Synthesis of highly efficient and stable Ni/CexZr1-xGdxO4 and Ni/X-Al2O3 (X = Ce, Zr, Gd, Ce-Zr-Gd) nanocatalysts applied in methane reforming reactions

Abstract A series of nanocatalysts including Ni/CeZr0.5GdO4 as well as four Ni/X-Al2O3 (X = Gd, Zr, Ce, Ce-Zr-Gd) were synthesized and applied in the dry (DRM) and steam (SRM) reforming of CH4 to evaluate their catalytic activities. The XRD, EDX, FE-SEM, TEM, TGA, BET, NH3-TPD and TPR analyses as well as the catalytic reactions were performed to study and compare the properties of all nanocatalysts. The highest activity in both of the DRM and the SRM reactions was afforded using the catalyst Ni/CeZr0.5GdO4 but the Ni/Al2O3 illustrated the least efficiency among all of the samples. The CH4 conversions measured for the DRM and SRM processes using the Ni/CeZr0.5GdO4 nanocatalyst were 92.89 and 93.93%, respectively, with a feed GHSV=54000 h−1 at 800 °C indicating the SRM reaction could afford a greater efficiency. It was surprising that the TGA diagrams indicated negligible carbon deposition (1.98%) on the Ni/CeZr0.5GdO4 catalyst surface used in the DRM whereas 8.5, 9.2, 11, 16 and 24% coke amounts were measured for the Ni/Gd-Al2O3, Ni/Ce-Zr-Gd-Al2O3, Ni/Ce-Al2O3, Ni/Zr-Al2O3 and Ni/Al2O3 samples, respectively. The time on stream (TOS) experiments displayed that for the two DRM and the SRM, the CH4 conversions were slightly decreased using the Ni/CeZr0.5GdO4 catalyst after 30 h but the Ni/Ce-Zr-Gd-Al2O3 and Ni/Al2O3 samples exhibited greater activity losses. Such results illustrated that the Ni/CeZr0.5GdO4 catalyst was a very stable sample with a high catalytic activity confirming it could be very suitable for application in the methane reforming processes.