Ce-promoted Ni/Al2O3 catalyst for enhanced sustainable syngas production from CO2 reforming of crude glycerol

Abstract

Dry reforming of glycerol (GDR) presents an alternative approach to syngas production by converting glycerol, a byproduct of biodiesel, with CO₂. This study systematically investigated the effect of Cerium doping on Ni/Al₂O₃ catalyst synthesized via the wetness sonicated-assisted impregnation method. The effect of Ce promotion was studied at 0.5–3 wt%, conducted temperatures ranging from 650 to 750 °C and glycerol to CO₂ ratios from 1:0 to 1:4 in a fixed-bed reactor. The results show that Ce doping enhances catalyst basicity and modifies surface morphology by enlarging the CeO_x–nickel aluminate pore volume and reducing NiO crystallite size, thereby facilitating the formation of a synergistic NiO–NiAl₂O₄ active phase. Consequently, the improved adsorption of CO₂ molecules enhances glycerol conversion and significantly increases CO yield. The results show that the H₂/CO ratio in the syngas ranges from 0.8 to 1.2, with values below 2 being suitable for the Fischer-Tropsch reaction. Among the examined catalysts, the 1Ce10Ni/Al₂O₃ catalyst, benefiting from an improved glycerol conversion of ∼60 %, correlates with higher yields of H₂ (53 %) and CO (73 %), showing a notable 1.5 times improvement in glycerol conversion and 1.3–1.6 times greater yields of hydrogen and CO compared to the catalyst unpromoted catalyst, at reaction temperature of 700 °C. This finding underscores the substantial influence of CeOx doping on catalytic performance, highlighting the critical role of optimizing the H₂/CO ratio to achieve maximum glycerol conversion efficiency. Furthermore, the apparent glycerol activation energy decreases significantly from 60.21 kJ mol⁻¹ to 35.99 kJ mol⁻¹, demonstrating that Ce promotion contributes to the superior activity of 1Ce10Ni/Al₂O₃ compared to its unpromoted Ni/Al₂O₃. In general, the glycerol to CO₂ ratio (GCR) were the dominant parameters influencing reaction products, with the optimized GCR found to be 1:1.