## 2 Results and Discussion
### Catalysts' Characterization
#### 2.1.2 Spectroscopy Studies (FTIR, UV-Vis, Raman, and \({}^{29}\)Si MAS-NMR)

Table 4: Textural properties for the calcined MCM-41 materials. Figure 11: Thermal analysis obtained under synthetic air for A-Si-MCM-41: TG and DTG curves (**A**); DTG and DSC curves (**B**). The temperatures indicated refers to the DTG maximums of observable peaks. Figure 12: Thermal analysis obtained under synthetic air for A-Ce-MCM-Cl: TG and DTG curves (**A**); DTG and DSC curves (**B**). The temperatures indicated refers to DTG maximums of observable peaks. For A-Si-MCM-41, five thermal events were observed and are consistent with previously reported events for similar as-synthesized MCM-41 materials [89]: (i) Evaporation of physically adsorbed water (endothermic, from room temperature to 129 \({}^{\circ}\)C); (ii) initial decomposition of occluded CTA\({}^{+}\) molecules through Hofmann elimination (endothermic, from 129 to 270 \({}^{\circ}\)C), generating triethylamine and alkenes; (iii) further fragmentation of carbon chains that resisted Hofmann elimination (exothermic; from 270 to 322 \({}^{\circ}\)C); (iv) oxidation of reminiscent organic residues from previous thermal events, like coke (exothermic; from 322 to 482 \({}^{\circ}\)C); and (v) condensation of silanol groups (with almost undetectable DTG and DSC maximums, from 482 to 1000 \({}^{\circ}\)C). The comparison between the modified as-synthesized materials and A-Si-MCM-41 showed differences in the DTG and DSC curves, even though the TG curves display similar profiles and CTA\({}^{+}\)/SiO\({}_{2}\) ratios. The different thermal behavior for both cerium incorporated materials, especially after the Hofmann elimination, revealed that: (i) In the temperature range associated to CTA\({}^{+}\) decomposition, one extra endothermic event occurs at 304 \({}^{\circ}\)C for A-Ce-MCM-Cl and 309 \({}^{\circ}\)C for A-Ce-MCM-NO\({}_{3}\); (ii) these extra events were overlapped with the first oxidation process, now shifted in the range of 315 to 360 \({}^{\circ}\)C; (iii) increase in the temperature of the DTG maximum for the final oxidation process, occurring around 70 \({}^{\circ}\)C higher than for A-Si-MCM-41; and (iv) increase in mass loss for the final oxidation processes, 5.59% for A-Si-MCM-41 and above 8.50% for both A-Ce-MCM-41 samples. Overall, this evidence demonstrates clearly that template molecules in the modified materials are thermally more resistant than in the as-synthesized Si-MCM-41. The extra thermal event might be due to an extra Hofmann elimination of molecules that survived the first decomposition process, delaying both exothermic events. Such phenomena can be either related to an increase of the interaction stability between CTA\({}^{+}\) and the inorganic framework or to diffusion limitations of products from thermal processes, since there was a decrease in \(V_{meso}\) after cerium incorporation. Similar observations have been made by [PERSON] [55] and [PERSON] and co-workers [90], especially as further evidence of isomorphic substitution of heteroelements in the inorganic framework. The TG curves of the calcined MCM-41 materials (Figure 14) and the mass loss associated to all processes (Table S3) are displayed in the Supplementary Material. These curves provided significant information to differentiate the materials among themselves, where a difference in total mass loss from room temperature to 1000 \({}^{\circ}\)C was observed in all solids. The two thermal events were associated to the evaporation of adsorbed water (endothermic event from room temperature to temperatures around 115 to 150 \({}^{\circ}\)C) and the condensation of silanol groups (water evaporation until 1000 \({}^{\circ}\)C). The major mass loss was associated to the initial evaporation of water: 4.58%, 14.23%, and 12.29% for Si-MCM-41, Ce-MCM-Cl, and Ce-MCM-NO\({}_{3}\), respectively. Also, this event ends in higher temperatures for the cerium-modified samples than for Si-MCM-41 (usually above 130 \({}^{\circ}\)C). Figure 13: Thermal analysis obtained under synthetic air for A-Ce-MCM-NO\({}_{3}\): TG and DTG curves (**A**); DTG and DSC curves (**B**).