Deactivation feature of Cu/SiO2 catalyst in methanol decomposition

Abstract

The deactivation of Cu/SiO2 catalyst in methanol decomposition, which demonstrated a unique characteristics with time on stream, was studied in this paper. Based on the variation of methanol conversion, three catalyst samples with different testing time were obtained, enabling dynamic investigation of the deactivation process in three stages. These samples were fully characterized by BET, ICP-OES, XRD, TEM and H2-TPR techniques. The results indicated that copper sintering, coking and loss of silica all contributed to the catalyst deactivation during the whole reaction process. It was found that the rate of both copper sintering and silica loss decreased with increasing the reaction time, while the coking rate decreased initially from 0 h to 200 h and then increased in the final stage from 200 h to 296 h. The catalytic performance of regenerated samples showed that the deactivated catalyst with different testing time had nearly the same initial activity, but revealed a big change with time on stream, especially for the 296 h tested sample. The findings obviously revealed that sintering of Cu slowed down while silica loss continued at decreased rate after testing for 200 h, and the increased rate of coking might be due to structural change of the catalyst. It was also found that the loss of silica had an accumulating effect, i.e. drastic change of catalyst texture could be made due to gradual loss of silica, which in turn led to fatal catalyst deactivation.