Oxidative Fluorination of Cu/ZnO Methanol Catalysts.

The influence of a mild difluorine treatment on Cu/ZnO precatalysts for methanol synthesis was investigated. It led to the incorporation of 1.2…1.3±0.1 wt % fluoride into the material. Fluorination considerably increased the amount of ZnOx related defect sites on the catalysts and significantly increased the space-time yields. Although the apparent activation energy EA,app for methanol formation from CO2 and H2 was almost unchanged, the EA,app for the reverse water-gas shift (rWGS) reaction increased considerably. Overall, fluorination led to a significant gain in methanol selectivity and productivity. Apparently, also the quantity of active sites increased.