The Oxidation of Carbon Monoxide

These facts indicate that the carbon monoxide must be held simultaneously by both metal and oxygen atoms. Thus, the adsorbed molecule must be represented as 

It will be evident, from the limited number of items discussed above, that the study of the geometry of catalytic surfaces and of molecules adsorbed on them is in a very early stage of development. It may, therefore, be useful to indicate a few directions in which further practical and theoretical advances may be expected. In extending the examination of catalysts. 

On the theoretical side also, importance must be attached to oxides and sulfides because these present many problems which do not arise with metallic catalysts. The function of the oxygen and sulfur atoms in such lattices is a matter of prime importance, and structures produced by partial removal of these elements from their compounds must have very special properties. It would be of great interest to know, for example, in what positions the hydrogen atoms split off during ring-closure of aliphatic hydrocarbons are adsorbed on the catalyst it seems highly probable that the oxygen atoms in the chromium oxide or molybdenum oxide are involved and that they contribute an essential part to the specific effects of these catalysts. 

In many instances, as, for example, in the production of ethylene oxide by oxidation of ethylene with silver catalysts (Twigg, 39), the reaction takes place by collision with chemisorbed oxygen. It is, however, quite likely that instances will be found where the mechanism is entirely different and where two-point adsorption takes place. 

These few suggestions will indicate that a better knowledge of the geometrical factors in catalysis can only be obtained by the combined results of several distinct methods of theoretical and practical treatment. One of the most important of these is to increase the information available about the nature of the bond between the adsorbed molecule and the catalyst, and about its dependence on the chemical properties of the catalyst elements. 

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Other important uses of stannic oxide are as a putty powder for polishing marble, granite, glass, and plastic lenses and as a catalyst. The most widely used heterogeneous tin catalysts are those based on binary oxide systems with stannic oxide for use in organic oxidation reactions. The tin—antimony oxide system is particularly selective in the oxidation and ammoxidation of propylene to acrolein, acryHc acid, and acrylonitrile. Research has been conducted for many years on the catalytic properties of stannic oxide and its effectiveness in catalyzing the oxidation of carbon monoxide at below 150°C has been described (25). 

A variety of instmments are available to analyze carbon monoxide in gas streams from 1 ppm to 90%. One group of analyzers determines the concentration of carbon monoxide by measuring the intensity of its infrared stretching frequency at 2143 cm . Another group measures the oxidation of carbon monoxide to carbon dioxide electrochemically. Such instmments are generally lightweight and weU suited to appHcations requiring portable analyzers. Many analyzers are equipped with alarms and serve as work area monitors. 

CO Oxidation Catalyzed by Palladium. One of the best understood catalytic reactions occurring on a metal surface is the oxidation of carbon monoxide on palladium ... 

E. V. Albano. Monte Carlo simulation of the oxidation of carbon monoxide on fractal surfaces. Surf Sci 255 351-359, 1990. 

Perhaps the most familiar example of heterogeneous catalysis is the series of reactions that occur in the catalytic converter of an automobile (Figure 11.12). Typically this device contains 1 to 3 g of platinum metal mixed with rhodium. The platinum catalyzes the oxidation of carbon monoxide and unburned hydrocarbons such as benzene, C6H6 ... 

Catalysts in an oxidized state showed high activity in the oxidation of carbon monoxide [nickel catalysts (146) ] and hydrogen [molybdenum catalysts (146a)]. 

Kolbel et al. (K16) examined the conversion of carbon monoxide and hydrogen to methane catalyzed by a nickel-magnesium oxide catalyst suspended in a paraffinic hydrocarbon, as well as the oxidation of carbon monoxide catalyzed by a manganese-cupric oxide catalyst suspended in a silicone oil. The results are interpreted in terms of the theoretical model referred to in Section IV,B, in which gas-liquid mass transfer and chemical reaction are assumed to be rate-determining process steps. Conversion data for technical and pilot-scale reactors are also presented. 

The second step is the oxidation of carbon monoxide to carbon dioxide ... 

Drivers for Performing the Oxidation of Carbon Monoxide to Carbon Dioxide... 

Haruta, M., Kobayashi, T, Sano, H. and Yamada, N. (1987) Novel Gold Catalysts for the Oxidation of Carbon Monoxide at a Temperature far Below 0°. Chemistry Letters, 16, 405-408. 

Mechanisms of the Oxidation of Carbon Monoxide and Small Organic Molecules at Metal Electrodes... 

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. 

McCallum C, Pletcher D, 1978. An investigation of the mechanism of the oxidation of carbon monoxide adsorbed onto a smooth Pt electrode in aqueous acid. J Electroanal Chem 70 277. 

Watanabe M, Motoo S. 1975a. Electrocatalysis by ad-atoms. Part in. Enhancement of the oxidation of carbon monoxide on platinum by mthenium ad-atoms. J Electroanal Chem 60 275-283. 

