JPS57165359A - Preparation of unsaturated nitrile - Google Patents

Abstract

PURPOSE: To prepare the titled compound in high efficiency, utilizing the heat effectively, by recovering crude product of the ammoxidation reaction of an olefin using a recovering column, and distilling the crude product with various distillation columns each having a heater at a specific position using the vapor gnerated in the recovering column as the heat source for distillation.

CONSTITUTION: The ammoxidation reaction of an olefin is carried out in the reactor 1, and the produced reaction mixture containing unsaturated nitrile, saturated nitrile, and cyanic acid is absorbed in water in an absorption column 8, subjected to the extraction distillation in the recovering column 13, and distilled and purified by the cyanic acid removing column 21, the dehydration column 25 and the product distillation columns 28, etc. The distillation columns are operated in the following manner: the column is furnished with a heater 29 at the position where the temperature in the column becomes lower than the vapor temperature at the top of the recovering column; the distillation is carried out using the vapor from the recovering column as the distillation heat source; the liquid in the distillation column below the heater 29 is supplied to the re-distillation column 31 and distilled with the heater 32; the distillate obtained from the top of the column is circulated to the bottom of the product distillation column 28; the product (e.g. acrylonitrile) is condensed with the condenser 30; and the high-boiling component is extracted from the bottom of the re-distillation column 31.

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