Catalytic cracking reaction of used lubricating oil to liquid fuels catalyzed by sulfated zirconia

The conversion of used lubricating oil to transport fuel by direct cracking is a suitable way to dispose of waste oil. The aim of this research was to study the catalytic cracking of used lubricating oil, and thus change its classification from a waste produce to a liquid fuel as a new alternative for the replacement of petroleum fuels. The experiments were carried out in a 70-cm³ batch microreactor at a temperature of 648-698 K, initial hydrogen pressure of 1-4 MPa, and reaction time of 10-90 min over sulfated zirconia as a catalyst. The conditions that gave the highest conversion of naphtha (~20.60%) were a temperature of 698 K, a hydrogen pressure of 2 MPa, and a reaction time of 60 min, whereas, under the same conditions, kerosene, light gas oil, gas oil, long residues, hydrocarbon gases, and a small amounts of solids were present (~9.04%, 15.61%, 5.00%, 23.30%, 25.58%, and 0.87%, respectively). The liquid product consisted of C₇-C₁₅ of n-paraffins, C₇-C₉ of branched chain paraffin and aromatic compounds such as toluene, ethylbenzene and xylene. The kinetic study reveals that the catalytic cracking of waste lubricating oil follows a second order reaction, and the kinetic model is defined as k(s⁻¹)=2.88×10⁴exp[−(103.68 kJmol⁻¹)/(RT)].