Sulfonation of 1,4-diaminoanthraquinone leuco by chlorosulfonic acid: Kinetics and process intensification

Abstract

The work herein employed a rotating packed bed (RPB) to intensify the sulfonation process of 1,4-diaminoanthraquinone leuco (DL) in an attempt to improve the yield of the product 1,4-diaminoanthraquinone-2-sulfonic acid (DSA). First, the effects of operating conditions in a stirred tank reactor (STR), including stirring speed, chlorosulfonic acid/DL molar ratio (η), solvent/DL mass ratio (ζ), reaction temperature and dropping speed of chlorosulfonic acid, on the yield of DSA were investigated. The yield of DSA can reach 87.34% under the optimal operating conditions: stirring speed of 500 r·min−1, η of 4.5, ζ of 7, reaction temperature of 150 °C, dropping speed of 0.61 ml·min−1. In addition, the kinetics of the sulfonation process via the shrinking core model revealed that the reaction is controlled by diffusion via a product layer under the reaction temperature of 140 °C. Furthermore, the RPB was employed to intensify the mass transfer between liquid and solid phases during the sulfonation reaction process. The results showed that the DSA yield of 92.69% obtained by RPB was 5.35% higher than that by STR, indicating that RPB can significantly intensify the mass transfer in the liquid–solid phase sulfonation reaction process.