化学学报 ›› 2013, Vol. 71 ›› Issue (04): 573-578.DOI: 10.6023/A12121032 上一篇    下一篇

研究论文

离子热法合成AEL磷酸铝分子筛膜及其机理研究

李科达a,c, 厉晓蕾a,c, 王亚松a,c, 李大伟a,c, 刘浩a,c, 徐仁顺a,b, 田志坚a,b   

  1. a 中国科学院大连化学物理研究所洁净能源国家实验室 大连 116023;
    b 中国科学院大连化学物理研究所催化基础国家重点实验室 大连 116023;
    c 中国科学院大学 北京 100049
  • 收稿日期:2012-12-11 出版日期:2013-04-14 发布日期:2013-02-04
  • 通讯作者: 田志坚 E-mail:tianz@dicp.ac.cn
  • 基金资助:

    项目受国家自然科学基金(No. 21103179)资助.

Ionothermal Synthesis of AEL-Type Aluminophosphate Molecular Sieve Membrane and Its Formation Mechanism

Li Kedaa,c, Li Xiaoleia,c, Wang Yasonga,c, Li Daweia,c, Liu Haoa,c, Xu Renshuna,b, Tian Zhijiana,b   

  1. a Dalian National Laboratory of Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning;
    b State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning;
    c University of Chinese Academy of Sciences, Beijing 100049
  • Received:2012-12-11 Online:2013-04-14 Published:2013-02-04
  • Supported by:

    Project supported by the National Natural Science Foundation of China (No. 21103179).

δ-氧化铝为基底和铝源, 使用离子热基底自转晶法, 在[EMIm]Br离子液体中合成了AEL磷酸铝分子筛膜. 采用X射线(XRD)和扫描电镜(SEM)等方法对所得的AEL分子筛膜进行了表征, 研究了合成条件对膜的影响. 研究发现在氢氟酸和磷酸离子液体混合溶液中一步反应可以合成c轴高度取向的AEL分子筛膜, 在氢氟酸和磷酸离子液体溶液中分别顺序两步反应可以合成无取向的AEL分子筛膜. 离子热基底自转晶法分子筛膜的形成符合固相转化机理, 氟离子可以促进分子筛膜的生长, 并影响分子筛膜的取向.

关键词: 离子热, 磷酸铝分子筛膜, 基底自转晶, 晶化机理

Highly c-oriented AEL aluminophosphate molecular sieve membranes were ionothermally synthesized on the surface of δ-alumina substrate by “Substrate Surface Conversion” method. The typical synthesis procedure can be described as follows: a δ-aluminia alumina disc was put into 1-ethyl-3-methyl imidazolium bromide ([EMIm]Br) solution containing reagent quantities of phosphoric acid (H3PO4) (85 wt% in water, AR) and hydrofluoric acid (HF) (40 wt% in water, AR). The synthesis was performed at 210 ℃ for certain time. No additional Al source is added into the synthesis solution. After the synthesis, the as-synthesized sample was washed thoroughly with distilled water and acetone for several times by ultrasonic vibration and dried at 120 ℃ overnight. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were carried out to characterize the products. The synthesis process of AEL membrane via “Substrate Surface Conversion” can be divided into two separated steps, which is carried out in the ionic liquid solution of HF and H3PO4 in turn. We termed this route as ionothermal two-step method, which making it possible for us to investigate the effect of HF and H3PO4, respectively. The formation mechanism of “Substrate Surface Conversion” was therefore demonstrated, with which the δ-alumina substrate acts as both support and Al source during the synthesis process. The surface of the substrate is first converted into a gel layer by the solution. The layer is a heterogeneous phase, which contains all nutrients required for the crystallization of molecular sieve membrane, including the aluminophosphate precursor, the mineralizer and the structure directing agent. The transformation from the gel layer into membrane is probably of solid-solid formation mechanism. The whole synthesis process needs the participation of both H3PO4 and HF. H3PO4 is an essential component of both aluminophosphate precursor and molecular sieve crystal. The crystallinity and the orientation of synthesized membranes can be greatly influenced by adjusting the amount of HF in the initial solution, which may act as both structure directing agent and mineralizer during the synthesis process of molecular sieve membrane.

Key words: ionothermal synthesis, aluminophosphate molecular sieve membrane, substrate surface conversion, formation mechanism