Organometallic iron precursors, ferrocene and ferric acetate, were impregnated into Illinois No. 6 (IL), Wyoming (WY), and Yalloum (YL) coals by solvent swelling technique in THF, ethanol, and a THF/ethanol binary solvent. Then iron-impregnated coals were pyrolyzed in a flow of helium at atmospheric pressure in a fixed bed and a thermobalance. Conversion of coal nitrogen to N2 was 20, 38, and 30%, respectively, for original IL, WY, and YL coals. Iron formed from both precursors lowered the onset temperature of N2 evolution by 20-100 °C. When ferrocene was impregnated in coals at a concentration of 1.7-1.8 wt % as Fe, nitrogen conversion was increased to 52, 71, and 68% for IL, WY, and YL coals, respectively. Ferric acetate impregnated into IL coal from THF/ethanol solution increased the nitrogen conversion much more than that from ethanol solution. The expansion of microporous coal structure by the swelling was essential for better dispersion of the catalyst precursor. The evolution of HCN as well as NH3 was effectively suppressed above 600 °C by the presence of iron but not influenced significantly by combinations of catalyst precursors and solvents. The increase in N2 yield was compensated by the decrease in nitrogen emitted as HCN and NH3 and in tar and char. The increase in CO evolution from the iron-impregnated IL coal at 600-800 °C was explained by catalytic rearrangement of aromatic structure of char, accompanying the removal of nitrogen as N2. In a range of 600-750 °C, the evolution of CO as well as N2 from the other coals increased remarkably with a significant decrease in CO2 evolution, which was caused by iron-catalyzed CO2 gasification in char micropores.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Fuel Technology
- Energy Engineering and Power Technology