Aromatic hydrocarbons production and synergistic effect of plastics and biomass via one-pot catalytic co-hydropyrolysis on HZSM-5

Abstract

The catalytic co-hydropyrolysis of pine sawdust (PW) and high density polyethylene (HDPE) to selectively produce aromatic hydrocarbons was studied by optimizing reaction parameters (feedstock composition, reaction temperature, residue time, initial hydrogen pressure and catalyst to reactant ratio). The composition of feedstocks, reaction temperature and the ratio of catalyst to reactant all had significant effects on the content of aromatic hydrocarbons, and the appropriate reaction parameters were selected to maximize the yield of aromatic hydrocarbons. The maximum aromatic hydrocarbons yield (18.3 %) and the highest selectively (67.8 %) were obtained when the ratio of plastic to reactant was 0.6, 400 °C, 1.5 MPa for 1 h and the catalyst to reactant ratio was 0.2. Compared with hydropyrolysis of biomass, the addition of plastics reduced the yield of solid residue and the oxygen content in bio-oil. Characteristic analysis of bio-oil showed that that monocyclic aromatic hydrocarbons accounted for the majority of aromatic hydrocarbons in blends, with benzene, toluene, xylene (BTX) having the highest selectivity (51.6–70.6 %), and oxygenates were almost absent in bio-oil. Meanwhile, the possible reaction pathways in the co-hydropyrolysis of biomass and plastic for aromatic hydrocarbons were discussed extensively.