Monodispersed and nanostructrured Ni/SiO2 catalyst and its activity for non oxidative methane activation

In this paper, we prepared nickel nanoparticles for the non oxidative methane activation. A nickel acetate solution was impregnated on silica support and then reduced with NaBH4 (NiB/SiO2) exhibiting only small metallic Ni0 particles of the order of 15 nm. Part of this solid was then oxidized under mild conditions, where Ni ions were re-structured and redistributed as a Ni-Ox/SiO2 oxide solid that after reduction with hydrogen favored the formation of smaller Ni particles. XPS spectra of the Ni-Ox/SiO2 sample before the reduction showed that NiO is the predominant species at the surface and after reduction it indicates the presence of small metallic nickel particles at the surface interacting with the SiO2 support. XRD and DRIFTS results confirm the structural interaction of metal-support after the mild oxidation and TEM images indicate small particles of the order of 3.5 nm and surface defects. The non oxidative methane activation evidenced significant formation of methane coupling products over the Ni-Ox/SiO2 catalyst during methane chemisorption. Chemisorption of methane on the NiB/SiO2 showed ethane formation only. The temperature programmed surface hydrogenation (TPSH) results suggested the formation of carbidic species at lower temperatures of adsorption.

.Figure optionsDownload high-quality image (220 K)Download as PowerPoint slideResearch highlights
► Preparation of NiB/SiO2 and Ni-Ox/SiO2 for non oxidative methane activation.
► Chemisorption of CH4 in the temperature range 473–773 K, followed by hydrogenation.
► Ni-Ox/SiO2 evidenced great ability for methane coupling in chemisorption to C2.
► XPS and TEM results evidence metallic Ni particles of 3.5 nm at surface.