The mannitol is produced in a lot of ways, but most of the products are not pure, but a mixture of sorbitol and mannitol. If you want to get a single product, you have to go through purification.
1. Kelp Extraction Method The kelp extraction method is the main method for producing mannitol in China. It extracts mannitol from the wastewater after extracting iodine and sodium alginate from kelp, and extracts about 1 ton of mannitol per ten tons. The method obtains a single mannitol, which eliminates the separation step and has high purity, but the production cost of the method is high, and the source of the raw material is limited by region and season.
Process: 1 dry seaweed soaked and washed. 2 Adjust the pH with sodium hydroxide solution to precipitate the gel. 3 Acidify the supernatant with sulfuric acid to further remove the gel. 4 The supernatant is evaporated, desalted, crystallized, and centrifuged to obtain a crude mannitol product. 5 refined. 6 dried at about 90 ° C, that is, medicinal mannitol (99.08%).
2. Catalytic hydrogenation method using sucrose as raw material The aqueous solution of sucrose is acid-hydrolyzed into glucose and fructose to carry out catalytic hydrogenation reaction, glucose is converted into sorbitol, and fructose is converted into approximately equal amounts of sorbitol and mannitol. In the actual product, sorbitol accounts for 80% and mannitol accounts for 20%. Generally 5.2t white sugar can get 1t mannitol and co-produce sorbitol 4t.
The method uses abundant and cheap sucrose as raw material, has reliable process and high utilization rate of raw materials. Compared with kelp extraction method, the cost is low, the product quality is good, and the raw materials are not restricted by regional seasons.
Process: 1 heating and stirring to dissolve sucrose in water, pH adjustment with HCl, temperature control is 90 ~
105 ° C, kept for 1 ~ 2h, cooled for later use. 2 The syrup is purified by an anion/cation exchange resin and introduced into a hydrogenation reactor for catalytic hydrogenation. 3 Vacuum concentration, crystallization, and centrifugation to obtain crude mannitol, and the mother liquor is industrial sorbitol. 4 crude mannitol secondary crystallization, centrifugation, drying, pulverization, sieving, to obtain industrial grade mannitol.
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