Study On The Preparation And Modification Of Cu/SiO₂ Catalysts For DME Steam Reforming To Produce Hydrogen

Hydrogen?H₂?is a new kind of sustainable energy sources.Dimethyl ether steam reforming?DME SR?is a very effective way to produce hydrogen.The key technology of this reaction is the development of catalysts,and the enhancement of the catalyst activity at low temperature and selectivity are the main difficulties that the current researchers need to overcome.In this work,the copper phyllosilicate with unique lamellar structure was prepared by ammonia evaporation method and the DME SR reaction over the copper phyllosilicate,which was mixed with solid acid??-Al₂O₃?was investigated.The effects of copper loading and doping modification on the catalytic performance are systematically investigated.Multiple techniques,such as XRD,BET,N₂O chemisorption,FTIR,XPS and H₂-TPR,were employed to characterize the catalysts.The characterization results and the activity test results were well correlated.The Cu/SiO₂ catalysts with different Cu content were prepared by ammonia evaporation method.The mechanism of the formation of the copper phyllosilicate and the effect of Cu loading on DME SR were studied in detail.The results of the activity tests show that this catalyst prepared by this method has better catalytic activity at low temperature?380 ^oC?than the catalyst prepared by impregnation method,and the catalyst with the Cu content of 30%exhibits the best catalytic performance.The XRD results show that the catalyst prepared by this method has highly dispersed Cu species.The XPS results show that the Cu⁰/Cu⁺ratio on the catalyst surface increases with the increase of Cu loading.Through the TOF calculation,we propose that the DME SR reaction exhibits the best catalytic performance when Cu⁰/Cu⁺is close to 1.The Cu/SiO₂ catalyst prepared by ammonia evaporvation method is modified to achieve better catalytic activity and selectivity.A series of ZnO-modified Cu/SiO₂catalysts were prepared by excess impregnation method.The ZnO-modified catalyst exhibits lower CO selectivity and better stability than unmodified Cu/SiO₂ catalyst.According to the N₂O chemical adsorption and XPS results,the loading of Zn significantly affected the Cu⁰ and Cu⁺contents on the catalyst surface.The TOF results also show that the catalyst has the best catalytic performance when Cu⁰/Cu⁺is close to 1.The XPS,H₂-TPR and EDS characterizations show that there is a strong interaction between Cu species and ZnO on the reduced catalyst,which not only inhibits the reverse water gas shift reaction but also prevents the sintering of copper species.