The effect of sodium on the Pd-catalyzed reduction of NO by methane

The kinetics of NO reduction by methane over Pd catalysts supported on 8 mol% yttria-stabilised zirconia (YSZ) has been studied at atmospheric pressure in the 620‐770 K temperature range. Langmuir‐Hinshelwood type kinetics are found with characteristic rate maxima reflecting competitive adsorption of NO and methane: NO adsorption is much more pronounced than that of methane within the temperature range of this investigation. Pd is an effective catalyst: 100% selectivity towards N2 can be achieved at 100% conversion of NO over this wide temperature range. Sodium causes strong poisoning of the reaction. The response of the system to variations in NO and methane concentrations, temperature, and sodium loading indicate that this is due to the Na-induced enhancement of NO chemisorption and dissociation relative to methane adsorption, i.e. sodium enhances oxygen poisoning of the catalyst. These results stand in revealing contrast to the strong promotional effect of sodium in the reduction of NO by propene over the same catalysts. The very different response of the two hydrocarbon reductants to Na doping of the Pd catalyst receives a consistent explanation. # 1998 Elsevier Science B.V. All rights reserved.

[1]  M. Pessa,et al.  Activated adsorption of methane on clean and oxygen-modified Pt{111} and Pd{110} , 1997 .

[2]  Shinya Sato,et al.  Iron ion-exchanged zeolite: the most active catalyst at 473 K for selective reduction of nitrogen monoxide by ethene in oxidizing atmosphere , 1992 .

[3]  T. Watling,et al.  The difference between alkanes and alkenes in the reduction of NO by hydrocarbons over Pt catalysts under lean-burn conditions , 1997 .

[4]  R. M. Lambert,et al.  In Situ Electrochemical Promotion by Sodium of the Platinum-Catalyzed Reduction of NO by Propene , 1997 .

[5]  M. Sasaki,et al.  Selective reduction of nitrogen monoxide with propane over alumina and HZSM-5 zeolite : Effect of oxygen and nitrogen dioxide intermediate , 1991 .

[6]  Shuichi Kagawa,et al.  Catalytic decomposition of nitric oxide over copper(II)-exchanged, Y-type zeolites , 1981 .

[7]  A. Ramli,et al.  A kinetic investigation of the reduction of NO by CH4 on silica and alumina-supported Pt catalysts , 1998 .

[8]  M. Pessa,et al.  Influence of preadsorbed oxygen on activated chemisorption of methane on Pd(110) , 1996 .

[9]  M. McCoustra,et al.  Impact-induced dissociation of methane and ethane on Pt(111) and Pt0.25Rh0.75(111) , 1996 .

[10]  J. Nørskov,et al.  Electrostatic adsorbate-adsorbate interactions: The poisoning and promotion of the molecular adsorption reaction , 1985 .

[11]  M. Vannice,et al.  NO decomposition and reduction by CH4 over Sr/La2O3 , 1996 .

[12]  D. Goodman,et al.  The effect of particle size on nitric oxide decomposition and reaction with carbon monoxide on palladium catalysts , 1994 .

[13]  M. McCoustra,et al.  Dissociative adsorption of methane on Pt(111) induced by hyperthermal collisions , 1993 .

[14]  Kathleen C. Taylor.  Nitric oxide catalysis in automotive exhaust systems , 1993 .

[15]  R. M. Lambert,et al.  Promotion by sodium in emission control catalysis : A kinetic and spectroscopic study of the Pd-catalyzed reduction of NO by propene , 1998 .

[16]  L. Xia,et al.  THE ROLE OF SURFACE CORRUGATION IN DIRECT TRANSLATIONALLY ACTIVATED DISSOCIATIVE ADSORPTION , 1994 .

[17]  J. Armor,et al.  Selective catalytic reduction of NOx with methane over metal exchange zeolites , 1993 .

[18]  D. Goodman,et al.  A Comparative Study of the Coadsorption of carbon monoxide and nitric oxide on Pd(100), Pd(111), and Silica-Supported Palladium Particles with Infrared Reflection-Absorption Spectroscopy , 1994 .

[19]  D. Goodman,et al.  BASIS FOR THE STRUCTURE SENSITIVITY OF THE CO+NO REACTION ON PALLADIUM , 1996 .

[20]  M. Pessa,et al.  Dissociative chemisorption of methane on clean and oxygen precovered Pt(111) , 1996 .

[21]  X. Verykios,et al.  Support-induced promotional effects on the activity of automotive exhaust catalysts1. The case of oxidation of light hydrocarbons (C2H4) , 1997 .

[22]  H. Miki,et al.  Chemisorption of NO on Pd(100), (111) and (110) surfaces studied by AES, UPS and XPS , 1991 .

[23]  D. Resasco,et al.  Conversion of nitric oxide and methane over Pd/ZSM-5 catalysts in the absence of oxygen , 1995 .

[24]  A. Bell,et al.  NO Adsorption, Desorption, and Reduction by CH4 over Mn-ZSM-5 , 1997 .

[25]  M. D. Amiridis,et al.  The selective catalytic reduction of NO by propylene over Pt supported on dealuminated Y zeolite , 1997 .

[26]  L. Prati,et al.  Catalytic dehydrohalogenation of polychlorinated biphenyls Part II: Studies on a continuous process , 1997 .

[27]  J. Armor,et al.  Metal exchanged ferrierites as catalysts for the selective reduction of NOx with methane , 1993 .

[28]  M. Vannice,et al.  The Kinetics of NOxDecomposition and NO Reduction by CH4overLa2O3and Sr/La2O3 , 1996 .

[29]  S. Sciré,et al.  Selective catalytic reduction of nitric oxide with ethane and methane on some metal exchanged ZSM-5 zeolites , 1994 .

[30]  C. Mullins,et al.  Trapping-mediated and direct dissociative chemisorption of methane on Ir(110): A comparison of molecular beam and bulb experiments , 1997 .

[31]  J. Armor,et al.  Catalytic reduction of nitrogen oxides with methane in the presence of excess oxygen , 1992 .

[32]  C. Vayenas,et al.  Non-faradaic electrochemical modification of catalytic activity: A status report , 1992 .

[33]  M. Vannice,et al.  NO Adsorption, Decomposition, and Reduction by Methane over Rare Earth Oxides , 1995 .

[34]  R. M. Lambert,et al.  Chemisorption and reactivity of nitric oxide on Na-dosedplatinum{111} , 1997 .

[35]  R. M. Lambert,et al.  Electrochemical Promotion in Emission Control Catalysis: The Role of Na for the Pt-Catalysed Reduction of NO by Propene , 1998 .

[36]  Robert J. Kudla,et al.  Removal of methane from compressed natural gas fueled vehicle exhaust , 1992 .

[37]  A. Ramli,et al.  A comparative investigation of the reduction of NO by CH4 on Pt, Pd, and Rh catalysts , 1998 .

[38]  Hidenori Yahiro,et al.  Cu-ZSM-5 zeolite as highly active catalyst for removal of nitrogen monoxide from emission of diesel engines , 1991 .