Effect of Support Structure in Au/Al₂O₃-TiO₂ Catalysts in Low-Temperature CO Oxidation

¹ AGH University of Science and Technology, Faculty of Materials Science and Ceramic, Al. Mickiewicza 30, 30-059 Krakow, Poland
² Foundry Research Institute, Department of Non-Ferrous Metal Alloys, Zak opiańska 73, 30-418 Krakow, Poland
³ Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warsaw, Poland

^a Corresponding author: rajska@agh.edu.pl

Abstract

The aim of this study was to determine the effect of the support phase composition (Al₂O₃–TiO₂) and the addition of gold on the catalytic properties in low-temperature CO oxidation. In this paper, the physicochemical properties and results of catalytic measurements performed for the obtained samples were investigated. The catalyst carriers were prepared using the sol-gel method with alkoxide Al(C₃H₇O)₃ and Ti(C₃H₇O)₄ employed to obtain the corresponding oxides, in the case of which the molar ratio (Al₂O₃:TiO₂) was 0.75:0.25, 0.50:0.50 and 0.25:0.75, thus corresponding to the molar ratio of the Al:Ti elements, i.e. 1.5:0.25, 2:1 and 0.5:0.75 respectively. The gold catalysts were prepared through the deposition of gold by the deposition precipitation method using the theoretical loading of Au 2 wt.%. To examine the effect of the phase composition on the catalytic activity of the obtained samples, appropriate carriers were calcined at two different temperatures: 500°C and 1350°C. This made it possible to obtain the intended polymorphs of aluminum oxide and titanium dioxide (γ–Al₂O₃, α–Al₂O₃, anatase and rutile). For certain samples, calcined at a high temperature, the aluminum titanium oxide (Al₂O₅Ti) phase was also observed. The prepared samples were characterized by XRD, BET, SEM, and additionally both particle size distribution analysis and measurements of the catalytic activity were performed. The highest catalytic activity was shown by Au/75Al–25Ti_LT, where T₉₀ was about 110°C.