Dark- and Photoreactions of Ethanol and Acetaldehyde over TiO2/Carbon Molecular Sieve Fibers

Reztsova, T; Chang, C. H.; Koresh, Jacob E.; Idriss, Hicham

doi:10.1006/jcat.1999.2520

Cited by 42 publications

(29 citation statements)

References 81 publications

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“…The signal of all, but m/e 44 products return to the base line. The remaining m/e 44 signal is due to total oxidation of traces of ethanol to CO 2 (as it is not mirrored by m/e 29 and m/e 15; fingerprint of acetaldehyde); it is worth indicating that photooxidation of ethanol is a set of consecutive reactions studied in some details previously on TiO 2 [30] as well as on Ru/TiO 2 [31]. Table 3 presents the computed peak areas of the mass spectrometer signals of the main products.…”

Section: Resultsmentioning

confidence: 92%

Ethanol photoreactions over Au–Pd/TiO2

et al. 2014

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A prototype Au-Pd/TiO 2 catalyst was prepared, characterized and tested for the photoreaction of ethanol. XPS Au4f and Pd3d indicated that the as-prepared material is composed of metallic Au, metallic Pd as well oxidized Pd (Pd 2? ). Ar ion sputtering (5 min) of the catalyst surface resulted in almost total reduction of Pd 2? to metallic Pd in addition to considerable reduction of surface Ti cations to Ti 3? and Ti 2? cations; XPS Au4f lines were not affected. Transmission electron microscopic studies indicated that Au particles have a mean particle size of about 3.5 nm while Pd particles are smaller 1-1.5 nm in size. UV excitation of the catalyst in ultrahigh vacuum (UHV) conditions resulted in the formation of acetaldehyde and hydrogen in addition to photodesorption of the reactant ethanol. Hydrogen production, representing ca. 30 % of the desorbing products, was delayed compared to acetaldehyde desorption. This was interpreted as due to kinetic effect whereby initially most electrons transferred to the conduction band are trapped by surface hydroxyls as well inevitable presence of oxygen in the powder accelerating acetaldehyde formation (dehydrogenation). Only once most oxygen-containing species have reacted and molecular hydrogen was formed. To our knowledge, this is the first UHV in situ study of hydrogen production from ethanol photocatalytically over M/TiO 2 system.

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Section: Resultsmentioning

confidence: 92%

Ethanol photoreactions over Au–Pd/TiO2

et al. 2014

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“…Desorption of unreacted ACA was also detected in this temperature range, in agreement with the desorption of ACA over TiO 2 /carbon molecular sieve fibers. [35] Crotonaldehyde, which is formed by aldol-condensation during ACA adsorption, desorbed over this temperature range, in which a small amount of butadiene was also detected.…”

Section: Tio 2 and Cu/tiomentioning

confidence: 81%

Probing Surface Properties and Reaction Intermediates During Heterogeneous Catalytic Oxidation of Acetaldehyde

Kydd¹,

Teoh²,

Scott³

et al. 2009

ChemCatChem

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The influence of Cu on various metal oxide supports was investigated for the catalytic oxidation of acetaldehyde (ACA). The activity of the catalysts towards ACA conversion and the CO2 yield decrease in the order: Cu/CeO2>Cu/TiO2≈Cu/ZrO2> Cu/Al2O3>Cu/SiO2. Spontaneous adsorptive conversion of ACA to surface carboxylates, such as bridging and bidentate acetates, was detected over the basic supports CeO2, TiO2, and ZrO2. Detailed temperature‐programmed studies found the high activity of Cu/CeO2 to stem mainly from the intrinsically high activity of the CeO2 support. In contrast, similar studies on Cu/TiO2 demonstrated the activity improvements imparted by Cu were predominantly additive. Despite the difference in origin of ACA oxidation activity over Cu/CeO2 and Cu/TiO2, the overall concerted effects of basicity‐induced carboxylate formation and availability of surface oxygen were thought to be overriding factors crucial in the overall catalytic reactivity.

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“…As indicated above, in competition with this process, electron-hole recombination takes place. The photo-catalytic activity has been shown to depend on several parameters such as surface structure (Brinkely and Engel 2000), particles size (Reztova et al 1999;Furube et al 1999), defects (Henderson et al 1999), doping (Karakitsu and Verykios 1993;Hengelin 1989) and the formation of n-p compounds (Wang et al 2005). There are basically three requirements for a high catalytic activity:…”

Section: Steady State Reactions Of Acetic Acid Under Uv Irradiationmentioning

confidence: 98%

“…11. The reaction intermediates have been studied on powder TiO 2 and are found to involve the dehydrogenation product CH 3 CHO (Reztova et al 1999) formed by the removal of the electron from the radical of (15):…”

Section: à2mentioning

confidence: 99%

Photoreactions of Organic Compounds with TiO2 Single Crystal Surfaces

Idriss¹

2010

Nanostructure Science and Technology

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In this work the photoreactions of two organic molecules: acetic acid and ethanol, over rutile TiO 2 (110), TiO 2 (011) and the (011) reconstructed surface of TiO 2 (001) single crystals are presented. Comparison with the corresponding dark reaction is also given. The steady state reaction at 320 K of acetic acid over the {011}-faceted surface of TiO 2 (001) under UV irradiation indicated the formation of methane, ethane and CO 2 . These are the expected products of the socalled "Photo-Kolbe" reaction of acetic acid. While the formation of methane was not sensitive to the addition of molecular oxygen and could be carried out in UHV conditions catalytically that of ethane required the continual addition of gas phase molecular oxygen for its photo-catalytic production to occur. The quantum yield of the reaction was computed equal to 0.05, while the depletion layer width and barrier height were found equal to 18 nm and 0.18 eV, respectively. The photoreaction of ethanol conducted over the rutile TiO 2 (110) surface indicated that, oxidation of ethoxides to acetate species occurs under molecular oxygen within the investigated pressure range (10 À6 -10 À9 torr). In the absence of molecular oxygen (base pressure 2 Â 10 À10 torr) or in presence of molecular hydrogen with a pressure up to 10 À6 torr negligible photo-reaction occurred. Fitting the observed decay of ethoxides upon irradiation with a Langmuir-type analysis, as a function of gas phase molecular oxygen, the binding constant of the later was found equal to ca. 2 Â 10 7 torr À1 . This value, together with the initial surface coverage of ethoxide of 0.5 with respect to surface Ti atoms, may indicate that the number of adsorbed molecular oxygen needed for maximum reaction rate is similar to that of the free surface Ti atoms.

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Dark- and Photoreactions of Ethanol and Acetaldehyde over TiO2/Carbon Molecular Sieve Fibers

Cited by 42 publications

References 81 publications

Ethanol photoreactions over Au–Pd/TiO2

Ethanol photoreactions over Au–Pd/TiO2

Probing Surface Properties and Reaction Intermediates During Heterogeneous Catalytic Oxidation of Acetaldehyde

Photoreactions of Organic Compounds with TiO2 Single Crystal Surfaces

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