| NOx is one of the major pollutants in the atmosphere, and the abatement of NOX has been a hotspot of study all over the world. Catalytic reduction of NO with CO is considered to be one of the most important reaction for NOX control. But most of employed DeNOx catalysts-noble metals catalysts are now facing the crisis of resource scarcity, therefore, in recent years, studies with transition metals have attracted much attention.TiO.2 possesses the advantages of resisting water and SO2. Except some previous reports of the V-W-Ti catalytic system, little work has been done on TiO2 as supports of DeNOx catalysts. So it is of great theoretical and practical significant to investigate the properties of TiO2-based catalysts in NO+CO reaction. In this study, the supports were TiO2, CeO2 modified TiO2 and CexTi|.xO2 mixed oxides, and the catalysts were prepared by the impregnation method, the activities and mechanisms of CuO/TiO2, CuO/CeO2-TiO2, CuO/CexTi,.xO2 and NM(Pt,Pd and Rh)/Ce0.3Ti0.7O2 in NO+CO reaction were examined by means of BET, TG-DTA, H2-TPR, CO-TPR, XRD, XPS and NO-TPD technologies. 1. Selection of active componentsAmong four active component(NiO, CoO, CuO and MnO) on Ti02, CuO shows the best activity and N2 selectivity in NO+CO reaction, and its low temperature activity was much higher than catalysts based on other supports(SiO2, ZSM-5 and y -Al2O3). As the calcination temperature increased, the activities of NiO/TiO2, CoO/TiO2 and MnO/TiO2 decreases but the activity of CuO/TiO2 increased. The activity of CuO/Ti02 was similar to thatof CuO/y-Al2O3. 2. Catalytic activity and mechanism of CuO/TiO2 in NO+CO reactionAfter calcination at 650癈, 12%CuO/TiO2 catalyst possesses the highest activity, and the Cu-Ti system showed good anti-sintering properties. The crystalline of TiO2 transformed from anatase to rutile with the increase in calcination temperature of support. The forming of rutile phase improved the activity of Cu-Ti catalyst system.Besides highly dispersed CuO, the CuO crystallite plays an important role in the NO+CO reaction. Results of XRD and TPR showed that the activity of CuO/TiO2 and CeO2/TiO2 has a close relationship with highly dispersed Cu species and fine CuO crystal formed on the surface. In addition, the smaller crystallite size of CuO and largermicro-strain increased the catalyst activity.NO-TPD profile also showed that the catalytic activities were closely related to NO dissociation-a step that determined the rate of NO+CO reaction, but were not affected by the amount of adsorbed NO. The addition of CeO2 accelerated the dissociation of NO on the surface of Cu-Ti, and improved the catalytic activity. The addition of CeO2, also restrained the crystallite transformation of TiO2, resulted in small CuO crystallite and decreased the bonding energy of Cu species. There are four Cu species on CuO/TiO2 catalyst: Cu0, Cu1", common Cu2+(Cu2+(l)) and Cu2+ with a very unstable train structure(-Cu-O-Ti-O-(Cu2+(ll)). Cu species on fresh Cu-Ti catalyst surface existed as Cu+, common Cu2+(Cu2+(l)) and Cu2+ , where Cu2+(l) was the main species; Cu species on Cu-Ti surface existed as Cu? Cu+, common Cu2+(Cu2+(l)) in the NO+CO reaction, the order of dissociative ability of these Cu species toward NO was : Cu?> Cu+ > Cu2+; The activity center of Cu-Ti catalysts system was Cu+ and Cu2+ at low reaction temperature, and Cu?and Cu+ at high reaction temperature.CuO on TiO2(nm) showed higher bonding energy than on TiO2 prepared by the S-G method and TiCU hydrolation method, and it has larger amount of Cu2+(ll), but showed lower activity than other two Cu-Ti catalysts in the NO+CO reaction. 3. Preparation of CexTii.xO2 and activity of CuO/ CexTii_xO2CexTi|.xO2 mixed oxides at different mole ratios(x=0, 0.1, 0.2-0.9, 1.0) were prepared by co-precipitation method. The results show that different Ce/Ti mole ratios and calcination temperatures induce regular changes of structure and reductive properties of the CexTi|.xO2 mixed oxides. When x=0.1-0.5, amorphous CeTi2O6 phase mainly formed a...
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