Clean reclaiming process for byproduct chloromethane of glyphosate acid

Abstract

The discharged exhaust gas during the glyphosate acid production process through phosphorous acid alkyl acid includes 20-90% of methyl chloride, methanol, formaldehyde dimethyl acetal, water, hydrogen chloride and other foreign matter, by solvent absorption of foreign matter, condensation impurity or charging part of the foreign matter such as methanol, formaldehyde dimethyl acetal into hydrochloride-containing liquid and converting it into methyl chloride, high purity of methyl chloride can be obtained. The process not only solves the problem of environmental pollution in the glyphosate acid production, the production cost can also be lowered substantially.

Description

[0001] This application is a divisional application of a Chinese patent application with an application date of July 23, 2002, a publication date of October 8, 2003, and application number 02125282.3. technical field [0002] The invention relates to a method for purifying and recovering hydrolysis tail gas during the synthesis of glyphosate acid, more specifically, recovering methyl chloride as a by-product with high yield from the tail gas discharged from the production of glyphosate acid, and the process does not produce secondary pollution. Background technique [0003] Glyphosate is the herbicide with the largest sales volume and the fastest growth rate in the world. The total production of glyphosate technical products in the world has reached 260,000 tons. With the successful development and popularization of glyphosate-resistant transgenic crops, It provides a new opportunity for the continued development of glyphosate...

AI Technical Summary

Problems solved by technology

However, this process has some shortcomings in recovery rate and environmental protection: ① low recovery rate

Since the tail gas contains saturated or supersaturated methylal and methanol under normal pressure, if it cannot be removed during washing, it will cause high consumption of desiccant after being brought into the drying system, and affect the quality of recovered methyl chloride.

However, affected by the solubility and mass transfer rate of methylal and methanol in water, in order to ensure the quality of reclaimed methyl chloride, it is necessary to wash with a large amount of water (6 tons / ton of methyl chloride), and methyl chloride has a certain solubility in water ( 0.38 g / liter), the large amount of washing water causes the dissolution loss of methyl chloride in water to increase, which affects the recovery rate; 2. pollutes the environment

Although this process can recover most of the methyl chloride in the exhaust tail gas and reduce the environmental pollution caused by the production of glyphosate acid, the defects of the process itself make it impossible to completely solve the environmental protection problem. A large amount of washing water dissolves the methyl chloride in the tail gas. Acetal, methanol, methyl chloride and other organic compounds, and low content of these substances can not be recovered by economical methods, only biochemical treatment or discharge, resulting in environmental pollution; if biochemical treatment is carried out, due to methylal and chlorine Methane is a difficult biochemical substance, and the cost of processing it is relatively high

③ Poor quality of recycled methyl chloride

The impurities (moisture content, methylal, methanol) contained in the glyphosate acid by-product chloromethane recovered by the three-stage treatment process described in this process are too high, and will react with the target product in the synthesis of methyl chlorosilane The formation of polymers or thermal cracking will coke and coke on the surface of the catalyst, thereby affecting production