Preparation Of Copper-tungsten (cerium/titanium) Oxide And Study On Catalytic Selective Reduction Of NO_x With Ammoni

With the rapid development of industrialisation,various types of plants are emitting more and more nitrogen oxides(NOx),causing serious environmental hazards.NH3 selective catalytic reduction(NH3-SCR)method is the most commonly used technology for the removal of nitrogen oxides(deNOx)from flue gases.The synthesis of NH3-SCR catalysts with low temperature,high activity and resistance to H2O and SO2 poisoning is of great importance for the characteristics of flue gas emissions from non-electric industries.In this paper,Cu1-mWmOx,Cu0.1-mWmCe0.9Ox and Cu0.1-mWmTiOx oxide catalysts have been designed and synthesized with copper and tungsten as the main active component of the catalysts.The effects of different tungsten and copper contents on the physicochemical properties and denitration performance of NH3-SCR catalysts were investigated by various characterization methods and in situ DRIFTS.A series of Cu1-mWmOx(m=0.3,0.4,0.5,0.6,0.7)catalysts were synthesised and the effect of W addition on the catalytic activity of the Cu1-mWmOx catalysts was tested.The Cu1-mWmOx catalysts showed better catalytic activity compared to pure CuO catalysts,with Cu0.5W0.5Ox having a good activity window and N2 selectivity in the temperature range of 200 ℃ to 340 ℃(>90%NO conversion).However,the Cu0.5W0.5Ox catalysts had a narrow activity temperature window and were less resistant to H2O and SO2 poisoning.A series of Cu0.1-mWmCe0.9Ox(m=0.05,0.06,0.07)catalysts were synthesised and the effect of the introduction of different W contents on the catalyst performance was tested.Among them Cu0.04W0.06Ce0.9Ox showed a wide temperature window and excellent resistance to H2O poisoning in the temperature range of 140℃ to 400℃,but poor resistance to SO2 poisoning at low temperatures.Various characterisations showed that having more surface acidic sites on the Cu0.1-mWmCe0.9Ox catalyst could promote NH3 adsorption and activation and inhibit NH3 peroxidation,resulting in a Cu0.1-mWmCe0.9Ox catalyst with high activity over a wide temperature range.A series of Cu0.1-mWmTiOx(m=0.05,0.06,0.07,0.08,0.09)catalysts were synthesised and the effect of the introduction of W on the catalytic activity of the catalysts was tested.The better NH3-SCR activity of Cu0.03W0.07TiOx may be related to the synergistic effect of the moderate oxidation properties of the catalysts and the enhanced surface acidity.The reason for the good H2O/SO2 resistance at low temperatures after W addition in the Cu0.03W0.07TiOx catalyst was analysed in particular by in situ DRIFTS under different conditions.The reason is that the addition of W obviously inhibits the competitive adsorption between H2O/SO2 and NOx on the catalyst surface.The possible SCR reaction process over Cu0.03W0.07TiOx catalysts was also proposed in combination with various characterisation results.