates can then be used to reconstruct the temperature-time histories of other samples from organic geochemical data, e.g. calculation of the amount and timing of uplift.

Selectivity of iridium catalysts in reactions of C 6 hydrocarbons: The role of surface carbonaceous layers and metal particle size

Skeletal reactions of methylcyclopentane and hexane have been studied on Ir and the results are compared with earlier data on neohexane reactions. The conclusions are as follows: (1) Ir can catalyze the isomerization of hydrocarbons; (2) only under certain experimental conditions is the methylcyclopentane ring opening selective (“no” hexane); when covered by carbonaceous layers, Ir shows also a less selective ring opening. (3) the particle size dependence of the catalytic properties of Ir, as well as its sensitivity for self-poisoning, are much less pronounced than with Pt.

Isomerization and aromatization of hydrocarbons in sedimentary basins formed by extension

Summary. The reactions involved in oil generation are of great economic importance, but remain to be studied in detail. We have investigated the rates of three reactions which occur before and during the early stages of oil formation, and have used the predicted thermal and subsidence history of stretched basins to estimate the six reaction constants. Two of the reactions are isomerization reactions, at C-20 in a sterane and at C-22 in a hopane hydrocarbon. The third reaction converts C-ring monoaromatic to triaromatic steroid hydrocarbons. No single measure of maturity can describe the progress of these reactions. In old basins, such as the North Sea, both isomerization reactions are almost complete before appreciable aromatization has occurred, whereas in young basins, such as the Pannonian Basin in Hungary, aromatization is almost complete before appreciable isomerization of the steranes has occurred. We show that the calculated progress of these reactions agrees well with that observed in both basins if the frequency factors and activation energies are 6 x 10-3 s-1 and 91 kJ mol-1, 0.016 s-1 and 91 kJ mol-1, 1.8 x 1024 s-1 and 200 kJ mol-1 for the isomerization of steranes, of hopanes, and the aromatization of steroid hydrocarbons respectively. The rate of conversion of the R to the S form was taken to be 1.174 and 1.564 times that of the reverse reactions for sterane and hopane isomerizations respectively, and the aromatization reaction was assumed to be irreversible. All three reactions were assumed to be first order and unimolecular. The aromatization rate is consistent with laboratory observations. The rate of hopane isomerization is not, and different reaction mechanisms probably dominate at different temperatures. The same constants can be used to predict the progress of the reactions in basins which have been uplifted by inversion, such as the Lower Saxony Basin in West Germany. The geochemical observations provide estimates of the amount and time of uplift which agree with those from geological studies. Geochemical observations from the eastern part of the Paris Basin suggest that this region has also been uplifted by between 1 and 2 km.

Isomerization and aromatization of hydrocarbons in stretched sedimentary basins

We have calculated the progress of two reactions, both involving biological marker compounds, which occur in shales rich in organic matter. Both reactions are associated with the early stages of oil generation. One of these reactions is an isomerization reaction of a sterane1,2, the other involves the aromatization of monoaromatic steroid hydrocarbons3,4. Both reactions have recently been discussed by Mackenzie et al.5. We demonstrate that the observed progress of these reactions within two basins formed by extension, the North Sea and the Pannonian Basin, can be reproduced in some detail by a simple model of basin formation6. We used samples from basins formed by stretching the lithosphere because both the subsidence history and the variation of heat flux with time is principally controlled by the amount of extension6–10. In contrast the subsidence of the other major class of sedimentary basins, which are formed by flexure of the continental lithosphere11–13, can only be modelled when the geological history of the region is known in detail13, and such models do not constrain the history of the heat flux.

Isomerization of hydrocarbons in the presence of zeolite-containing catalysts

Summaryo1.Y-type zeolites with 97% of the sodium removed and after aluminium removal (modulus close to 8) and without precious metal activation—are active and fairly selective catalysts for the isomerization of paraffinic and naphthenic hydrocarbons at 200°–280°C.2.The isomerization activity of HY and HM zeolites correlates with the concentration of strong acid sites; the isomerization of paraffins requires stronger centres sites than are needed for the isomerization of naphthenes.3.HY Catalysts may be used for increasing the octane number of refined oils in catalytic reforming Y-type zeolites with 97% of the sodium removed and after aluminium removal (modulus close to 8) and without precious metal activation—are active and fairly selective catalysts for the isomerization of paraffinic and naphthenic hydrocarbons at 200°–280°C. The isomerization activity of HY and HM zeolites correlates with the concentration of strong acid sites; the isomerization of paraffins requires stronger centres sites than are needed for the isomerization of naphthenes. HY Catalysts may be used for increasing the octane number of refined oils in catalytic reforming

ChemInform Abstract: ORGANIC PHOTOCHEMISTRY. 55. VALENCE ISOMERIZATION OF C9H10 HYDROCARBONS: PHOTOCHEMICAL REACTIONS OF BICYCLO(3.2.2)NONA‐2,6,8‐TRIENE AND ITS DIHYDRO‐DERIVATIVES

Chemischer InformationsdienstVolume 13, Issue 12 Preparative Organic Chemistry ChemInform Abstract: ORGANIC PHOTOCHEMISTRY. 55. VALENCE ISOMERIZATION OF C9H10 HYDROCARBONS: PHOTOCHEMICAL REACTIONS OF BICYCLO(3.2.2)NONA-2,6,8-TRIENE AND ITS DIHYDRO-DERIVATIVES T. KUMAGAI, T. KUMAGAISearch for more papers by this authorK. SHIMIZU, K. SHIMIZUSearch for more papers by this authorH. TSURUTA, H. TSURUTASearch for more papers by this authorT. MUKAI, T. MUKAISearch for more papers by this author T. KUMAGAI, T. KUMAGAISearch for more papers by this authorK. SHIMIZU, K. SHIMIZUSearch for more papers by this authorH. TSURUTA, H. TSURUTASearch for more papers by this authorT. MUKAI, T. MUKAISearch for more papers by this author First published: March 23, 1982 https://doi.org/10.1002/chin.198212143Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume13, Issue12March 23, 1982 RelatedInformation

