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在干凝胶法制备ZSM-5分子筛的体系中添加晶种导向剂,控制分子筛的生长,制备了纳米沸石组装的无粘结剂成型多级孔ZSM-5分子筛,一步完成纳米分子筛的制备及组装成型,即克服了传统纳米粒子难以过滤分离的问题,同时组装所形成的多级孔有助于改善分子在催化剂内的扩散,从而提高催化反应效率.以硅胶、薄水铝石为原料,四丙基氢氧化铵(TPAOH)和ZSM-5晶种导向胶作为粘结剂,通过混捏、挤条得到直径2mm的条状前驱物,随后通过干凝胶转换法制备成型分子筛.所用晶种导向剂组成为0.35TPAOH:1SiO2:20H2O:4C2H5OH.通过X射线衍射(XRD),热重(TG)分析和傅里叶变换红外(FTIR)光谱等方法对分子筛晶化过程进行了表征,结果表明晶种导向剂加入量对分子筛生长速度及多级孔结构均有影响.当所加晶种导向剂中TPAOH与SiO2的摩尔比为0.025时,经过3h晶化,分子筛相对结晶度达到100%.扫描电镜(SEM)结果表明,合成的分子筛尺寸约为200nm,组装形成的多级孔分子筛的介孔体积为0.28cm3·g-1.通过NH3程序升温脱附(NH3-TPD)考察了所得成型分子筛的酸性,发现该分子筛酸性与市售的粉末H-ZSM-5分子筛类似.
The ZSM-5 molecular sieve prepared by dry gel method is added with a seed guiding agent to control the growth of the molecular sieve to prepare a zeolite-free binder-forming multi-stage pore ZSM-5 zeolite, and the preparation of the nanometer molecular sieve in one step is completed Assembly and forming, that overcomes the traditional nano-particles difficult to filter separation problem, while the assembly of the multi-level hole formed help to improve the diffusion of molecules in the catalyst, thereby enhancing the catalytic reaction efficiency.With silica gel, boehmite as raw material, Tetrapropylammonium hydroxide (TPAOH) and ZSM-5 seeding glue were used as binders to prepare strip-shaped precursors with a diameter of 2 mm by kneading and extruding, and then the formed molecular sieves were prepared by xerogel conversion method. The composition of the directing agent is 0.35TPAOH: 1SiO2: 20H2O: 4C2H5OH.The crystallization process of the molecular sieve was characterized by X-ray diffraction (XRD), thermogravimetric analysis (TG) and Fourier transform infrared spectroscopy (FTIR) When the molar ratio of TPAOH to SiO2 in the seed-oriented agent is 0.025, the relative crystallinity of the molecular sieve reaches 100% after 3h crystallization. Electron microscopy (SEM The results showed that the size of synthesized zeolite was about 200 nm, the mesopore volume of the assembled multi-pore molecular sieve was 0.28cm3 · g-1. The NH3-TPD was used to investigate the acidity, The molecular sieve was found to be similar in acidity to the commercially available powder H-ZSM-5 molecular sieve.