CO2 and CH4 sorption on carbon nanomaterials and coals - Comparative characteristics

The aim of this research was to compare the structure, sorption properties and the kinetics of sorption to CO2 and CH4 in nanomaterials with a very orderly structure and in structurally heterogeneous coal. The authors tested synthetic materials such as multiwall carbon nanotubes (MWCNT) and reduced graphene oxide (rGO) as well as natural materials such as coals of various ranks. The value of the surface area of Langmuir and Brunauer, Emmett and Teller, in MWCNTs and rGO was much higher than in the coal. The course of CH4 and CO2 sorption of the materials was investigated and the parameters of sorption isotherms in the pressure of 0-2.0 MPa were determined. The nanomaterials reached the sorption equilibria much faster than the coal. The highest total CH4 sorption capacity was found in low-rank coal. The highest CO2 total sorption capacity was found in MWCNTs and low-rank coal. The highest relative mean drop in CH4 and CO2 sorption capacity resulting from the increasing measurement temperature was found in the MWCNTs and the low-rank coal. The authors analysed the courses of CH4 and CO2 sorption kinetics in the materials of highly different structures. The kinetics of CH4 and CO2 accumulation in MWCNT and rGO nanomaterials progressed almost instantaneously, and their rate was many times higher than in the case of kinetics on hard coals.