| 摘要 |
1,271,104. Vinyl acetate. FARBENFABRIKEN BAYER A.G. 7 May, 1969 [10 May, 1968], No. 23224/69. Heading C2C. In a process for the purification of crude vinyl acetate containing acetic acid, water and ethyl acetate by azeotropic distillation of the vinyl acetate and water as the head product, and phase separation of the condensate, the vinyl acetate of this condensate is partly recycled to the azeotropic distillation column in a quantity such that the sump product contains 0À5 to 6% of water and acetic acid is obtained as the sump product. In a continuous process the tail acetic acid may be recycled through an evaporator to a reaction vessel in which vinyl acetate is prepared by reacting ethylene, acetic acid, molecular oxygen in the gaseous phase over a noble metal catalyst. A reflux ratio, based on the vinyl acetate of 3 to 8 is preferred. A second azeotropic distillation stage may be used to remove final water and acetaldehyde, and polymer impurities, and acetic acid traces are removed by a final distillation. In a modification an intermediate side stream may be withdrawn from the azeotropic distillation column and combined with the sump product to pass to an evaporator before recycling to the vinyl acetate production stage. This ethyl acetate rich liquid side stream may be taken from the distillation column, e.g. between the 8th and 16th plate of a 60 plate column. |
