短b轴ZSM-5分子筛制备方法及应用研究进展

Progress in preparation and application of short b-axis ZSM-5 molecular sieve

ZSM-5分子筛作为应用最为广泛的催化剂之一,一直是研究关注的重点。由于其沿着b轴直通孔道相比于沿着a轴和c轴的Z形孔道具有更好的扩散性能,其长度的控制对改善分子筛的催化特性具有重要作用。综述了控制ZSM-5分子筛各向生长的主要方法,结构导向法和生长修饰法。对短b轴ZSM-5分子筛在MTP、MTH以及MTG等催化领域的应用进行了具体分析。并指出,特定季铵盐作为结构导向剂制备的片层分子筛,具有均匀良好的自柱撑结构和晶间介孔,由于结构导向剂制备难度较高,采用生长修饰剂部分取代季铵盐更加经济环保。特定生长修饰剂合成难度低且成本低廉,制备的分子筛具有分散或团聚片层结构,新工艺的开发以改善晶间介孔将使其具有更好的扩散性。对片层分子筛厚度和酸性的精准调控、合成机理以及各向长度对催化性能影响的深入研究,以保证高效制备兼顾转化率、选择性以及稳定性的分子筛对短b轴分子筛的发展具有重要意义。

As one of the most widely used catalysts,the ZSM-5 molecular sieve has always been the focus of scholars’research.Due to its better diffusion performance along the b-axis straight channels compared to that along the a-axis and c-axis the zigzag channels,the control of their length plays an important role in improving the catalytic properties of molecular sieves.The main methods for controlling the anisotropic growth of ZSM-5 molecular sieves are reviewed,including structure-oriented methods and growth modification methods.The application of short b-axis ZSM-5 molecular sieves in catalytic fields such as MTP,MTH,and MTG is analyzed in detail.It is also pointed out that lamellar molecular sieves prepared with specific quaternary ammonium salts as structural directing agents have a uniform and good self-pillared structure and intercrystalline mesopores.Due to the high difficulty in preparing structural directing agents,it is more economical and environmentally friendly to partially replace quaternary ammonium salts with growth modifiers.The synthesis of specific growth modifiers is low in difficulty and cost,and the prepared molecular sieves have dispersed or agglomerated lamellar structures.The development of new processes to improve intercrystalline mesopores will enable them to have better diffusivity.The in-depth study of the precise regulation of the thickness and acidity of lamellar molecular sieves,the synthesis mechanism,and the influence of anisotropic length on catalytic performance to ensure efficient preparation of molecular sieves that take into account conversion,selectivity,and stability is of great significance to the development of short b-axis molecular sieves.