Formation of Acetic Acid by Aqueous‐Phase Oxidation of Ethanol with Air in the Presence of a Heterogeneous Gold Catalyst

Christensen, Claus H.; Jørgensen, Bo; Rass‐Hansen, Jeppe; Egeblad, Kresten; Madsen, Robert; Kegnæs, Søren; Hansen, Steen; Hansen, Mike R.; Andersen, Hans Christian; Riisager, Anders

doi:10.1002/anie.200601180

Cited by 217 publications

(151 citation statements)

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“…Gold on titanium oxide or zinc oxides showed a high initial activity towards ethanol oxidation. Ethanol conversions of > 90% was achieved (but a slight oxygen deficiency was used in these runs) After 10 h about 80% of ethanol conversion was observed, a result similar to that reported by Christensen et al where 1% Au/MgAl 2 O 4 was used as a catalyst [27]. An ethanol conversion of 93% was observed when 1% Au/TiO 2 was used in reactions conducted for longer than 20h (slight oxygen deficiency used).…”

Section: Resultssupporting

confidence: 87%

“…The behavior of gold/titania in ethanol oxidation was previously reported [27]. We have also investigated the catalyst lifetime of Au/TiO 2 in ethanol oxidation reaction, as it has not been reported before, and have also noted the gold leaching tendencies of some of these catalysts.…”

Section: Introductionmentioning

confidence: 61%

“…An intense interest in gold catalysis followed the seminal work of Haruta et al [25] and Hutchings et al [26] in CO oxidation and acetylene hydrochlorination respectively. Recently, it has been found that Au supported catalysts are selective and stable for the oxidation of various alcohols to their corresponding aldehydes, acids and ketones [27][28][29]. In this emerging field of "green" oxidation chemistry, catalysts comprising gold nanoparticles have attained a very prominent role [30].…”

Section: Introductionmentioning

confidence: 99%

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Acetic acid production by selective oxidation of ethanol using Au catalysts supported on various metal oxide

2009

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The liquid-phase oxidation of ethanol to acetic acid using Au catalysts supported on various metal oxides was studied at 150°C using molecular oxygen as stoichiometric oxidant. Catalysts containing 1 wt% Au supported on TiO 2 , Al 2 O 3 , and ZnO were examined for ethanol oxidation. The results showed that ZnO and TiO 2 gave higher initial activities as supports for gold in ethanol oxidation, followed by Al 2 O 3 . Ethanol conversions of >90% and selectivities to acetic acid of >95% were achieved when using ZnO and TiO 2 as supports under conditions where a slight oxygen deficiency was used. With a slight excess of oxygen present initially, ethanol conversions of 99.4%, and a selectivity to acetic acid selectivity of 99.8% could be achieved. Gold leaching seemed to be very apparent with alumina as support and also, after continued use with titania-based catalysts. The use of higher initial concentrations of ethanol (range studied 5 -40 mass% ethanol in water) led to higher ethyl acetate selectivities. High acetic acid selectivities were seen for relatively low (5-10 mass%) initial ethanol concentrations.

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Section: Resultssupporting

confidence: 87%

Section: Introductionmentioning

confidence: 61%

Section: Introductionmentioning

confidence: 99%

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Acetic acid production by selective oxidation of ethanol using Au catalysts supported on various metal oxide

2009

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“…10 Indeed, the field of Au catalysis may be described largely in a regime of exploratory science, with numerous research groups working to discover new reactions and investigate new potential applications for Au-based materials.…”

