The role of Ga and Y on binary Al2O3-Y2O3 and Al2O3-Ga2O3 mixed oxides nanoparticles towards potential Ni water-gas shift catalysts

Abstract

This work focuses on the study of binary Al₂O₃-Y₂O₃-x and Al₂O₃-Ga₂O₃-x mixed oxides with varying Y₂O₃ or Ga₂O₃ nominal loading (x=25, 50) prepared by hydrothermal synthesis assisted by Triton X-100. The mixed oxides were used to prepare Ni-based (5 wt%) catalysts for the Water Gas Shift Reaction. The Al₂O₃ sample presented urchin-like hollow nanosphere morphology, which evolved to solid nanospheres with Y₂O₃ or Ga₂O₃ in the mixed oxides. The physicochemical characterization indicated good integration of the mixed oxides, especially on the low-content additive oxides. The theoretical results confirmed that Ga goes deeper into the alumina matrix than Y, partially explaining the XPS and HRTEM results in which the Ni dispersion was better in the Ni/AlGa-x samples. The FTIR in-situ measurements of the reaction allowed us to propose that the reaction occurs minimally through the carbonyl mechanism at low temperatures (<300 °C) and the formate mechanism at high temperatures (>300 °C).