A comparative study of dry reforming of methane over nickel catalysts supported on perovskite-type LaAlO3 and commercial α-Al2O3

Abstract

A systematic and comparative study was made to determine the influence of perovskite-type LaAlO3 and commercial α-Al2O3 on the performance of nickel-based catalysts in dry reforming of methane (DRM). The perovskite-type LaAlO3 was selected due to its characteristics of solid state semiconductor with oxygen vacancies and high structural stability. The catalysts were characterized by X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), N2 adsorption-desorption, temperature programmed reduction (TPR-H2), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The catalyst performance was evaluated based on activity tests (600–800 °C) and short- and long-term stability (10 and 20 h) at 700 °C at a GHSV (Gas Hourly Space Velocity) of 18 and 72 L g−1 h−1. The TPR-H2 profiles indicate that the oxygen vacancies on the perovskite surface exerted a strong effect on the reduction temperature and reducibility of the NiO nanoparticles, resulting in weak Ni0/support interaction. The results of the tests after 10 h under GHSV of 18 L g−1 h−1 indicate that the Ni/LaAlO3 catalyst is 7.8 and 11.5% more stable than Ni/α-Al2O3 in the conversions of CH4 and CO2, respectively. The higher stability and activity of Ni/LaAlO3 is directly ascribed to the presence of NiO (3.38 wt%) after activation, which promoted the formation of carbon nanotubes (CNT) and increased the dispersion of the metallic phase. Even under severe conditions of activation and reaction (high GHSV), as in the long-term test, the Ni/LaAlO3 catalyst showed a 37.2% higher H2 yield than the Ni/α-Al2O3. Analyses by TEM indicate that the Ni/α-Al2O3 catalyst exhibited deactivation problems associated with sintering effects. Thus, the presence of structural defects and surfaces rich in oxygen vacancies makes LaAlO3 perovskite a potential support for application in methane catalytic reforming processes.