Pt/Ce-Sm-O_x catalysts for stable steam-assisted biogas reforming: comparative performance and carbon accumulation

Steam-assisted biogas reforming can tune syngas composition, but long-term operation is limited by catalyst deactivation and carbon accumulation. To compare the effects of Ce-, Sm-, and combined Ce/Sm-containing oxide environments under identical conditions, Pt/CeO₂, Pt/Sm₂O₃, and Pt/Ce-Sm-O_x catalysts containing a nominal Pt loading of 1 wt% were prepared by a citrate-assisted sol-gel method. Under a CH₄/CO₂/H₂O/N₂ feed ratio of approximately 3:2:2.7:1, Pt/Ce-Sm-Ox achieved approximately 91 % CH₄ conversion and 55 % CO₂ conversion at 800 °C. During the 100 h test, the CH₄ and CO₂ conversions remained within 90 %-92 % and 52 %-56 %, respectively, and the H₂/CO ratio was approximately 1.8. The spent Pt/Ce-Sm-O_x catalyst showed an apparent oxidative mass loss of approximately 1 wt%, compared with an apparent oxidative mass loss of approximately 19.3 wt% for spent Pt/CeO₂. Hydrogen temperature-programmed reduction (H₂-TPR) and carbon dioxide temperature-programmed desorption (CO₂-TPD) showed formulation-dependent reducibility and CO₂-desorption behaviour, while the density of the post-reaction electron paramagnetic resonance (EPR)-active defect-related centres over Pt/Ce-Sm-O_x was approximately 1.9 times that over Pt/CeO₂. Together with the results of in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), post-reaction microscopy, and Raman spectroscopy, these observations support, but do not prove, a working hypothesis involving complementary roles of Pt and the Ce/Sm-containing oxide.