Tuning of the Performance of a Ru-Ni-Mg/Ceria-Zirconia Dry Reforming Catalysts through Strategic Reduction Conditions and Varying Ru Loading Amount

Our past research on low temperature reforming catalysts for intensified, one-step conversion of biogas sourced methane and carbon dioxide to liquid fuels has led to the development of high performing Pt/ceria-zirconia based catalysts. However, to minimize the material formulation cost without compromising performance, we sought a less expensive metal to replace Pt. A series of Ni (1.4wt%)-Mg (1.0wt%)-Ce_0.6Zr_0.4O₂(CZO) samples promoted with Ru (0.16-0.32 wt%) were synthesized using the incipient wetness method. The reducibility of the catalysts was found to increase with increasing Ru content, and the low reduction temperatures were between 163 and 205 ℃. N₂ physisorption analysis revealed the materials were mesoporous with a specific surface area between 29.1 and 42 m²/g. Diffraction patterns ascribed to the cubic-fluorite structure were found from the Powder X-ray diffraction. This result was supported by the Raman spectra, which showed peaks belonging to the F2g bands of ceria. In-situ CO DRIFTS measurements presented bands for linear CO adsorption on Ru metal and the formation of carbonates and formates. The activity of the materials for dry-reforming was evaluated using temperature-programmed and steady-state experiments. The reactants’ conversions increased with increasing Ru loading. CH₄ conversion rates at 450 ℃ for the 0.16Ru-CZO and 0.16Ru-1.4Ni-1.0Mg-CZO samples were 11.9 and 6.12 µmol/g_cat/s respectively. The CH₄ apparent activation energy at 470-510 ℃ was found to be 14.0 and 19.1kcal/mol for 0.16Ru-CZO and 0.16Ru-1.4Ni-1.0Mg-CZO, respectively. Changes in conversion rates and apparent activation energies were observed with increasing the reduction temperature from 300 to 400 ℃. The 0.16Ru-CZO sample was found to be stable after a 10 h TOS study with no decrease in activity and no coke formation was detected. The results obtained indicate that Ru is a suitable replacement for Pt and provides insights into the effect of reduction treatment, metal loadings and metal-metal interactions on the catalyst performance.