MWW族分子筛的合成工艺及性质研究进展

综述了MWW族分子筛合成工艺及对烃的吸附性质、表面酸性和稳定性研究进展。采用汽相和水热合成法均可以合成MWW族分子筛,但水热合成法更常用,并且水热法可分为动态合成和静态合成两种,影响其合成产物结构的主要因素均为模板剂的种类及用量、温度、硅铝比、胶液碱度等。重点讨论了水热合成法中模板剂、硅铝比、合成体系碱度和晶化方式对分子筛合成结构的影响,同时介绍了含杂原子MWW族分子筛的合成进展。深入评述了MWW族分子筛对正己烷、3-甲基戊烷、2,2-二甲基丁烷、苯、甲苯、p-二甲苯和m-二甲苯等烃类分子吸附性质的研究进展,并对MWW族分子筛的孔道结构进行了讨论,指出有大分子参与的反应主要发生在位于表面的12MR超笼中,只有小分子才能进入10MR孔道;以吡啶、2,6-二叔丁基吡啶、NH3、CO、N2等作为探针分子,对MWW分子筛酸性进行测定并区分了外表面和孔道内酸,同时也讨论了量子化学计算MWW族分子筛酸性的研究进展;介绍了MWW族分子筛的耐热稳定性和酸碱稳定性。指出MWW族分子筛的研究和开发为更大孔道分子筛的研究开辟了道路。

Advances in the Research on Synthesis and Properties of MWW Zeolite

This article describes the advances in the research on the synthesis of MWW zeolite and the zeolite＇s absorbability to hydrocarbon,surface acidity and stability.Both the vapor and hydrothermal synthesis methods can be used to synthesize MWW zeolite although the hydrothermal method is more commonly used. The hydrothermal synthesis method consists of dynamic synthesis and static synthesis.The main factors affecting the structures of the products of the two hydrothermal methods are the category and dose of template, temperature,the ratio of silicate to aluminum and the alkalinity of glue solution.This article discusses,in detail,the influence of template ,the silicate-aluminum ratio ,alkalinity of the synthetic system and the way of crystallization on the structure of zeolite synthesized in the hydrothermal synthesis method and also describes the advances in the research on the synthesis of MWW zeolite with heteroatom.The article also describes the advances in the research on the Adsorption properties of MWW zeolite to hydrocarbon molecules such as n- hexane, 3 -methylpentane, 2,2 -dimethylbutane, benzene, methylbenzene, p -dimethylbenzene and m -dimethylbenzene and discusses the pore structure of MWW zeolite.According to the article ,most reactions involving large molecules take place in the 12MR supercage at the surface and only small molecules can enter the 10MR pores.Using pyridine,2,6-di-tert-butylpyridine,NH3,CO and N2 as molecular probes,the authors of the article measured the acidity of MWW zeolite and discriminated the acid at the outside surface and in the pores.In the article,they also discussed the advances in the research into using quantum chemistry to calculate the acidity of MWW zeolite.Also described in the article is MWW zeolite＇s stability to heat,acid and alkali.The article commented that the research and development of MWW zeolite has laid the groundwork for the development of zeolite with larger pores.