Copper-zinc catalysts.: X.: Comparison of preparation methods:: co-precipitation, successive precipitations or use of bimetallic precursor

The comparison of different preparation procedures of Cu-ZnO catalysts has disclosed the formation of an unidentified copper-zinc phase in the case of precipitation methods. The size of the copper crystallites obtained after reduction is clearly related to the amount to this phase. Moreover, the catalytic activity in methanol synthesis from CO + CO2 + H-2 mixture depends on the intermediate formation of this phase. The bimetallic precursor leads to catalyst that displays a lower activity correlated to sintering of copper during the reduction step.