Upgrading of pyrolytic lignin fraction of fast pyrolysis oil to hydrocarbon fuels over HZSM-5 in a dual reactor system

Abstract

The catalytic upgrading of pyrolytic lignin (PL) fraction of a fast pyrolysis oil to hydrocarbon fuels was studied over HZSM-5 at atmospheric pressure. The PL fraction was obtained after removing the water-soluble components from the pyrolysis oil. The upgrading was done in a dual reactor system having two catalytic reactors in series. The temperatures in these reactors were in the range 340–400°C (first reactor) and 350–450°C (second reactor). Due to the highly viscous nature of the PL fraction, it was co-processed with tetralin. The objective was to maximize the amount of organic distillate product with a high concentration of aromatic hydrocarbons. The amount of organic distillate in the effluent from the second reactor was between 22–31 wt.% of the PL fraction and contained up to 84 wt.% aromatic hydrocarbons. The gaseous product mainly consisted of CO and CO 2 and amounted to 8–19 wt.% of the PL fraction. Comparison of the results with those from a single reactor system revealed that the dual reactor system was particularly beneficial when the temperature in the first reactor was low. Thus, with the first reactor at 340°C, the aromatic hydrocarbon yield from the dual reactor system was two-fold and the coke plus char yield was 25 wt.% lower than those from the single reactor system at 350°C.