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Applied Catalysis A, General (v.347, #1)

Editorial Board (pp. co2).

Contents (pp. iii-vi).

Pd-γAl₂O₃ applied to triglycerides hydrogenation with supercritical propane by C.M. Piqueras; I.O. Costilla; P.G. Belelli; N.J. Castellani; D.E. Damiani (pp. 1-10).

Pd-γAl₂O₃ catalysts with different metallic particle size and modified with Cl were used in the triglyceride hydrogenation. The experiences were carried out in homogeneous-phase conditions using supercritical propane. FTIR spectra's and DFT calculations evidenced the enhancement of the CO adsorption energy due to the presence of electro deficient ensembles. These lasts could promote the modification of the reaction selectivity and (TOF) values.▪A set of Pd-γAl₂O₃ catalysts of different metallic particle sizes and modified with 2-chloro-butane was used for triglyceride hydrogenation. The experiments were carried out in single-phase conditions using propane as a supercritical solvent. A generalized criterion was used to determine the absence of mass-transfer limitations for both reactants inside the pore structure of the catalyst.FTIR spectra of CO on diverse catalysts showed different absorption bands and significant shifts to higher wavelengths of the CO species corresponding to on-top and bridge configurations. In order to test these results, theoretical studies using the density functional theory (DFT) were carried out for the FTIR of CO adsorption on two Pd ensembles, with or without charge deficiency and with Cl adsorbed on them. The results showed similar displacements of the band frequencies to those obtained experimentally, and demonstrate an enhancement of the CO adsorption energy of the on-top, isolated bridge and three-fold bridge CO species on electron deficient ensembles. Enhancement of the adsorption bond strength could promote the direct hydrogenation of the diunsaturated compound to complete saturated fatty acid chains. The decrease of the specific reaction rate (TOF) and the increase of the saturated fatty acids production, as well as a decrease of the monounsaturated and isomers content observed is in line with a possible modification of the electronic properties of the Pd particles. The influence of some planes of Pd clusters intervening on the direct hydrogenation is discussed.

Keywords: Palladium; FTIR; Supercritical propane; Triglyceride; Hydrogenation

The oxidative dehydrogenation of n-octane to styrene using catalysts derived from hydrotalcite-like precursors by Holger B. Friedrich; Abdul S. Mahomed (pp. 11-22).

Catalysts with varying Mg/V ratio, derived from hydrotalcite-like precursors, were investigated in aerobic oxidation of n-octane under varying conditions of GHSV, temperature and feed/air ratio. Styrene was found to be the dominant organic product with a maximum selectivity of 19% obtained over a catalyst with a Mg/V ratio of 2.3.▪A number of hydrotalcite-like compounds containing Mg and V were prepared with different Mg/V ratios, ranging from 1:1 to 4:1. The effect of variations in synthesis procedures, such as preparing the compounds under inert gas, hydrothermal treatments at different temperatures and different precipitating agents were examined. These compounds were characterised by ICP-OES, powder XRD (including, in part, in situ powder XRD under H₂, air and N₂), Raman (incl. in situ), IR, XPS and SEM. They were then investigated as catalysts for the aerobic oxidation of n-octane under varying conditions of GHSV, temperature and feed/air ratio. Styrene was found to be the dominant organic product and a maximum selectivity of 19%, corresponding to a yield of 14%, was obtained with a catalyst with a Mg/V ratio of 2.3. The mechanism appears to involve olefin formation, followed by cyclisation to form ethyl benzene, which is further dehydrogenated to form styrene. Catalysts where the precursors have more amorphous structures were found to be superior to those obtained from highly crystalline precursors, and catalysts derived from sodium salts were superior to those obtained from potassium salts.

Keywords: Alkane (paraffin) oxidation; n; -Octane; Styrene; Hydrotalcite; In situ; characterisation

Calcination temperature and CuO loading dependence on CuO-CeO₂ catalyst activity for water-gas shift reaction by Petar Djinović; Jurka Batista; Albin Pintar (pp. 23-33).

