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Littérature scientifique sur le sujet « Alkanes »

Auteur : Grafiati

Publié le 4 juin 2021

Mis à jour le 30 juillet 2024

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Articles de revues sur le sujet "Alkanes"

Koch, Daniel J., Mike M. Chen, Jan B. van Beilen et Frances H. Arnold. « In Vivo Evolution of Butane Oxidation by Terminal Alkane Hydroxylases AlkB and CYP153A6 ». Applied and Environmental Microbiology 75, n^o 2 (14 novembre 2008) : 337–44. http://dx.doi.org/10.1128/aem.01758-08.

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ABSTRACT Enzymes of the AlkB and CYP153 families catalyze the first step in the catabolism of medium-chain-length alkanes, selective oxidation of the alkane to the 1-alkanol, and enable their host organisms to utilize alkanes as carbon sources. Small, gaseous alkanes, however, are converted to alkanols by evolutionarily unrelated methane monooxygenases. Propane and butane can be oxidized by CYP enzymes engineered in the laboratory, but these produce predominantly the 2-alkanols. Here we report the in vivo-directed evolution of two medium-chain-length terminal alkane hydroxylases, the integral membrane di-iron enzyme AlkB from Pseudomonas putida GPo1 and the class II-type soluble CYP153A6 from Mycobacterium sp. strain HXN-1500, to enhance their activity on small alkanes. We established a P. putida evolution system that enables selection for terminal alkane hydroxylase activity and used it to select propane- and butane-oxidizing enzymes based on enhanced growth complementation of an adapted P. putida GPo12(pGEc47ΔB) strain. The resulting enzymes exhibited higher rates of 1-butanol production from butane and maintained their preference for terminal hydroxylation. This in vivo evolution system could be useful for directed evolution of enzymes that function efficiently to hydroxylate small alkanes in engineered hosts.

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Funhoff, Enrico G., Ulrich Bauer, Inés García-Rubio, Bernard Witholt et Jan B. van Beilen. « CYP153A6, a Soluble P450 Oxygenase Catalyzing Terminal-Alkane Hydroxylation ». Journal of Bacteriology 188, n^o 14 (15 juillet 2006) : 5220–27. http://dx.doi.org/10.1128/jb.00286-06.

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ABSTRACT The first and key step in alkane metabolism is the terminal hydroxylation of alkanes to 1-alkanols, a reaction catalyzed by a family of integral-membrane diiron enzymes related to Pseudomonas putida GPo1 AlkB, by a diverse group of methane, propane, and butane monooxygenases and by some membrane-bound cytochrome P450s. Recently, a family of cytoplasmic P450 enzymes was identified in prokaryotes that allow their host to grow on aliphatic alkanes. One member of this family, CYP153A6 from Mycobacterium sp. HXN-1500, hydroxylates medium-chain-length alkanes (C6 to C11) to 1-alkanols with a maximal turnover number of 70 min−1 and has a regiospecificity of ≥95% for the terminal carbon atom position. Spectroscopic binding studies showed that C6-to-C11 aliphatic alkanes bind in the active site with Kd values varying from ∼20 nM to 3.7 μM. Longer alkanes bind more strongly than shorter alkanes, while the introduction of sterically hindering groups reduces the affinity. This suggests that the substrate-binding pocket is shaped such that linear alkanes are preferred. Electron paramagnetic resonance spectroscopy in the presence of the substrate showed the formation of an enzyme-substrate complex, which confirmed the binding of substrates observed in optical titrations. To rationalize the experimental observations on a molecular scale, homology modeling of CYP153A6 and docking of substrates were used to provide the first insight into structural features required for terminal alkane hydroxylation.

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Jacobs, Cheri Louise, Rodolpho do Aido-Machado, Carmien Tolmie, Martha Sophia Smit et Diederik Johannes Opperman. « CYP153A71 from Alcanivorax dieselolei : Oxidation beyond Monoterminal Hydroxylation of n-Alkanes ». Catalysts 12, n^o 10 (11 octobre 2022) : 1213. http://dx.doi.org/10.3390/catal12101213.

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Selective oxyfunctionalization of non-activated C–H bonds remains a major challenge in synthetic chemistry. The biocatalytic hydroxylation of non-activated C–H bonds by cytochrome P450 monooxygenases (CYPs), however, offers catalysis with high regio- and stereoselectivity using molecular oxygen. CYP153s are a class of CYPs known for their selective terminal hydroxylation of n-alkanes and microorganisms, such as the bacterium Alcanivorax dieselolei, have evolved extensive enzymatic pathways for the oxyfunctionalization of various lengths of n-alkanes, including a CYP153 to yield medium-chain 1-alkanols. In this study, we report the characterization of the terminal alkane hydroxylase from A. dieselolei (CYP153A71) for the oxyfunctionalization of medium-chain n-alkanes in comparison to the well-known CYP153A6 and CYP153A13. Although the expected 1-alkanols are produced, CYP153A71 readily converts the 1-alkanols to the corresponding aldehydes, fatty acids, as well as α,ω-diols. CYP153A71 is also shown to readily hydroxylate medium-chain fatty acids. The X-ray crystal structure of CYP153A71 bound to octanoic acid is solved, yielding an insight into not only the regioselectivity, but also the binding orientation of the substrate, which can be used in future studies to evolve CYP153A71 for improved oxidations beyond terminal n-alkane hydroxylation.

