The production of antioxidant RD usually uses aniline and acetone as raw materials and hydrochloric acid as a catalyst. The finished product is obtained through unit operations such as salt formation, polycondensation, neutralization, distillation, granulation and packaging. At present, the main methods for the production of antioxidants RD at home and abroad are “one-step” process and “two-step” process.
The “two-step method” is that the monomer TMDQ (2,2,4-trimethyl-1,2-dihydroquinoline) is first formed by the condensation reaction of aniline and acetone under the action of an acidic catalyst. Under the action of an acidic catalyst, moderate polymerization is performed to obtain an antioxidant RD product. When the “two-step method” is used for production, RD monomers are not in contact with raw materials such as aniline and acetone during polymerization, so they have fewer side reactions and good product quality. The dimer content in the polymer of the antioxidant RD product produced by the “two-step method” can reach about 50%. The condensation catalysts used include p-toluenesulfonic acid, BF3, polyfluorinated sulfonic acid resins, aniline hydrochloride, SiCl4, etc., and the polymerization catalysts are mostly hydrochloric acid, and also use polybasic fatty acids such as oxalic acid and succinic acid.
The “one-step method” is that the condensation polymerization reaction of aniline and acetone is carried out in the same reactor, and an RD-proof product can be obtained in one step. The “one-step method” simplifies the process, with less equipment investment, high yield, and low consumption, so the cost is low and the product has strong competitiveness. Antioxidant RD with dimer content of 45% -48% can also be obtained by using appropriate process conditions and catalysts. The catalysts used are p-toluenesulfonic acid, CuCl2, concentrated hydrochloric acid, BF3 and the like. Ketoamine molar ratio is generally controlled to 1.7-2.4: 1.