修饰晶种法合成MFI型分子筛膜包覆的活性炭颗粒

由于分子筛膜的分离和催化作用, 分子筛膜包覆的传统催化剂颗粒可以实现高效的催化过程. 活性炭颗粒作为一种常用的催化剂载体, 由于其表面的憎水性和不平整, 在不规则活性炭颗粒表面直接水热合成包覆一层分子筛膜非常困难. 为了克服上述缺点, 本文采用一种勃姆石凝胶修饰的晶种法在活性炭颗粒表面合成连续的分子筛膜. 以勃姆石溶胶为前驱体, 在活性炭颗粒表面通过喷涂预先形成一层相对平整的勃姆石凝胶层以改善活性炭表面. 在随后的晶种涂覆过程中, 晶种分散液加入部分勃姆石溶胶为胶粘剂, 所得的晶种层覆盖载体完全, 与载体结合牢固, 无需焙烧处理. 将晶种涂覆后颗粒在旋转动态水热175℃处理6 h, 得到分子筛膜包覆的活性炭颗粒, 所得材料分别用X射线衍射和扫描电镜进行表征. 包覆的分子筛膜为MFI 结构, 厚度约为5μm. 对比实验表明, 没有勃姆石溶胶修饰的活性炭颗粒上不能成膜. 这种勃姆石凝胶修饰晶种法为在各种惰性载体上合成分子筛膜提供了便捷的方法.

Synthesis of MFI-Type Zeolite Membrane Encapsulated Activated Carbon Particles Using a Modified Seeded Method

Zeolite membranes with their advantageous separation and catalytic properties can be coated on traditional catalysts to achieve highly effective perfermance. It is difficult to coat zeolite membranes onto activated carbon (AC) particles, a commonly used catalyst support, because of the hydrophobic and rough surfaces of AC. To overcome these shortcomings, a boehmite gel modified seeded method was developed to synthesize MFI-type zeolite membrane encapsulated AC particles. By using the spray-coating process, the boehmite sol precursor was introduced in a gel layer on the AC surface to provide a smooth surface for seed dispersion and a binder for seed fixation. The obtained seed layer was dense and firm even without calcination. After 6 h rotary hydrothermal synthesis, continuous zeolite membrane encapsulated AC particles were obtained. The synthetic membrane type and the composite material morphologies were elucidated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results indicate that MFI-type zeolite membrane has a thickness of 5 μm. For comparison, on AC particles without boehmite gel modification, no continuous membrane forms. Our boehmite gel modified seeded strategy provides an efficient way to prepare zeolite membranes on different inert supports.