Hierarchically structured tetragonal zirconia as a promising support for robust Ni based catalysts for dry reforming of methane

Abstract

In this study, nanosheets-accumulating Laminaria japonica-like hierarchically structured tetragonal phase dominant zirconia (t-ZrO₂-lj) with high thermal stability was successfully synthesized for the first time by a facile hexamethylenetetramine–glucose assisted hydrothermal approach. The supported Ni catalyst on t-ZrO₂-lj with tetragonal phase dominant crystalline structure displays much superior activity and stability for synthesis gas production through dry reforming of methane with CO₂ in comparison with a Ni catalyst supported on monoclinic zirconia nanoparticulate (m-ZrO₂-np) prepared by a common hydrothermal method. By employing diverse characterization techniques, including X-ray diffraction (XRD), N₂ adsorption (BET), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), H₂ temperature-programmed reduction (H₂-TPR), CO chemisorption, CO₂ temperature-programmed desorption (CO₂-TPD), and thermogravimetric analysis (TGA), the natures of the as-synthesized ZrO₂ and the supported Ni catalyst on t-ZrO₂-lj were unambiguously characterized. Correlating the nature of the catalyst to the reaction results, the higher activity of Ni/t-ZrO₂-lj catalyst compared to Ni/m-ZrO₂-np can be ascribed to higher Ni dispersion and better reducibility due to the unique morphology and microstructure of the zirconia support. More interestingly, the developed Ni/t-ZrO₂-lj catalyst demonstrates higher coke resistance during the dry reforming process in comparison with Ni/m-ZrO₂-np, resulting from the higher basicity of tetragonal phase ZrO₂ compared to monoclinic ZrO₂, which endows the developed Ni/t-ZrO₂-lj catalyst with greatly superior stability to Ni/m-ZrO₂-np for dry reforming of methane. This study provides a new avenue for fabricating robust coke-resistent Ni-based catalysts for synthesis gas production. Moreover, the as-synthesized t-ZrO₂-lj with high thermal stability has great potential for applications as an excellent support in diverse transformations, especially for high temperature reactions.