Unfortunately, I don't have any suggestions. I've researched a couple of handbooks and most of them refer to carbon systems where the VOC's are adsorbed on carbon and then regenerated with steam. My search did show up one link which may be helpful. The Department of Energy has done some research into high pressure membrane separation of VOC's from Air. The link is: http://www.frtr.gov/matrix2/section4/4_62.html. I am not sure about the pressure drop required, but that may be prohibitive.