The Effects of Acid and Hydrogen Peroxide Stabilizer on the Thermal Hazard of Adipic Acid Green Synthesis

The synthesis of adipic acid, which is formed by the reaction of cyclohexene oxidized by hydrogen peroxide (H₂O₂), is hazardous because of the highly exothermic nature of this reaction and H₂O₂ decomposition. The objective of this comprehensive study was to investigate and illustrate the effects of sulfuric acid (H₂SO₄) and H₂O₂ stabilizer (EDTA) on the thermal hazard of H₂O₂ decomposition and the green synthesis of adipic acid, which also provided a reference to reduce the risk of the reactions. Various calorimetry techniques were carried out to characterize the exothermic behavior of the reactions. An HPLC device was used to characterize the yield of adipic acid and the conversion rate of the raw materials, cyclohexene and H₂O₂. Meanwhile, density functional theory calculations were performed to understand the reaction mechanism and the associated energies of H₂O₂ decomposition catalyzed by sodium tungstate dihydrate (Na₂WO₄·2H₂O). Finally, combined with the calorimetry results, the risk of the adipic acid synthesis reaction was assessed using the intrinsic control index method (ITHI). The results show that the addition of H₂SO₄ and EDTA can reduce the exothermic heat of the H₂O₂ decomposition reaction and the green synthesis reaction of adipic acid. The yield of adipic acid was also increased. The hazard level of stage A was IV, and to remove more reaction heat, it was recommended to enhance the reflux cooling of stage A. The hazard level of stage B was I, which was very low and no further measures could be taken.