By optimizing process conditions and establishing a combined calorimetry–computational framework, the research provides both a theoretical foundation and practical guidance for improving chemical process safety.
The chemical industry relies heavily on diazotization reactions, which transform aromatic amines into highly reactive diazonium salts. While indispensable for producing a wide range of organic compounds, these reactions are notoriously hazardous. The heat release during diazotization can exceed −150 kJ/mol, and diazonium salts decompose violently at even slightly elevated temperatures, causing industrial accidents worldwide. Conventional safety controls—such as low-temperature semi-batch reactors—offer partial protection but often lead to poor mixing, side reactions, and yield losses. These challenges highlight the urgent need for integrated research approaches that can unravel reaction mechanisms while identifying practical strategies to minimize thermal hazards.
A study (DOI: 10.48130/emst-0025-0010) published in Emergency Management Science and Technology on 30 June 2025 by Juncheng Jiang’s team, Nanjing Tech University, optimizes process parameters and mitigates thermal runaway risks in 2-ANDSA diazonium salt synthesis, providing essential guidance for safer industrial production of high-risk diazotization reactions.
In this study, the researchers applied a systematic series of optimization experiments based on single-factor variable control to explore the synthesis of 2-ANDSA diazonium salt and its associated thermal hazards. Using two temperature control modes (Tr and Tj), they carefully varied and monitored reaction temperature, feed rate, molar ratios of raw materials, and stirring speed to ensure reliable data and minimize experimental error. The results revealed that reaction temperature had only a marginal effect on purity at low levels (0–10 °C), where values remained above 95%, but higher temperatures (20–30 °C) substantially increased heat release, molar enthalpy, and the maximum temperature of synthesis reaction (MTSR), raising the risk of thermal runaway. Feeding rate experiments showed that while lower rates (0.10–0.15 mL/min) maintained high purity and acceptable thermal parameters, higher rates caused sharp declines in purity and doubled heat release, underscoring the need for precise control. Similarly, optimizing the hydrochloric acid ratio improved product purity up to 96.8% at 2.6, but excessive acid content intensified exothermic reactions; thus, a balanced ratio of about 2.4 was deemed optimal for both yield and safety. Sodium nitrite ratios above 1.0 drastically elevated the maximum heat release rate despite little change in purity, highlighting the importance of keeping this parameter tightly controlled. Stirring rate analysis indicated that 400 rpm offered the best compromise between mixing efficiency, purity (97%), and safety, whereas very high rates promoted overheating and instability. Comparing Tr and Tj temperature control modes, the Tr approach achieved safer early-stage heat dissipation and lower MTSR values, suggesting it as the preferred option for industrial practice. Further safety assessments using differential scanning calorimetry (DSC), accelerating rate calorimetry (ARC), and kinetic analysis confirmed that 2-ANDSA diazonium salt decomposes at relatively low temperatures and poses significant gas-generating runaway risks if uncontrolled. Risk Matrix and Stoessel Criticality Diagram evaluations ultimately classified the optimized process as low-risk but stressed the importance of strict temperature management, careful feeding, and efficient cooling systems to ensure industrial-scale stability.
This research provides a roadmap for safe industrial production of high-risk diazonium salts. By integrating experimental calorimetry with theoretical modeling, the study not only improves the efficiency and selectivity of diazotization reactions but also ensures safer scale-up. The recommended parameters help manufacturers minimize accident risks while maintaining product quality, directly benefiting industries such as dye and pharmaceutical manufacturing.
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References
DOI
10.48130/emst-0025-0010
Original Source URL
https://doi.org/10.48130/emst-0025-0010
Funding Information
This work was supported by the National Natural Science Foundation of China (Grant Nos 52274209, 52334006), the Jiangsu Qing Lan Project, and the Jiangsu Association for Science and Technology Youth Talent Support Program.
About Emergency Management Science and Technology
Emergency Management Science and Technology (e-ISSN 2832-448X) is an open access journal of Nanjing Tech University and published by Maximum Academic Press. It is a medium for research in the science and technology of emergency management. Emergency Management Science and Technology publishes high-quality original research articles, reviews, case studies, short communications, editorials, letters, and perspectives from a wide variety of sources dealing with all aspects of the science and technology of emergency.