CO oxidation catalyst

Catalyst contamination from sources such as turbine lubricant and boiler feed water additives is usuaUy much more severe than deactivation by sulfur compounds in the turbine exhaust. Catalyst formulation can be adjusted to improve poison tolerance, but no catalyst is immune to a contaminant that coats its surface and prevents access of CO to the active sites. Between 1986 and 1990 over 25 commercial CO oxidation catalyst systems operated on gas turbine cogeneration systems, meeting both CO conversion (40 to 90%) and pressure drop requirements. 

Effect of ozone pretreatment on low temperature CO oxidation catalysts... 

Titanium dioxide supported gold catalysts exhibit excellent activity for CO oxidation even at temperatures as low as 90 K [1]. The key is the high dispersion of the nanostructured gold particles over the semiconducting Ti02 support. The potential applications of ambient temperature CO oxidation catalysts include air purifier, gas sensor and fuel cell [2]. This work investigates the effects of ozone pretreatment on the performance of Au/Ti02 for CO oxidation. 

The objective of this study was to develop a low temperature CO oxidation catalyst that continually removes low concentrations of CO from the atmospheres of space stations. CO is a major contaminant in spacecraft environments. Since... 

The CiijCe, r02 v nanostructuied catalyst prepared by the sol-gel method is a very efficient and selective CO oxidation catalyst even under the highly reducing conditions which are present in a PrOX reactor. It is energy efficient toward the PEM fuel cell technology, because it oxidizes CO... 

R G. Harrison, I. K. Ball, W. Azelee, W. Daniell, and D. Goldfarb, Nature and surface redox properties of copper(ll)-promoted cerium(lV) oxide CO oxidation catalysts, Chem. Mater. 12, 3715-3725 (2000). 

CO oxidation catalyst, 45 CO oxidation reaction, 50 Co silicide nanoparticles, 155 CO stretching frequencies,... 

Zhou S, Yin H, Wu Z et al (2008) NiAu alloy nanoparticles for preparing highly active Au/ NiOx CO oxidation catalysts. Chem Phys Chem 9 2475-2479... 

The focus of these studies has been on identifying mild activation conditions to prevent nanoparticle agglomeration. Infrared spectroscopy indicated that titania plays an active role in dendrimer adsorption and decomposition in contrast, adsorption of DENs on silica is dominated by metal-support interactions. Relatively mild (150° C) activation conditions were identified and optimized for Pt and Au catalysts. Comparable conditions yield clean nanoparticles that are active CO oxidation catalysts. Supported Pt catalysts are also active in toluene hydrogenation test reactions. 

For successful operation a selective CO oxidation catalyst in a reformer-PEFC system must be operated at ca. 353-373 Kin a complex feed consisting of CO, 02, H2, C02, H20 and N2, and be capable of reducing CO concentrations from about 1% to below 50 ppm - this is equivalent to a CO conversion of at least 99.5% [4, 54, 60], In addition, this conversion must be achieved with the addition of equimolar 02 (twice the stoichiometric amount) and the competitive oxidation of H2 must be minimized. This is expressed as selectivity, which is defined as the percentage of the oxygen fed consumed in the oxidation of CO for commercial operation a selectivity of 50% is acceptable, since at this selectivity minimal H2 is oxidized to water. 

Monitoring pollutants in a variety of composition ranges in motor vehicle and chemical process exhaust gases is a major area of research in pollution abatement technology. Low-temperature CO oxidation catalysts are needed for zero emission vehicles, CO gas sensors, selective oxidation of CO in H2 rich streams in fuel cell applications,1,2 and in closed-cycle C02 lasers used for remote sensing in space applications.3"5 Effective oxidation of CO during... 

Stabilized zeolite-Y is the principal acidic constituent of the catalyst, responsible for most of the cracking activity. The metal catalyst is a supported Pt, added in small amounts, and which functions as a CO oxidation catalyst, allowing cleaner gaseous emissions from the regenerator. 

Figure 5. Reactive oxygen species derived from co-oxidation catalyst of benzy(a)pyrene (B(a)P) diol oxidation, (a) B(a)P (b) (+)B(a)P diol (c) (-)anti-diolepoxide B(a)P enantiomer (d) (-)-B(a)P diol (e) (+)-anti-diolepoxide enantiomer. ROCf = peroxyl radical P-450 monoxygenase. The ( )B(a)P-7,8 diol enantiomer is generated from (B(a)P in vivo from both ROO and...

NASA Conf. Pub. 3076. Eow-Temperature CO-Oxidation Catalysts for Eong-Eife CO2 Easers, D.R. Schryer, G.B. Hoflund, eds., NASA, 1990. 

Chemical vapor deposition (CVD) has been used to prepare nanoparticle catalysts, although the technology is quite expensive. Dimethylgold acetylacetonate absorbs on supports such as MgO. Decomposition at > 100°C produces an efficient CO oxidation catalyst. X-ray absorption near edge (XANES) and extended X-ray absorption fine structure spectroscopies (EXAFS) showed that, under steady-state CO oxidation conditions, the catalyst contained Au(0) in the form of (on average) Aus clusters and also additional gold as... 

In California (US), a 385 MW cogeneration facility comprising four gas turbine combined cycle trains is in operation [137]. Separate fuels such as natural gas, butane, and refinery fuel gas may be used. The refinery gas contains 800 ppm (by volume) sulfur. Sulfur was removed from the fuel before it was burnt in the gas turbine. The gas cleanup system includes a CO oxidation catalyst and downstream from this catalyst a SCR system. 

In Fig. 11, a selected area is shown in (a) for UHV conditions and in (b) for 665 Pa of a CO 02 (1 5) reaction mixture. There are noteworthy parallels between the instability of the small Au clusters, their catalytic activity, and the change in their catalytic activity with time. Au clusters of approximately 3 nm are optimum as CO oxidation catalysts. Clearly, reaction-induced sintering of these small clusters is a mechanism for the loss of activity with time. 

We used this reactor set-up to evaluate highly active room temperature CO-oxidation catalysts based on gold. These systems were discovered by Haruta and co-workers [23], but it is rather difficult to reproduce samples with similar performance based on the publications, as the activity of the final catalysts is determined by many parameters. The bottleneck in synthesizing active catalysts has been testing time, as the full catalytic test takes about a day, if temperatures other than only room temperature are to be investigat-... 

G. Tyuliev, D. Panayotov, I. Avramova, D. Stoichev, T. Marinova, Thin-film coating of Cu-Co oxide catalyst on lanthana/zirconia films electrodeposited on stainless steel, Mater. Sci. Eng. C-Biomim. Supramol. Syst. 23 (2003) 117. 

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