VISBREAKING OF AN ASPHALTENIC COAL RESIDUE

A residue from deasphalting of liquids obtained by direct liquefaction of a Spanish subbituminous coal was processed by thermal treatment. This residue is rich in asphaltenes which do not undergo cracking easily and are coke precursors in thermal cracking. The kinetics of the cracking and coke formation reactions were studied and the viscosity, coke content, boiling point distribution, elemental analysis and aromaticity of the reaction products were determined. The experimental data fit the first-order kinetic model proposed. The main effects produced by the thermal treatment were a large decrease in the viscosity from 4608 mm(2) s(-1) for the feedstock to 939 mm(2) s(-1) for the product. The conversion of the heavy fraction (b.p. > 350 degrees C and soluble in toluene) increased with the temperature and residence time, the conversion to coke being higher than the conversion to light products (b.p. <350 degrees C and soluble in toluene).