In this work we investigated an influence of CuO loading and catalyst pretreatment procedure to derive at an optimal CuO-CeO₂ catalyst for water-gas shift (WGS) reaction, and to study in detail the structure–activity relationships. The results of activity measurements and catalyst characterization by means of temperature-programmed techniques demonstrate that WGS activity of CuO-CeO₂ catalysts synthesized by means of co-precipitation is influenced by CuO dispersion, extent of surface CeO₂ reduction and surface acidic properties.▪In this work we investigated the influence of CuO loading and catalyst pretreatment procedure to derive an optimal CuO-CeO₂ catalyst for water-gas shift (WGS) reaction, and to study in detail structure–activity relationships. Nanostructured catalyst samples prepared by co-precipitation and a 10, 15 and 20mol% CuO content were examined by XRD, BET and TPR/TPD analyses and subjected to pulse WGS activity tests in the temperature range of 180–400°C. As evaluated by TPR/TPD and N₂O chemisorption analyses, with increasing CuO loading the portion of finely dispersed CuO nanoparticles decreases on behalf of larger CuO aggregates. Strong surface structure–activity dependence in WGS reaction was observed for all catalyst samples. It was established that increasing CuO content results in higher extent of CeO₂ reduction, which has a positive effect on H₂ production during the WGS reaction. Increasing calcination temperature on the other hand reduces BET surface area, induced by CuO sintering and agglomeration of CeO₂ particles resulting in a negative effect on H₂ production. Distinctive WGS activity dependence on surface acidity of examined solids was observed for all CuO loadings.

Keywords: Cu-Ce mixed oxide catalysts; CuO loading; Calcination temperature; Water-gas shift reaction

Novel methanol steam reforming activity and selectivity of pure In₂O₃ by Harald Lorenz; Wilfrid Jochum; Bernhard Klötzer; Michael Stöger-Pollach; Sabine Schwarz; Kristian Pfaller; Simon Penner (pp. 34-42).

Pure In₂O₃ thin film and In₂O₃ powder catalysts were found to be structurally stable and highly active and CO₂-selective in methanol steam reforming between 450 and 673K. No catalytic activity in both routes of the water–gas shift reaction as tested in the same temperature region where the catalysts exhibit high reforming activity and selectivity, could be observed.▪Electron-microscopy suitable In₂O₃ thin films prepared by thermal deposition of In₂O₃ powder in 10⁻²Pa O₂ at 600K and, for comparison, a commercial polycrystalline In₂O₃ powder catalyst were tested in methanol steam reforming and in both routes of the water–gas shift reaction as a function of reaction temperature. The effect of oxidative (1bar O₂, 373–673K, 1h) and reductive (1bar H₂, 373–673K, 1h) catalyst pre-treatments was assessed. The resulting structural and morphological changes occurring during catalyst activation and catalytic reaction were monitored by (high-resolution) transmission electron microscopy, scanning electron microscopy and surface area measurements by N₂ adsorption according to BET.Both the In₂O₃ thin film and the powder sample were observed to be structurally stable under typical catalyst pre-treatments in oxygen and hydrogen at temperatures T≤673K and T<673K, respectively, as well as under typical methanol steam reforming conditions at temperatures T≤680K. No pronounced catalyst sintering was observed below 673K.Both In₂O₃ samples were found to be highly active and selective toward CO₂ in methanol steam reforming over a broad temperature range (450< T<673K). Selectivities of >95% toward CO₂ were usually observed, with at maximum 5% or less CO formed. No dependence of selectivity on either reaction temperature or oxidative/reductive pre-treatment was observed.No catalytic activity in both routes of the water–gas shift reaction as tested in the same temperature region where the catalysts exhibit high reforming activity and selectivity, could be observed. Therefore In₂O₃ based catalysts offer a broad range of temperature not influenced by unwanted CO formation via the inverse water–gas shift process.

Keywords: (High-resolution) electron microscopy; Indium oxide; Thin film model catalyst; Powder catalyst

Fe-N-C oxygen reduction catalysts supported on vertically aligned carbon nanotubes by Gary Chih-Kang Liu; J.R. Dahn (pp. 43-49).

Fe-N-C oxygen reduction reaction catalyst was sputter deposited vertically aligned carbon nanotubes (VACNTs) and activated by annealing to 800°C. The catalyst activity was evaluated electrochemically and shown to be equivalent to the best Fe-N-C catalysts in the literature. ▪Non-noble metal electrocatalyst (Fe-N-C) for the oxygen reduction reaction (ORR) was sputter deposited onto films of vertically aligned carbon nanotubes (VACNT) and tested by the rotating ring disk electrode (RRDE) technique. The VACNT support was first synthesized at atmospheric pressure on a SiO₂/Si wafer substrate in a simple tube furnace by iron-catalyzed chemical vapor deposition of ethylene and ammonia at a temperature of 720°C. VACNT films, with CNT bundle height of 1.5μm and CNT diameter of 50nm, were loaded into a sputtering machine to deposit Fe-N-C materials onto the VACNT as support. Iron and carbon were sputtered in a nitrogen atmosphere in order to deposit an amorphous mixture of Fe-N-C material on the VACNT films. The Fe-N-C material supported on the VACNT films was then annealed in Ar at 800°C to make the ORR electrocatalyst. The catalyst-coated VACNT was scraped off the SiO₂/Si substrate and made into catalyst ink for testing by the RRDE technique. The impact of catalyst loading on the RRDE performance (disk current density and %H₂O₂) is discussed.

