ZSM-5/纳米β核壳分子筛的构筑与性能

Construction and properties of ZSM-5/nano-βcore-shell zeolites

采用DPA 206(阳离子淀粉)对ZSM-5进行表面预处理,并通过分段晶化合成壳层为纳米β分子筛的有序复合材料。得到的核壳分子筛,通过XRD、SEM、HR-TEM、N_(2)吸附-脱附和NH_(3)-TPD等进行表征。结果表明,硅源的种类会影响通过二次生长方式所得β分子筛的晶体形貌,以自制硅粉合成材料的壳层覆盖率接近100%,且利于形成均匀致密的纳米多晶壳层,核壳化优化了比表面积和孔容参数、酸中心的分布及其强度,形成了高分散的活性中心和丰富的多级传质孔道。在均三甲苯(1,3,5-TMB)裂解反应中,相比于非核壳组成分子筛,ZSM-5/纳米β核壳分子筛展现出更优异的催化活性、反应稳定性和协同催化效果,是用于大分子芳烃高效转化的理想催化材料。

Ordered zeolite-composites with nano-βshell were synthesized by segmented crystallization,after the core ZSM-5 was pretreated by the DPA 206(cationic starch).The obtained ZSM-5/nano-βcore-shell zeolites were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),high-resolution transmission electron microscopy(HR-TEM),N_(2) adsorption-desorption and temperature programmed desorption of ammonia(NH_(3)-TPD).The results show that,the silica source can affect the crystal morphology of zeolite-βobtained by secondary synthesis,the shell coverage is approximately 100%by using self-made silica powder,which is favorable for the formation of uniform and dense nano polycrystalline shell.The specific surface area,textural properties and the acid distribution of the core-shell material were optimized,hence with highly dispersed active centers and abundant of hierarchical porosity.Compared with the other catalysts in the cracking reaction of mesitylene(1,3,5-TMB),ZSM-5/nano-βCore-shell zeolite shows higher catalytic activity,more excellent reaction stability and synergistic effect,and thus it would be an ideal catalytic material for the efficient conversion of heavy aromatics.