Introduction to Sorbitol & Vitamin C
Sorbitol is a kind of hexahydric alcohol. Because of its molecule contains six hydroxyl groups, can be dehydrated, oxidation, esterification, etherification and other chemical reactions, but also play a water-absorbing and moisturizing effect, widely used in food, medicine and chemical industry, tobacco and leather and other industries.
In the food industry, due to the low sweetness, low calorific value and excellent heat resistance, Sorbitol can be used for diabetics, obese patients, children’s sweeteners and additives. As a solid sorbitol absorbs heat when dissolved(Heat of solution at 25℃ -120.8J/g), there is a cooling sensation after eating. It is the upper class raw materials for making chewing gum gum candy. In recent years, sorbitol has long become the world’s food industry “new favorite”;
In daily chemical and light industry, Sorbitol replaces glycerin and propylene glycol as moisturizing excipient in toothpaste and cosmetics. It has the advantages of good moisturizing effect, high viscosity and low price. In China’s toothpaste industry, the amount of glycerol replaced by sorbitol has reached more than 90%.
In the pharmaceutical industry, the medicinal field of sorbitol continues to expand, and the pharmaceutical varieties synthesized with it as raw material are constantly being developed successfully, among which the production of vitamin C is the most prominent, with the dosage accounting for about nearly half of its total. Sorbitol is an important pharmaceutical intermediates and the main raw material for the synthesis of vitamin C. Vitamin C obtained from sorbitol by secondary fermentation and hydrochloric acid conversion can be used to prevent and treat scurvy and various infectious diseases and purpura disease.
Vitamin C as one of the vitamin varieties with the largest production and marketing scale in the world, it has a huge application amount in medicine, health care, food additives, etc. At present, the global demand for vitamin C is about 220,000 tons, China is the global production base of vitamin C, whose supply accounted for 70%. The downstream demand for vitamin C is mainly for residential consumers, showing a rigid demand performance, which effectively guarantees the slow and steady increase.
Besides, the production of one ton of vitamin C requires approximately 3.5 tons of sorbitol with a dry matter content of 50%.. From the perspective of global sorbitol market consumption, from 2016 to 2020, the global sorbitol market consumption has increased year by year, and the global sorbitol market consumption in 2020 has increased by 2.4%. In the future, due to the high cost-effectiveness of sorbitol, its market demand will continue to increase along with the development of the downstream market of food, medicine and daily chemicals, showing a steady growth trend.
Vitamin C production process
The most commonly used method for industrial synthesis of Vitamin C is the two-step fermentation process. This method utilizes biological air oxidation to first hydrogenate glucose into sorbitol, followed by fermentation to produce sorbitol, which is then further oxidized to glucuronic acid. The glucuronic acid is neutralized with potassium carbonate to obtain sodium glucuronate, which is processed through ion exchange, ground settling, secondary exchange, concentration, crystallization, and drying to produce glucuronic acid. The glucuronic acid undergoes esterification and conversion to form sodium ascorbate, which is then alkalinized, concentrated, and crystallized to obtain crude Vitamin C. The crude Vitamin C is dissolved, decolorized, cooled and crystallized, and vacuum-dried to produce high-quality Vitamin C.
It is worth noting that the quality of sorbitol has a significant impact on the production and yield of Vitamin C; therefore, high standards are set for the quality of sorbitol, with the typical requirement being a sorbitol content of 97% or higher.
Sorbitol Production Process
Industrially, the main methods for producing sorbitol include hydrogenation, electrochemical processes, and fermentation. In China, the traditional method for producing sorbitol is the hydrogenation of glucose. This process involves preparing a solution of glucose with a mass fraction of 50% to 55%, adding activated Raney nickel catalyst, and passing hydrogen gas to carry out the hydrogenation reaction until the residual sugar meets the required standards. The reaction mixture is then allowed to settle, and the supernatant is subjected to ion exchange, resulting in a sorbitol solution with a mass fraction of generally 50%. In this process, the separation of the catalyst is achieved through initial settling followed by precise separation, which not only addresses the issue of catalyst contamination of ion exchange resins but also allows for the recovery and reuse of spent catalyst or its sale as scrap metal.
The RaneCAT series of Raney nickel catalysts, independently developed by SUNCHEM, are suitable for the hydrogenation of aldehydes to alcohols in sugar molecules. Their high conversion rate and selectivity can reduce the content of raw sugar and mannitol, a by-product and isomer of sorbitol, leading to high-yield and high-purity sorbitol products. Additionally, the minimal metal residues in the reaction can be completely separated through ion exchange.
Our RaneCAT-8000 series of specialized catalysts for carbonyl hydrogenation have been successfully applied in the catalytic hydrogenation production of various food and pharmaceutical intermediates, earning a good reputation in industrial applications. These catalysts offer excellent cost-effectiveness, providing high activity, high selectivity, and high conversion rates, making them ideal “three-high” catalysts.