On the mechanisms and the selectivity determining steps in syngas conversion over supported metal catalysts: An IR study

Abstract

Abstract An IR study of syngas and methanol conversion has been performed over Cu–ZnO–Al 2 O 3 methanol synthesis catalyst, Ni–Al 2 O 3 methanation catalyst and Co–Al 2 O 3 Fischer Tropsch catalyst. The data, obtained at low pressure, provide unequivocal evidence of the existence of a way via oxygenated intermediates (formates, possibly dioxymethylene, methoxy groups) in the three cases. In the selectivity determining step, methoxy groups desorb associatively as methanol on Cu–ZnO–Al 2 O 3 . Methoxy groups are selectively hydrogenolyzed to methane over Ni–Al 2 O 3 . Over Co–Al 2 O 3 oxygenated surface species may be involved in the chain growth to give C 2+ compounds. It is possible that this mechanism coexists with the via -carbide all-metallic catalysis reported for methanation and FT synthesis, on the basis of studies performed on pure metals.