Production of diesel-like fuel by co-pyrolysis of waste lubricating oil and waste cooking oil

The co-pyrolysis of waste lubricating oil and waste cooking oil was carried out with various blend compositions at 450 °C, 3 kW, and 5 min of residence time in a stainless steel reactor. The fraction within the boiling range of diesel fuel, referred to as diesel-like oil, was separated from the pyrolytic oil using ASTM D-86 distillation. Properties of the products were evaluated and compared to the standard properties of petro-diesel as required by ASTM standards and Oil and Gas Regulation Authority (OGRA) standards followed by oil refineries in Pakistan. Results showed that the fraction of diesel-like oil increases, and its final boiling point decreases with the increasing composition of waste cooking oil. It was observed that the maximum yield of pyrolytic oil and a maximum fraction of diesel-like oil were 73 wt.% and 84.5 vol.%, respectively. It was also observed that most of the properties of pyrolytic and diesel-like oils obtained from the blends containing 50% or less waste cooking oil by volume were close to the commercial diesel. This research resulted in converting two environmentally hazardous waste materials in a single facility to produce fuel. The sulfur content of the fuel was lower as compared to the fuel obtained by waste lubricating oil alone, reducing the environmental hazard. The pour point of the fuel was lower than the fuel obtained by waste cooking oil alone, making fuel fit for use in cold weather. This research provided the basis for an economically sound co-pyrolysis facility of waste oils.