Catalysts derived from nickel sources

Catalysts Derived from Nickel(O) and Nickel(ll) Sources... 

Stolzenberg demonstrated that the low-valent, heterogeneous sources of Ni, Raney nickel and nickel boride, yield methane from MeCoM. "" The former reaction is quantitative, while in the latter, the catalyst preferentially cleaves the S—CH2 bond of MeCoM. Attempts to prepare homogeneous catalysts derived from Ni macrocycles and sodium borohydride proved ineffective. 

The vanadium generally associated with ashphaltenes, nickel and iron are constituents of the crude oil from which the fiiel oil is derived, whereas the sodium occurs in a brine phase. The silicon and aluminium are present as a result of the refining process, generally derived from inert catalyst carriers. Sulphur is usually present in the form of organic sulphur compounds, the amount depending on the origin of the crude oil from which the fuel oil is obtained. The presence of these "impurities" is the source of fouling from oil combustion. 

In contrast to these findings, earlier VH4 studies (34, 35] of the mcthylation of benzene and some other hydrocarbons with methane over nickel on silica and alumina catalysts showed that the methyl group was largely derived from sources other than methane gas. Carbonaceous species were thought to supply part of the carbon for mcthylation. A more recent CHi isotopic tracer investigation by Lunsford and co-workers [18] also failed to reveal the presence of any detectable C in the methylated products of the mcthylation of benzene over H-beta catalyst in a flow reactor at 400 X and 4.8 MPa pressure. The workers [18] then concluded that benzene served as the sole source of carbon in all of the observed products under their reaction conditions. Thus, it appears that there is tack of agreement in the... 

Fischer-Tropsch process /fish-er tropsh/ The catalytic hydrogenation of carbon monoxide in the ratio of 2 1 hydrogen to carbon monoxide at 200°C to produce hydrocarbons, especially motor fuel. The carbon monoxide is derived from water gas, which uses coal or natural gas as a source of carbon, and the catalyst is finely divided nickel. The process was extensively used in Germany during World War II and is still used in countries in which crude oil is not... 

The reactivity of aryl triflates [24,32,36,49] and other sulfonates [45,48] can be slightly different than is presented here, what depends on the catalyst and the reaction conditions used. For example, the SM reactions of aryl chlorides in the presence of aryl triflates catalysed by Pd2(dba)3 / 2Pt-Bu3 have given exclusively the biaryl derived from the chloride, whereas the use of Pd(OAc)2 / 2PCy3 catalytic system leads to predominant SM reaction of aryl triflate. The latter results indicate the fact, that the (phosphine) ligand(s), not the palladium (nickel) source, controls chloride / triflate selectivity, as well as other closely reactive substrates. 

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