PdO/Sn_xCe_yO_2催化剂的CO氧化性能研究
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摘要
采用共沉淀-浸渍法制备PdO/Sn_xCe_yO_2催化剂,通过XRD、N_2吸附-脱附、CO-TPD和CO-DRIFT对催化剂的物相结构和表面性质进行表征和分析,并考察了催化剂的CO催化氧化活性。研究表明,催化剂的低温CO氧化活性与比表面积无关,而与表面晶格氧的活泼程度有直接关系。与富Sn催化剂Pd/Sn_(0.7)Ce_(0.3)O_2相比,富Ce催化剂Pd/Sn_(0.3)Ce_(0.7)O_2上的表面晶格氧更活泼,对低温CO的氧化起到了关键作用。CO-DRIFT结果显示,CO可以在室温下还原PdO,生成Pd~0和Pd~+。CO的吸附以Pd~0位上的线式吸附为主。相较于惰性预处理方法,氧化预处理有利于促进吸附CO的氧化,减少表面碳酸盐的生成。
The PdO/Sn_xCe_yO_(2 )catalysts were synthesized by the co-precipitation-impregnation method.XRD,N_2adsorption-desorption,CO-TPD and CO-DRIFT techniques were used to investigate the structural and surface properties of the catalysts,and their catalytic activity by CO oxidation were evaluated.The results show that the CO oxidation activity of the catalysts is irrelevant with the surface area,but directly correlates with the reactivity of surface lattice oxygen species.Compared with the Pd/Sn_(0.7)Ce_(0.3)O_2catalyst,the higher reactivity of surface lattice oxygen species on the Pd/Sn_(0.3)Ce_(0.7)O_2catalyst plays a vital role in better CO oxidation performance at low temperatures.The in-situ DRIFT spectra of CO adsorption show that,the PdO species can be reduced by CO even at room temperature and form the Pd~0/Pd~+species.The linearly bonded CO-Pd~0is the dominate adsorption species.Furthermore,compared with the inert pre-treatment method,the oxidative pre-treatment method facilitates the oxidation of CO and decreases the formation of carbonates.
The PdO/Sn_xCe_yO_(2 )catalysts were synthesized by the co-precipitation-impregnation method.XRD,N_2adsorption-desorption,CO-TPD and CO-DRIFT techniques were used to investigate the structural and surface properties of the catalysts,and their catalytic activity by CO oxidation were evaluated.The results show that the CO oxidation activity of the catalysts is irrelevant with the surface area,but directly correlates with the reactivity of surface lattice oxygen species.Compared with the Pd/Sn_(0.7)Ce_(0.3)O_2catalyst,the higher reactivity of surface lattice oxygen species on the Pd/Sn_(0.3)Ce_(0.7)O_2catalyst plays a vital role in better CO oxidation performance at low temperatures.The in-situ DRIFT spectra of CO adsorption show that,the PdO species can be reduced by CO even at room temperature and form the Pd~0/Pd~+species.The linearly bonded CO-Pd~0is the dominate adsorption species.Furthermore,compared with the inert pre-treatment method,the oxidative pre-treatment method facilitates the oxidation of CO and decreases the formation of carbonates.
引文
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[2]MENG L,LIN J J,PU Z Y,et al.Identification of active sites for CO and CH4oxidation over PdO/Ce1-xPdx O2-δcatalysts[J].Applied Catalysis B:Environmental,2012,119/120:117-122.
[3]HU Z,LIU X,MENG D,et al.Effect of ceria crystal plane on the physico-chemical and catalytic properties of Pd/Ceria for CO and propane oxidation[J].ACS Catalysis,2016,6(4):2265-2279.
[4]KIM C,NOH M,CHOI M,et al.Critical size of a nano SnO2electrode for Li-secondary battery[J].Chemistry of Materials,2005,17(12):3297-3301.
[5]CHAPPEL S,CHEN S G,ZABAN A,TiO2-coated nanoporous SnO2electrodes for dye-sensitized solar cells[J].Langmuir,2002,18(8):3336-3342.
[6]GUBBALA S,CHAKRAPANI V,KUMAR V,et al.Band-edge engineered hybrid structures for dye-sensitized solar cells based on SnO2nanowires[J].Advanced Functional Materials,2008,18(16):2411-2418.
