Catalytic fast pyrolysis of low density polyethylene into naphtha with high selectivity by dual-catalyst tandem catalysis.

In this work, catalytic fast pyrolysis of low density polyethylene (LDPE) into highly valuable naphtha by the relay catalysis (Al2O3 followed by ZSM-5 zeolite) was conducted. Effects of different catalysts, pyrolysis temperatures, catalyst to plastic ratio, and Al2O3 to ZSM-5 ratio, on product distribution and selectivity were studied. Al2O3 shows an excellent performance for catalytic reforming of LDPE pyrolysis vapors, mainly producing C5-C23 olefins that are the important precursors to form aromatics via Diels-Alder, aromatization, and polymerization reactions in the pores of ZSM-5 catalyst. Experimental results also show that the selectivity of monoaromatics and C5-C12 alkanes/olefins can be up to 100% over Al2O3 followed by ZSM-5 relay catalysis at the temperature of 550 °C, the catalyst to plastic ratio of 4:1, and Al2O3 to ZSM-5 ratio of 1:1. The product (monoaromatics and C5-C12 alkanes/olefins), naphtha, could be a renewable feedstock for new plastic production in the petroleum industry so that this finding might provide a new insight for a circular economy.