New Membranes for Hydrogen and Syngas Production

Syngas is an important feedstock for the production of higher hydrocarbons or methanol. It can be produced via conversion of methane and the most extensively used process for this conversion is the methane steam reforming reaction carried out in large furnaces. On the other hand, hydrogen is nowadays produced via conversion of methane to syngas and successive water gas shift reaction and purification. Methane steam reforming is a highly endothermic reaction which is industrially operated under severe conditions resulting in several undesirable consequences: sintering of the catalyst, very high carbon deposition and the use of high-temperature resisting materials. These drawbacks for methane steam reforming can be overcome by using membrane reactors, systems able to combine the separation properties of membrane with the typical characteristics of catalytic reactions. By using for example Pd-based membrane reactors, the hydrogen produced can be continuously withdrawn from the reaction system circumventing the thermodynamic limitations and making the methane steam reforming feasible at lower temperatures than the traditional systems. A potential alternative technique to steam reforming processes for producing syngas is the partial oxidation of methane with oxygen, having the disadvantage (economical and technological) that pure oxygen is required. Using air instead of pure oxygen is beneficial only if it can be performed by using a membrane reactor in which the membrane is perm-selective to oxygen. Another possible route for the partial oxidation of methane is the use of catalytic membrane reactors in which the membrane acts as both separation layer and reaction media. In this chapter new membranes to be used in syngas production and in hydrogen production will be discussed.

Keywords: Membrane reactors, hydrogen production, syngas production, partial oxidation of methane, Pdbased membranes.