| 摘要 |
Hydrogen cyanide is removed from ammonia gas by washing with a liquid nitrile, e.g. b ,b 1-dicyanodiethylether, or b -methoxy-, b -ethoxy-, b - n - propoxy-, b - i - propoxy-, b - n - butoxy-, b - i - butoxy-, b - pentoxy-, b - cyclopentoxy-, b - cyclopentoxy-, b - cyclohexoxy-, or b -benzoxypropionitrile. The ammonia gas may also contain propylene or isobutylene; air or oxygen; and a volatile nitrile, e.g. acrylo-, methacrylo-, propio-, or aceto-nitrile. Any cyanide. Ammonia may be recovered from the washed gas by further washing, e.g. with water. In one embodiment (Fig. 1, not shown) for a gas containing a mol. ratio of HCN/nitrile of less than 3/7 , the gas is passed upwards through a first tower in countercurrent with a recycled washing liquid which is then passed to the centre portion of a second tower in which absorbed ammonia is removed by blowing with an inert gas and desorbed hydrogen cyanide and nitriles are re-absorbed in further recycled washing liquid. The absorbed hydrogen cyanide and nitriles are then distilled off in a third tower and the solvent recycled to the top of the first and second towers. In a modification (Fig. 2, not shown) for a gas containing a mol. ratio of HCN/nitrile of more than 3/7 , the liquid being distilled in the third tower is blown with inert gas, the gas evolved is washed with 1-2N aqueous sulphuric acid in a fourth tower to remove ammonia, hydrogen cyanide and nitriles are distilled off from the sulphuric acid in a fifth tower and the acid is recycled to the fourth tower. The residence time in each of the first and second towers may be 2-30 minutes. The first and second towers may be combined. The inert gas injected into the second and third towers may be nitrogen, carbon dioxide, propylene, or air. The distillation in the third tower may be effected at atmospheric or sub-atmospheric pressure. Specification 928,777 is referred to. |
