The Experimental Study Of Denitrification And Demercuration By MnOx-CeO₂/γ-Al₂O₃Catalysts

China is the biggest producer and consumer of coal in the world. The emission of SO₂,NOxand mercury from coal combustion has brought serious pollution and restricted thesustainable development in our country. The emission and control of NOxand mercury inthe flue gas has attracted huge attention in recent years. The coal fired power plants havebeen equipping the FGD and SCR systems step by step. It will be the most economic andpractical way to remove mercury using the FGD and SCR systems. TheMnOx-CeO₂/γ-Al₂O₃catalyst was prepared using the sol-gel method in this article with theaim to get the high SCR activity and achieve the efficient oxidation and removal of mercurywith the absence of HCl.The SCR efficiency and sulfur resistance of the MnOx-CeO₂/γ-Al₂O₃catalyst weretested in the fixed reaction bed. The NO removal rate of this exceeded85%during80³00℃, which was proved to be an excellent low temperature SCR catalyst. In addition,the addition of Ce has improved the performance of SO₂poison resistance.The mercury oxidation and removal performance of the catalyst was tested with theabsence of HCl. It was found that the mercury removal efficiency reached higher than90%at250℃under the simulated gas atmosphere. The catalyst reactivity maintained verystable in the first12hours under the atmosphere of4.5%O₂, and the mercury removalefficiency kept higher than85%. When the catalytic reaction proceeded by10and24hours,about15%and28%Hg²⁺were detected in the end gas. It indicated that the elemental Hgwas oxided to be the Hg²⁺. It was also found that O₂and NO could facilitate the oxidationand removal of mercury, while NH₃and SO₂could obviously inhibit it.Several characterization methods including BET, XRD and XPS were adopted toprobe the catalytic mechanism. It was found that the oxidation and removal of mercuryfollowed the Mars-Maessen theory. The XPS results revealed that Mn existed mainly in theform of MnO₂and Mn₂O₃in the catalyst, and the content of MnO₂was higher than Mn₂O₃.While, Ce existed mainly as the form of Ce³⁺, and the content of Ce⁴⁺was some less. Theinhibition of NH₃derived from the competing adsorption of NH₃and Hg0.