Investigation On Catalytic Oxidation Of Low Concentration Benzene And Formaldehyde Removal

In this work,supported Pt catalysts,MnO₂ oxides with different phases and CoMn with unique morphology were expected to eliminate indoor benzene and formaldehyde.The structure-activity relationship between structure and activity of the catalysts was constructed by the structure characterizations,activity evaluation and mechanism studies.The results were summarized as follows:Hydrophobic TS-1 zeolite with pore size closed to the dynamic diameter of benzene and superior hydrophobic properties was selected as substrate for Pt dispersion to catalyze the benzene oxidation reaction at low temperature,the relationship between particle size of Pt and specific benzene reaction rate was also studied.The catalyst with the least Pt loading of 0.03wt%and smallest average Pt NPs of ca.5 nm exhibited the highest specific rate and lowest Ea,indicating the smaller Pt NPs favored the reaction.While 0.66 wt%Pt/TS-1 catalyst has the greatest number of active sites and best benzene oxidation performance,100%benzene conversion can be achieved at 140 ^oC(WHSV=60,000 mL g^-1 h^-1,relative humidity=50%).the complete oxidation temperature of benzene on 0.66 wt%Pt/TS-1 was much lower than that of 0.03 wt%Pt/TS-1.These results suggested that the catalytic performance of benzene was not only related to the particle size,but also restricted by the number of active centers.Additionally,the Pt/TS-1 catalyst has excellent water resistance and stability.In order to reduce high cost of precious metals,manganese oxides with high efficiency were selected for VOCs removal.Four types of MnO₂ with different phase were synthesized to test for C₆H₆ and HCHO catalytic oxidation.?-MnO₂ shown the highest HCHO catalytic activity while?-MnO₂ exhibited better benzene catalytic performance.It was observed that complete conversion of HCHO occurred at 70 ^oC(WHSV=60,000 mL g^-1 h^-1,relative humidity=50%?25 ^oC?)over?-Mn O₂ catalyst.Such high activity can be ascribed to the high activity and low reduced temperature of surface oxygen was confirmed by H₂-TPR and XPS studies.?-MnO₂ was prepared with solvent free synthesis exhibited the highest benzene catalytic performance,it was observed that 90%of benzene occurred at 197 ^oC(WHSV=60,000 m L g^-1 h^-1,relative humidity=50%?25 ^oC?).The medium temperature lattice oxygen was active species for the complete oxidation of benzene,?-MnO₂ with good activity of lattice oxygen facilitated it shown higher activity of benzene oxidation characterized by H₂-TPR,C₆H₆-TPSR,C₆H₆-TPD and C₆H₆-TPO results.To further reduce the complete oxidation temperature of formaldehyde.We developed a hybrid nanostructure of?-MnO₂@Co₃O₄ via two-step hydrothermal synthesis method,the effect of CoMn ratio on the oxidation activity of formaldehyde was also investigated.100%HCHO conversion can be achieved at 70 ^oC(WHSV=75,000 mL g^-1 h^-1,relative humidity=50%?25 ^oC?)over?-MnO₂@Co₃O₄-II?Co/Mn=1?catalyst,such high formaldehyde may ascribed to the controllable construction of heterogeneous interface and the generation of K₆Mn₂O₆ species.On the other hand,Co₃O₄ nanocubes with tunable particle size were synthesized and to test for HCHO catalytic oxidation.The results suggested that Co₃O₄ with an average particle size of 42 nm and narrow size distribution?30-60 nm?exhibited the best HCHO catalytic activity.It was observed that complete conversion of HCHO occurred at 130^oC(WHSV=75,000 m L g^-1 h^-1,relative humidity=50%?25 ^oC?),indicating that smaller size and narrow size distribution of Co₃O₄ nanocubes facilitated the HCHO catalytic oxidation reaction.