Synthesis and pervaporation performance of mordenite membranes on mullite tubes

Mordenite membranes were synthesized on porous mullite tubes by secondary growth method using a template-free aluminosilicate gel with molar compositions of n_Na2_O:n_Al2_O3,:n _SiO2:n_H2_O =0.25:0.015∼0.1:1:15∼60. The as-synthesized mordenite membranes were characterized by x-ray diffraction (XRD) and scanning electron microscope (SEM). The effects of synthesis conditions such as synthesis time, n Al₂O_3nAl ₂O₃ ratio, n_H2_O n_Al2 _O3 ratio, and silica source on the crystallization and the pervaporation(PV) properties of zeolite layers were investigated. The increase in synthesis time could accelerate the formation of mordenite membranes preferentially oriented with c axis normal to the support surface. However, the oriented mordenite top layer does not improve the flux and selectivity toward a water/ethanol mixture by PV. Under optimized reaction conditions, the as-synthesized membrane shows high PV performance with a flux of 0.70 kg • m^-2• h^-1 and separation factor of 860 for a feed of 10wt% water/ethanol mixture at 348 K. The high PV performance could be contributed to the compact intermediate zeolite layer between the support layer and top layer based on the results of XRD and SEM characterization.