A Study On Butylation Of Toluene Over Y Zeolite Catalysts

Aromatics alkylation production plays a very important role in the entire chemical industry.In recent years,as an important chemical raw material,p-tert-butyl toluene has been in continuously increasing demand.Therefore,the researches on toluene tert-butyl catalysts with high activity,high selectivity,and long life have attracted much attention.In this paper,toluene tert-butyl reaction was used as the probe reaction to study the influence of the zeolite types and the Si/Al ratio of HY zeolite on the catalytic performance of tert-butyl reaction,and the tert-butyl reactivity of core-shell structure zeolite HY@MCM-41 was also studied.The results of research are as follows:1.Performance research on the different kinds of zeolite catalyzing tert-butylation of tolueneThe catalytic performance is researched in the reaction of 4 kinds of zeolite such as HY(Si/Al=12)?USY(Si/Al=15)?HM(Si/Al=25)?HZSM-5(Si/Al=25)catalyzing the alkylation of toluene and tert-butanol.The experimental results show that: the order of catalytic activity of the 4 zeolite is HY?USY > HM > hzsm-5,which is not consistent with the order of total acid content HY > USY > hzsm-5 > HM,which indicates that the catalytic activity of zeolite is not only related to the type and number of acid centers,but also related to the pore structure of the zeolite.HY and USY both belong to FAU crystal structure with and the large acid content and the high catalytic activity,but the para-position selectivity of HY is significantly superior to USY,which is due to the situation that the excessive strong acid center of USY intensifies the side reaction.The total acid content of HM is small and the catalytic activity is low,but its para-position selectivity is the best due to the shape-selecting effect of the pore canal.Hzsm-5 has a large total acid content,but the size of pore canal is too small,which causes the reaction to take place only on the outer surface,so the catalytic activity is the lowest.The appropriate reaction conditions are defined by means of the research on the process conditions for the alkylation reaction of HY catalyzing toluene and tert-butanol: Cyclohexane 60 m L,catalyst 1.0g,n(tert-butanol):n(toluene)=3:1,the reaction temperature is 1890? and the reaction time is 4h.The conversion rate of toluene is 30.9% and the selectivity of 4-TBT is 71.0% under these conditions.2.Research on the reaction of HY catalyzing tert-butylation of toluene under different Silica-Alumina ratiosThe catalytic performance is researched in the reaction of HY catalyzing the alkylation of toluene and tert-butanol under the Silica-Alumina ratios 7.5,11,12 and 14.The experimental results show that: the order of catalytic activity of the 4 zeolite was HY(Si/AL=12)> HY(Si/AL=11)> HY(Si/AL=14)> HY(Si/AL=7.5),and the order of the total acid content is HY(Si/AL=7.5)> HY(Si/AL=7.5)> HY(Si/AL=7.5)> HY(Si/AL=14),which indicates that the catalytic activity of zeolite is the result of the comprehensive action of acid content,acid strength and acid type.The appropriate operating conditions for HY(Si/Al=12)catalyzing the alkylation of toluene and tert-butanol are listed as follows: cyclohexane 60 m L,HY(12)= 1.0g,n(tert-butanol):n(toluene)=3:1,the reaction temperature is 180? and the reaction time is 4h.The conversion rate of toluene is 40.7% and the selectivity of P-Tert-Butyl Toluene(PTBT)is 71.0% under these conditions.3.Research on the reaction of HY@MCM-41 nucleocapsid zeolite catalyzing the alkylation of toluene and tert-butanolCatalyst for HY@MCM-41 nucleocapsid zeolite is synthesized by the application of zeolite silica sources method,the reaction of the alkylation of toluene and tert-butanol is taken as the probe reaction to evaluate the catalytic activity of the catalyst for HY@MCM-41 nucleocapsid zeolite.The experimental results show that: according to the small-angle XRD,HY@MCM-41 composite zeolite have obvious characteristic peak and diffraction peak at the place of(100),(110)and(200),which indicates that the HY@MCM-41 zeolite has been prepared successfully.According to SEM,HY@MCM-41 zeolite present the loose micron-flakes and rough surface,which indicates that the surfaces of HY zeolite have wrapped the shell of McM-41 successfully.According to BET,the growth of MCM-41 does not destroy the micro-porous structures of HY zeolite.According to NH3-TPD,the weak acid content of HY@MCM-41 molecular sieve changed little,while the strong acid content decreased obviously.According to the analysis of PY-IR,the L acid content of HY@MCM-41 decreased significantly,while the B acid content decreased slightly;under the same conditions,both catalytic activity and para-position selectivity are significantly better than the catalyst for HY zeolite,which is because the outer surface of HY is wrapped with the mesoporous MCM-41 shell,realizing the modulation of the surface acidity of HY zeolite,passivation of the exterior acid center and inhibiting the occurrence of side reactions;the synthetic process conditions for HY@MCM-41 zeolite are researched,the appropriate process conditions of the reaction are listed as follows: NaOH concentration is 1mol/L,pH is 9.5,and crystallization time is 48h;the process conditions are researched for the reaction of HY@MCM-41 nucleocapsid zeolite catalyzing tert-butylation of toluene,the appropriate process conditions of the reaction are listed as follows: the dosage of molecular sieve is 1.0g,and the molar ratio of tert-butanol to toluene is 3,the reaction temperature is 180? and the reaction time is 4h,the conversion rate of toluene is 76.4% at most,and the selectivity of 4-TBT can be 90.4% at this moment.