Abstract: This article briefly describes the application of glycine in food, medicine, feed, pesticides, etc., and systematically introduces the current situation, development trends, and research progress of China’s glycine production technology.
1 Application of glycine
Glycine is an important organic compound with a simple structure. With the continuous improvement of people’s living standards and the need for physical health, glycine has become a bulk raw material used in the food and pharmaceutical industries and has been widely used in pesticides, feed, daily chemical industries, and other industries. According to the different production technology and product quality requirements of glycine, it can be divided into four specifications products: food grade, pharmaceutical grade, feed grade, and industrial grade.
In the food industry, adding an appropriate amount of glycine to beverages, canned foods, dairy products, and preserved foods can not only prevent food from spoilage but also extend its shelf life. In animal and plant food processing, adding glycine to the sweet sauce, fruit juice, soy sauce, and vinegar can not only play the role of seasoning and flavor enhancement but also achieve the purpose of increasing food nutrition and improving food flavor.
In medicine, glycine can synthesize a variety of drugs. For example, calcium carbonate preparations for inhibiting gastric ulcers, delapril hydrochloride, calcium monoglycine acetylsalicylate, paracetamol glycinate, thiamphenicol, and reseramine injections for the treatment of hypertension.
Adding an appropriate amount of glycine to the feed can not only improve the nutrient content of the livestock and poultry feed but also prevent the feed from oxidative deterioration and prolong the freshness and use period of the feed.
Industrial grade glycine is mainly used for the large-scale production of the herbicide glyphosate. Glyphosate has been widely used in China in recent years for weeding in a variety of crops and non-arable lands such as transportation, forests, and construction due to its strong herbicidal power, easy decomposition, low toxicity, and no residue.
Glycine can also be used as a solvent and biochemical reagent in organic synthesis and is also widely used in the daily chemical industry.
2 Current status of glycine production technology in China
At present, the production technology of glycine in China is mainly based on the chloroacetic acid ammonolysis process. The difficulty of this process is the separation of the main product glycine and the by-product ammonium chloride. The main problems are the use of toxic and flammable methanol alcohol precipitation method to separate glycine, the amount of methanol is large, and the recovery of methanol requires increased equipment investment; the one-time consumption of the catalyst urotropine causes a large waste of raw materials; at the same time, there is a large amount of mother liquor. , The mother liquor processing capacity is large. Due to the high energy consumption and high material consumption of the process of producing glycine by chloroacetic acid ammonolysis, it directly leads to high production costs and a lack of international competitiveness.
Focusing on the problems in the process technology for the production of glycine by the chloroacetic acid ammonolysis method, Chinese glycine production enterprises, universities, and scientific research institutions are based on the principles of optimizing production process conditions, reducing production costs, and improving product quality. The process has done a lot of research work and technological transformation. For example, in the separation process, alkalization deamination method, ion exchange method, electrodialysis membrane separation method, etc. are used, and certain progress has been made. However, no production technology completely deviates from the methanol alcohol precipitation method. The only glycine can be obtained, and ammonium chloride is dissolved in the mother liquor and discharged. By concentrating the mother liquor, only agricultural ammonium chloride can be obtained, and the processing of the mother liquor is complicated, which severely restricts the expansion of the production scale.
Glycine is a fine organic chemical product with broad development prospects, and its application fields are constantly expanding. The production of glycine in many countries has eliminated the process technology of the chloroacetic acid ammonolysis method. The main production technologies used are the Strecker and Hydantion methods with hydrocyanic acid and hydroxyacetonitrile as raw materials. Through continuous updates and improvement of process technology, product yield and product quality have been greatly improved. There is also a trend of using biotechnology to synthesize glycine from glycine nitrile, focusing on the application of high and new technology such as catalysis, radiation, and biosynthesis to the research of glycine synthesis technology, and certain progress has been made.
The production of glycine in China currently generally adopts the chloroacetic acid ammonolysis process technology. Since its industrialization in 1969, although it has carried out many technological improvement studies, the yield of glycine has been increased from 70% at the beginning to more than 85% at present, and the content of glycine has increased from 95% to 98.5%. The key indicator chloride content is still as high as 0.06%-0.5%. Due to the low purity and many impurities of the obtained product, which cannot meet the requirements of the food and pharmaceutical industries, the process technology is mainly used for the production of industrial-grade glycine.
3 Development trend of glycine production technology
Today, when people’s awareness of environmental protection is increasing, achieving sustainable development has become a consensus of mankind. The mother liquor treatment in the process of producing glycine by the traditional chloroacetic acid ammonolysis method has become an important issue to be solved in the production technology of glycine. There are three main difficulties in extracting ammonium chloride from the mother liquor for the production of glycine: ①The sublimation of ammonium chloride during the evaporation of the mother liquor and the decomposition of the catalyst urotropine lead to secondary pollution due to substandard discharge of condensate; ②High energy consumption; ③ Strong corrosion. It is economically unreasonable to process the mother liquor to recover ammonium chloride through evaporation. Therefore, various manufacturers are studying to solve this problem, but there is no feasible plan, which makes the pollution problem unsolved for a long time. The problem of pollution directly affects the vitality of the process technology and also determines the future of the process.
To maintain the unique market competitive advantage of the chloroacetic acid ammonolysis process technology for the production of glycine, it is necessary to improve the production process from the following aspects: ① Research and develop high-purity chloroacetic acid production technology suitable for the domestic market, and reduce the side effects in the production of chloroacetic acid. The effect of high product content on the subsequent ammonolysis reaction; ②Using high-purity chloroacetic acid liquid to directly carry out the amination reaction and adopting a continuous process to reduce the consumption of catalyst; ③Using more efficient subsequent separation and refining technology to improve the content and quality of glycine; ④ Research and develop economically feasible by-product processing technology.
In the past ten years, China has done a lot of research work on glycine synthesis technologies such as catalytic dehydrogenation, biosynthesis, and radiation synthesis. However, they are still at the theoretical and experimental stage and are far from being put into industrial production. Degree. Therefore, Chinese scientific research institutions and enterprises must significantly increase product yield, improve product quality, reduce raw material consumption and energy consumption, and eliminate or reduce the by-product ammonium chloride, in addition to the clean production technology transformation of the traditional chloroacetic acid ammonolysis method. This should be the direction of the technological transformation of China’s existing glycine production equipment.
4 Conclusion
From the viewpoint of green chemical clean production, a reasonable production process route should have strong economic competitiveness. China’s glycine production enterprises and some universities and research institutes should strengthen cooperation, learn from foreign research ideas, increase R&D investment from the perspective of participating in international competition and sustainable development, and continue to innovate in glycine production technology. The improvement of process technology can reduce the production cost of glycine and eliminate environmental pollution, obtain good economic and social benefits, and improve the competitiveness of glycine products in the international market.
