Browsing by Author "Ekeoma, MO"

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Glycerol Carbonate Synthesis Using a Catalyst Derived from Oldoinyo Lengai Volcanic Ash: Porosity, Process Optimization, Kinetic and Thermodynamic Analysis
(Wiley-VCH GmbH, 2025-11-08) Kandola, Isack; Tsere, Melkizedeck; Kichonge, Baraka; Jacob, Fortunatus; Bakari, Ramadhani; Pogrebnoi, Alexander; Mpumi, Nelson; Ekeoma, MO; Okoye, Patrick; Hilonga, Askwar; Kivevele, Thomas
This study investigates the use of natural catalysts from volcanic lava ash (VLA) to promote the conversion of glycerol (GL) to glycerol carbonate (GC). The surface basicity was characterized by temperature-programmed desorption of carbon dioxide (TPD-CO2), and textural properties by Brunauer–Emmett–Teller (BET). Kinetic modeling and thermodynamic calculations were performed to understand the reaction system. The VLA catalyst exhibited a surface area of 32.16 m2 g−1 with a total pore volume of 0.076 cm3 g−1 and an average pore diameter of 18.60 nm. Textural properties of volcanic ash lava revealed abundant active sites for adsorption and a mesoporous structure, which propagated diffusions of reactants, reactions at the active sites, and desorption of the products. High yield of glycerol carbonate and conversion of glycerol was attributed to high surface basicity of 32.40 mmol g−1 based on temperature-programmed desorption of carbon dioxide analysis. Process optimization based on response surface methodology using the Box-Behnken design revealed that 97.0 ± 0.1% of glycerol and 91.00 ± 0.15% of glycerol carbonate can be achieved at optimal conditions of 80 °C, 4.5 wt% catalyst loading, dimethyl carbonate to glycerol molar ratio of 3:1, under 90 min reaction time. The regression models exhibited R2 = 0.98 for glycerol conversion and R2 = 0.99 for glycerol carbonate yield. Kinetic studies revealed pseudo-first-order behavior with a rate constant of 0.1 min−1 at 348.15 K, and an activation energy of ∼33 kJ mol−1. Thermodynamic parameters (ΔG* = 92 kJ mol−1, ΔH* = 31 kJ mol−1, ΔS* = −174 J mol−1 K−1) suggest an endergonic and nonspontaneous reaction. The characterization results revealed that the catalyst possesses a basic and mesoporous structure. These properties played a crucial role in enhancing its catalytic efficiency and sustainable route for optimized glycerol carbonate synthesis with defined kinetics.
Glycerol Carbonate Synthesis Using a Catalyst Derived from Oldoinyo Lengai Volcanic Ash: Porosity, Process Optimization, Kinetic and Thermodynamic Analysis
(Wiley-VCH GmbH, 2025-11-08) Kandola, Isack; Tsere, Melkizedeck; Kichonge, Baraka; Jacob, Fortunatus; Bakari, Ramadhani; Pogrebnoi, Alexander; Mpumi, Nelson; Ekeoma, MO; Okoye, Patrick; Hilonga, Askwar; Kivevele, Thomas
This study investigates the use of natural catalysts from volcanic lava ash (VLA) to promote the conversion of glycerol (GL) to glycerol carbonate (GC). The surface basicity was characterized by temperature-programmed desorption of carbon dioxide (TPD-CO2), and textural properties by Brunauer–Emmett–Teller (BET). Kinetic modeling and thermodynamic calculations were performed to understand the reaction system. The VLA catalyst exhibited a surface area of 32.16 m2 g−1 with a total pore volume of 0.076 cm3 g−1 and an average pore diameter of 18.60 nm. Textural properties of volcanic ash lava revealed abundant active sites for adsorption and a mesoporous structure, which propagated diffusions of reactants, reactions at the active sites, and desorption of the products. High yield of glycerol carbonate and conversion of glycerol was attributed to high surface basicity of 32.40 mmol g−1 based on temperature-programmed desorption of carbon dioxide analysis. Process optimization based on response surface methodology using the Box-Behnken design revealed that 97.0 ± 0.1% of glycerol and 91.00 ± 0.15% of glycerol carbonate can be achieved at optimal conditions of 80 °C, 4.5 wt% catalyst loading, dimethyl carbonate to glycerol molar ratio of 3:1, under 90 min reaction time. The regression models exhibited R2 = 0.98 for glycerol conversion and R2 = 0.99 for glycerol carbonate yield. Kinetic studies revealed pseudo-first-order behavior with a rate constant of 0.1 min−1 at 348.15 K, and an activation energy of ∼33 kJ mol−1. Thermodynamic parameters (ΔG* = 92 kJ mol−1, ΔH* = 31 kJ mol−1, ΔS* = −174 J mol−1 K−1) suggest an endergonic and nonspontaneous reaction. The characterization results revealed that the catalyst possesses a basic and mesoporous structure. These properties played a crucial role in enhancing its catalytic efficiency and sustainable route for optimized glycerol carbonate synthesis with defined kinetics.