Tuning smaller Co3O4 nanoparticles onto HZSM-5 zeolite via complexing agents for boosting toluene oxidation performance

Tunable smaller Co3O4 nanoparticles onto HZSM-5 zeolites were prepared by the addition of various rich-hydroxyl complexing agents. The physicochemical properties including the crystalline size, surface dispersion, reducibility and acidity of Co3O4 active component and the catalytic performance for toluene oxidation were extensively investigated by numerous characterization techniques and catalytic experiments. It was found that the smaller particle size and the better dispersion of Co3O4 nanoparticles on HZSM-5 zeolite after complexing agents addition lead to remarkable reducibility enhancement and higher abundance of surface acidity, which were proved to be the key factors for the elevation of toluene oxidation activity. Among all, the catalyst with beta-cyclodextrin as the complexing agent (designated as Co3O4/HZSM-5/beta-CD) exhibited not only the optimum catalytic activity, but also high catalytic stability under dry condition and good regeneration capacity under humid conditions. Based on the results of reaction order determination, a first-order reaction rate equation with respect to toluene concentration was derived under rich-oxygen atmospheres, which was in good accordance with the conclusion in previous research.