# An Experimental Study of Glycerol Carbonate Synthesis over g-C\({}_{3}\)N\({}_{4}\) Catalysts
## 4 Conclusions  
This work introduces a new catalytic system with potential for scalable, environmentally friendly synthesis of glycerol carbonate and provides both experimental data and statistical modeling to support its performance. In this respect, four graphitic-carbon-nitride (g-C\({}_{3}\)N\({}_{4}\)) catalysts co-doped with phosphorus (P), sulfur (S), magnesium (Mg), and lithium (Li) were synthesized using a one-step thermal condensation method. The catalysts were characterized using XRD, SEM, TGA, FTIR, and nitrogen adsorption-desorption  
Figure 12: SEM images of the MgPSCN catalyst after two reaction cycles at optimum parameters.  
Figure 13: EDX spectra of the MgPSCN catalyst after two reaction cycles at optimum parameters.  
techniques and were employed for the synthesis of glycerol carbonate through the coupling reaction of glycerol and CO\({}_{2}\). Co-doping did not significantly modify the average crystallite size, except for lithium doping which favored the shrinkage of crystallites. The BET surface area of the pores was also maintained at similar values, except for Li doping which almost doubled it. Thermogravimetric analysis revealed that doping with sulfur and phosphorus led to increased weight loss, which can be elucidated by the lesser value of the homolytic dissociation energy of the P-O-C bond compared to that of the C-C bond. The incorporation of phosphorus and sulfur additives to the PSCN, MgPSCN, and LiPSCN catalysts led to a reduction in the intensity of the C-N and N-H vibrational peaks, as revealed by FTIR analysis. SEM analysis revealed that doping with magnesium, phosphorus, and sulfur favored the formation of numerous clusters with variable sizes at the nanometric scale, with diameters smaller than those in PSCN, while doping with lithium favored the uniformization of the structure compared to PSCN. The parameters of the glycerol carbonate synthesis process were optimized using the response surface methodology based on a Box-Behnken design, with reaction temperature, catalyst amount, and operating pressure as independent variables. All catalysts considered in this study were tested under these conditions, with the experimental data obtained highlighting the increase in conversion and yield in glycerol carbonate for the doped catalysts. Thus, highest values for glycerol conversion of 70.05% and GC yield of 45.85% were obtained on the MgPSCN catalyst using the optimal factors values.  
Conceptualization, D.M.C.; Data curation, I.B., C.P. and R.D.; Formal analysis, G.V., I.L.L.M., M.B. and I.V.G.; Investigation, M.L.C., I.L.L.M., G.V., M.B., C.D.-V. and R.D.; Methodology, M.L.C., D.B. and C.P.; Project administration, D.M.C.; Resources, D.B and I.L.L.M.; Software, I.B. and R.D.; Supervision, D.M.C.; Validation, G.V. and D.B.; Visualization, D.M.C.; Writing--original draft, M.L.C., I.B., D.B., C.D.-V. and R.D. All authors have read and agreed to the published version of the manuscript.  
This work was carried out through the PN 23.06 Core Program--ChemNewDeal within the National Plan for Research, Development, and Innovation 2022-2027, developed with the support of the Ministry of Research, Innovation, and Digitization, project no. PN 23.06.02.01 (InteGrad).  
Not applicable.  
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
Author [PERSON] was employed by the company Botanical SRL. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.