## 3 Results and Discussion  
### Characterization  
The XRD patterns of the zeolites used as support and the final catalysts after calcination are presented in Figure 1. These diffractograms confirm that the original structure of both zeolite types, ITQ-2 and ZSM-5, is preserved after Ni incorporation and calcination. For the sample supported on the ITQ-2 without Al, the absence of diffraction peaks of NiO indicates that Ni is well-dispersed in this sample with a small crystallite size (Figure 1a). The absence of diffraction peaks related to NiO for this catalyst indicates that the size of this phase might be probably under 3 nm, as the determination of crystallite sizes by XRD is reported to be applied more accurately in the range between 3 and 100 nm [29]. For the ITQ-2 zeolite with a Si/Al ratio of 15, the peaks corresponding to the NiO phase can be observed. The calculation of the crystallite size for NiO by Scherrer equation gives a result of 10.6 nm. In the case of ZSM-5 samples, NiO diffraction peaks are detected for both samples independently of the Si/Al ratio (Figure 1b). Crystallite sizes of 12.0 and 16.5 nm are obtained for 5 Ni/ZSM-5(15) and 5 Ni/ZSM-5(140), respectively. Therefore, the use of the delaminated zeolite ITQ-2 with a high Si/Al ratio seems to favor the formation of smaller NiO crystallite size. Textural properties and chemical composition are summarized in Table 1. First of all, comparing ITQ-2 and ZSM-5 samples, the higher values of external surface area for the former group clearly stand out. Secondly, concerning the effects of Ni incorporation, a decrease of S\({}_{\text{BET}}\) was observed for all the samples. This fact is explained mainly by the dilution effect that takes place with Ni incorporation to the zeolite [30,31]. The variations of both external and micropore surface area were calculated to identify additional reasons. As the obtained values are higher than the expected values taking into account just the dilution effect, other reasons for the decrease of S\({}_{\text{BET}}\), such as the blockage of micropores, might also exist. Examining more carefully these calculated percentages, it can also be observed that for ZSM-5 samples, the variation of external and micropore surface areas follow opposite trends with Si/Al ratio. When the Si/Al ratio is increased, the variation of micropore surface area decreased up to the expected \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample** & **Si/Al Ratio 1** & \begin{tabular}{c} **Ni Content 1** \\ **(wt.\%)** \\ \end{tabular} & \begin{tabular}{c} **S\({}_{\text{BET}}\)** \\ **(m\({}^{2}\)/g)** \\ \end{tabular} & \
\begin{tabular}{c} **S\({}_{\text{external}}\)** \\ **(m\({}^{2}\)/g)** \\ \end{tabular} &
\begin{tabular}{c} **S\({}_{\text{micropore}}\)** \\ **(m\({}^{2}\)/g)** \\ \end{tabular} \\ \hline ITQ-2(\(\infty\)) & & & 712 & 528 & 185 \\
5 Ni/ITQ-2(\(\infty\)) & & 5.2 & 579 & 458 (\(-\)13\%) & 120 (\(-\)35\%) \\ ITQ-2(15) & 10 & & 610 & 284 & 325 \\
5 Ni/ITQ-2(15) & 10 & 5.7 & 520 & 213 (\(-\)25\%) & 307 (\(-\)6\%) \\ ZSM-5(140) & 117 & & 394 & 43 & 351 \\
5 Ni/ZSM-5(140) & 117 & 5.7 & 368 & 37 (\(-\)14\%) & 331 (\(-\)6\%) \\ ZSM-5(15) & 14 & & 429 & 40 & 389 \\
5 Ni/ZSM-5(15) & 15 & 5.3 & 373 & 40 (0\%) & 333 (\(-\)14\%) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Textural properties and chemical composition of the supports and the corresponding 5 wt.% Ni catalysts supported on ITQ-2 and ZSM-5 with different Si/Al ratios. Figure 1: X-ray diffraction (XRD) patterns of the supports and the corresponding 5 wt.% Ni catalysts supported on (**a**) ITQ-2; (**b**) ZSM-5 with different Si/Al ratios. value considering the dilution effect. However, the percentage of variation of external surface area increased suggesting that Ni nanoparticles are deposited in the external surface of this material. Metal can migrate during calcination to more internal positions providing greater stabilization.