中空ZSM-5分子筛微球及其吸附与催化性能

Hollow ZSM-5 Zeolite Microspheres with Improved Adsorption and Catalytic Properties

首先利用聚乙二醇作为软模板合成出具有一定介孔结构的ZSM-5分子筛微球,再通过快速可控碱刻蚀的方法,成功制备出尺寸均一的中空分子筛微球。利用X射线衍射(XRD)、氮气吸附等温线分析(N2 isotherm)、扫描和透射电子显微镜(SEM,TEM)对所制备的中空分子筛微球进行了表征,并研究了中空分子筛微球对有机物废水的吸附性能和对大分子的催化裂解性能。结果表明,刻蚀后分子筛结晶度略有下降,但是介孔度和孔体积明显提升。中空分子筛微球外径在600 nm,壳层厚度在100 nm左右。此外,该中空结构不仅对苯等有机分子具有吸附富集作用,其饱和吸附量几乎达到了常规分子筛微球的3倍,并且六次循环使用后的吸附容量依然保持基本不变,显示出较高的吸附容量和循环使用稳定性。在异丙苯和三异丙苯裂解反应中中空分子筛微球也显示出较高的催化活性。

A new kind of uniform hollow zeolite spheres were successfully synthesized by non-hard template synthetic method, which involves two key steps： firstly, the conventional hydrothermal synthesis process of zeolite spheres by using polyethylene glycol（PEG） as soft template, and then, the rapid post-alkaline-etching（PAE） technique. Structural features were characterized by XRD, N2 isotherm, SEM, and TEM. The performance in the organic-waste-water treatment and catalytic cracking of bulky molecules were also measured. It was found that crystallinity of the product underwent a reducing tendency after alkaline etching treatment, but the mesoporosity and pore volume were promoted. The diameter and shell thickness of hollow zeolite spheres were about 600 nm and 100 nm, respectively. Moreover, such hollow structure demonstrates remarkably a threefold capability increase in adsorption of benzene molecules in methanol solution if compared with conventional zeolite spheres. Such capability can be basically kept after repeating 6 times, indicating high capability and stability in adsorption. Enhanced catalytic activities were also approved in cracking of isopropyl benzene and triisopropyl benzene.