Thermal cracking of C5-deasphalted oil (C5-DAO) was performed in a batch reactor at 410 degrees C in the absence and presence of H2 gas and catalysts. Coke was formed during the thermal cracking of C5-DAO even though the feed contained no asphaltenes. Although H2 suppressed asphaltene formation and decreased the coke yield, coke was still formed in the absence of a catalyst. A slurry-phase dispersed catalyst inhibited the transformation of resins into heavier fractions and facilitated <1 wt % asphaltene yield with no coke formation even under high conversion conditions. The main function of the catalyst was the facilitation of hydrogenation reactions and the stabilization of free radicals, leading to liquid production by inhibiting coke formation. Consequently, the product quality, in terms of hydrogen to carbon ratio and microcarbon residue and S contents, was enhanced by catalytic hydrocracking.