Optimization of combined mixture and process variables for the pyrolysis oil yield from co‐pyrolysis of polymeric wastes

Abstract

The combined mixture process variable approach for optimization and prediction of oil yield in co‐pyrolysis of polymeric wastes was investigated in this study using I‐optimal design. The components mixture investigated were low‐density polyethylene (LDPE), polystyrene (PS), and polyethylene terephthalate (PET), whereas the process variables were temperature and residence time. Thirty experimental runs were developed using the I‐optimality criterion to investigate the effect of interaction between the mixture and process parameters on oil recovery from co‐pyrolysis of the polymeric wastes. The data obtained were used to generate a model equation, and analysis of variance was used to estimate the significance of the model. The model was significant with a P value < 0.0001, the R2 value of 0.9980, adjusted R2 of 0.9949, and predicted R2 of 0.9201. Optimized oil yield showed close match between actual and predicted responses with a desirability factor of 0.999. The predicted mixture compositions and operating parameters for the optimum oil yield were 52.86% for LDPE, 47.15% for PS, and 0% for PET at 471.07°C and 115.25 minutes. The chemical compositions of the pyrolysis oil at the optimum conditions were hydrocarbons in the carbon range between C6 and C25, with physical properties comparable to conventional diesel.

Synergistic Effects and Mechanistic Insights into the Co-Hydropyrolysis of Chilean Oak and Polyethylene: Unlocking the Potential of Biomass–Plastic Valorisation

“…Such hydrocarbon content increase is accompanied by lower acids, improving the bio-oil quality by increasing stability and calorific value and reducing corrosion problems. An elemental analysis performed on the mixture with 40% HDPE reported +14% for carbon and −50% for oxygen and a calorific value of 42 MJ/kg (43% higher than calculated), similar to the commercial diesel reported values [ 33 , 37 ].…”

“…Conversely, xylene, toluene, and benzene exhibited decreased levels compared to individual pyrolysis [ 32 ]. Additionally, Oladunni et al, 2021 reported the presence of unsaturated hydrocarbons (C=C) and aromatic hydrocarbons in the pyrolysis of LDPE, along with the detection of free OH radicals, reactive carbonyl groups, aldehydes, ketones, esters, and conjugated carboxylic acids through FTIR analysis [ 33 ]. This finding is supported by a previous study by Kayacan and Dogan (2008), who observed that aliphatic (C-C and C-H) and CH2 groups were the predominant components in the pyrolysis of raw and waste HDPE and LDPE [ 34 ].…”

Molecular Characterization of a Mixed Plastic Pyrolysis Oil from Municipal Wastes by Direct Infusion Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

“…The oil fraction can be then valorized as fuels or reused as monomers after steamcracking. Studies have shown that the proportions of each fraction are directly related to the reactor type and operating conditions set as temperature, pressure, fluidized gas flow rate, or residence time. − It has also been shown that the use of catalysts impacts the fraction ratio . Moreover, the composition of raw plastic material is also a determining factor .…”