Catalytic CO2 Methanation Over Modified Carbon-Supported Ruthenium: The Influence of the Support Type on the Properties and Activity of the Catalyst

The influence of the type of carbon support on the catalytic activity of Ru/graphitized carbon systems in carbon dioxide methanation was evaluated. Four partly graphitized carbons with varying surface areas (from 50 to 1417 m(2)/g) were used as supports. The prepared samples were characterized by N-2 physisorption, TG-MS studies, H-2-TPR, CO2-TPD, XRD, XAS, TEM/STEM, Raman spectroscopy and CO chemisorption. Both the mode of particle size distribution and the dispersion of the active phase clearly depend on the carbon texture; dispersion changes from 27% to almost 90% with increasing carbon support surface area. The degree of support graphitization affects its resistance to undesired methanation under reaction conditions. The activity tests conducted in a model H-2-rich stream with very low CO2 concentration (1 vol% CO2) show that the catalysts exhibit good activity, achieving a 20% conversion of CO2 at a temperature of 270 degrees C. The increase of the average Ru particle size leads to about sevenfold increase in the CO2 conversion and a nearly 20-fold increase in TOF values. The catalytic activity or Ru/carbon catalysts is also associated with the presence of basic sites on their surface.