Does anyone know the production process for glycine?

Regarding the production process of glycine, the following information is provided for the original poster’s reference. According to literature reports, there are many production routes for glycine. The main industrialized and industrially promising processes currently include the ammonolysis of chloroacetic acid, the Strecker method, the synthesis of glycine via hydrocyanic acid, and biosynthesis methods. 1. Ammonolysis of chloroacetic acid: Depending on the raw materials used, this method can be further divided into the following processes: (1) Synthesis in an aqueous or alcoholic phase using urotropine, chloroacetic acid, and ammonia water (either gaseous ammonia or liquid ammonia) ； (2) In the aqueous phase, it is synthesized using ammonium carbonate or carbamamide, chloroacetic acid, and ammonia water as raw materials. Currently, the former method is primarily used in domestic production, with a yield of around 70%, while the latter has a lower yield (about 42%), which is why it is rarely used in industrial production. Since a large amount of urethane is consumed in the synthesis of glycine in an aqueous medium, and urethane is expensive and cannot be recovered, the cost remains high. Using an alcoholic solution instead of an aqueous one reduces the amount of urethane used, thereby lowering the production costs. Therefore, the alcohol-phase method is currently widely used in China for the synthesis of glycine. The advantages of the ammonolysis method for chloroacetic acid are easy availability of raw materials, a simple synthesis process, low requirements for equipment, ease of operation, and virtually no environmental pollution. The disadvantages include a longer reaction time, difficulty in removing by-products such as ammonium chloride and other inorganic salts, poor product quality, high refining costs. Urotropine, which is used as a catalyst, cannot be recovered and reused, resulting in significant waste of raw materials and increased production costs. Domestic glycine manufacturers and some research institutions have carried out extensive research on the process of synthesizing glycine using chloroacetic acid, with the aim of optimizing reaction conditions to reduce production costs and improve product quality, and have made certain progress in this regard. 2. Strecker method: The reaction process in the Strecker method involves using formaldehyde, sodium cyanide, and ammonium chloride as raw materials; an alcoholysis reaction takes place in the presence of sulfuric acid, followed by hydrolysis with barium hydroxide to yield glycine. The product is filtered, and ethanol is added in the presence of sulfuric acid to effect decomposition, yielding ammonioacetonitrile sulfate. The above product is decomposed with barium hydroxide to yield barium aminoacetate; thereafter, a quantitative amount of sulfuric acid is added to precipitate the barium, and the filtrate is concentrated and allowed to cool, resulting in the precipitation of glycine crystals. This process route is lengthy; the raw material NaCN is highly toxic, the desalination step in the reaction is complex, and the operating conditions are quite stringent. Its advantages are easy refinement, low cost, and suitability for large-scale industrial production. 3. A new process for synthesizing glycine using hydrocyanic acid: This process replaces sodium cyanide with hydrocyanic acid, a cheap by-product of acrylonitrile, resulting in lower production costs. The United States, Japan, and other countries generally use this method to produce glycine. In the early 1990s, the Dalian Institute of Chemical Physics under the Chinese Academy of Sciences developed a process for synthesizing glycine using HCN as a raw material. This process uses hydrocyanic acid as the main raw material; during production, gaseous HCN or an HCN aqueous solution in any proportion can be used directly. Aldehydes can be used in the form of gases, solutions, or polymers; ammonia sources can include ammonia combined with carbon dioxide, or ammonium carbonate, ammonium bicarbonate, etc. The amounts of each reactant used are close to the theoretical values, allowing a product yield of 73%, with a product purity of over 95%. Due to the few reaction steps involved, this process results in a shortened manufacturing procedure, simplified operation steps, reduced equipment investment, and thus **lower production costs**. There is no need for waste treatment, scaling up production is easy, and the quality of the glycine produced is significantly better than that obtained using the chloroacetic acid method. 4. Biosynthetic method: The 21st century is the century of biosynthesis, and the biosynthetic production of glycine has become a very important and highly promising synthetic route. The United States, Japan, and Europe have been committed to research on the biosynthetic production of glycine for a long time. Previously, the industrialization of biosynthetic methods was limited by factors such as low enzyme activity, the high demand for microorganisms capable of synthesizing glycine, and low glycine yields. In the late 1980s, the Japanese company Mitsubishi added selected microorganism genera such as Aerobacter, Brevibacter, and Corynebacterium to a medium containing carbon sources, nitrogen sources, and inorganic nutrients for cultivation. Then, at temperatures of 25–45°C and a pH level of 4–9, these microorganisms were used to convert ethanolamine into glycine, which was subsequently obtained through concentrated neutralization and ion exchange processes. After entering the 1990s, new advances were made abroad in the technology for synthesizing glycine. Nitto Chemical Industry in Japan added the cultivated bacteria of genera such as Pseudocellulomonas, Caseibacter, and Alcaligenes to a matrix containing glycine amine at a concentration of 0.5% (by mass, on a dry weight basis). At 30°C and a pH of 7.9–8.1, the reaction was carried out for 45 hours, during which almost all of the glycine amine was hydrolyzed into glycine, achieving a conversion rate of 99%. Although the biological method is still in the research stage at present, it features high selectivity and no pollution, making it a synthetic route with great potential for development.