(4kl) Hydrothermal Liquefaction of Biomass and Mixed Plastics for Fuel and Chemicals

Plastic waste has become a significant issue in waste management sector due to its high production rate, and minimal recycling effort. Conventional disposal methods of these robust polymeric materials with different chemical compositions are posing a serious threat to the environment. Depolymerization technology offers a potential solution to reduce the enormous amount of plastic waste by recovering valuable chemicals. This research has focused on the valorization of waste plastic products by the hydrothermal liquefaction (HTL) method for two well-known plastic polymers: high-density polyethylene (HDPE) and polystyrene (PS).The HTL reaction was conducted in an 1800 ml autoclave batch reactor with an average reaction temperature of 430 °C and a residence time of 2 hours. The HTL conversion of HDPE plastic yielded 76 wt.% of crude product, whereas the PS mainly resulted in 73wt.% of crude fractions. PS feedstock primarily decomposed into aromatic and cyclic compounds with an energy content of 39 MJ/kg, whereas HDPE was transformed into straight-chain alkanes with a calorific value of 44.5 MJ/kg. A maximum of 92 wt.% of gasoline-range compounds were found in PS crude products, while 36 wt.% of the same boiling point range compounds were identified in HDPE-derived products. The following step involved co-liquifying HDPE and PS plastic polymers in varying ratios to formulate a fuel-grade crude product with an appropriate concentration of aromatic and alkane compounds. The optimum proportion of HDPE to PS in the mixed feedstock was determined by analyzing the resulting crudes using GC-MS analysis. To comply with the fuel standard, a catalytic hydrotreatment was applied to the unsaturated hydrocarbon content of cotreated crude product from the optimized HDPE-PS mixture with thorough analysis. The outcomes of this study will facilitate the treatment of HDPE and PS plastic waste while promoting the development of sustainable fuel.

Research Interests

The research interests of presenting author include waste to energy, thermochemical conversion technologies, biorefineries and fuels and the teaching interests covers the area of renewable energy, heat and mass transfer in chemical process, biomass to bioenergy and waste recycling topics.