Preparation Of MO_x/TiO₂（M=Co,Cu,Mn）catalyst And Its VUV Catalytic Degradation Of Toluene

Toluene is an important source of volatile organic compounds in the atmosphere,and excess toluene is the main precursors of photochemical smog,ozone and PM2.5,which are harmful to the ecological environment and human health.Therefore,it is need to be controlled the toluene pollution urgently.Photocatalytic oxidation is considered as a green technology,which can oxidize toluene into CO₂ and H₂O at room temperature and pressure.The key issue of photocatalytic oxidation of toluene is the development of stable and high performance photocatalyst.TiO₂ is widely used because of its stable chemical properties,cheap and non-toxic,and improving its photocatalytic efficiency is one of the research hotspots.Transition metal oxides can form a composite catalyst with TiO₂.The transition metal oxides can help the adsorption of toluene molecules on catalysts,the separation of photogenerated electrons and holes pairs,and the generation of oxidative species,which has attracted wide attention from researchers.In this study,we selected the MO_x/TiO₂composite catalyst photocatalytic oxidation of toluene as a reaction system under the irradiation of VUV.The main research contents and conclusions are as follows:（1）Co₃O₄/TiO₂ catalysts composites with different mass ratio are prepared by hydrothermal method for the photocatalytic oxidation of toluene and the decomposition of O₃.The results show that 3Co₃O₄/TiO₂ with a load of 6%has the best catalytic effect.Compared with the degradation of toluene by VUV,the degradation rate of toluene by3Co₃O₄/TiO₂ increased from 70%to 92%,the mineralization rate increased from 59%to 75%,and the residual O₃ in the tail gas was less than 1%.The 3Co₃O₄/TiO₂ catalyst improved the separation ability of photogenerated electron-hole pair and the oxidation ability of the catalyst.The 3Co₃O₄/TiO₂ catalyst has good stability,and the degradation rate of toluene remains above 85%after three cycles of 3-hour test each time.（2）Cu O/TiO₂ catalyst was prepared by precipitation impregnation method,and the effect of Cu O dispersion on its catalytic activity was studied.The degradation rate and mineralization rate of toluene of 1Cu O/TiO₂ catalyst with 1%loading capacity are85%and 73%,respectively,which are 16%and 15%higher than that of VUV,respectively,and the O₃ in tail gas is eliminated completely.After 900 min stability test,the degradation rate of toluene remained above 83%.The reasons for the excellent activity of Cu O/TiO₂ are as follows:1)Cu O is uniformly dispersed on the surface of TiO₂ nanoribbons,and the particle size of Cu O is less than 10 nm,which provides more active sites for toluene degradation on the surface of the catalyst.2)It promotes the adsorption of O₃ and the rate of the formation of·OH radical from O₃.（3）Mn O₂/TiO₂ with a mas ratio of 0.15%was prepared by impregnation reduction method.For the Mn atoms existed in the form of Mn⁴⁺on Mn O₂/TiO₂ and there were a lot of oxygen vacancies in the catalyst,which provided more active sites for toluene degradation.The degradation rate of toluene in the condition of irradiation of VUV was4.9 times higher than that of UV,and the mineralization rate of para-toluene reached 73%.