Section: Introductionmentioning

confidence: 99%

Adsorption of CO on Supported Gold Nanoparticle Catalysts: A Comparative Study

2009

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The adsorption of CO on three different gold nanoparticle catalysts supported on high surface area TiO 2 was studied using infrared transmission spectroscopy at room temperature and CO pressures typically used in CO oxidation reactions. The three, real-world catalysts were Au catalysts synthesized in our laboratory from thiol monolayer protected clusters (MPCs) and two commercial catalysts from the World Gold Council (WGC and AuTEK). Within experimental reproducibility, the adsorption data for the three catalysts are indistinguishable. While showing approximately Langmuir behavior, the adsorption data also show coverage dependence, as others have observed for many catalyst systems. Two approaches were used to fit the data, a two-site model and a variable binding constant model. The two-site Langmuir model yielded strong (36%) and weak (64%) binding constants of 2740 and 146 atm -1 , respectively. Alternatively, using a sliding-tangent Langmuir fit gave a variable binding constant of 2670-120 atm -1 at room temperature for coverage θ ) 0-0.8. The heat of adsorption was then extracted from the binding constants using a literature value for -T∆S. These values were determined as ∆H ) -64 and -56 kJ/mol for strong and weak binding according to the two-site model and ∆H ) -63 to -56 kJ/mol for coverage θ ) 0-0.8 for the variable binding constant model. These values agree well with literature values obtained (i) using supported catalysts under higher pressures and (ii) using model catalysts under higher pressures and ultrahigh vacuum conditions.

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“…[1][2] In spite of their technological and scientific importance, the underlying catalytic mechanism remains largely unclear in literature. Many plausible hypotheses are related to the Au/oxide interface, which either plays a role in controlling the morphology of Au nanoparticles or has a direct contribution to their catalytic behaviors.…”

mentioning

confidence: 99%

Effect of Interfacial Structure on Gold-assisted Growth of Oxides

Zhou

Liu

et al. 2015

Microsc Microanal

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, have profound significance for many energy-related reactions such as low-temperature CO oxidation and selective oxidation of alcohols. [1][2] In spite of their technological and scientific importance, the underlying catalytic mechanism remains largely unclear in literature. Many plausible hypotheses are related to the Au/oxide interface, which either plays a role in controlling the morphology of Au nanoparticles or has a direct contribution to their catalytic behaviors. [3][4][5] Nevertheless, it is crucial to fully clarify the interfacial structure, including the atomic arrangement and chemical bonding nature. In order to facilitate structural characterization, we synthesized model systems with Au nanoparticles on a single-crystal oxide support by the presence of an Au overlayer and the application of heat.A new phenomenon, we have discovered recently in those systems, involves the dewetted gold nanoparticle acting as a seed causing crystalline substrates to spontaneously grow underneath the gold nanoparticle.[5] Fig.1 shows intricate nano-structures including dewetted gold nanoparticles supporting by the regrowth oxide bases. As shown in the HAADF (Z-contrast) images, gold nanoparticles, with well-defined facets on crystalline bases, share the same contrast with the substrate. The composition and the crystallographic orientation of the bases are further confirmed by the electron energy-loss spectroscopy and diffraction techniques, respectively. The formation of such intricate nanostructures depends on a few parameters such as the thickness of the Au overlayer and the heating treatment.Limited to the Au-TiO 2 and Au-MgAl 2 O 4 systems we have studied so far, the intricate nano-structures include: a). gold nanoparticles, normally close to the Wulff equilibrium shape, have a few preferential crystallographic orientations with respect to the single-crystal substrates; b). regrowth oxide bases, with a well-defined shape, are epitaxially aligned with the single-crystal substrates; and c). interfacial monolayers, which have completely different atomic arrangement, extends both the gold and oxide lattices. The formation of such interfacial monolayers always accompanies with the regrowth of the substrates. Those unique interfacial structures may be responsible for the epitaxial growth of the substrate under self-organized gold nanoparticles.The interfacial monolayers referred as rearranged Au atoms between the gold and oxide lattices. We detected an interfacial bilayer between the gold nanoparticles and spinel bases, labeled by the red and blue arrows in Fig.2. On top of monolayer A with Au atoms extending the spinel lattice, the monolayer B exhibits an oscillating contrast in the HAADF image when viewed from [110] MgAl2O4 . In the case of Au-TiO 2 with much large lattice mismatch, different interfacial structures have been observed with different crystallographic orientations between the gold and rutile lattice. Fig.3 shows the interfacial monolayers varies from single monolayer to a few monolayers viewed from [001...

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Formation of Acetic Acid by Aqueous‐Phase Oxidation of Ethanol with Air in the Presence of a Heterogeneous Gold Catalyst

Cited by 217 publications

References 28 publications

Acetic acid production by selective oxidation of ethanol using Au catalysts supported on various metal oxide

Acetic acid production by selective oxidation of ethanol using Au catalysts supported on various metal oxide

Adsorption of CO on Supported Gold Nanoparticle Catalysts: A Comparative Study

Effect of Interfacial Structure on Gold-assisted Growth of Oxides

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