晶种溶液辅助合成ZSM-5沸石及偏三甲苯异构化催化性能研究

Seed Solution-Assisted Synthesis of ZSM-5 Zeolite and Its Catalytic Performance of Trimethylbenzene Isomerization

以四丙基氢氧化铵为模板剂,商业硅溶胶为硅源,在100℃下合成了晶种溶液。同时,在无模板剂体系下,以晶种溶液辅助成功合成了结晶度良好的ZSM-5沸石,并探究了其合成条件。采用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、N_(2)吸附-脱附、傅里叶变换红外光谱(FT-IR)、X射线荧光光谱(XRF)和氨气程序升温脱附(NH_(3)-TPD)测试方法对合成的沸石样品进行表征。结果表明:在无模板剂存在下,仅添加0.5%(质量分数)晶种溶液即可合成ZSM-5沸石;同时,在最佳合成条件下,170℃晶化8 h可合成亚微米级ZSM-5沸石团聚体,粒径为500 nm左右。此外,在偏三甲苯异构化反应中,硅铝比为30的样品具有更好的催化性能,其偏三甲苯质量转化率、均三甲苯质量收率及均三甲苯选择性分别为32.81%、20.81%和63.42%。

The seed solution was synthesized at 100℃using tetrapropylammonium hydroxide as template and commercial silica sol as silicon source.Meanwhile,ZSM-5 zeolites with well crystallinity were successfully synthesized by adding seed solution in the template-free system,and the synthetic conditions of ZSM-5 zeolites were explored.The synthesized zeolites samples were characterized by X-ray powder diffraction(XRD),scanning-electron microscopy(SEM),N 2 adsorption-desorption,fourier transform infrared(FT-IR),X-ray fluorescence spectroscopy(XRF)and ammonium temperature-programmed desorption(NH 3-TPD).The results show that ZSM-5 zeolites are synthesized by adding only 0.5%(mass fraction)seed solution in the template-free system.Meanwhile,submicron-scale ZSM-5 zeolite aggregates with the size of~500 nm are synthesized at 170℃for 8 h under optimal synthesis conditions.Furthermore,in the isomerization of trimethylbenzene,the sample with n(SiO 2)/n(Al 2O 3)ratio of 30 has better catalytic performance.Mass conversion of 1,2,4-trimethylbenzene,mass yield of 1,3,5-trimethylbenzene and selectivity of 1,3,5-trimethylbenzene are 32.81%,20.81%and 63.42%,respectively.