An experimental investigation into the formation of polycyclic-aromatic hydrocarbons (PAH) from pyrolysis of biomass materials

The formation of polycyclic-aromatic hydrocarbons (PAH) from the pyrolysis of cellulose, pectin, and chlorogenic acid was studied. The primary product, mostly primary volatile tar, was exposed to a higher thermal severity, i.e. high temperatures and long residence times. The reactor setup consisted of a quartz tube with two zones, zone I and II, each heated and controlled separately. Zone I was used to first pyrolyze the substrate at 300°C to produce a low temperature tar (LTT) as well as to pyrolyze the product char at 600°C to produce a high temperature tar (HTT). The LTT and HTT were then subjected to a high thermal severity in the second zone (zone II) where the temperature was varied between 700 and 850°C. The residence time of the volatiles in zone II was varied between ca. 90 and 1400 ms (calculated at 800°C). The results showed that the yield of most PAHs increased with temperature, except in a few cases where the yield of two- and three-ring PAHs exhibited a maximum. PAHs yields also generally increased as the residence time was increased from 90 to 1400 ms at 800°C.