Catalytic Hydrogenation Of Ru/SiAl-TiO₂ For The Depolymerization Of Diphenyl Ether

The purpose of our work is to understand the active site information of hydrolyzed diphenyl ether reaction,and to develop inexpensive and readily available catalysts for further application in industrial production in the future work,so as to explore a feasible path for efficient and clean utilization of lignite.Lignite contains a large number of aromatic units connected by C_aryl-O and C-C bonds,so the research of this subject has high value.The C_aryl-O bond energy in lignite is low,and Ru-based dual-function catalyst shows excellent hydrodepolymerization performance in lignite hydrodepolymerization reaction.Therefore,a series of noble metal dual-function catalysts were designed and prepared in this dissertation,and the catalytic performance of catalytic hydrogenation depolymerization of diphenyl ether,which is a coal-like structure model compound containing ether oxygen bridge bond,was studied under mild conditions.The specific research contents are as follows:（1）ASA-TiO₂ composite support was synthesized,and Ru₅/ASA-TiO₂ catalyst was prepared by impregnation method.Using diphenyl ether as model compound of lignite,the hydrodepolymerization activity of Ru₅/ASA-TiO₂ catalyst was investigated under mild conditions.In addition,it has been confirmed that the reaction temperature can affect the relative content of each type of acid so as to significantly affect the selectivity of hydrodepolymerization products of diphenyl ether.The distribution of hydrodepolymerization products of diphenyl ether at low temperature is mainly alkanes,and the products at high temperature are mainly aromatics.At the same time,the acidity of the prepared catalyst was investigated by pyridine adsorption infrared（Py-IR）and ammonia temperature programmed desorption（NH₃-TPD）,and it was confirmed that the catalyst with lower BA/LA value can effectively improve the conversion rate and benzene yield of hydrodepolymerization of diphenyl ether.In addition,pyridine adsorption infrared characterization also confirmed that the introduction of active metal Ru on the surface of ASA-TiO₂ can increase the content of Lewis acid on the surface of the material.（2）The HZSM-TiO₂ composite support was prepared,and Ru₅/HZSM-TiO₂ was prepared by impregnation method.The performance of the catalyst was evaluated by hydrogenation depolymerization of diphenyl ether under mild conditions.Meanwhile,by means of Py-IR and NH₃-TPD,it was found that catalysts with lower BA/LA value and moderate acid total amount had better reactivity.In addition,the properties of the prepared catalyst were investigated by TEM and XPS characterization,and it was found that a new Ti-O-Si and/or Ti-O-Al bond was formed in 1HZSM-1TiO₂,which may be caused by the interaction between HZSM-5 molecular sieve and TiO₂.The formation of new bonds may also be one of the factors that makes the catalyst exhibit excellent reactivity.（3）In this chapter,we compound TiO₂ with HZSM-5 molecular sieve and explore the influence of different composite methods on the mechanism of action of catalyst in hydrodepolymerization of diphenyl ether.In this section,several Ru-based catalysts were prepared by different compounding methods,and they were also applied to the hydrogenation depolymerization of diphenyl ether under mild conditions,and the reactivity of the catalyst was investigated.Ru₅/TiO₂-8HZSM showed the highest catalytic activity.The experimental results show that TiO₂ on HZSM-5 surface can enhance the selectivity of aromatics products in hydrodepolymerization reaction.The acidity properties of the catalysts prepared were investigated by means of NH₃-TPD and Py-IR.The characterization results showed that the surface acidity distribution and acid strength of the catalysts were significantly affected by different compounding methods.Among them,the Lewis acid strength and BA/LA value of the catalysts significantly affected the reactivity and aromatics product selectivity of the hydrodepolymerization of diphenyl ether.