P-Fe改性ZSM-5分子筛的酸性质对正戊烷催化裂解性能的影响

Effect of Acid Properties of P-Fe Modified ZSM-5 Zeolite on the Catalytic Pyrolysis Performance of n-Pentane

为提高石脑油中小分子烷烃催化裂解为低碳烯烃的收率,采用等体积浸渍法制备P-Fe改性ZSM-5分子筛。通过XRD、N_(2)等温吸附-脱附、NH_(3)-TPD和Py-IR等手段对分子筛的物化性质进行表征。采用固定床微型反应器,考察P-Fe改性ZSM-5分子筛对正戊烷催化裂解性能的影响,分析酸性质与催化裂解性能之间的关联规律。结果表明:P-Fe改性提高了ZSM-5分子筛水热处理后强酸酸量的保留率,负载P_(2)O_(5)能提高ZSM-5分子筛水热稳定性并提高弱酸酸量占比,负载Fe 2O_(3)增加了其Lewis酸比例;正戊烷的转化率随P-Fe改性ZSM-5分子筛的强酸酸量增加而提高,且转化率的增长速率随强酸酸量增加而减小,当强酸酸密度大于0.55μmol/m 2时,引起的氢转移反应明显增强;当弱酸所占比例增加时,丙烯选择性提高,乙烯选择性随Lewis酸比例增大而提高。

To improve the yield of catalytic pyrolysis of small molecular alkanes to light olefin in naphtha,P-Fe modified ZSM-5 zeolites were prepared by the equal volume impregnation method.Physicochemical properties of molecular sieves were characterized by XRD,N_(2) isothermal adsorption-desorption,NH_(3)-TPD and Py-IR.Meanwhile,a fixed bed micro reactor was used to investigate the effect of P-Fe modified ZSM-5 zeolites on catalytic pyrolysis properties of n-pentane,and then analyze the correlation between acid properties and catalytic pyrolysis performance.The results show that P-Fe modification can improve the retention rate of strong acid content of ZSM-5 zeolite after hydrothermal treatment,the loaded P_(2)O_(5) can improve the hydrothermal stability of ZSM-5 zeolite and the proportion of weak acid,and the loaded Fe 2O_(3) can improve Lewis acid ratio.The conversion rate of n-pentane is increased with the increase of strong acid amount of P-Fe modified ZSM-5 zeolites,and the growth of conversion rate is decreased with the increase of strong acid amount;when the strong acid density is greater than 0.55μmol/m 2,the hydrogen transfer reaction induced is obviously enhanced;when the proportion of the weak acid rises,the propylene selectivity is improved,and the ethylene selectivity rises with the increase of Lewis acid.