Hydrocarbons formation

Mobil MTG and MTO Process. Methanol from any source can be converted to gasoline range hydrocarbons using the Mobil MTG process. This process takes advantage of the shape selective activity of ZSM-5 zeoHte catalyst to limit the size of hydrocarbons in the product. The pore size and cavity dimensions favor the production of C-5—C-10 hydrocarbons. The first step in the conversion is the acid-catalyzed dehydration of methanol to form dimethyl ether. The ether subsequendy is converted to light olefins, then heavier olefins, paraffins, and aromatics. In practice the ether formation and hydrocarbon formation reactions may be performed in separate stages to faciHtate heat removal. 

Several biomass species have been found to contain oils and/or hydrocarbons (Table 13). It is apparent that oil or hydrocarbon formation is not limited to any one family or type of biomass. Interestingly, some species in the Euphorbiaceae family, which includes Hevea bra liensis form hydrocarbons having molecular weights considerably less than that of natural mbber at yields as high as 10 wt% of the plant. This corresponds to hydrocarbon yields of about 3.97 mVhm2-yr(25bbl/hm2-yr). 

Selectivity is primarily a function of temperature. The amount of by-products tends to increase as the operating temperature is raised to compensate for declining catalyst activity. By-product formation is also influenced by catalyst impurities, whether left behind during manufacture or otherwise introduced into the process. Alkaline impurities cataly2e higher alcohol production whereas acidic impurities, as well as trace iron and nickel, promote heavier hydrocarbon formation. 

In secondary operations, where chemicals are injected into hydrocarbon formations in conjunction with a chemical flooding process, polyamines are used to reduce the loss of injected chemicals to the formation by adsorption and precipitation (312). TEPA and other ethyleneamines are used with water-soluble polymeric thickeners in water—flood petroleum recovery operations to stabilize viscosity, mobiUty, and pH while imparting resistance to hydrolysis (313). 

It is also clear that in the former case electropositive promoters (alkalis) should enhance the rate of hydrocarbon formation while in the latter case a beneficial effect is to be expected only if CO is weakly adsorbed and to the extent that the alkali does not induce CO dissociation. 

McEnally, C.S. et al.. Studies of aromatic hydrocarbon formation mechanisms in flames Progress towards closing the fuel gap. Prog. Energy Combust. Sci., 32, 247, 2006. 

The reaction of steam with coal generates a 1 1 gas mixture of H2 and CO. Hydrocarbon formation requires a 2 1 mixture, so additional H2 is produced by the reaction of steam with some of the CO ... 

K. W. Smith and T. R. Thomas. Method of treating shale and clay in hydrocarbon formation drilling. Patent EP 680504,1995. 

Hydrocarbon formation involves the removal of one carbon from an acyl-CoA to produce a one carbon shorter hydrocarbon. The mechanism behind this transformation is controversial. It has been suggested that it is either a decarbonylation or a decarboxylation reaction. The decarbonylation reaction involves reduction to an aldehyde intermediate and then decarbonylation to the hydrocarbon and releasing carbon monoxide without the requirement of oxygen or other cofactors [88,89]. In contrast, other work has shown that acyl-CoA is reduced to an aldehyde intermediate and then decarboxylated to the hydrocarbon, releasing carbon dioxide [90]. This reaction requires oxygen and NADPH and is apparently catalyzed by a cytochrome P450 [91]. Whether or not a decarbonylation reaction or a decarboxylation reaction produces hydrocarbons in insects awaits further research on the specific enzymes involved. 

The effect of hydrogen pressure in the reaction network and kinetics of quinoline hydrodenitrogenation has been matter of debate. Some controversial results and explanation were raised by the proposal of light hydrocarbons formation [78], The lack of observation of these hydrocarbons in previous experiments was explained by the low pressure employed and the deviations observed of the mass balances in these experiments were an evidence for the formation of lights HCs. The controversy is not clear yet and might be the subject for further investigations. 

Geacintov, N.E. Ibanez, V. Benjamin, M.J. Hibshoosh, H. 5 Harvey, R.G. In "Polynuclear Aromatic Hydrocarbons Formation, Metabolism and Measurement" Cooke, M. 5 Dennis, A.J., Eds Battelle Press, Columbus, Ohio, 1983, 554-570. 

Koerts, T., Deelen, M., and van Santen, R., Hydrocarbon formation from methane by a low-temperature two-step reaction sequence, /. Catal., 138, 101,1992. 

Nolan, P. E., Lynch, D. C., and Cutler, A. H. 1998. Carbon deposition and hydrocarbon formation on Group VIII metal catalysts. J. Phys. Chem. B 102 4165-75. 

FIGURE 9.25 Basic kinetic scheme of FT hydrocarbon formation on cobalt. 

Co-feeding of alcohols effects an increased rate of hydrocarbon formation, as shown in early experiments of Emmett and coworkers1"1 using 14C-labeled alcohols. These experiments were carried out in order to support the hydroxyl-carbene mechanism favored at that time. Their experiments were confirmed by Shi and Davis23 for Co catalysts and co-feeding of ethanol. Furthermore, in their study, the argument that ethanol may be dehydrated to ethene, incorporated, and followed by subsequent chain growth via CH2 insertion could be excluded, as co-fed ethanol incorporated much faster than ethene. 

It is clear that a complex hydrocarbon polymer chemistry must exist in the atmosphere of Titan involving polyyne species, polynitrile species and mixtures of the two, and additional routes to polyaromatic hydrocarbon formation. This presents a significant problem for the gas chromatography/mass spectrometry instruments on the Huygens probe. There should be hydrocarbon fragments, producing perhaps... 

The catalyst used for the conversion of methanol to gasoline is based on a new class of shape-selective zeolites (105-108), known as ZSM-5 zeolites, with structures distinctly different from other well-known zeolites. Apparently, the pore dimensions of the ZSM-5 zeolites are intermediate between those of wide-pore faujasites (ca. 10 A) and very narrow-pore zeolites such as Zeolite A and erionite (ca. 5 A) (109). The available structural data indicate a lattice of interconnecting pores all having approximately the same diameter (101). Hydrocarbon formation... 

Hydrocarbon Formation on Polymer-Supported -Cyclopentadienyl Cobalt... 

The principal competing reactions to ruthenium-catalyzed acetic acid homologation appear to be water-gas shift to C02, hydrocarbon formation (primarily ethane and propane in this case) plus smaller amounts of esterification and the formation of ethyl acetate (see Experimental Section). Unreacted methyl iodide is rarely detected in these crude liquid products. The propionic acid plus higher acid product fractions may be isolated from the used ruthenium catalyst and unreacted acetic acid by distillation in vacuo. 

Black, J.J. 1983. Epidermal hyperplasia and neoplasia in brown bullheads (Ictalurus nebulosus) in response to repeated applications of a PAH containing extract of polluted river sediment. Pages 99-111 in M. Cooke and A.J. Dennis (eds.). Polynuclear Aromatic Hydrocarbons Formation, Metabolism and Measurement. Battelle Press, Columbus, OH. 

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