甲烷无氧芳构化反应催化剂HZSM-5载体的研究

【作者】 张贺；

【导师】 王祥生；

【作者基本信息】 大连理工大学 ， 工业催化， 2002， 硕士

【摘要】 甲烷无氧芳构化反应对能源利用和催化科学均具有重要意义。自报道了973K下甲烷在Mo／HZSM-5催化剂上连续流动模式下的无氧芳构化反应以来，引起了国内外学术界的广泛关注。研究人员在Mo／HZSM-5系催化剂上做了大量的理论研究。研究表明HZSM-5是甲烷无氧芳构化反应的优良载体，HZSM-5以其独特的孔道结构和酸性质成为许多石油化工反应的优良催化剂，并且在甲烷无氧芳构化反应中对甲烷活化及生成苯的过程均起到重要作用。因此研究HZSM-5载体性质对甲烷无氧芳构化反应的影响是十分有意义的。 在此基础上，论文重点研究了载体HZSM-5性质对甲烷无氧芳构化反应的影响，包括不同硅铝比HZSM-5、不同结晶度HZSM-5、不同晶粒大小HZSM-5对甲烷无氧芳构化反应的影响。研究表明，在一定硅铝比范围内，随着硅铝比的降低，HZSM-5酸量增加，其催化反应活性增大，载体HZSM-5在该反应中起到酸催化作用。载体HZSM-5的结晶度对甲烷芳构化反应性能影响不大。同一体系下合成的不同晶粒大小的HZSM-5，其催化剂的催化活性与HZSM-5的酸性成正比，进一步证实了载体HZSM-5在该反应中起到酸催化作用，对于酸性相近的HZSM-5，其粒度越小，催化性能越好。 本文探讨了通过硅源的改变、晶化条件的控制合成不同晶粒大小的ZSM-5沸石的方法，研究了不同体系下合成微米ZSM-5和纳米ZSM-5的方法。所合成的微米级ZSM-5为一种孪晶，纳米级ZSM-5为纳米ZSM-5的团聚体，研究表明，以纳米级ZSM-5团聚体为载体的催化剂，其甲烷芳构化反应性能优于以微米级ZSM-5孪晶为载体的催化剂。本文还研究了高温水热法催化剂的甲烷无氧芳构化反应性能，探讨了该催化剂无芳构化活性的原因，可能是由于HZSM-5骨架铝的部分脱除及催化剂还原性能不利于甲烷芳构化活性Mo物种的生成。另外本文还考察了浸渍法基础上的挤条成型催化剂的甲烷无氧芳构化反应性能，并证实该催化剂具有一定的工业化前景。更多还原

【Abstract】 Methane non-oxidative aromatization is very significant to utilization of resources and science of catalysis. Mo/HZSM-5 catalyst has a very good catalytic performance in methane non-oxidative aromatization. HZSM-5 has particular pore structure and acidity, and it is proved to be a very good support. The effect of support properties on catalytic performance of Mo/HZSM-5 in methane non-oxidative aromatization is studied in this paper. Catalytic performance of 6%Mo/HZSM-5 catalysts with different SiO2/Al2O3 ratios is investigated. It is found that, the lower SiO2/Al2O3 ratio is, the stronger the acidity of HZSM-5 is, and the higher the conversion rate of methane is. In addition, catalytic performance of 6% Mo/HZSM-5 with the same SiO2/Al2O3 ratio but different crystallinity is tested. The results show that crystallinity does not significantly affect the catalytic performance. Therefore, the catalytic performance of Mo/HZSM-5 for methane non-oxidative aromatization doesn’t mainly depend on crystallinity, but acidity of support. Catalytic performance of 6% Mo/HZSM-5 with different crystal size is investigated. It is proved that , there is a close correlation between the activity of reaction and the acidity of HZSM-5. Catalytic performance of 6% Mo/HZSM-5 with the close acidity of HZSM-5 but different crystal sizes is also tested. It is found that, the smaller the crystal size is, the higher the activity of reaction is. Based on the above, it is suggested that HZSM-5 is not only the support of catalyst, but also plays an acid catalytic role. The influence of nanosizd HZSM-5 and microsized HZSM-5 zeolites on catalytic performance of Mo/HZSM-5 in methane non-oxidative aromatization is studied. Nanosize HZSM-5 loaded with Mo has much better catalytic performance than microsize HZSM-5 loaded with Mo. It is found that, nanosize HZSM-5 is nano-particla agglomeration, and microsized HZSM-5 is a kind of twins crystals. Catalytic performance of Mo/HZSM-5 prepared by high-temperature hydrothermal method is also studied. No activity of the reaction results from the extraction of framework aluminum and the decrease of its reductive ability.更多还原