Patent ID: 7997426

Claim:
A multi-layer membrane structure for use in acid environments, comprising: a first layer composed of a crosslinked polymeric membrane comprising a copolymer of crosslinked polyvinyl alcohol and, polyvinyl sulfate, such membrane having a first thickness, the membrane being selectively permeable to acid over hydrocarbons and further characterized as having a crosslink density from about 3.0% to about 15.0%, and wherein the crosslinked polymeric membrane is crosslinked utilizing a crosslinking agent selected from the group consisting of 1,4 diisocyanatohexane, 1,4 diisocyanatobutane, 1,8 diisocyanatooctane, 1,12 diisocyanatododecane, 1,5 diisocyanato-2-methyl pentane, and 4,4′ diisocyanato-diphenylmethane; a second layer composed of a fluoropolymer or a cellulosic polymer having a pore size that is less than half of the first thickness; and a third structural layer composed of a material with a pore size of at least 3 μm, an intrinsic bulk material value for the flexural modulus of greater than about 100×10 3 psi, and an intrinsic bulk material value for the tensile modulus of greater than about 10,000 psi.