THERMAL-CRACKING OF PETROLEUM RESIDUES .2. HYDROGEN-DONOR SOLVENT ADDITION

The thermal cracking of a petroleum vacuum residue mixed with 20 wt% of a hydrogen-donor solvent (dihydrophenanthrene, DHP) was studied within the temperature range 390-450 °C and reaction times up to 4 h. The concentration of three pseudo-components, i.e. vacuum residue, distillate and coke, was observed during conversion and a simple kinetic model of the reaction was proposed. The comparison of these results with corresponding data previously recorded for simple thermal cracking shows that the presence of the donor solvent : 1. (1) decreases the rate of vacuum residue conversion with a particular effect on coke deposition reactions that are strongly inhibited; 2. (2) enhances the maximum distillate production by about 10-15 wt%; 3. (3) allows operation at higher severities while maintaining the visocity of the residual oil (tar) at low values.