Carbon Dioxide Methanation Over Nickel Catalysts Supported on Activated Carbon at Low Temperature

Abstract

The methanation of carbon over nickel catalysts supported on activated carbon was investigated using a continuous flow microreactor. Catalysts with nickel loadings of 5, 7, and 10% were synthesised by incipient wetness impregnation methods and characterised using Brunauer–Emmett–Teller (BET), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), H₂-temperature-programmed reduction (TPR), BET, XRD, SEM, TEM and H₂-TPR. The methanation reaction was studied over the temperature range 200–500°C with a H₂ to CO₂ ratio of 4 : 1 in He and at 1 atm. With an increase in Ni content from 5 to 7 % both conversion of CO₂ and CH₄ selectivity increased. Increasing the nickel content to 10 %, however decreased conversion and selectivity due to the larger crystallite size and lower surface area of the catalyst. The most active catalyst with 7 % Ni does not deactivate during 15 h time on stream at 350°C. The high catalytic activity and stability of the studied catalysts is a consequence of the reducibility of Ni and a synergetic effect between the nickel active sites and the activated carbon surface.