WO_3对V_2O_5/TiO_2-ZrO_2催化剂NH_3-SCR脱硝的影响
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摘要
采用共沉淀法制备TiO_2-ZrO_2固溶体浸渍法负载WO_3和V_2O_5得到一系列V_2O_5-(x%)WO_3/TiO_2-ZrO_2催化剂。利用比表面积测定(BET)、X射线衍射(XRD)、原位漫反射傅里叶变换红外光谱(In situ DRIFTS)、程序升温脱附(NH_3-TPD)、高分辨率透射电子显微镜(HRTEM)等表征技术,结合脱硝性能测试,研究催化剂的表面特性、微观结构及脱硝活性;同时针对优选出的脱硝性能较好的催化剂,研究SO_2和H_2O对其活性的影响。结果表明:WO_3的负载增强了催化剂孔隙结构的稳定性和Lewis酸的强度。当WO_3含量为9%时,催化剂的孔隙结构最稳定,表面-NH_2活性物种最多,NH_3的吸附量最大脱硝活性最高,在300~400℃的温度窗口平均保持在92%以上。而当烟气中同时含有SO_2和H_2O时,催化剂活性会显著下降,且中毒不可逆。
TiO_2-ZrO_2 solid solution was prepared by a co-precipitation method and V_2O_5-(x%)WO_3/TiO_2-ZrO_2 catalysts were prepared using the impregnation method.The physicochemical properties were investigated by X-ray diffraction(XRD),BET specific surface area,NH_3 temperature-programmed desorption(NH_3-TPD),in situ diffuse reflectance infrared Fourier transform spectroscopy(in situ DRIFTS) and high-resolution transmission electron microscopy(HRTEM).Their catalytic performance for the selective catalytic reduction of NO_x was tested,as well as the effect of SO_2 and H_2O on SCR catalytic activity for the preferred catalysts.It was found that the strength of Lewis acid sites and the stability of the pore structure are increased with the load of WO_3.The results of catalytic activity indicated that the catalyst with 9%WO_3 content exhibits 92%NO conversion within the wide temperature range of 300 ℃ to 400 ℃ due to the most stable pore structure,the most active species-NH_2 on the surface and the biggest absorbing capacity of NH_3.When SO_2 and H_2O get into the flue gas,the SCR catalytic activity sharply decreases and it is an irreversible process.
TiO_2-ZrO_2 solid solution was prepared by a co-precipitation method and V_2O_5-(x%)WO_3/TiO_2-ZrO_2 catalysts were prepared using the impregnation method.The physicochemical properties were investigated by X-ray diffraction(XRD),BET specific surface area,NH_3 temperature-programmed desorption(NH_3-TPD),in situ diffuse reflectance infrared Fourier transform spectroscopy(in situ DRIFTS) and high-resolution transmission electron microscopy(HRTEM).Their catalytic performance for the selective catalytic reduction of NO_x was tested,as well as the effect of SO_2 and H_2O on SCR catalytic activity for the preferred catalysts.It was found that the strength of Lewis acid sites and the stability of the pore structure are increased with the load of WO_3.The results of catalytic activity indicated that the catalyst with 9%WO_3 content exhibits 92%NO conversion within the wide temperature range of 300 ℃ to 400 ℃ due to the most stable pore structure,the most active species-NH_2 on the surface and the biggest absorbing capacity of NH_3.When SO_2 and H_2O get into the flue gas,the SCR catalytic activity sharply decreases and it is an irreversible process.
引文
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[11]李鹏,张亚平,肖睿,等.整体式V_2O_5-WO_3/TiO_2-ZrO_2催化剂用于NH_3选择性催化还原NO_x[J].中南大学学报:自然科学版,2013,4:1719-1726.Li Peng,Zhang Yaping,Xiao Rui,et al.Selective catalytic reduction of NO_x with NH_3 over V_2O_5-WO/TiO_2-ZrO_2monolith catalysts[J].Journal of Central South University:Science and Technology Edition,2013,4:1719-1726.(in Chinese)
[12]卢熙宁,宋存义,童震松,等.结掺杂TiO_2负载锰铈氧化物低温催化还原NO_x[J].北京科技大学学报,2014,9:1222-1232.Lu Xining,Song Cunyi,Tong Zhensong,et al.Low-temperature catalytic reduction of nitrogen oxides over managanese-cerium composite oxides supported on zirconiumdoped titanium dioxide[J].Journal of University of Science and Technology Beijing,2014,9:1222-1232.(in Chinese)
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[14]Bond G C,Tahir S f.Vanadium oxide monolayer catalysts prepartion,characterization and catalytic activity[J].Applied Catalysis A:General,1991,71(1):1-31.
