Co-carbonization processes of a petroleum asphalt and coal-derived liquids: An approach to co-carbonization compatibility

Mixtures of three principal carbonizing materials (Kafji vacuum asphalt (KF-VR), solvent-refined coal (SRC) and solvent-treated coal (STC)) with five additives (three Ashland petroleum pitches (A240, A200 and A170), quinoline-soluble residue of steam-cracked crude oil (KP-QS) and coal-tar pitch (CTP-ASM)) were co-carbonized and development of optical texture in the resultant cokes was assessed to evaluate the compatibility of the mixtures. CTP-ASM showed the highest compatibility for KF-VR, but failed to modify STC. By contrast, A240 modified KF-VR and STC so that flow texture developed. FT-i.r. spectra of co-carbonization intermediates from STC had absorption bands between 1100-1300 cm^-1 attributable to phenoxyl groups. These were also present in co-carbonizations with CTP-ASM, but were only just apparent in co-carbonizations with A240. Measurement of naphthenic hydrogen, defined as R_nus, during co-carbonization, was consistent with deoxygenation via hydrogen transfer. Thus, the modifying activities of A240 and CTP are differentiated by the availability of transferrable hydrogen. Mechanisms of co-carbonization are discussed.