| With the rapid development of economy, the growing demand for electricity makes the NOx emissions level, which comes from the power plant coal-fired boiler, also gradually increased, and the selective catalytic reduction (SCR) technology is the most effective way to control NOx emissions from the stationary sources. In recent years, the low-temperature SCR technology, because of its advantages of energy-saving features, low running cost and the wide industrial application prospect, has attached more and more attention. V2O5-WO3(MoO3)/TiO2is a widely used commercial catalyst in SCR. But its optimum denitrification effect appears in a high temperature range of300～400℃, and it also has other disadvantages, such as high toxicity and SO2oxidation rate of vanadium as well as secondary pollution, so it’s not suitable for application and popularization in the low-temperature SCR. This paper has put forward a novel F-doped cerium tianium SCR and systematically studied its low-temperature SCR DeNOx performance.In this paper, we prepared two series of F-doped cerium titanium catalysts through sol-gel-impregnation and coprecipitation methods, results showed that F-doping improved denitration activity of the cerium titanium catalyst and the effect of F-doping and Ce concent on the denitration efficiency showed that the optimal proportion of the catalysts were Ce0.1/TiF1.5and Ce0.3TiF1.5, respectively. The investigation of space velocity, concentration of O2,[NH3]/[fNO] and calcination temperature found that the two kinds of catalysts calcined at500℃displayed the best denitration efficiency under the technology condition of5vol%O2and [NF3]/[NO] of1.2. Low-temperature DeNOx efficience of the catalyst prepared by coprecipitation was greatly higher than that of sol-gel-impregnation method under the same reaction conditions, NOx conversion of Ce0.3TiF1.5reached92.19%at180℃when the GHSV was41000h-1. The influence of H2O and SO2on the denitration performance showed that both series of catalysts showed good resistance to H2O and relatively poor resistance to SO2. In contrast, the catalysts prepared by coprecipitation method had a better H2O-resistance and SO2-resistance.We had used XRD, BET, PL, XPS and NH3-TPD characterization methods to study the physical-chemical properties of the two kinds of catalysts, such as crystal structure, specific surface area, oxygen vacancy, element valence and surface acidity, which indicated that partially substitution of O in TiO2lattice by F had caused a series of changes in the catalyst structure and surface properties. The catalysts prepared by coprecipitation exhibited amorphous structure and F-doping could enhance the interaction between Ce and Ti more than it was in the catalyst prepared by sol-gel-impregnation method, so that the catalyst produced a larger specific surface area, more oxygen vacancies, chemisorbed oxygen and acid sites. These factors above were conducive to the improvement of denitration performance of the catalyst. Based on the catalysts prepared by co-precipitation had better low-temperature catalytic activity and a more favorable structure and physical-chemical properties, so we made an more intensive research on this series of catalysts. Raman test showed that F-doping was beneficial to the adsorption of O2on the oxygen vacancy to generate highly active superoxide radical(O2-), which could react with NO to produce nitro and nitroso intermediate species; DRIFTS characterization results also proved that the surface of F-doped catalyst had more adsorbed NOX, and the species of nitrate and nitrite. All these favorable changes above simultaneously enhanced the catalytic activity for NH3-SCR of NOX. |
PDF Full Text Request