M-Mn(M=Ni,Co,Fe) Composite Oxide Catalysts For Catalytic Combustion Of VOCs

With the rapid development of industry and economy, and the growth of population,environmental load is more and more serious, and then the problem of environmentpollution is becoming more and more serious. The Earth to survival of human isgradually deteriorating. The air pollution is one of the important factors that influencehuman survival and ecological environment. Volatile organic compounds （VOCs） ismore serious in atmospheric environmental pollution problem, people pay moreattention to the treatment method of VOCs. Catalytic combustion is an effective way totreat the VOCs, it is safer, and it occurs at lower temperatures with higher yields ofdestructions than thermal oxidation, and it has no secondary pollution, so it has beenwidely applied in the control of VOCs.Catalyst is the key of catalytic combustion method, because it determines theeffect of catalytic combustion. Transition metal element Mn has always been the hotspot in the research, and it has been applied in the research, the activity of Mn will beimproved when it compounds with other transition metal element, but the studies oncomposite catalysts of Ni-Mn, Fe-Mn, Co-Mn are little. In this work, Ni, Fe and Cocomposite with Mn respectively, and then the catalytic activity of this three series ofcatalyst will be evaluated.In this study, the catalysts of Ni-Mn/γ-Al₂O₃, Fe-Mn/γ-Al₂O₃and Co-Mn/γ-Al₂O₃were prepared by impregnation method. The activity of the catalyst in the completeoxidation of toluene was investigated, and the best of molar ratio of the various seriesof catalyst had been chosen in the end. The influences of Ni-Mn loading andcalcination temperature with experiment condition on the catalytic activity ofNi-Mn/γ-Al₂O₃in catalysis of toluene were investigated. These catalysts were characterized by Brunauer-Emmett-Teller surface area （BET）, scanning electronmicroscope （SEM） and Fourier transform infrared spectroscopy （FT-IR） techniques.The results shows that the catalytic activity of composite oxide is better than thatof a single oxide from the overall, then the best mole ratios of this three series catalystare Ni/Mn=0.5, Fe/Mn=2and Co/Mn=0.5respectively. The highest conversion rates are91.12%，84.24%，81.15%respectively. So, the best composite oxide catalysts areNi-Mn.The loading and calcination temperature of the catalysis with Ni/Mn=0.5wereinvestigated, the result indicated that the best loading amounts is20%, and the optimaltemperature is500℃. At the same time, the specific surface area is162m²/g.The results from the investigation of experiment conditions show that the catalystis suitable for catalyzing toluene of low concentration, whose loading rate, calcinationtemperature and molar ratio are20%,500℃, Ni/Mn=0.5respectively.The catalytic combustion products of the catalyst with the best molar ratio fromthe three series composite oxides are CO₂and H₂O, toluene or the by-product withbenzene ring.