Catalytic oxidation of low concentrations of vinyl chloride over spinel-type Co3O4 catalysts

In this study, a series of spinel-type Co3O4 catalysts were synthesized by different routes, including template (Co3O4-TP), sol–gel (Co3O4-SG), and precipitation method (Co3O4-CP), and their performance in the catalytic oxidation of vinyl chloride (VC) was investigated. The relationships between the catalysts’ physicochemical properties and performance in the catalytic oxidation of VC were investigated by X-ray diffraction, transmission electron microscopy, temperature-programmed reduction, ammonia temperature-programmed desorption, oxygen temperature-programmed desorption and X-ray photoelectron spectroscopy. The results showed that the catalytic activity of the catalysts decreased in the order Co3O4-TP > Co3O4-CP > Co3O4-SG, which was in a good agreement with the trends for the content of acid sites and oxygen vacancies. Notably, the Co3O4-TP catalyst showed the highest catalytic activity towards VC due to its low-temperature reducibility, larger number of adsorbed oxygen species, and higher oxygen mobility. Moreover, it was found that surface-adsorbed oxygen species were essential in the catalytic oxidation of VC. The VC conversion rate over Co3O4-TP calcined at 400 °C achieved 98% at 275 °C, with selectivities towards CO2 and HCl of 95.6 and 80.5%, respectively. In addition, only traces of chlorinated by-products were formed, and the conversion rate of low-concentration VC exceeded 96% after 60 h continuous reaction.