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Mayes, R. W., C. S. Lamb et Patricia M. Colgrove. « The use of dosed and herbage n-alkanes as markers for the determination of herbage intake ». Journal of Agricultural Science 107, n^o 1 (août 1986) : 161–70. http://dx.doi.org/10.1017/s0021859600066910.

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SUMMARYThe recovery in the faeces of the n-alkanes of herbage (odd-chain, C27–C35) and of dosed artificial alkanes (even-chain, C28 and C32) was studied in twelve 4-month-old castrated male lambs. The lambs received three levels of cut, fresh perennial ryegrass or a mixed diet of perennial ryegrass (0·70) and a barley-based concentrate (0·30) (500–900 g D.M./day). C28 and C32 n-alkanes (130 mg each), absorbed onto shredded paper, were given once daily for 17 days to test whether the recoveries of herbage and dosed alkanes were similar to enable their use as markers for determining the herbage intake of grazing sheep. Stearic and palmitic acids (130 mg each) were given with the dosed alkanes to half of the animals with the objective of facilitating emulsification of the dosed alkanes within the digestive tract.With the exception of C27 n-alkane, the faecal recoveries of all alkanes were unaffected by diet, feeding level or emulsifying agent. Faecal recovery of odd- chain herbage n-alkanes increased with increasing C-chain length. The recovery of the dosed C28 n-alkane was slightly greater than the recoveries of both C27, and C29 n-alkanes of herbage. The recoveries of the dosed C32 n-alkane and the herbage C33-alkane were the same.The mean herbage intake estimated using C33 and C32 n-alkanes was identical to the actual herbage intake. Other alkane pairs gave slight underestimates of herbage intake ranging from 3·5% for the C28–C29 pair to 7·6% for the C27–C28 pair. No cyclical pattern of n-alkane excretion throughout the day was observed. Examination of daily variations in faecal alkane concentrations indicated that the start of alkane dosing should precede the sampling of faeces by at least 6 days.These results suggest that accurate estimation of herbage intake in grazing sheep is possible from the simultaneous use of dosed C32 and herbage C33 n-alkanes as markers.The method may be particularly useful in enabling unbiased estimates of herbage intake to be made in animals receiving supplementary feed.

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Gołębiowski, M., M. Paszkiewicz, A. Grubba, D. Gąsiewska, M. I. Boguś, E. Włóka, W. Wieloch et P. Stepnowski. « Cuticular and internal n-alkane composition of Lucilia sericata larvae, pupae, male and female imagines : application of HPLC-LLSD and GC/MS-SIM ». Bulletin of Entomological Research 102, n^o 4 (25 janvier 2012) : 453–60. http://dx.doi.org/10.1017/s0007485311000800.

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AbstractThe composition of cuticular and internal n-alkanes in Lucilia sericata larvae, pupae, and male and female imagines were studied. The cuticular and internal lipid extracts were separated by HPLC-LLSD, after which the hydrocarbon fraction was identified by GC/MS in selected ion monitoring (SIM) and total ion current (TIC) modes.The cuticular lipids of the larvae contained seven n-alkanes from C23 to C31. The major n-alkane in L. sericata larvae was C29 (42.1%). The total cuticular n-alkane content in the cuticular lipids was 31.46 μg g−1 of the insect body. The internal lipids of L. sericata larvae contained five n-alkanes ranged from C25 to C31. The most abundant compound was C27 (61.71 μg g−1 of the insect body). Eighteen n-alkanes from C14 to C31 were identified in the cuticular lipids of the pupae. The most abundant n-alkanes ranged from C25 to C31; those with odd-numbered carbon chains were particularly abundant, the major one being C29:0 (59.5%). Traces of eight cuticular n-alkanes were present. The internal lipids of L. sericata pupae contained five n-alkanes, ranging from C25 to C31. The cuticular lipids of female imagines contained 17 n-alkanes from C12 to C30. Among the cuticular n-alkanes of females, C27 (47.5%) was the most abundant compound. Four n-alkanes, with only odd-numbered carbon chains, were identified in the internal lipids of females. The lipids from both sexes of L. sericata had similar n-alkane profiles. The cuticular lipids of adult males contained 16 n-alkanes ranging from C13 to C31. C27 (47.9%) was the most abundant cuticular n-alkanes in males. The same n-alkanes only with odd-numbered carbon chains and in smaller quantities of C27 (0.1%) were also identified in the internal lipids of males.The highest amounts of total cuticular n-alkanes were detected in males and females of L. sericata (330.4 and 158.93 μg g−1 of the insect body, respectively). The quantities of total cuticular alcohols in larvae and pupae were smaller (31.46 μg g−1 and 42.08 μg g−1, respectively). The internal n-alkane contents of larvae, pupae, and male and female imagines were significantly higher than the cuticular n-alkane contents (153.53, 99.60, 360.06 and 838.76 μg g−1 of the insect body, respectively).

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Madhu, Azad, Myoseon Jang et Yujin Jo. « Modeling the influence of carbon branching structure on secondary organic aerosol formation via multiphase reactions of alkanes ». Atmospheric Chemistry and Physics 24, n^o 9 (15 mai 2024) : 5585–602. http://dx.doi.org/10.5194/acp-24-5585-2024.

