Hydrogen Separation by Natural Zeolite Composite Membranes: Single and Multicomponent Gas Transport

Single and multicomponent gas permeation tests were used to evaluate the performance of metal-supported clinoptilolite membranes. The efficiency of hydrogen separation from lower hydrocarbons (methane, ethane, and ethylene) was studied within the temperature and pressure ranges of 25-600 degrees C and 110-160 kPa, respectively. The hydrogen separation factor was found to reduce noticeably in the gas mixture compared with single gas experiments at 25 degrees C. The difference between the single and multicomponent gas results decreased as the temperature increased to higher than 300 degrees C, which is when the competitive adsorption-diffusion mechanism was replaced by Knudsen diffusion or activated diffusion mechanisms. To evaluate the effect of gas adsorption, the zeolite surface isotherms of each gas in the mixture were obtained from 25 degrees C to 600 degrees C. The results indicated negligible adsorption of individual gases at temperatures higher than 300 degrees C. Increasing the feed pressure resulted in a higher separation efficiency for the individual gases compared with the multicomponent mixture, due to the governing effect of the adsorptive mechanism. This study provides valuable insight into the application of natural zeolites for the separation of hydrogen from a mixture of hydrocarbons.