Preparation method of green chelating agent tetrasodium glutamate diacetate

Abstract

The invention provides a preparation method of a green chelating agent tetrasodium glutamate diacetate. The method specifically comprises the steps as follows: sodium glutamate and chloroacetic acid are subjected to an SN2 bimolecular nucleophilic substitution under an alkaline condition at a certain temperature to produce a tetrasodium glutamate diacetate water solution. Chloroacetic acid and a caustic soda liquid are dropwise added to a kettle simultaneously, the pH value of the reaction system is kept in the range of 9-12 by controlling the addition speed of the caustic soda liquid, and meanwhile, negative pressure of 0-minus 0.005 MPa is established. Sodium glutamate and chloroacetic acid which are soluble in water are used as raw materials, a process method of partially neutralizing sodium glutamate and removing water out of the reaction system during the reaction is adopted, so that reaction substrates always keep higher reaction activity, and the reaction yield and reactant conversion rate are increased; the reaction cycle is short, the production process is simple, and the yield can reach 96% or above; the method is safe, environmentally friendly and high in operability, does not produce toxic byproducts or wastewater, can realize energy saving and emission reduction, is low in cost and facilitates large-scale industrial production.

Description

technical field [0001] The invention belongs to the technical field of organic synthesis and provides a preparation method for synthesizing a green chelating agent tetrasodium glutamate diacetate by using sodium glutamate and chloroacetic acid as raw materials. Background technique [0002] Chelating additives such as ethylenediaminetetraacetic acid (EDTA), aminotriacetic acid (NTA), and sodium tripolyphosphate (STPP) are commonly used in traditional industrial and household detergents. Although EDTA has the characteristics of strong complexing ability and good alkali resistance, it has weak dispersion and is not easy to be biodegraded; while NTA is a suspected carcinogen, and its use has been regulated by the United States and the European Union many years ago ; In recent years, due to the increasingly serious problem of eutrophication in rivers and lakes, the use of phosphorus-containing additive STPP also tends to be strictly prohibited. Environmental changes and global ...

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Problems solved by technology

Patent CN101784513B introduces a method for preparing glutamic acid-N,N-diacetic acid alkali metal salts using L-glutamic acid, formaldehyde and hydrogen cyanide and its salts as raw materials. The product of this method has high impurity content, and The raw material hydrocyanic acid used is highly toxic, and the waste water produced contains a large amount of cyanide residue, and it is easy to corrode the production equipment

Chinese patent 201210073918.X discloses a method of using zinc salt to catalyze the reaction of L-glutamic acid and 2-chloroacetonitrile in an organic base system such as pyridine and triethylamine, and then neutralizing the base with sodium hydroxide to prepare glutamic acid Tetrasodium diacetate (GLDA.Na 4 ), because the solubility of L-glutamic acid in water at room temperature is extremely low, so this method needs to dissolve glutamic acid at high temperature and then lower it to low temperature to add raw materials 2-chloroacetonitrile and organic base. After alkali, it needs to reflux to discharge the generated ammonia, and the generated product has a dark color. This method has complicated process operation, long process cycle and high energy consumption.

It is reported in Chinese literature that L-glutamic acid and chloroacetic acid are used as raw materials, LiOH is added to adjust the pH of the system and mixed uniformly, heated for 5 to 6 hours, acidified with hydrochloric acid, recrystallized and washed with decompressed ethanol to prepare N , the method of N-dicarboxymethyl-L-glutamic acid, the yield of the product prepared by this method is low, the reaction time is long, and the cost is high

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