Pt/HZSM-5基催化剂双功能协同性对正丁烷催化裂解反应机制的影响

The effect of bifunctionality synergy of Pt/HZSM-5 based catalyst on reaction mechanism of n-butane catalytic cracking

轻质烷烃结构稳定,化工利用率低.催化裂解轻质烷烃是其高值利用的重要途径,相关研究同时对C-C键和C-H键活化和演变调控具有重要意义.本文在基于原子层沉积法构建高稳定Pt/HZSM-5基双功能模型催化剂的基础上,研究了不同酸性HZSM-5分子筛引入脱氢组分Pt对反应路径及目的产物低碳烯烃的影响规律.研究发现,双功能催化剂中, Pt的脱氢性能与分子筛的酸性裂解性能存在协同作用,不同硅铝比的分子筛上引入Pt,高硅铝比分子筛上Pt的引入对脱氢促进效应更明显.同时,将脱氢组分Pt引入到不同裂解能力的酸性分子筛载体上,会改变其低碳烯烃的生成路径,高硅铝比的分子筛上引入Pt后丁烯的生成路径增强,而低硅铝比的分子筛上则会增强乙烯与丙烯的生成路径,当分子筛硅铝比继续降低时,乙烯的生成路径进一步增强.本研究对多相复杂反应中反应路径调控及高效双功能催化剂设计具有指导意义.

Light alkanes are stable,and they are not fully utilized in chemical industry.Catalytic cracking is an important process for the valorization of light alkanes,and the related study is also of significant importance for the activation and evolution regulation of C?H bond and C?C bond.In this work,on the basis of highly stable Pt/HZSM-5based bifunctional model catalysts constructed by atomic layer deposition,the dehydrogenation component Pt was introduced onto HZSM-5 zeolites with different acidic properties,and their influences on the reaction pathways and formation of targeted light olefins were studied.It was found that the dehydrogenation function of Pt and cracking role of acidic HZSM-5 zeolites work in synergy.Among the catalysts with the introducing of Pt onto HZSM-5 zeolites with different SiO_(2)/Al_(2)O_(3)ratios,the dehydrogenation effect brought by metal introduction onto zeolite with high SiO_(2)/Al_(2)O_(3)ratio is stronger than those introduced onto the ones with low SiO_(2)/Al_(2)O_(3)ratios.Meanwhile,the introducing of dehydrogenation component onto acidic supports with different cracking abilities would also vary the formation pathways of light olefins.Specifically,with introducing Pt,the pathway of butene formation is enhanced on zeolite with high SiO_(2)/Al_(2)O_(3)ratio,while the pathways of ethene and propene formation are strengthened on zeolites with low ones.With further decreasing SiO_(2)/Al_(2)O_(3)ratio,the pathway of ethene formation is mainly enhanced.The present study is expected to provide guidance for the regulation of reaction pathways and future design of efficient bifunctional catalysts for complex heterogeneous reactions.