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Abstract. Branched alkanes represent a significant proportion of hydrocarbons emitted in urban environments. To accurately predict the secondary organic aerosol (SOA) budgets in urban environments, these branched alkanes should be considered as SOA precursors. However, the potential to form SOA from diverse branched alkanes under varying environmental conditions is currently not well understood. In this study, the Unified Partitioning Aerosol Phase Reaction (UNIPAR) model is extended to predict SOA formation via the multiphase reactions of various branched alkanes. Simulations with the UNIPAR model, which processes multiphase partitioning and aerosol-phase reactions to form SOA, require a product distribution predicted from an explicit gas kinetic mechanism, whose oxygenated products are applied to create a volatility- and reactivity-based αi species array. Due to a lack of practically applicable explicit gas mechanisms, the prediction of the product distributions of various branched alkanes was approached with an innovative method that considers carbon lengths and branching structures. The αi array of each branched alkane was primarily constructed using an existing αi array of the linear alkane with the nearest vapor pressure. Generally, the vapor pressures of branched alkanes and their oxidation products are lower than those of linear alkanes with the same carbon number. In addition, increasing the number of alkyl branches can also decrease the ability of alkanes to undergo autoxidation reactions that tend to form low-volatility products and significantly contribute to alkane SOA formation. To account for this, an autoxidation reduction factor, as a function of the degree and position of branching, was applied to the lumped groups that contain autoxidation products. The resulting product distributions were then applied to the UNIPAR model for predicting branched-alkane SOA formation. The simulated SOA mass was compared to SOA data generated under varying experimental conditions (i.e., NOx levels, seed conditions, and humidity) in an outdoor photochemical smog chamber. Branched-alkane SOA yields were significantly impacted by NOx levels but insignificantly impacted by seed conditions or humidity. The SOA formation from branched and linear alkanes in diesel fuel was simulated to understand the relative importance of branched and linear alkanes with a wide range of carbon numbers. Overall, branched alkanes accounted for a higher proportion of SOA mass than linear alkanes due to their higher contribution to diesel fuel.

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Shu, Bin, Lijun Lin, Yingjun Zhang, Hai Wang et Hailing Luo. « N-alkane profiles of common rangeland species in northern China and the influence of drying method on their concentrations ». Canadian Journal of Plant Science 88, n^o 1 (1 janvier 2008) : 137–41. http://dx.doi.org/10.4141/cjps07008.

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Plant wax alkanes have been used as internal markers to estimate diet composition of grazing animals. However, alkane contents in samples may vary depending on the drying method used. This study was undertaken to determine the alkane profiles and concentrations of 17 common range land species in northern China with two different drying methods. The results showed that regardless of drying methods, the odd-chain alkanes, particular C29 and C33, predominated in cuticular wax in all 17 common species and their component plant parts. The alkane patterns of plant species within the same genus were relatively similar and the differences in alkanes between stem and leaf were generally smaller than those between inflorescences and leaf or stem. The influence of drying methods on alkane concentrations varied depending on family and individual alkane. The effect of drying methods on C29 seemed to be smaller than other alkanes in all the samples. The oven-dry method produced higher concentrations (P < 0.05) in the three major alkanes (C23, C31 and C33) in the Gramineae family than the freeze-dry method. Therefore, studies dealing with alkane concentrations should use the same drying method for all samples. Key words: Alkane pattern, steppe grassland, oven-dry, freeze-dry

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Yang, Jiyuan, Guoyang Lei, Chang Liu, Yutong Wu, Kai Hu, Jinfeng Zhu, Junsong Bao, Weili Lin et Jun Jin. « Characteristics of particulate-bound n-alkanes indicating sources of PM_2.5 in Beijing, China ». Atmospheric Chemistry and Physics 23, n^o 5 (7 mars 2023) : 3015–29. http://dx.doi.org/10.5194/acp-23-3015-2023.

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Abstract. The characteristics of n-alkanes and the contributions of various sources of fine particulate matter (PM2.5) in the atmosphere in Beijing were investigated. PM2.5 samples were collected at Minzu University of China between November 2020 and October 2021, and n-alkanes in the samples were analyzed by gas chromatography mass spectrometry. A positive matrix factorization analysis model and source indices (the main carbon peaks, carbon preference indices, and plant wax contribution ratios) were used to identify the sources of n-alkanes, to determine the contributions of different sources, and to explain the differences. The n-alkane concentrations were 4.51–153 ng m−3 (mean 32.7 ng m−3), and the particulate-bound n-alkane and PM2.5 concentrations varied in parallel. There were marked seasonal and diurnal differences in the n-alkane concentrations (p<0.01). The n-alkane concentrations in the different seasons decreased in the order of winter > spring > summer > fall. The mean concentration of each homolog was higher at night than in the day in all seasons. Particulate-bound n-alkanes were supplied by common anthropogenic and biogenic sources, and fossil fuel combustion was the dominant contributor. The positive matrix factorization model results indicated five sources of n-alkanes in PM2.5, which were coal combustion, diesel vehicle emissions, gasoline vehicle emissions, terrestrial plant release, and mixed sources. Vehicle emissions were the main sources of n-alkanes, contributing 57.6 %. The sources of PM2.5 can be indicated by n-alkanes (i.e., using n-alkanes as organic tracers). Vehicle exhausts strongly affect PM2.5 pollution. Controlling vehicle exhaust emissions is key to controlling n-alkanes and PM2.5 pollution in Beijing.

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Boadi, D. A., S. A. Moshtaghi Nia, K. M. Wittenberg et W. P. McCaughey. « The n-alkane profile of some native and cultivated forages in Canada ». Canadian Journal of Animal Science 82, n^o 3 (1 septembre 2002) : 465–69. http://dx.doi.org/10.4141/a01-084.

