Separation and Purification Technology, Vol.210, 659-669, 2019
Effect of calcination atmosphere on microstructure and H-2/CO2 separation of palladium-doped silica membranes
Palladium-doped silica materials with Si-CH3 groups were fabricated by sol-gel method under various calcination atmospheres and membranes were made thereof by coating process. The results showed that air atmosphere can lead to the partial oxidation of metallic Pd to Pd-0 while N-2 and H-2 atmospheres can effectively prevent metallic Pd from being oxidized. H-2 atmosphere is proved to be a more prominent way to slow down the decomposition of organic Si CH3 group than N-2 and air atmospheres. The surface area, micropore volume and porosity of palladium-doped silica membrane material calcined in H-2 atmosphere are much higher than those calcined in N-2 atmosphere. Compared with N-2 atmosphere, the palladium-doped silica membranes calcined in H-2 atmosphere showed higher H-2 permeability and H-2/CO2 selectivity before and after the steam exposure. The apparent activation energy of H-2 permeation through the palladium-doped silica membrane calcined under H-2 atmosphere (2.51 +/- 0.05 kJ/mol) was slightly lower than that calcined under N-2 atmosphere (2.84 +/- 0.04 kJ/mol). Calcination atmosphere plays some role in membrane performance, which has greater influence on the permeance than on the gas permselectivity. Calcination under H-2 atmosphere is well conducive to improve the gas permeance and H-2 permselectivity of palladium-doped silica membrane.
Keywords:Palladium-doped silica membrane;Calcination atmosphere;Hydrothermal stability;H-2/CO2 separation;Apparent permeation activation energy