Preparation Of Modified V₂O₅/TiO₂ Catalyst In Wide Temperature Domain And Regeneration Of Sulfur Poisoning Catalyst For SCR Denitration

The operating temperature of most commercial SCR catalysts ranges from 300? to 450?.When the unit is at low load or in the startup/shutdown process,flue gas temperature decreases as well as the denitrification efficiency.Therefore,it is necessary to broaden the operating temperature range of the catalyst to meet practical requirements.In this paper,V₂O₅-CeO₂/TiO₂ catalysts were studied and modified by doping MnOx.In addition,a new V₂O₅@CeO₂/TiO₂ core-shell structure was prepared.The activity,sulfur resistance and water resistance of the catalyst were tested.Also,the performance of the catalysts was analyzed by BET,XRD,NH3-TPD and H2-TPR.Finally,the preferred 0.5%V₂O₅-10%CeO₂-20%MnOx/TiO₂ catalyst was used in the sulfur poisoning and regeneration experiments.The main conclusions were as follows:The V₂O₅-CeO₂/TiO₂ catalyst was modified by doping MnOx and the effects of the loading amount of V₂O₅ and MnOx on the performance were studied respectively by characterization.The results of activity test and sulfur resistance and water resistance test showed that V₂O₅ affected catalysts mainly at high temperature,while MnOx at low temperature.Excessive or low load reduced the catalyst's denitrification activity,sulfur resistance and water resistance.According to the characterization results,the surface acidity of the catalyst increased with increasing V₂O₅ amount,but the crystallinity of the catalyst increased too,which was unfavorable to the reaction.Loading of MnOx improved the redox ability of the catalyst.However,the specific surface area and the surface acidity of the catalyst decreased rapidly with excessive load and MnOx changed from Mn2O3 to Mn3O4,which were not conducive to the removal of NOx.The V₂O₅@CeO₂/TiO₂ core-shell structure was prepared by electrostatic self-assembly method.The denitrification activity,sulfur resistance and water resistance of the catalyst were tested.Meanwhile,the interaction mechanism was analyzed by in situ infrared analysis.It was shown that the denitrification efficiency was above 80%at 260?400?.When the sulfur content in flue gas was low,denitrification efficiency of this catalyst decreased more slowly compared with the catalyst prepared by traditional impregnation,but the denitrification efficiency decreased more quickly with high sulfur content.According to in situ infrared analysis,the absorption peak of NH3 gradually weakened and disappeared when inletting NO and O₂ after pre-absorption of NH3,while the absorption peak of NO still existed when inletting NH3 and O₂ after pre-absorption of NO.It was speculated that V₂O₅@CeO₂/TiO₂ followed the E-R mechanism.With preferred 0.5%V₂O₅-10%CeO₂-20%MnOx/TiO₂ catalysts,three methods were used to study the regeneration of sulfur poisoning catalysts:water washing,heating and thermal reduction.Catalysts regenerated by water washing showed the best performance,the denitrification efficiency of which could be restored to 90%of the efficiency of fresh catalysts while catalysts regenerated by heating regeneration performed worst.It also indirectly proved that the main reason for the deactivation of catalysts was the formation of ammonium sulfate,which was reversible.Another reason was the sulfation of metal oxides.According to the characterization analysis,the specific surface area of the catalyst after washing regeneration was merely lager than that of fresh catalysts while it decreased after thermal reduction.The redox ability and the surface acidity of the catalyst decreased after heating and thermal reduction.