ADSORPTION ISOTHERMS AND CATALYST SELECTIVITY FOR A UNIFORM SURFACE: THE ROLE OF MULTIPLE LANDING AREAS

In general a gas phase species can be present simultaneously in more than one adsorbed form on a uniform solid surface. The different adsorbed forms tie up different combinations of surface sites. Each such combination is termed a landing area. The different adsorbed forms present on the surface of a catalyst may form different products. (In the more general case, each different adsorbed form yields a different distribution of a set of products.) Hence the relative amount of each adsorbed form and landing area present on the surface determines the selectivity of the solid catalyst. The variation of the landing area distribution with temperature and partial pressure of the gas phase species is examined in the first part of this work. In general, increasing the pressure or decreasing the temperature leads to the relative decrease of molecules adsorbed on landing areas consisting of larger number of sites and the relative increase of molecules adsorbed on smaller landing areas. The kinetics of metal catalyzed skeletal isomerization and hydrogenoly-sis of hydrocarbons on supported metal catalysts is examined in the framework of the landing area in the second part of this work. A simple model for the variation of reaction order with pressure agrees with experimental data from other laboratories.

温州ミカンの貯蔵臭に関する研究 ＶＩ

Quantitative changes in various terpene hydrocarbons (α-pinene [1], β-pinene [2], myrcene [3], d-limonene [4], γ-terpinene [5]) were studied in Satsuma Mandarin juice during storage. Compound [1] yielded α-terpineol [6] and β-terpineol [7] as hydration products. Hydration of [2] yielded [6] as the main product and fenchyl alcohol [8] as the minor product. Terpinen-4-ol [9], [6] and [7] were produced from [4]. Compounds [3] and [5] were quite stable in the juice. Isomerization of terpene hydrocarbons [1_??_5] was also observed. Further-more, the precursors and formation mechanisms of the off-flavored compounds [6, 7, 8] of the juice were suggested.

Mechanism of isomerization of hydrocarbons on metals. Part 9.—Isomerization and dehydrocyclization of 2,3-dimethyl[2-13C]pentane on a 10 % Pt–Al2O3 catalyst

The isomerization, dehydrocyclization and hydrogenolysis of 2,3-dimethyl[2-13C]pentane have been studied at 260°C over a 10 % Pt–Al2O3 catalyst of low dispersion, under various hydrocarbon and hydrogen pressures. Most of the isomerization products are accounted for either by a bondshift mechanism or by a cyclic mechanism involving 1,2-dimethylcyclopentane intermediate. The absence of significant scrambling of the label suggests that the rate-determining step in isomerization is the skeletal rearrangement of highly dehydrogenated species. The positive order as a function of hydrogen which is found (0.8–1.2) cannot then be taken as evidence that desorption is rate-determining. It is best explained by assuming multisite adsorption of hydrocarbon and competition with hydrogen for chemisorption on the same sites. The results provide argument in favour of a reactive rather than dissociative-type adsorption step.

Mechanism of isomerization of hydrocarbons on metals. Part 10.—Isomerization and dehydrocyclization of 2-methyl[2-13C]hexane on a 10 % Pt–Al2O3 catalyst

The contact reactions of 2-methyl[2-13C]hexane and 2-methyl[6-13C]hexane have been investigated at 270 and 360°C, respectively, over a 10% Pt–Al2O3 catalyst. The isomerizations of 2-methylhexane and 2,3-dimethylpentane, at 270°C, are very similar: the orders as a function of hydrogen are positive (0.2–1.75) and all the products are obtained by a one-step process according to either a bond-shift or a cyclic mechanism (the latter being predominant). The positive order, together with the absence of scrambling, is consistent with Frennet's model, assuming hydrocarbon adsorption on several contiguous metal sites.

Mechanisms of isomerization of hydrocarbons on metals. Part 11.—Isomerization and dehydrocyclization of 13C-labelled 3-methylhexanes on Pt–Al2O3 catalysts

The isomerization, dehydrocyclization and hydrogenolysis of 3-methylhexane have been studied at 320–380°C over a series of Pt–Al2O3 catalysts with a metal dispersion extending from 0.05 to 1. The use of five labelled compounds, 3-methyl[1-13C], [2-13C], [3-13C], [6-13C]hexanes and 3-methyl-[13C]hexane, allowed distinction between the various parallel pathways.On all catalysts the predominant reaction was the isomerization according to a cyclic mechanism involving either 1,3-dimethyl-, 1,2-dimethyl- or ethyl-cyclopentane intermediates with a relative contribution of 60, 40 and 20 %, respectively. These results are consistent with a dehydrocyclization scheme involving a metallocarbene as precursor and dicarbene or dicarbyne recombination as the rate-determining step.

8,16‐Methano[2.2]metacyclophane‐1,9‐diene. A Valence Isomer of 10b,10c‐Methano‐cis‐10b, 10c‐dihydropyrene

Laws governing the valence isomerization of polycyclic hydrocarbons have hardly been recognized so far; surprisingly, the new system (2), unlike (1), exists only as the “methano” isomer. The “cyclopropanetetrayl” isomer of (2) is postulated as intermediate in rearrangements.