## 3 Results and Discussion
Two different regions were observed in the \({}^{29}\)Si MAS NMR spectra of the calcined samples, which were synthesized with aluminum (Figure 4a, Table 3). This includes the chemical environment, at approximately 105 ppm to 120 ppm, in which all Si atoms, surrounded by O atoms, were bonded to four additional Si atoms. Additionally, the second \begin{table}
\begin{tabular}{c c} \hline \hline
**Sample** & **Average Relative Crystallinity Index** \\ \hline SiAl15 & 0.62 \\ SiAl25 & 0.97 \\ SiAl35 & 1.00 \\ Pure\_Silica & 0.34 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Relative crystallinity index. Figure 3: Magnified view of the X-ray diffractograms of the calcined samples. region centered at approximately 102 ppm which corresponds to the Si[OSi]\({}_{3}\)[OAl] species, that is, with one Al atom replacing one of the Si atoms in the second coordination sphere [4; 12]. The bands of the first region were assigned to Si [OSi]\({}_{4}\) outside of the D4R cages (at approximately \(-115.5\) ppm) and to Si [OSi]\({}_{4}\) in the D4R cages (at approximately 109 ppm) [19]. Comparing these chemical shifts with those reported for pure silica (published in [4; 19]), a slight displacement, which is typical of the heteroatom introduction in a pure silica zeolite, was observed. In addition, the Si[OSi]\({}_{3}\)[OAl] species in the pure silica sample, confirming the introduction of aluminum in the framework, was not identified. This absence was reported previously for the pure silica form synthesized that employed HF and is explained as being due to the lack of connectivity defects after calcination [19; 20]. The sample with the highest Si/Al\({}_{\text{TETRA}}\) ratio corresponded to the sample synthesized with the highest (Si/Al)\({}_{\text{CEL}}\) ratio. The \({}^{27}\)Al MAS NMR spectra (Figure 4b, Table 3) of the calcined samples also confirmed the existence of the aluminum framework, corresponding to the tetrahedral aluminum represented by the band at approximately 60 ppm. A band at approximately 7 ppm, related to octahedral aluminum, also appeared, with a variation in the intensity among the samples. These results showed that a higher aluminum concentration in the synthesis gel led to a lower content of bulk octahedral aluminum. The three [Al] HPM-1 samples were also studied by X-ray photoelectron spectroscopy (XPS) because this technique provides fundamental information regarding the surface chemistry for catalytic reactions [21]. This technique had never previously been reported to study the aluminum distribution in HPM-1, as far as we know. Several interesting differences were found among the samples. Figure 5 presents the Al \(2p\) signals from each sample, showing differences in the binding energy (BE, eV) values among the samples. These variations were in the range of the beta zeolite (differences of about \(\pm 0.5\) eV in BE), a topology that also presents a chiral polymorph [22]. The different (Si/Al\({}_{\text{TETRA}}\))\({}_{\text{SURFACE}}\) ratios were calculated from these spectra and the Si \(2p\) spectrum (Table 3). The results followed the same tendency as the \({}^{29}\)Si MAS NMR spectra, and showed that the surface was r  
Figure 4: \({}^{29}\)Si (**a**) and \({}^{27}\)Al (**b**) MAS NMR (Magic-angle spinning solid-state nuclear magnetic spectroscopy) spectra of the calcined samples. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{2}{c}{**Si/Al\({}_{\text{TETRA}}\)**} & \multicolumn{2}{c}{**Al\({}_{\text{TETRA}}\)/Al\({}_{\text{OCTA}}\)**} \\ \cline{2-5}  & **MAS NMR** & **XPS** & **MAS NMR** & **XPS*** \\ \hline SiAl15 & 185.0 & 7.7 & 1.6 & 0.6 \\ SiAl25 & 192.6 & 11.1 & 1.3 & 1.1 \\ SiAl35 & 192.3 & 11.9 & 0.9 & 1.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: \({}^{29}\)Si MAS NMR (Magic-angle spinning solid-state nuclear magnetic spectroscopy) chemical shifts of the calcined samples SiAl15, SiAl25, and SiAl35. resulting in a higher amount of Al incorporated in the external layer of the zeolite.