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(Ni x W/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 H 2 WO 4 can significantly improve Ni dispersion on SBA-15 (Ni 50 W/SBA-15) with Ni 0 and non-stoichiometric WO x species as small as ca . 3.6 nm. The prepared Ni x W/SBA-15 was utilized for CO 2 hydrogenation, which showed that a higher W content restrained the CO 2 hydrogenation while a lower W ratio promoted both conversion rate and selectivity for methane compared with Ni/SBA-15. The Ni 50 W/SBA-15 catalyst showed the best performance with a 93.3% CO 2 conversion rate and 99.7% selectivity for methane at 400 o 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 CH 4 . This work provides a new clue to fabricating efficient CO 2 conversion bimetallic materials.