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 ZnO_x related defect sites on the catalysts and significantly increased the space-time yields. Although the apparent activation energy E_A,app for methanol formation from CO₂ and H₂ was almost unchanged, the E_A,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.