Evaluation of Pyrolysis Wax as a Solvent in Polyolefin Pyrolysis Processing

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Department of Chemical Engineering


A lack of recycling-process technologies has led to plastic pollution becoming one of the world's greatest environmental crises. Plastic fast pyrolysis is a recycling technology that may enable the conversion of waste plastic into virgin-quality plastic resin, thereby contributing to a circular economy for plastics. In this study, pyrolysis wax, a byproduct of the plastic pyrolysis process, was evaluated for its use as a solvent for plastic waste in preparation for pyrolysis. The viscosity of a 1:1 ratio mixture of pyrolysis wax with HDPE and PP at 220, 240, and 260 °C was measured. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were performed at three different weight percentages of the samples (25, 50, and 75 wt %) to determine the solubility and characterize the thermal behavior of HDPE/pyrolysis wax, LDPE/pyrolysis wax, and PP/pyrolysis wax mixtures. A unique semibatch pyrolysis pilot plant, including a dissolution tank and a tubular pyrolysis reactor, was used to convert pyrolysis wax/plastic feed at 600 °C. The reaction exhibited a complete conversion with a residence time of approximately 2 s, while GC-MS analysis demonstrated pyrolysis of both the wax and HDPE in the feed. Plastic waste and pyrolysis wax are soluble at 240 °C for up to 75 wt % of plastic. The pilot plant experiment, with its semibatch system involving a dissolution tank, verifies the feasibility of using pyrolysis wax as a viscosity-reducing strategy prior to pyrolysis.

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Industrial and Engineering Chemistry Research