The Promotion Effect of Transition Metals on Water-Tolerant Performance of Cu/SiO2 Catalysts in Hydrogenation Reaction

The effect of transition metals (Fe, Co, Ni, Zn) on water-tolerant performance of Cu/SiO2 catalysts in hydrogenation reaction at industrially relevant conditions (containing water) was investigated. Notably, an improvement in the water-tolerant hydrogenation performance, indexed by the decrease in the reaction temperature (from 280 to 240 degrees C) was achieved. The HRTEM showed the existence of crystal defects which formed at the border of copper species and doping metal species. Furthermore, XRD of catalysts after reaction showed the peak shift was existed, indicating crystal defects were existed in the reaction. From the result of Cu LMM and TPR, the doping of metal element could also increase the value of Cu+/(Cu-0+Cu+) by adjusting the interaction between copper ion and silica. The in-situ DRIFT visually showed the promotion effect of doping meal on hydrogenation reaction. Combined with hydrogenation performance, it could be found crystal defects and high Cu+/(Cu-0+Cu+) were main factors to improve hydrogenation performance of Cu/SiO2 catalyst, which provided more active sites at relative low temperature and then improve the water-tolerant performance. Furthermore, it was found the size of Cu+/(Cu-0+Cu+) took major responsibility for the improvement of hydrogenation performance, and crystal defects played an auxiliary role. The Cu-Zn/SiO2 catalyst showed the best water-tolerant hydrogenation performance with a high conversion and stability at low temperature reaction conditions.