Selective adsorption of greenhouse gases on the residual carbon in lignite coal liquefaction

Abstract Adsorption of CO 2 , CH 4 , and N 2 on activated carbon now is considered as a promising approach for greenhouse gas capture and/or separation. The objective of this study was to determine whether the residual carbon in lignite coal liquefaction could be used as an inexpensive and effective replacement for activated carbon. The chemical structure and functional groups transformation of residual carbon were analyzed using Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR). The adsorption properties of CO 2 , CH 4 , and N 2 on the residual carbon were investigated at temperatures of 0 °C, 10 °C and 20 °C up to a pressure of 100 kPa. The adsorption kinetics and thermodynamics were also discussed from the uptake curves with the isothermal model. The separation of CO 2 /CH 4 , CH 4 /N 2 , and CO 2 /N 2 binary mixtures was determined using ideal adsorbed solution theory (IAST) model. At 0 °C and 100 kPa, the simulated selectivities of CO 2 /CH 4 , CH 4 /N 2 , and CO 2 /N 2 in 50/50 vol.% were 35, 11, and 38, respectively. Significant increased values than have previously been reported in the literature. The residual carbon from solvothermally treated lignite coal could be developed for greenhouse gas capture or biogas purification to achieve fuel grade quality.