Mild ultraviolet detemplation of SAPO-34 zeolite membranes toward pore structure control and highly selective gas separation

SAPO-34 zeolite membranes were activated by ultraviolet (UV) radiation at low temperatures to reduce grain boundary defects. The successful detemplation of SAPO-34 zeolite powders using UV radiation was confirmed by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and nitrogen adsorption-desorption. The irradiance exerted a significant impact on the quality of UV-detemplated SAPO-34 membranes. Under optimal UV detemplation conditions, SAPO-34 membranes showed a moderate H 2 permeance of ∼10 −7 mol Pa −1 m −2 s −1 , with a H 2 /i-C 4 H 10 permselectivity over 75 under room temperature. The membranes showed an exceptionally low CO 2 permeance in comparison with N 2 and CH 4 despite the smaller molecular size of CO 2 , resulting in an unprecedentedly high H 2 /CO 2 permselectivity over 50, which was ascribed mainly to the intense interaction between the CO 2 molecules and confined organic structure directing agent (OSDA) residue in membrane channels. The temperature dependence of singe-gas permeance through SAPO-34 zeolite membranes showed that gases, including He, H 2 , CO 2 , CH 4 , C 2 H 6 , C 3 H 8 , and i-C 4 H 10 , markedly increased as the temperature increased, indicating an activated diffusion mechanism. The activation energies for H 2 permeation through the SAPO-34 membranes were 17–23 kJ mol −1 , which were reasonable based on the correlation between the activation energy for H 2 permeation and the average pore size for reported membranes by assuming minimal grain boundary defects in the UV-detemplated SAPO-34 membranes.