USE OF THE METHANOL DECOMPOSITION REACTION FOR IDENTIFYING SURFACE SPECIES IN CU CO-BASED CATALYSTS/

Methanol decomposition was used as test reaction for characterizing Cu /Co-based catalysts. Three Cu/Co/Al ternary catalysts containing Co/ ( Cu + Co) molar ratios of 0.34, 0.49, and 0.67, respectively, were prep ared. Two binary reference samples containing Co/Al and Cu/Al, respect ively, were also prepared. Methanol decomposition on binary Co/Al samp le gave predominantly CO, CH4, and higher hydrocarbons; the active sit es were metallic Co crystallites, the Co(n+) ions being almost inactiv e. Main products on binary Cu/Al sample were methyl formate, CO, and C O2. Both, CuO and Cu(n+) sites were active. The methanol decomposition mechanism was interpreted in terms of a reaction scheme based on the initial dehydrogenation of methanol to formaldehyde and the consecutiv e decomposition of the formaldehyde intermediate to different products according to the nature of the Cu or Co active site involved. The tes t reaction was specifically used to investigate the effect of both the chemical composition and the calcination temperature on the generatio n of surface species of ternary Cu/Co/Al samples. Good agreement was f ound between the conclusions obtained from catalytic testing and those from sample characterization by means of bulk and surface techniques (X-ray diffraction, temperature programmed reduction, and X-ray photoe lectron spectroscopy). Methanol decomposition proved to be a useful te st reaction for discriminating between Cu and Co sites on Cu/Co-based catalysts.