Sacrificial Carbon Strategy toward Enhancement of Slurry Methanation Activity and Stability over Ni-Zr/SiO2 Catalyst

Catalytic Performance for CO Methanation over Ni/MCM-41 Catalyst in a Slurry-Bed Reactor

The Ni-based catalyst has been intensively studied for CO methanation. Here, MCM-41 is selected as support to prepare xNi/MCM-41 catalysts with various Ni contents and the catalytic performance for CO methanation in a slurry-bed reactor is investigated under different reaction conditions. The CO conversion gradually increases as the reaction temperature or pressure rises. As the Ni content increases, the specific surface area and pore volume of xNi/MCM-41 catalysts decrease, the crystallite sizes of metallic Ni increase, while the metal surface area and active Ni atom numbers firstly increase and then slightly decrease. The 20Ni/MCM-41 catalyst with the Ni content of 20 wt% exhibits the highest catalytic activity for CO methanation, and the initial CH4 yield rate is well correlated to the active metallic Ni atom numbers. The characterization of the spent xNi/MCM-41 catalysts shows that the agglomeration of Ni metal is accountable for the catalyst deactivation.

Carbon Deposition Behavior of Ni Catalyst Prepared by Combustion Method in Slurry Methanation Reaction

Ni/Al2O3 catalyst prepared by combustion method was applied in a slurry methanation reaction to study the catalytic performance, especially the regeneration performance. The catalyst properties were characterized by (X-Ray diffraction) XRD, Inductively coupled plasma atomic emission spectrometer (ICP-AES), Nitrogen adsorption-desorption, Transmission electron microscopy (TEM), Thermogravimetric analysis (TG/DTG), Temperature programmed oxidation (TPO), and H2 chemisorption before and after reaction. The results show that the catalyst deactivation was mainly due to carbon deposition, which exhibited amorphous carbon films and formed by the disproportionation of CO. The carbon deposition was formed on the catalyst surface and existed as carbon films during the reaction, then it gradually separated from the catalyst surface, generated an overlapping multi-layer three-dimensional carbon structure, which covered the active site and blocked the pores. As a result, the metal surface area of catalyst decreases, as well as the activity. The carbon deposition could be removed by oxidative calcination without destroying the catalyst structure, the active sites could be re-exposed and the catalyst activity could be recovered.