Methanation reduction

Nickel compounds Hydrogenations (e.g. Raney nickel) Conversion of synthesis gas to methane Reduction of organo nitro compounds to amines Carcinogenic (nickel subsulphide). Skin sensitization... 

Protonation reactions of the related dimethyl(hydrido)platinum(IV) complex TpMe2PtMe2H (58) leading to rapid methane reductive elimination have also been reported (86). This protonation was shown to occur exclusively at the pyrazole nitrogen, presumably forming a five-coordinate Pt(IV) intermediate. This species should undergo C-H coupling, and while a Pt(II) methane complex is not observed, trapping with... 

Regeneration by methane reduction is conducted in a separate unit returning sulfur dioxide, but now in more useful high concentrations (Eq. 3.42). Regeneration ... 

This has been shown to meet stringent regulatory requirements with a processing train very similar to that used for methane reduction (Fig. 11.7). 

SCHEME 11.6 The rates of H/D exchange for a Re(V) perdeuteriomethyl hydride complex and of methane reductive elimination as a function of temperature allow comparison of activation parameters for the two processes. 

Parkin and Bercaw reported that Cp 2W(Me)(H) eliminates methane to form Cp (ri5,ri1-C5Me4CH2)WH.26 For the mixed isotopomer, Cp 2W(CH3)(D), H/D scrambling to give Cp 2W(CH2D)(H) is competitive with the methane elimination process (Scheme 11.7). Although the authors point out that the H/D exchange process could occur by pathways other than formation of a methane-coordinated intermediate, the observation of an inverse kinetic isotope effect (KIE) for the methane reductive elimination (see bottom of Scheme 11.7) provides additional support for the reversible formation of coordinated alkane (see below for a more detailed discussion of KIEs for reductive elimination of C—H bonds). Furthermore, at relatively low concentrations, heating a mixture of Cp 2W(CH3)(H) and Cp 2W(CD3)(D) produces only CH4 and CD4 with no observation of H/D crossover, which is consistent with intramolecular C—H(D) processes. Similar results have been obtained for... 

Gallon, H.J., Tu, X., Twigg, M.V. and Whitehead, J.C. (2011). Plasma-Assisted Methane Reduction of a NiO Catalyst — Low Temperature Activation of Methane and Formation of Carbon Nanofibres. AjsjoZ. Catal. B Environ., 106, pp. 616-620. 

---