## 3 Results
### Catalyst Characterization
#### 3.2.2 PXRD measurements  
PXRD analysis was performed for identification of the crystal structure of the catalysts. The average size of ceria (D\({}_{\text{ceria}}\)) and lattice constant (\(\alpha_{\text{ceria}}\)) are listed in Table 1. Very similar values were measured for all samples, supported on pure ceria and CeO\({}_{2}\)/Al\({}_{2}\)O\({}_{3}\) or Y-doped CeO\({}_{2}\)/Al\({}_{2}\)O\({}_{3}\) prepared by mechanochemical mixing. Significantly larger average crystallite size of ceria (12.6 and 16.8 nm) was calculated in gold-based catalysts on prepared by impregnation supports. Slight contraction of ceria lattice parameter was also observed, that should be related to the size differences. Recently, [PERSON] et al. observed that the increase of crystallites size was accompanied with a decrease in the lattice \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample** & **S\({}_{\text{BET}}\)** & **V\({}_{\text{pore}}\)** & **D\({}_{\text{pore}}\)** & **D\({}_{\text{ceria}}\)** & **\(\alpha_{\text{ceria}}\)** \\  & **(m\({}^{2}\cdot\)g\({}^{-1}\))** & **(cm\({}^{3}\cdot\)g\({}^{-1}\))** & **(nm)** & **(nm)** & **(nm)** \\ \hline \(\gamma\)-Al\({}_{2}\)O\({}_{3}\) & 200 & 0.53 & 10.6 & - & - \\ Au/Al & 204 & 0.51 & 10.0 & - & - \\ Pd/Al & 195.8 & 0.52 & 9.7 & - & - \\ Pd-Au/Al & 193.7 & 0.52 & 9.6 & - & - \\ CeO\({}_{2}\) & 63.0 & 0.29 & 20.3 & - & - \\ Au/Ce & 65.0 & 0.28 & 17.1 & 4.9 & 0.5418(7) \\ Pd/Ce & 67.6 & 0.28 & 16.5 & 6.2 & 0.5424(4) \\ Pd-Au/Ce & 62.5 & 0.29 & 22.5 & 5.1 & 0.5421(7) \\ CeAl & 165.0 & 0.39 & 9.5 & - & - \\ Au/CeAl & 147.9 & 0.39 & 9.8 & 6.2 & 0.5426(1) \\ Pd/CeAl & 161.2 & 0.45 & 9.5 & 5.8 & 0.5424(1) \\ Pd-Au/CeAl & 151.6 & 0.37 & 9.6 & 5.6 & 0.5425(1) \\ YCeAl & 168.0 & 0.43 & 10.0 & - & - \\ Au/YCeAl & 160.0 & 0.39 & 9.7 & 6.2 & 0.5428(1) \\ Pd/YCeAl & 166.4 & 0.40 & 9.6 & 5.8 & 0.5420(1) \\ Pd-Au/YCeAl & 157.9 & 0.38 & 9.6 & 5.8 & 0.5425(1) \\ Au/CeAl IM & 127.0 (142 \({}^{*}\)) & 0.27 & 8.6 & 16.8 & 0.5398(1) \\ Au/YCeAl IM & 125.0 (135 \({}^{*}\)) & 0.27 & 8.7 & 12.6 & 0.5402(7) \\ \hline \hline \end{tabular} \({}^{*}\)S\({}_{\text{BET}}\) of CeAl IM and YCeAl IM.  
\end{table} 
Table 1: Specific surface area (S\({}_{\text{BET}}\)), pore volume (V\({}_{\text{pore}}\)), pore size (D\({}_{\text{pore}}\)), average size (D\({}_{\text{ceria}}\)) and lattice parameter (\(\alpha\)) of ceria estimated by PXRD. parameter [28]. Partial insertion of some Al\({}^{3+}\) in the ceria lattice, because of smaller ionic radius (Al\({}^{3+}\) < 0.8 A, Ce\({}^{4+}\)-0.97 A) could be also suggested. The PXRD patterns are grouped in Figure 4a-d depending on the type of support. As displayed in Figure 4a, four diffraction peaks at 20 = 28.5\({}^{\circ}\), 33.1\({}^{\circ}\), 47.5\({}^{\circ}\) and 56.4\({}^{\circ}\) indicated the presence of CeO\({}_{2}\) in the cubic crystal structure of fluorite-type. There were no reflections related to gold or palladium, because of their small amounts and high dispersion. The calculation of the average gold particles size on the basis of High resolution transmission electron microscopy (HRTEM) and high angle annular dark field (HAADF) measurements indicated that despite the support preparation method, the size was very similar (2-3 nm) [29; 30]. In contrast, very strong diffraction peaks at 20 = 38.2\({}^{\circ}\) and 44.4\({}^{\circ}\) due to the formation of quite big gold particles were observed in the patterns of Au/Al and Pd-Au/Al (Figure 4b). The calculated average size was 32 and 40 nm, respectively. The larger size of gold in the bimetallic sample probably was caused by additional thermal treatment at 400 \({}^{\circ}\)C after deposition of Pd. The peaks of CeO\({}_{2}\) dominate in the diffraction patterns of all samples, supported on CeO\({}_{2}\)/Al\({}_{2}\)O\({}_{3}\) or Y-doped CeO\({}_{2}\)/Al\({}_{2}\)O\({}_{3}\) (Figure 4c,d). Weak contribution of alumina is visible about 20 = 38\({}^{\circ}\) together with broadening of the ceria peak at 20 = 47.5\({}^{\circ}\). Y\({}_{2}\)O\({}_{3}\) phase was not detected by PXRD.