CO Impurities Research Articles

Ordered bilayer ruthenium–platinum core-shell nanoparticles as carbon monoxide-tolerant fuel cell catalysts

Fabricating subnanometre-thick core-shell nanocatalysts is effective for obtaining high surface area of an active metal with tunable properties. The key to fully realize the potential of this approach is a reliable synthesis method to produce atomically ordered core-shell nanoparticles. Here we report new insights on eliminating lattice defects in core-shell syntheses and opportunities opened for achieving superior catalytic performance. Ordered structural transition from ruthenium hcp to platinum fcc stacking sequence at the core-shell interface is achieved via a green synthesis method, and is verified by X-ray diffraction and electron microscopic techniques coupled with density functional theory calculations. The single crystalline Ru cores with well-defined Pt bilayer shells resolve the dilemma in using a dissolution-prone metal, such as ruthenium, for alleviating the deactivating effect of carbon monoxide, opening the door for commercialization of low-temperature fuel cells that can use inexpensive reformates (H2 with CO impurity) as the fuel.

Reaction Mechanisms in Irradiated, Precipitated, and Mesoporous Silica

A matrix EPR spectroscopy study of the low temperature γ radiolysis of precipitated (Zeosil) and mesoporous high surface silica has afforded evidence of the formation of trapped H-atoms, H-atom centers, siloxy radicals ≡Si-O(•), anomalous silyl peroxy radicals ≡Si-OO(•) with reduced g tensor anisotropy, siloxy radical-cations (≡Si-O-Si≡)(+•), E' centers, and two species from Ge impurity. Coordination of peroxyl radicals with diamagnetic ≡Si(+) centers is proposed and tested by DFT computations in order to justify the observed g tensor. Coordination of H-atoms to ≡Si(+) centers is also proposed for the structure of the H-atom centers as an alternative model not requiring the intervention of Ge, Sn, or CO impurities. The DFT method has been employed to assess the electronic structure of siloxy radical-cations and its similarity with that of the carbon radical-cation analogues; the results have prompted a revision of the structures proposed in the literature for ST1 and ST2 centers. The comparison between the two types of silica has afforded evidence of different radiolysis mechanisms leading to a greater yield of trapped H-atoms and H-atom centers in zeosil silica, which is reckoned with the 4-fold greater concentration of silanol groups. Parallel radiolysis experiments carried out by using both types of silica with polybutadiene oligomers as adsorbate have afforded evidence of free valence and energy migration phenomena leading to irreversible linking of polybutadiene chains onto silica. Reaction mechanisms are proposed based on the detection of SiO2-bonded free radicals whose structure has been defined by EPR.

The Long-term Corrosion Behaviour of Abandoned Wells Under CO2 Geological Storage Conditions: (2) Experimental Results for Corrosion of Casing Steel

Regarding the geological storage of CO2 in aquifers or in depleted gas fields, the reactivity of the well casing left in the abandoned well is important in order to investigate the potential for leakage. The corrosion behavior of the casing steel tube was investigated in highly pressurized CO2 environments.The corrosion test of the J55 and N80 steel tube in API specification 5CT was conducted. Those steel tubes have been frequently used as casing tube and are found in abandoned natural gas wells. The following test conditions were achieved with the autoclave apparatus: temperature at 50 to 70°C, CO2 pressure at 5 to 18MPa with/without the impurities of 20ppm H2S and 2000ppm CO, in/above stagnant 0.5M NaCl solution of simulated formation water. The test durations were 100, 300 and 1000hours.After the corrosion test, the specimens were analyzed by Energy dispersive X-ray spectrometry and X-ray diffractometry. The specimens were found to be covered mainly with FeCO3, which is considered to be formed from dissolved Fe2+ and environmental CO2. The corrosion rate was evaluated via the weight loss of the specimens after the removal of the surface corrosion products, containing FeCO3. No significant differences were observed between J55 and N80 in terms of FeCO3 formation and corrosion weight loss. It was found that the weight loss by corrosion, around 100mg/cm2 after 100hours, was remarkably large when the specimen was placed in the solution and was, in contrast, two orders of magnitude smaller when the specimen was above the solution. In the case with the impurities of 20ppm H2S and 2000ppm CO, the weight loss in the solution was less relative to the pure CO2 condition. The weight loss in the solution reached a plateau in initial 100hours, and was only slightly increased in the 300- and the 1000-hour tests. The ‘plateau’ was considered to be due to the protective effect of the FeCO3 formed on the specimen. Considering the protective effect of the FeCO3, the corrosion of the steel casing over a long period of time is small under the stagnant condition, and would be expected to remain in place with little structural degradation.

