Desulfurization and de-ashing of coal through catalytic oxidation using Fe (III) and Cu(II) catalysts loaded in different forms

In the present study, desulfurization and de-ashing of the low rank lignite coal were investigated by catalytic oxidation using H₂O₂/HCOOH oxidation system in the presence of Fe³⁺ and Cu²⁺ as catalysts. The catalysts were loaded in three different forms along with coal during oxidation, including impregnated on coal, as aqueous solutions and supported on activated carbon. Before oxidation, the coal sample was leached with HNO₃ and KOH solutions, out of which HNO₃ exhibited good results. Furthermore, among the three modes of catalysts loading, the catalyst loaded on AC was more efficient. In case of Fe and Cu loaded on AC, about 81% and 71% sulfur and ash were removed with 0.1% Fe/AC. Likewise, in the presence of 0.1% Cu/AC catalyst, the level of sulfur and ash removed was 88.04 and 79.81% respectively. Post-treatment characterization of the coal sample revealed that the heating value of the coal sample has slightly declined with the catalytic oxidation, probably due to surface oxidation of coal, which was confirmed by the FTIR analysis. The XRD analysis of the ash suggested that the coal samples had mostly Quartz, hematite and clay substances, representing the mineral matter in coal, most of these were removed during oxidation.