SUPPORT AND MORPHOLOGICAL EFFECTS IN THE SYNTHESIS OF METHANOL OVER CU/ZNO, CU/ZRO2 AND CU/SIO2 CATALYSTS

Copper catalysts supported on ZnO, SiO2 and ZrO2 have been prepared and the copper surface areas determined using the technique of frontal chromatography. The activities of the catalysts for the synthesis of methanol from CO/CO2/H2 and CO/H2 mixtures have been determined at 10 and 40 bar pressure and in the temperature range 250-270°C under conditions of continuous flow. The results show a clear support effect in both reaction mixtures and at both pressures. Under our experimental conditions there is no correlation between the copper surface area and the activity for the synthesis of methanol. Instead we observe that the activity of a Cu/ZnO catalyst is between 10 and 30 times higher per unit copper area than is the activity of a Cu/SiO2 catalyst. Cu/ZrO2 catalysts are intermediate in activity. It is concluded that support effects can strongly influence the activity of copper in the methanol synthesis reaction at elevated pressures. Possible explanations in terms of the morphology of the copper particles and the structure sensitivity of the reaction are discussed.