Ni/Ce_0.8Zr_0.2O_2-xsolid solution catalyst: A pathway to coke-resistant CO2 reforming of methane

The CO2 reforming of methane effectively produces syngas using two prevalent greenhouse gases: CO2 and CH4. This study investigates the performance of three nickel-based catalysts, Ni/ZrO2, Ni/CeO2 and Ni/Ce0.8Zr0.2O2-x, in the DRM reaction. Each catalyst was thoroughly examined using a range of techniques, including XRD, TPR, BET, TPD, HR-TEM, Raman, O2-TPD, XPS, TGA and CO2-TPD to assess its structural and catalytic properties. The Ni/Ce0.8Zr0.2O2-x catalyst, combining the advantages of both supports to form a solid solution, achieved the best overall performance with enhanced activity and stability. Meanwhile, Ni/ZrO2 and Ni/CeO2 catalysts showed a tendency towards deactivation over extended reaction times. Characterization showed that incorporating zirconia into the CeO2 lattice led to the solid solution synthesis with a solely defective cubic fluorite phase, as confirmed by XRD and Raman analysis. The TPR and CO2-TPD revealed that the resulting Ni/Ce0.8Zr0.2O2-x catalyst possesses strong metal-support interaction and higher CO2 adsorption compared to pure CeO2 and ZrO2 samples. This composite support facilitated the generation of oxygen vacancies/active oxygen species, which are beneficial for reducing coke deposition. The Ni/Ce0.8Zr0.2O2-x catalyst demonstrated exceptional performance, achieving around 90.8% methane conversion and 91.0% CO2 conversion at 700°C, with the resulting H2/CO ratio precisely equal to one. The stability test revealed remarkable stability against coke deposition for Ni/Ce0.8Zr0.2O2-x; meanwhile, Ni/ZrO2 and Ni/CeO2 are more susceptible to coke deposition, with the Ni/ZrO2 sample showing a greater tendency towards graphitic coke deposition. This study highlights the importance of catalyst supports in optimizing the performance of nickel-based catalysts for CO2 reforming applications.