Mesoporous Co3O4 with large specific surface area derived from MCM-48 for catalytic oxidation of toluene

Abstract

As one of the most promising candidates for the catalytic combustion of volatile organic compounds, crystalline cobalt oxide is one of the most used and cost-effective catalyst. We present here a mesoporous Co3O4 catalyst with large specific surface area of 182.5 ​m2/g derived from MCM-48 with a specific surface area of 1470.9 ​m2/g, giving the T90 (the temperature required for achieving a toluene conversion of 90%) of 229 ​°C and the apparent activation energy (Ea) of 17.53 ​kJ/mol for the oxidation of toluene, both of which are much lower than the Co3O4 catalysts prepared by using SBA-15 and MCM-41 as hard template (T90 ​~ ​260 ​°C, Ea ​~ ​30 ​kJ/mol). Constant complete conversion of toluene over M48-Co3O4 was observed for 60 ​h, suggesting its superior stability for toluene combustion. Characterization results indicated the large specific surface area, higher Co3+/Co2+ ratio as well as abundant surface-active oxygen exposed for easy accessibility of reactant molecules contribute simultaneously to the good catalytic oxidation performance of M48-Co3O4. Particularly, 400 ​°C was viewed to be the optimal calcination temperature for keeping the mesoporous structures of catalyst as much as possible. The reaction intermediates of toluene oxidation over M48-Co3O4 were detected based on both GC-MS and in-situ DRIFTS, demonstrating the formation of the benzyl alcohol, benzaldehyde, benzoic acid, itaconic anhydride and maleic anhydride, acetone, and acetic acid, etc., as the main intermediates.