(762c) Interfacial Perimeter Sites of Au-TiOx in Isopropanol Decomposition

Au-TiO_x interfacial perimeter sites was found to be very active for dehydrogenation to acetone by comparing Au/SiO₂, TiO_x/SiO₂ and TiO_x/[Au/SiO₂] in isopropanol decomposition. Although metal-support perimeter sites have been regarded active in different catalytic reactions,¹ dehydrogenation of isopropanol at these sites has only been addressed recently.^{2, 3} Two TiO_x coverage, corresponding to 0.5 and 3 monolayer equivalent of TiO₂ and loadings of Ti 0.8-1.1 and 4.1-5.3 wt.%, respectively, were prepared on SiO₂ or Au/SiO₂. TiO_x/SiO₂, which possessed only Lewis acid sites as determined by FTIR spectroscopy and pyridine adsorption, catalyzed only dehydration of isopropanol to propene. The ratio of propene formation rate on 3MonoTiO₂/SiO₂ to that on Ti/SiO₂ was 8. Unlike TiO_x/SiO₂, acetone as well as propene was produced over Au/SiO₂ and TiO_x/[Au/SiO₂] with a high acetone selectivity of 50-85%. However, Au/SiO₂ was much less active than TiO_x/[Au/SiO₂]. The rates of propene and acetone formation on TiO_x/[Au/SiO₂] were 3-16 and 8-9 times, respectively, higher than on Au/SiO₂. In addition, relative to TiO_x/SiO₂, the propene formation rates on TiO_x/[Au/SiO₂] was 35-57% lower. These results suggested that the active sites for dehydrogenation of isopropanol were at the Au-TiO_x interfacial perimeters. The decreases in propene formation rates may be contributed to the creation of Au-TiO_x interfacial perimeters at the expense of TiO_x free from Au. The kinetic results of reaction order and activation energies will also be presented.

1. Y. Y. Wu, N. A. Mashayekhi and H. H. Kung, Catal. Sci. Technol., 2013, 3, 2881-2891.

2. Z. Martinez-Ramirez, J. A. Gonzalez-Calderon, A. Almendarez-Camarillo and J. C. Fierro-Gonzalez, Surf. Sci., 2012, 606, 1167-1172.

3. M. C. Holz, K. Kahler, K. Tolle, A. C. van Veen and M. Muhler, Phys. Status Solidi B, 2013, 250, 1094-1106.