Tóm tắt

In the view of the current environmental problems, especially in the light of mitigating the effect of globalrnwarming due to anthropogenic carbon dioxide (CO2) emissions to the atmosphere, numerous technolo-gies have been proposed like CO2sequestration in deep and unmineable coal seams. This paper presentsrnadvanced characterization of two South African coals upon short-term flue gas exposure. A syntheticrnindustrial flue gas containing 12% CO2, 5.5% O2, 82% N2, 0.38% SO2, and 0.12% NO2was used in the study.rnThe two coals were exposed to the flue gas at a temperature of 60u0001C and pressure of 9.0 MPa for up torn120 h. Subsequently, the coals were analysed using conventional characterization techniques (densityrnStereopycnometer, proximate and ultimate, textural, and petrographic) and advanced characterizationrntechniques (carbon 13 nuclear magnetic resonance (rn13rnC NMR), attenuated total reflectance-Fourier trans-form infrared (ATR-FTIR), wide-angle X-ray diffraction (WXRD), and field emission gun scanning electronrnmicroscopy (FEG-SEM)) to check the physical and chemical structural changes during the CO2/flue gasrnsorption to simulate sequestration.rnThe conventional analytical techniques have revealed significant observable changes of the physicalrnand chemical structure of the coal upon flue gas exposure. However, clear changes in chemical structurernwere observed through ATR-FTIR analysis. The observable change in surface chemistry of the coals sug-gests that there is most certainly a chemical interaction between the coals and the flue gas components atrnhigh pressure. Slight structural changes were observed from FEG-SEM and WXRD characterization. Lastly,rnthere were no obvious structural changes from the results obtained fromrn13rnC NMR, except for slightrnchanges in the aliphatic carbons bonded to oxygen of 37% for Coal EML and 27% for Coal SML. Thesernchanges could be due to the presence of oxygen in the flue gas; thus, substituting to form stronger inten-sities of the C-O and COO bonds as observed in the ATR-FTIR spectra