CO-REFINING OF COAL AND PETROLEUM - NEW ANALYTICAL METHODS AND RESULTS

A UK bituminous coal was co-processed with five different petroleum residues, and with hydrotreated feedstocks, in a simulation of the British Coal Corporation's two-stage liquid solvent extraction process. One-stage co-processing in the presence of a catalyst and hydrogen gas was also investigated. The feedstocks and products were analysed by a variety of procedures, some of which were especially devised, e.g. simulated distillation by supercritical fluid chromatography, determination of the functionality of nitrogen and sulphur, and assessment of the contributions of coal and petroleum to the products by stable-isotope mass spectrometry and size-exclusion chromatography. In low-severity co-processing the best yields were found to be associated with the content of n-pentane insoluble (asphaltene) aromatics in the solvent. Single-stage co-processing gave improved yields. Progressive changes in the composition of the solvent during recycle were identified. No changes in the distribution of nitrogen among different functional groups during co-processing were observed, but the formation of new sulphur groups was observed.