Research On The Middle-low Temperature Denitration Properties Of V₂O₅-MoO₃ SCR Catalysts

Ammonia selective catalytic reduction?NH₃-SCR?method is the mainstream of stationary source denitration technology,and the core of technology is the SCR denitration catalyst.Currently commercial SCR denitration catalyst active is mainly V₂O₅-WO₃?MoO₃?/TiO₂ honeycomb,plate or corrugated board type catalyst,which is based on V₂O₅ as active component,WO₃?or MoO₃?as adjuvant,and TiO₂ as carrier.The catalyst has wide application in coal-fired power plants,and its applicable temperature window is 300-420 oC.When temperature is below 300 oC,the catalyst can't applicable.However,when the coal-fired power plant is running at low load,the flue gas temperature is usually lower than 300 oC,the conventional SCR denitration catalyst must be withdrawn from use?stop ammonia injection?.Besides,in addition to the thermal power industry,the industrial boiler fule gas temperature of the steel smelting,glass manufacturing and other industries of industrial boiler is generally under 300 oC?for example,coke oven flue gas temperature of the steel industry is generally 250-300 oC,and the sintering machine flue gas temperature is 180-200 oC,and the flue gas temperature of the glass furnace denitration section is 230-290 oC?.Based on these,it is very necessary to research and develope a new type of SCR denitration catalyst which is suitable for the low temperature?180-300 oC?flue gas conditions.Considering the technical requirements for middle-low temperature denitration of flue gas,a series of powder and plate type V₂O₅-MoO₃/TiO₂ SCR catalysts were prepared using incipient wetness impregnation method within V₂O₅ as the active component and MoO₃ as the promoter.Experiments were performed to investigate the effects of active component and promoter contents on the activities and resistance to SO₂ and H2 O of the catalysts.Characterization was conducted on the fresh and used catalysts.And the optimal catalyst was further studied to reveal the denitration performance under different flue gas conditions.The results indicated that the activities of the catalysts were enhanced with the increase of V₂O₅ loadings.Also,addition of MoO₃ could promote the catalytic activity.XRF,XPS,FT-IR and other characterization results suggested that MoO₃ content could affect the V⁴⁺/V⁵⁺ ratio in the catalyst.Increase of relative MoO₃ content was favorable for the formation of non-stoichiometry vanadium species as well as the rise of chemical adsorption oxygen ratio.Therefore,interactions between molybdenum and vanadium species might be the essential reason for the resistance to the deactivation of SO₂ and H2 O.The denitrification efficiency of 3V₂O₅-10 MoO₃/TiO₂ plate catalyst held steady around 82% after 30 days test in presence of SO₂ and H2 O at temperature of 200 oC and space velocity of 3500 h-1.The catalyst exhibited excellent resistance to the deactivation of SO₂ and H2 O under middle-low temperature.Finally,this article aimed at the modification research of low temperature SCR denitration catalyst,like precursor solution pH,sulfated processing modification means,doped metal oxide for further improvement of the denitration efficiency of the catalyst.Given the precise control of pH and sulfuric acid acidification treatment on low improvement on catalyst efficiency,and this operating process is relatively complex to industrial applying.Ultimately X metal oxide doped catalysts for modification was chosen.the modified plate catalyst was examined under SO₂ and H2 O,as well as the working flue gas condition.Results showed that the modification of the low temperature SCR plate denitration catalyst could maintain the outstanding performance of resistence SO₂ and H2 O poisoning of original catalyst,and the denitration activity had a certain extent of improvement in low temperature area.This catalyst had a good adaptation to flue gas conditions,and was expected to achieve industrial production application.