The conversion of fossil fuels, by gasification, reforming, or partial oxidation processes is important for the synthesis of hydrogen and syngas which are subsequently used in refining, and for production of chemicals and fuels. Gas-separation steps are needed in the implementation of these technologies and membranes are commonly used for this purpose. Membrane reactors are a promising application because they combine reaction and separation in one step, overcoming equilibrium limitations in some chemical transformations.
It is known that palladium-based membranes are effective materials for hydrogen separation with high permeance and selectivity and high mechanical strength. In the present work a novel membrane preparation technique was used employing an electric-field to uniformly deposit Pd nanoparticle seeds on a substrate, followed by deposition of ultrathin Pd or Pd-Cu layers on the activated surface by electroless plating (ELP). To increase the membranes’ resistance to sulfur poisoning, phosphorus was incorporated in the structure and the peformance and sulfur resistance of the membranes were evaluated under exposure to a gas mixture of 100 ppm H2S in H2. The presence of phosphorus conferred structural integrity to the membranes, resulting in a more efficient regeneration under hydrogen flow after exposure to H2S.
The prepared membranes were used in a membrane reactor and tested for ethanol steam reforming for hydrogen production, using catalysts such as Co-Na/ZnO. The reactions were also carried out in in a packed bed reactor to evaluate the benefits of employing membranes. Ethanol conversion and hydrogen product yields were significantly higher in the membrane reactors compared to the packed bed reactor.