Capturing carbon dioxide is vital for the future of climate-friendly combustion, gasification, and steam-reforming processes. Dry processes utilizing simple sorbents have great potential in this regard. Long-term calcination/carbonation cycling was carried out in an atmospheric-pressure thermogravimetric reactor. Although dolomite gave better capture than limestone for a limited number of cycles, the advantage declined over many cycles. Under some circumstances, decreasing the carbonation temperature increased the rate of reaction because of the interaction between equilibrium and kinetic factors. Limestone and dolomite, after being pretreated thermally at high temperatures (1000 or 1100 °C), showed a substantial increase in calcium utilization over many calcination/carbonation cycles. Lengthening the pretreatment interval resulted in greater improvement. However, attrition was significantly greater for the pretreated sorbents. Greatly extending the duration of carbonation during one cycle was found to be capable of restoring the CO 2 capture ability of sorbents to their original behavior, offering a possible means of countering the long-term degradation of calcium sorbents for dry capture of carbon dioxide.

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Graphite oxide synthesized with phosphoric acid, labeled “GOP”, shows a higher degree of oxidation and has a larger interlayer spacing than the oxide prepared using the conventional Hummers method, referred to as “GOH”, as confirmed by X-ray photoelectron spectroscopy and X-ray diffraction analyses. This study was performed under the assumption that the oxygen-containing functional groups between the GOP layers are more easily reduced than those between the GOH layers. Raman analysis supported this assumption in that the reduced graphene from GOP has a larger number of sp2 carbons and fewer defects than the graphene obtained from GOH. The relative extent of defects in graphene can be investigated by dibenzothiophene (DBT) adsorption, which requires π–π interactions between the free π-bonds of sp2 atoms from graphene and those from the aromatic ring of DBT. The graphene obtained from GOP showed higher DBT adsorption capacity than that synthesized from GOH. In addition, the DBT adsorption capacity on graphene decreased as the concentrations of other aromatic compounds increased.

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