Nickel supported on AlCeO₃ as a highly selective and stable catalyst for hydrogen production via the glycerol steam reforming reaction

In this study, a critical comparison between two low metal (Ni) loading catalysts is presented, namely Ni/Al₂O₃ and Ni/AlCeO₃ for the glycerol steam reforming (GSR) reaction. The surface and bulk properties of the catalysts were evaluated using a plethora of techniques, such as N2 adsorption/desorption, Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy / Energy Dispersive X-Ray Spectroscopy (SEM/EDX, Transmission Electron Microscopy (TEM), CO₂ and NH3-Temperature Programmed Desorption (TPD), and Temperature Programmed Reduction (H₂-TPR). Carbon deposited on the catalyst’s surfaces was probed using Temperature Programmed Oxidation (TPO), SEM, and TEM. It is demonstrated that Ce-modification of Al₂O₃ induces an increase of the surface basicity and Ni dispersion. These features lead to a higher conversion of glycerol to gaseous products (60% to 80%), particularly H₂ and CO₂, enhancement of WGS reaction, and a higher resistance to coke deposition. Allyl alcohol was found to be the main liquid product for the Ni/AlCeO₃ catalyst, the production of which ceases over 700 °C. It is also highly significant that the Ni/AlCeO₃ catalyst demonstrated stable values for H₂ yield (2.9-2.3) and selectivity (89-81%), in addition to CO₂ (75-67%) and CO (23-29%) selectivity during a (20 h) long time-on-stream study. Following the reaction, SEM/EDX and TEM analysis showed heavy coke deposition over the Ni/Al₂O₃ catalyst, whereas for the Ni/AlCeO₃ catalyst TPO studies showed the formation of more defective coke, the latter being more easily oxidized.