This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
A Comparison of Rate Laws for CO Oxidation Over Pt on Alumina
Annotation ability available
Sector:
Language:
English
Abstract
This study compares global rate expressions for CO oxidation over Pt/Al2O3 catalysts from the literature to a recent rate law based on a novel experimental approach. Our new method infers local values of reaction rates from measured concentration profiles along an enlarged isothermal catalytic passage at typical automotive exhaust conditions. Experimental uncertainties are relatively small, so parameters in the rate law can be assigned within close tolerances. Rate laws based on dual-site Langmuir Hinshelwood (LH) mechanisms correlate several of the available databases, including the new one. And activation energies for the CO-O2 reaction in several global rate laws agree with values reported in the surface science literature. However, assigned energies in the CO adsorption equilibrium constant are 25 to 35 kcal/mole lower than they should be. All of the most accurate global rate laws have coefficients for CO inhibition that are virtually independent of temperature, whereas energy parameters in the actual equilbrium constants are between 30 and 40 kcal/mole.
Simulated light off curves for a typical passage in a monolithic converter are shown to be very sensitive to the activation energy for the CO-O2 reaction, so it is reassuring that reported values based on different databases are consistent. They are also affected by different forms of the rate expressions, even among those that have the same regression coefficients. But this factor is secondary compared to the influence of activation energy.
Authors
Citation
Boehman, A., Niksa, S., and Moffatt, R., "A Comparison of Rate Laws for CO Oxidation Over Pt on Alumina," SAE Technical Paper 930252, 1993, https://doi.org/10.4271/930252.Also In
References
- Boehman, A. L. Niksa, S. Moffat, R. J. “Catalytic Oxidation of Carbon Monoxide in a Large Scale Planar Isothermal Passage” SAE 922332 1992
- Shishu, R. C. “Kinetics of Carbon-Monoxide Oxidation Over Platinum Catalyst,” University of Detroit 1972
- Voltz, S. E. Morgan, C. R. Liederman, D. Jacob, S. M. “Kinetic Study of Carbon Monoxide and Propylene Oxidation on Platinum Catalysts,” I&EC Prod. Res. Dev. 12 294 1973
- Hegedus, L. L. Oh, S. H. Baron, K. “Multiple Steady States in an Isothermal, Integral Reactor: The Catalytic Oxidation of Carbon Monoxide Over Platinum-Alumina,” AIChE J. 23 632 1977
- Montreuil, C. N. Williams, S. C. Adamczyk, A. A. “Modeling Current Generation Catalytic Converters: Laboratory Experiments and Kinetic Parameter Optimization - Steady State Kinetics,” SAE 920096 1992
- Paspek, S. C. Varma, A. Carberry, J. J. “Utilization of the Recycle Reactor in Determining Kinetics of Gas-Solid Catalytic Reactions,” Chem. Eng. Ed. 14 78 1980
- Young, L. C. “The Application of Orthogonal Collocation to Laminar Flow Heat and Mass Transfer in Monolith Converters,” University of Washington 1974
- Langmuir, I. “The Mechanism of the Catalytic Action of Platinum in the Reactions 2 CO + O 2 = 2 CO 2 and 2 H 2 + O 2 = 2 H 2 O,” Trans. Far. Soc. 17 827 1922
- Kuo, J. C. W. Morgan, C. R. Lassen, H. G. “Mathematical Modeling of CO and HC Catalytic Converter Systems,” SAE 710289 1971
- Subramaniam, B. Varma, A. “Reactions of CO, NO. O 2 and H 2 O on Three-Way and Pt/yAl 2 O 3 Catalysts,” Front.. Chem. Rec. Eng. 1 231 1984
- Boehman, A. L. “Catalytic Oxidation of Carbon Monoxide in a Large Scale Planar Isothermal Passage” Stanford University 1992
- Press, W. H. Flannery, B. P. Teukolsky, S. A. Vetterling, W. T. Numerical Recipes: The Art of Scientific Computing Cambridge University Press 498 1986
- Kee, R. J. Warnatz, J. Miller, J. A. “A FORTRAN Computer Code Package for the Evaluation of Gas-Phase Viscosities, Conductivites and Diffusion Coefficients” Sandia Report SAND83-8209 1983
- Engel, T. Ertl, G. “Elementary Steps in the Catalytic Oxidation of Carbon Monoxide on Platinum Metals,” Adv. Catal. 28 1 1979
- Yao, Y.-F. Y. “The Oxidation of CO and Hydrocarbons Over Noble Metal Catalysts,” J. Catal. 87 152 1984
- Bonzel, H. P. Ku, R. “Mechanisms of the Catalytic Carbon Monoxide Oxidation on Pt (110),” Surf. Sci. 33 91 1972
- Winterbottom, W. L. “Application of Thermal Desorption Methods in Studies of Catalysis: I. Chemisorption of Carbon Monoxide on Platinum,” Surf. Sci. 36 195 1973
- Winterbottom, W. L. “Application of Thermal Desorption Methods in Studies of Catalysis: II. The Oxidation of Carbon Monoxide on Platinum,” Surf. Sci 36 205 1973
- McCabe, R. W. Schmidt, L. D. “Binding States of CO on Single Crystal Planes of Pt” Surf. Sci. 66 101 1977
- Campbell, C. T. Ertl, G. Kuipcrs, H. Segner. J. “A Molecular Beam Study of the Catalytic Oxidation of CO on a Pt (111) Surface,” J. Chem. Phys. 73 5862 1980
- Oh, S. H. Hegedus, L. L. “Dynamics of High-Temperature Carbon Monoxide Chemisorption on Platinum-Alumina by Fast-Response IR Spectroscopy,” ACS Sym. Ser. 178 79 1982
- Racine, B. N. Herz, R. K. “Modeling Dynamic CO Oxidation over Pt/Al 2 O 3 : Effects of Intraplellet Diffusion and Site Heterogeneity” J. Catal. 137 158 1992
- Moffat, R. J. “Describing the Uncertainties in Experimental Results,” Exp. Therm. Fluid Sci. 1 3 1988
- Herz, R. K. Marin, S. P. “Surface Chemistry Models of Carbon Monoxide on Supported Platinum Catalysts” J. Catal. 65 281 1980
- Haaland, D. M. Williams, F. L. “Simultaneous Measurement of CO Oxidation Rate and Surface Coverage on Pt/Al 2 O 3 Using Infrared Spectroscopy: Rate Hysteresis and CO Island Formation,” J. Catal. 76 450 1982
- Oh, S. H. Fisher, G. B. Carpenter, J. E. Goodman, D. W. “Comparative Kinetic Studies of CO-O 2 and CO-NO Reactions Over Single Crystal and Supported Rhodium Catalysts,” J. Catal. 100 360 1986