SUPPORT EFFECTS IN METHANOL SYNTHESIS OVER COPPER-CONTAINING CATALYSTS

Cu/ZnO/Al2O3 (CZA), Cu/ZnO/SiO2 (CZS) and Cu/ZnO/activated carbon (CZC) impregnation catalysts were studied with respect to their catalytic activity in the synthesis of methanol from CO/H-2 and CO/H-2/CO2. Temperature-programmed reduction (TPR) indicated the presence of copper not only on the support but also in interaction with ZnO in all three types of catalysts. During methanol synthesis from CO/H-2/CO2, both the copper surface areas and the activities of the low-zinc CZC catalysts decreased rapidly due to the weak interaction between copper and carbon. The presence of larger amounts of zinc had a stabilizing effect on both the copper surface area and the activity. The CZS catalysts exhibited a slow increase in activity with process time. The activity of the CZA catalysts remained quite stable during the experiments. In methanol synthesis from CO/H-2, the activity of all catalysts was lower than in CO/H-2/CO2, while the nature of the support had a large influence on the activity: the activity of copper on SiO2 or on activated carbon was much lower than that of Al2O3- or ZnO-supported copper. In contrast, the activity in CO/H-2/CO2 appeared to be much less dependent on the choice of the support.