[15]Wachs I E,Weckhuysen B M.Structure and reactivity of surface vanadium oxide species on oxide supports[J].Applied Catalysis A:General,1997,157(1/2):67?90.
[16]辛勤,罗孟飞.现代催化研究方法[M].北京:科学出版社,2009:83-88.Xin Qin,Luo Mengfei.Modern Catalytic Research Methods[M].Beijing:Science Press,2009:83-88.(in Chinese)
[17]Topsoe N Y,Topsoe H,Dumesic J A.Vanadia/titania catalysts for selective catalytic reduction(SCR)of nitric-oxide by ammonia:1.combined temperature-programmed in-situ FTIR and on-line mass-spectroscopy studies[J].Journal of Catalysis,1995,151(1):226-240.
[18]Pan S,Luo H,Li L,et al.H_2O and SO_2 deactivation mechanism of MnO_x/MWCNTs for low-temperature SCR of NO_x with NH_3[J]Journal of Molecular Catalysis A:Chemical,2013,377:154-161.
[19]Tsyganenko A A,Pozdnyakov D V,Filimonov V N.Infrared study of surface species arising from ammonia adsorption on oxide surfaces[J].Journal of Molecular Structure,1975,29(2):299-318.
[20]Sun D,Liu Q,Liu Z,et al.An in situ DRIFTS study on SCR of NO with NH_3 over V_2O_5/AC surface[J].Catalysis Letters,2009,132(1):122-126.
[21]Wu Z,Jiang B,Liu Y,et al.DRIFT study of manganese/titania-based catalysts for low-temperature selective catalytic reduction of NO with NH_3[J].Environmental Science and Technology,2007,41(16):5812-5817.
[2]中华人民共和国环境保护部.火电厂氮氧化物防治技术政策[Z].2010-01-27.Ministry of Environmental Protection.Technical Policy for Prevention and Control of Nitrogen Oxides in Thermal Power Plant[Z].2010-01-27.(in Chinese)
[3]闫志勇高翔,吴杰,等.V_2O_5-WO_3-MoO_3/TiO_2催化剂制备及NH_3选择性还原NO_x的试验研究[J].动力工程,2007,27(2)282-286.Yan Zhiyong,Gao Xiang,Wu Jie,et al.Experimental study on preparation of V_2O_5-WO_3-MoO_3/TiO_2 catalysts and selective reduction of NO_x with NH_3[J].Journal of Power Engineering,2007,27(2):282-286.(in Chinese)
[4]Alemany L J,Lietti L,Ferlazzo N,et al.Reactivity and physicochemical characterization of V_2O_5-WO_3/TiO_2 de-NO_x catalysts[J].Journal of Catalysis,1995,155(1):117-130.
[5]侯亚芹,黄张根,马建蓉.V_2O_5/ACF催化剂用于烟气低温脱硝的研究[J].环境化学,2009,1:26-30.Hou Yaqin,Huang Zhanggen,Ma Jianrong.Study on the activities of V_2O_5/ACF catalyst for the catalytic reduction of NO at low temperature[J].Environmental Chemistry,2009,1:26-30.(in Chinese)
[6]武建兵,王辉,秦张峰,等.V_2O_5/TiO_2-ZrO_2催化剂上甲醇选择氧化制甲缩醛[J].燃料化学学报,2011,1:64-68.Wu Jianbin,Wang Hui,Qin Zhangfeng,et al.Selective oxidation of methanol to dimethoxymethane over V_2O_5/TiO_2-ZrO_2 catalyst[J].Journal of Fuel Chemistry and Technology,2011,1:64-68.(in Chinese)
[7]焦峰斌,张亚平,沈凯,等.γ-Al_2O_3对SCR脱硝催化剂V_2O_5-WO_3/TiO_2的改性研究[J].燃料化学学报,2012(10):1258-1263.Jiao Fengbin,Zhang Yaping,Shen Kai,et al.γ-Al_2O_3 modification on V_2O_5-WO_3/TiO_2 catalyst for selective catalytic reduction(SCR)of NO[J].Journal of Fuel Chemistry and Technology,2012(10):1258-1263.(in Chinese)
[8]Perez Hernandez R,Mendoza Anaya D,Fernandez M E,et al.Synthesis of mixed ZrO_2-TiO_2 oxides by sol-gel:microstructural characterization and infrared spectroscopy studies of NO_x[J].Journal of Molecular Catalysis A:Chemical,2008,281(1):200-206.
