Variations in organic oxygen structures in the Argonne premium coals as a function of rank

摘要

It has been found that MS and NMR results on oxygenated species in coal correlate quite nicely. As expected, from previous studies, structures related to lignin dominate in the lower rank coals. However, benzofurans and dibenzofurans make an important contribution to the overall distribution. Singly and multiply hydroxylated benzene rings are the major oxygen structures in the low rank coals. In addition, carboxylic acids are quite abundant. In the bituminous coals, carboxylic acids are absent and multiple hydroxylated aromatic compounds become only minor contributors to the overall distribution. More furan containing aromatics are seen. In the higher rank lv and mv bituminous coals, hydroxy aromatic compounds are minor constituents and large annulated benzofurans dominate. The relative contribution from ethers is still uncertain and is currently being investigated. Overall, it appears that a dominant mechanism for oxygen loss during coalification is the coupling of phenolic species to form furan structures resulting in the loss of water (Scheme 1). These furans are expected to be stable under these conditions and remain intact as coal liquefaction proceeds.