Segmented catalytic co-pyrolysis of biomass and high-density polyethylene for aromatics production with MgCl2 and HZSM-5

[Display omitted] •The Diels-Alder reaction was used for aromatics production during the segmented co-pyrolysis of biomass and HDPE.•High selectivity of aromatics (95.9%) bio-oil was obtained.•The synergistic effect was promoted by using MgCl2 and HZSM-5 in the segmented co-pyrolysis of biomass and HDPE. For the catalytic co-pyrolysis of glucose and high-density polyethylene (HDPE) in a fixed-bed reactor, the effects of different layout schemes of feedstock and catalysts on bio-oil yield and aromatics selectivity were investigated based on the Diels-Alder reaction of furans and short-chain olefins on HZSM-5 for aromatics production. Experimental results showed that the arrangement (HDPE/HZSM-5/glucose/HZSM-5) had advantages on bio-oil yield and aromatics selectivity. A mixture of pine sawdust and MgCl2 as a glucose substitute that provided furan compounds (Furfural) reacted with short-chain olefins for aromatics production. We found that acquiring high selectivity of aromatic bio-oil from the catalytic co-pyrolysis of pine sawdust and HDPE with MgCl2 and HZSM-5 is feasible. The effects of co-pyrolysis temperature, biomass to HDPE ratio, and feedstock to catalyst ratio on bio-oil yield and chemical compositions were discussed. Notably, an appropriate ratio between the amounts of furans and short-chain olefins is necessary for increasing bio-oil yield and aromatics selectivity. Maximum oil phase product yield of 20.6% and aromatics selectivity (area %) of 95.9% were obtained when pyrolysis temperature, biomass to HDPE ratio, and feedstock to catalyst ratio were 600 ℃, 1:2, and 1:1, respectively.