Industrial production process comparison of saccharin sodium
Product yield
When the toluene method uses toluene as a raw material for chlorosulfonation with chlorosulfonic acid, nearly half of the by-products of p-toluenesulfonyl chloride are formed, and the yield of o-toluenesulfonyl chloride to o-toluenesulfonamide is only 75-78%. Therefore, The total yield of sodium saccharin produced by the toluene method is less than 40%. Although there are various types of side reactions in the production process of the phthalic anhydride method, the total yield can reach more than 80%, which is more than double the yield of the toluene method. Therefore, the phthalic anhydride method is better in terms of yield. . To
product quality
The intermediate product o-toluene sulfonamide is produced during the production of sodium saccharin by the toluene method. Insoluble saccharin is formed after oxidation and acid precipitation of the o-toluene sulfonamide. In the actual production process, the oxidation is often incomplete, and the unreacted o-toluene cannot be completely removed during separation. Sulfonamide is separated, and o-toluene sulfonamide is a carcinogen. In addition, p-toluene sulfonamide is also present in the product, which has a great impact on product quality. Countries and regions such as Europe and the United States have strict requirements on the content of o (or p) toluene sulfonamide in saccharin sodium, which is difficult to control. There is no similar product in the production of phthalic anhydride method, and the product quality is better than that of the toluene method.
Pollution and governance
There are hydrogen chloride tail gas, waste acid water containing chlorosulfonic acid, sulfuric acid or hydrochloric acid, waste water containing ammonia, ammonium salt, waste alkali water, activated carbon waste residue containing o-toluenesulfonamide, waste residue of manganese dioxide, etc. in the toluene production process. Except that the hydrogen chloride tail gas can be absorbed into hydrochloric acid by water, and manganese dioxide can be treated as a by-product, the others are not easy to recover or treat.
The wastes in the production process of phthalic anhydride include: alkali mother liquor wastewater, waste acid water containing copper sulfate, waste acid water containing insoluble saccharin, ammonia tail gas, nitrogen dioxide tail gas, sulfur dioxide tail gas, chlorine tail gas, activated carbon waste residue, steamed toluene waste residue, etc. The amount of process wastewater is twice that of the toluene method. The alkali mother liquor wastewater can firstly recover methanol, and then react with waste acid water containing copper sulfate to recover anthranilic acid. The wastewater containing insoluble saccharin is precipitated to recover the insoluble saccharin, and then distilled to recover ammonia and methanol. The exhaust gas discharged is relatively toxic, and the exhaust gas recovery is a key point. Sodium sulfite, sodium hypochlorite, sodium nitrite and ammonia can be recovered. Activated carbon waste residue can be reused; steamed toluene waste residue can be used as auxiliary materials for waterproof building materials. The recovered product can be used as a raw material or sold as a product.