High performance ZIF-8/PBI nano-composite membranes for high temperature hydrogen separation consisting of carbon monoxide and water vapor

Two types of advanced nano-composite materials have been formed by incorporating as-synthesized wet-state zeolitic imidazolate frameworks-8 (ZIF-8) nano-particles into a polybenzimidazole (PBI) polymer. The loadings of ZIF-8 particles in the two membranes (i.e., 30/70 (w/w) ZIF-8/PBI and 60/40 (w/w) ZIF-8/PBI) are 38.2 vol % and 63.6 vol %, respectively. Due to different ZIF-8 loadings, variations in particle dispersion, membrane morphology and gas separation properties are observed. Gas permeation results suggest that intercalation occurs when the ZIF-8 loading reaches 63.6 vol %. The incorporation of ZIF-8 particles significantly enhances both solubility and diffusion coefficients but the enhancement in diffusion coefficient is much greater. Mixed gas tests for H2/CO2 separation were conducted from 35 to 230 °C, and both membranes exhibit remarkably high H2 permeability and H2/CO2 selectivity. The 30/70 (w/w) ZIF-8/PBI membrane has an H2/CO2 selectivity of 26.3 with an H2 permeability of 470.5 Barrer, while the 60/40 (w/w) ZIF-8/PBI membrane has an H2/CO2 selectivity of 12.3 with an H2 permeability of 2014.8 Barrer. Mixed gas data show that the presence of CO or water vapor impurity in the feed gas stream does not significantly influence the membrane performance at 230 °C. Thus, the newly developed H2-selective membranes may have bright prospects for hydrogen purification and CO2 capture in realistic industrial applications such as syngas processing, integrated gasification combined cycle (IGCC) power plant and hydrogen recovery.

Superconductivity suppression of Ba0.5K0.5Fe2−2xM2xAs2single crystals by substitution of transition metal (M = Mn, Ru, Co, Ni, Cu, and Zn)

We investigated the doping effects of magnetic and nonmagnetic impurities on the single-crystalline p-type Ba0.5K0.5Fe2-2xM2xAs2 (M = Mn, Ru, Co, Ni, Cu and Zn) superconductors. The superconductivity indicates robustly against impurity of Ru, while weakly against the impurities of Mn, Co, Ni, Cu, and Zn. However, the present Tc suppression rate of both magnetic and nonmagnetic impurities remains much lower than what was expected for the s\pm-wave model. The temperature dependence of resistivity data is observed an obvious low-T upturn for the crystals doped with high-level impurity, which is due to the occurrence of localization. Thus, the relatively weak Tc suppression effect from Mn, Co, Ni, Cu, and Zn are considered as a result of localization rather than pair-breaking effect in s\pm-wave model.

The effect of molecular impurities CO and CH4 on the structural characteristics of the C60 fullerene around the orientational phase transition

X-ray studies of structural characteristics of С60(С)0.9 and С60(CH4)0.5 solid solutions were carried out in around the orientation phase transition in the C60 fullerene. It was established that the filling of octahedral cavities of the fullerene lattice by molecules of CO and CH4 results in a significant increase of the lattice parameter and the thermal expansion coefficients of the ordered phase and in a decrease in the volume change and phase transition temperature TC. In this case there also occurs a noticeable “smearing” of the phase transformation. Based on these results and on the data in the literature contradictions in the conclusions about the structural peculiarities of the formation of a glass state in the CO–C60 solutions were analyzed and discussed. Linear dependences of orientational transition temperature TC and glass transition temperature Tg on CO concentration in the octahedral cavities were obtained. Concentrations of CO in the previous study of specific heat of solid mixtures were calculated.

Extraction of extra pure hydrogen from methane steam conversion products in membrane equipment, combined simultaneously with two CO and CH4 conversion catalysts

A numerical modeling method is used to study conditions and parameters for effective preparation of extra pure hydrogen from methane conversion products within a high-temperature converter system, i.e., membrane equipment using two catalysts (CO and CH4 conversion) simultaneously within a high-pressure vessel. Sufficiently complete use is achieved for the starting steam and methane mixture for preparation of high purity hydrogen with the minimum possible content of H2, CO, and CH4 impurities in the discharge gas.

