Study On Hydrothermal Synthesis Of Molecular Sieves And Removal Of Trace Olefin From Aromatic Hydrocarbons With Clay

Aromatic hydrocarbon is an important basic organic chemical raw material,which contains trace olefin in catalytic reforming production,which not only affects the long period and safe operation of the unit,but also affects the quality of aromatic products and subsequent processing,so it needs to be removed to a certain content.Adsorptive refining is one of the methods commonly used in industry to remove trace olefin from aromatic hydrocarbons.Granular clay,modified clay and molecular sieve can be used for fine adsorption preparation.Granular clay and modified clay have the characteristics of easy access to raw materials and low price,but they also have the problems of short life and not easy to regenerate.Special molecular sieve adsorption preparation has high olefins removal activity and can be regenerated for 2～3 times,but the price is high and the one-time investment of the device is large.In this study,industrial granular clay was selected and treated at different roasting temperatures.XRD,BET,Py-IR,NH₃-TPD,TGA characterization and titration analysis were performed,and the results showed that:Particles with the increase of calcination temperature,the montmorillonite clay content decreased,the content of quartz,active silica content increase after fall first,activated alumina aluminum content gradually reduce,specific surface area and entrance are diminishing,acid B and L acid in the acid strength gradually reduce,roasting temperature below 400℃,the highest active silica content.NaY molecular sieve was synthesized from calcined granular clay by in-situ crystallization,ammonium chloride as exchange agent,and HY molecular sieve was prepared by two-crossing and two-baking process.XRD,BET,Py-IR and NH₃-TPD were used to characterize HY zeolites synthesized in situ from granular clay under different conditions.The deolefin performance of C₈⁺aromatics produced by catalytic reforming was evaluated.The results showed that when the amount of guide agent was 14%,Under the conditions of Na₂O:Al₂O₃:Si O₂:H₂O=17:1:6:561,crystallization temperature of 100℃,crystallization time of 24h,HY molecular sieve has good physical and chemical properties and deolefin performance.The HY molecular sieve was treated with citric acid,and the samples prepared under different treatment conditions were characterized by XRD,BET,Py-IR and NH₃-TPD.The performance of deolefin removal was evaluated with C₈⁺aromatic hydrocarbons produced by catalytic reforming as raw materials.The results showed that the suitable conditions for treating HY molecular sieve with citric acid were as follows:The concentration of citric acid was 0.3mol/L,the volume ratio of citric acid（molecular sieve mass:volume of citric acid）was 1:10,the acid treatment temperature was 90℃,and the acid treatment time was 3h.