Tentative exploration on water-promoted catalytic ozonation of Cl-VOCs and feasibility of application in complex flue gas over monolithic cobalt catalyst
2023
Xiang, Li | Zhang, Luyang | Shao, Jiaming | Lin, Fawei | Wang, Zhihua | Yan, Beibei | Chen, Guanyi
It is still challenge to avoid Cl poisoning and achieve efficient elimination of Cl-VOCs at low temperature. This paper tentatively explored water-promoted catalytic ozonation of Cl-VOCs and feasibility of application in complex flue gas over monolithic cobalt catalyst. O₃ decomposition and Cl-VOCs ozonation occur simultaneously but the active radicals and intermediates from O₃ decomposition and Cl-VOCs ozonation have competitive effects on oxygen vacancies. Most interestingly, presence of water vapor and NO, as well as lowering temperature to 50 °C further promote catalytic ozonation of Cl-VOCs. Moisture vapor facilitates desorption of surficial Cl species and deep oxidation by washing effect and provision of additional H source to attain higher conversion and less byproducts. Especially, 1 vol% water vapor attains ∼10% elevation in CH₂Cl₂ conversion and almost 10∼25% improvement in mineralization rate. NO ozonation generates NO₃ related radicals with strong oxidability to enhance Cl-VOCs conversion and inhibit polychlorinated byproducts formation. Lower temperature promotes adsorption of the above-mentioned active radicals and intermediates to prolong the contact time, thus attaining higher conversion, ca. 100% conversion with O₃/CH₂Cl₂ of 12.5 at 50 °C. SO₂ and Ca cause severe deactivation on catalytic ozonation that requires higher O₃ input, which should be attributed to the occupation of active sites and attenuation of acidity. Above all, this paper reports an effective and practical approach for Cl-VOCs elimination in flue gas with potential to simultaneous remove NO.
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