Application of used engine oil as a hydrogen-rich substance in co-pyrolysis with pine wood for reduction its environmental hazards and produced diesel-like fuel: Thermal behavior, kinetic and thermodynamic analysis

Abstract

This study introduced co-pyrolysis process as effective way for convert used engine oil (UEO) into useful product and reduced its environmentally hazardous. The co-pyrolysis of acid-washed pine wood (APW) and used engine oil was investigated through thermogravimetric analysis (TGA) within the temperature range of 30 to 700 °C, employing heating rates of 5, 10, and 20 °C/min. Among the blends studied, a blend containing an equal ratio of two feeds exhibited the highest synergism. The study of the oil composition obtained from the co-pyrolysis of APW and UEO in the fixed-bed reactor showed that the simultaneous use of UEO as a feedstock reduced the yield of oxygenated compounds from 82.69 % to 25.06 %, while significantly increasing the yield of hydrocarbons from 17.31 % to 74.93 % compared to APW alone. 51.25 % of these hydrocarbons were in the range of diesel fuel. The kinetic parameters were determined using three iso-conversional methods: Kissinger-Akahira-Sunose (KAS), Ozawa-Flynn-Wall (OFW), and Starink. The obtained average activation energy was 162.65, 161.39, and 161.66 kJ/mol for FWO, KAS, and Starink, respectively. The pre-exponential factors, determined by the Kissinger method, varied from 1.98 × 108 to 9.12 × 1018. Also, the use of master plots in combination with iso-conversional methods showed that the reaction order model, f(α)= (1-α)n, with n between 2 and 3, provides the best description for the co-pyrolysis of APW and UEO in the applied heating rate range. Furthermore, with increasing conversion from 0.2 to 0.8, the thermodynamic parameters including ΔH, ΔG, and ΔS, changed in the range of 125.09–234.59 KJ/mol, 159.02–155.92 KJ/mol, and −0.06 to 0.13 KJ/mol, respectively.