Optimization Study On DeNO_x Performance Of Modified V-W/Ti SCR Catalyst Based On Metal G At Middle-low Temperature

Water vapor and SO₂ are inescapable components in the coal fuel gas,which leads to a research hot spot in the denitration field that broadening the reaction temperature window of NH₃-SCR catalyst with good poisoing resistance.The research point in this paper focused on vanadium.Firstly,antimony doped V-W/Ti catalysts were synthesized by the wetness impregnation method,and then the optimal amounts for every kind of element was obtained based on a series of experiment results.And then,Ce,La,and Y were introduced into the antimony doped V-W/Ti catalysts respectively,and the promoting effect was investigated.Meanwhile,the essential physical and chemical properties for all of the catalysts were reflected by N₂ physisorptionts,XRD,NH₃-TPD,and H₂-TPR.Finally,the processes of the vanadium or antimony oxides adsorbing airborne molecules in the gas were simulated in the software,Material Studio 8.0,based on the density functional theory,and the adsorption energy was calculated as well as the features of adsorption behaviors were summarized.The main results are as follows:Antimony can promote the sulfur poisoning resistance on the V-W/Ti catalyst and the redox ability at low temperature.Tungsten species can enter the gaps or insides of antimony oxide.When the loading components,V,W,and G,form a kind of appropriate balance between the surface acidity and redox ability of the catalysts,the best catalyst can keep a broad active window in the temperature region of 150³00?.V-W/Ti catalysts can not be poisoned with low-concentration SO₂ at low or middle temperature,but show irreversible deactivation at180?and reversible deactivation at 240?after SO₂ concentration increased to 350 ppm.3V-5W-2G/90Ti was thought to be the ideal formulation because of the NO_x conversions reaching 56%at 180?and 95%at 240?(GHSV=45,000 h^-1)in the presence of H₂O and SO₂,displaying valuable application potential.Rare-earth metals can make huge changes on the surface features of the modified catalysts through different patterns.All of three elements weakened the redox ability of the catalysts,resulting in the decrease of NO_x conversions at low temperature but the increasing tendency over 200?.The resistance to H₂O and SO₂ for 3V-3W-2G-1Ce/91Ti has a resemblance to3V-5W-2G/90Ti at 180?and 240?.Hence,3V-3W-2G-1Ce/91Ti can be used in industrial occasions with lower catalyst costs instead of 3V-5W-2G/90Ti.NH₃ can adsorb strongly on the acid sites of V?001?surface,and expressly seize the H⁺from the Br?nsted acid site.However,NH₃ showed the weak adsorption at G?222?and G?111?surface.Hence,the catalyst without V hardly showed good NO_x conversion in the experiment.As for H₂O,on one hand,it can produce effect on the active sites of both two kinds of metal oxide surface by right of O atom itself,on the other hand,it can form hydrogen bonds as NH₃does,which enhanced the stability of adsorption configurations and caused competitive adsorption to NH₃.The surface of vanadium oxide has the sulfur poisoning resistance attributed to difficult SO₂ adsorption except O_?1?-B substrate,and the surface of antimony oxide can adsorb and activate substantial O₂ in the gas,which achieves protection for antimony oxide from SO₂.Those consequences made sulfur poisoning resistance for V-W-G/Ti favorable,leading to stable deNO_x performance in the gas circumstance with 100 ppm SO₂ at low or middle tempeature.