Catalytic Pyrolysis of Polystyrene over Steel Slag under CO2 Environment

Abstract

As the consumption of plastic materials has been dramatically increased, the abundant presence of their debris has become a significant problem worldwide. Thus, this study proposes a sustainable plastic conversion platform for energy recovery. In detail, polystyrene pyrolysis was examined as a case study under CO2 atmosphere in reference to N2 condition. The major gaseous and liquid products from polystyrene pyrolysis include permanent gases (syngas and C1-2 hydrocarbons) and condensable aromatic compounds. Under CO2 environment, the reduction of polycyclic aromatic hydrocarbons (PAHs) was achieved during polystyrene pyrolysis, in comparison with N2 condition. Since its slow reaction kinetics, conversion of condensable hydrocarbons into permanent gases was not fully activated. Therefore, a cheap industrial waste, steel slag (SS), was employed as a catalyst to increase reaction kinetics. The synergistic effects of SS and CO2 contributed to doubling H2 production, while CO formation increased more than 300 times, in reference to non-catalytic pyrolysis. Because CO2 acted as an oxidant for CO production, control of H2/CO ratio was achieved in different conditions. Thus, the utilization of CO2 would suggest a promising way to reduce the formation of PAHs, adopting the reliable platform to produce syngas from plastic waste.