James A. Franz

13C, 2H, 1H n.m.r. and gpc study of structural evolution of a subbituminous coal during treatment with tetralin at 427 °C

Abstract Subbituminous Kaiparowitz coal was treated with 1,1-d2-tetralin or tetralin in sealed tubes at 427 °C and 500 °C for varying periods of time and rates of temperature rise (15 °C/s, 3 °C/s, and 1 °C/s). The time dependence of yields, average molecular weights, molecular-weight distributions and changes in hydroxyl-group content and elemental composition were determined. Deuterium FT n.m.r. was used to monitor the incorporation of deuterium from 1,1-dideuteriotetralin into aliphatic and aromatic structures in the fractionated products. The exchange of 2H with phenol in the presence of the coal was examined to aid in the interpretation of 2H n.m.r. results. 13C and 1H FT n.m.r. and i.r. spectroscopy were used to monitor the fractionated products over time. The ultimate obtainable yields of THF-soluble product were not significantly altered by the shorter temperature-rise times. The highoxygen-containing subbituminous coal undergoes an extremely rapid loss of about 20% of its oxygen by dehydration, and was found to enhance the rate of reduction of acetophenone and the scrambling of deuterium label in tetralin. The growth of benzylic aliphatic hydrogen at the expense of β (ArCH2C H 2) hydrogen was rapid in the early stages of reaction. In spite of apparently labile aliphatic structures, the preasphaltenes exhibited products above MW 1200 that were stable for more than 2 h at 500 °C.

Origin of certain heterocyclic compounds from depolymerization of lignite

Abstract The origins of products observed in the acid-catalysed phenolic depolymerization of a lignite are discussed. The isolation of 14C-labelled xanthene and 9-arylxanthenes from the use of 1-14C-phenol in lignite depolymerization reactions demonstrates the solvent origins of aromatic portions of these products. Methylene-, methine-, and ethylene-bridged aromatic products were identified by gas chromatography—mass spectrometry (GCMS) techniques, demonstrating a close similarity to products from the depolymerization of brown coals and lignites. Reactions of model triarylmethane compounds under depolymerization conditions demonstrated the facile conversion of triarylmethine structures to diarylmethane structures, indicating ambiguity in the simple interpretation of diarylmethane products as having derived from diarylmethane functional groups in coal. Alternative mechanistic pathways to observed products are presented.