INVESTIGATION OF COKING PROPENSITY OF NARROW CUT FRACTIONS FROM ATHABASCA BITUMEN USING HOT-STAGE MICROSCOPY

The incipient mesophase formation of 10 narrow cut fractions from Atha basca bitumen vacuum bottoms boiling above 525 degrees C (pitch) deriv ed by supercritical fluid extraction (extraction) using pentane was pe rformed using hot-stage microscopy. The experiments were performed in a stream of hydrogen at 750 psi (5.2 MPa) and 440 degrees C. The forma tion of mesophase for these pitch fractions correlated with their macr omolecular carbon residue, molecular weight, and aromaticity. The high er the values of these properties, the sooner the mesophase appeared. The time for the mesophase formation was the shortest in a pitch fract ion containing 88 wt % asphaltenes. In cases where the fractions conta ined low boiling point materials, the mesophase appeared significantly sooner than expected. This was rationalized in terms of the induction period where certain fractions of heavy oils, if present, delay mesop hase formation.