Preparation Of Non-precious Metal Cobalt-based Catalysts And Research On Their Application In Propane Dehydrogenation

The direct dehydrogenation of propane（PDH）has been industrialized,and the catalysts used in the process are focused on Pt-based and CrOx-based catalysts.However,the high price of Pt and hypertoxicity of CrOx restrict the development of PDH industry to some extent.These factors have driven researchers to find alternatives which are environmentally friendly and non-precious.Cobalt has relatively low toxicity,earth abundance and diverse chemical reactivity.However,it is rarely used in the study of direct dehydrogenation of propane.This subject aims to study the preparation of cobalt-based catalysts and their performance in propane dehydrogenation reaction.A series of Co-based catalysts were designed and synthesized in this paper for direct dehydrogenation of propane.The catalysts were characterized by XRD,TPR,TEM,XPS and TG,and the structure-performance relationship of the catalysts was established.Firstly,SmCoO₃ supported on different carriers were prepared by incipient wetness impregnation combined with citrate complexing method,such as SmCoO₃/ZrO₂,SmCoO₃/SiO₂ and SmCoO₃/Al₂O₃.The effects of different carriers on the dehydrogenation performance of Co-based perovskite were investigated.The results show that the presence of the carrier is beneficial to changing the catalytic effect of perovskite from cracking to dehydrogenation.The carrier is favorable for the dehydrogenation reaction.The effect of Al₂O₃ is the best.The propane conversion reaches 25%and the propylene selectivity reaches 95%.This is due to the proper interaction between the Al₂O₃ support and SmCoO₃ perovskite,leading to a good dispersion of perovskite crystallites.Then,the effects of different A-site ions(La³⁺,Pr³⁺and Sm³⁺)on the dehydrogenation performance of Co-based perovskite were investigated.The results show that the dehydrogenation effect was best when the A-site ions were Sm³⁺ions.The optimal catalyst（SmCoO₃/Al₂O₃）and the SmCoO/Al₂O₃catalyst prepared by the conventional co-impregnation method were compared for the catalytic performance.Combining it with the structure comparison based on the characterization results,the paper explores the effect of perovskite structure on the dehydrogenation performance of Co-based catalysts.The results show that small and dispersed perovskite microcrystalline nanoparticles are synthesized through the pore limits of alumina.This interaction between the support Al₂O₃ and SmCoO₃ NPs restrains the reduction of Co²⁺to Co⁰,and at the same time exposes more active cobalt nanoparticles on the catalyst surface,thus achieving good catalytic performance.In the meantime,its carbon deposits are far less than those of the SmCoO catalyst prepared by conventional co-impregnation method.Finally,the effects of different preparation methods on the structure of single-component Co-based catalysts and propane dehydrogenation performance were studied.It was found that the change of preparation methods had a significant effect on the reaction stability of the catalyst.Co-based catalyst prepared by the sol-gel method is stable.The conversion of propane is 15%,the selectivity of propylene is 95%,and it can be stabilized for 14h.The reason for the good stability is that they have a small specific surface area,strong resistance to carbon deposition and partial coverage of the Al₂O₃ support and active components.