THE SYNTHESIS OF ALCOHOLS USING CU ZNO/AL2O3+(CE OR MN) CATALYSTS/

Cu/ZnO/Al2O3 catalysts modified by compounds of manganese or cerium we re prepared by coprecipitation or by impregnation and were tested for the synthesis of alcohol mixtures from synthesis gas at pressures of u p to 70 bar. They were also examined by XPS both before and after the reaction. With both the impregnated and the coprecipitated catalysts, manganese increased the selectivity to higher alcohols (mainly isobuta nol). However, in the case of cerium, the location of the cerium ions appeared to determine the selectivity; it shifted towards alkanes and CO2 when cerium was present at the surface of the catalyst (probably a s CeO2), but to isobutanol when the cerium ions were present in the bu lk. Changes were found in the selectivities of the catalyst doped with cerium with time on stream and these could be explained by a segregat ion of the cerium ions to the surface. Some of the mechanistic steps i n the formation of higher alcohols as proposed in the literature were confirmed.