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ZSM-5分子筛对许多正碳离于反应有优异的择形催化性能。近年来的研究表明,ZSM-5沸石的晶粒大小对其催化活性、选择性和稳定性有显著影响。如对甲苯歧化、甲苯与甲醇的甲基化反应,大晶粒ZSM-5分子筛对生成对二甲苯有较高的选择性。对于二甲笨液相异构化反应,小晶粒ZSM-5沸石具有较高的催化活性和选择性。我们用“直接法”合成了大晶粒(34×116μ)ZSM-5沸石分子筛,比较了不同晶粒大小ZSM-5分子筛催化剂在一些反应中的催化性能。大晶粒ZSM-5分子筛系不用有机胺,直接用水玻璃、硫酸铝、硫酸为原料合成的。用光学显微镜、扫描电镜观察所得分子筛的晶粒外形和大小,取5—6个有代表性的晶粒计算其平均尺寸。用BET重量法测定分子筛对正己烷、环己烷和水的吸附量。用X—射线衍射分析样品的物相。在160—200℃温度范围内考察了晶化温度对晶粒大小的影响,所得结果如表1。
ZSM-5 zeolite has excellent shape selectivity for many ortho-carbon dissociative reactions. Recent studies have shown that the grain size of ZSM-5 zeolite has a significant impact on its catalytic activity, selectivity and stability. Such as toluene disproportionation, toluene and methanol methylation reaction, large grain ZSM-5 zeolite to generate p-xylene higher selectivity. For the dimethyl isophthalide phase isomerization reaction, the small crystal ZSM-5 zeolite has high catalytic activity and selectivity. We synthesized the large-grained (34 × 116μ) ZSM-5 zeolite by the “direct method” and compared the catalytic performance of ZSM-5 zeolite catalysts with different grain sizes in some reactions. Large grain ZSM-5 zeolite without organic amine, direct use of water glass, aluminum sulfate, sulfuric acid as raw materials. The morphology and size of the obtained molecular sieve were observed with an optical microscope and a scanning electron microscope, and the average size of 5-6 representative grains was calculated. The adsorption capacity of molecular sieve to n-hexane, cyclohexane and water was determined by BET gravimetric method. The phase of the sample was analyzed by X-ray diffraction. The effect of crystallization temperature on the grain size was investigated in the temperature range of 160-200 ℃.