Determination of coal reactivity during coprocessing using stable isotope mass spectrometry

The 13C12C ratios of fractions with different functionality (saturates, aromatics, polar aromatics and asphaltenes) separated during mild coal-oil coprocessing runs have been determined by stable isotope ratio mass spectrometry on the CO2 produced by quantitative combustion. The proportions of coal-derived carbon in the different fractions can be determined from the difference in natural abundance of 13C between the coal and oil starting materials. The correction of the data for isotope-selective effects between different fractions (based on data from oil-only runs) is discussed. The corrected data support a complex model for the mechanism of coal dissolution, with interactions between the coal reactant and all of the fractions of the soluble run product, together with retrograde reactions incorporating oil-derived carbon into the insoluble coke product.