Reduction processes in Cu/SiO2, Co/SiO2, and CuCo/SiO2 catalysts

Cu/SiO2, Co/SiO2, and bimetallic CuCo/SiO2 catalysts have been synthesized and their reduction behavior characterized by TPR, in situ XRD, and in situ XANES. In Cu/SiO2, a two step reduction process, CuO → Cu2O → Cu0, occurred. Two forms of the intermediate Cu2O with different degrees of reducibility were observed. Addition of cobalt to Cu/SiO2 resulted in formation of an amorphous fraction of CuO that was more easily reducible than crystalline CuO. Cobalt addition also prevented formation of the less reducible form of Cu2O. Addition of copper to Co/SiO2 increased the reducibility of Co3O4, and to greater extent of the intermediate CoO, which in the monometallic Co/SiO2 was less readily reduced due to interaction with the support.