Ab initiostudy of point defects in the strongly correlated system CoO

Density functional theory is applied to study the effect of substitutional Fe, Al, and In impurities on the structural, electronic, and magnetic properties of stoichiometric and nonstoichiometric CoO. Ab initiocalculated hyperfine interactions at the Fe impurity are used to determine aliovalent states of iron dopant in CoO and Co${}_{1\ensuremath{-}x}$O systems as well as to characterize the local structure around the impurity. Various Hubbard potentials describing the on-site Coulomb interactions at the Fe impurity are considered, and their influence on the calculated hyperfine parameters and electronic structure of Fe-doped CoO is analyzed. Different vacancy-impurity configurations within the Co-deficient matrix are taken into account to find the site preferences for Fe, Al, and In dopants. The hyperfine parameters at the Fe impurity in Co${}_{1\ensuremath{-}x}$O are also investigated as a function of the distance between vacancy and impurity. This study shows that divalent Fe cations are created inside the almost perfect host lattice, while the trivalent Fe cations are stabilized in the system containing cobalt vacancies. Trivalent Co ions are induced in the cobalt sublattice defected by vacancies and impurities. The overall concentration of trivalent cations in Co${}_{1\ensuremath{-}x}$O is twice as large as the concentration of cation vacancies. Trivalent cations of different ionic radii prefer residing in the second-neighbor sites of a cationic sublattice with respect to the cobalt vacancy. The energy gap of CoO with Fe${}^{2+}$ ions is comparable to that calculated for the defect-free system. The band gap of Co${}_{1\ensuremath{-}x}$O with Fe${}^{3+}$ and Co${}^{3+}$ ions is reduced due to the acceptor states introduced by both trivalent cations. Band-gap reduction arising from acceptor levels created by Co${}^{3+}$ cations is also observed for Co${}_{1\ensuremath{-}x}$O defected by nonmagnetic trivalent impurities. The present first-principles studies support and supplement results of several M\ossbauer spectroscopy experiments.

The role of SiO2 and sintering temperature on the grain boundary properties of Ce0.8Sm0.2O2−δ

The solid solution Ce0.8Sm0.2O2−δ (20CSO) was synthesized by freeze-drying precursor procedure. Well-crystallized powders with nanometric grain sizes were obtained after calcining the precursor at 375°C for 4h. The effect of SiO2-addition and sintering temperature on the properties of the bulk and grain boundary processes were studied. For this purpose, 20CSO–SiO2 samples were prepared by the addition of 0.05 or 0.5mol% SiO2 to Ce0.8Sm0.2O2−δ, in the form of tetraethyl orthosilicate (TEOS). Also, 2mol% Co was added to some of the precalcined compositions with and without silica-addition. Cobalt free samples were sintered at 1400, 1500 and 1600°C and cobalt-added samples were sintered 1150°C, for 10h to obtain dense pellets. The electrical behaviour of the bulk was revealed to be nearly independent on sintering temperature and/or on the addition of impurities of SiO2 and Co to the grain boundaries. This was explained by the low solubility of impurities in the grain fluorite structure. However, the grain boundary resistance showed important differences as function of sintering temperature and with the presence of impurities. The analysis of grain boundary properties suggests that segregated impurities affect the microstructure and also segregation of Sm at the space charge layer, thus changing both the specific grain boundary conductivity and microstructural parameters.

Assessment of the different parameters affecting the CO 2 purity from coal fired oxyfuel process

The oxyfuel process is one of the most promising options to capture CO 2 from coal fired power plants. The combustion takes place in an atmosphere of almost pure oxygen, delivered from an air separation unit (ASU), and recirculated flue gas. This provides a flue gas containing 80–90 vol% CO 2 on a dry basis. Impurities are caused by the purity of the oxygen from the ASU, the combustion process and air ingress. Via liquefaction a CO 2 stream with purity in the range from 85 to 99.5 vol% can be separated and stored geologically. Impurities like O 2, NO X, SO X, and CO may negatively influence the transport infrastructure or the geological storage site by causing geochemical reactions. Therefore the maximum acceptable concentrations of the impurities in the separated CO 2 stream must be defined regarding the requirements from transportation and storage. The main objective of the research project COORAL therefore is to define the required CO 2 purity for capture and storage.

