Influence of catalyst pretreatments on volatile organic compounds oxidation over gold/iron oxide

Minicò, Simona; Scirè, Salvatore; Crisafulli, C.; Galvagno, S.

doi:10.1016/s0926-3373(01)00221-1

Cited by 163 publications

(84 citation statements)

References 35 publications

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“…7). Hence, the peaks at 84.9 and 88.6 eV were assigned to ionic gold species Au δ+ in line with the reported data (Au 3+ [32] and Au 1+ [33]). Thus, a study of the sample before the reduction in H 2 finds gold species with different oxidation states.…”

Section: Au/acf Catalysts Formationsupporting

confidence: 90%

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Highly dispersed gold on activated carbon fibers for low-temperature CO oxidation

Bulushev

Yuranov

Suvorova

et al. 2004

Journal of Catalysis

202

132

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Gold nanoparticles of 2-5 nm supported on woven fabrics of activated carbon fibers (ACF) were effective during CO oxidation at room temperature. To obtain a high metal dispersion, Au was deposited on ACF from aqueous solution of ethylenediamine complex [Au(en) 2 ]Cl 3 via ion exchange with protons of surface functional groups. The temperature-programmed decomposition method showed the presence of two main types of functional groups on the ACF surface: the first type was associated with carboxylic groups easily decomposing to CO 2 and the second one corresponded to more stable phenolic groups decomposing to CO. The concentration and the nature of surface functional groups was controlled using HNO 3 pretreatment followed by either calcination in He (300-1273 K) or by iron oxide deposition. The phenolic groups are able to attach Au 3+ ions, leading to the formation of small Au nanoparticles (< 5 nm) after reduction by H 2 . This was confirmed by high-resolution electron microscopy combined with X-ray energy-dispersive analysis. The catalyst with high Au dispersion demonstrated high activity in CO oxidation. The surface carboxylic groups decomposed during interaction with [Au(en) 2 ]Cl 3 solution and reduced Au 3+ to Au 0 , resulting in the formation of bigger (> 9 nm) Au agglomerates after reduction by H 2 . These catalysts demonstrated lower activity as compared to the ones containing mostly small Au nanoparticles. Complete removal of surface functional groups rendered an inert support that would not interact with the Au precursor. The oxidation state of gold in the Au/ACF catalysts was controlled by X-ray photoelectron spectroscopy before and after the reduction in H 2 . The high-temperature reduction in H 2 (673-773 K) was necessary to activate the catalyst, indicating that metallic gold nanoparticles are active during catalytic CO oxidation.  2004 Elsevier Inc. All rights reserved.

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Section: Au/acf Catalysts Formationsupporting

confidence: 90%

“…The spectrum was complex; therefore, it was deconvoluted into several components. The first doublet with peaks at 84.0 and 87.7 eV is characteristic for metallic gold [31][32][33][34]. Metal Au 0 represents ∼ 43% of the total gold deposited and was assigned to the particles of 2 nm observed by HRTEM (Fig.…”

Section: Au/acf Catalysts Formationmentioning

confidence: 93%

Highly dispersed gold on activated carbon fibers for low-temperature CO oxidation

Bulushev

Yuranov

Suvorova

et al. 2004

Journal of Catalysis

202

132

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“…The presence of a sharp peak centered at 83.9 AE 0.2 eV, relative to the Au 4f7/2 signal, suggests the existence of the metallic state only. [12] By using gold particles of different size in the range 3-6 nm, we observed a catalytic activity inversely proportional to the diameter at the total gold concentration of 3.2 10 À5 m ( Figure 5). Particles larger than 6 nm deviate from linearity and a sharp cut off is observed at approximately 10 nm.…”

