Fast pyrolysis of agroindustrial wastes blends: Hydrocarbon production enhancement

Abstract

Fast pyrolysis of waste from agroindustry may be an alternative choice for sustainable use of enhanced biofuels. Plastics are one option for improving the hydrogen to carbon efficiency ratio (H/Ceff) of biomass feedstock. Waste from agroindustry in blends with biomass could modify the reaction mechanism for removing oxygen by substituting decarbonylation and decarboxylation with dehydration. Firstly, fast pyrolysis was performed to find the optimal mass blending ratio for olive pomace (OP) and agroindustrial polymers (polyethylene (PE), polystyrenes (PS) and polyvinyl chloride (PVC)) according to hydrocarbon production. Experimental results for the 1.5:1 OP/PE, 1:1.5 OP/PS and 1:1.5 OP/PVC mass blending ratios at 500 °C, showed synergistic enhancement of hydrocarbon yields. Alkenes yield were enhanced for 1.5:1 OP/PE, where the light hydrocarbons fraction (C6-C10) first increased and then decreased with temperature, reaching a maximum at 650 °C. For 1:1.5 OP/PS and 1:1.5 OP/PVC, it was improved the aromatic compounds formation, being 500 °C and 650 °C the optimal reaction temperature for the former and the later, respectively. Benzene, toluene and xylene were in large quantities obtained for PS and PVC blends with OP. Additionally, the synergistic effect on pyrolysis of the blends did not show any clear trend for pyrolytic gas emissions. In general, as reaction temperature increased, CO and CO2 emissions fell and CH4 was enhanced. Finally, olefin and aromatic yields were promoted for blends with a higher H/Ceff.