Study On Synthesis And NH₃-SCR Performance Of Mn-based Denitration Catalysts In FCC Regeneration Flue Gas

Nitrogen oxides?NO,N₂O and NO₂,etc.?,which originate from various processes for the combustion of fossil fuel,are a major type of air pollutants and are very harmful to human health due to the formation of photochemical smog,acid rain,the ozone hole and a series of environmental pollution.NO_X emissions from a typical refinery are a few thousand tonnes,and the fluid catalytic cracking?FCC?section contributes about 50 % of the total amount.The selective catalytic reduction of NO_X with ammonia?NH₃-SCR?technology has become more and more important for researchers as an effective method for the removal of NO_X emitted from stationary sources flue gas and motor vehicles exhaust.In recent years,the application of manganese titanium based catalyst in NH₃-SCR reaction has attracted more and more attention of researchers.The catalyst with Mn as the active component exhibits good low temperature NH₃-SCR activity,high N₂ selectivity,so it has been widely used.Therefore,this thesis is based on Mn-Ti catalyst,preparing catalysts with different Mn/Ti mass ratios and modifing different metals for the active component.The catalysts were characterized by the methods of XRD?SEM?BET?Raman and NH₃-TPD.And their catalytic performances for deNO_X from flue gas and diesel engine exhausts were evaluated by NH₃-SCR reaction.The activity test results showed that,in the present study,the Mn/Ti catalyst by hydrothermal synthesis gives the best activity.Different catalysts with different Mn/?MnO_X+TiO₂?ratios have different catalytic activity,and it was found that the NH₃-SCR reaction activity was the best when Mn/?MnO_X+TiO₂?mass ratio is 35 %.This catalyst gives high NO conversion rate in the low-temperature section,and the conversion was 89 % at 100 ?,exhibiting the best catalytic activity at low temperature.Besides,NO conversion was above 90 % at 100 ??350 ?.In situ DRIFTS of NH₃ adsorption results show that the asymmetric bending vibration peaks of N-H bond in NH⁴⁺ chemisorbed on Br?nsted acid site disappear after evacuation at 100 ?.Therefore,the Lewis acid sites are relatively more stable,and the mechanism of E-R was more obvious under the conditions of high temperature.The introduction of different metal oxides is an important factor which influences the catalytic activity of NH₃-SCR.When loading different metals,the catalyst with Fe loaded has a slightly better high temperature activity,and the temperature window was wider than the catalysts with no metals loaded.The catalytic activity of the catalysts with Ni and Cd loaded were worse than the catalysts with no metals loaded,among which the catalysts with Cd loaded was worst,only in 175 ??225 ? reached 100 % NO conversion rate.The catalytic activity of the catalysts with Ce loaded was best,exhibiting a good reaction activity at low temperature,and its temperature window is 100 ??350 ?.Supported Ce had a wide temperature window and good activity,and many other advantages.The introduction of Ce may improve the dispersity between manganese and titanium species and the catalyst dispersed more homogeneously.The desorption peak of NH₃-TPD had maximum intensity.The results illustrate that the adsorption ability of NH₃ enhanced,which is conducive to the NH₃-SCR reaction.