Effects of impurities on CO2 transport, injection and storage

Abstract Effects of impurities in CO 2 streams on geological storage of CO 2 have been investigated. A number of key issues have been addressed, and several significant findings have been made. Highlighted among the findings are: (1) non-condensable impurites such as N 2 , O 2 and Ar greatly reduce CO 2 storage capacity of geological formations, and there is a maximum reduction of the storage capacity at a certain pressure under a given temperature. By contrast, impurities which are more condensable than CO 2 , such as SO 2 , can increase the storage capacity, and there is a maximum increase at a certain pressure under a given temperature; (2) change of density caused by non-condensable gas impurities results in lower injectivity of impure CO 2 into geological formations. However, above a threshold pressure range the injectivity could reach the level of pure CO 2 due to lowered viscosity; (3) non-condensable impurities increase the buoyancy of the CO 2 plume. This would negatively affect the efficiency of solubility trapping and residual trapping of CO 2 . (4) the effect of SO 2 on reduction of rock porosity and hence CO 2 injectivity would be much smaller than previously thought. A simple formula has been developed to enable quick determination of the effect.

Phase diagrams of CO2 and CO2–N2 gas mixtures and their application in compression processes

Abstract Phase diagrams of carbon dioxide, nitrogen and their mixtures with different amounts of nitrogen (e.g. 5 mol%, 10 mol N 2 ) were calculated with high accuracy with the NIST Reference Fluid Thermodynamic and Transport Properties database program REFPROP ® for up to 200 bar, as well as density-pressure diagrams. Beside the use of carbon dioxide as a solvent for supercritical fluid extraction, increasing interest in physical chemical properties of CO 2 exists as Carbon dioxide Capture and Storage (CCS) starts to play an important role to limit anthropogenic emissions of CO 2 into the atmosphere. Therefore CO 2 processing and pipeline technologies became of considerable commercial importance, especially in the context of future underground storage of CO 2 . As example the CO 2 compression process with gas separation membrane in post-combustion capture was simulated with PRO/II ® software. Through adopting several different equations of states, phase diagrams of different CO 2 –N 2 gas mixtures were calculated and compared with the aforementioned accurate thermodynamic and transport properties calculation results. This type of validation is very useful for process engineering analysis. Further investigations related to the compression process were carried out for the different CO 2 gas mixtures, which are generated from the gas separation membrane capture process. Specific energy of the compression process was analysed for each gas mixture. The energy consumption and the state of the compressed compounds are strongly influenced by the N 2 composition in the mixture. The impurities in multi-component CO 2 mixtures vary strongly depending on the different capture technologies. The calculation of reliable phase diagrams of CO 2 mixtures provides guidelines for optimization of compression, pipeline transport, and storage processes.

Computational evaluation of the capability of transition metal exchanged zeolites for complete purification of hydrogen for fuel cell applications: the cheapest performs the best

The study reports an estimation of the capability of zeolites exchanged with different monovalent transition metal cations to be used for the deep purification of hydrogen for PEMFC applications from CO, ammonia and hydrogen sulfide impurities. The estimation is based on thermodynamic data derived by computational modeling using the periodic DFT approach, and allows determination of the minimal impurity gas concentration in the H2 feed that could be achieved with the specific adsorbent. The results suggest that zeolites exchanged with Co+, Ni+, Cu+, Rh+ or Ir+ cations can purify hydrogen under standard conditions to CO concentrations of 10−12–10−16, depending on the metal. A theoretically recommended material for hydrogen purification is Cu exchanged zeolite, since it is able to reduce CO concentrations down to 10−11 and has weaker binding of CO compared to the other modeled cations, which facilitates the regeneration of the adsorbent. In addition, this zeolite can capture NH3 and H2S impurities and reduce their concentration in the H2 feed to 10−10, while the other modeled cation exchanged zeolites show a higher permeability of these impurities and are less appropriate. Thus, the modeled adsorbents, in particular Cu exchanged zeolite, are good candidates for H2purification due to their low cost and predicted high efficiency, and could be considered as an appropriate alternative to the other currently applied approaches.

A DFT study on the effect of lattice impurities on the electronic structures and floatability of sphalerite

