Influence of the Process Conditions on Yield, Composition, and Properties of the Products Derived from the Thermolysis of Scrap Tire and Used Engine Oil Blends

The thermolysis of waste blends, consisting of shredded scrap tires and used motor oil, was carried out in a semicontinuous distillation reactor. The aim of this research was to investigate the influence of mixture composition, feedstock chopping degree, and pressure on the yield, composition, and properties of thermolysis products, i.e., oil, char, and gas. The distribution of the thermolysis products derived from Tire/Oil (T/O) mixtures was 44.8–60.2% (w/w) of liquid, 22.1–31.6% (w/w) of char, and 17.6–24.6% (w/w) of gas. The highest yield, 60.2% (w/w), of desired product (oil) was obtained from the finer feedstock (Type 1), which was mixed with engine oil in the ratio of 2:2 and thermolyzed at elevated pressure (40 bar). The results of the chemical composition of liquid thermolysis products revealed three dominant classes of hydrocarbons: arenes (21.84–34.48%, w/w), alkenes (21.06–34.54%, w/w), and alkanes (18.36–38.66%, w/w). The liquid products derived from Tire/Oil mixtures can be used as liquid fuels due to their high heating value (41–45 MJ/kg), low ash (0.01–0.11%, w/w), and sulfur (0.58–0.90%, w/w) content. Besides, 19.0–48.0% (w/w) of such liquids are in easily distillable fractions with a boiling range of 50–200 °C that comprise commercial gasoline, and 41.0–52.0% (w/w) boil at a temperature of 200–360 °C that is a typical range of a diesel fraction. The gaseous thermolysis product of the Tire/Oil mixture is composed of the lightest alkanes (over 41%, v/v), hydrogen (11.84–14.72%, v/v), carbon oxides (over 3.5%, v/v), and butenes (about 4%, v/v) as the main alkenes. The elemental analysis of residual char showed carbon as the main element; however, a significant share (13.4–19.8%, w/w) is taken by inorganic impurities. The average calorific value of the thermolysis char is 31 MJ/kg. This work could be considered as a contribution for strengthening and encouraging the blends of waste tires and used oil thermolysis for the production of liquid fuels, which could be used in industrial furnaces or can be refined as a crude oil for manufacture of conventional petroleum fuels and chemicals.