Quantum Chemistry Research On DeNO_x And Poisoning Mechanism Of SCR Catalyst

Nitric oxides?NO_X?are widely thought to be one of the main atmospheric pollutants in the world and its emissions show a steady growth trend.The main source of NO_X is the fossil fuels combustion from power plants.The selective catalytic reduction?SCR?of NO_X with NH₃ as reductant is most efficient and widely technology for abating NO_X emitted from stationary power stations at present.In the flue gas denitration system,one of the most important parts is the catalyst,whose property would directly affect and cost of denitrification.Poisoning is an inevitable problem in the practical application for the SCR catalyst.This article study the mechanism of SCR reaction and metal poisoning on vanadia-based catalysts with the density functional theory?DFT?using the clusters of V₆O₁₅ and V₆O₁₅⁺.It will provide theoretical guidance for the efficiency improvement of denitrification and the poisoning resistance of catalyst.The article introduces some basic principles of quantum chemistry such as fundamental equation of quantum chemistry,some calculation methods and Gaussian software introduction.Using the density functional theory?DFT?method,V₆O₁₅ and V₆O₁₅⁺ cluster models are used to simulate the surface morphology of vanadium based catalysts.The structure parameters,single point energy and charge analysis are carried out by optimizing the configuration.On the basis of the optimized models,the chemical properties of V₆O₁₅ and V₆O₁₅⁺ cluster models are discussed in turn,which with good acidity,good oxidation resistance,and the difficulty in the re-oxidation of the reduced molecules.In the third part,the adsorption mechanism of Lewis adsorbing the water molecule to form a V-OH is studied on the based of optimized V₆O₁₅ and V₆O₁₅⁺cluster models.Intermediate and transition state structures are formed in the reaction process and the paths of IRC?Intrinsic Reaction Coordinate?are analysed.The adsorptions of NO and NH₃ on the catalyst are simulated,and the reaction mechanism of SCR are analyzed with adsorption energy,electrostatic potential and charge transfer.The fourth part mainly focused on the influence of alkali and alkali-earth metals on the V₆O₁₅ and V₆O₁₅⁺ cluster model.And the molecular structure parameters,adsorption energy,LUMO orbit energy and hydrogenation reaction of the catalyst before and after poisoning were calculated.The results indicated that the catalytic activity is decreased by adding K?Na and Ca metals.Poisoning effect order for V₆O₁₅ cluster are K-doped >Na-doped >Ca-doped >Undoped,for V₆O₁₅⁺cluster are Ca-doped >K-doped > Na-doped >Undoped.