Performance Of NH₃-SCR Over Natural Manganese Ore And It Supported Metal Oxides

With the increase of NO_x emissions,the air pollution has become more and more serious.And the NO_x emission standard was becoming stricter in recent years.When the V₂O₅-WO₃?MoO₃?/TiO₂ catalyst could not meet the NO_x emission standard in low temperature,seeking low-temperature,high efficiency and green catalyst in NH₃-SCR was attracted much attention of researchers both domestic and overseas.Mn-based catalysts were attracted more and more attention due to their excellent performance in low-temperature of NH₃-SCR.In this paper,some novel SCR catalysts were prepared on the basis of natural manganese ore and supported metal oxides?TiO₂,Ce O₂,Fe₂O₃?on it.XRD,BET,XPS,H₂-TPR,NH₃-TPD,SEM and TEM were utilized to characterize the mineral phase and morphology of natural manganese ore and composite catalysts.And the influence of different factors?calcined temperature,ratio of active component,H₂O and SO₂,NH₃/NO and preparation method?on NH₃-SCR performance of different catalysts were studied by experiments.Main conclusions were shown as follows:?1?The natural manganese ore was collected from Qingyang?Anhui Province?has good low-temperature denitrification performance under the simulated environment of anhydrous sulfur-free flue gas.The NO conversion was up to 92.3% when the reaction temperature at 250?,while it's over 85% when the temperature was between 150? to 300?,and the N₂ selectivity was up to 99%.But its resistance to H₂O and SO₂ was poor,the deactivation of SO₂?0.01%,0.02%?on the catalyst was reversible,but the high concentration of SO₂?0.03%?could make the catalyst inactivated and it was irreversible.?2?TiO₂ loaded on natural manganese ore were prepared by sol-gel method,the NO conversion was not affected when 10% water vapor was introduced into the system,but the poisoning of SO₂ on the catalyst was still inevitable.?3?The SCR activity was improved when CeO₂ loaded on natural manganese ore were prepared by impregnation method.The NO conversion was up to 72.7% and 95.7% when the reaction temperature was 100? and 250?,respectively,but the resistance to H₂O and SO₂ was still poor.?4?The activity of low-temperature denitrification was improved when ?-Fe₂O₃ supported on natural manganese ore were prepared by solid-phase grinding method.The addition of H₂O?10%?or low concentration of SO₂?0.01%?to the system only has a little effect on the NH₃-SCR activity of the catalyst,but high concentration of SO₂?0.03%?still has a large effect.?5??-Fe₂O₃ was added to Ce O₂/NMO catalyst as an auxiliary.The NO conversion of the composite catalyst was above 90% at the reaction temperature window of 150-250?,it also has a good resistance to H₂O,SO₂ and alkali metal.And the NO conversion was beyond 80% in the reaction temperature range of 120-250 ? when the deactivated catalyst was regenerated by ultrasonic washing,which has a good regeneration performance.