METHANOL SYNTHESIS OVER COPPER AND ZNO PROMOTED COPPER SURFACES

Methanol synthesis has been studied in fixed beds of unpromoted Raney copper, zinc oxide promoted Raney copper and a commercial low pressure Cu-ZnO-Al2O3 methanol synthesis catalyst at 523 K and 4.5 MPa using s ynthesis gas containing various CO2/CO ratios, while keeping the H-2/( CO2 + CO) ratio constant. All catalysts produced similar patterns of c arbon dioxide and carbon monoxide conversions with increasing space ve locities. carbon monoxide conversions were initially low, for synthesi s gas containing CO2/CO ratios less than one and did not achieve maxim um values until the conversion of carbon dioxide had reached a constan t level (approaching thermodynamic equilibrium for the zinc oxide prom oted catalysts). For synthesis gas containing CO2/CO ratios higher tha n one, carbon monoxide conversions were depressed by carbon dioxide hy drogenation. The results suggest that ZnO is an essential component fo r higher methanol activities. Hydrogenation of carbon dioxide and carb on monoxide takes place on the copper surface and the carbon monoxide hydrogenation appears to require activation resulting from carbon diox ide hydrogenation.