Theoretical Study Of Adsorption Performance And Reaction Mechanism Of Tetralin On Y Zeolite

The continuous deterioration of petroleum resources,increasing demand for light oil products and increasing requirements of environmental protection laws and regulations on clean oil production make the development of new combined process of cycle oil hydrogenation and catalytic cracking increasingly urgent.The high-efficiency conversion of naphthenic aromatic hydrocarbons generated in the hydrogenation of cycle oil is the core issue of the new process,and its reaction mechanism affects the development of catalytic cracking catalyst and optimization of process conditions.Theoretical calculation has incomparable advantages than experimental study of reaction mechanism.In this paper,tetralin is used as a model compound of naphthenic aromatic hydrocarbons,and its adsorption and reaction mechanism on Y zeolite are studied.Molecular simulation technology can explain the mechanism by simulating experimental phenomena and lay a theoretical foundation for experiments.In this paper,Materials Studio software is used for quantum chemistry calculation,and the influence of Si/Al ratio on zeolites acidity and adsorption properties of tetralin,the reaction mechanism of tetralin molecules in Y zeolite,and the influence of phosphoric acid modification on zeolite acidity and tetralin cracking reaction are mainly studied.As for the influence of Si/Al ratio on the acidity and adsorption properties of tetralin,it is found that the change of Si/Al ratio on the acidity density and acid strength of zeolites presents the opposite rule.The decrease of Si/Al ratio can improve the acidity density of zeolite,but it will weaken the acidity strength of acid sites.Besides,the decrease of Si/Al ratio will lead to the increase of adsorption performance of tetralin,that is,the acid density in the acid properties of zeolite has a positive influence on the adsorption performance.For the study of tetralin reaction mechanism,tetralin reaction is divided into cracking reaction and dehydrogenation reaction in this paper.The calculated reaction potential energy diagram shows that the distribution of primary cracking and secondary cracking products is related to the experimental temperature.Comparing the energy barriers of cracking and dehydrogenation reactions,monomolecular dehydrogenation>primary ring opening>bimolecular dehydrogenation,indicating carbonium ion tends to undergo bimolecular dehydrogenation reaction,which is matched with the overall product distribution of the experiment.Phosphoric acid modification can affect the acid strength of zeolites.Through the study of deprotonation energy and NH₃adsorption energy,it can be seen that phosphoric acid modification reduces the acid strength of Bronsted acid sites.The cracking reaction activity of tetralinβfracture was studied.the results showed that phosphoric acid modification was beneficial to the occurrence of tetralin ring-opening reaction,that is,to improve the reaction activity.