Novel purification method for formic acid

Abstract

The invention discloses a new method for formic acid purifying, which comprises the following steps: the aqueous solution of dilute formic acid with the mass concentration of more than 30 percent and anhydrous calcium chloride are mixed, heated to 80 distillation; and the mass ratio of the water in the aqueous solution of calcium chloride anhydrous and the aqueous solution of dilute formic acid is 1: 1.5 to 95 DEG C so as to lead the anhydrous calcium chloride to be dissolved, and then formic acid with high concentration is obtained through atmosphericto 1.8. The purifying method of formic acid is a process which has the advantages of simple and convenient operation, fastness, low cost and cleanness, thus being suitable for industrial production.

Description

(1) Technical field [0001] The invention relates to a new technology for purifying formic acid. (2) Background technology [0002] Formic acid, commonly known as formic acid, is a colorless liquid with a boiling point of 100.7°C and a melting point of 8.4°C. Formic acid is used as reducing agent, condensation agent, formylation reagent and solvent in synthesis. [0003] In the past, methods for purifying formic acid have been reported in the literature. For example, the French patent report in 1929 prepared anhydrous formic acid by reflux reaction of phthalic anhydride and aqueous formic acid. The principle of this method is that phthalic anhydride can selectively react with water to form phthalic acid, thereby removing the water in formic acid. However, the disadvantage of this method is that a large amount of phthalic acid formed by the reaction is difficult to recycle. Economic and environmental protection pressures. Add new entrainer in aqueous formic acid as British...

AI Technical Summary

Problems solved by technology

The principle of this method is that phthalic anhydride can selectively react with water to form phthalic acid, thereby removing the water in formic acid. However, the disadvantage of this method is that a large amount of phthalic acid formed by the reaction is difficult to recycle. Economic and environmental pressures

Add new entrainer in aqueous formic acid as British patent report in 1948, the obvious shortcoming of this type of method is: entrainer propyl formate, isobutyl formate etc. generally need to be prepared from anhydrous formic acid, simultaneously The consumption of entrainer is also relatively large, and the production cost is relatively high

Another example is the Chinese patent report in 1992, using SOCL 2 The principle of purifying dilute formic acid is that water in dilute formic acid and sulfite chloride selectively form hydrogen chloride and sulfur dioxide. Although this method can obtain high-concentration formic acid, it will cause certain pollution to the environment, and it will bring more problems in industrial implementation. high cost

Another example is the boric anhydride purification method reported in Chinese literature in 2006. Its principle boric anhydride (boron trioxide) reacts with water in dilute formic acid to form boric acid. After distillation, high-concentration formic acid can be obtained. Reuse, but boric acid is dried and dehydrated into boric anhydride, which can only be carried out at a temperature above 300°C, which is difficult to implement industrially, and boric anhydride is expensive, and the production cost is too high