Efficient synthesis of dodecylbenzene sulfonic acid in microreaction systems

Dodecylbenzene sulfonic acid (DBSA) is one of the significant anionic surfactants that can be used as a cleaning agent in the daily chemical industry or chemical oil-displacing agents in tertiary oil recovery. The sulfonation of dodecylbenzene (DDB) is the predominant route to fabricate DBSA. In this paper, we introduce a continuous process and a cyclic process in microreactors to optimize the routine of DDB sulfonation using dilute liquid sulfur trioxide and compare the two processes systematically. By optimizing the flow rate, the SO3/DDB molar ratio, the sulfonation temperature in the microreactor and the aging step, all the physicochemical indexes of product in continuous process can meet the standard of top grade with sulfonic acid contents up to 97 wt.% and the free oil and sulfuric acid contents down to 1.0 wt.%. Furthermore, the residence time of the reactants in the microreactor can be as low as 2.5 s, and the aging stage can be completed in less than one hour, which is a lot faster than the industrial process. In summary, we have optimized the whole process of the DBSA production so that it can have great potential in application to actual industrial production.