Keywords: Abbreviations; CNT; carbon nanotube; CVD; chemical vapor deposition; cm; centimeter; DC; direct current; ORR; oxygen reduction reaction; RRDE; rotating ring disk electrode; RTP; rapid thermal processor; RHE; reversible hydrogen electrode; SEM; scanning electron microscope; sccm; standard cubic centimeter per minute; TEM; transmission electron microscope; VACNT; vertically aligned carbon nanotubeProton exchange membrane fuel cell (PEMFC); Oxygen reduction reaction (ORR); Electrocatalyst; Catalyst support; Vertically aligned carbon nanotubes (VACNT); Rotating ring disk electrode (RRDE) technique

Role of adsorption activation energy in heat change of irreversible dissociative adsorption with coverage on energetically heterogeneous solid surface by Yun Hang Hu (pp. 50-54).

The change of differential adsorption heat with coverage on double-site surface is strongly dependent on the difference of adsorption activation energies between active sites. Furthermore, a discontinuous double-site surface can exhibit continuous changes of differential adsorption heat with coverage. This indicates that the distribution functions obtained from the relationship between differential adsorption heat and coverage may provide an incorrect characteristic of surface energetic heterogeneity.▪The differential heat of gas adsorption on solid surface is often used to determine surface energy heterogeneity. In this paper, the theoretical analysis of irreversible dissociative adsorption on double-site surfaces shows that the change of differential adsorption heat with coverage is strongly dependent on the difference of adsorption activation energies between active sites. Furthermore, it was found that a discontinuous double-site surface can exhibit continuous changes of differential adsorption heat with coverage. This indicates that the distribution functions obtained from the relationship between differential adsorption heat and coverage may provide an incorrect characteristic of surface energetic heterogeneity.

Keywords: Irreversible dissociative adsorption; Heterogeneous solid surface; Coverage; Adsorption activation energy

Catalytic activity and magnetic properties of Co–ZSM-5 zeolites prepared by different methods by Liliana B. Pierella; Clara Saux; Silvana C. Caglieri; Héctor R. Bertorello; Paula G. Bercoff (pp. 55-61).

The catalytic oxidation of styrene with H₂O₂ was studied over Co–ZSM-5 zeolites which differ in the preparation methods. Styrene conversion shows an important increment when Lewis acid sites concentration was enhanced (observed by FTIR). The magnetic properties of the zeolites were improved with cobalt incorporation and the applied thermal treatments. The catalytic and magnetic properties of Co–ZSM-5 samples are discussed.▪The selective catalytic oxidation of styrene with hydrogen peroxide was studied over Co–ZSM-5 catalysts which differ in the preparation methods. The catalysts were obtained from NH₄⁺–ZSM-5 by wetness impregnation and ion-exchange techniques followed by different post-thermal treatments: oxidation and reduction. The characterization of acidic properties by FTIR of adsorbed pyridine revealed that new and strong Lewis sites (1452cm⁻¹), different from those characteristics of aluminum in the matrix (1456cm⁻¹) were generated by cobalt introduction. Styrene conversion shows an important increment over the exchanged samples as compared to the impregnated ones. This behavior may be explained by the high Lewis acid sites concentration. Benzaldehyde was the main product in all the samples under study. The samples’ magnetic properties were improved with the cobalt incorporation and the applied thermal treatments. The catalytic and magnetic properties of Co–ZSM-5 samples are discussed.

Keywords: Co–ZSM-5; Lewis and Brönsted acidity; Styrene oxidation; Magnetic properties

Selective CO oxidation with nano gold particles-based catalysts over Al₂O₃ and ZrO₂ by Nielson F.P. Ribeiro; Fabiana M.T. Mendes; Carlos A.C. Perez; Mariana M.V.M. Souza; Martin Schmal (pp. 62-71).

