Cycling method for preparing iminodiacetic acid from iminodiacetic acid disodium salt

Abstract

The invention discloses a new cycling process for preparing iminodiacetic acid from iminodiacetic acid disodium salt by a freezing crystallization method. The method is characterized by comprising the following steps: taking the iminodiacetic acid disodium salt as a starting raw material; adding water and stirring to decolorize and dissolve the iminodiacetic acid disodium salt; adding concentrated sulfuric acid dropwise to control pH at 1.8-2.1; centrifuging to obtain the iminodiacetic acid; adding an alkaline matter to acid pregnant liquor until the pH equals 4-7; separating Na2SO4.10H2O out by crystallization at the temperature of 5-10 DEG C; performing vacuum filtration, and recycling the filtrate to continuously prepare the iminodiacetic acid (IDA), wherein, content and desalination rate of the IDA are above 98%, and the yield is about 97%. The pregnant liquor is not discarded in the production process and the whole process can have a plurality of cycles, thus improving production efficiency and utilization rate of the raw material, and avoiding environmental pollution.

Description

technical field [0001] The invention relates to a method for preparing iminodiacetic acid, an intermediate of chemical products, in particular to a new process for preparing iminodiacetic acid using sodium salt of iminodiacetic acid as a raw material. Background technique [0002] Iminodiacetic acid (IDA) is an important raw material and intermediate for surfactants, complexing agents, synthetic metal surface treatment materials and ion exchange resins. Its largest use is to produce the herbicide glyphosate. At present, the technologies for industrialized production of iminodiacetic acid mainly include chloroacetic acid method, nitrilotriacetic acid method, hydrocyanic acid method and diethanolamine method. These processes are to first produce iminodiacetic acid sodium salt, and then obtain For iminodiacetic acid, the used or reported desalination methods include hydrochloric acid acidification, hot filtration, calcium salt complex precipitation and electrodialysis. [0003...

AI Technical Summary

Problems solved by technology

This method is easy to form calcium salt precipitation because iminodiacetic acid has very strong complexation, and yield is very high, but generates a large amount of calcium chloride waste liquids again while acidifying with hydrochloric acid, is more difficult to handle, causes water pollution

[0005] Chinese patent CN101186581A proposes a method of directly producing glyphosate with iminodiacetic acid sodium salt without going through the process steps of producing iminodiacetic acid, so that a large amount of sodium chloride is produced as a by-product in the process of producing diglyphosate. The whole system is viscous, and the mixing equipment is severely corroded, which not only affects the production capacity, but also has a large amount of waste water

Yang Hongquan and others used electrodialysis to prepare IDA in the article "Research on the Preparation of Iminodiacetic Acid" (Chemical Production and Technology. 2007, 14(2). 28-31). The resulting product has good quality, high yield and no waste water discharge , but this method is complicated to operate, the ion membrane is severely corroded by concentration polarization, the equipment is easily damaged, and the economic cost is high

Xu Liuxing and others proposed a method for acidifying IDA with concentrated sulfuric acid in "New Synthesis Process of Glyphosate Intermediate Iminodiacetic Acid" (Pesticides. 2006, 45 (11). 751-753), and the product purity reached 99.3%. But the yield is only 85%, which cannot meet the industrial requirements

[0006] The above methods are not complicated in process, high in equipment requirements, low in yield, large in three wastes, and high in cost, which are difficult to accept in industrial production.

Images