Nickel catalysts supported on silica microspheres for CO2 methanation

Nickel catalysts supported on silica microspheres were prepared by the application of porous resin beads (Amberlite XAD7HP) as hard template using different order of nickel nitrate and tetraethoxysilane (TEOS) introduction. Large nickel oxide nanoparticles distributed over silica microspheres were formed when nickel precursor was introduced directly to the polymer template prior to the silica framework development or added into the silica-polymer composites. On the other hand, an impregnation of as-prepared silica microspheres after template removal led to the formation of small nickel oxide nanoparticles. The catalysts showed hierarchical pore structure. Low-temperature nitrogen adsorption/desorption and photoacoustic Fourier-transform infrared spectroscopy studies revealed slight changes of porosity and surface properties of catalysts affected by the synthesis methods. X-ray diffraction, scanning and transmission electron microscopy, temperature-programmed reduction and hydrogen desorption studies were used for determination of the properties of metallic nickel nanoparticles. It was stated that the activity and selectivity of catalysts in the CO2 methanation reaction was related to the active surface area and the size of nickel nanoparticles. An increase in CO2 conversion and selectivity to methane at low temperatures (220-350 degrees C) with an increase in active surface area and decrease in nickel crystallite size was observed.