Gold catalysts nano-dispersed on oxide supports Al₂O₃, ZrO₂ and 10% ZrO₂/Al₂O₃ were evaluated in selective CO oxidation. In situ XRD experiments were performed to identify the active phase and the average size during reaction. No significant changes were observed in the average size after 60h on stream, and that the active phase depends strongly on the support.▪We present the preparation, characterization and catalytic evaluation of gold-based catalysts over Al₂O₃, ZrO₂ and 10% ZrO₂/Al₂O₃ in selective CO oxidation. Oxidation and reduction pretreatments were evaluated using in situ X-ray diffraction, and the size of gold particles was determined. All catalysts contained gold particles in the range of 2–5nm, with as-prepared samples containing a mixture of gold species (Au³⁺ and Au⁰). The catalytic tests showed complete CO oxidation at temperatures lower than 100°C, with Au/ZrO₂ sample presenting the best performance. Both the support and pretreatment conditions were found to cause changes to gold species. In situ X-ray diffraction patterns indicated the presence of different gold phases and of nanometer-scale crystallites of gold, which was confirmed by transmission electron microscopy results. It was also found that cationic gold improved the activity of Au/ZrO₂. Concerning stability, time on stream tests showed that all samples were stable to coke deposition and sintering.

Keywords: Gold; Nanoparticles; CO oxidation; In situ XRD

Iron-catalyzed gas-phase epoxidation of propylene by N₂O via halide-assisted oxygen transfer by Blažej Horváth; Milan Hronec (pp. 72-80).

The epoxidation of propylene using N₂O over Fe-containing catalysts was studied. Silicate catalysts showed 69% selectivity to epoxide at 1.6% conversion. Supported, halide-modified catalysts exhibit two epoxidation routes: one, similar to that of silicates; and a second, more selective, air-induced, with a 45.7% conversion. A mechanism involving KCl as an oxygen transmitter is suggested.▪The gas-phase epoxidation of propylene using nitrous oxide as an oxidant over bulk and supported iron-containing catalysts was studied. The presence of silica and an alkaline metal in both types of catalysts was found to be indispensable. Bulk catalysts formed in potassium–iron mixed silicates were studied, with respect to their crystalline structure, oxidation state and performance in propylene epoxidation. Over these catalysts a 69% selectivity to propylene oxide at 1.6% propylene conversion was reached. The presence of separated iron oxide phase was shown to promote the undesired allylic oxidation of propylene. Supported, halide-modified Fe-containing catalysts exhibit a superposition of two epoxidation routes. One, independent of air-pretreatment, shows similarity with that observed at bulky potassium–iron silicates; and the second, more selective, induced by air-pretreatment. The second mechanism, dominant in the first 30min on stream, results in a maximum of 45.7% propylene conversion at 70% selectivity to propylene oxide. An improvement of the epoxidation activity was obtained, comprising reaction–reactivation switching steps. A reaction mechanism involving KCl as an oxygen transmitter and a metastable form of iron moieties is suggested.

Keywords: Epoxidation; Propylene oxide; Nitrous oxide; Iron catalyst; Chlorohydrine

Total oxidation of propene at low temperature over Co₃O₄–CeO₂ mixed oxides: Role of surface oxygen vacancies and bulk oxygen mobility in the catalytic activity by L.F. Liotta; M. Ousmane; G. Di Carlo; G. Pantaleo; G. Deganello; G. Marcì; L. Retailleau; A. Giroir-Fendler (pp. 81-88).

The present paper studies the propene oxidation over Co₃O₄–CeO₂ mixed oxides. Complete oxidation of C₃H₆ to CO₂ and H₂O is achieved below 350°C, the most active samples, Co₃O₄ and the mixed oxide Co₃O₄ (30wt%)–CeO₂ (70wt%) giving full conversion of the hydrocarbon at 250°C. As an important property, the catalysts maintain stable activity upon three consecutive heating–cooling cycles and unchanged textural and reduction properties.▪Co₃O₄, CeO₂ and Co₃O₄–CeO₂ mixed oxides with Co/Ce nominal atomic ratio 0.1:5, prepared by co-precipitation method with sodium carbonate, were tested in the oxidation of propene under lean condition and the catalyst stability was checked by performing three consecutive heating–cooling cycles. Characterization of the textural properties were performed by surface area measurement BET, X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. Among the Co₃O₄–CeO₂ mixed oxides, Co₃O₄ (30wt%)–CeO₂ (70wt%) gives the best activity attaining full propene conversion at 250°C. This sample is characterized by the presence of Co₃O₄ particles well dispersed and in good contact with ceria according to BET and XRD data and as evidenced by SEM micrographs.Oxygen temperature-programmed desorption (O₂-TPD) and C₃H₆-temperature-programmed reduction (C₃H₆-TPR) experiments were carried out in order to study the surface and bulk oxygen mobility and to correlate it to the activity. At temperature around 200°C, O₂-TPD experiments showed the desorption of mobile surface oxygen species for the most active samples, Co₃O₄ and Co₃O₄ (30wt%)–CeO₂ (70wt%). C₃H₆-TPR experiments for both of the oxides also evidenced a high reactivity at low temperature, especially, for Co₃O₄ (30wt%)–CeO₂ (70wt%) giving at 345°C an intense peak of CO₂ formation.Conversely, the ceria sample showed by C₃H₆-TPR much less pronounced oxygen bulk mobility, starting to react with propene above 500°C and forming only CO.In this case, the catalytic activity of ceria was explained in terms of formation of surface oxygen vacancies which are relevant to the propene oxidation in presence of gaseous oxygen.

