Laboratory-scale coking of coal-petroleum mixtures in sealed reactors

Three highly fluid bituminous coals - from the Pittsburgh, Powellton, and Eagle seams - were reacted with atmospheric resid and decant oil in microautoclave reactors under nitrogen at temperatures of 450-500 °C. This exploratory study is the first step in evaluating the prospects for adding coal to delayed cokers to obtain coal-derived components in the liquid product. Subsequent hydrotreating (not studied here) of the liquid would produce a jet fuel with good stability toward pyrolytic decomposition. Coal-derived components appear in the oil fraction from coal-resid reactions at 465 °C. This reaction temperature represents a "coke jump", in which the yield of solid, as a function of temperature, increases dramatically. This behavior is not observed when the individual feedstocks are reacted alone. Further evidence for coal-petroleum interactions in this system is exhibited by the fact that (i) the product slates from the co-coking reactions are not linear combinations of the products from the feedstocks reacted individually and (ii) the fluidity profiles of the Powellton-resid mixtures are similar to those for two interacting coking coals. The effect of changing coal with the same petroleum feedstock is minimal, although the coals are very similar in composition and properties. In contrast, changing from resid to decant oil with the same coal causes major changes in the product slate.