초록

A process for separating a component from a low molecular weight organic mixture by pervaporation. The process uses fluorinated membranes and is particularly useful for treating mixtures containing light organic components, such as methane, propylene or n-butane.

대표청구항 ▼

We claim: 1. A pervaporation process for separating a first component from a liquid organic mixture, comprising the steps of: a) passing the liquid organic mixture across the feed side of a separation membrane having a feed side and a permeate side, the separation membrane having a selective layer

We claim: 1. A pervaporation process for separating a first component from a liquid organic mixture, comprising the steps of: a) passing the liquid organic mixture across the feed side of a separation membrane having a feed side and a permeate side, the separation membrane having a selective layer comprising a polymer comprising repeat units of a cyclic structure of an at least 5-member fluorinated ring, the polymer having a fractional free volume less than 0.3, a glass transition temperature of at least about 100° C., and an oxygen permeability below 800 Barrer; (b) providing a driving force for transmembrane permeation; (c) withdrawing from the permeate side a permeate vapor stream enriched in the first component compared to the liquid organic mixture; (d) withdrawing from the feed side a residue liquid stream depleted in the first component compared to the liquid organic mixture. 2. The process of claim 1, wherein the first component is propylene and the liquid organic mixture further comprises propane. 3. The process of claim 1, wherein the first component is n-butane and the liquid organic mixture further comprises isobutane. 4. The process of claim 1, wherein the first component is an aromatic compound. 5. The process of claim 1, wherein the first component is a C1-2 hydrocarbon and the liquid organic mixture further comprises C3+ hydrocarbons. 6. The process of claim 1, wherein the polymer is formed from a monomer chosen from the group consisting of fluorinated dioxoles, fluorinated dioxolanes and fluorinated cyclically polymerizable alkyl ethers. 7. The process of claim 1, wherein the polymer comprises a perfluorinated polymer. 8. The process of claim 1, wherein the polymer is a polyperfluoro (alkenyl vinyl ether). 9. The process of claim 1, wherein the polymer comprises a copolymer. 10. The process of claim 1, wherein the polymer has the formula: where x and y represent the relative proportions of the dioxole and the tetrafluoroethylene blocks, such that x+y=1. 11. The process of claim 1, wherein the polymer has the formula: where n is a positive integer. 12. The process of claim 1, wherein the separation membrane comprises a composite membrane. 13. The process of claim 1, wherein the polymer is unfilled. 14. The process of claim 1, wherein the oxygen permeability is below 300 Barrers. 15. The process of claim 1, wherein the permeate side is at a pressure of at least about atmospheric pressure. 16. The process of claim 1, further comprising passing at least a portion of a stream chosen from the permeate vapor stream and the residue liquid stream to additional separation treatment. 17. The process of claim 1, further comprising condensing at least a portion of the permeate vapor stream. 18. The process of claim 1, further comprising condensing at least a portion of the permeate vapor stream by dephlegmation. 19. The process of claim 1, further comprising passing at least a portion of a stream chosen from the permeate vapor stream and the residue liquid stream to a distillation step. 20. The process of claim 1, wherein the liquid organic mixture comprises a fraction from a distillation step. 21. A pervaporation process for separating a first component from a liquid organic mixture, comprising the steps of: (a) passing the liquid organic mixture across the feed side of a separation membrane having a feed side and a permeate side, the separation membrane having a selective layer comprising a fluorinated polymer having a fractional free volume less than 0.3, a glass transition temperature of at least about 100° C., a fluorine:carbon atom ratio in the polymer of at least 1:1, and an oxygen permeability below 800 Barrer; the separation membrane being further characterized in that it provides a membrane selectivity in favor of propylene over propane of at least about 3 and a propylene pressure-normalized flux of at least about 10 GPU when challenged at 20° C. with a liquid mixture of 50 wt % propylene/50 wt % propane at a feed pressure of 150 psig and a permeate pressure of 0 psig; (b) providing a driving force for transmembrane permeation; (c) withdrawing from the permeate side a permeate vapor stream enriched in the first component compared to the liquid organic mixture; (d) withdrawing from the feed side a residue liquid stream depleted in the first component compared to the liquid organic mixture. 22. The process of claim 21, wherein the first component is propylene and the liquid organic mixture further comprises propane. 23. The process of claim 21, wherein the first component is n-butane and the liquid organic mixture further comprises isobutane. 24. The process of claim 21, wherein the first component is an aromatic compound. 25. The process of claim 21, wherein the first component is a C1-2 hydrocarbon and the liquid organic mixture further comprises C3+ hydrocarbons. 26. The process of claim 21, wherein the polymer has a ratio of fluorine to carbon atoms of at least about 1:1. 27. The process of claim 21, wherein the polymer comprises a perfluorinated polymer. 28. The process of claim 21, wherein the polymer is a polyperfluoro (alkenyl vinyl ether). 29. The process of claim 21, wherein the polymer comprises a copolymer. 30. The process of claim 21, wherein the polymer has the formula: where x and y represent the relative proportions of the dioxole and the tetrafluoroethylene blocks, such that x+y=1. 31. The process of claim 21, wherein the polymer has the formula: where n is a positive integer. 32. The process of claim 21 wherein the polymer is unfilled. 33. The process of claim 21, wherein the oxygen permeability is below 300 Barrer. 34. The process of claim 21, wherein the separation membrane comprises a composite membrane. 35. The process of claim 21, wherein the permeate side is at a pressure of at least about atmospheric pressure. 36. The process of claim 21, further comprising passing at least a portion of a stream chosen from the permeate vapor stream and the residue liquid stream to additional separation treatment. 37. The process of claim 21, further comprising condensing at least a portion of the permeate vapor stream. 38. The process of claim 21, further comprising condensing at least a portion of the permeate vapor stream by dephlegmation. 39. The process of claim 21, further comprising passing at least a portion of a stream chosen from the permeate vapor stream and the residue liquid stream to a distillation step. 40. The process of claim 21, wherein the liquid organic mixture comprises a fraction from a distillation step. 41. A pervaporation process for separating a liquid organic mixture comprising propylene and propane, comprising the steps of: (a) passing the liquid organic mixture across the feed side of a separation membrane having a feed side and a permeate side, the separation membrane having a selective layer comprising a fluorinated polymer having a fractional free volume less than 0.3, a glass transition temperature of at least about 100° C., a fluorine:carbon atom ratio in the polymer of at least 1:1, and an oxygen permeability below 800 Barrer; and either: (i) wherein the selective layer comprises repeat units of a cyclic structure of an at least 5-member fluorinated ring, or (ii) wherein the separation membrane is further characterized in that it provides a membrane selectivity in favor of propylene over propane of at least about 3 and a propylene pressure-normalized flux of at least about 10 GPU when challenged at 20° C. with a liquid mixture of 50 wt % propylene/50 wt % propane at a feed pressure of 150 psig and a permeate pressure of 0 psig; (b) providing a driving force for transmembrane permeation; (c) withdrawing from the permeate side a permeate vapor stream enriched in propylene compared to the liquid organic mixture; (d) withdrawing from the feed side a residue liquid stream depleted in propylene compared to the liquid organic mixture. 42. The process of claim 41, wherein the oxygen permeability is below 300 Barrer.