Tentative exploration on water-promoted catalytic ozonation of Cl-VOCs and feasibility of application in complex flue gas over monolithic cobalt catalyst

Abstract

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. O 3 decomposition and Cl-VOCs ozonation occur simultaneously but the active radicals and intermediates from O 3 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 o 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 CH 2 Cl 2 conversion and almost 10%~25% improvement in mineralization rate. NO ozonation generates NO 3 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 O 3 /CH 2 Cl 2 of 12.5 at 50 o C. SO 2 and Ca cause severe deactivation on catalytic ozonation that requires higher O 3 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. • The monolithic catalyst is firstly used for catalytic ozonation system. • CoO x @Ni attains 90% DCM conversion with O 3 /DCM=6.0 under humid condition at 120 o C. • Water vapor enhances the performance of Cl-VOCs catalytic ozonation over CoO x @Ni. • Simultaneous removal of NO and Cl-VOCs can be achieved during catalytic ozonation.