Steam reforming of methanol on binary Cu/ZnO catalysts: Effects of preparation condition upon precursors, surface structure and catalytic activity

Precursors for Cu/ZnO catalysts, with Cu/Zn molar ratios in the range from 100/0 to 0/100, were prepared by two coprecipitation methods. These methods differ by the addition rate of a mixed Cu(NO3)(2)/Zn(NO3)(2) solution to a NaHCO3 solution. Characterisation by powder X-ray diffraction (PXRD), differential thermal analysis (DTA), thermal gravimetric analysis (TGA), FT-IR and UV/VIS spectroscopies indicated that the structure of precursors with Cu/Zn ratios in the range of 30/70 to 70/30 depends greatly upon the addition rate of the mixed solution. Amorphous copper hydroxycarbonate and sodium zinc carbonate were formed prior to the various precursors such as malachite, aurichalcite and hydrozincite. The Cu/ZnO catalysts subsequently formed from the precursors showed the activity for steam reforming of methanol to vary with its composition. Based on the results of temperature programmed oxidation (TPO) with N2O and an infrared spectra of CO chemisorption, the TOF of the reaction is proposed to be associated with the surface of metallic Cu.