Abstract: | Cu/ZnO catalysts (with a Cu/Zn atomic ratio of 30/70) have been prepared by high intensity mechanical mixing of copper and
zinc oxide powder in air and under vacuum. During milling in vacuum gradual amorphisation of the constituents occurs, as evidenced
by broadening of the Cu0 and ZnO diffraction peaks in XRD, but the two original phases remain. The result of such treatment is a catalyst with low
BET area and low Cu metal surface area. Consequently, the activity of the vacuum milled samples in batch methanol production
from synthesis gas (CO/CO2/H2=20/5/75) at 50 bar and 250°C is low. Milling in air leads to oxidation of the copper metal phase and much higher BET surface
area and, after reduction, Cu metal surface area. Prolonged milling times in air result in more than 90% Cu2+ formation as evidenced by TPR. Activity in methanol synthesis for the air milled samples is comparable to a conventional
Cu/ZnO catalyst prepared by coprecipitation. It is concluded that high intensity ball milling at ambient conditions is a promising
method to prepare mixed oxide catalysts or catalyst precursors.
This revised version was published online in July 2006 with corrections to the Cover Date. |