Boosting Ni Dispersion on Zeolite-Supported Catalysts for CO<sub>2</sub> Methanation: The Influence of the Impregnation Solvent
Carmen Bacariza, Salman Amjad, Paula Teixeira, J.M. Lopes, Carlos Henriques
Abstract
In this work, an enhancement of Ni0 particle dispersion over zeolite-supported catalysts was intended by tuning the impregnation solvent. For this purpose, a series of 15 wt % Ni catalysts supported over a Cs-USY zeolite were prepared by incipient wetness impregnation using water, ethanol, methanol, 2-propanol, acetone, or ethylene glycol as solvents. Samples were characterized by TGA, N2 adsorption, XRD, DRS UV–Vis, H2-TPR, CO2-TPD, and TEM and catalytically tested at atmospheric pressure under CO2 methanation conditions (86,100 mL gcat–1 h–1, PCO2 = 0.16 bar, H2/CO2 = 4:1). The use of organic solvents rather than water increased the number of weak and medium basic sites, while 2-propanol and ethylene glycol promoted metal–support interactions. The average Ni0 particle sizes after reduction at 470 °C were significantly different for all the studied solvents, ranging from 13 to 34 nm. Despite the beneficial properties exhibited by the catalyst prepared using ethylene glycol concerning metal particle dimensions and the number of weak and medium basic sites, 2-propanol allowed the highest CO2 conversion and CH4 selectivity (64 and 95%, respectively, at 350 °C), probably because of the partial damage of the zeolite structure observed when ethylene glycol was used. Materials prepared within this work were finally compared with other Ni-based catalysts from the literature, assessing the corresponding catalytic activity from CH4 production rates. Their performances were shown to be similar to or higher than those of the literature materials, thus confirming the relevance of these Ni/zeolite catalytic systems and motivating further developments towards this reaction.