Effect Of Metal-support Interaction On Catalytic Performance Of Co-based Catalysts In Propane Dehydrogenation

Propylene is an important commercial chemical used in the production of various products,such as polypropylene,propylene oxide,acetone,acrylonitrile and acrolein.With the increasing global demand for propylene and the huge propane reserves in shale gas,people are interested in catalytic propane dehydrogenation（PDH）to produce propylene.The commercial PDH process is mainly based on two technologies,namely Oleflex process using Pt Sn/Al₂O₃ catalyst and Catofin process using Cr/Al₂O₃ catalyst.For Pt-based catalysts,the electronic modification of additives and the specific interaction with the optimized support can improve the catalytic activity and stability.However,the high price of Pt metal and the serious toxicity of Cr-based catalyst greatly limit the further development of PDH process.Therefore,environmental friendly Co-based catalysts have attracted much attention because of their excellent C-H bond activation ability and high selectivity for olefins.In this work,the evolution of ZIF-67 derived Co-based catalyst with carbonization temperature was studied,and its catalytic performance in PDH was studied.The results showed that the PDH performance of the catalyst was significantly changed by adjusting the carbonization temperature.At lower carbonization temperature,Co/NC-T catalyst has higher propane conversion,but the products are mainly methane obtained from pyrolysis;When the carbonization temperature reaches 700℃,the catalyst has the highest propylene formation capacity.At this time,the space-time yield and selectivity of propylene can reach 592.6 kg/h/m_cat³ and 91.9%,respectively.Combined with the characterization results,it is found that the proportion of Co⁰ is positively correlated with STY（C₃H₆）,indicating that Co⁰ species play an important role in the dehydrogenation of propane to propylene.The carbonization temperature can effectively regulate the performance of the catalyst by adjusting the morphology and proportion of Co species.On this basis,to improve the regeneration property of the catalyst,a series of layered x Co/Al₂O₃ catalysts were prepared.By changing the Co loading,the interaction between Co species and support was regulated,and its effect on the catalytic performance of the catalyst in PDH was explored.XRD,SEM and XPS were used to characterize the interaction of Co-Al₂O₃ with different Co loading.The results showed that the Co loading could effectively adjust the proportion and morphology of various species in the catalyst.Further analysis of the catalytic induction period and the reasons for deactivation showed that the induction period was due to the production of surface metal Co species(Co³⁺→Co⁰)as the active site.