Anthracite can be defined as a form of coal that has the chemical formula: C208H162O12N4. The coal contains high levels of sulfur and nitrogen. Due to its high heating values and low ash contents, anthracite is the most preferred raw material when making activated charcoals. To reduce the ash in activated carbons, it is necessary to be aware of the mineral composition and distribution on the surface.
A study has been conducted on the influence of KOH activation in anthracite mineralogy, surface elements composition and the results. In order to achieve this, steam (H2O), as the activating agents, was used in a combination of physical and chemical activation. Then, the proximate analyses of the resulting carbon products were performed. SEM with EDS was used for the analysis of microcrystalline composition, surface elemental structure, and anthracite microcrystalline.
Based on the above results, a molecular model of the Yangquan anthracite was established. Models were created with Kingdraw's chemical drawing software, and then imported to the MestReNova program for molecular modeling. The vibrational spectrum (V-V), as well as the orbital spectra, were calculated for the anthracite. These were compared against the predicted molecular model. The 13C NMR of the molecular model for anthracite was well-aligned with the experimental spectra.
Furthermore, the A-O and V-V spectral patterns of the anthracite were used to generate vibrational atomic model potentials. These potentials are used to calculate the bonding energies between oxygen-containing groups within the anthracite molecules. Anthracite's oxygen substitution and oxygen-grafting fat content were measured using 13C NMR. The anthracite contains four hydroxyls. It was estimated that the aromatic ring contains about ten protons.
In addition, the XPS experiment revealed that the sulfur in anthracite was mainly present in the form of sulfate and nitrate. In anthracite, nitrogen is mainly present as pyridines and pyrroles.
SEM-EDS images of the sinter for 40% anthracite replacement were analyzed. Hematite (the primary component of the ash) and calcium ferrite were found to be its main constituents. In addition, complex silicate containing Si, Al, and Fe was also detected.
SEM/EDS images showed anthracites arranged into clusters over the surface particle. They were then surrounded by eutectic hematite calcium ferrite complex silicate. SEM/EDS mapping revealed the presence of a greater area for hematite or calcium ferrite than that for complex silicate. It is possible to explain this sinter formation by the chemical reaction between the two elements. These findings suggest that the ash reduction reaction in anthracite is triggered by a physisorption mechanism.
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