Activity comparison of monolithic Cu-Co-Ce/TiO2/CH catalysts with noble metal catalysts in catalytic combustion of chlorobenzene

To eliminate the environmentally hazardous effect of chlorinated volatile organic compounds (CVOCs) and verify the feasibility of replacing noble metal catalysts with cobalt-based catalysts, monolithic Cu-Co-Ce/TiO 2 /cordierite honeycomb (CH) catalysts were prepared by a sol-gel/impregnation combined method and applied in the catalytic combustion of chlorobenzene, compared with commercial noble metal catalysts. The research suggested that Ce loading had an optimal amount, and Cu-Co 0.86 -Ce 0.54 /TiO 2 /CH catalyst exhibited the highest catalytic activity among four Cu-Co-Ce/TiO 2 /CH catalysts. Chlorobenzene was completely removed at 330℃ and mineralized at 400℃ under the conditions of an initial chlorobenzene concentration (C 0 ) of 1200 mg m −3 and gas hourly space velocity (GHSV) of 5000 h −1 . Compared with three noble metal catalysts, the Cu-Co 0.86 -Ce 0.54 /TiO 2 /CH catalyst had the highest catalytic ability at low C 0 and GHSV; however, its catalytic capacity was lower than that of noble metal catalyst C and higher than noble metal catalysts A and B at high values of C 0 (2000 m −3 ) and GHSV (20000 h −1 ). It is speculated that abundant active particles with different structures on the Cu-Co 0.86 -Ce 0.54 /TiO 2 /CH catalyst’s surface induce the lowest light-off temperature for chlorobenzene oxidation; however, their different catalytic activities also induce intermediate products that compete with chlorobenzene for the active sites, which decreases the catalytic activity of the catalyst, especially at high GHSV. The Cu-Co 0.86 -Ce 0.54 /TiO 2 /CH catalyst exhibited good stability, water resistance, and excellent anti-chlorine-poisoning capacity under two different conditions, confirming the feasibility of replacing noble metal catalysts at the relatively low space velocities. This research further identified the key mechanism behind which is the oxygen vacancies, the acid sites, and the electron transfers among Cu 2+ /Cu + , Co 3+ /Co 2+ , and Ce 4+ /Ce 3+ that promoted the adsorption, activation, and transformation of gaseous oxygen and chlorobenzene. Therefore, chlorobenzene is adsorbed and oxidized onto the active sites of the Cu-Co 0.86 -Ce 0.54 /TiO 2 /CH catalyst by both O ads and O latt, which follows the L-H mechanism and the MvK mechanism, respectively. For the noble metal catalyst C, both the E-R mechanism and the L-H mechanism could coexist in chlorobenzene degradation. This research establishes a theoretical basis for the commercial application of low-cost cobalt-based catalysts to effectively lessen the hazardous effects of CVOCs on the ecosystem and human health.