Patent ID: 6572679
Filing Date: 2003-06-03
Classification: B01D,C01B

Abstract:
A process for treating a gas mixture comprising a gaseous hydrocarbon and a second gas, the process comprising:(a) providing a first membrane unit containing a first membrane having a first feed side and a first permeate side, the first membrane being selective in favor of the gaseous hydrocarbon over the second gas; (b) providing a second membrane unit containing a second membrane having a second feed side and a second permeate side, the second membrane being selective in favor of the second gas over the gaseous hydrocarbon, and including a selective layer comprising a polymer comprising repeating units having a fluorinated cyclic structure of an at least 5-member ring, the polymer having a fractional free volume no greater than about 0.3; â€ƒthe second membrane unit being connected in series with the first membrane unit such that gas leaving the first feed side can enter the second membrane unit on the second feed side; (c) passing the gas mixture into the first membrane unit and across the first feed side; (d) providing a first driving force for transmembrane permeation; (e) withdrawing from the first feed side a first residue stream depleted in the gaseous hydrocarbon compared with the gas mixture; (f) withdrawing from the first permeate side a first permeate stream enriched in the gaseous hydrocarbon compared with the gas mixture; (g) passing the first residue stream into the second membrane unit and across the second feed side; (h) providing a second driving force for transmembrane permeation; (i) withdrawing from the second feed side a second residue stream depleted in the second gas compared with the first residue stream; (j) withdrawing from the second permeate side a second permeate stream enriched in the second gas compared with the first residue stream.