Reaction mechanism and thermal hazard assessment of diazotization for 2-aminonaphthalene-1,5-disulfonic acid (2-ANDSA)

This research comprehensively addresses the significant exothermic behavior and the associated thermal runaway risks in the semi-batch preparation of 2-aminonaphthalene-1,5-disulfonic acid (2-ANDSA) diazonium salt. By employing various thermal analysis techniques, including reaction calorimetry, differential scanning calorimetry (DSC), and accelerating rate calorimetry (ARC), the influences of reaction temperature and reagent feeding rates on product purity and thermal safety were systematically examined. The findings demonstrate that increased reaction temperatures accelerated reagent addition rates, and lowered solvent-to-reactant ratios markedly elevated the likelihood of thermal runaway incidents. Complementary density functional theory (DFT) calculations elucidated the detailed reaction mechanism, highlighted critical intermediate species, and clarified their thermodynamic profiles, thereby providing deeper insights into the thermal decomposition mechanism of the diazonium salt. Additionally, the combined application of the Risk Matrix and Stoessel Criticality Diagram methods facilitated a comprehensive thermal runaway risk assessment and identification of key operational safety parameters for process scale-up. These findings serve as a robust theoretical foundation and practical reference for effective thermal hazard management and safe production practices in processes involving high-risk aromatic diazonium salts.