# Nickel-Based Structured Catalysts for Indirect Internal Reforming of Methane
## 3 Results and Discussion  
### XRD and Textural Characterization of Ni-SmDC Catalyst  
Figure 1 displays the X-ray diffraction patterns of Ni-SmDC powders calcined at 750 \({}^{\circ}\)C and after a reduction treatment in H\({}_{2}\) up to 800 \({}^{\circ}\)C. The crystallite sizes calculated by [PERSON]'s equation are reported in Table 1. The XRD pattern of the calcined sample shows well-defined peaks of the cubic fluorite phase of CeO\({}_{2}\) (JCPDS 81-0792) with Fm-3m space group [34] and weak peaks of NiO cubic phase (JCPDS 78-0643). No trace of Sm\({}_{2}\)O\({}_{3}\) oxide cubic phase was revealed, confirming that Sm forms a Ce\({}_{0.85}\)Sm\({}_{0.15}\)O\({}_{2\cdot 5}\) solid solution ascribable to the good dispersion of Ce\({}^{3+}\) and Sm\({}^{3+}\) cations' precursors during the synthetic procedure. The NiO low-intensity peaks at 37.3\({}^{\circ}\) and 43.3\({}^{\circ}\) were due to the low NiO content, but also to the fact that a limited part of Ni\({}^{2+}\) ions were included into the cubic fluorite structure of the Ce\({}_{0.85}\)Sm\({}_{0.15}\)O\({}_{2\cdot 8}\) phase [29]. After reduction at 800 \({}^{\circ}\)C, Ce\({}_{0.85}\)Sm\({}_{0.15}\)O\({}_{2\cdot 8}\) phase remained unchanged and no decomposition into Sm\({}_{2}\)O\({}_{3}\)-CeO\({}_{2}\) oxides was observed. Narrow peaks and correspondingly increased crystallites' sizes from 18 to 20 nm were detected. NiO was fully reduced to Ni\({}^{0}\) metallic phase with cubic structure (JCPDS 87-0712). Ni\({}^{0}\) showed narrow peaks with a 20 nm crystallite size, which was larger than that of NiO, suggesting coarsening and/or aggregation of Ni\({}^{0}\) particles was occurring at high temperature. Figure 1 shows the nitrogen adsorption-desorption isotherms and the pore-size distribution (PSD) of Ni-SmDC powder samples after calcination at 750 \({}^{\circ}\)C and after reduction at 800 \({}^{\circ}\)C. The textural properties are reported in Table 1. The isotherms give a qualitative assessment of the porous microstructure. The isotherms of both calcined and reduced samples exhibited a similar shape, comparable to types II and III, according to the IUPAC (International Union of Pure and Applied Chemistry) classification [35], indicating macroporous materials, with the N\({}_{2}\) adsorption-desorption \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{2}{c}{**Crystallites Size (nm)**} & \multicolumn{2}{c}{**Surface Area**} & \multicolumn{1}{c}{**Pore Volume**} & \multicolumn{1}{c}{**Pore Size**} \\ \cline{2-7}  & **SmDC** & **NiO** & **Ni\({}^{0}\)** & **(m\({}^{2}\) g\({}^{-1}\))** & **(cm\({}^{3}\) g\({}^{-1}\))** & **(nm)** \\ \hline Ni-SmDC & 18 & 14 & - & 31 & 0.15 & 18 \\ Ni-SmDC\_r (*) & 20 & - & 20 & 15 & 0.07 & 23 \\ \hline \hline \end{tabular} \({}^{\text{(a)}}\) Sample after reduction treatment at 800 \({}^{\circ}\)C.  
\end{table} 
Table 1: Textural properties of calcined and reduced samples. Figure 1: (**a**) XRD patterns and (**b**) N\({}_{2}\) adsorption/desorption isotherms and pore-width distribution of Ni-SmDC samples after calcination and after reduction treatment at 800 \({}^{\circ}\)C.  
hysteresis loop of H3 type. The hysteresis loops of both samples were in the relative pressure range of 0.51-0.98 and they were characterized by slit-shaped pores formed by aggregation of plate-like particles, suggesting the presence of dominant macropores and some mesopores. The pore size distributions were determined from BJH desorption isotherm. The pore size distribution of both calcined and reduced samples was broad because the result of BJH pore-size distribution could be attributed to the total contribution of both intra- and interparticle pores. The PDS curves of both samples show a pore-width distribution in the range 2.6-100 nm. The primary pore diameter was about 26.5 nm (mesoporous) for the calcined sample and in the range between 40 and 66 nm for the reduced sample.