Modified Nano-hzsm-5 Zeolite Catalyst Ethylbenzene Ethylation Reaction Performance

Para-diethylbenzene(p-DEB) is a high-valued desorbent commonly used in p-xylene adsorptive separation process and the key raw material of vinylstyene, whereas its isomers, o-and m- DEB have lower market values. Now large-crystal HZSM-5 zeolites(2~5 m) are used as catalysts in the industrial production of p-DEB. After modifications, large-crystal HZSM-5 zeolite can get high p-DEB selectivity. But it's activity is low and it's stability is poor.The zeolite with crystal size less than 100nm and with unique physical and micro-porous characteristics could replace the existing zeolite catalyst and thus novel environmental friendly catalytic processes could be developed. Compared with the large-crystal HZSM-5 zeolites, nano HZSM-5 zeolites have three catalytic properties. One is high reaction activity, the other is good stability and the third is good resistance of coke. Based on the catalytic properties of nano HZSM-5 zeolites, it is hoped to get a new catalyst which has high reaction activity, good stability and high p-DEB selectivity for the industrial production of p-DEB.In this paper, different modification methods was studied. It is found that hydrothermal treatment, La2O3 modification, silylation, P modification and MgO modification all can adjust the strength and the quantity of acid sites and regulate pore size of zeolites. Hydrothermal treatment and La2O3 modification can only improve p-DEB selectivity slightly. Silylation, P modification and MgO modification can improve p-DEB selectivity greatly.After nano HZSM-5 zeolites are modified by combined methods, La-Mg-HZSM and La-Mg-Si-HZSM can be gained The p-DEB selectivity of La-Mg-Si-HZSM exceeds 98% and after reaction run for 300 hours, it's DEB yield can still reach 6.53%. Compare the catalytic performances of modified HZSM-5 zeolites with different crystal size, and follow points can be got:A. The reaction temperature of modified nano HZSM-5 is lower than that of modified micro HZSM-5 about 20 C and the mol ratio of EB and ethylene increases from 4.5 to 5.5;B. Under the same reaction conditions, the EB conversion of modified nano HZSM-5 exceeds that of modified micro HZSM-5 64%;C. After the reaction run for 300 hours under different reaction conditions, the DEB yield of modified nano HZSM-5 exceeds that of modified micro HZSM-5 13%.