Methane, homologation

Boskovic, G., and Smith, K. J. 1997. Methane homologation and reactivity of carbon species on supported Co catalysts. Catal. Today 37 25-32. 

Co2(CO)g has been used to obtain encapsulated cobalt clusters in Y-faujasite, which have been used as model catalysts for methane homologation [152]. The gas phase adsorption of Co2(CO)8 under N2 rendered predominately encaged Co4(CO)i2 species whereas Co,s(CO)iis was obtained when the impregnation of Co2(CO)8 was carried out under a CO/H2 atmosphere [152, 155], Samples were oxidized at 80°C, subsequently reduced at 400 °C and then structurally characterized by EXAFS. Clusters of two and three cobalt atoms were formed from encaged Co4(CO)i2 and COis(CO)iis, respectively. Higher methane conversion and selectivity to C2+ products in the CH4 homologation reaction have been obtained for the two atoms-size cluster sample the results were discussed using a DFT model [152]. 

Fig. S-20. (a) Frequency distribution of the sum of methane homologs in 3,500 samples from different types of reservoirs (from Nikonov, 1971). Gas, oil and condensate surveys (b) location frequency distributions of hydrocarbons in soil gas over different basins, (c) methanerethane ratio, (d) propane methane ratio, (e) methane content, (0 Pixler ratio diagram (Pixler, 1969), (g) soil-gas data plotted on Pixler diagram, (h) Reservoir gas analyses of Verbanac and Ounia (1982) plotted on Pixler diagram.

Dadashev, F.G., 1982. The background of methane homologs in near surface sediments as a regional indicator of source rock potential. Neftoegozovaya Geol., Geofiz, No. 1, pp. 19-20. 

Nikonov, V.F., 1971. Distribution of methane homologs in gas and oil fields. Akademiya Nauk SSSR Doklady, 206 234-236. 

The metal catalysts derived from the zeolite-entrapped metal cluster complexes have been studied because of the interest in a uniform distribution and a high degree of metal dispersion through the zeolite frameworks. Nevertheless, little information is available on the structural and chemical behavior of the entrapped metal cluster complexes, particularly on the retention of the cluster character under the reaction conditions, e.g., CO + H2, alkane hydrogenolysis and methane homologation re-... 

Natural gas, depending on its source, contains—besides methane as the main hydrocarbon compound (present usually at >80-90%) — some of the higher homologous alkanes (ethane, propane, butane). In wet gases the amount of C2-C5 alkanes is higher (gas liquids). 

In the attempted thermolytic preparation of pyrroloisoxazole (32) from azidoisoxazole (31a), only cinnamoyl cyanide was isolated. The assumed intermediate nitrene (33) did not insert into the styryl bond, but rather ring rupture and loss of acetonitrile produced the product. Similar products were obtained from the homolog (31b) (Scheme 7) (79TL4685). The stabilized nitrene intermediate is similar to that postulated for diazofuryl- and diazoisoxazolyl-methanes (78JA7927, 79TL2961). 

The ability of C to catenate (i.e. to form bonds to itself in compounds) is nowhere better illustrated than in the compounds it forms with H. Hydrocarbons occur in great variety in petroleum deposits and elsewhere, and form various homologous series in which the C atoms are linked into chains, branched chains and rings. The study of these compounds and their derivatives forms the subject of organic chemistry and is fully discussed in the many textbooks and treatises on that subject. The matter is further considered on p. 374 in relation to the much smaller ability of other Group 14 elements to form such catenated compounds. Methane, CH4, is the archetype of tetrahedral coordination in molecular compounds some of its properties are listed in Table 8.4 where they are compared with those of the... 

PerD32 Perry, D. The number of structural isomers of certain homologs of methane and methanol. J. Amer. Chem. Soc. 54 (1932) 2918-2920. 

A homologous series of hydrocarbons of general formula C I I2ni 2, of which the first member is methane CH4. 

It should be noted at this point that primary and secondary reaction products can be distinguished not only by kinetic data (13) but also by suppression of the secondary reactions. E.g substitution of 2,2,2-trifluoroethanol for p-dioxane as solvent for HCoCCO) suppresses homologation and methane formation addition of a phosphine to give the less acidic catalyst HCo(CO)3PR3 has the same effect, as has the substitution of the less acidic catalyst HMn(CO)5. 

J. S. Lloyd, R. Finch, H. Dalton, J. C. Murrell (1999) Homologous expression of soluble methane monooxygenase genes in Methylosinus trichosporium OB3b. Microbiology, 145 461-470... 

Reduction of C02 past formic acid generates formaldehyde, methanol or methane (Eqs. (16-18)), and ethanol can be produced by homologation of the methanol. The liberation of water makes these reactions thermodynamically favorable but economically less favorable. The reductions typically require much higher temperatures than does the reduction to formic acid, and consequently few homogeneous catalysts are both kinetically capable and able to withstand the operating conditions. 

Paraffin (alkane) one of a series of saturated aliphatic hydrocarbons, the lowest numbers of which are methane, ethane, and propane. The higher homologs are solid waxes. 

In the presence of an acyclic alkane, 3 catalyzes at moderate temperature (25-200 °C) the metathesis reaction, leading to the formation of heavier and lower homolog alkanes by simultaneous breaking and formation of C-H and C-C bonds. For example, propane is transformed, even at 25 °C into a quasi-equimolar mixture of ethane and butanes (n- and iso-mixture) as well as methane and pentanes, in lower quantities. Lower and heavier homologs are also obtained starting from... 

As pointed out above, neither methane nor its higher homologs (ethane, propane, hexane) can be effectively metalated. The introduction of a hetero-substituent changes this outset profoundly. Second-row and third-row elements (such as silicon, phosphorus and sulfur) will not be considered in this context as they are known to acidify hydrocarbons strongly due to d-orbital resonance (or polarization) effects. But also the first-row elements nitrogen, oxygen and fluorine can distinctly facilitate the deprotonation of paraffinic hydrocarbons. 

Within the reaction parameters used, the nickel catalyst is highly selective towards carbonylation. With the exception of trace a-mounts of methane formed, no other hydrogenation product is found. This is in contrast with cobalt whose carbonylation catalytic activity is enhanced by hydrogen but generally associated with aldehyde formation and homologation. 

These species show different promoting effects on the activity and selectivity of the homologation of methyl acetate with CO + H2 (carbonylation to acetic acid, homologation to ethyl acetate and hydrogenation to methane) (5). 

---