| 摘要 |
Cellulose acetate butyrate gas separation membranes are prepared from a casting solution containing from about 10 to 30 percent polymer, 35 to 70 percent solvent, and 15 to 30 percent pore-forming agents. A film casting solution is cast onto a substantially flat support surface and a dense layer is formed on the exposed film surface. The film is gelled, washed, and dried to produce a particularly useful gas separation membrane. The cellulose acetate polymers used in this preparation have molecular weights of at least about 20,000, and have about 10 to about 45% butyryl groups, about 2 to about 35% acetyl groups, and about 0.8 to about 2 percent hydroxyl groups, by weight. The membranes may be used for separating a feed gas into a permeate fraction and a residual fraction, and are particularly useful for separating gases in the purge gas stream of ammonia plants to recover a permeate which is relatively rich in hydrogen. Cellulose acetate butyrate membranes may be used to improve the separation of ammonia plant purge gases which contain ammonia as well as hydrogen and nitrogen, especially when there is no pretreatment of the purge gas to remove ammonia gas. |