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Frage samples were collected from swards growing in Carberry, Manitoba, Brandon, Manitoba, Saskatoon, Saskatchewan, and St. John’s, Newfoundland, and the alkane concentrations were determined by gas chromatography. Considerable differences were observed in almost all odd-numbered alkanes and in their total content between species. The odd-numbered alkanes were always present in high concentrations compared to the even-chain alkanes in both native and cultivated species. Of the cultivated grasses, the fescues had very high concentrations of CN31 among the odd-chain alkanes, while the legumes tended to have higher concentrations of C29 than C31 or C33. The low concentrations of odd-chain alkanes (< 50 mg kg-1 DM) in little bluestem, indiangrass, reed canarygrass, orchardgrass, timothy and Russian wildrye forages could bias intake calculations of these forages when the double alkane technique is used. Differences between location and cultivar were observed for C29 in timothy and C31 in meadow bromegrass (P < 0.05). There were no effects of location and cultivar on n-alkane concentrations for orchardgrass (P > 0.05). Key words: n-alkanes, forage species, cultivar, location

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Baldwin, Robert L., et George D. Rose. « How the hydrophobic factor drives protein folding ». Proceedings of the National Academy of Sciences 113, n^o 44 (17 octobre 2016) : 12462–66. http://dx.doi.org/10.1073/pnas.1610541113.

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How hydrophobicity (HY) drives protein folding is studied. The 1971 Nozaki–Tanford method of measuring HY is modified to use gases as solutes, not crystals, and this makes the method easy to use. Alkanes are found to be much more hydrophobic than rare gases, and the two different kinds of HY are termed intrinsic (rare gases) and extrinsic (alkanes). The HY values of rare gases are proportional to solvent-accessible surface area (ASA), whereas the HY values of alkanes depend on special hydration shells. Earlier work showed that hydration shells produce the hydration energetics of alkanes. Evidence is given here that the transfer energetics of alkanes to cyclohexane [Wolfenden R, Lewis CA, Jr, Yuan Y, Carter CW, Jr (2015) Proc Natl Acad Sci USA 112(24):7484–7488] measure the release of these shells. Alkane shells are stabilized importantly by van der Waals interactions between alkane carbon and water oxygen atoms. Thus, rare gases cannot form this type of shell. The very short (approximately picoseconds) lifetime of the van der Waals interaction probably explains why NMR efforts to detect alkane hydration shells have failed. The close similarity between the sizes of the opposing energetics for forming or releasing alkane shells confirms the presence of these shells on alkanes and supports Kauzmann's 1959 mechanism of protein folding. A space-filling model is given for the hydration shells on linear alkanes. The model reproduces the n values of Jorgensen et al. [Jorgensen WL, Gao J, Ravimohan C (1985) J Phys Chem 89:3470–3473] for the number of waters in alkane hydration shells.

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Thèses sur le sujet "Alkanes"

Khalil, Enam A. S. A. « A thermodynamic study of binary and ternary mixtures of some alkanes and alkanols ». Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328889.

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Løften, Thomas. « Catalytic isomerization of light alkanes ». Doctoral thesis, Norwegian University of Science and Technology, Department of Chemical Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1909.

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In recent years the levels of sulfur and benzene in the gasoline pool have been reduced, and in the future there may also be new regulations on vapor pressure and the level of aromatics and olefins as well. The limitations on vapor pressure and aromatics will lead to reduced use of C₄ and reformate respectively. The branched isomers of C₅ and C₆ alkanes have high octane numbers compared to the straight chain isomers, and are consequently valuable additives to the gasoline pool. To maintain the octane rating, it is predicted that an increased share of isomerate will be added to the gasoline pool.

Today there is a well established isomerization technology with platinum on chlorided alumina as the commercial catalyst for both isomerization of n-butane and of the C₅/C₆ fraction. This catalyst is very sensitive to catalyst poisons like water and sulfur, and strict feed pretreatment is required. Zeolites promoted by platinum are alternatives as isomerization catalysts, and has replaced Pt/alumina catalysts to some extent. The Pt/zeolite catalyst is more resistant to water and sulfur compounds in the feed, but it is less active than platinum on chlorided alumina. It does therefore require a higher reaction temperature, which is unfortunate since the formation of the branched isomers of the alkanes is thermodynamically favored by a low temperature.

Because of the limitations of the two types of isomerization catalysts, there is a search for a new catalyst that is resistant to sulfur and water in the feed and is highly active so it can be operated at low temperature. A new type of catalyst that seems to be promising in that respect is sulfated zirconia.

The first part of this study focuses on a series of iron and manganese promoted SZ catalysts. The catalysts were characterized by various techniques such as XRD, TGA, N₂adsorption and IR spectroscopy of adsorbed pyridine. The catalytic activity in n-butane isomerization at 250°C and atmospheric pressure was compared to the physical and chemical properties of the samples. No promoting effect of iron and manganese was found when n-butane was diluted in nitrogen. When nitrogen was replaced by hydrogen as the diluting gas the activity of the unpromoted SZ sample was dramatically lowered, while the activity of the promoted catalyst was not significantly changed.

