A study of hexane/toluene extraction of fossil resin types from the Utah Wasatch Plateau coal

Abstract

Four fossil resin types from the Wasatch Plateau coal field of central Utah were distinguished by their colour—yellow, amber, light-brown and dark brown—and were physically isolated by hand sorting. These resin types were subjected to physical/chemical characterization, petrographic examination, and hexane/toluene extraction. The solvent extracted fractions were then subjected to pyrolysis gas chromatography/electron impact mass spectrometry analysis and FT-i.r. spectroscopic examination. The extraction rate by both hexane and toluene follows the order: yellow > amber > light brown > dark brown. These resins were found to be composed mainly of aliphatic components, partially aromatized multicyclic terpenoids and a few oxygen functional groups (mostly -COOH) with molecular weight and aromaticity increasing in the following order: yellow resin < amber resin < light brown resin < dark brown resin. Hexane-purified resin from these four resin types closely resembles the properties of physically separated yellow resin which is of significant value in the printing ink industry. The nature of the resinite coloration is discussed, based on the experimental results.