P-nitrotoluene-2-sulfonic acid continuous synthesis method

Abstract

Disclosed is a p-nitrotoluene-2-sulfonic acid continuous synthesis method. The p-nitrotoluene-2-sulfonic acid continuous synthesis method comprises melting or dissolving p-nitrotoluene in organic solvent or inorganic solvent, and inletting the melt of solution together with sulfur trioxide mixed gas into a film sulfonation reactor for sulfonation reaction, filtering liquid reaction products containing the inorganic solvent to remove the inorganic solvent and then feeding the reaction products into an ageing tank, or directly feeding the solvent-free or organic solvent-containing liquid reaction products into the ageing tank for stirred ageing; and performing hydrolysis by adding in deionized water to obtain hydrolyzed products, which, if containing no organic solvent, are p-nitrotoluene-2-sulfonic acid, else, performing extraction by adding in deionized water for dissolution in aqueous phase to obtain the p-nitrotoluene-2-sulfonic acid. The p-nitrotoluene-2-sulfonic acid continuous synthesis method has the advantages of being low in production cost, free from producing waste acid, high in safety performance and capable of achieving continuous production.

Description

technical field [0001] The invention relates to a continuous synthesis method of p-nitrotoluene-o-sulfonic acid. Background technique [0002] p-Nitrotoluene-2-sulfonic acid is also known as 4-nitrotoluene-2-sulfonic acid, referred to as NTS acid, and its CAS registration number is 121-03-9. As a very important dye intermediate, its main uses are as follows: 1) After oxidation to obtain 4,4'-dinitrostilbene-2,2'-disulfonic acid (DNS acid), and then reduced to obtain 4, 4'-diaminostilbene-2,2'-disulfonic acid (DSD acid), or 4-amino-4'-nitrostilbene-2,2'-disulfonic acid (ANSD acid);2 ) as a raw material to synthesize a series of monotriazole stilbene type optical brighteners. [0003] At present, the synthesis process route of p-nitrotoluene o-sulfonic acid at home and abroad is obtained by sulfonating p-nitrotoluene with sulfonating agents such as oleum, chlorosulfonic acid or sulfur trioxide. For example, the patent CN 1762992A discloses a sulfonating agent using 20% ​​ol...

AI Technical Summary

Problems solved by technology

However, it does not take into account that as the reaction progresses, every molecule of SO consumed 3 A molecule of water will be produced, and the sulfuric acid in the system will be gradually diluted, resulting in the continuous production of waste sulfuric acid. In the industrial production of fixed output, the accumulated waste sulfuric acid will still become a burden on the enterprise

Secondly, 50-65% of the fuming sulfuric acid used in the production is extremely unstable, highly corrosive and dangerous chemicals controlled by the state. It is usually solid in cold conditions, difficult to store, and high in transportation costs.

In addition, the production is carried out in a reactor, and the reaction using oleum requires uninterrupted stirring, which not only consumes a lot of energy, but also wastes a lot of time, and each reactor needs to be discharged after the reaction is completed, so it cannot be continuously produced.

Therefore, regardless of economic cost or environmental protection pressure, the current sulfuric acid sulfonation and oleum sulfonation cannot meet the requirements of large-scale production.