晶种和季铵盐诱导β沸石合成研究

Hydrothermal synthesis of zeolite Beta by seeding and using quaternaryammonium salts

通过对比实验和X-射线衍射技术,研究了四乙基溴化铵(TEABr)和四乙基氢氧化铵(TEAOH)模板剂对β沸石晶体生长的结构导向作用,考察了合成胶硅铝比[n(SiO2)∶n(Al2O3)]和晶化条件对合成沸石相组成的影响。结果表明,以TEAOH为模板剂,在β沸石晶种质量分数0.5%、合成胶n(SiO2)∶n(Al2O3)=37.2~64条件下,合成出相对结晶度较高的纯β沸石。另一方面,以TEABr为模板剂,在晶种质量分数0.5%、晶化温度413K条件下,当n(SiO2)∶n(Al2O3)≤45、晶化时间240~260h时,可以获得结晶度高的单一β沸石;在不含晶种、n(SiO2)∶n(Al2O3)=37.2~72的体系中,合成的沸石β与沸石ZSM-5共生,而且随着硅铝比的增加沸石β质量分数逐渐减少,竞争相ZSM-5的含量急剧增加。

Taking into account of the issues during zeolite Beta production,the comparative experiments to examine the structure-direction effects of TEABr and TEAOH on Beta crystal growth were performed by the hydrothermal synthesis and XRD characterization,while the silica-to-alumina ratios and crystallization conditions were investigated in the present work.The results showed that,by the use of TEAOH as a template,the well relatively crystalline zeolites with BEA structure were synthesized under the conditions of SiO2/Al2O3 from 37.2to 64 and addition of 0.5wt% seed crystals in synthetic gels.On the other hand,in the case of TEABr as template and the introduction of 0.5wt%seed crystals,the highly crystalline zeolites with BEA structure were obtained under conditions of the silica-to-alumina ratios lower than 45 and crystallization periods in the range of 240~260h.In the case of using TEABr but no seed crystals,as the silica-to-alumina ratio ranged from 37.2to 72,the intergrowth phases of both Beta and ZSM-5zeolites were identified,and the BEA phase reduced with the increased ZSM-5as a competing phase.