Enhancing the anti-K poisoning performance of Co3O4 catalyst for toluene oxidation by modifying MnOx

A series of cobalt-based catalysts (Co 3 O 4 , Mn/Co 3 O 4 , K-Co 3 O 4, and K-Mn/Co 3 O 4 ) were prepared for toluene catalytic combustion and anti-K poisoning experiments. Co 3 O 4 catalyst has exhibited good performance in toluene oxidation , but it has poor anti-K poisoning performance. The Mn/Co 3 O 4 catalyst has shown excellent low-temperature catalytic activity , good resistance to K poisoning at T 90 of 226 °C, and achieved a complete toluene conversion at about 235 °C; the activity after the addition of K slightly reduced at T 90 of 237 °C. A series of characterizations indicated that adding Mn can effectively promote the Co 2+ ↔Co 3+ cycle, increase the Co 3+ content on the catalyst surface, and enhance the redox performance of the catalyst. On the other hand, MnO x intercepts K species and generates Mn-O-K, blocking most of the poisonous effects of K on cobalt oxide , thereby protecting the active species (Co 3+ and surface-adsorbed oxygen) and acidic sites on the Co 3 O 4 surface. Finally, GC-MS and in-situ infrared characterization were adopted to investigate the reaction mechanism of the catalysts. Two reaction paths of the Co 3 O 4 catalyst may co-occur. Still, the reaction path of the Mn/Co 3 O 4 catalyst is relatively simple; that is, the chemically adsorbed toluene molecules are oxidized through surface-active oxygen, after which various intermediate by-products are formed successively. Finally, they are completely degraded into CO 2 .