Composite-alumina-carbon molecular sieve membranes prepared from novolac resin and boehmite. Part II: Effect of the carbonization temperature on the gas permeation properties

The influence of carbonization temperature on the permeation properties and aging of thin (4 μm) supported carbon molecular sieve membranes (c-CMSM), prepared from in house synthesized novolac phenolic resin loaded with boehmite nanoparticles, were studied. Just after membrane carbonization (fresh membrane), high permeance to N₂ and O₂ and low O₂/N₂ permselectivities were observed; the highest permeations were observed for carbonization end temperatures between 500 °C and 700 °C. After leaving the c-CMSM 1 day in the air, a large decrease in the permeation and considerable increase in the permselectivity were observed due to the reduction of the pore size by oxygen chemisorption and water physical adsorption; the permeability to H₂ and H₂/N₂ ideal permselectivity for a membrane carbonized at 550 °C are close to palladium membranes for low temperature (<100 °C). The effect of the permeation characteristics of the membranes carbonized at various temperatures and the removal of water adsorbed in the pores by heat treatment were studied.