Effect of MgO Promoter on the Structure, Performance and Carbon Deposition of Ni-Al2O3 Catalyst for CO Methanation Based-on Slurry-bed Reactor

A series of Ni/MgO-Al2O3 catalysts with different MgO abundance were prepared by mechanochemical method for CO methanation based-on slurry-bed reactor. The prepared catalysts were characterized by X-ray diffraction (XRD), H-2 temperature-programmed reduction (H-2-TPR), N-2 adsorption-desorption, thermogravimetric analysis (TG-DTG) and temperature-programmed hydrogenation (TPH) techniques, and CO methanation performance evaluation was carried out for the samples. Results showed that the catalyst with MgO loading of 2 wt.% (Ni/MgO(2)-Al2O3) presented smaller Ni grain size of 9.64 nm and larger specific surface area of 329 m(2) . g(-1), indicating that a well dispersion of active component on the catalyst. Evaluation results showed that Ni/MgO(2)-Al2O3 could improve the activity of catalyst for CO methanation. Carbon deposition analysis, from TG-DTG characterization, found that MgO could significantly inhibit the formation of carbon deposition in the reaction process. The amount of carbon deposition on Ni/MgO(2)-Al2O3 was the least, only 6.5 %, and the deposited carbon was consisted with the results obtained from TPH analysis. Kinetic analysis showed that the carbon removal reaction mainly occurred at the stage of 250-550 degrees C. And the activation energy from carbon removal reaction for Ni/MgO(2)-Al2O3 was lower to 13.12 kJ/mol, demonstrating that the catalyst with MgO as additive is more beneficial to anti-carbon ability.