Aromatics production from segmented co-pyrolysis of poplar sawdust and high-density polyethylene: Enhancing the synergistic effects

Catalytic co-pyrolysis of biomass and plastic waste is a promising approach for producing renewable biofuels and value-added chemicals. However, because of their different pyrolysis behaviors, the synergy between biomass and plastic is limited, and low-yield aromatics are produced. Herein, a modified segmented catalytic co-pyrolysis technology was proposed, and the effects of pyrolysis parameters were studied in detail to enhance the synergistic effect between feedstocks. For the biomass section (segment 1), catalytic fast pyrolysis (CFP) of poplar sawdust was conducted, and results showed that employing 15 wt% MgCl2 at 500 °C facilitated the production of furans. For the plastic section (segment 2), CFP of high-density polyethylene (HDPE) were performed. It was showed that instead of Y and beta zeolites, the utilization of ZSM-5 as a pyrolysis catalyst with a loading of ZSM-5/HDPE = 1.0, and a temperature of 600 °C was beneficial for the production of short-chain olefins. For the segmented co-pyrolysis of poplar sawdust and HDPE (segment 1 + segment 2), the biomass-to-plastic ratio was crucial in aromatics production. A ratio of 1:1 was found to be most effective in producing MAHs (54.8 area%), which was ∼3.9 or 1.6 times that for the separate CFP of biomass or HDPE. This was also consistent with its higher enhancement factor, confirming that the synergy between poplar sawdust and HDPE was dramatically enhanced. Finally, a segmented catalytic co-pyrolysis reaction pathway was proposed.