# Effects of Different Variables on the Formation of Mesopores in Y Zeolite by the Action of CTA+
## 3 Results
### Influence of Base Concentration  
The X-ray diffractograms of the modified USY zeolites presented diffraction peaks characteristic of the faujasite structure, but with lower intensity compared to the diffractogram of the original USY zeolite (Figure 6). The X-ray diffractograms of the modified zeolites produced using higher amounts of base (x = 0.04-0.08) with a more pronounced halo at 26 of 15-30\({}^{\circ}\), possibly related to amorphous silica, different from the X-ray diffractograms of the modified zeolites produced with lower base content. Figure 5: Pore diameter distributions (Barret-Joiner-Halenda method; BjH) of the modified zeolites produced using different CTAB concentrations. Figure 6: X-ray diffractograms of the modified zeolites produced using different base ratios. The relative crystallinity of the zeolites decreased as the concentration of the alkaline medium increased (Table 3). This demonstrated the importance of adjusting the concentration of the alkali solution in order to avoid excessive amorphization of the material and conserve the properties of the zeolite. The X-ray diffractograms at small angles of the modified zeolites produced using different base concentrations are shown in Figure 7. The YB0-S0.1, YB0.02-S0.1, and original USY zeolites did not present a diffraction peak at 2\({}^{\circ}\) 2\(\theta\), corresponding to the repetition of the crystallographic planes, probably due to the absence of mesoporosity with a certain degree of organization. The nitrogen adsorption isotherms (Figure 8) revealed the lower nitrogen adsorption by the YB0.02-S0.1 zeolite at a relative pressure of 0.4, indicative of the generation of fewer mesopores due to the milder alkaline treatment. The modified zeolites produced using higher base concentrations presented greater mesopore formation. \begin{table}
\begin{tabular}{c 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)** & **Sext 2 (cm\({}^{3}\)/g)** & **pH 4** \\ \hline USY & 100 & 0.395 & 0.239 & 0.115 & 208 & - \\ YB0-S0.1 & 96 & 0.396 & 0.242 & 0.142 & 186 & 3 \\ YB0.02-S0.1 & 80 & 0.367 & 0.199 & 0.170 & 209 & 9 \\ YB0.04-S0.1 & 52 & 0.464 & 0.129 & 0.229 & 420 & 10 \\ YB0.06-S0.1 & 38 & 0.627 & 0.095 & 0.379 & 591 & 11 \\ YB0.08-S0.1 & 33 & 0.649 & 0.077 & 0.404 & 661 & 11 \\ \hline \hline \end{tabular} \({}^{1}\) P/P\({}_{0}\) = 0.85; 2 t-plot; 3 NLDFT; 4 pH of the reaction mixture after the USY treatment.  
\end{table} 
Table 3: Relative crystallinity and textural properties of the modified zeolites, according to the base concentration used. Figure 7: X-ray diffractograms at small angles of the modified zeolites produced using different base concentrations. From the data presented in Table 3 and Figure 8, no mesoporous was created when the modification was performed in the absence of a base. This indicated that the formation of SiO\({}^{-}\) species by breaking the Si-O-Si bonds due to the action of a base was fundamental for the formation of mesopores. A positive correlation was found between the NaOH concentration used in the treatment and the mesopore volume of the resulting material. In addition, an increase in the volume of mesopores was accompanied by a decrease in the micropore volume (Table 3, Figure 9), as also found elsewhere [10]. The modified zeolites demonstrated a narrow pore size distribution centered near 3 nm (Figure 10). As the alkaline treatment concentration increased, the volume of the mesopores generated also  
Figure 8: Nitrogen adsorption isotherms of the modified samples produced using different concentrations of the alkaline medium. Figure 9: Zeolite mesopore and micropore volumes as a function of the base ratio (x) used for the modification. A and B represent the volume of micropores and mesopores in the original USY zeolite, respectively. increased. The mildest alkaline treatment (x = 0.02) was insufficient to create any substantial quantity of mesopores templated by the CTA\({}^{+}\) micelles.