| 摘要 |
PURPOSE:To enable the dehydrative distillation of the titled aqueous solution in high thermal efficiency, using a specific entrainer, by evaporating a part of the entrainer phase of the condensed liquid of the column top vapor or evaporating at least a part of the side-cut liquid of the liquid recycling in the column, and returning the vapor to the raw material feeding stage of the dehydrative distillation column or a downstream stage thereof. CONSTITUTION:An aqueous solution 1 of a carboxylic acid such as formic acid, acetic acid, propionic acid, etc. is subjected to the dehydrative distillation 2 using an entrainer separable from water to form two phases in the condensed liquid of the column top vapor, and having a boiling point lower than that of the carboxylic acid, e.g. benzene, toluene, hexane and/or ethyl acetate, etc. In the above process, a part of the entrainer phase in the condensed liquid of the column top vapor or at least a part of the side-cut liquid of the liquid recycling in the column is taken out of the dehydrative distillation column, subjected to the heat exchange 7 with a heat source sufficient to vaporize the liquid, preferably with the column top vapor or the column bottom liquid, and the evaporated vapor is supplied 8 to the stage below the raw material feeding stage of the dehydrative distillation column 2. The dehydrative distillation of the above aqueous solution can be carried out in an extremely high efficiency, using a low-grade heat source.
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