The Selective Defect Reparation And Characterization Of MFI Membranes

Zeolite membranes own regular structure, good stabilities and catalytic performances, thus bear general applications as separation and catalysis membranes, chemical sensors, and microelectronic devices. The research on zeolite membranes has become one of the hot topics in advanced materials since 1990 s, and the obvious progress has been made so far. However, the fabrication technique of zeolite membranes is not good enough. Due to their own weaknesses, such as brittleness and polycrystalline structure, it is difficult to make defect-free zeolite membranes. Obviously, the defect of zeolite membranes is an important obstacle to the practical application of zeolite membranes. Therefore, fixing the defect of zeolite membranes without blocking zeolitic pores is a key issue toward their large-scale applications.Many achievements have been made in fixing defects of zeolite membranes, but there is still much to be desired for current fixing techniques, such as the limited reparation range, poor fixing selectivity and the complex reparation process. Accordingly, inspired by CVD and CLD methods, we proposed the innovative interfacial polymerization to realize the selective defect-patching of ZSM-5 zeolite membranes. In this method, trimesoyl chloride(TMC) and m-phenylenediamine(MPDA) were chosen respectively as monomers in organic and aqueous solutions, the diameters of the two monomers were bigger than that of zeolitic pores. The two monomers can only polymerize at the pore-mouth of defects if the differential pressure can be controlled properly. What's more, the created hydrophilic polyamide RO membranes containe uniform parallel pores, thus the membrane gets selectively repaired using this method. The self-inhibition reaction can be avoided without the pore-blocking of zeolite membranes, and the created RO membrane contains two kinds of holes, that is aggregation pores(r=2.1~2.4 ?) and network pores(r=3.5~4.5 ?). The radius of water molecules is 1.3 ?, so water molecules can get through while the ethanol molecules cannot. What's more, the RO membrane is hydrophilic. These factors described above can affect selective permeation of water molecules. So, the separation factor increases.Furthermore, FT-IR, SEM, Contact-angle and other measurements had been used in the process of experiments. Experimental results show the ZSM-5 zeolite membranes get selectively repaired by the created RO membrane, the defects are reduced to less than 1 nm and pore size distribution is concentrated in a range that smaller than 0.6 nm, the separation factor of C2H5OH/H2 O can be increased to more than 16 from 1, and the permeation flux can be kept larger than 1 kg/m2·h.