Kinetics of carbon monoxide oxidation

It has been stressed in Section 1.4 that a knowledge of the reaction kinetics, especially of the orders of reaction, is an essential ingredient of any discussion of mechanism. Few measurements of this kind have however been reported and the results are not in good agreement (Table 6.3). Orders in both reactants lie between 0.05 and 0.46, implying moderate to strong chemisorption the absence of negative orders shows that neither is so 

deposition-precipitation IMP, impregnation with chloroauric acid, unless specified LTR, low-temperature reduction under H2 at 473 K HTR, high-temperature reduction at 773 K C, air treatment at 673 K. 

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K. Grass and H. G. Lintz, The kinetics of carbon monoxide oxidation on tin(TV) oxide supported platinum catalysts, J. Catal. 172, 446-452 (1997). 

Howard J.B., Williams G.C., Fine D.H.. (1973) Kinetics of Carbon Monoxide Oxidation in Postflame Gases. // Symposium (Int.) on Combustion, Combustion Institute Pittsburgh... 

Howard J., Williams G., Fine D. (1973) Kinetics of carbon monoxide oxidation in postflame gases. 14 Symposium (Intemat.) on Combustion. The Combustion Institute, Pittsburgh, 975-986... 

Almost all catalytic converters have to contend with the decay or poisoning of the catalyst In some form and the catalytic monolith Is no exception. Indeed this Is notorious In the automotive application where the catalytic converter must survive 50,000 miles of operation and still perform adequately. Although we shall use the kinetics of carbon monoxide oxidation over a platinum catalyst as an obvious and Important example, our main objective Is to develop a model which can handle any catalyst decay question and to point out the differences In two types of poisoning. Thus our study comes within the third main division of the subject as laid out by Butt (1 ) In 1972 not the mechanism or rate determination but the effect of deactivation on the operation of the reactor. 

Berlowitz PJ, Peden CHF, Goodman DW (1988) Kinetics of carbon monoxide oxidation on single-crystal palladium, platinum, and iridium. J Phys Chem 92 5213-5221... 

The purpose of this article is to review the results of transient low pressure studies of carbon monoxide oxidation over transition metal substrates. Particular emphasis is given to the use of in-situ electron spectroscopy, flash desorption, modulated beam and titration techniques. The strengths and weaknesses of these will be assessed with regard to kinetic insight and quantification. An attempt will be made to identify questions that are ripe for investigation. Although not limited to it, the presentation emphasizes our own work. A very recent review of the carbon monoxide oxidation reaction C l) will be useful to readers who are interested in a more comprehensive view. 

Helling and Tester (1987) reported the oxidation kinetics of carbon monoxide over the temperature range 420 to 570°C at a pressure of 246 bar (24.6 MPa). Holgate and Tester (1994) examined oxidation kinetics of carbon monoxide. In addition to direct oxidation with oxygen, Helling and Tester found that the reaction of carbon monoxide with water was significant, as the following equations show ... 

The effects of temperature and concentration on direct and indirect oxidation kinetics of carbon monoxide were correlated with global models. In 1986, Helling and Tester found the oxidation of carbon monoxide to be globally first order in carbon monoxide and independent of oxygen concentration over the range investigated. 

Helling, R.K. Tester, J.W. Oxidation Kinetics of Carbon Monoxide in Supercritical Water, Energy and Fuels, 1 (1987) 417-423. 

Seravalli, J., Kumar, M., Lu, W.-P., and Ragsdale, S. W., 1997, Mechanism of carbon monoxide oxidation by the carbon monoxide dehydrogenase/acetyl-CoA syndiase from Clostridium thermoaceticum Kinetic characterization of the intermediates, Biochem. 36 11241fi 11251. 

Gavril, D. Katsanos, N.A. Karaiskakis, G. Gas chromatographic kinetic study of carbon monoxide oxidation over platinum-rhodium catalysts. J. Chromatogr., A 1999, 852, 507-523. 

Catalytic properties in the reactions of carbon monoxide oxidation (all oxides) and butene oxidative dehydrogenation (iron oxides) were studied using a microreactor with the vibrofluidized bed of catalysts and pulse/flow kinetic installation [4], Catalytic activities were characterized by the reaction rate W (molec. COWs) in differential conditions and first-order rate constant K (dm butene (STP) /m -s-atm), respectively. 

One of the inconveniences of TS-PFR methods is that it is difficult, in fact impossible, to compare conversions calculated using the fitted rate expression with raw TS-PFR data. This point was raised previously in connection with the investigation of carbon monoxide oxidation. One can simulate kinetic behaviour using the above equations and parameters to produce the expected isothermal behaviour of the system but not that observed in the experimental results that are obtained from the TS-PFR during temperature ramping. This is unavoidable and results from our lack of knowledge of the axial temperature profile in the experimental set-up. 

The kinetics of carbon monoxide and dioxide generation in the oxidation of cyclohexanone labelled with a 14C carbonyl group has been investigated [279]. It was suggested that CO and C02 were formed by the decay of acyl and acyl peroxy radicals. 

Source From Gas chromatographic kinetic study of carbon monoxide oxidation over platinum-rhodium catalysts, in J. Chromatogr. 

Fig. 4 Energy distribution function, (p(e t) (cmol/kJ/mol/), against the dimensionless product of the lateral interaction energy (P) and the local isotherm (0)P0, for carbon monoxide adsorption over a bimetalhc Pto.25-Rho.75 silica supported catalyst, at 698 K. Source From Gas chromatographic kinetic study of carbon monoxide oxidation over platinum-rhodium catalysts, in J. Chromatogr.

Bohlbro, H. An Investigation on the Kinetics of Carbon Monoxide with Water Vapour over Iron Oxide Based Catalyst, Gjellerup, Copenhagen, 1966, chapt. 7 Section 1.5.2)... 

Isothermal kinetic studies of carbon monoxide oxidation... 

Hueso, J. L. Martinez-Martinez, D. Caballero, A. et al. Near-ambient X-ray photoemission spectroscopy and kinetic approach to the mechanism of carbon monoxide oxidation over lanthanum substituted cobaltites. Catal. Commun. 2009, 10, 1898-1902. 

In this chapter, we have summarized (recent) progress in the mechanistic understanding of the oxidation of carbon monoxide, formic acid, methanol, and ethanol on transition metal (primarily Pt) electrodes. We have emphasized the surface science approach employing well-defined electrode surfaces, i.e., single crystals, in combination with surface-sensitive techniques (FTIR and online OEMS), kinetic modeling and first-principles DFT calculations. 

Just as in gas phase kinetics, reactive molecular beam-surface scattering is providing important molecular level insight into reaction dynamics. There is no surface reaction for which such studies have proven more illuminating than the carbon monoxide oxidation reaction. For example Len, Wharton and co-workers (23) found that the product CO exits a 700K Pt surface with speeds characteristic of temperatures near 3000K. This indicates that the CO formed by the reactive encounter of adsorbed species is hurled off the surface along a quite repulsive potential. 

Fluidised catalysts are also used in the synthesis of high-grade fuels from mixtures of carbon monoxide and hydrogen, obtained either by coal carbonisation or by partial oxidation of methane. An important application in the chemical industry is the oxidation of naphthalene to phthalic anhydride, as discussed by Riley(131). The kinetics of this reaction are much slower than those of catalytic cracking, and considerable difficulties have been experienced in correctly designing the system. 

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