If we only consider the promoted samples, the catalytic activity increases with increasing iron/manganese ratio. We also observe that the activity of the samples is clearly correlated with the number of strong Brønsted acid sites. The total number of strong acid sites (i.e. the sum of Brønsted and Lewis sites) does not change significantly when the promoter content is changing, hence no correlation between catalytic activity and the total number of acid sites is found. This underlines the importance of discrimination between Lewis and Brønsted acidity when characterizing the acidity of the samples.

The second part of this study is focused on a series of noble metal promoted sulfated zirconia. Their catalytic activity in n-hexane isomerization at high pressures was compared to a commercial Pt/zeolite catalyst. Among the noble metal promoted samples the catalyst promoted with platinum was the most active. The samples promoted with rhodium, ruthenium and iridium showed equal activity.

Common for all the noble metal promoted catalysts is the large increase in activity when catalysts are reduced with hydrogen compared to when they are pretreated in helium. The increase in activity is most likely connected to the reduction of the metal oxides of the promoters to ensure that the promoters are in the metallic state. Reduction at too high temperatures does however give lower activity. This is probably due to the reduction of surface sulfate groups leading to a loss in acid sites.

The commercial sample was considerably less active than the sample of platinum promoted sulfated zirconia. The commercial catalyst was however more stable than the PtSZ catalyst. All the sulfated zirconia catalysts deactivated, but the initial activity could be regenerated by reoxidation at 450°C followed by reduction at 300°C. The promotion with noble metals appears to inhibit coke formation on the catalyst. But, the main cause of deactivation of the platinum promoted sample is most likely the reduction of sulfate species leading to a loss of acid sites.

The kinetic study of the catalysts indicates that the n-hexane isomerization proceeds via a classical bifunctional mechanism where the role of the promoting metal is to produce alkenes, which are subsequently protonated on the acid sites. The reaction orders of hydrogen, n-hexane and total pressure are all in accordance with this mechanism. The activation energies of the catalysts are within the typical range of bifunctional catalysts.

All catalysts, except the unpromoted SZ sample, showed close to 100% selectivity to branched hexane isomers and a similar distribution of these isomers. The isomer distribution being the same for both the noble metal promoted catalyst and the Pt/zeolite is another indication that the isomerization proceeds via the bifunctional mechanism over the promoted samples. The different selectivity of the unpromoted SZ catalyst indicates that the isomerization proceeds via a different pathway over this catalyst; this is probably a pure acidic mechanism

The acidity characterization can not explain the differences in isomerization activity. It is however likely that the activity of the promoting metals in the dehydrogenation of alkanes is important since the classical bifunctional mechanism is prevailing.

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Pongtavornpinyo, Ruti. « Indium Carbenes Alkenes and Alkanes ». Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508494.

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Marozzelli, Filippo. « Alkanes activation over oxide catalysts ». Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/60089/.

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The basics of the oxidation mechanism of different alkanes within zeolites and over molybdenum oxide surfaces were studied employing state of the art computational modelling. It was shown that the constrained environment inside MFI, MFS and MOR induces terminal selectivity on the reaction of 6-, 8- and 10- term linear alkanes, i.e. hexane, octane and decane, respectively. The Monte Carlo (MC) random alkane configuration sampling showed that the oxidation reactivity is driven by the fact that the terminal C atoms of the substrate are more likely to be closer to the zeolites internal walls than the methylene (–CH2–) C atoms. As a confirmation of this, the calculation of kprim/ksec for all the host/guest (alkane/zeolite) systems estimated that the pore effect exerted by the zeolites in the reaction favors terminal products (terminal selectivity). The alkane oxidation over MoO3(010), Fe2(MoO4)3(001) and (110) surfaces involved the activation of a C–H bond of the substrate. The surface calculations were carried out using DFT+U to localize the electrons at a terminal point of the surface. Energy comparison with hybrid DFT (B3LYP) calculations for cluster models of the MoO3(010) surface showed consistency with the DFT+U results. The propane terminal C–H bond activation generated a propyl radical. Transition state structures were found for the adsorption of radical species on MoO3(010) and Fe2(MoO4)3(001) surface and the corresponding energy barriers showed that the adsorption on the former system is favored, which indicates that the Fe2(MoO4)3 surface alone is not a good catalyst for the reaction studied.

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ZHENG, TAO. « MOLECULAR SIMULATION OF DIFFUSION AND SORPTION OF ALKANES AND ALKANE MIXTURES IN POLY[1-(TRIMETHYLSILYL)-1-PROPYNE] ». University of Cincinnati / OhioLINK, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=ucin973701057.

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Xu, Xiangrong. « Uranyl ion sensitised photooxidation of alkanes ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq27436.pdf.

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Gomes, Ana Catarina Costa. « Photocatalysis : Carbonylation of arenas and alkanes ». Thesis, University of York, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516370.

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Smith, Paul Andrew. « Simulation studies of alkanes and surfactants ». Thesis, Queen's University Belfast, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314225.

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Shiimi, Annatolia. « Modeling Diiron enzymes for alkanes activation ». Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/10669.

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Includes abstract.
Includes bibliographical references.
The synthesis and characterization of a series of ruthenium 'sawhorse' complexes of the type [RU2(IJ-02CRh(CO)4(Lh]' has been successfully carried out. The complexes have been characterized by IR, 1H and 13C NMR spectroscopy, elemental analysis as well as by mass spectrometry.

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Correia, Leslie Daniel Camara. « Oxygen transfer in hydrocarbon-aqueous dispersions and its applicability to alkane-based bioprocesses ». Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/999.

