Synthesis method of sulfamic acid

There are many methods to produce 1. sulfamic acid, such as hydroxylamine method with sulfur dioxide and hydroxylamine or acetone oxime as raw materials, ammoniation method with sulfurous acid or sulfate and liquid ammonia as raw materials, chlorosulfonation method with urea and chlorosulfonic acid as raw materials, fuming sulfuric acid method with urea, sulfur trioxide and sulfuric acid as raw materials, fuming sulfuric acid method and fuming sulfuric acid method (also called liquid phase method), and gas phase method in which liquid ammonia reacts with sulfur trioxide. There are two industrial processes at home and abroad: fuming sulfuric acid method and ammoniation method for directly synthesizing sulfur trioxide and ammonia. Urea and fuming sulfuric acid are sulfonated at 40-70℃ to produce sulfamic acid crude product, and then water is added for crystallization to obtain sulfamic acid finished product. Raw material consumption quota: 2000kg/ton of urea and 0/500kg/ton of fuming sulfuric acid.

2. There are two main synthetic methods: gas phase method and liquid phase method. The gas phase method has harsh operating conditions and high requirements for equipment materials. There are many by-products, and amino acids are easy to attach to the inner wall of the reactor and need to be cleaned frequently. The production cost is high. Its advantage is high product purity. Most manufacturers use the liquid phase method.

3. Adding excessive fuming sulfuric acid into the reaction kettle, stirring and cooling to 20-40 DEG C, and starting to add sulfuric acid and urea mixed in proportion. After the addition, the mixture was stirred at about 20.d egree. C. for 8 hours. Then gradually raise that temperature to 70-90 DEG C, steaming out sulfur trioxide, and cool and crystallizing. After solid-liquid sharing, crude sulfamic acid was obtained, which was recrystallized with water, dehydrated and dried to obtain high-purity refined sulfamic acid.

4. Aminosulfonic acid is an adduct of strong Lewis acid SO3 and strong Lewis base NH3. When preparing a small amount of high-purity sulfamic acid, high-purity SO3 can directly react with ammonia under completely anhydrous conditions. If the dosage is large, it can be prepared by the reaction of urea and oleum. Put the round-bottomed flask with mechanical stirring device into a flowing water bath, add 560g 100% sulfuric acid to it, and slowly add 100g urea into the sulfuric acid for several times (about 45 minutes) under strong stirring, taking care not to make the temperature exceed 40℃. Then add 309g fuming sulfuric acid (containing 65% free SO3), and let it stand at 42 ~ 45℃ for 65438±06h. The reaction mixture was filtered with a glass sand funnel, washed first with pure sulfuric acid, then with 50% sulfuric acid, and finally with cold methanol.

5. Heat 20% oleum to 30℃, slowly add urea at 60 ~ 65℃, keep the temperature for 3H after adding, then raise the temperature to 80 ~ 85℃, keep the temperature for 2h, after the reaction, cool it to 5℃, filter, centrifuge, dry the obtained crystal, then wash it with 5% ethanol, and recrystallize and refine it with distilled water to obtain pure sulfamic acid.