Influence of the support in aqueous phase oxidation of ethanol on gold/metal oxide catalysts studied by ATR-IR spectroscopy under working conditions

Waheed, Ammara; Wang, Xianwei; Maeda, Nobutaka; Meier, Daniel M.; Ishida, Tamao; Murayama, Toru; Haruta, Masatake; Baiker, A.

doi:10.1016/j.catcom.2020.106183

Cited by 2 publications

(1 citation statement)

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“…The intensity of the ν(C–H) band at 2710 cm –1 decreased with time, suggesting that the C–H bond of the formyl group was dissociated during the reaction. The band at around 1020–1110 cm –1 was assigned to both of ν(C–O) of the chemisorbed ethoxide on Au and molecularly physisorbed ethanol. − The bands centered at 1240 and 1400 cm –1 were attributed to the C–O stretching vibration of ethanol, and the mixture of the O–H bending vibration and the C–H bending vibration of ethanol. − During the reaction, the band at 1725 cm –1 (ν(CO)) readily decreased and a new band was observed at 1685 cm –1 , suggesting that octanal was transformed into octanoate. In the absence of octanal, no peak attributed to the carbonyl CO vibration was observed, which can exclude that the oxidative esterification of ethanol to ethyl acetate via the formation of acetaldehyde did not occur under the measurement conditions (Figure S18).…”

Section: Resultsmentioning

confidence: 99%

Gold/Substituted Hydroxyapatites for Oxidative Esterification: Control of Thin Apatite Layer on Gold Based on Strong Metal–Support Interaction (SMSI) Results in High Activity

Taketoshi

Gangarajula

Sodenaga

et al. 2023

ACS Appl. Mater. Interfaces

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Gold nanoparticles (Au NPs) deposited on various cationand anion-substituted hydroxyapatites (Au/sHAPs) show oxidative strong metal−support interaction (SMSI), wherein a thin layer of the sHAP covered the surface of the Au NPs by heat treatment in an oxidative atmosphere. Calcination of Au/sHAPs at 300 °C caused a partial SMSI and that at 500 °C gave fully encapsulated Au NPs. We investigated the influence of the substituted ions in sHAP and the degree of the oxidative SMSI on the catalytic performance of Au/sHAPs for oxidative esterification of octanal or 1-octanol with ethanol to obtain ethyl octanoate. The catalytic activity depends on the size of the Au NPs but not on the support used, owing to the similarity of the acid and base properties of sHAPs except for Au/CaFAP. The presence of a large number of acidic sites on CaFAP lowered the product selectivity, but all other sHAPs exhibited similar activity when the Au particle size was almost the same, owing to the similarity of the acid and base properties. Au/sHAPs_O 2 with SMSI exhibited higher catalytic activity than Au/sHAPs_H 2 without SMSI despite the fact that the number of exposed surface Au atoms was decreased by the SMSI. In addition, the oxidative esterification reaction proceeded even though the Au NPs were fully covered by the sHAP layer when the thickness of the layer was controlled to be less than 1 nm. The substrate can access the surfaces of the Au NPs covered by the thin sHAP layer (<1 nm), and the presence of the sHAP structure in close contact with the Au NPs resulted in significantly higher catalytic activity compared with that for fully exposed Au NPs deposited on the sHAPs. This result suggests that maximizing the contact area between the Au NPs and the sHAP support based on the SMSI enhances the catalytic activity of Au.

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