Molecular Profile, Fuel Properties, Engine Performance and Emission Characteristics of Gasoline-Like Fuel Produced Via Cracking of Used Engine Oil Using Na-Fe3O4/HZSM-5 Catalyst

Abstract

A vast quantity of used engine oil (UEO) is generated every day and poses a major disposal issue in modern society due to the heavy metals and other hazardous contaminants present in it. Due to its high carbon content, UEO has great potential to be utilized as a feedstock for fuel production via thermo-catalytic processes. The studies on the molecular profile, fuel properties, engine performance, and emission characteristics of gasoline-like fuel produced via cracking of used engine oil were conducted. The Fe₃O₄ nanoparticles was synthesized via the one-spot method using iron (III) chloride hexahydrate (FeCl₃.6H₂O) and iron (II) chloride tetrahydrate (FeCl₂.4H₂O) as precursors, while the HZSM-5 was synthesized using Al₂(SO₄)₃.18H₂O and Na₂SiO₃ as sources of alumina and silica, respectively. The UEO was cracked in a fixed stainless-steel batch reactor for 1h at varying temperature (350 – 450 ⁰C). The liquid fuel product obtained was analysed for its molecular composition using GC-MS and FTIR. ASTM standard procedure was used to determine the fuel properties while the engine performance and emission characteristics test were carried out on a four stroke, single cylinder, carbureted, spark ignition (SI) engine. The results showed that the catalyst is 97.60% selective for gasoline range hydrocarbons, which could be attributed to the high surface area of HZSM-5, which offers more active sites for catalytic cracking. The fuel properties of the produced liquid fuel determined include specific gravity (0.76), kinematic viscosity (1.69 mm²/Sec), flash point (-42 °C), auto ignition temperature (225 °C), carbon residue (0.12%), lower heating value (40,443 KJ/kg), and octane number (94). The engine performance test results using the produced liquid fuel were comparable to those of commercially available gasoline. However, the emissions of CO, CO₂, and unburnt hydrocarbons were higher than those of commercially available gasoline. Based on the results obtained, it was concluded that the fuel obtained could be used directly or as a blend in spark-ignition engines without any negative impact on engine performance.