Preparation And Hydrocracking Performance Of Y Zeolite With High Si/Al Ratio

With the domestic crude oil becoming heavier,the more and more strictly on environmental laws and the growing requirements for clean oils,more and more attentions have been paid on hydrocracking technology.Hence,the production capacity of hydrocracking technology will be highly improved in the near future.The key of hydrocracking process is catalyst,while the capacity of hydrocracking is determined by pore structure and acidity property of catalyst.USY zeolites,with adjustable acid property,are widely used as the carrier.So,USY zeolites direct impact the hydrocracking property of the catalyst.The unit cell sizes of the USY can always impact the acid and stability properties of catalyst,which then impact the activity and selectivity of hydrocracking catalyst.In this study,the commercial USY zeolites were used as the matrix catalyst and then double reagents complex dealuminzation method was introduced to get small cell size of USY zeolites with high Si/Al ratio.The citric acid was used as the main dealuminzation reagent in this work.The citric acid-ammonium borofluoride and citric acid-EDTA were used as double complex dealuminzation system to get USY zeolites with high Si/Al ratio.In view of the unit cell size and crystal of USY zeolites,the concentration and ratio of citric acid and ammonium borofluoride,dealuminzation reagent dosage,reaction temperature and reaction time were investigated by single factor experiments to get USY zeolites with high Si/Al ratio.Then the optimum preparation condition was determined and scale-up experiments were also investigated in this condition to get the change of structure and property of USY zeolites.From the results we can see that,the cell parameters of the USY declined.Meanwhile,the framework Si/Al ratio and the volume of mesopores both increased.In view of the framework Si/Al ratio of USY zeolites,the concentration of citric acid and EDTA,reaction temperature and reaction time were investigated by orthogonal experiments to get the optimum preparation conditions in the citric acid-EDTA system.Then the scale-up experiments were also investigated in this optimum preparation condition.From the results we can see that,silicon-aluminum ratio of USY zeolites increases with stable crystalline.The results of the scale-up experiments in citric acid-EDTA system indicate that the samples with better crystal structure than the matrix USY zeolites were prepared by scal-up experimens.Preparation of two kinds of USY zeolite molecular sieves and commerce hydrocracking catalyst than gasoline fraction yield increased significantly,showing a better industrialization prospect.Compared with the commercial USY,the two kinds of dealumination Y zeolite have high gasoline yield and industrialization prospects.