Studies of the role of the copper promoter in the iron oxide/chromia high temperature water gas shift catalyst

A study of the role of the copper promoter in the iron oxide/chromia high temperature water gas shift reaction is reported and discussed. The rate of reaction using both CuO/Fe3O4/Cr2O3 and Fe3O4/Cr2O3 catalysts is zero order in H2O and first order in CO over a wide range of reactant compositions and reaction pressures. The activation energy for the Fe3O4/Cr2O3 catalyst is found to be 118±9 kJ mol−1 which is in agreement with previous literature data. The addition of CuO to the Fe3O4/Cr2O3 catalyst significantly decreases the activation energy to ca. 75–80 kJ mol−1. TPR studies using H2/He and H2/CO indicate that the addition of CuO partially stabilises the catalyst with respect to reduction with CO, indicating that one role of CuO as a promoter is to permit the use of higher partial pressures of CO in the reactant gases. Model experiments with CH3OH/CO mixtures show that the addition of CuO to the Fe3O4/Cr2O3 catalyst promotes the formation of methyl formate significantly. Based on these findings, the possible role of CuO in the promoted catalyst is discussed.