物理化学学报 >> 2012, Vol. 28 >> Issue (09): 2115-2121.doi: 10.3866/PKU.WHXB201206141

催化和表面科学 上一篇    下一篇

晶种导向干凝胶法制备成型ZSM-5分子筛

岳明波1,2, 杨娜2, 王一萌2   

  1. 1. 曲阜师范大学化学与化工学院, 山东省生命有机分析重点实验室, 山东曲阜 273165;
    2. 华东师范大学化学系, 上海市绿色化学与化工过程绿色化重点实验室, 上海 200062
  • 收稿日期:2012-03-30 修回日期:2012-06-14 发布日期:2012-08-02
  • 通讯作者: 王一萌 E-mail:ymwang@chem.ecnu.edu.cn
  • 基金资助:

    国家自然科学基金(20890124, 21003083)和山东省博士科研奖励基金(BS2009CL031)资助项目

Synthesis of Shaped ZSM-5 Zeolites by Dry-Gel Conversion with Seed Gel as Directing Agent

YUE Ming-Bo1,2, YANG Na2, WANG Yi-Meng2   

  1. 1. Key Laboratory of Life-Organic Analysis of Shandong Province, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, Shandong Province, P. R. China;
    2. Shanghai Key Laboratory of Green Chemistry and Chemical Processes, Department of Chemistry, East China Normal University, Shanghai 200062, P. R. China
  • Received:2012-03-30 Revised:2012-06-14 Published:2012-08-02
  • Contact: WANG Yi-Meng E-mail:ymwang@chem.ecnu.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (20890124, 21003083) and Doctoral Foundation of Shandong Province, China (BS2009CL031).

摘要:

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2 mm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3 h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200 nm, 组装形成的多级孔分子筛的介孔体积为0.28 cm3·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.

关键词: 成型ZSM-5分子筛, 干凝胶法, 多级孔结构, 晶种导向剂, 纳米分子筛

Abstract:

Shaped binderless ZSM-5 zeolites were prepared via a rapid dry-gel conversion technique from aluminosilicate extrudate. Silica gel and boehmite were well mixed and extruded into cylindrical shaped extrudates with diameter of 2 mm with the aid of silica sol, ZSM-5 zeolite seed gel, and/or tetrapropylammonium hydroxide (TPAOH) solution. The total molar ratio of TPAOH to SiO2 was fixed at 0.025. With same amounts of structure directing agent (TPAOH), the addition of seed gels accelerated the crystallization of the zeolite. The seed gel directing agent composition was 0.35TPAOH:1SiO2:20H2O: 4C2H5OH. The seed gel not only provided crystal nuclei for rapid crystallization but also controlled the size of the ZSM-5 crystals. Especially, the morphology of these extrudates was well maintained in the crystallization process. The crystallization processes of zeolite were characterized by X-ray diffraction (XRD), thermogravimetric (TG) analysis, and Fourier transform infrared (FTIR) spectroscopy. The results showed that the growth of the zeolite was accompanied by the occupation of the zeolite channels by TPAOH. When the TPAOH/SiO2 molar ratio was 0.025, the sample achieved 100% relative crystallinity after 3 h crystallization. The morphology and textural properties were characterized by scanning electron microscopy (SEM) and nitrogen sorption isotherms. The obtained shaped zeolites comprised nanosized crystals (200 nm) and exhibited a hierarchical structure with high mesopore volume (0.28 cm3·g-1). The temperature- programmed desorption of ammonia (NH3-TPD) was used to assess the acidity of these shaped zeolites. The results showed that this shaped zeolite possessed an acidity similar to that of a commercial H-ZSM-5 catalyst.

Key words: Shaped ZSM-5 zeolite, Dry-gel conversion, Hierarchical structure, Seed structure directing gel, Nanoscale zeolite

MSC2000: 

  • O643.36