The Economic Viability of Using Membranes in Chemical Processes Involving Hydrogen Transport

Recently, scientists in several countries, notably Russia, have succeeded in developing several composite membranes for separation uses. The membranes are made of extra-thin films of palladium (Pd) or its alloy, occasionally with another extra-thin film of other metals, and supported on porous ceramic or metals. Such membranes have the unique property of 100% permselectivity to hydrogen, as well as a tolerable degree of permeability. Because of the extra-thin Pd layer the membrane does not suffer the physical weakness of the dense Pd membranes and it is not so expensive to manufacture. Resolution of these problems opens the way for industry to study their use in processes that involve hydrogen transport, such as dehydrogenation and hydrogenation.

In this review we evaluate the economic viability of these membrane processes, viz., making hydrogen via methane reforming and styrene via ethylbenzene dehydrogenation. Using a short-cut method, we compare costs incurred for the membrane processes with those of the conventional nonmembrane processes. In both cases, the results indicate that the membrane process using a proper composite Pd-Ag or Pd membrane may make the membrane process economically viable. Even an existing styrene plant using the present commercial process may be modified to use these mem-branes economically.