Effect of the Y₂O₃ Promoter on the Structure of the Ni/Al₂O₃ Catalyst for Ethanol Autothermal Reforming

The Ni/Al₂O₃ catalyst is a viable alternative in catalytic reforming due to its excellent ethanol conversion and lower cost; however, it still suffers from deactivation by coke deposition. Doping the Ni/Al₂O₃ catalyst with yttrium oxide (Y₂O₃) neutralizes the acidic sites of the support, mitigating the reactions that lead to deactivation. In this work, Ni/Al₂O₃ catalysts with 1% and 2% Y₂O₃ were prepared by the wet impregnation method, dried at 90 °C for 24 h, and calcined at 975 °C for 5 h. The catalysts were characterized by N₂ physisorption (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), temperature-programmed reduction (TPR), and H₂ pulse chemisorption. The addition of the promoter reduced the temperature required for the reduction of nickel oxide (NiO) to Ni⁰ due to the lower formation of NiAl₂O₄ spinel. The Ni(10%)/Y₂O₃ (1%)Al₂O₃ (S3) catalyst achieved 100% ethanol conversion and superior selectivities for H₂ and CO₂ during 480 min at 600 °C, with an H₂O/C₂H₅OH/O₂ molar ratio of 3:1:0.5 and a space velocity of 1300 h^-1. Thermogravimetric analysis (TGA) indicated low coke formation (<1 mg_coke/mg_catalyst) for all catalysts and showed that the catalyst doped with 1% Y₂O₃ did not exhibit mass gain associated with the oxidation of Ni⁰ to NiO. Therefore, Y₂O₃ proved to be an effective promoter for increasing the activity and stability of Ni/Al₂O₃ catalysts in the autothermal reforming of ethanol.