Influence of toluene vapor on the H2-selective performance of dimethoxydiphenylsilane-derived silica membranes prepared by the chemical vapor deposition method

We have investigated the influence of coexisting toluene vapor on H2, N2 and SF6 permeation properties through dimethoxydiphenylsilane-derived silica membranes in the temperature range 573–298 K and toluene concentrations of 0.5%–2.0%. Among these three gases, N2 permeance was most susceptible to the influence of coexistence of toluene, resulting in the decrease of the permeance. In addition, we also confirmed that these decreased permeances recovered after keeping the membrane at 573 K for 5 h. Based on these results, the toluene molecules physically condensed or adsorbed on the membrane surface or the inside of the pores to prevent the permeation of the gases at lower temperature, and these molecules could be effectively removed at higher temperature. In addition, we successfully demonstrated, using a laser ionization compact analyzer that can measure the concentration every 50 s that this membrane can stably provide hydrogen with higher than 99.99% purity from a hydrogen gas mixture containing 2.0% toluene vapor.