CO<sub>2</sub> Methanation on Ni Catalysts Supported over Activated Carbons Derived from Cork Waste
Filipe Mateus, Paula Teixeira, J.M. Lopes, Carlos Henriques, Carmen Bacariza
Abstract
High Resolution Image Download MS PowerPoint Slide Activated carbons (ACs) derived from cork wastes were for the first time used as supports for CO 2 methanation catalysts. Cork wastes (natural-N and processed-P) were physically activated under N 2 /H 2 O (v) atmosphere at 800 °C to obtain the corresponding AC supports (AC N and AC P, respectively). Ni and Ni-CeO 2 catalysts were prepared by loading the ACs with 15 wt % Ni (Ni/AC) or 15 wt % Ni and 15 wt % Ce (NiCe/AC) by incipient wetness impregnation or co-impregnation, respectively, using 2-propanol as the solvent. For comparison purposes, a commercial activated carbon (AC C ) was impregnated with the same metals and loadings. The catalysts were characterized by N 2 and CO 2 sorption, XRD, TGA, SEM, and TEM, and finally tested at atmospheric pressure under CO 2 methanation conditions (86 100 mL·h –1 ·g cat –1, H 2 /CO 2 = 4:1). Microporous activated carbons with high surface areas (757–903 m 2 ·g –1 ) were obtained from natural and processed cork wastes. While nickel was incorporated as Ni 0 over the materials, CeO 2 phases were detected on Ni-CeO 2 catalysts. The incorporation of these metal species over the activated carbons induced a decrease of the textural properties, while the affinity toward CO 2 was promoted by CeO 2 . In terms of average Ni 0 particle sizes, while the smallest ones were detected on Ni/AC C (8 nm) for Ni/AC samples, the addition of CeO 2 led to a remarkable decrease of this parameter on cork-derived materials (from 20 to 7 nm and from 33 to 16 nm on AC N and AC P, respectively). Higher CH 4 yields were exhibited by CeO 2 -containing catalysts, with relative CH 4 yield increases of 210–670% using Ni samples as the basis being observed. This was ascribed to CeO 2 ’s ability to activate CO 2 and promote Ni 0 dispersion. The best results (CH 4 yield of 73% at 400 °C) were obtained for the NiCe/AC N catalyst, its performance being similar to or higher than that reported in the literature for similar systems, thus motivating further development and optimization of these materials for CO 2 methanation.