Comments on "The effect of ZnO in methanol synthesis catalysts on Cu dispersion and the specific activity" - [by T. Fujitani and J. Nakamura]

Fujitani and Nakamura recently reported on the effect of ZnO on Cu/ZnO methanol synthesis catalysts (Catal. Lett. 56 (1998) 119). Having measured the methanol synthesis activity of a series of Cu/ZnO catalysts of different Cu/ZnO ratios, they reported a linear relationship between the copper metal area and the methanol yield (implying a fixed value of the copper specific activity) and paradoxically they also reported a volcano-type relationship between the copper specific activity in methanol synthesis and the ZnO content. This paradox is resolved by showing that their Cu/ZnO catalysts fall into two groups: (i) the low-surface-area copper catalysts which have a specific activity of 10 mg CH3OH/m(2)-Cu h and (ii) the high-surface-area copper catalysts which have specific activity of 14.8 mg CH3OH/m(2)-Cu h. These different specific activities derive from different surface morphologies of the copper in these catalysts.