[7]SHINDE V M,MADRAS G.Kinetics of carbon monoxide oxidation with Sn0.9M0.05O2-δ(M=Cu,Fe,Mn,Co)catalysts[J].Catalysis Science&Technology,2012,2(2):437-446.
[8]XU X,ZHANG R,ZENG X,et al.Effects of La,Ce,and Y Oxides on SnO2Catalysts for CO and CH4 Oxidation[J].Chemical Catalyst and Chemistry,2013,5(7):2025-2036.
[9]WANG S,HUANG J,ZHAO Y,et al.Preparation,characterization and catalytic behavior of SnO2supported Au catalysts for low-temperature CO oxidation[J].Journal of Molecular Catalysis A:Chemical,2006,259(1):245-252.
[10]YE Q,WANG J,ZHAO J,et al.Pt or Pd-doped Au/SnO2catalysts:High activity for low-temperature COoxidation[J].Catalysis Letters,2010,138(1/2):56-61.
[11]李静,柴澍靖,李新刚.SnO2-CeO2催化剂的合成及其CO氧化性能[J].化学工业与工程,2017,34(6):1-5.
[12]GURBANI A,AYASTUY J L,GONZLEZ-MAR-COS M P,et al.Comparative study of CuO-CeO2catalysts prepared by wet impregnation and deposition-precipitation[J].International Journal of Hydrogen Energy,2009,34(1):547-553.
[13]YAO X,YU Q,JI Z,et al.A comparative study of different doped metal cations on the reduction,adsorption and activity of CuO/Ce0.67 M0.33O2(M=Zr4+,Sn4+,Ti 4+)catalysts for NO+CO reaction[J].Applied Catalysis B:Environmental,2013,130:293-304.
[14]YU Q,WU X,TANG C,et al.Textural,structural,and morphological characterizations and catalytic activity of nanosized CeO2-MOx(M=Mg2+,Al 3+,Si 4+)mixed oxides for CO oxidation[J].Journal of Colloid and Interface Science,2011,354(1):341-352.
[15]ZHU X,GAO X,QIN R,et al.Plasma-catalytic removal of formaldehyde over Cu-Ce catalysts in a dielectric barrier discharge reactor[J].Applied Catalysis B:Environmental,2015,170:293-300.
[16]YAO X,GAO F,YU Q,et al.NO reduction by COover CuO-CeO2catalysts:effect of preparation methods[J].Catalysis Science&Technology,2013,3(5):1355-1366.
[17]BAE J,KIM J,JEONG H,et al.CO oxidation on SnO2surfaces enhanced by metal doping[J].Catalysis Science&Technology,2018,8(3):782-789.
[18]PRIOLKAR K R,BERA P,SARODE P R,et al.Formation of Ce1-xPdxO2-δsolid solution in combustion-synthesized Pd/CeO2 catalyst:XRD,XPS,and EXAFS investigation[J].Chemistry of Materials,2002,14(5):2120-2128.
[19]SU Y Q,LIU J X,FILOT I A W,et al.Highly active and stable CH4 oxidation by substitution of Ce4+by two Pd2+ions in CeO2(111)[J].ACS Catalysis,2018,8(7):6552-6559.
[20]SATSUMA A,OSAKI K,YANAGIHARA M,et al.Low temperature combustion over supported Pd catalysts-Strategy for catalyst design[J].Catalysis Today,2015,258(1):83-89.
[21]SASMAZ E,WANG C,LANCE M J,et al.In situ spectroscopic investigation of a Pd local structure over Pd/CeO2and Pd/MnOx-CeO2during CO oxidation[J].Journal of Materials Chemistry A,2017,5(25):12998-13008.
[22]JEONG H,BAE J,HAN J W,et al.Promoting effects of hydrothermal treatment on the activity and durability of Pd/CeO2catalysts for CO oxidation[J].ACS Catalysis,2017,7(10):70977105.
[23]XU J,OUYANG L,MAO W,et al.Operando and kinetic study of low-temperature,lean-burn methane combustion over a Pd/γ-Al2O3catalyst[J].ACS Catalysis,2012,2(2):261-269.
[24]WANG C,SASMAZ E,WEN C,et al.Pd supported on SnO2-MnOx-CeO2catalysts for low temperature COoxidation[J].Catalysis Today,2015,258(2):481-486.