The electronic structures of bulk sphalerite containing 14 typical kinds of impurities were studied by density-functional theory (DFT). The calculated results show that the presence of Cd, Hg, Ga, Ge, In, Ag, Sn, Pb and Sb could increase the lattice parameter of sphalerite. Ag, Sn, Pb, Sb, Cd and Hg impurities narrowed the band-gap and increased the conductivity of sphalerite. Moreover, Mn, Fe, Ga, In, Sn and Sb impurities changed the semiconductor type of sphalerite from p-type to n-type. All of the impurities except Cd and Hg made the Fermi level shift to higher energy and led to the occurrence of an impurity state in the forbidden band. Analysis of the frontier molecular orbital showed that the impurities Mn, Fe, Cu, Ge, Sn, Pb and Sb contributed greatly to the highest occupied molecular orbital (HOMO) and greatly influence the nucleophilicity of sphalerite. On the other hand, the impurities of Fe, Cu, Co, Ni, Cd and Ga greatly contributed to the lowest unoccupied molecular orbital (LUMO) and greatly affected the electrophilicity of sphalerite. The interactions of O 2 and xanthate with sphalerite are discussed. Results suggest that Mn, Fe, Ni, Cu, Sn and Pb impurities favored the oxidization of sphalerite; however, the impurities of Cd, Hg, Ga and In had the opposite effect. Impurities of Mn, Fe, Co, Ni, Cu, Hg and Pb could enhance the reactivity of xanthate with sphalerite.

Chemiluminescence system for direct determination and mapping of ultra-trace metal impurities on a silicon wafer

A highly sensitive chemiluminescence (CL) system which consumed low sample and reagent volumes in the microlitre range was developed for direct determination and mapping of ultra-trace metal contaminants on solid surfaces, such as silicon wafers or flat display panels. The analytical result of the system was confirmed with ICP-MS. The system was composed of a scanner, sensor and a wafer moving stage. The scanner, with a scanning tip made of 0.03'' i.d. PTFE tubing, was used to collect metal impurities on the wafer surface with 5 μL of scanning solution. A coaxial sensing head of about 13 mm o.d. and 110 mm height was designed both to inject a luminescent reagent of luminol-H(2)O(2) mixture and to collect the luminescence light resulting from the reaction with metal ions of Co(2+), Fe(2+), Cu(2+), and Ni(2+). Due to the almost zero background, an extremely low limit of detection of 20.8 pg/mL for Co(2+) in 1% hydrofluoric acid (HF) was obtained from the calibration curve. In order to map the spatial distribution of the impurities, 11 cross sections of a Co-contaminated wafer were selected and scanned individually with a diluted HF solution. A contaminant level of 1.45-7.11 × 10(11) atoms cm(-2) was obtained for each section with an average of 4.21 × 10(11) atoms cm(-2), which was similar to the analytical result of 5.48 × 10(11) atoms cm(-2) obtained from vapor phase deposition-inductively coupled plasma-mass spectrometry (VPD-ICP-MS). Although this CL system does not have selectivity for each specific metal ion, its high sensitivity facilitates the monitoring and mapping of metal impurities of Co, Fe, Cu, etc. on the wafer directly and it can be used as an on-line inspection sensor for the first time in the semiconductor industry.

Performance of the direct formic acid fuel cell with electrochemically modified palladium–antimony anode catalyst

Previous work has shown that palladium catalysts are quite active for formic acid electrooxidation, but the catalysts need to be periodically regenerated to remove a CO impurity from the surface. The objective of this paper is to determine whether antimony additions could suppress the CO formation under fuel cell conditions. We find that antimony doubles the rate of reaction in an electrochemical cell, but the increase is less in real fuel cell conditions. The current that is produced at 0.6 V is approximately 14% greater for the fuel cell containing antimony additions than the palladium anode catalyst. In a constant-current test, we find that the fuel cell assembled with palladium–antimony anode catalyst produces 18% more voltage than the palladium anode catalyst after 9 h of operation. These results show that the antimony additions that significantly improve oxidation in the electrochemical cell have a much lesser impact in the formic acid fuel cell – they do not suppress CO formation in the fuel cell as anticipated.

Ab initio study of the magnetic interaction of Co and Ni doped ZnO with intrinsic vacancies

Abstract Within the framework of density functional theory we have computed the total energy and the magnetic properties of wurtzite ZnO doped with diluted impurities of Co or of Ni in the presence of intrinsic vacancies. The complex M Zn –V Zn (M=Co,Ni) , where the Zn-vacancy ( V Zn ) is in the next nearest neighbour site with respect the transition metal M atom, is energetically favored with respect to the configuration in which the two defects are far apart. Also for the more favourite thermodynamic growth condition the probability to find these types of complex at room temperature is relatively small (of the order of 10 −7 or less).

