Characterization of Cu/SiO2 catalysts prepared by ion exchange for methanol dehydrogenation

A series of copper on silica catalysts prepared by using the ion exchange methods with copper loadings between 0.45 and 3 wt% have been studied by means of different techniques such as TPR, EPR, XANES, XRD, XRE BET and methanol dehydrogenation reaction. The TPR patterns showed two well-defined peaks with maxima between 250-350 degrees C and 600-650 degrees C. The first one (peak I) corresponds to two contributions: (i) the one step reduction (Cu2+ to Cu-0) of a low interacted species (S-1), and (ii) the partial reduction (Cu2+ to Cu1+) of a highly dispersed and surface interacted species (S-2). The second TPR peak (peak II) observed at a higher temperature corresponds to the second step reduction (Cu1+ to Cu-0) of the S-2 species. In addition, it has been found out that Cu-0 and not Cu2+ is the active site for methanol dehydrogenation to methyl formate. (C) 1997 Elsevier Science B.V.