Issue 10, 2014

Gas-phase oxidation of ethanol over Au/TiO2 catalysts to probe metal–support interactions

Abstract

Ethanol and oxygen were converted over titania and gold nanoparticles supported on titania to investigate the reactivity of the support, the influence of the metal, and the role of metal–support interactions. In addition to determining the degrees of conversion and the yields as a function of temperature, temperature-programmed desorption and diffuse reflectance infrared spectroscopy were performed in fixed-bed reactors under continuous flow conditions. Over pure TiO2 mainly selective oxidative dehydrogenation to acetaldehyde and water and, to a minor extent, total oxidation to CO2 and H2O were found to occur above 500 K. The presence of Au nanoparticles additionally induced the selective oxidation to acetaldehyde and H2O at temperatures below 400 K. Thus, the Au/TiO2 catalyst shows bifunctional properties in oxygen activation needed for the selective oxidation of ethanol. Ethoxy species were detected by IR spectroscopy, which are identified as intermediate species in ethanol conversion. In contrast, strongly bound acetates and acetic acid acted as catalyst poisons for the selective low-temperature oxidation route but not for the high-temperature route. Selective low-temperature oxidation is assumed to occur at the perimeter of the Au nanoparticles, which additionally enhance the high-temperature oxidation route on TiO2 pointing to a Mars–van Krevelen mechanism based on an enhanced reducibility of TiO2.

Graphical abstract: Gas-phase oxidation of ethanol over Au/TiO2 catalysts to probe metal–support interactions

Article information

Article type
Paper
Submitted
15 huhti 2014
Accepted
29 touko 2014
First published
29 touko 2014

Catal. Sci. Technol., 2014,4, 3495-3504

Author version available

Gas-phase oxidation of ethanol over Au/TiO2 catalysts to probe metal–support interactions

M. C. Holz, K. Tölle and M. Muhler, Catal. Sci. Technol., 2014, 4, 3495 DOI: 10.1039/C4CY00493K

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