## 3 Results and Discussion
This measurement could also be taking the octahedral aluminum into account. Therefore, the (Al\({}_{\text{TETRA}}\)/Al\({}_{\text{OCTA}}\))\({}_{\text{SURTACE}}\) ratio was calculated, and the modified Auger parameter of Al (\(\alpha^{\prime}\)) [23], from the different samples, was obtained according to Equation (5):  
\[\alpha^{\prime}=1253.6+\text{KE}(\text{Al}_{\text{KLL}})-\text{KE}(\text{Al}\,2p) \tag{5}\]  
where \(\text{KE}(\text{Al}_{\text{KLL}})\) is the kinetic energy of the Auger electron at \(\text{Al}_{\text{KLL}}\) (Figure 6), and \(\text{KE}(\text{Al}\,2p)\) is the kinetic energy of the Al \(2p\) photoelectron. A comparison of these results with the results of \({}^{27}\)Al MAS NMR shows that, for SiAl25 and SiAl35, it is similarly indicated that the tetrahedral aluminum would be easily accessible as acidic sites. In the case of SiAl15, the octahedral aluminum content may interfere with the accessibility of the tetrahedral aluminum in future reactions. Despite the increasing ratio from SiAl15 to SiAl35, the results were as expected. The octahedral aluminum was outside of the framework; it was placed on the surface. The data obtained from the XPS analysis are summarized in Tables 3 and 4. The resulting morphology is similar to a rice grain, which has the same reported morphology for the pure silica HPM-1 [4]. Finally, to determine the acidic or basic character of the zeolite, the ethanol dehydration model reaction was used [12]. Figure 8 and Table 5 show the catalytic performance of the [Al] HPM-1 samples. Comparing all the samples, a greater ethanol conversion value was observed for the SiAl25 sample, and lower conversions were observed for the SiAl15 and SiAl35 samples. This order of conversion performance was explained by several factors. The first factor is the BET (Brunauer-Emmett-Teller) area (SBET, Table 5, Supplementary Material Figures S3-S5, and Tables S1-S3), which is directly related to the highest conversion values, because the highest SBET allows a higher quantity of accessible acidic sites [12]. Therefore, SiAl25 and SiAl35 were expected to show higher conversion values than SiAl15. The second factor influencing the ethanol conversion was the amount of octahedral aluminum. While SiAl15 had the highest Si/Al\({}_{\text{TETRA}}\) ratio, its (Al\({}_{\text{TETRA}}\)/Al\({}_{\text{OCTA}}\))\({}_{\text{XPS}}\) ratio was low, implying that the total pore volume (TPV, Table 5, Supplementary Material Tables S1-S3) was lower than in the other cases, thus preventing interaction between the ethanol and the active sites and making the diffusion of the molecules in the pores more difficult. The difference in the conversion performance between SiAl25 and SiAl35 was due to the bulk tetrahedral aluminum content, which was greater for SiAl25 than for SiAl35. Finally, even though SiAl35 has double the area of SiAl15, they presented a similar conversion value, probably because the higher area value was in consideration of the area of the octahedral aluminum, and did not interfere with the reaction. The Pure_Silica sample was also tested for the dehydration of ethanol and showed a very low activity (approximately 2-12%), which is practically inactive, owing to the minimal amount of Si-OH sites reported in a fluoride medium [4; 12; 19; 20]. It is well known that the product selectivity in ethanol conversion is directly related to the acid strength of the material [24]. For the study of sample selectivity at 250 \({}^{\circ}\)C, ethanol was catalytically converted via the intramolecular and intermolecular dehydration reactions [25] to produce ethylene and diethylether (DEE), respectively (Table 5, Figure 8)--products that are only formed at acidic sites. This result demonstrated the high acidic character of the samples; the SiAl25 sample was the most acidic sample. Comparing the three cases, at a high temperature and conversion, DEE is produced with high selectivity, as expected, due to the exothermic nature of the reaction [14; 15].