Study On Low And Non Vanadium Catalysts For The Selective Catalytic Reduction Of NO_x By NH₃

In this work, we studied the catalytic performance of Ce-doped VTi catalysts and Mo-doped CeTi catalysts prepared by impregnation method, and the purpose is to improve the catalytic activity and reduce the content of V2O5. VCeTi and CeMoTi catalysts exhibited high NH3-SCR activity. Several methods including N2adsorption, XRD, Raman, H2-TPR, XPS were used to characterize the structure of the catalysts and the in Situ DRIFTS was used to reveal the influencing mechanistic cause of the promoting effect of Ce and Mo doping on the catalysts.The addition of Ce to VTi catalysts notablely improved the catalytic activity and the resistance against H2O, SO2and alkali metals. The optimal content of CeO2is5%by weight, and over90%NOX conversion was obtained on VCeTi catalyst in the temperature range of300-450℃under a GHSV of128,000h-1. Characterization results revealed that Ce addition inhibited the translation of TiO2from anatase to rutile which was caused by V2O5. The addition of Ce also increased the redox behavior and more NO was oxidezed to NO2on the catalyst surface which is beneficial for NH3-SCR. The activity of the Ce10Ti catalyst could be greatly enhanced by Mo addition and the optimal content of MoO3is5%by weight. Ce10Mo5Ti catalyst showed over90%NOx conversion in the temperature range of275～400℃under a GHSV of128,000h-1and showed higher tolerance to SO2and H2O poisoning than CelOTi. Further characterization revealed that Mo acted as structural promoter and strong interaction happened between Mo and Ti. Mo addition weakened the interaction between Ce and Ti which leaded to the the crystallization of CeO2and lowered the catalyst oxidizability. So the generation of nitrate that is from ammonia oxidization was suppressed. Besides, the addition of Mo greatly increased the number of Br(?)nsted sites on the catalyst surface which could not only lead to more adsorbed NH3species, but also reduced the inactive nitrate specie that may cover the active sites. All these are beneficial for the NH3-SCR of NOx.