Cobalt–manganese oxide water-gas shift catalysts. A kinetic and mechanistic study

Abstract

An investigation of the mechanism of the water-gas shift reaction over a cobalt–manganese oxide catalyst (Co: Mn = 1:1) is described using both kinetic and model reagent studies. The reaction of methanol, ethanol and formic acid are discussed, and these reagents are used as model reactants to probe the reaction mechanism. Based on these kinetic and model reactant studies a mechanism for the water-gas shift reaction is proposed for this catalyst system. It is considered that the mechanism proceeds according to the following steps : (i) water dissociatively adsorbs to form surface hydroxy and hydride species, (ii) subsequent CO adsorption and oxidative addition of the surface hydroxy species lead to the formation of a surface formate species, (iii) decomposition of the formate species via β-elimination to give gas-phase CO₂ and surface hydride and (iv) combination of two surface hydride species giving gas-phase H₂.