CO2 to methanol

In a very recent example (Figure 1.53), INEPT DOSY has been applied to confirm the dinudear nature of the unstable Zirconium intermediate 141 in the reaction of CO with [ZrHCl(Cp)], 140 [344], a model reaction for the heterogeneously catalyzed hydrogenation of CO2 to methanol [345]. As was expected for a binuclear compound, the diffusion coefficient of intermediate 141 is smaller than for the mononuclear 142. 

More complex reductions of CO2 by enzyme cascades have also been achieved. A combination of an electron mediator and two enzymes, formate dehydrogenase and methanol dehydrogenase, was used to reduce CO2 to methanol. This system operates with current efficiencies as high as 90% and low overpotentials (approximately —0.8 V vs. SCE at pH 7) [125]. The high selectivity and energy efficiency of this system indicate the potential of enzyme cascades. There are also drawbacks to these systems. In general, enzymes are... 

Figure 1.1.7 Equilibrium calculation for the hydrogenation of CO2 to methanol at 50 bar pressure. The parameter is the fraction of CO in CO2 facilitating the hydrogenation.

An alternative "after combustion" type of CO2 removal is to convert atmospheric CO2 to methanol by a catalytic process at elevated temperature and pressure. Catalyst based on Cu and ZnO are used and laboratory demonstrations performed at a temperature of 150°C and a pressure of 5 MPa (Saito et al., 1997). Additional reaction products are CO and water. Other... 

For Cu-La2Zr207, as well as for Cu-ZnO catalysts, an almost linear correlation can be observed between the methanol yield, the copper surface area and the amount of formates located on the catalyst s surface. A similar correlation cannot be evidenced on ZnO promoted Cu-La2Zr207 catalysts. The results are discussed and a mechanism for the hydrogenation of CO2 to methanol is proposed... 

Results at true differential conversions have demonstrated that the intrinsic rate of COj hydrogenation is unaffected by the presence of Pd, whether it is incorporated by impregnation or added in a physical mixture, in the absence of water. For catalytic conversion of CO2 to methanol, a limiting factor at industrially useful yields is the high concentration of product water the effect of which can be ameliorated to some extent by Pd probably due to hydrogen spillover. 

Effective conversion of CO2 to methanol and dimethyl ether over hybrid catalysts... 

The elements Mo and Ru were reported to reduce CO2 to methanol or CH4 by Frese et al. with low partial current density below 0.1 mA but the observations have not been reproduced... 

Table 7 Photoelectrochemical conversion of CO2 to methanol using p-GaP with pyridine...

The conversion of CO and CO2 to methanol is limited by the pertinent chemical equilibria. The conversions of CO and CO2 resulting at various pressures and temperatures on the equlibrium being adjusted were listed in Table 3.6 for a synthesis gas produced from coal containing 3.0% CO2, 27.0% CO, 64% H2, 4 % CH4 and 2 % N2, all by volume. 

Ogura, K. and I. Yoshida (1988). Electrocatalytic reduction of CO2 to methanol— part 9 Mediation with metal porphyrins. J. Mol. Catal. 47(1), 51-57. 

The two equations above illustrates that the reduction of CO2 to methanol is a scientifically severe challenge. Inoue et al. (Inoue et al., 1979) [5] were the first to report CO2 photoreduction to methanol in 1979 over binary inorganic materials with a... 

Barton, E.E., Rampulla, D.M. and Bocarsly, A.B. Selective solar-driven reduction of CO2 to methanol using a catalyzedp-GaP basedphotoelectrochemical cell. Journal of the American Chemical Society, 2008. 130(20) p. 6342-+. 

Toyir J, Ramirez de la Piscina P, Fierro JLG, Homs N. Highly effective conversion of CO2 to methanol over supported and promoted copper-based catalysts influence of support and promoter. Appl Catal B Environ 2001 29 207-15. 

Cole EB, Lakkaraju PS, Rampulla DM, Morris AJ, Abelev E, Bocarsly AB (2010) Using a one-electron shuttle for the multielectron reduction of CO2 to methanol kinetic, mechanistic, and structural insights. J Am Chem Soc 132(33) 11539-11551... 

Barton EE, RampuUa DM, Bocarsly AB (2008) ive solar-driven rednction of CO2 to methanol using a eatalyzed p-GaP based photoelectroehemieal cell. J Am Chem Soc 130 6342... 

The reverse process, cathodic reduction of CO2 to methanol [reaction (10.10), going from right to left] or to other organic compounds, has also been the subject of numerous studies in recent decades. These studies had basically two practical aims, as described below. 

The series of reactions above gives an insight into the reaction mechanism of reduction of CO2 to methanol, with three consecutive 2e -transfer steps (see also Chap. 8). 

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