Gaseous CO and toluene co-oxidation over monolithic core-shell CoO-based hetero-structured catalysts

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2019-07, Vol.7 (27), p.16197-1621
• Main Authors: Mo, Shengpeng, Zhang, Qi, Sun, Yuhai, Zhang, Mingyuan, Li, Jiaqi, Ren, Quanming, Fu, Mingli, Wu, Junliang, Chen, Limin, Ye, Daiqi
• Format: Article
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c9ta03750k

The inhibiting effects of using platinum group metal (PGM) catalysts are universal problems for the co-oxidation of CO and hydrocarbons (HCs), resulting in a higher temperature to handle CO and HCs pollutants. Herein, this work focuses on designing a series of Co 3 O 4 -based catalysts whose catalytic activities in the individual oxidation and co-oxidation of CO and toluene are comparable to Pt-based catalysts. The catalytic behaviors of CO and toluene oxidation over Pt/Al 2 O 3 are mutually inhibited in the presence of CO and toluene, in which CO oxidation could improve catalytic toluene degradation over Co 3 O 4 -based catalysts, as its CO oxidation is negatively affected by toluene oxidation. In addition, under the coexistence of CO and toluene, the light-off temperature of toluene oxidation on both Co 3 O 4 -based and Pt-based catalysts consistently followed that of CO oxidation. Among all monolithic core-shell Co 3 O 4 -based catalysts, these catalysts introduced to different elements (Co, Mn and Cu) showed the distinct promotion of CO and toluene oxidation, and the Co 3 O 4 @Co 3 O 4 catalyst exhibited the most outstanding catalytic performances for the individual oxidation and co-oxidation of CO and toluene. In addition, the physicochemical properties of core-shell hetero-structured catalysts are further characterized in detail by XRD, BET, SEM, TEM, H 2 -TPR, XPS, O 2 -TPD and Raman spectrometry. It was confirmed that the excellent performance of the Co 3 O 4 @Co 3 O 4 catalyst is mainly associated with the surface area, surface oxygen vacancies and low-temperature reducibility, whose prominent oxygen vacancy and low-temperature reducibility are induced by the synergistic effect of different Co 3 O 4 structures. In situ DRIFT spectroscopy confirmed that bidentate carbonate species and benzoate species were considered as a reaction intermediate species in CO and toluene oxidation, respectively. Moreover, there is a competitive adsorption-reaction on the active sites of Co 3 O 4 -based catalysts for CO and toluene, but the reaction mechanism of CO/toluene oxidation may be mutually independent under the coexistence of CO and toluene. Gaseous CO co-existence could improve catalytic toluene oxidation over Co 3 O 4 -based catalysts, and the reaction mechanism on the CO/toluene oxidation may be mutually independent in the presence of both CO and toluene.