The Effects of Changing Fuels on Hot Gas Path Conditions in Syngas Turbines

Gas turbines in integrated gasification combined cycle power plants burn a fuel gas (syngas (SG)) in which the proportions of hydrocarbons, H2, CO, water vapor, and minor impurity levels may differ significantly from those in natural gas (NG). Such differences can yield changes in the temperature, pressure, and corrosive species that are experienced by critical components in the hot gas path, with important implications for the design, operation, and reliability of the turbine. A new data structure and computational methodology is presented for the numerical simulation of a turbine thermodynamic cycle, with emphasis on the hot gas path components. The approach used allows efficient handling of turbine components and variable constraints due to fuel changes. Examples are presented for a turbine with four stages, in which the vanes and blades are cooled in an open circuit using air from the appropriate compressor stages. For an imposed maximum metal temperature, values were calculated for the fuel, air, and coolant flow rates and through-wall temperature gradients for cases where the turbine was fired with NG or SG. A NG case conducted to assess the effect of coolant pressure matching between the compressor extraction points and corresponding turbine injection points indicated that this is a feature that must be considered for high combustion temperatures. The first series of SG simulations was conducted using the same inlet mass flow and pressure ratios as those for the NG case. The results showed that higher coolant flow rates and a larger number of cooled turbine rows were needed for the SG case to comply with the imposed temperature constraints. Thus, for that case, the turbine size would be different for SG than for NG. A second series of simulations examined scenarios for maintaining the original turbine configuration (i.e., geometry, diameters, blade heights, angles, and cooling circuit characteristics) used for the SG simulations. In these, the inlet mass flow was varied while keeping constant the pressure ratios and the amount of hot gas passing the first vane of the turbine. The effects of turbine matching between the NG and SG cases were increases—for the SG case of approximately 7% and 13% for total cooling flows and cooling flows for the first-stage vane, respectively. In particular, for the SG case, the vanes in the last stage of the turbine experienced inner wall temperatures that approached the maximum allowable limit.

Preferential Oxidation of CO Impurities in the Presence of H2 on NiO-Loaded and Unloaded TiO2 Photocatalysts at 293 K

The photocatalytic preferential oxidation of CO with O2 in the presence of H2 (photo-PROX) was found to proceed efficiently on the NiO-loaded TiO2 (NiO/TiO2) catalyst under UV light irradiation at 293 K. NiO/TiO2 exhibited higher CO conversion as well as CO2 selectivity for a photo-PROX reaction than the original unloaded TiO2 (P-25). Various spectroscopic investigations have revealed that the small NiO clusters formed on TiO2 play an important role in the enhancement of CO oxidation activity in this reaction.

Nanodispersed Au/Al 2O 3 catalysts for low-temperature CO oxidation: Results of research activity at the Boreskov Institute of Catalysis

This paper presents some important results of the studies on preparation and catalytic properties of nanodispersed Au/Al 2O 3 catalysts for low-temperature CO oxidation, which are carried out at the Boreskov Institute of Catalysis (BIC) starting from 2001. The catalysts with a gold loading of 1–2 wt.% were prepared via deposition of Au complexes onto different aluminas by means of various techniques (“deposition-precipitation” (DP), incipient wetness, “chemical liquid-phase grafting” (CLPG), chemical vapor deposition (CVD)). These catalysts have been characterized comparatively by a number of physical methods (XRD, TEM, diffuse reflectance UV/vis and XPS) and catalytically tested for combustion of CO impurity (1%) in wet air stream at near-ambient temperature. Using the hydroxide or chloride gold complexes capable of chemical interaction with the surface groups of alumina as the catalyst precursors (DP and incipient wetness techniques, respectively) produces the catalysts that contain metallic Au particles mainly of 2–4 nm in diameter, uniformly distributed between the external and internal surfaces of the support granules together with the surface “ionic” Au oxide species. Application of organogold precursors gives the supported Au catalysts of egg shell type which are either close by mean Au particle size to what we obtain by DP and incipient wetness techniques (CVD of (CH 3) 2Au(acac) vapor on highly dehydrated Al 2O 3 in a rotating reactor under static conditions) or contain Au crystallites of no less than 7 nm in size (CLPG method). Regardless of deposition technique, only the Cl-free Au/Al 2O 3 catalysts containing the small Au particles ( d i ≤ 5 nm) reveal the high catalytic activity toward CO oxidation under near-ambient conditions, the catalyst stability being provided by adding the water vapor into the reaction feed. The results of testing of the nanodispersed Au/Al 2O 3 catalysts under conditions which simulate in part removal of CO from ambient air or diesel exhaust are discussed in comparison with the data obtained for the commercial Pd and Pt catalysts under the same conditions.