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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. [ABSTRACT FROM AUTHOR]

The mesocellular silica foams (MCF) supported rhodium catalysts, prepared by wetness impregnation method, were tested in CH 4 reforming with CO 2 . Hydrogen temperature-programmed desorption (H 2 -TPD) analysis showed that hydrogen spillover occurs on MCF loaded with highly dispersed rhodium. The turnover frequency of CH 4 (TOF CH4 (s −1 )) increased with the strength rise of spilt-over hydrogen. The promotion mechanism was investigated by controlled atmosphere 13 C and 1 H MAS NMR. The spilt-over hydrogen atoms were found to adsorb on the bridged oxygen sites (Si O Si) of MCF and to form surface terminal silanol groups. Meanwhile, in the reforming reaction steps, CH 4 dissociation into CH 3 * and CH 3 O* decomposition into CH 2 O* occurred. The results confirmed that hydrogen atoms can spill over from highly dispersed rhodium species to the neighboring bridged oxygen atoms of MCF, which promotes the reaction by facilitating rate determining steps of CH 4 dissociation and CH x O*( x = 2, 3) intermediates decomposition on metal surface. [ABSTRACT FROM AUTHOR]

Highlights: [•] 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 CH x O*. [ABSTRACT FROM AUTHOR]

Abstract: The mechanism of methane reforming with carbon dioxide over 1.0wt.% Rh/SBA-15 catalyst has been studied by the 13C and 1H magic-angle spinning (MAS) NMR spectroscopies under controlled atmosphere condition using 13CH4 + 12CO2 and 12CH4 + 13CO2 as reactants. The effect of temperature in the region of 298–1023K on the reaction was investigated and the contents of various 13C and 1H species were obtained quantitatively by the NMR technique. When treated at 573K, the carbon exchange between methane and carbon dioxide can be observed. With the temperature rising to 773K, the adsorbed CH3O* species is formed but no reforming reaction occurs. In the high temperature range of 873–1023K, the reforming reaction was observed with concomitant appearance of the adsorbed CH2O* species and the intensity of both CH3O* and CH2O* increases with increasing temperature, indicating that the decomposition of CH3O* to CH2O* occurs and the products of dry reforming are formed from decomposition of the adsorbed CH2O* species. [Copyright &y& Elsevier]