Pyrolysis of Waste Tires in a Fixed Bed Reactor: Influence of Additive on Sulfur Content in Pyrolysis Oil

In this study, pyrolysis of waste tires and waste polypropylene/waste polyethylene mixtures was carried out in a fixed bed reactor at reaction temperatures ranging from 550 to 560 ℃. The objective was to investigate the changes in the properties of the resulting pyrolysis oil, with particular emphasis on the effect of the CaO additive on the sulfur content. The sulfur content in the pyrolysis oil derived from a single waste tire sample was found to be about 1 wt%. To effectively reduce sulfur content, waste polypropylene and waste polyethylene were mixed in a 1:1 weight ratio. When the pyrolysis of the mixed waste tire and waste polypropylene samples was conducted with CaO, the sulfur content in the pyrolysis oil was reduced to a maximum of about 0.4 wt%. This indicates an about 80% reduction compared to the sulfur content in the original waste tire feedstock (2.3 wt%). GC-MS analysis revealed that with increasing reaction temperature, the proportion of aliphatic compounds decreased while the proportion of aromatic compounds increased. The primary compounds detected included limonene, xylene, styrene, and toluene, with trace amounts of sulfur and nitrogen compounds also identified.