以开孔的二维MFI纳米片为构筑单元制备沸石片膜

以食人鱼溶液(体积比为3∶1的95%～98%(w/w)H_2SO_4和30%(w/w)H_2O_2混合液)处理多层MFI(ML-MFI)除去有机结构导向剂(OSDA),经超声剥离和沉降纯化后得到了开孔的MFI沸石纳米片。采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、N_2吸附-脱附、傅立叶变换红外光谱(FT-IR)和热重分析(TGA)等手段对得到的MFI沸石纳米片进行表征,发现食人鱼溶液处理可移除ML-MFI中的OSDA,再经超声剥离得到可分散、开孔的MFI沸石纳米片。将MFI沸石纳米片用简单抽滤的方式沉积到自制Al_2O_3载体上,不经二次生长得到了连续的沸石纳米片膜。单组分气体渗透性能测试结果表明,制备的MFI沸石纳米片膜对正/异丁烷的理想选择性为4.1～5.8,正丁烷的渗透速率为2.2×10~(-7)～4.1×10~(-7) mol·m~(-2)·s~(-1)·Pa~(-1)。

Fabrication of Zeolite Membranes Using Two-Dimensional Open-Pore MFI Nanosheets as Building Blocks

Open-pore MFI zeolite nanosheets were prepared by removal of organic structure-directing agents (OSDA) from a multilamellar MFI zeolite (ML-MFI) using a mixture of 95%~98%(w/w) H₂SO₄ and 30%(w/w) H₂O₂ with V_H2SO4:V_H2O2=3:1 (known as piranha solution), followed by ultrasonication for exfoliation and sedimentation for purification. The exfoliated MFI zeolite nanosheets were characterized by various techniques, such as X-ray diffraction (XRD), scanning electron microscope (SEM), transmittance electron microscope (TEM), N₂ adsorption-desorption, Fourier transform infrared spectrometer (FT-IR) and thermal gravimetric analyzer (TGA), etc., indicating that OSDA was removed after the piranha solution treatment and dispersed, open-pore MFI nanosheets were obtained followed by exfoliation through ultrasonication. Continuous MFI nanosheet membranes were prepared by depositing the open-pore MFI nanosheets on home-made alumina disc supports by a simple vacuum-assisted filtration method. Single gas permeance tests on the MFI zeolite nanosheet membranes indicated that ideal selectivities for n-butane over i-butane of 4.1~5.8 with a permeance of n-butane of 2.2×10^-7~4.1×10^-7 mol·m^-2·s^-1·Pa^-1 were achieved.