Liquefaction of waste tires by pyrolysis for oil and chemicals—A review

• Progress in waste tire pyrolysis for fuels and chemicals.
• Oil yields with temperature variation and type of reactor operation.
• Effect of catalysts, co-pyrolysis and other pyrolysis methods on oil compositions.
• Pyrolytic oil upgrading for direct applications

This article provides a critical review of past efforts over the last four decades in oil and liquids production from the pyrolysis of waste tires. Experimental lab-scale and pilot-scale results from the pyrolysis of scrap tires are included here. The various operating conditions under which pyrolysis of waste tires is carried out are reviewed. In addition to reactor conditions such as temperature and heating rates, other aspects of the tire pyrolysis such as catalyst type, catalyst preparation, and their effects on oil yields are also reviewed. Pyrolytic oil characteristics such as heating value, sulfur content and density are summarized. The various issues with production of oil from tire pyrolysis such as sulfur content, gaseous combustion emissions, naphtha composition are also discussed in the review. Various methods for the analysis of the pyrolytic oil composition and its refining to produce valuable products are evaluated. The review revealed that the pyrolytic oil could yield useful chemicals such as the aromatic benzene and limonene, in addition to fuel applications, depending on the type of waste tires pyrolyzed and the operating conditions of the pyrolysis process.