Development of an optimized process for recovery and reuse of spent membranes for hydrogen separation

In the last years, the growth in hydrogen's demand has created considerable interest in the development of more efficient processes for its production. The production of hydrogen with membrane reactors is considered one of the most promising areas. The key concept of membrane reactors is to separate the hydrogen meanwhile it is produced, thus shifting the chemical equilibrium towards reaction products in order to obtain higher conversions of the hydrocarbon feedstock, at lower temperatures, thereby increasing the energy efficiency of the conversion process. The fundamental element of this new technology is the presence of a membrane semipermeable to hydrogen. For the most interesting membranes, from an industrial point of view, however their cost still prohibitive (up to 10,000 a��/m2), it evidences that a potential recovery and recycling of the main elements constituting the membrane can potentially contribute to a significant reduction in the unit production cost. The purpose of this work is to identify an optimized process for the recovery of membranes based on palladium and silver, prepared from substrates of stainless steel, since this particular configuration seems to be the most promising in terms of hydrogen recovery, purity and for a potential scale-up. Hydrometallurgical processes were identified as the best solution for the dissolution of Pd and Ag. The leaching process was carried out at different times, temperatures and acid solutions concentration. The reaction products were analysed by atomic absorption spectrophotometry and scanning electron microscopy. The optimal leaching solution allowed to completely remove the selective layer of Pd and Ag, while leaving the support undamaged. The results obtained enabled the development of an optimized process scheme and the design of a reactor to this aim. A preliminary economic evaluation confirms that such type of process could help at least to reduce in 50% the cost of the membrane per m2.