Pt/Ce-Sm-Ox 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-Ox 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-Ox 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-Ox 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.