Effect of petroleum feedstock and reaction conditions on the structure of coal-petroleum co-cokes and heat-treated products

Bituminous coal/petroleum co-cokes were produced by coking 4:1 blends of vacuum resid (VR)/coal and decant oil (DO)/coal at temperatures of 465 and 500 °C for reaction times of 12 and 18 h, under autogenous pressure in microautoclave reactors. Co-cokes were calcined at 1420 °C and graphitized at 3000 °C for 24 h. Optical microscopy, surface area measurements, X-ray diffraction, temperature-programmed oxidation, and Raman spectroscopy were used to characterize the products. Product yield distribution analysis suggested an increase in co-coke yield as reaction severity index increases, although the increase yield is small at higher index values. It was found that higher reaction temperature (500 °C) or shorter reaction time (12 h) leads to an increase in the amount of mosaic carbon at the expense of textural components necessary for the formation of anisotropic structure, namely, domains and flow domains in the co-coke texture. Characterization of graphitized co-cokes showed that the quality, as expressed by the degree of graphitization, crystallite dimensions, Raman disorder parameter, and oxidation reactivity temperature of the final product, is dependent on the nature of the precursor co-coke, with products obtained from co-cokes produced at 500 °C showing a higher structural disorder than the corresponding products produced at 465 °C. The products obtained from DO/coal blend also displayed better structural order than products derived from VR/coal.