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Livres sur le sujet "Alkanes"

Hiemstra, H. Alkanes. Stuttgart : Thieme, 2009.

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Patai, Saul, et Zvi Rappoport, dir. Alkanes and Cycloalkanes (1992). Chichester, UK : John Wiley & Sons, Ltd, 1992. http://dx.doi.org/10.1002/0470034378.

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Marsh, K. N., dir. Densities of Aliphatic Hydrocarbons _ Alkanes. Berlin/Heidelberg : Springer-Verlag, 1996. http://dx.doi.org/10.1007/b58738.

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L, Hill Craig, dir. Activation and functionalization of alkanes. New York : Wiley, 1989.

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Saul, Patai, et Rappoport Zvi, dir. The Chemistry of alkanes and cycloalkanes. Chichester : Wiley, 1992.

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Well, Willy Van. Adso rption of alkanes in zeolites. Eindhoven : Eindhoven University, 1998.

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Bursian, N. R. Tekhnologii͡a︡ izomerizat͡s︡ii parafinovykh uglevodorodov. Leningrad : "Khimii͡a︡," Leningradskoe otd-nie, 1985.

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Derouane, Eric G., Jerzy Haber, Francisco Lemos, Fernando Ramôa Ribeiro et Michel Guisnet, dir. Catalytic Activation and Functionalisation of Light Alkanes. Dordrecht : Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-017-0982-8.

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1923-, Calvert Jack G., dir. Mechanisms of atmospheric oxidation of the alkanes. Oxford : Oxford University Press, 2008.

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G, Derouane E., et North Atlantic Treaty Organization. Scientific Affairs Division., dir. Advances and challenges : Catalytic activation and functionalisation of light alkanes. Dordrecht : Boston, Mass., 1998.

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Chapitres de livres sur le sujet "Alkanes"

Quintas, Louis V., et Edgar G. DuCasse. « Alkanes ». Dans New Frontiers in Nanochemistry, 7–17. Includes bibliographical references and indexes. | Contents : Volume 1. Structural nanochemistry – Volume 2. Topological nanochemistry – Volume 3. Sustainable nanochemistry. : Apple Academic Press, 2020. http://dx.doi.org/10.1201/9780429022937-2.

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Clugston, Michael, Malcolm Stewart et Fabrice Birembaut. « Hydrocarbons : Alkanes ». Dans Making the Transition to University Chemistry. Oxford University Press, 2021. http://dx.doi.org/10.1093/hesc/9780198757153.003.0017.

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This chapter tackles the concept of alkanes, a type of hydrocarbon. It defines a hydrocarbon as containing hydrogen and carbon only. Alkanes are saturated hydrocarbons. Crude oil is an example of a complex mixture of hydrocarbons, most of which are alkanes. Fractional distillation allows for the separation of the mixture and relies on the different fractions with varying boiling points. The chapter explores the mechanism for radical chain reaction and photochemical halogenation which occur through the reaction of an alkane with a halogen. Finally, the combustion of alkanes is considered to be the most significant reaction commercially since it is also a radical chain reaction.

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« Alkanes ». Dans Lead Optimization for Medicinal Chemists, 33–39. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2013. http://dx.doi.org/10.1002/9783527645640.ch3.

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Robin, Melvin B. « Alkanes ». Dans Higher Excited States of Polyatomic Molecules, 79–106. Elsevier, 1985. http://dx.doi.org/10.1016/b978-0-12-589903-1.50007-2.

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Lin-Vien, Daimay, Norman B. Colthup, William G. Fateley et Jeanette G. Grasselli. « Alkanes ». Dans The Handbook of Infrared and Raman Characteristic Frequencies of Organic Molecules, 9–28. Elsevier, 1991. http://dx.doi.org/10.1016/b978-0-08-057116-4.50008-0.

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« Alkanes ». Dans Category 6, Compounds with All-Carbon Functions, sous la direction de Hiemstra. Stuttgart : Georg Thieme Verlag, 2009. http://dx.doi.org/10.1055/sos-sd-048-00001.

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« ALKANES ». Dans Understanding Advanced Chemistry Through Problem Solving, 69–79. WORLD SCIENTIFIC, 2023. http://dx.doi.org/10.1142/9789811281839_0004.

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« ALKANES ». Dans Understanding Advanced Chemistry Through Problem Solving, 69–79. WORLD SCIENTIFIC, 2014. http://dx.doi.org/10.1142/9789814596503_0004.

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« Alkanes ». Dans Understanding Advanced Organic and Analytical Chemistry, 111–28. WORLD SCIENTIFIC, 2016. http://dx.doi.org/10.1142/9789814733991_0004.

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« Alkanes ». Dans Understanding Advanced Organic and Analytical Chemistry, 105–21. WS EDUCATION, 2011. http://dx.doi.org/10.1142/9789814374996_0004.

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Actes de conférences sur le sujet "Alkanes"

Yin, Sudong, Yanglin Pan et Zhongchao Tan. « Catalytic Hydrothermal Conversion of Glucose to Light Petroleum Alkanes ». Dans ASME 2010 4th International Conference on Energy Sustainability. ASMEDC, 2010. http://dx.doi.org/10.1115/es2010-90433.

