Light oil production from waste tire pyrolysis using nobel metal-supported catalysts

Abstract

The influences of pyrolysis conditions, i.e. pyrolysis temperatures, catalyst temperatures were investigated on the catalytic pyrolysis of waste tire. For the influences of catalysts, the studied parameters were metallic nature, metal particle size, metal loading, the amount of catalyst, and the addition of a second metal. Particular focus was placed on the reduction of poly- and polar-aromatics and consequent increase of light oil production. Increasing pyrolysis temperature increased the content of polar-aromatic in the tire-derived oil. Based on experimental results and various evidences, a set of possible pathways for polar-aromatic formation was proposed. The use of noble metals (Pt, Rh, Re, and Ru)-supported catalysts led to a drastic reduction in poly- and polar-aromatics together with an increment in light oil selectivity. Among the studied noble metals, Ru was the most active one due to its intrinsic nature that has both a high hydrogenation activity and its low heat capacity constant. Subsequently, the roles of ruthenium and its particle size were elucidated. Ruthenium clusters were found to be the active sites for poly and polar-aromatic reduction. And, the activity increased with decreasing ruthenium particle size (from 4.5nm to 2.5nm). Increasing ruthenium loading (up to 2%wt) while maintaining its dispersion could dramatically enhance light oil production as well as poly- and polar-aromatic reduction activities of Ru-based catalysts. Finally, synergistic effects on aromatic reduction and consequent increase in light oil production were observed on RuNi/HMOR catalysts. And, the synergy was strongly dependent on the catalyst composition, i.e. Ru/(Ru+Ni) ratio.