【作者】 顾文应；

【导师】 郭洪臣；

【作者基本信息】 大连理工大学 ， 能源化工， 2010， 硕士

【摘要】 ZSM-5沸石具有独特孔道结构,良好的骨架热稳定性和水热稳定性、较强的酸度、以及优异的择形催化性能,被大量地应用于催化裂化、芳烃烷基化、甲醇制汽油和轻烃芳构化等重要工业过程。自1972年美国Mobil公司首次使用TPA+为模板剂合成出ZSM-5沸石以来,许多有机胺模板剂和氨水以及多种低碳醇导向合成ZSM-5沸石,甚至能在无胺(氨)无醇的所谓无模板凝胶体系中晶化出ZSM-5沸石。采用无模板方法合成ZSM-5沸石既可以进一步降低生产成本又可以最大限度地减少胺(氨)类对环境的污染。本文主要报道了我们最近在无模板凝胶体系中水热合成ZSM-5沸石的初步研究结果：(1)在无模板剂体系中,不添加晶种很难得到ZSM-5沸石,晶种过多则易产生杂晶。Na2O／SiO2限制了凝胶体系的碱度,且Na+具有模板作用帮助构建骨架,故较低和较高的Na2O／SiO2都不利于ZSM-5沸石的合成。廉价的水玻璃和硅溶胶都可合成高结晶度的ZSM-5沸石,并且不同硅源对ZSM-5沸石晶貌有一定的影响；吐温-20的添加,能显著优化凝胶状态,同时提高产物结晶度,合成特殊晶貌的ZSM-5沸石。(2)高硅ZSM-5沸石难以合成,因为随着凝胶SiO2／Al2O3比升高,硅越难进入骨架,无模板剂合成中Na+弱的导向作用使得这种现象更加明显。由于生成的ZSM-5沸石在母液中的稳定性较差,所以合成过程中需严格控制晶化温度和晶化时间而避免产生杂晶。采用搅拌晶化也能明显地减小ZSM-5沸石的晶粒度,同时影响晶体形貌。(3)通过对凝胶SiO2／Al2O3比范围在20～300样品进行物化性能表征表明,无模板剂合成的ZSM-5分子筛孔道通畅,热稳定性,水热稳定性良好,酸性较高,在正己烷裂化反应中表现出良好的催化性能。无模板剂ZSM-5沸石造价较低,环境友好,将具有广阔的应用前景。更多还原

【Abstract】 ZSM-5 zeolite has been widely applied to catalytic cracking, aromatic hydrocarbon alkylate, methyl alcohol system gasoline and the light hydrocarbon aromatization and such like various industry, due its unique miropore structure, the well skeleton thermostability and water thermostability, relative strong acidity as well as outstanding shape-selecting catalytic performance. Since Mobil Corporation first synthesized the ZSM-5 zeolite using TPA+as template in 1972, organic amines and ammonia as well as the many kinds of low-carbon alcohol have been used as structure-directing reagents towards to ZSM-5 zeolite. Moreover, ZSM-5 zeolite even can be crystallized without the template of amine (ammonia) and alcohol.Template-free methods towards to ZSM-5 zeolite can not only reduce the production cost but also reduce environment pollution of the volatile amines (ammonia). So, this paper mainly discussed the synthesis of ZSM-5 zeolite by template-free hydrothermal method.(1) In the template-free system, it is very difficult to obtain the ZSM-5 without seeds, but there will be a new mixed crystal formed with excessive seeds. Not only the ratio of Na2O/SiO2 decides the alkalinity of the gelatin, but also Na+cation plays a structure directing role, so it is an important factor. Therefore it is not propitious for synthesis ZSM-5 with too low or too high ratio of Na2O/SiO2. Highly pure ZSM-5 can be synthesized with inexpensive silicon resource such as water glass and the silicon sol, and its appearance is influenced by the different silicon source; Adding Tween-20 can obviously optimize the gel state, simultaneously enhances the crystallinity, and synthesis ZSM-5 with special appearance.(2) ZSM-5 with high silicon is difficult to prepare, because of along with the rise of SiO2/Al2O3, the silicon is more difficult to enter the skeleton, and the weak guidance of Na+ causes this kind of phenomenon to be more obvious in the template free system. Mordenite will be easily formed if the SiO2/Al2O3 quite is low and kenyaite if the SiO2/Al2O3 quite is high. Crystallization temperature and time should be strictly controlled, otherwise mixed crystal forms. We can see that agitation can obviously reduce the size of ZSM-5.(3) Characterizations carried out with SiO2/Al2O3 range of 30 to 300 samples indicate that template-free ZSM-5 possess higher thermal and hydrothermal stability, good micropore diffusivity, and stronger acidity, as well as displays a good catalyzed performance in the n-hexane cracking reaction. Because of the low cost and environment friendly, the template-free ZSM-5 means a promising prospect of industrial application.更多还原