CO2 hydrogenation over metal/zirconia catalysts
Metal/zirconia catalysts have attracted considerable interest for the hydrogenation of carbon dioxide. Various preparation methods such as impregnation, co-precipitation, sol–gel synthesis, and controlled oxidation of amorphous metal alloys have been used, leading to catalysts with very different properties. The catalytic behaviour of these materials is greatly influenced by the active metal and by the interfacial contact area between the metal and zirconia. Cu and Ag catalyse mainly methanol formation, while methane is formed over, e.g., Ni, Ru and Rh. Examples for less reactive metal constituents are Pd, Rh, Pt and Au, catalysing simultaneously the formation of methanol, carbon monoxide (by reverse water–gas shift reaction) and methane. The structural and catalytic properties of the various catalysts are compared and possible reaction pathways are discussed.