Gibbs TK, McCallum C, Pletcher D. 1977. The oxidation of carbon monoxide at platinum and gold metallized membrane electrodes. Electrochim Acta 22 525-530. 

Since much of the impetus for our STM studies stems from earlier spectroscopic investigations of alkali metals and alkali metal-modified surfaces,6 we consider first what was learnt from the caesiated Cu(l 10) surface concerning the role of different oxygen states, transient and final states, in the oxidation of carbon monoxide, and then examine how structural information from STM can relate to the chemical reactivity of the modified Cu(110) surface. 

It is true, however, that many catalytic reactions cannot be studied conveniently, under given conditions, with usual adsorption calorimeters of the isoperibol type, either because the catalyst is a poor heat-conducting material or because the reaction rate is too low. The use of heat-flow calorimeters, as has been shown in the previous sections of this article, does not present such limitations, and for this reason, these calorimeters are particularly suitable not only for the study of adsorption processes but also for more complete investigations of reaction mechanisms at the surface of oxides or oxide-supported metals. The aim of this section is therefore to present a comprehensive picture of the possibilities and limitations of heat-flow calorimetry in heterogeneous catalysis. The use of Calvet microcalorimeters in the study of a particular system (the oxidation of carbon monoxide at the surface of divided nickel oxides) has moreover been reviewed in a recent article of this series (19). 

Heat-flow calorimetry may be used also to detect the surface modifications which occur very frequently when a freshly prepared catalyst contacts the reaction mixture. Reduction of titanium oxide at 450°C by carbon monoxide for 15 hr, for instance, enhances the catalytic activity of the solid for the oxidation of carbon monoxide at 450°C (84) and creates very active sites with respect to oxygen. The differential heats of adsorption of oxygen at 450°C on the surface of reduced titanium dioxide (anatase) have been measured with a high-temperature Calvet calorimeter (67). The results of two separate experiments on different samples are presented on Fig. 34 in order to show the reproducibility of the determination of differential heats and of the sample preparation. 

Figure 1.1 Schematic representation of a well known catalytic reaction, the oxidation of carbon monoxide on noble metal catalysts CO + Vi 02 —> C02. The catalytic cycle begins with the associative adsorption of CO and the dissociative adsorption of 02 on the surface. As adsorption is always exothermic, the potential energy decreases. Next CO and O combine to form an adsorbed C02 molecule, which represents the rate-determining step in the catalytic sequence. The adsorbed C02 molecule desorbs almost instantaneously, thereby liberating adsorption sites that are available for the following reaction cycle. This regeneration of sites distinguishes catalytic from stoichiometric reactions.

CODHs catalyse the oxidation of carbon monoxide in a reversible, two-electron process. They are homodimeric enzymes with five metal clusters, two C-clusters that catalyse the oxidation of CO to C02 and three typical [Fe4S4] cubane clusters (Figure 15.4). 

The oxidation of carbon monoxide, 2CO + 02 — C02 is one of the reactions (apart from reduction of nitric oxides and oxidation of unbumt hydrocarbons) taking place in the car exhaust catalyst. The latter consists of small noble metal particles (Pt, Rh or Pd) on a ceramic support. The reaction proceeds through the following steps [25]... 

Early experimental work on the oxidation of carbon monoxide was confused by the presence of any hydrogen-containing impurity. The rate of CO oxidation in the presence of species such as water is substantially faster than the bone-dry condition. It is very important to realize that very small quantities of hydrogen, even of the order of 20 ppm, will increase the rate of CO oxidation substantially [8], Generally, the mechanism with hydrogen-containing compounds present is referred to as the wet carbon monoxide condition. 

M. Haruta, T. Kobayashi, H. Sano, and N. Yamada, Novel gold catalysts for the oxidation of carbon monoxide at a temperature far below 0°C, Chem. Lett. 2, 405 08 (1987). 

Previous studies in conventional reactor setups at Philip Morris USA have demonstrated the significant effectiveness of nanoparticle iron oxide on the oxidation of carbon monoxide when compared to the conventional, micron-sized iron oxide, " as well as its effect on the combustion and pyrolysis of biomass and biomass model compounds.These effects are derived from a higher reactivity of nanoparticles that are attributed to a higher BET surface area as well as the coordination of unsaturated sites on the surfaces. The chemical and electronic properties of nanoparticle iron oxide could also contribute to its higher reactivity. In this work, we present the possibility of using nanoparticle iron oxide as a catalyst for the decomposition of phenolic compounds. 

Cherian, M. A., P. Rhodes, R. J. Simpson, and G. Dixon-Lewis. 1981. Kinetic modelling of the oxidation of carbon monoxide in flames. 18th Symposium (International) on Combustion Proceedings. Pittsburgh, PA The Combustion Institute. 385-96. 

According to the authors cited above, equation (16) holds for the decomposition of hydrogen iodide on platinum and of nitrous oxide on gold, and furthermore, according to Schwab and Drikos (12), for the oxidation of carbon monoxide to carbon dioxide on copper oxide. 

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