CO methanation reaction over the Ni

CO methanation reaction over the Ni/Al2O3 catalysts for synthetic natural gas production was systematicallyinvestigated by tuning a number of parameters, including using different commercial Al2O3 supports and varying NiO and MgOloading, calcination temperature, space velocity, H2/CO ratio, reaction pressure, and time, respectively. The catalyticperformance was greatly influenced by the above-mentioned parameters. Briefly, a large surface area of the Al2O3 support, amoderate interaction between Ni and the support Al2O3, a proper Ni content (20 wt %), and a relatively low calcinationtemperature (400 °C) promoted the formation of small NiO particles and reducible β-type NiO species, which led to highcatalytic activities and strong resistance to the carbon deposition, while addition of a small amount of MgO (2 wt %) couldimprove the catalyst stability by reducing the carbon deposition; other optimized conditions that enhanced the catalyticperformance included high reaction pressure (3.0 MPa), high H2/CO ratio (≥3:1), low space velocity, and addition of quartzsand as the diluting agent in catalyst bed. The best catalyst combination was 20−40 wt % of NiO supported on a commercialAl2O3 (S4) with addition of 2−4 wt % of MgO, calcined at 400−500 °C and run at a reaction pressure of 3.0 MPa. On thiscatalyst, 100% of CO conversion could be achieved within a wide range of reaction temperature (300−550 °C), and the CH4selectivity increased with increasing temperature and reached 96.5% at a relatively low temperature of 350 °C. These results willbe very helpful to develop highly efficient Ni-based catalysts for the methanation reaction, to optimize the reaction process, andto better understand the above reaction.