•La2O3-modified Ni/SBA-15 catalysts were studied in CH4 reforming with CO2.•Ni dispersion and the catalytic performance were improved with La addition.•The promoting intermediates were trapped in a designed infrared cell.•La promotes the reforming mainly by adsorbing CO2 and facilitating CO* and CHxO*.La-promoted Ni/SBA-15 catalysts (molar ratio of La2O3/Ni = 0.10, 0.25) were prepared by the wetness impregnation method for the reforming of CH4 with CO2. The La species are highly dispersed on the catalyst and cause smaller nickel particles in comparison with the Ni/SBA-15 catalyst. The presence of La in Ni/SBA-15 evidently improves the catalytic activity and stability. For the reaction mechanism study, a special infrared cell under rapid heat dissipating was designed to trap the transient intermediates (e.g., CHxO*) on the catalysts. For La–Ni/SBA-15 with La2O3/Ni = 0.10, the adsorbed Ni(CO)4 and bridge-bonded CO (Ni2–CO) form on the nickel surface with large particle size, while for the one with La2O3/Ni = 0.25, CHxO* (x = 2, 3) surface species occur on small sized nickel particle. The results indicate that highly dispersed La effectively promotes CO2 dissociation into oxygen atom which facilitates the formation of the different C1 intermediates from the adsorbed CH4 on the neighboring nickel species depending on the varied La2O3/Ni ratio.Graphical abstract

•IGC was used to study surface property of MCF loaded with the sized Ni particle.•High adsorption free energy and heat of aromatics on MCF with ca. 5 nm Ni particle.•Strong dispersive and specific interaction on MCF with small Ni particle (<1.4 nm).•Ni highly dispersed on MCF promotes the great interaction with aromatics structure.The mesocellular silica foams (MCF) modified by different sized Ni nanoparticles (≤27.4 nm) were prepared through the wetness impregnation of low metal content (0.5–2.0 wt%). The technology of inverse gas chromatography (IGC) was used to evaluate the size effect of Ni nanoparticles on the surface property of Ni/MCF and the probes of four n-alkanes (C6–C9), cyclohexane, benzene, toluene, trichloroethylene, and tetrachloroethylene were tested in the 463.2–493.2 K temperature range. High free energy of adsorption and enthalpy of adsorption for the aromatic hydrocarbons were found over 1.0 wt% Ni/MCF with small nanoparticles of ca. 5 nm. The dispersive interaction parameter γSD, and specific interaction parameter Isp increase with Ni nanoparticle size decreasing over Ni/MCF. The results indicate that Ni species highly dispersed on MCF support significantly promote the surface property of the specific interaction with the aromatic structure.

•IGC was used to study surface property of KIT-6 impregnated by Ni species.•High adsorption energy and strong interaction on KIT-6 with 1.0 wt% Ni impregnated.•Ni species penetrates into the micropore of KIT-6 and becomes ‘unaccessible’.•Ni species with high dispersion shows ‘unexpected’ low activity in CH4 dry reforming.Inverse gas chromatography (IGC) was employed in evaluating the catalytic surface of meso-microporous KIT-6 impregnated Ni (0.5–2.0 wt%) in methane dry reforming reaction. The free energy of adsorption did not changed significantly for the sample modified with highly dispersed Ni species (0.5 wt%). At higher Ni loadings, higher free energy of adsorption and enthalpy of adsorption of the probes were observed, together with high dispersive interaction and specific interaction of aromatics. The results indicated that during the impregnation, Ni species preferably penetrated into the microporous region to form Ni particles and became ‘unaccessible’. This feature was used to understand the dependence of activity on Ni loading for the gas phase catalytic methane reforming with carbon dioxide on Ni/KIT-6. The lower TOF at low metal loadings was attributed to Ni particles located in the micropores which result in diffusional constraint of reactants and products.