Influence of Activation Method on Coconut-Shell-Derived Carbon Supports for Ni and Ni–Ce Catalysts in CO ₂ Methanation

High Resolution Image Download MS PowerPoint Slide Three activated carbons derived from coconut shell were investigated as catalyst supports, each prepared using a different activation method: physical activation with CO 2 and chemical activation with H 3 PO 4 and ZnCl 2 . Ni and Ni–Ce catalysts were synthesized via incipient wetness impregnation and co-impregnation, respectively, and characterized using ICP analysis, N 2 adsorption, TGA, SEM-EDX, and TEM. Prior to catalytic evaluation, the materials were assessed in terms of hydrophobicity, textural properties (pore volumes, surface areas), and metal dispersion. Catalytic performance was tested under both conventional and aging conditions at atmospheric pressure over a temperature range of 240–450 °C (GHSV = 86100 mL h –1 g cat –1, H 2:CO 2 = 4:1). The activation method was found to strongly influence the structural properties of the supports. In particular, CO 2 activation produced a predominantly microporous carbon, whereas chemically activated carbons exhibited different pore structures and contained residual species from the activating agents. Among the Ni-based catalysts, the one supported on CO 2 -activated carbon showed the best performance, attributed to its higher basicity, measured by the determination of the pH PZC . The incorporation of Ce further enhanced catalytic activity by improving Ni dispersion and promoting CO 2 activation on CeO 2 sites. Overall, the highest CH 4 yield (∼80% at 370 °C) was achieved with catalysts containing 20 wt % Ni and 20 wt % Ce supported on H 3 PO 4 and CO 2 -activated carbons. The CO 2 -activated support was identified as the most promising due to its greener preparation route and superior performance, maintaining stable activity under aging tests without significant deactivation.