Patent ID: 8083946

Claim:
A process for forming an appropriately selective membrane element within a membrane assembly and for using that membrane assembly for selectively separating a desired component from a hydrocarbon feedstream, the process comprising: a) forming a first membrane element comprised of a dianhydride, a halogenated diamine, an epoxy cross-linking agent, and a C 1 to C 18 polyalkyladipate difunctional dihydroxy polymer, and wherein the first membrane element has a retentate side and a permeate side and is comprised of a hard segment and soft segment, wherein the soft segment has a glass transition temperature, T g , less than 77° F. (25° C.); b) analyzing the first membrane element by infra-red spectroscopy to determine an Absorbance Infra-red Spectrum, so as to determine an Aliphatic C—H Area, defined by an absorbance peak and a baseline at wavenumbers approximately between 3150 and 3025 cm −1 , and an Aromatic C—H Area, defined by an absorbance peak and a baseline at wavenumbers approximately between 3025 and 2800 cm −1 ; c) for membrane elements having a ratio of the Aliphatic C—H Area to the Aromatic C—H Area of at least 10, forming a polymeric membrane assembly comprised of at least the first membrane element and at least a first support material; (d) contacting the retentate side of the polymeric membrane assembly with the hydrocarbon feedstream; and (e) retrieving a permeate stream from the permeate side of the polymeric membrane assembly; wherein the concentration by wt % of the desired component in the permeate stream is higher than the concentration by wt % of the desired component in the hydrocarbon feedstream.