Controlled atmosphere 13C and 1H MAS NMR study of reforming route of methane with carbon dioxide over Rh/SBA-15

The mechanism of methane reforming with carbon dioxide over 1.0 wt.% 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 298–1023 K on the reaction was investigated and the contents of various 13C and 1H species were obtained quantitatively by the NMR technique. When treated at 573 K, the carbon exchange between methane and carbon dioxide can be observed. With the temperature rising to 773 K, the adsorbed CH3O* species is formed but no reforming reaction occurs. In the high temperature range of 873–1023 K, 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.

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► CH4 reforming with CO2 over Rh/SBA-15 was studied by 13C and 1H MAS NMR.
► Isotopic scrambling and dry reforming reaction were observed by 13C MAS NMR.
► CH3O* and CH2O* species were found by 1H MAS NMR.
► Three crucial steps in the reforming route were found.