Impregnation of Controlled-Porosity Silica: Cu/Sio2, Co/SiO2 and Cu-Co/SiO2 Investigation of the Parameters Affecting Selectivity in CO Hydrogenation

Abstract

Silica spheres of controlled pore size (83% of pores between 6–10nm in radius) were impregnated with aqueous nitrate solutions to give 8%Cu/SiO2, 8%Co/SiO2 and 8%Cu-4%Co/SiO2. Temperature-programmed reduction, microprobe analysis, and propane hydrogenolysis all indicated that the Cu and Co in the bimetallic catalyst were in intimate contact. In the catalysis of CO hydrogenation rate of CO conversion increased in the sequence:

Cu/SiO2 < Cu-Co/SiO2 < Co/SiO2

while selectivity to methane increased in the same sequence (and selectivity to methanol decreased). These selctivity trends are to be expected since the ability of Co to dissociate CO and produce methane is well known. However, none of these catalysts produced significant amounts of ethanol. Therefore the study of these idealised catalysts suggests that Cu-Co interactions are not sufficient to induce selectivity to ethanol in CO hydrogenation at 523K and 2MPa but must also require an interaction with a ZnO or Al2O3 component in the full catalyst.