Influence Of H₂O On Kinetics Of Low-temperature SCR Of NO By NH₃over V₂O₅/AC Catalyst

Nowadays, coal is one of the main energy sources in China, which ismainly applied in thermal power plant. It may cause serious globalenvironmental problems if NO_xare directly exhausted into air without anyDeNO_xprocess. The SCR of NO by NH₃over various catalysts is one of themost effective denitration technologies nowadays. The AC (activated carbon)supported V₂O₅(vanadium pentoxide)(V₂O₅/AC) catalyst is a new DeNO_xcatalyst, which has many advantages such as: excellent adsorption abilities;high activity during the temperature range of453-523K; SO₂can improve theactivity. So the V₂O₅/AC catalyst may be an excellent option for SCR of NOwith NH₃. In this thesis, the intrinsic kinetics of NH₃-SCR over V₂O₅/ACcatalyst in the condition of different H2O contents were studied, and a3Dmathematical model for monolithic SCR reactor was established to determinethe most suitable kinetic model for describing the NH₃-SCR reaction. Themain works are listed as follows: 1. V₂O₅/AC catalysts were prepared by the pore volume impregnation andwere characterized by the BET surface area and XPS. The BET surfacearea of V₂O₅/AC catalyst is larger than that of blank AC from the result.The XPS spectra shows that S species may exist in the form of SO₂-4on theV₂O₅/AC catalyst such as Na2SO₄and FeSO₄.2. Before the kinetic measurement, the stability of1.0wt%V₂O₅/AC catalystand the influence of internal and external diffusion were tested. From thestability test, the V₂O₅/AC catalyst prepared in this work exhibits a longlife of high activity and stability. From the influence of internal andexternal diffusion, the experimental condition can be decided as follows:the particle size0.2-0.3mm, the catalyst weight0.5g, the total gasflowrate400ml·min-1.3. The NO conversion in different condition were measured, and bothmechanical models (i.e. Eley-Rideal model, Langmuir-Hinshelwood model,and Mars-van Krevelen model) and the empirical (i.e. first-order model andpower-rate law model) were applied to correlate the experimental data.From the comparison of NO conversion between experimental data andcorrelated results, we can find that the SCR of NO by NH₃over V₂O₅/ACcatalyst follows the Eley-Rideal mechanism rather thanLangmuir-Hinshelwood or Mars-van Krevelen mechanism whether H2O iscontained in the flue gas or not, and the pre-exponential factor decreasesand activation energy increases with the increasing amount of H2O. 4. The kinetic parameters of Eley-Rideal model, first-order model andpower-rate law model were respectively input the3D mathematical modelof AC monolithic reactor. The Eley-Rideal model is more suitable fordescribing the SCR of NO by NH₃in comparison to the empiricalpower-rate law model through the comparison between experimental dataand predicted values.