Comparison of the Quaternary Aromatic Carbon Contents of a Coal, a Coal Extract, and Its Hydrocracking Products by NMR Methods

Samples of a coal extract and its hydrocracked products have been examined by solution-state and solid-state NMR spectroscopy to establish if these methods could follow the reaction process that is expected to convert bridgehead C atoms into hydrogen-substituted C atoms. The changes have also been followed by size-exclusion chromatography (SEC), elemental analysis, basic −OH titration, and UV-fluorescence spectroscopy. NMR spectra in CDCl3 indicated that the products contained more bridgehead C atoms than the extract. Spectra obtained using a better solvent, 1-methyl-2-pyrrolidinone (NMP), did indicate that the extract contained more bridgehead C atoms than the products. The basic −OH measurement indicated rapid removal of the group by hydrocracking; however, this was a relatively minor correction to the overall quaternary carbon concentration. The evidence from SEC and UV-fluorescence suggested that the large molecules that were indicated to be present in the coal extract and the products did not give go...