Preparation and characterization of Ni–Co/SiO2 nanocomposite catalysts for CO2 methanation

Abstract

For effective CO2 methanation, monometallic Co(10)/SiO2 and Ni(10)/SiO2 and bimetallic Ni(5)Co(5)/SiO2 and Ni(2)Co(8)/SiO2 nanocomposite (NC) catalysts, where numbers between brackets indicate the metal content (wt%), have been prepared with solvate-stimulated modification, thermal decomposition, and chemical reduction stages using nanosilica A-300 as a carrier. The catalysts were characterized using SEM–EDX, nitrogen physisorption, and X-ray powder diffraction. The samples before and after the reduction with hydrogen have a similar mesoporous texture. The bimetallic Ni–Co/SiO2 NC catalysts showed improved catalytic activity compared to Ni/SiO2. The formers are characterized by the smallest bimetallic crystallites of ca. 12 nm in size. Activity in the methanation of the Ni–Co/SiO2 NC catalysts depends on the cobalt content resulting in a prominent increase in CO2 conversion and methane yield at 250–350 °C. The SEM–EDX analysis showed unusual flower-like nanostructures and proved the random distribution of Ni/Co bimetallic aggregates in the nanosilica matrix at the nanoscale level. Both Ni(2)Co(8)/SiO2 and Ni(5)Co(5)/SiO2 exhibited high activity in the CO2 methanation with 81–88% CH4 yield at 450 °C. The results of thermo-programmed desorption mass spectroscopy revealed that the catalytic reaction is passed through the formation of O-containing intermediates bound to the active Ni–Co and nanosilica sites.