Keywords: Propene total oxidation; C; ₃; H; ₆; -TPR; TPD experiments; Surface oxygen vacancies; SEM characterization

Modified goethites as catalyst for oxidation of quinoline: Evidence of heterogeneous Fenton process by Iara R. Guimarães; Luiz C.A. Oliveira; Paulo F. Queiroz; Teodorico C. Ramalho; Marcio Pereira; José D. Fabris; José D. Ardisson (pp. 89-93).

In the present work, the reactivity of a heterogeneous Fenton system based on thermally treated goethite, particularly focusing on the effect of surface Fe²⁺ sites on the iron oxide particles to degrade quinoline in aqueous medium was studied. The reactions were monitored by using an electrospray ion source with an Agilent ion trap mass spectrometer (ESI-MS). The chemical mechanism was modeled with theoretical calculations. ▪A heterogeneous Fenton-like reaction occurring on the thermally modified surface of a synthetic iron oxide previously treated with a H₂ stream was investigated. The quinoline decomposition, used as an organic substrate model, was monitored with electrospray ionization mass spectrometry. Quinoline was found to be oxidized through a successive hydroxylation mechanism. These results strongly suggest that highly reactive hydroxyl radicals, generated during the reaction involving H₂O₂ on the catalysts surface, respond for this oxidation, and confirm that the material is an efficient heterogeneous Fenton-like catalyst. Theoretical quantum mechanics calculations, by the density functional theory (DFT), were carried out in order to understand the basic molecular degradation steps for quinoline decomposition mechanism on this H₂-treated goethite (αFeOOH) surface.

Keywords: Goethite; Fenton-like process; Mössbauer spectroscopy

Performance of nano-sized Au/TiO₂ for selective catalytic reduction of NO_x by propene by Long Q. Nguyen; Chris Salim; Hirofumi Hinode (pp. 94-99).

Nano-sized gold particles on titania catalysts were prepared by metal sol method. The catalytic activity for selective catalytic reduction of NO_x by C₃H₆ was evaluated in the excess oxygen condition. At very low Au loading of 0.1%, good catalytic performance and a relatively wide operation window were achieved, although the peak temperature shifted to slightly higher temperature. ▪Nano-sized gold particles supported on titania catalysts (Au/TiO₂) were prepared by metal sol method. The catalytic activity of the nano-sized Au/TiO₂ catalysts for selective catalytic reduction (SCR) of NO_x by propene in the presence of excess oxygen was investigated. The maximum NO_x conversion to N₂ over Au (1wt.%)/TiO₂ was obtained at 325°C which is relatively lower than was the case for Au/Al₂O₃. Anatase crystalline type is preferable for Au/TiO₂ catalyst because of the higher NO_x reduction and C₃H₆ oxidation performance at low temperatures compared with the rutile form. When the Au loading was lowered to 0.1wt.%, the peak temperature shifted to 375°C but the maximum NO_x conversion remained the same as that of 1wt.% Au loading sample. The full width at half maximum of conversion (FWHM) increased significantly as the loading of Au decreased. FWHM of 0.1wt.% Au loading was almost two times wider than that of the 1wt.% Au loading sample. The effect of feed composition, including moisture, was also investigated.

Keywords: Nano-sized gold; Au/TiO; ₂; SCR; Metal sol method

Transesterification reaction of vegetable oils, using superacid sulfated TiO₂–base catalysts by Rusiene M. de Almeida; Lúcia K. Noda; Norberto S. Gonçalves; Simoni M.P. Meneghetti; Mario R. Meneghetti (pp. 100-105).

