Influence of process conditions on the formation of 2-4 ring polycyclic aromatic hydrocarbons from the pyrolysis of polyvinyl chloride

Municipal solid waste (MSW) contains significant amounts of polyvinyl chloride (PVC). The reactivity of PVC may form polycyclic aromatic hydrocarbons (PAHs) during the pyrolysis of MSW, which can become a key challenge during the development of pyrolysis technologies. However, there is very limited work in relation to the influence of pyrolysis process conditions in terms of temperature and heating rate on PAHs formation during pyrolysis of PVC. In this work, the formation of 2-4-ring PAHs from the pyrolysis of PVC at temperatures of 500, 600, 700, 800, or 900°C and at fast and slow heating rates was investigated under a N₂ atmosphere in a fixed bed reactor. With the increase of temperature from 500 to 900°C, HCl yield decreased from 54.7 to 30.2 wt.%, while the yields of gases and PAHs in the tar increased. Slow pyrolysis generated higher HCl yield, and lower gas and tar yield than fast pyrolysis; the PAH yield obtained from the slow pyrolysis was much lower compared to fast pyrolysis. The results suggest that for fast pyrolysis, the dehydrochlorination of the PVC might be incomplete, resulting in the formation of chlorinated aromatic compounds.