# An Experimental Study of Glycerol Carbonate Synthesis over g-C\({}_{3}\)N\({}_{4}\) Catalysts
## 1 Introduction  
In 2023, global carbon dioxide emissions related to energy rose by 1.1%, setting a new peak at 37.4 gigatons--moving further away from the decline needed to align withthe climate targets outlined in the Paris Agreement [1]. To mitigate these emissions, two primary technological approaches are employed: capturing CO\({}_{2}\) and either storing it or repurposing it. Forecasts indicate that by 2050, approximately 5.6 gigatons of CO\({}_{2}\) will need to be captured and securely stored each year [2]. Nevertheless, transforming CO\({}_{2}\) into useful chemical products presents a more cost-effective alternative compared to underground sequestration [3]. A key strategy in emission reduction involves the adoption of renewable sources, such as biodiesel derived from biomass. This option is gaining traction due to its favorable properties--including being non-toxic, renewable, and free of sulfur and aromatic compounds [4]. As a byproduct of biodiesel production, glycerol has become increasingly surplus due to the expansion of biodiesel applications. Given the need for sustainable development, converting glycerol into high-value chemicals has become a challenge for researchers [5; 6]. Glycerol is highly valued for its extensive use across various industrial sectors, including pharmaceuticals, personal care products, the food industry, and cosmetics [7]. Additionally, it shows significant potential as a primary chemical reactant in synthesizing various organic molecules. Glycerol can serve as a renewable feedstock in numerous chemical processes, such as carbonation, carbonylation, transesterification, and oxidation. Among these transformations, the synthesis of glycerol carbonate is particularly compelling from an environmental perspective as it utilizes CO\({}_{2}\) as both a carbon source and a C1 feedstock. This approach is pivotal in advancing decarbonization efforts and accelerating progress toward achieving net-zero emission targets [2; 8]. Glycerol carbonate is emerging as a promising platform chemical and an eco-friendly alternative to traditional petrochemical-based substances. Its applications are diverse, serving as a solvent in detergents and paints, and playing a crucial role in producing valuable intermediates like glycidol which are used in textiles, plastics, pharmaceuticals, and cosmetics [9]. Additionally, glycerol carbonate is utilized in lithium-ion battery electrolytes, surfactants, and as a general-purpose solvent [10]. Among the various synthesis routes, the direct reaction between glycerol and CO\({}_{2}\) is the most environmentally favorable as it exclusively produces the target compound without unwanted byproducts. However, this method has not yet been implemented on an industrial scale due to challenges such as low conversion efficiency, limited catalyst stability, and thermodynamic constraints of the reaction. These issues may be mitigated by optimizing reaction pathways and using water-removing agents to shift the equilibrium towards product formation [3; 11; 12]. To enhance the synthesis of glycerol carbonate, a variety of heterogeneous catalytic systems have employed dehydating agents such as acetonitrile, benzonitrile, 2-cyanopyridine, adiponectinrile, dimethylformamide (DMF), calcium oxide (CaO), and magnesium carbonate (MgCO\({}_{3}\)) [13; 14; 15; 16; 17; 18]. These systems include titanosilicate-based ETS-10 zeolite catalysts, which are modified by impregnating active metals such as Co, Zn, Cu, Ni, Zr, Ce, and Fe [19]. Cerium oxide (CeO\({}_{2}\)) catalysts have also been synthesized through precipitation, hydrothermal techniques, and citrate sol-gel methods [3; 15]. In another approach, finely distributed MgInCe mixed metal oxides (MgInCe-MMOs) were synthesized via a topological transformation from their layered double hydroxide precursors (MgInCe-LDHs) [20]. Hydrothermal synthesis was also used to fabricate a range of Cu\({}_{1-x}\)Zr\({}_{x}\)O\({}_{2}\) bimetallic oxides with varying Cu-to-Zr ratios [21].