# Effects of Different Variables on the Formation of Mesopores in Y Zeolite by the Action of CTA+
## 3 Results  
### Influence of Surfactant Concentration  
The X-ray diffractograms of the modified zeolites and the original USY zeolite (Figure 1) revealed that only the zeolite modified without the addition of a surfactant (YB0.08-S0) did not show diffraction peaks corresponding to the FAU structure. Calculation of the relative crystallinity (RC) of the modified zeolites (Table 2) revealed an average reduction in RC of approximately 65% under the conditions tested. Notably, the use of CTA\({}^{+}\) in the alkaline treatment protected the Si-O-Si bonds from attack by hydroxyl groups (OH\({}^{-}\)), thus preventing the complete destruction of the zeolite structure. In a study on the desilocalization of zeolite Y with different Si/Al ratios used in this study, the same behavior in the presence of CTAB was verified [14]. Figure 1: X-ray diffractograms of the samples modified using different concentrations of cetyltrimethylammonium bromide (CTAB). The X-ray diffractograms showed the presence of a halo around 15-30\({}^{\circ}\) 20 (the magnification in Figure 1), possibly due to silicon atoms removed from the structure and deposited in the form of amorphous silica organized by the CTA\({}^{+}\) micelles. For a better visualization of the amorphous halo in the X-ray diffraction (XRD) pattern of sample YB0.08-S0, the graph was plotted on a smaller scale. (Figure S1). At small angles, the X-ray diffractograms of the modified zeolites showed a peak near of 2\({}^{\circ}\) 20, corresponding to the repetition of crystallographic planes, possibly resulting from the ordering of pores larger than 2 nm, derived from the treatments of the materials (Figure 2). Comparison of the modified zeolites with low (y = 0.02) and high (y = 0.1) surfactant contents showed that the relative crystallinity did not change significantly. In other words, the surfactant content did not considerably influence this parameter. The initial USY zeolite presented a type I isotherm (Figure 3) according to the IUPAC [16] classification, reflecting a predominance of micropores in its structure. However, the modified materials showed isotherms that were a combination of types I and IV (Figure 3), indicative of the presence of micro- and mesopores in their structures and confirming the effectiveness of the modifications. The porous structure of the YB0.08-S0 zeolite was completely destroyed due to the absence of CTA \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample** & **RC (\%)** & **Vtotal 1 (cm\({}^{3}\)/g)** & **Vmicro 2 (cm\({}^{3}\)/g)** & **Vmeso 3 (cm\({}^{3}\)/g)** & **S\({}_{\text{ext}}\) 2 (cm\({}^{3}\)/g)** \\ \hline USY & 100 & 0.395 & 0.239 & 0.115 & 208 \\ YB0.08-S0 & 0 & 0.023 & 0.002 & 0.033 & 20 \\ YB0.08-S0.02 & 32 & 0.225 & 0.087 & 0.123 & 165 \\ YB0.08-S0.04 & 39 & 0.395 & 0.107 & 0.193 & 364 \\ YB0.08-S0.06 & 38 & 0.468 & 0.091 & 0.265 & 536 \\ YB0.08-S0.08 & 38 & 0.603 & 0.092 & 0.363 & 597 \\ YB0.08-S0.1 & 33 & 0.649 & 0.077 & 0.404 & 661 \\ \hline \hline \end{tabular}  
* P/P\({}_{0}\) = 0.85; 2 External surface area by t-plot; 3 determined by NLDFT. The pH of the reaction mixture after the USY treatment was about 11.0.  
\end{table} 
Table 2: Relative crystallinity (RC) and textural properties of the modified zeolites, according to the amount of surfactant used during the modification. Figure 2: X-ray diffractograms at small angles of the modified zeolites produced using different concentrations of surfactant (CTA\({}^{+}\)). during the modification, in agreement with the destruction of the faujasite structure shown by the X-ray diffraction analysis (Figure 1). The larger mesopore volume of the modified samples produced using higher surfactant ratios (Table 2) were probably due to the formation of a higher number of micelles, since these are templates for the formation of mesopores. The external area, determined by the t-plot method, increased with increasing mesopore volume. Figure 4 shows the volumes of micropores and mesopores as a function of the surfactant ratio used in modification of the original USY zeolite.