Investigating the Catalytic Effects of Ni and Fe Doping on CaO for Enhancing the Glycerol Valorization into Lactic...

This study presents the synthesis of a waste-derived catalyst for the efficient glycerol valorization into value-added products, contributing to waste valorization, resource recovery, circular economy, and sustainable chemical production. The valorization of glycerol into lactic acid has been investigated using Fe- and Ni-doped calcium oxide (CaO) catalyst synthesized from marble waste through thermal decomposition. The catalysts were calcined at 500 °C and thoroughly characterized using Brunauer-Emmett-Teller (BET) surface area analysis, X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR). The optimized catalyst, designated as NiO·Fe₂O₃/CaO, achieved a lactic acid yield of 20.7 mol % under reaction conditions of 10 g of catalyst, a temperature of 260 °C, and a reaction time of 150 min. A glycerol conversion of 68.5% was recorded. Secondary products formed during the reaction included 1,3-propanediol, formic acid, and acetic acid, with their maximum yields being 8.45 mol %, 2.20 mol %, and 1.79 mol %, respectively, observed at 260 °C after 180 min. The lactic acid yield was found to be dependent on both temperature and reaction time, reaching a maximum at 260 °C and 150 min, after which it declined due to thermal degradation into lighter gases and oxygenated byproducts. These results highlight the potential of utilizing marble waste-derived catalysts for the sustainable and value-added transformation of glycerol.