Superacid sulfated titania (TiO₂/SO₄) catalysts (TS series) have been prepared via the sol–gel technique, with different sulfate concentrations, and tested in the methanolysis reaction of soybean and castor oils at 120°C, for 60min. These catalysts have been characterized by several techniques in order to determine their physico-chemical characteristics and the influence of their properties in their catalytic activity. The catalyst that exhibits the highest catalytic activity (TS-5) was that which displayed the highest specific surface area, average pores diameter and pore volume, and highest percentage in sulfate groups.▪Superacid sulfated titania catalyst, TiO₂/SO₄ (TS-series), have been prepared via the sol–gel technique, with different sulfate concentrations. The relation of structure and catalytic activity of the prepared material have been evaluated. The obtained material was characterized by several techniques, as infrared and Raman absorption spectroscopy, pyridine-adsorption infrared spectroscopy, thermogravimetric analyses and obtention of N₂ adsorption–desorption isotherms. The catalyst that exhibits the highest catalytic activity in the methanolysis of soybean and castor oils at 120°C, for 60min (40% and 25%, respectively) was that which displayed the highest specific surface area, average pores diameter and pore volume, and highest percentage in sulfate groups (TS-5).

Keywords: Superacids; Biodiesel; Transesterification; TiO; ₂; /SO; ₄

Effect of hydrogen on carbon formation on Ni/YSZ composites exposed to methane by Kasra Nikooyeh; Ryan Clemmer; Vanesa Alzate-Restrepo; Josephine M. Hill (pp. 106-111).

Nickel/yttria-stabilized zirconia (Ni/YSZ) is the conventional anode material for solid oxide fuel cells (SOFC). Although these anodes have many advantages, they suffer from carbon formation when exposed to hydrocarbon feeds. One potential way to decrease the severity and extent of carbon formation is to increase the hydrogen content of the feed. In this work, Ni/YSZ composites have been prepared and exposed at 1073K to humidified feeds containing hydrogen to methane ratios varying between 0 and 1.5. The Ni/YSZ composites were analyzed using temperature-programmed oxidation (TPO), temperature-programmed hydrogenation (TPH), and scanning electron microscopy (SEM). Our results demonstrated that TPH techniques can be effectively used to characterize and fully remove the carbon formed on Ni/YSZ composites provided that the hydrogen content of the analysis stream is sufficient. Hydrogen addition to methane in the inlet feed significantly decreased the degree of carbon formation, and removal of the carbon using hydrogen rather than oxygen resulted in less damage to the microstructure.The carbon deposits formed on Ni/YSZ exposed at 1073K to humidified feeds containing H₂:CH₄ ratios between 0 and 1.5 were examined using temperature-programmed oxidation, temperature-programmed hydrogenation, and scanning electron microscopy. The carbon can be fully removed using hydrogen provided that the hydrogen concentration is sufficient. Reaction and regeneration with hydrogen results in the least damage to the Ni/YSZ microstructure. ▪

Keywords: Ni/YSZ; Carbon deposition; Temperature-programmed oxidation; Temperature-programmed hydrogenation; SOFC; Hydrogen

CO oxidation on rough Au thin films grown on Si wafer by H.O. Seo; S.H. Jeong; H.J. Lee; H.-G. Jee; J.-H. Boo; D.C. Lim; Y.D. Kim (pp. 112-116).

The CO oxidation reactivity of nanoporous Au thin films with W impurity (∼5% of Au) was studied. No CO oxidation is observed at room temperature. At 160°C, the conversion of CO to CO₂ was observed. Decomposition of the carbonate species on the surface is the rate-determining step of the CO oxidation reaction. ▪The CO oxidation reactivity of rough Au thin films containing ∼5% W was investigated. At room temperature, no CO oxidation could be detected under our experimental conditions, whereas conversion of CO to CO₂ was observed at 160°C. At higher temperatures, the initial reactivity increased. However, with increasing reaction time, it was evident that deactivation of the catalytically active sites was more facile at higher temperatures. Temperature-programmed desorption (TPD) suggested that the formation of strongly bound carbonate species could be responsible for the deactivation process. Based on the TPD data, we propose that decomposition of carbonate species on the surface is the rate-determining step of CO oxidation.

Keywords: Au; CO oxidation; Nanostructure

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Applied Catalysis A, General (v.347, #1)