ZrO_2和Al_2O_3支撑的MFI型沸石分子筛膜:支撑体材料对膜性能的影响

Zirconia and Alumina Supported MFI Zeolite Membranes: Effects of Support Materials on Membrane Properties

采用水热合成法,以纯SiO2为源物质,在介孔Y2O3掺杂的ZrO2(YZ)及大孔a-Al2O3支撑体上制备出高质量的MFI型沸石分子筛膜。通过H2/n-C4H10气体混合物的渗透分离和p-xylene的蒸发研究了不同支撑体上MFI型沸石分子筛膜分离性能。在较低温度范围,YZ支撑的MFI型沸石分子筛膜中n-C4H10的渗透率比Al2O3支撑的膜高很多。最大n-C4H10与H2的分离率达到500。Al2O3支撑的膜中p-xylene的蒸发流量随时间下降很快,而YZ支撑的膜中的蒸发流量则变化缓慢。用XRD对膜的晶体结构进行分析,通过多种温度下热处理不同支撑体上的膜样品研究了其热稳定性与支撑体材料的关系。YZ支撑的MFI型沸石分子筛膜的MFI 结构在1000C 后仍能保持,而Al2O3支撑的膜950C 时已完全转变为石英相。研究结果表明,YZ支撑的MFI型沸石分子筛膜比Al2O3支撑的膜表现出更好的厌水性,热稳定性以及抗阻塞性。

Good quality MFI type zeolite membranes were prepared on mesoporous Y2O3 doped ZrO2 (YZ) support and macroporous a-Al2O3 support with pure SiO2 precursor by hydrothermal process. Permeation of binary mixture H2/n-C4H10 through zeolite membranes on YZ and a-Al2O3 supports was measured using a multi-component gas permeation set-up. YZ supported zeolite membrane had a much higher n-C4H10 permeance than the a-Al2O3 supported one in the lower temperature range. The maximum n-C4H10 to H2 separation factor of YZ supported zeolite membrane was as high as 500. Pure p-xylene pervaporation through these zeolite membranes was also conducted to study the membranes separation property. The pervaporation flux declined significantly with time for the a-Al2O3 supported zeolite membrane. Much less change in pervaporation flux was found for the YZ supported zeolite membrane. XRD was employed to analyze the phase structure of the zeolite membranes. The thermal stability of the YZ and a-Al2O3 supported MFI zeolite membranes was studied by comparing the phase structure of the zeolite films after heat-treatment at different temperatures. The zeolite membrane on the YZ support remained in the MFI structure up to 1000C. The zeolite membrane on the a-Al2O3 support transformed completely to a quartz phase after heat-treatment at 950C. Zirconia supported MFI type zeolite membrane is more hydrophobic, thermally stable and fouling resistant than the alumina supported one.