Burger, L.

Deutschmann, O.

Maier, L.

English

KITopen

Development of an unified surface reaction mechanism of oxidation and reforming reactions of light hydrocarbons over platinumLea Burger1, Lubow Maier2, Olaf Deutschmann1, 2 lea.burger@kit.edu1 Institute of Chemical Technology and Polymer Chemistry2 Institute for Nuclear and Energy TechnologiesIntroduction Numerical Model, DETCHEM PackageModel LevelmacroscopicWashcoat optionalPLUG 1D Plug FlowCHANNEL2D Parabolized Model MONOLITHTransient Temperature ProfileReforming and partial oxidation of hydrocarbons [1,2], combustion ofnatural gas [3,4], and the reduction of pollutant emissions fromautomobiles [5] are important examples for catalytic reactions overplatinum.The application of reliable and predictive modeling of technical reactorsused by CFD simulations calls for a better understanding of the kineticsand elementary-step reactions. A detailed surface mechanism isdeveloped against numerous experimentally derived data.PBED1D Packedbed ReactorDETCHEM-LibraryReaction MechanismsThermodynamic DataTransport CoefficientsmicroscopicModeling approachThe software DETCHEM [6] was applied for numerical simulation.Steady state and transient models of packed bed, channel andmonolithic reactors have been evaluated concerning their ability todescribe laboratory experiments specific.Should include allpossible paths forformation of thechemical speciesShould be applicableover a wide range ofconditionsNeeds to be evaluatedagainst numerousexperimentally deriveddataCrucial steps in themechanism ought to bedefineΓcΘ iiiσ=Surface coverageΓstΘ iii σ&=∂∂Rate expression∏=−=s1expexpNiiiµiaβkf RTΘεΘRTETAk kkikkkiiii cMRTSsπ2eff=&Adsorption• Adsorbates are assumed to be randomly distributed on the surface• Surface is viewed as being uniform; the local environment (edges, defects,  terraces, different structures) is not directly taken into accountComplexityThermodynamic ConsistencyKK +′′+′′←→+′+′ 22112211 AAAArfννννkkEquilibrium reactionreactionmechanism Thermo-dynamicallyconsistentmechanism Potentially inconsistent surfacereaction mechanismCalculate             for pairs ofreversible reactions( )TGR∆thermodynamics adjusted    knownthermodynamicsadjusted    known( )TiµSubstituteknownLinear equations forunknown( )TiµWeightedleast square fit for unknown           ( )TiµCalculate             from thermodynamicdata( )TGR∆Calculate rate coefficientsof reverse reactionsInitial surface reaction mechanismSurface scienceTheoretical studies (DFT, MC)Reactor models(including detailed gas chemistry and transport models)Comparison of experiment and simulationRevised reaction mechanismNumerical simulationMean field approximation( )( )( ) ( )( )∏∏′⊕′′⊕⊕ ∆−=iiiiiiccTRTGTkTkννRrf expKIT – University of the State of Baden-Wuerttemberg andNational Research Center of the Helmholtz AssociationExperimental CO oxidation results (dots) ofdifferent reactor systems were simulated (solidline) by corresponding DETCHEM software tools.3003504004505005506000 0.1 0.2 0.3 0.4 0.5 0.6 CO/(CO+O2)light-off temperature [K]SimulationExperiment 30 Torr Ar00.20.40.60.810 100 200 300 400 500temperature [K]conversion CO and selectivity simulated COconversionCO in pure N2Channel MonolithPackedbed00.20.40.60.81350 400 450 500temperature in Kconversion COexperimentalsimulationRef: Rinnemo et al.,1997 own experiment 2010Ref: Kahlich et al., 1997References:[1] R. Schwiedernoch, S. Tischer, C. Correa, O. Deutschmann, J. Warnatz. Proc Combust. Ind. 29, 2002, 1005[2] R. Quiceno, O. Deutschmann, J. Warnatz, J. Pérez-Ramírez. Catalysis Today 119, 2006, 311[3] Deutschmann, O.; Maier, L. I.; Riedel, U.; Stroemman, A. H.; Dibble, R. W. Catalysis Today 59, 2000, 141[4] M. Rinnemo, D. Kulginov, S.Johansson, K. L. Wong, V. P. Zhdanov, B. Kasemo, Surface Science, Vol. 376, 1997, 297[5] J. Koop, O. Deutschmann. Appl. Catal.B: Environmental 91, 2009, 47-58 [6] O. Deutschman et al., DETCHEM version 2.3, 2010, www.DETCHEM.comThe developed sub-mechanisms are applicable to different reactorsand experimental set-ups. The simulations conform to theexperimental data very well.Contact: L. Burger, O. Deutschmann, Institute for Chemical Technology and Polymer Chemistry, Engesserstraße 20, 76131 Karlsruhe, Germany. lea.burger@kit.edu, deutschmann@kit.edu Presented at 44. Jahrestreffen Deutscher Katalytiker, Weimar/Germany, März  16.-18., 2011Simulation Results00.010.020.030.040.050 3 6 9p CO [kPa]Rw(CO2) [mol kg-1 s-1] experimentalsimulation3503703904104304504704900.0% 0.2% 0.4% 0.6% 0.8% 1.0% 1.2%CO - concentration %outlet temperatur [K]ExperimentSimulation mit 16K Wärmeverlust0%20%40%60%80%100%350 370 390 410 430 450 470 490 510temperature [K]conversion COsimulationexperimentRef: Salomons et al., 2006Ref: Sun et al.,  2003Ref: Nibbelke et al., 1997Further sub-mechanisms are verified against experimental measurements for hydrogen oxidation, methane partial oxidation and steam reforming of methane to develop a unified surface mechanism. [7] S. Salomons, M. Votsmeier, R.E. Hayes, A. Drochner, H. Vogel, J. Grieshof, Catalysis Today, Vol. 117, 2006, 491-497[8] M. J. Kahlich, H. A. Gasteiger, R.J. Behm, Journal of Catalysis, Vol. 171, 1997, 93-105[9] R. H. Nibbelke, M. A. J. Campman, J. H. B. J. Hoebink, G. B. Marin, Journal of Catalysis, Vol 171, 1997, 358-373[10] M. Sun, E. B. Croiset, R. R. Hudgins, P. L. Silveston, M. Menzinger, Ind. Eng. Chem. Res., Vol. 42, 2003, 37-45[11] Rinnemo M., Fassihi M., Kasemo B. chem. phys. letters 211,1993, 60[12] Hegarty, M.E.S. et al. Catalysis Today 42, 1998, 225Acknowlegement:Florian Schott for the experimental results. CH4/O2H2/O2Ref: Rinnemo et al.,1993 Ref: Hegarty et al.,1998own experiment 2010CH4/H2O

Development of an unified surface reaction mechanism of oxidation and reforming reactions of light hydrocarbons over platinum

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Development of an unified surface reaction mechanism of oxidation and reforming reactions of light hydrocarbons over platinum

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