Burger, L.

Deutschmann, O.

Maier, L.

English

KITopen

KIT – University of the State of Baden-Wuerttemberg andNational Research Center of the Helmholtz AssociationMolar net production rate:(heterogeneous reactions)Surface coverage: Rate expression:Oxidation and reforming of light hydrocarbons over platinum catalysts:  Development of a unified surface reaction mechanism Lea Burger1, Lubow Maier2, Olaf Deutschmann1-31 Institute of Chemical Technology and Polymer Chemistry2 Institute for Nuclear and Energy Technologies3 Institute for Catalysis Research and TechnologyIntroduction Modeling approachMethodsReforming and partial oxidation of hydrocarbons [1,2], combustion of natural gas [3,4], and the reduction of pollutant emissions from automobiles [5] are important examples for catalytic reactions over platinum.For a better understanding of the kinetics of the elementary-step reactions on platinum coated catalysts detailed modeling and simulation techniques are useful. A detailed surface mechanism is developed using numerous experimentally derived data.To set up a reliable unified surface mechanism of light hydrocarbons over platinum, we first established several sub-mechanisms (H2 /O2 , CO/O2 , CH4 /O2 ) applicable for a wide range of temperature and C/H/O ratios. Coupling of these mechanisms lead to an initial mechanism of Cn H2n - hydrocarbons. We expanded this mechanism by important side reactions and by coverage dependencies of activation energies.References:[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] O. Deutschmann, L. I. Maier, U. , A.H. Stroemman,  R.W. Dibble. 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 The developed C1-mechanism for oxidation and reforming reactions of CH4 are applicable to different reactors and experimental set-ups. The mechanism also describes the influence of adduct/product inflow in systems like CH4 /O2 + H2 O, CH4 /CO2 + H2 O, etc.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 45. Jahrestreffen Deutscher Katalytiker, March 14 – March 16, 2012Simulation Results[6] O. Deutschmann, S. Tischer et al., DETCHEM version 2.3, 2010, www.DETCHEM.com[7] R. H. Nibbelke, M. A. J. Campman, J. H. B. J.Hoebink, and G. B. Marin. Journal of Catalysis, 171, 1997, 358-373[8] M.E.S. Hegarty, A.M. O’Connnor, J.R.H. Ross. Catalysis Today 42, 1998, 225[9]. M.M.V.M. Souza, D.A.G. Aranda, M. Schmal. Journal of Catalysis 204, 2001, 498Acknowledgement:The authors would like to thank F. Schott for  the experimental results. Financial support by German Research Foundation (DFG) is gratefully acknowledged.sjkskNNjjKkiki cksg 'fs1expexpNiiiμiaβkf RTΘεΘRTETAk kkikkkInitial surface reaction mechanismSurface scienceTheoretic al studies (DFT, MC)Comparison of experiment and simulationRevised reaction mechanismSensitivity analysisNumerical simulationThermodynamic consistencyReactor models(including detailed gas chemistry and transport models) ii stComputational simulations are performed using the software package DETCHEM [6]. It contains routines for calculation of reaction rates and transport coefficients. Different reactor models, such as plug flow and packed bed, are implemented that resort to these routines. Lab experimentsExperimentsTo support the development of the mechanism, laboratory experiments were performed in a flow reactor.• Well-defined boundary conditions• 20g/ft³ loaded Pt/Al2 O3 monolith catalyst• Homogenous pulse free reactant flow  (2 – 4 slpm)• Analyzed by FTIR and MS Experimental data from Hegarty et al. [8]The unified C1-mechanism consists of 49 elementary-step reactions among 9 gas phase and 14 surface species. With these simulations we could figure out that the specific reactions of H2 O and CHx of the reforming mechanism works via the HCOO- intermediate. Experimental data from Deutschmann et al. [3]Experimental data from Nibbelke et al. [7]Experimental data from Souza et al. [9](Pt) + (Pt) + O2 ⇌ O(Pt) + O(Pt) H2 + (Pt) + (Pt) ⇌ H(Pt) + H(Pt) H + (Pt) → H(Pt) CH4 + (Pt)  + (Pt) ⇌ CH3(Pt)  + H(Pt) H2O + (Pt) ⇌ H2O(Pt) OH + (Pt) ⇌ OH(Pt) CO + (Pt) ⇌ CO(Pt) CO2 + (Pt) ⇌ CO2(Pt) CH3(Pt) + (Pt)  ⇌ CH2(Pt) + H(Pt) CH2(Pt) + (Pt)  ⇌ CH(Pt)  + H(Pt) CH(Pt)  + (Pt)   ⇌ C(Pt)   + H(Pt) H(Pt) + O(Pt) ⇌ OH(Pt) + (Pt) OH(Pt) + H(Pt) ⇌ H2O(Pt) + (Pt) OH(Pt) + OH(Pt) ⇌ H2O(Pt) + O(Pt) CO(Pt)  +O(Pt)   ⇌ CO2(Pt) +(Pt) C(Pt)   +O(Pt)  ⇌ CO(Pt)  +(Pt) CO(Pt) + OH(Pt) ⇌ COOH(Pt) + (Pt) CO(Pt) + OH(Pt) ⇌ HCOO(Pt) + (Pt) (Pt) + HCOO(Pt) ⇌ H(Pt) + CO2(Pt) CO2(Pt) + OH(Pt) ⇌ HCOO(Pt) + O(Pt) CO(Pt) + H(Pt) ⇌ HCO(Pt) + (Pt) CO(Pt) + OH(Pt) ⇌ CO2(Pt) + H(Pt) OH(Pt) + C(Pt) ⇌ H(Pt) + CO(Pt)…

Oxidation and reforming of light hydrocarbons over platinum catalysts: Development of a unified surface reaction mechanism

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Oxidation and reforming of light hydrocarbons over platinum catalysts: Development of a unified surface reaction mechanism

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