磷改性ZSM-5分子筛的制备及其催化苯酚烷基化反应性能

Preparation of Phosphorus Modified ZSM-5 Zeolite and Its CatalyticPerformance for Phenol Alkylation

为了解决ZSM-5分子筛催化苯酚烷基化对甲酚选择性低的问题,采用等体积浸渍法对制备的ZSM-5分子筛进行硅、磷、镁改性得到系列改性ZSM-5催化剂。采用XRD、Py-IR和BET等手段对改性前后ZSM-5分子筛进行表征,并采用固定床反应器考察了改性ZSM-5分子筛催化苯酚烷基化反应性能。结果表明:磷负载质量分数15%的15P-ZSM-5分子筛的比表面积和总酸量分别从未改性前的395 m^(2)/g和406μmol/g降低到了309 m^(2)/g和128μmol/g,外表面酸量从未改性前的18μmol/g降低到了3μmol/g;在质量空速12 h^(-1)、反应温度420℃、反应压力1.5 MPa条件下进行催化苯酚烷基化反应,磷负载质量分数10%的10P-ZSM-5分子筛作用下的苯酚转化率为52.4%、对甲酚选择性为15.4%;磷改性可以通过磷酸根离子覆盖ZSM-5分子筛外表面的酸位点对表面酸性酸量进行调节,提高对甲酚的选择性,与其他改性分子筛相比,磷改性分子筛具有最佳的苯酚烷基化反应性能。

To solve the problem of low selectivity of cresol for phenol alkylation catalyzed by ZSM-5 zeolite,a series of modified ZSM-5 catalysts was obtained by modifying the ZSM-5 zeolite prepared by the equal-volume impregnation method with silicon,phosphorus and magnesium.The ZSM-5 zeolite before and after modification was characterized by XRD,Py-IR and BET methods.The catalytic performance of modified ZSM-5 zeolites for phenol alkylation was investigated in a fixed bed reactor.The results show that the specific surface area and total acid amount of P-loaded 15P-ZSM-5 zeolite with a mass fraction of 15%are decreased from 395 m^(2)/g and 406μmol/g to 309 m^(2)/g and 128μmol/g,respectively,and the external surface acid amount is decreased from 18μmol/g to 3μmol/g.The phenol alkylation reaction was catalyzed at the mass space velocity of 12 h^(-1),reaction temperature of 420℃and reaction pressure of 1.5 MPa.Under the catalysis of the P-loaded 10P-ZSM-5 zeolite with a mass fraction of 10%,the conversion rate of phenol and selectivity for cresol are 52.4%and 15.4%respectively.Phosphorous modification can adjust the surface acid amount of ZSM-5 zeolite by using phosphate anions to cover the acid sites on the external surface of ZSM-5 zeolite,and improve the selectivity for cresol.Compared with other modified zeolites,the phosphorous modified zeolite has the best performance in phenol alkylation reaction.