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The production of carbon-neutral liquid fuels from renewable biomass has attracted worldwide interest in an age of depletion of fossil fuel reserves and pollutions caused by utilization of fossil petroleum. Currently, commercial bio-oil production technologies include bio-ethanol, bio-diesel and pyrolysis bio-oil. But, these bio-oils mainly consist of alcohols and aromatic chemicals rather than alkanes of the main components of gasoline and diesel. Direct utilization of these bio-oils can corrode car engines as well as emitting large unburned hydrocarbons particles through automotive combustion system. Therefore, in this study, catalytic hydrothermal conversion (CHTC) of glucose to alkanes in a single batch reactor was investigated with respect to effects of conversion parameters such as initial pressure of process gas H2, pH level of aqueous solution and catalysts on alkane yields and compositions. Results showed that the highest alkane yield of 21.6% (based on the mol of the input glucose) was obtained at 265 °C, with 300 psi of H2 process gas, 0.5 g catalyst of 1w%. Pt/Al2O3 and a residence time of 15 h. The alkane yield was significantly influenced by the initial pressure of H2, which increased with increasing H2 pressure. On the other hand, the alkane yields first increased and then decreased with pH levels. Also, more alkanes were produced by Pt/Al2O3 than Pd/Al2O3. Regarding alkane compositions, high initial pressure of H2 favored the production of relatively heavy C3–4 alkanes. With 300 psi of initial H2, C3H8 and C4H10 accounted for 75% of the total produced alkanes. All of the experimental data in this study lead to one conclusion that petroleum alkanes can be directly produced from glucose.

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Leyva Gutierrez, Francisco, et Tong Wang. « Crystallography and Functionality of Natural Waxes : Insights for the Development of Tailored Lipid Materials ». Dans 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/nyok4571.

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Natural waxes are valuable industrial products consisting of complex chemical mixtures. To probe the structure−function role of select constituents, model n-alkanes, alcohols, aldehydes, and fatty acids of C18−19, C22−23, and C26−27 carbon chain lengths were synthesized and analyzed via calorimetry and X-ray powder diffraction. Pure compounds and binary mixtures crystallized into monoclinic (M), triclinic (T), and orthorhombic (O) lattices or combinations thereof. The C26 aldehyde formed an O lattice and exhibited one solid−solid phase transition similar to n-alkanes. The water vapor permeability (WVP) of model systems cast as films was determined. For pure compounds, WVP decreased in the following order: fatty acid > even n-alkane > odd n-alkane > alcohol > aldehyde. Increasing carbon chain length, which translates to increasing unit cell volume, decreased WVP. Binary mixtures generally exhibited a more complex relationship with WVP. These findings may be applicable to the agricultural postharvest, pharmaceutical, and paperboard coating industries.

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Bellan, Josette R., et Panayotis Kourdis. « A Unified Reduction of Elementary Kinetic Mechanisms for n-Alkanes, Highly-Branched Alkanes and Cycloalkanes ». Dans 55th AIAA Aerospace Sciences Meeting. Reston, Virginia : American Institute of Aeronautics and Astronautics, 2017. http://dx.doi.org/10.2514/6.2017-0834.

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Lowry, William, Jaap de Vries, Michael Krejci, Eric Petersen, Zeynep Serinyel, Wayne Metcalfe, Henry Curran et Gilles Bourque. « Laminar Flame Speed Measurements and Modeling of Pure Alkanes and Alkane Blends at Elevated Pressures ». Dans ASME Turbo Expo 2010 : Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-23050.

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Alkanes such as methane, ethane, and propane make up a large portion of most natural gas fuels. Natural gas is the primary fuel used in industrial gas turbines for power generation. Because of this, a fundamental understanding of the physical characteristics such as the laminar flame speed is necessary. Most importantly, this information is needed at elevated pressures to have the most relevance to the gas turbine industry for engine design. This study includes experiments performed at elevated pressures, up to 10-atm initial pressure, and investigates the fuels in a pure form as well as in binary blends. Flame speed modeling was done using an improved version of the kinetics model that the authors have been developing over the past few years. Modeling was performed for a wide range of conditions, including elevated pressures. Experimental conditions include pure methane, pure ethane, 80/20 mixtures of methane/ethane, and 60/40 mixtures of methane/ethane at initial pressures of 1, 5, and 10 atm. Also included in this study are pure propane and 80/20 methane/propane mixtures at 1 and 5 atm. The laminar flame speed and Markstein Length measurements were obtained from a high-pressure flame speed facility using a constant-volume vessel. The facility includes optical access, a high-speed camera, a schlieren optical setup, a mixing manifold, and an isolated control room. The experiments were performed at room temperature, and the resulting images were analyzed using linear regression. The experimental and modeling results are presented and compared to previously published data. The data herein agree well with the published data. In addition, a hybrid correlation was created to perform a rigorous uncertainty analysis. This correlation gives the total uncertainty of the experiment with respect to the true value rather than reporting the standard deviation of a repeated experiment. Included in the data set are high-pressure results at conditions where in many cases for the single-component fuels few data existed and for the binary blends no data existed prior to this study. Overall, the agreement between the model and data is excellent.

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Guolin, Jing, Qin Shaopeng et Li Ming. « Oxidation of Alkanes in Supercritical Water ». Dans 2009 International Conference on Energy and Environment Technology (ICEET 2009). IEEE, 2009. http://dx.doi.org/10.1109/iceet.2009.395.

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Ando, Hiromitsu, Yasuyuki Sakai et Kazunari Kuwahara. « Factors Determining the Octane Number of Alkanes ». Dans SAE 2014 World Congress & Exhibition. 400 Commonwealth Drive, Warrendale, PA, United States : SAE International, 2014. http://dx.doi.org/10.4271/2014-01-1227.

