Highly Efficient Purification of Styrene Exhaust Gas by Aqueous Oxidation-Absorption and Kinetic Study

Abstract

Organic solvents (e. g., mineral oil) are frequently employed as absorbents to purify VOCs, but their absorption efficiency and saturation capacity are limited and the high viscosity causes uneven liquid distribution and increased pressure drop, restricting their industrial applications. To surmount these limitations, this work develops the use of water as an absorbent combined with aqueous-phase chemical oxidation absorption to remove low-concentration styrene from exhaust gases. The effects of key parameters, including oxidant type, styrene concentration, and liquid-phase pH on the oxidation absorption performance were systematically investigated. Experimental results indicate that KMnO₄ outperforms K₂FeO₄ and NaClO₂ in enhancing styrene absorption, KMnO₄ can interact with the C=C bonds in styrene to form cyclic permanganate ester intermediate with a lower activation energy, thereby facilitating the oxidation process. Under the oxidation action of KMnO₄, styrene is rapidly oxidized into water-soluble species, primarily benzaldehyde, significantly improving the absorption ability of water for styrene, with a purification efficiency exceeding 95%. In weakly alkaline conditions of pH 9, the saturation absorption capacity of KMnO₄ for styrene reaches 308.6 mg/g. A detailed reaction pathway for the KMnO₄-mediated oxidation of styrene under various pH conditions is proposed and further validated through quantum chemical calculations. Additionally, kinetic studies reveal that the oxidation of styrene by KMnO₄ follows a second-order reaction model, with an apparent activation energy of 15.205 kJ/mol. These findings provide valuable insights into the development of efficient VOCs purification technologies for industrial applications.