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

A series of Ni-W catalysts supported on mesoporous SBA-15 with different Ni:W ratios(NixW/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), H-2-temperature programmed reduction(H-2-TPR), and X-ray photoelectron spectroscopy(XPS). High-resolution TEM images, XPS measurements, H-2-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 Ni-0 and non-stoichiometric WOx species as small as ca. 3.6 nm. The prepared NixW/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 degrees C 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.

Automated summary

This study investigated the effect of Ni-W catalysts with different Ni:W ratios on CO2 hydrogenation, and found that a small amount of W can significantly improve the dispersion of Ni on the support, while promoting selective CH4 formation. This provides a new clue for fabricating efficient CO2 conversion materials.