Yttrium modified layered double hydroxide derived Ni-based catalysts for effective CO2 methanation at low temperatures

Ni-based catalysts derived from Ni-Al-Y layered double hydroxides with various amounts of yttrium were synthesized by a condensation reflux method. At the optimized Al/Y atomic ratio of 24/1, the obtained H-Ni 75 Al 24 Y 1 sample showed the highest CO 2 methanation performance. At a WHSV of 15,000 mL h -1 g -1 and a pressure of 0.1 MPa, the CO 2 conversion reached 84.1% with 100% selectivity to CH 4 at 250°C, which was much higher than that of H-Ni 75 Al 25 (75.7%) prepared by the hydrothermal method. Furthermore, the CO 2 conversion over H-Ni 75 Al 24 Y 1 sample rose to 88.7% at 300°C, which exceeded that of the Y-free counterpart (84.1%). The introduction of Y altered the amount and distribution of basic sites as revealed by CO 2 -TPD and led to smaller size and higher dispersion of Ni as proved by XRD, TEM and XPS. The H 2 -TPR result verified stronger metal-support interaction but higher amount of reducible Ni weakly interacted with the support in Ni 75 Al 24 Y 1 LDH sample compared with the Y-free counterpart. As a result, the dissociation of H 2 over Ni sites and subsequent hydrogenation became faster based on the in situ DRIFTS results. Dual pathways were proposed to illustrate the reaction mechanism of CO 2 methanation.