Oil yield optimization from co-pyrolysis of low-density polyethylene (LDPE), polystyrene (PS) and polyethylene terephthalate (PET) using simplex lattice mixture design

Abstract

In this study, a novel approach to optimization of oil yield from the co-pyrolysis of Low-density Polyethylene (LDPE), Polystyrene (PS) and Polyethylene Terephthalate (PET) was investigated at 450 °C and residence time of 90 min. Simplex lattice mixture design (SLMD) was applied to investigate the oil recovery process to optimize the mixture compositions for maximum oil yield and to observe the blending behavior of the three plastic samples in relation to oil yield. Analysis of variance (ANOVA) showed the model generated was significant with a p-value <0.0001, R2 value of 0.9698, adjusted R2 of 0.9482 and predicted R2 of 0.9038. The model in terms of actual components, shows that the components LDPE, PS and PET have relative impacts of 31.18, 43.77 and 1.99, respectively on oil recovery. Non-linear blending LDPE × PET has a negative impact of 30.13, while LDPE × PS and PS × PET have positive impacts of 57.76 and 7.81, respectively on oil yield. The optimum mixture composition for the oil yield was 32.3% LDPE, 67.7% PS and 0% PET. The highest percent feedstock conversion of 99.9% was attained with mixture ratio 0.00 LDPE:1.00PS:0.00PET, while the lowest feedstock conversion of 86.90% was achieved with the mixture ratio 00.00 LDPE:0.00PS:1.00PET.