Investigation of mechanisms of polycyclic aromatic hydrocarbons (PAHs) initiated from the thermal degradation of styrene butadiene rubber (SBR) in N2 atmosphere

This study has been carried out to characterize the thermal decomposition of styrene-butadiene rubber (SBR), using thermo-gravimetric analysis (TGA) coupled to online GC/MS, and to investigate the formation and ultimate fate of chemical species produced during gasification of SBR. A preliminary mechanistic understanding has been developed to explain the formation and relationship of light hydrocarbons (C-1-C-4), substituted aromatics, and polycyclic aromatic hydrocarbons (PAHs) during the decomposition of SBR in a N-2 atmosphere. Identification and absolute concentrations of over 50 major and minor species (from hydrogen to benzo[ghi]perylene) have been established, and the measurements have been carried out between 300 and 500 at 10 degrees C/min heating rate in a N-2 atmosphere. The concentration of styrene reached 120 PPMV and the concentration of other substituted aromatics, such as toluene and ethyl benzene reached 20 and 5 PPMV, respectively. These measurements indicate PAH formation at a relatively lower temperature as compared to conventional fuel, such as coal and diesel. The PAH sequence is not simply the constructing of larger PAHs from smaller ones to achieve the complex polymer structures. It is possible to generate large PAH molecules while circumventing the typical construction pathway.