Structural comparison of coal liquefaction extracts and hydrocracking products

Abstract

This chapter describes the reactivities of coal extracts prepared in a flowing solvent reactor, where products released from coal are continuously removed from the reaction zone by a flow of solvent, allowing suppression of their extra particle secondary reactions. In hydrocracking coal extracts, the conversion of > 450°C fractions to lower boiling material decrease with rank and correlate with increasing elemental carbon contents and the vitrinite reflectances of the original coals. Results from size exclusion chromatography (SEC) shows the largest shifts to smaller molecular masses (MMs) during the hydrocracking of extracts from middle rank coals. The observed progressive decrease of MMs and increase of hydrocracking conversion with increasing reaction time suggests that this method of hydrocracking removes smaller aromatic clusters from large molecules in a gradual step-wise progression rather than in the form of a catastrophic breakdown of large molecular structures. The present hydrocracking process is instrumental in significantly reducing the sizes of polynuclear aromatic ring systems within the extracts during the early stages of the hydrocracking process.