Catalysts Of Pt-Cu Alloy Supported On CeO₂ Modified Hydrotalcite For Propane Dehydrogenation

Propene is an important chemical raw material.With the development of economy,the demand for propene is increasing.In recent years,the direct dehydrogenation of propane to propene is considered to be the most competitive technology.The Pt-based catalysts have been extensively utilized in propane dehydrogenation because of their high catalytic activity and excellent selectivity.However,supported Pt catalysts still suffered from remarkable deactivation caused by carbon deposit and sintering of active species at high temperature.In this work,a series of PtCuCeMgAl hydrotalcite-like precursors were synthesized by one-pot method,in the light of characteristics of uniformly dispersed metallic components at atom level,lattice confine and topological transformation.And CeO₂ modified Mg?Al?O supported Pt-Cu alloy were obtained by lattice confined calcining and reducing the corresponding precursors.The catalytic performances were evaluated by propane dehydrogenation.The effects of preparation method and Ce content on the catalysts structure and catalytic performances were systematically investigated.Also,preparation conditions as well as reaction conditions have important effects on the catalytic performance,which were discussed in this paper.Firstly,the PtCuCeMgAl hydrotalcite-like precursors were prepared by one-pot synthesis,then the supported Pt-Cu alloy catalysts?i.e.,PtCu/Ce_xMgAl-R?were obtained by calcining and reducing the precursors.The structure and physicochemical properties of the catalysts and their precursors were characterized by XRD,TPR,BET,TEM,CO chemisorption,XPS,ICP-OES and TG techniques and the catalytic performances were evaluated on propane dehydrogenation processes to study the structure-activity relationship of the catalysts.The results show that in PtCu/Ce_xMgAl-R catalysts,Pt-Cu alloy nanoparticles with high dispersion and small particle size were uniformly distributed on the surface of CeO₂ modified Mg?Al?O support,which is the key to improving the catalytic performance on propane dehydrogenation processes.At the same time,CeO₂ can effectively inhibit the formation of coke deposit on the active sites,which can further increase the stability of the catalysts.The Ce content has an obvious effect on the catalytic performance of the catalysts.When the Ce content is 0.3wt%the catalyst exhibits the highest activity with its propane conversion higher than45%and propene yield above 40%under the reaction conditions of 600?,atmospheric pressure,C₃H₈/H₂/N₂ molar ratio=8/7/35,and WHSV=3 h^-1.In order to explore the optimal catalytic performance,the effects of calcination temperature and reaction conditions on the catalytic performance of PtCu/Ce_0.3MgAl-R catalysts were studied.The catalysts were characterized by BET,XRD,TPR and other techniques,and the catalytic performances of the catalysts were evaluated by propane dehydrogenation reaction.The results show that the catalyst with large specific surface area and the smallest metal particle size can be obtained by calcination at 550?.The best catalytic performance happens at the calcination temperature of 550? and reduction temperature of 580? for 2h.