Study on the Ultrasonic-Enhanced Sulfonation Process of Tanshinone IIA

Abstract

This study has successfully developed a novel continuous-flow sulfonation process for tanshinone IIA based on ultrasonic intensification, providing a theoretical framework for the design and optimization of other ultrasonic-intensified complex reaction systems. Experimental results reveal that the enhancement of ultrasonic cavitation intensity by increasing power is not simply linear but is strongly governed by its interaction with the tube diameter. Specifically, the study demonstrates that the cavitation intensity at a tube diameter of 1.6 mm is significantly higher than that at 0.8 mm. Through systematic process optimization (a residence time of 2 min, a sulfonation temperature of 25 °C, and a molar ratio of SO3 to tanshinone IIA of 2), an optimal balance between mass transfer enhancement and side reaction suppression was successfully achieved under an ultrasonic power of 115 W and a tube diameter of 1.6 mm. Specifically, this optimal balance resulted in a high average sulfonation yield of 89.1%. Furthermore, the ultrasonic cavitation effect significantly modifies the product morphology through a dual fragmentation and suppression mechanism. It reduces both the characteristic particle sizes Dv(10) and Dv(90) of the aggregates by 3.4 times, thereby effectively alleviating the clogging issue in microchannel reactors.