Influence of co-pyrolysis temperature on the characteristics of diesel-like fuel produced from waste frying and engine oils

Global warming and energy crisis have driven the attention of researchers towards conversion of waste materials into valuable products. As compared to the simple pyrolysis, the co-pyrolysis is an environmentally friendly and effective waste conversion process which enhances the yield and properties of the co-pyrolytic fuel. This study explored the effect of temperature (380–450°C, with 10°C difference) on the yield and properties of the co-pyrolytic oil produced from waste frying oil and waste engine oil mixture with 1:1 ratio by volume. The influence of co-pyrolysis temperature on the fractions and properties of the distillate oil within the boiling range of diesel was also analyzed, which was obtained by ASTM D86 distillation of the co-pyrolytic oil. This co-pyrolysis study was conducted in a stainless-steel semi-batch reactor of 1.856-liters capacity. Most of the samples showed that physiochemical properties resembled to that of the commercial diesel, particularly at temperatures above 420°C. Product fuel was characterized by testing commercially important physiochemical properties including pour point, cetane index, API gravity, kinematic viscosity, calorific value, sulfur content and flash point by using test methods set by ASTM standards. Properties of the product fuel were compared to that of the standard specifications for diesel and biodiesel set by ASTM. The highest yield of co-pyrolytic oil (80.1 wt%) and highest fraction of distillate oil (85 vol%) were obtained at 450°C. By comparing with diesel and biodiesel, co-pyrolytic and distillate oils obtained at 450°C showed physiochemical properties resembling closely to the commercial diesel.