Characterization and upgradation of crude tire pyrolysis oil (CTPO) obtained from a rotating autoclave reactor

Many of the inferior fuel properties of crude tire pyrolysis oil (CTPO) can be attributed to the presence of polar organic compounds such as various oxygenates, nitrogen heterocycles and sulfur-containing compounds. An efficient, straightforward and scalable pathway of removing the polar fraction from CTPO is crucial in improving its fuel properties. In this work, CTPO produced by thermal pyrolysis (400 degrees C, 0.2 bar, 4 rpm, 5 h) of scrap automotive tires in a rotating autoclave reactor (8-tons) has been upgraded using silica gel (60-120 mesh) as adsorbent and petroleum ether as diluent. In two different strategies, CTPO was first diluted with petroleum ether and (1) passed through a column of silica gel (CoTPO) or (2) mechanically stirred with silica gel (StTPO) followed by solvent evaporation to afford upgraded oil. Both crude and upgraded TPO samples were extensively analyzed for chemical composition and fuel properties and compared with each other. Analytical techniques like GC-MS, H-1 NMR, FTIR, and elemental analysis showed significantly less polar fractions in CoTPO and StTPO compared to CTPO. The cetane index of CoTPO and StTPO were found to be 35 and 40, respectively compared to 33 in CTPO. Sulfur content decreased by 19% and 34% in CoTPO and StTPO, respectively. The acid value of CoTPO and StTPO were found to be 0.8 and 0.6 compared to 12.2 in CTPO. The TGA data showed better thermal stability of upgraded oil samples. StTPO showed better chemical composition and fuel properties compared to CoTPO that can be explained by its longer contact time with silica gel adsorbent.