[9]Mariscala R,Rojasa S.Support effects in Pt/TiO_2-ZrO_2 catalysts for NO reduction with CH_4[J].Catalysis Today,2002(75):385-391.
[10]王龙飞,张亚平,郭婉秋,等.WO_3/TiO_2-ZrO_2脱硝催化剂制备及其NH_3活化机理[J].化工学报,2015,10 3903-3910.Wang Longfei,Zhang Yaping,Guo Wanqiu,et al.Preparation of WO_3/TiO_2-ZrO_2 catalyst for selective catalytic reduction and mechanism of NH_3 activation[J].CIESC Journal,2015,10:3903-3910.(in Chinese)
[11]李鹏,张亚平,肖睿,等.整体式V_2O_5-WO_3/TiO_2-ZrO_2催化剂用于NH_3选择性催化还原NO_x[J].中南大学学报:自然科学版,2013,4:1719-1726.Li Peng,Zhang Yaping,Xiao Rui,et al.Selective catalytic reduction of NO_x with NH_3 over V_2O_5-WO/TiO_2-ZrO_2monolith catalysts[J].Journal of Central South University:Science and Technology Edition,2013,4:1719-1726.(in Chinese)
[12]卢熙宁,宋存义,童震松,等.结掺杂TiO_2负载锰铈氧化物低温催化还原NO_x[J].北京科技大学学报,2014,9:1222-1232.Lu Xining,Song Cunyi,Tong Zhensong,et al.Low-temperature catalytic reduction of nitrogen oxides over managanese-cerium composite oxides supported on zirconiumdoped titanium dioxide[J].Journal of University of Science and Technology Beijing,2014,9:1222-1232.(in Chinese)
[13]杨于兴,漆睿.X射线衍射分析[M].上海:上海交通大学出版社,1994:33.Yang Yuxing,Qi Rui.Analysis of X-ray Diffraction[M].Shanghai:Shanghai Jiaotong University Press,1994:33.(in Chinese)
[14]Bond G C,Tahir S f.Vanadium oxide monolayer catalysts prepartion,characterization and catalytic activity[J].Applied Catalysis A:General,1991,71(1):1-31.
[15]Wachs I E,Weckhuysen B M.Structure and reactivity of surface vanadium oxide species on oxide supports[J].Applied Catalysis A:General,1997,157(1/2):67?90.
[16]辛勤,罗孟飞.现代催化研究方法[M].北京:科学出版社,2009:83-88.Xin Qin,Luo Mengfei.Modern Catalytic Research Methods[M].Beijing:Science Press,2009:83-88.(in Chinese)
[17]Topsoe N Y,Topsoe H,Dumesic J A.Vanadia/titania catalysts for selective catalytic reduction(SCR)of nitric-oxide by ammonia:1.combined temperature-programmed in-situ FTIR and on-line mass-spectroscopy studies[J].Journal of Catalysis,1995,151(1):226-240.
[18]Pan S,Luo H,Li L,et al.H_2O and SO_2 deactivation mechanism of MnO_x/MWCNTs for low-temperature SCR of NO_x with NH_3[J]Journal of Molecular Catalysis A:Chemical,2013,377:154-161.
[19]Tsyganenko A A,Pozdnyakov D V,Filimonov V N.Infrared study of surface species arising from ammonia adsorption on oxide surfaces[J].Journal of Molecular Structure,1975,29(2):299-318.
[20]Sun D,Liu Q,Liu Z,et al.An in situ DRIFTS study on SCR of NO with NH_3 over V_2O_5/AC surface[J].Catalysis Letters,2009,132(1):122-126.
[21]Wu Z,Jiang B,Liu Y,et al.DRIFT study of manganese/titania-based catalysts for low-temperature selective catalytic reduction of NO with NH_3[J].Environmental Science and Technology,2007,41(16):5812-5817.