Utilization of waste tire pyrolysis oils for the production of special oil products

The best solution for environmentally friendly recycling of used tires is the pyrolysis of waste tires. Pyrolysis is a thermal process, what takes place in an oxygen-free environment at high temperature (usually 400-1000 °C), producing pyrolysis gas, pyrolysis oil and solid products (coke, carbon black) from tire waste. Tire pyrolysis oil is a dark brown/black liquid and its economic use is unsolved. The pyrolysis oil is a mixture of various hydrocarbons with carbon atoms of C5-C20: paraffins, olefins, diolefins, (poly) aromatic hydrocarbons and monoterpenes.

The most appropriate way to utilize the tire pyrolysis oil is to separate the gasoline and diesel fractions by distillation, what are suitable for the production of the most valuable products applying catalytic hydrogenation.

In the industry cobalt or nickel-promoted, sulfided molybdenum or tungsten-containing catalysts are used for catalytic hydrodesulphurization of oils containing sulphur. Oxide-form of NiMo/Al2O3 catalysts are usually produced by impregnating γ-Al2O3 support by aqueous solutions of Ni and Mo-containing compounds. After impregnation the catalysts are dried and then calcined. After calcination, the oxide form catalysts must be activated by sulfidation in the presence of H2/H2S gas mixture stream or in a liquid phase containing an organic sulfur compound at a temperature of 300-400°C. Sulfided NiMo/Al2O3 catalysts are generally used at temperatures of 350°C or higher to stabilize the pyrolysis oils. A commercial NiMo/Al2O3 catalyst and a self-made CoMo/Al2O3 catalyst were used for the hydrogenation/desulfurization of pyrolysis oils.

X-ray Photoelectron Spectroscopy (XPS) analytical method detected fluorine on the surface of the used, deactivated catalysts. The halogen content of the pyrolysis oil and the catalysts was determined by quantitative ICP-MS measurements. The great importance of discovering the halogen content of pyrolysis oils must be emphasized and it follows that the pyrolysis oils should be dehalogenated before catalytic hydrogenation/desulfurization.

The Palota Environmental Protection Ltd. proved through experiments, with the microreactor system, what was developed for treating waste tire pyrolysis oils for the production of special oil products on the basis of pyrolysis oil is feasible and can be solved on an industrial scale too. This is a new trend in the utilization of tire pyrolysis oils in an international context. At the same time, the first experiments also revealed a number of problems, that needed to be solved. The HUN-REN Centre for Energy Research was also involved to solve some of these problems. 

95-98% reduction of sulfur and olefin content was achieved at the preliminary experiments, but it will be important to carry out further experiments to optimize dehalogenation, to deal with sedimentation problems, and in connection with further developments in technology and control. Our development goals are aimed at developing a more complex, multi-reactor system.