Compatibility Study between 50% H2O2/H2SO4 Solution and Some Common Organic Solvents

In this article, a mixture of sulfuric acid and 50% hydrogen peroxide solution was used to produce Caro’s acid, which serves as an oxidant frequently encountered in the fine chemical industry. The chemical compatibility between 50% H₂O₂/H₂SO₄ and organic solvents is an important safety issue. The compatibility of 50% H₂O₂/H₂SO₄ and several organic solvents, including ethanol, acetonitrile, ethyl acetate, DMF, dichloroethane, DMSO, ether, and toluene, was studied by reaction calorimetry and thermal analysis techniques. It was found that the first five solvents presented good compatibility with 50% H₂O₂/H₂SO₄. DSC tests indicated that these five solvents almost did not react with 50% H₂O₂/H₂SO₄ before the onset decomposition temperature of 50% H₂O₂/H₂SO₄ (∼93.3 °C). RADEX tests showed that the reactions of 50% H₂O₂/H₂SO₄ with these solvents released heats from 800 to 1100 J g^–1, and the pressure effect was obvious for these mixtures. In contrast, the last three solvents, namely, DMSO, ether, and toluene, were incompatible with 50% H₂O₂/H₂SO₄, exhibiting a significant exothermic signal at lower temperatures. Most interestingly, the mixture of DMSO and 50% H₂O₂/H₂SO₄ presented a thermal runaway phenomenon below 40 °C. The causes of this thermal runaway incident were confirmed to be the oxidation of DMSO by Caro’s acid. Reaction calorimetry tests also indicated that the oxidation rate of DMSO was fast even at 40 °C, and the adiabatic temperature rise for the oxidation of DMSO was higher than 400 K.