Research on the Risk of Thermal Runaway in the Industrial Process of Styrene Solution Polymerization

Polymerization reactions are exothermic processes that are often accompanied by viscosity changes, and they can pose hazards due to thermal runaway. This paper describes an investigation of the potential for thermal runaway in the industrial process of styrene solution polymerization, in which particular focus was devoted to the effects of the monomer concentration and the solvent. As the monomer concentration increased from 20.0 to 50.0 wt %, the heat of reaction Q(r) and the adiabatic temperature rise Delta T-ad increased in a linear manner from 19.0 +/- 0.2 to 58.1 +/- 0.6 kJ and 21.7 +/- 0.1 to 64.8 +/- 0.6 K, respectively, and the maximum temperature attained by the synthesis reaction ( MTSR) was also increased from 86.1 +/- 0.2 to 101.5 +/- 0.2 degrees C. In addition, the molecular weight distribution of polystyrene was around 1.9, and the distribution was broad. The risk of a potential runaway reaction was evaluated using the Stoessel assessment criteria and Zurich Hazard Analysis. The criticality of runaway polymerization remained constant with increasing concentration, and class 1 risk was observed. However, the severity of a potential runaway reaction was increased from negligible to medium class. It was found that the solvent had an important effect on the risk of thermal runaway during polymerization. The criticality of the high-boiling solvents toluene and cyclohexanone used in this work was class 1, while that of the low-boiling solvent ethyl acetate was class 3. This work provides valuable insight that can help to control thermal risk in the chemical industry.