# Effects of Different Variables on the Formation of Mesopores in Y Zeolite by the Action of CTA+
## 3 Results
### Effect of the Presence of the Surfactant  
We evaluated the influence of the presence of the CTA\({}^{+}\) surfactant during modification of the USY zeolite on the generation of mesopores. As observed in Section 3.2, the presence of the surfactant during the alkaline treatment protected the zeolite structure from more intense action of the NaOH. The X-ray diffractograms of the YB0.04-S0.08-60/6h and YB0.04-S0-60/6h zeolites presented characteristic peaks of the faujasite structure (Figure 13). The zeolite modified without the presence of CTA\({}^{+}\) (YB0.04-S0-60/6h) showed a 77% reduction of relative crystallinity, whereas the RC of the zeolite modified with the addition of CTA\({}^{+}\) in the reaction mixture (YB0.04-S0.08-60/6h) decreased by only 6% (Table 5), confirming the protective effect of the surfactant. The modified USY zeolite produced using CTA\({}^{+}\) cations to compensate for the negative charges of the aluminum (denoted YB0.04-CTA\({}^{+}\)-60/6h) exhibited high relative crystallinity (Table 5, Figure 13). To verify the presence of the CTA\({}^{+}\) cations in this sample, thermogravimetric analysis (TGA) was performed (Figure S4). The presence of the cations could be explained by the presence of the cetyl (-C\({}_{16}\)H\({}_{33}\)) and methyl (-CH\({}_{3}\)) groups of the surfactant, whose occupation of space prevented the hydroxyl (OH\({}^{-}\)) groups from disrupting the Si-O-Si bonds protecting the micropores. This explanation \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample** & **RC(\%)** & **V\({}_{\text{total}}\)****1 (cm\({}^{3}\)/g)** & **V\({}_{\text{micro}}\)****2 (cm\({}^{3}\)/g)** & **V\({}_{\text{meso}}\)****3 (cm\({}^{3}\)/g)** & **S\({}_{\text{ext}}\)****2 (cm\({}^{3}\)/g)** \\ \hline USY & 100 & 0.395 & 0.239 & 0.156 & 208 \\ YB0.04-CTA\({}^{+}\)-60/6h & 98 & 0.405 & 0.245 & 0.160 & 179 \\ YB0.04-S0.08-60/6h & 94 & 0.426 & 0.240 & 0.186 & 233 \\ YB0.04-S0-60/6h & 23 & 0.355 & 0.084 & 0.271 & 334 \\ \hline \hline \end{tabular} \({}^{1}\) P/P\({}_{0}\) = 0.85; \({}^{2}\) t-plot; \({}^{3}\) NLDFT.  
\end{table} 
Table 5: Relative crystallinity and textural properties of the zeolites used to study the effect of the presence of the CTA\({}^{+}\) cations. Figure 13: X-ray diffractograms of the zeolites used to study the influence of the presence of CTA\({}^{+}\) cations. was supported by a previous study that reported that the use of tetramethylammonium hydroxide (TMAOH) [14] could protect the zeolite structure from hydroxyl attack, different from the use of the inorganic bases NH4 OH and NaOH. Analysis of the isotherms (Figure 14) revealed a smaller pore volume of the zeolite modified under mild conditions in the absence of the CTA\({}^{+}\) cation (YB0.04-S0-60/6h) compared to the zeolites modified in the presence of the surfactant. This occurred because the CTA\({}^{+}\) cations were not present to protect the zeolite structure, so the action of the base disrupted a greater quantity of Si-O-Si bonds. Analysis of the textural properties of the zeolites (Table 5) showed that the zeolite produced with CTA\({}^{+}\) cations compensating for the charges of the structure (YB0.04-CTA\({}^{+}\)-60/6h) did not form mesopores after the modification. This could be explained by the absence of micelle formation during the process, given that no surfactant was added to the reaction mixture. Analysis of the textural properties of the zeolite modified in the presence of the surfactant under milder hydrothermal treatment conditions (YB0.04-S0.08-60/6h) revealed that the milder alkaline solution and hydrothermal treatment conditions, when used together, were insufficient to form a significant quantity of mesopores. In this case, the micropore and mesopore volumes were virtually identical to those of the original USY zeolite (Table 5). In the absence of the surfactant, mesopores formed with a concomitant reduction in micropores (Table 5).