(272d) Solvothermal Conversion: Crude Oil Production from Waste Plastics

The global production and consumption of plastics have been increasing continuously. As plastic materials are durable and very slow to degrade, they are stable in the environment. The over-consumption and littering of plastics result in pollution, thus causing serious environmental consequences. As a result, one of the most talking points in today's’ research world is to find a feasible way to reuse or recycle these plastic wastes.

Solvothermal conversion is a thermochemical process, where a waste feedstock is treated in the presence of a solvent at a temperature higher than the boiling temperature of this solvent. Benzene, toluene, and xylene are the most common solvents used in the solvothermal conversion. These solvents are also known as BTX chemicals which are byproducts of a refinery plant. In the solvothermal process, the solvents play a significant role in overall conversion, distribution of products, and crude-oil yield and properties. For instance, the presence of organic solvents during the solvothermal process allows the product to contain important functional groups. Although, a few works have been done on thermochemical conversion of plastic wastes and solvothermal removal of brominated flame retardant from electronic waste plastic. However, to the best of the authors’ knowledge, none of the studies have used BTX to upgrade plastic wastes.

Therefore, the aim of this study was to investigate the optimal solvothermal condition for upgrading plastic wastes to crude oil and feed into a refinery plant. In this regard, two different wastes, such as polypropylene (PP) and polystyrene (PS) were solvothermally treated in presence of one of the BTEX chemicals (i.e., toluene) at its sub and super critical conditions (300 and 350 °C) for 1.0 to 6.0 hours. Various thermal analyses, such as TGA and DSC were conducted to investigate the product quality. Additionally, FTIR was used to see the change in specific functional groups in the product compared to feedstock. Furthermore, the GC-MS analysis of the product was conducted to investigate the presence of elements and species. Results showed that both feedstocks degraded more favorably at supercritical conditions. In terms of product quality, the supercritically converted products can be feed to the refinery as their quality (e.g., boiling point distribution, functional groups, etc.) is similar to the crude oil.