›› 2020, Vol. 22 ›› Issue (4): 46-55.

• Catalyst Research • 上一篇    下一篇

通过晶种胶作导向剂的凝胶预陈化路线合成多级孔道FAU/α-Al2O3整体材料

王佳1,靳其兵2,赵天波3   

  1. 1. 北京化工大学
    2. 北京化工大学信息科学与技术学院
    3. 北京理工大学化学学院教育部簇科学重点实验室
  • 收稿日期:2019-11-12 修回日期:2020-03-17 出版日期:2020-12-30 发布日期:2020-12-30
  • 通讯作者: 靳其兵 E-mail:jinqb@mail.buct.edu.cn
  • 作者简介:2020-03-31
  • 基金资助:
    国家自然科学基金;国家自然科学基金;中央高校基本科研业务费专项基金资助

Fabrication of Hierarchically Porous FAU/α-Al2O3 Monoliths via Gel Pre-aging Routes Using Seed Gel as Directing Agent

Wang Jia1,bing QiJin 3   

  • Received:2019-11-12 Revised:2020-03-17 Online:2020-12-30 Published:2020-12-30
  • Contact: bing QiJin E-mail:jinqb@mail.buct.edu.cn
  • Supported by:
    National Natural Science Foundation of China; National Natural Science Foundation of China;Fundamental Research Funds for the Central Universities of China

摘要:

以整体型α-Al2O3为载体,晶种胶作导向剂,通过凝胶预陈化路线合成了多级孔道FAU整体材料。对合成的样品进行了FT-IR、XRD、SEM和N2吸附脱附表征。根据实验结果确定了晶种胶、凝胶预处理及预陈化步骤的作用,同时提出了不同路线生成氧化铝复合物可能的合成机理。结果发现:负载的FAU沸石的粒径、形状及数量可通过改变晶化凝胶的组成,并且α-Al2O3载体的结构没有明显改变。具有简单、可重现且易将三重孔道结构融于成型的整体材料中的特点,通过晶种胶预处理的凝胶预陈化路线可加强载体内表面与沸石间的界面作用,形成纯相FAU晶体沉积在α-Al2O3载体骨架表面的形貌。另外,该方法可为其他的多级孔道沸石的合成提供思路。                           
 

关键词: FAU/α-Al2O3整体材料, 多级孔道, 晶种胶, 预陈化, 凝胶预处理

Abstract: Hierarchically macro-/meso-/microporous supported FAU monoliths with different micro-morphologies were synthesized using monolithic α-Al2O3 with interconnected macro-mesopores as blank carriers via gel pre-aging routes using seed gel as directing agent. Prior to the hydrothermal treatment, α-Al2O3 monoliths were subject to pre-aging in the crystallization gel at ambient temperature for 24 h, subsequently, in situ crystallization (ISC) was conducted at 373 K for 5 h. The FAU coatings in the size range of several-hundred nanometers were distributed on the wall of the macropores or precipitated as aggregates in the macro-channels of the substrates by conducting the gel pre-treating step before the pre-aging step or not. The as-synthesized samples were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and N2 sorption techniques. It was found that the pure-phase FAU could be supported on the alumina substrate with the presence of seed gel in the synthesis system via gel pre-aging routes, whereas the phase transition of alumina could be inhibited by pre-treating α-Al2O3 substrate with seed gel. Involving the gel pre-aging routes with the first-step of seed gel pre-treatment, the crystal size, shape and loading of the supported FAU could be readily tuned by varying the crystallization gel molar ratios of Na2O/Al2O3 or SiO2/Al2O3, the addition of seed gel into the crystallization mixture, the extra pre-treating step or the position of the mixture of substrate and crystallization gel in the reactor without notably changing the structure of the α-Al2O3 support. The effects of seed gel, gel pre-treating and pre-aging step were determined, while the possible formation mechanism of alumina composites with different synthesis processes was discussed based on the experimental results. With the characteristic of simple, reproducible and practically easy to integrate treble porous structures into large-dimension monoliths, the gel pre-aging route coupled with the one step pre-treatment of seed gel proved to be very effective in affording pure FAU crystals deposited on the α-Al2O3 skeleton surface and strengthening the interfacial interaction between them. Moreover, the successful preparation of FAU/α-Al2O3 composites via gel pre-aging route with two-step of gel pre-treatments and crystallized in the form of steam-assisted conversion (SAC) suggested that a more environment-friendly and cost-effective crystallization mode could be developed with the above optimal route and might provide inspiration to the synthesis of other hierarchical zeolites.

Key words: FAU/α-Al2O3 monoliths, Hierarchical porosity, seed gel, pre-aging, gel pre-treatment