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- Title
Process hazard and thermal risk evaluation of m-xylene nitration with mixed acid.
- Authors
Yao, Hang; Ni, Lei; Liu, Yinshan; Fu, Gang; Jiang, Juncheng; Cheng, Zhen; Ni, Yuqing; Chen, Zhiquan
- Abstract
The exothermic pattern of m-xylene nitration with mixed acid in semi-batch mode was studied by reaction calorimetry. Adiabatic temperature rise (Δ T ad) and reaction enthalpy (∆ H) were obtained to identify the thermal hazard. Process conditions including stirring rate, reaction temperature and strength of mixed acid were studied to optimize the reaction. Optimal yield (95.5%) was reached under the conditions of sufficient stirring rate, 70% strength of mixed acid and reaction temperature of 40 °C. Meanwhile, the thermal stability of nitration products was investigated by differential scanning calorimetry (DSC) and accelerating rate calorimetry (ARC). Pyrolysis kinetic parameters were calculated under non-isothermal and adiabatic conditions. Furthermore, the maximum temperature of the runaway system for synthesis reaction (MTSR) was determined to analyze the reaction hazard. The thermal risk of nitration of m-xylene was also assessed by the risk matrix and Stoessel criticality diagram. In addition, the nitration mechanism of m-xylene was presented. The active site for the electrophilic reaction of m-xylene was predicted via theoretical approach which was in consistent with the selectivity obtained by the experiment. These findings provide guidance for the safe operation of m-xylene nitration and can be used for further scale-up.
- Subjects
NITRATION; RISK assessment; DIFFERENTIAL scanning calorimetry; HEAT of reaction; ADIABATIC temperature; THERMAL stability
- Publication
Process Safety & Environmental Protection: Transactions of the Institution of Chemical Engineers Part B, 2023, Vol 175, p238
- ISSN
0957-5820
- Publication type
Article
- DOI
10.1016/j.psep.2023.05.028