# Influence of Synthesis Parameters in Obtaining KIT-6 Mesoporous Material
## 3 Results and Discussions
When evaluating the materials with 3D cubic structure, the values of specific area (S\({}_{\text{BET}}\)), mesoporous volume (V\({}_{\text{MESO}}\)) and total volume (V\({}_{\text{T}}\)) were lower (see Table 2) for both 18 h and 30 h when compared to the 24 h for the standard KIT-6. In this case, the aging time defines an optimal equilibrium point of 24 h to promote the hydrolysis of the silica source (TEOS), and later condensation of the inorganic phase interacting with the organic phase, generating exceptional textural properties for the 3D cubic structure. It can be observed that the variation in the time of the thermal treatment significantly influences the textural properties of the samples (KHT12, KHT18 and KHT30), and keeps the target for the 3D cubic structure. It denotes the proportional growth of values for the \(\mathrm{S}_{\mathrm{BET}}\), \(\mathrm{V}_{\mathrm{MESO}}\) and \(\mathrm{V}_{\mathrm{T}}\) parameters when the thermal treatment time increases (see Table 2). This behavior occurs because the longer the treatment time the greater the condensation rate of the silanol groups (Si-OH), directly influencing the formation of the inorganic structure. All the materials presented microporous volume varying between 0.01 and 0.03 cm\({}^{3}\).g\({}^{-1}\). In some specific cases, a small difference in the microporous volume is observed, such as in the case of the KHT12, KHT18 and KHT30 samples. However, the _\(\alpha\)-plot_ method does not allow a more in-depth analysis of these data, requiring more efficient methods, such as CO\({}_{2}\) adsorption at high pressures [42]. Table 4 shows the values of average pore diameter calculated with BJH, NLDFT and with VBS from the adsorption branch to compare the methods each other, and the values of pore diameter calculated from the desorption branch calculated by the VBS method. Figure 5 representatively shows the PSD of the standard KIT-6 and KDT2 samples. The PSD is very important to define the pore volumes for each pore size and, thus, to obtain the values of the average pore diameter of nanoporous materials. From the N\({}_{2}\) adsorption-desorption experimental isotherm data at 77 K, it was possible to apply microscopic (based on molecular theories) and macroscopic (based on capillary condensation) methods. According to some [24; 43; 44], the most used microscopic method is the NLDFT, and the macroscopic methods are BJH and VBS, these last two based on the Kelvin equation. In this work, the materials obtained with cylindrical pores show reversible isotherms with filling/emptying mechanism and hysteresis loops that are well defined. For this reason, the adsorption branch isotherm was selected to compare the methods with each other. From the evaluation of the PSD of representative samples (Figure 6) and the values of average pore diameter of all samples (Table 4), the NLDFT model overestimated the value of the pore size, while the values of the BJH and VBS methods were very close. This behavior suggests that the NLDFT model was not applied efficiently, once it takes another predetermined kernel to best fit the behavior of the samples. Among the macroscopic methods, the VBS method is the most accepted because this method was improved by