## 4 Conclusions  
NRHMS-SO\({}_{3}\)H was successfully prepared via an in situ sol-gel method and acted as the potential solid acid catalyst for LA esterification with various alcohols. The incorporation of NR provided a hydrophobic surface, while the nanocomposite structure maintained the mesoporous framework and imparted surface functionality. The functional groups were uniformly distributed over the catalyst structure due to functionalization via the co-condensation approach. However, the high loading of MPTMS significantly diminished the physicochemical properties of materials. Among the three solid acid catalysts, NRHMS-SO\({}_{3}\)H (0.4) exhibited the highest catalytic activity in LA esterification with alcohols due to the synergistic effect of its physicochemical properties, acid site density, and hydrophobicity, effectively enhancing the reaction kinetics. Upon increasing the carbon chain length of the primary alcohols, catalytic activity decreased, whereas higher reaction temperatures considerably increased the ALE yield. The reaction can be described by the pseudo-first-order kinetic model. The activation energy of LA esterification with \(n\)-butanol of NRHMS-SO\({}_{3}\)H (0.4) was the lowest among all catalysts at 58.2 \(\pm\) 7.1 kJ/mol, which further enhanced its catalytic performance. The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/nano12040604/s1](https://www.mdpi.com/article/10.3390/nano12040604/s1)]([https://www.mdpi.com/article/10.3390/nano12040604/s1](https://www.mdpi.com/article/10.3390/nano12040604/s1)), Figure S1: Representative ATR-FTIR spectra of the synthesized materials. ; Figure S2. Wide scan XPS spectrum of HMS-SO\({}_{3}\)H(0.2). ; Figure S3. Core level high resolution (A) O1s and (B) S2p spectra of HMS-SO\({}_{3}\)H(0.2). ; Figure S4. Wide scan XPS spectrum of HMS-SO\({}_{3}\)H(0.4). ; Figure S5. Core level high resolution (A) O1s and (B) S2p spectra of HMS-SO\({}_{3}\)H(0.4). ; Figure S6. Wide scan XPS spectrum of HMS-SO\({}_{3}\)H(0.6). ; Figure S7. Core level high resolution (A) O1s and (B) S2p spectra of HMS-SO\({}_{3}\)H(0.6). ; Figure S8. Wide scan XPS spectrum of HMS-SO\({}_{3}\)H(0.4). ; Figure S8. Wide scan XPS spectrum of \begin{table}
\begin{tabular}{c c} \hline \hline
**Catalyst** & **E\({}_{\textbf{a}}\) (kJ/mol)** \\ \hline Blank & 71.3 \(\pm\) 5.0 \\ HUSY & 66.2 \(\pm\) 8.4 \\ HMS-SO\({}_{3}\)H (0.4) & 65.2 \(\pm\) 9.7 \\ NRHMS-SO\({}_{3}\)H (0.4) & 58.2 \(\pm\) 7.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Activation energy (E\({}_{\textbf{a}}\)) of LA esterification with \(n\)-butanol over different catalysts. Figure 12: Arrhenius plot of pseudo-first-order reaction of LA esterification with \(n\)-butanol over NRHMS-SO\({}_{3}\)H (0.4). NRHMS-SO\({}_{3}\)H(0.2). ; Figure S9. Core level high resolution (A) O1s and (B) S2p spectra of NRHMS-SO\({}_{3}\)H(0.2). ; Figure S10. Wide scan XPS spectrum of NRHMS-SO\({}_{3}\)H(0.4). ; Figure S11. Core level high resolution (A) O1s and (B) S2p spectra of NRHMS-SO\({}_{3}\)H(0.4). ; Figure S12. Wide scan XPS spectrum of NRHMS-SO\({}_{3}\)H(0.6). ; Figure S13. Core level high resolution (A) O1s and (B) S2p spectra of NRHMS-SO\({}_{3}\)H(0.6). ; Figure S14. Representative plot of pseudo-first order kinetic model of LA esterification with alcohols over a series of solid acid catalysts at different reaction temperature. (EtLA = ethyl levulinate, PrLA = _n_-propyl levulinate and BuLA = _n_-butyl levulinate). ; Table S1. XPS binding energies and atomic percent of chemical states for HMS-SO\({}_{3}\)H series and NRHMS-SO\({}_{3}\)H series. S.C. and C.N. conceptualized and designed the experiments; S.C. performed the materials synthesis, characterization, and catalytic activity evaluation; C.N. and N.Y. supervised and contributed chemical reagents/laboratory equipment and analysis tools; S.C. and C.N. analyzed the data and wrote the manuscript. All authors have read and agreed to the published version of the manuscript.