Catalysis Today, Vol.43, No.3-4, 241-247, 1998
Depolymerization and demetallation treatments of asphaltene in vacuum residue
The asphaltene fraction [hexane insoluble (HI)] of a vacuum residue (VR) was treated under ultrasonic irradiation at 40 degrees C in THF or 150 degrees C in 1-methyl naphthalene (1-MN) in the presence of an adsorbent composed of modified macro-reticular polystyrene resin. Such a treatment was found effective to convert the asphaltene into the hexane soluble (HS : maltene) without any hydrogen consumption. 61 and 72% of the HI was converted by the adsorption treatment at 40 degrees C in THF and 150 degrees C in 1-MN, respectively, to HS materials havings lower molecular weights. About 65% of the metal contaminants in the original asphaltene remained with the newly formed maltenes after this treatment. Structural analyses of the asphaltene and maltene fractions before and after the treatment suggests decoagulation and/or depolymerization of the asphaltene into maltene, while the porphyrin moiety becomes soluble, being transformed to the maltene fraction. The roles of polar solvent, ultrasonic irradiation, and adsorbent are discussed based on the above results.