Ni-W Catalysts Supported on Mesoporous SBA-15: Trace W Steering CO2 Methanation

Aseries of Ni-W catalysts supported on mesoporous SBA-15 with different Ni:W ratios(Ni_xW/SBA-15, Ni-5%, x=1,10,50) was prepared and fully characterized by powder X-ray diffraction(PXRD), Brunner-Emmet-Teller(BET), transmission electronic microscopy(TEM), H₂-temperature programmed reduction(H₂-TPR), and X-ray photoelectron spectroscopy(XPS). High-resolution TEM images, XPS measurements, H₂-TPR experiments coupled with PXRD results determined the evolution of Ni and W species. It is found that a trace amount of W from H₂WO₄ can significantly improve Ni dispersion on SBA-15 (Ni₅₀W/SBA-15) with Ni⁰ andnon-stoichiometric WO_x species as small as ca. 3.6 nm. The prepared Ni_xW/SBA-15 was utilized for CO₂ hydrogenation, which showed that a higher W content restrained the CO₂ hydrogenation while a lower W ratio promoted both conversion rate and selectivity for methane compared with Ni/SBA-15. The Ni₅₀W/SBA-15 catalyst showed the best performance with a 93.3% CO₂ conversion rate and 99.7% selectivity for methane at 400 ^oC under 0.1 MPa and maintained ca. 97% initial performance for 24 h. Tracking product evolution experiments by in-situ Fourier transform infrared spectrascopy(FTIR) indicated that a small amount of W can modify the surface of Ni particles by geometric coverage and electronic modification, which facilitates the adsorption of the CO intermedia and results in the formation of CH₄. This work provides a new clue to fabricating efficient CO₂ conversion bimetallic materials.