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Ryu, M., M. Romano, J. C. Batsale, C. Pradere et J. Morikawa. « Microscale spectroscopic thermal imaging of n-alkanes ». Dans 2016 Quantitative InfraRed Thermography. QIRT Council, 2016. http://dx.doi.org/10.21611/qirt.2016.108.

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Iliev, Valentin Vankov, Theodore E. Simos et George Maroulis. « On Some Isomers of the Linear Alkanes ». Dans COMPUTATIONAL METHODS IN SCIENCE AND ENGINEERING : Theory and Computation : Old Problems and New Challenges. Lectures Presented at the International Conference on Computational Methods in Science and Engineering 2007 (ICCMSE 2007) : VOLUME 1. AIP, 2007. http://dx.doi.org/10.1063/1.2836130.

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Nickel, Daniel V., et Daniel M. Mittleman. « Terahertz time domain spectroscopy of branched alkanes ». Dans CLEO : Science and Innovations. Washington, D.C. : OSA, 2012. http://dx.doi.org/10.1364/cleo_si.2012.cm1l.8.

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Coskuner, Yakup Berk, Elio Dean, Xiaolong Yin et Erdal Ozkan. « Water Alternating Alkane Injection : A Molecular Dynamics Simulation Study ». Dans SPE Improved Oil Recovery Conference. SPE, 2022. http://dx.doi.org/10.2118/209363-ms.

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Abstract In a recent study, we observed that the diffusion coefficient of common hydrocarbons in crude oils are more affected by the presence of different hydrocarbon components than the effect of confinement. Based on our previous observations, in this study, we investigated the efficiency of smaller-chain alkane injection into oil-soaked sandstone pores to dilute the oil with alkane. We used molecular dynamics simulations of C2, C3, C4 and C5 as well as a mixture of C3 and C4 to rank the effects of different alkanes on the diffusion and distribution of oil molecules in pore. As water-alternating-alkane injection would bring water into the pores, our simulations included water. Our results indicate that alkane injection into sandstone reservoirs has a significant potential due to the fact that it effectively dilutes the oil. Water always wets quartz surface relative to the oils. Injection of water therefore should be effective in detaching oil molecules on the surface. Presence of water layers did not affect the diffusion coefficients of oil molecules.

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Rapports d'organisations sur le sujet "Alkanes"

Scott Han. Millisecond Oxidation of Alkanes. Office of Scientific and Technical Information (OSTI), septembre 2011. http://dx.doi.org/10.2172/1025808.

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Lyons, J. E. Catalytic conversion of light alkanes. Office of Scientific and Technical Information (OSTI), juin 1992. http://dx.doi.org/10.2172/7090637.

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Doskey, P. V. The vapor-particle partitioning of n-alkanes. Office of Scientific and Technical Information (OSTI), avril 1994. http://dx.doi.org/10.2172/10141716.

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Deutsch, M., B. M. Ocko, X. Z. Wu, E. B. Sirota et S. K. Sinha. Surface crystallization in normal-alkanes and alcohols. Office of Scientific and Technical Information (OSTI), juin 1995. http://dx.doi.org/10.2172/80963.

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Wu, X. Z., H. H. Shao, B. M. Ocko, M. Deutsch, S. K. Sinha, M. W. Kim, H. E. Jr King et E. B. Sirota. Surface crystallization and thin film melting in normal alkanes. Office of Scientific and Technical Information (OSTI), décembre 1994. http://dx.doi.org/10.2172/10117552.

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Lyons, J. E. Catalytic conversion of light alkanes : Proof of concept stage. Office of Scientific and Technical Information (OSTI), juin 1995. http://dx.doi.org/10.2172/67783.

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Lyons, J. E. Catalytic conversion of light alkanes. [Methane, ethane, propane and butanes]. Office of Scientific and Technical Information (OSTI), septembre 1992. http://dx.doi.org/10.2172/7090643.

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Cesar, J. R., et O. H. Ardakani. Organic geochemistry of the Montney Formation : new insights about the source of hydrocarbons, their accumulation history and post accumulation processes. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/329788.

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This study consists of a non-traditional molecular and stable isotope approach to analyze organic matter (soluble bitumen and produced oil/condensate) from the Montney Formation low-permeability reservoirs, with the purpose of identifying source(s) of hydrocarbons, accumulation history and post accumulation processes. The same approach bases on the distribution of compound classes such as aromatic carotenoids, polycyclic aromatic hydrocarbons (PAHs), bicyclic alkanes, and oxygen-polar compounds. The geochemical screening has been enhanced with performing compound specific isotope analysis (CSIA) of n-alkanes and selected aromatic hydrocarbons. Widely spread PAHs, the presence of molecular indicators of euxinia, and hydrocarbon mixtures identified using CSIA profiles, are some of the key findings from this research, which will improve our understanding of the Montney petroleum system(s).

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Edward M. Eyring. Spectroscopic Characterization of Intermediates in the Iron Catalyzed Activation of Alkanes. Office of Scientific and Technical Information (OSTI), mai 2007. http://dx.doi.org/10.2172/928851.

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Shkrob, I. A., et A. D. Trifunac. Pulse radiolysis of alkanes : A time-resolved electron paramagnetic resonance study. Office of Scientific and Technical Information (OSTI), février 1994. http://dx.doi.org/10.2172/10114982.

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