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confidence: 85%

The Catalytic Activity of “Naked” Gold Particles

et al. 2004

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The metal-support interaction in catalysis is of relevance both for academic studies and for industrial applications, and theoretical concepts have contributed to understanding the basic principles behind this interaction. [1] In most cases, however, the metal-support interaction is only described in terms of catalytic behavior and its nature often remains debatable. In recent years interest in gold catalysts for various applications in organic and inorganic chemistry [2] has increased and, our and other research groups have investigated the liquid-phase oxidation of polyol, [3][4][5][6][7] aminoalcohols, [8] and glucose [9] to carboxylates, and the gas-phase oxidation of alcohols to the corresponding carbonyl derivatives [10] using metal particles supported on different materials. In liquid-phase applications, carbon was found to be the support of choice, and in the case of ethane-1,2-diol oxidation, by comparing different commercial carbons, a tentative hypothesis of metal-support interactions, connected to the density of phenolic groups at the carbon surface, was formulated.[11] However, the synergism between gold particles and carbon was not demonstrated and this point remained unresolved.Although gold colloids have widely been employed to prepare supported gold catalysts, no report of particles derived from colloidal dispersion being used as catalysts has appeared. We have now found that, under controlled conditions, water-dispersed gold sol exhibits a surprising activity when used as "naked particles", that is, in the absence of common protectors as polyvinylalcohol (PVA), polyvinylpyrrolidone (PVP), tetrahydroxymethylphosphonium chloride (THPC). As a model reaction, we have investigated the aerobic oxidation of glucose to gluconate which occurs under mild conditions.As shown in the conversion-time plot (Figure 1), naked gold particles having a mean diameter of 3.6 nm behave as an active catalyst allowing 21 % glucose conversion in the first 200 s.These particles are produced as a colloidal sol by reducing HAuCl 4 in the presence of a large excess of glucose acting either as reagent or protector. From the initial rate, a specific molar activity of 18 043 mol gluconate [mol Au] À1 h À1 (calculated with respect to the total gold) can be derived. Under similar conditions, Cu, Ag, Pd, and Pt colloidal particles of similar dimension (3-5 nm) were scarcely active. During the catalytic test, gold coagulated into larger particles owing to the formation of sodium gluconate that, as is common with other electrolytes, promoted sol coagulation leaving a colorless, inactive solution after about 400 s. The growth of gold crystallites during the reaction has been followed by X-ray diffraction (XRD) analysis at various time intervals, after sol immobilization on carbon (Figure 2).Gold particles are also poisoned by sulfur compounds, such as sulfides and sulfites, and inhibited by protecting molecules, such as polyvinyl alcohol. Although the short life of the gold sol does not allow its use as a practical catalyst, its acti...

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“…The size of the interface between the Au particles and Fe 2 O 3 is an important factor influencing the catalytic response of supported Au catalysts in reaction of CO oxidation [61]. It is generally accepted that the oxidation of CO over transition-metal oxides such as Fe 2 O 3 , MnO 2 , and CuO follows a Mars-van Krevelen mechanism, in which lattice oxygen is involved in CO oxidation and the reduced surface of the catalyst is reoxidized by CO/O 2 feed mixture [62]. A high activity for CO oxidation can be achieved due to quick redox cycle through the spillover of reactive oxygen from the support to Au [63].…”

Section: Catalytic Oxidation Of Carbonmentioning

confidence: 99%

Low Temperature Oxidation of Carbon Monoxide over Mesoporous Au-Fe₂O₃Catalysts

Alshehri

Narasimharao

2017

Journal of Nanomaterials

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Low temperature active and stable mesoporous Au (0.1, 0.2, 0.5, and 1.0 wt.%) supported -Fe 2 O 3 catalysts were prepared via deposition-precipitation method. The H 2 -pretreated catalyst with 0.5 wt.% Au loading offered CO conversion of 100% at 323 K and showed continual activity for at least 120 h. X-ray diffraction and transmission electron microscopy analysis indicate that Au species were highly dispersed as nanoparticles (20-40 nm) on the surface of -Fe 2 O 3 support even after thermal treatment at 773 K. The N 2 -physisorption measurements show that the synthesized -Fe 2 O 3 support and Au-Fe 2 O 3 nanocomposites possessed mesopores with high specific surface area of about 158 m 2 g −1 . X-ray photoelectron spectroscopy and H 2 -TPR results reveal that the Au species exist in metallic and partially oxidized state due to strong interaction with the support. Effective Au-Fe 2 O 3 interaction resulted in a high activity for Au nanoparticles, locally generated by the thermal treatment at 773 K in air.

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Influence of catalyst pretreatments on volatile organic compounds oxidation over gold/iron oxide

Cited by 163 publications

References 35 publications

Highly dispersed gold on activated carbon fibers for low-temperature CO oxidation

Highly dispersed gold on activated carbon fibers for low-temperature CO oxidation

The Catalytic Activity of “Naked” Gold Particles

Low Temperature Oxidation of Carbon Monoxide over Mesoporous Au-Fe₂O₃Catalysts

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Influence of catalyst pretreatments on volatile organic compounds oxidation over gold/iron oxide

Cited by 163 publications

References 35 publications

Highly dispersed gold on activated carbon fibers for low-temperature CO oxidation

Highly dispersed gold on activated carbon fibers for low-temperature CO oxidation

The Catalytic Activity of “Naked” Gold Particles

Low Temperature Oxidation of Carbon Monoxide over Mesoporous Au-Fe2O3Catalysts

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Product

Resources

About

Low Temperature Oxidation of Carbon Monoxide over Mesoporous Au-Fe₂O₃Catalysts