Modifying activities of petroleum pitches and up-graded pitches in the co-carbonization with a range of coals have been examined with the object of proposing an effective co-carbonization process for blast-furnace coke production. Up-grading of additives was attempted using thermal, acidic and oxidative reactions. Acidic reactions with aluminium chloride were most effective with lighter petroleum residues of initially poor modifying activity, this being attributed to dealkylation, ring-closure and ring condensation reactions. The relation between modifying activity and structural indices is discussed. The aromaticity (fa) and the naphthenic ring number in the unit structure Tn,us can be used as appropriate parameters for the activity when the coking yield is taken into account.
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