Studies On Preparation And Reaction Properties Of Cobalt Catalysts For Catalytic Combustion Of Toluene

Catalytic combustion technology is an effective way to oxidize volatile organic compounds?VOCs?into non-polluting CO₂ and H₂O.The primary problem is to design and develop catalysts with high activity and stability.In a supported catalyst,the interaction generated between the support itself and the active component enhances catalyst performance.Cobalt catalyst exhibits good catalytic activity due to its excellent low temperature reducing ability,high concentration of oxygen vacancies and electrophilic oxygen species.In order to further improve the activity of the cobalt catalyst,cobalt is supported on the support or other active components are supported on the cobalt catalyst,and the catalytic performance is enhanced by the synergy between cobalt and other components.Graphitic carbon nitride?g-C₃N₄?is considered to be an excellent catalyst support due to its low density,good thermal stability and rich surface chemical properties.In this paper,the g-C₃N₄ supported cobalt oxide catalyst was designed and developed,and it was applied to the catalytic combustion reaction of toluene.The effect of g-C₃N₄ on the catalytic combustion of toluene was investigated.On the other hand,based on the morphological effect of the catalyst,cobalt oxide nanorods were synthesized and used as a carrier to support the active metal Ag.The catalytic oxidation performance of the cobalt oxide nanorod-supported Ag catalyst was studied.The results of this work are as follows:?1?Thermal polymerization of guanidine hydrochloride to synthesize g-C₃N₄,and preparation of CoOx/g-C₃N₄ catalyst by impregnation method.For comparison,SBA-15,?-Al₂O₃,AC supported CoOx catalysts were prepared.Catalytic oxidation of toluene showed that the catalytic activity increased with the increase of CoOx loading,and the optimal catalytic activity was achieved when the loading was 10%.Compared with other supported CoOx catalysts,the10%CoOx/g-C₃N₄ catalyst also has the best catalytic activity,achieving complete conversion of toluene at 279°C,and excellent stability and recycling.?2?The highest catalytic activity of 10%CoOx/g-C₃N₄ catalyst is due to the existence of high surface Co³⁺content,high density surface adsorbed oxygen species,and reducibility of Co³⁺at low temperature.?3?Compared with other supports,carbon nitride can promote the reducing ability of cobalt oxide,and its N-rich structure leads to electron richness on the surface of the catalyst,which may be the reason for the abundant presence of oxygen and Co species.Therefore,g-C₃N₄ can be used as a catalyst support for good catalytic oxidation of VOCs.?4?The Co₃O₄ nanorods were successfully prepared by hydrothermal method,and the Co₃O₄ nanorod-supported Ag catalyst was prepared by impregnation method.The effect of Ag loading on its catalytic oxidation performance was discussed.The catalytic oxidation of toluene showed that Co₃O₄ nanorods have good toluene catalytic activity and increase with the increase of Ag loading.When the Ag loading reaches 7%,it has the highest catalytic activity,T₅₀ and T₉₀ are 244.3°C,256.5°C.When the Ag loading was increased to 10%,the catalytic activity of toluene showed a slight decrease.?5?The 7%Ag/Co₃O₄ sample has the best catalytic activity for oxidizing toluene.This may be due to the high dispersion of Ag on the surface of Co₃O₄nanorods,the high relative content of Co³⁺and adsorbed oxygen species on the surface,and reducibility of Co³⁺at low temperature.