Research Information System
ChemCatChem, 2025 (SCI-Expanded)
Dry reforming of methane was studied over Ni/Al2O3 catalyst at 600 °C with varying CO2/CH4 ratios (0.2, 0.5, 1, 2, 5). 13CO2 as well as 12CO2 were used along with 12CH4 and resulting carbon was characterized with 13C solid state NMR spectroscopy in order to elucidate the role of CO2 in carbon build up. 13C NMR results revealed that carbon in the deposited coke not only came from CH4, but also from CO2. CO2 saturation coverage is determined by adsorption calorimetry as 0.02 mole/site at 323 K, populated on Al2O3. The critical CO2/CH4 ratio for the onset of carbon growth at atmospheric pressure was determined as 1.8 in good agreement with the literature. The effect of CO2/CH4 ratio on the type of carbon formation was investigated by HCTEM. Long-term reaction tests resulted in octopus carbon structure with several fibers growing from one nickel crystal. Above the critical CO2/CH4 ratio, carbon growth was inhibited, only a small amount of amorphous carbon could form. At CO2/CH4 ratios below the critical value, whisker formation was clearly observed. When the steady state operation of reforming reaction was changed to a transient operation by injecting pure CO2 flow to the reactor, coke deposition could be inhibited at the expense of hydrogen stoichiometry.