Biomass:polystyrene co-pyrolysis coupled with metal-modified zeolite catalysis for liquid fuel and chemical production

Biomass and waste polystyrene plastic (ratio 1:1) were co-pyrolysed followed by catalysis in a two-stage fixed bed reactor system to produce upgraded bio-oils for production of liquid fuel and aromatic chemicals. The catalysts investigated were ZSM-5 impregnated with different metals, Ga, Co, Cu, Fe and Ni to determine their influence on bio-oil upgrading. The results showed that the different added metals had a different impact on the yield and composition of the product oils and gases. Deoxygenation of the bio-oils was mainly via formation of CO2 and CO via decarboxylation and decarbonylation with the Ni–ZSM-5 and Co–ZSM-5 catalysts whereas higher water yield and lower CO2 and CO was obtained with the ZSM-5, Ga–ZSM-5, Cu–ZSM-5 and Fe–ZSM-5 catalysts suggesting hydrodeoxygenation was dominant. Compared to the unmodified ZSM-5, the yield of single-ring aromatic compounds in the product oil was increased for the Co–ZSM-5, Cu–ZSM-5, Fe–ZSM-5 and Ni–ZSM-5 catalysts. However, for the Ga–ZSM-5 catalyst, single-ring aromatic compounds were reduced, but the highest yield of polycyclic aromatic hydrocarbons was produced. A higher biomass to polystyrene ratio (4:1) resulted in a markedly lower oil yield with a consequent increased yield of gas.