Pressurized carbonization of mixed plastics into porous carbon sheets on magnesium oxide

Conversion of waste thermoplastics into porous carbons has attracted wide attention due to the requirement of recycling of large quantities of municipal solid waste. This work reports the preparation of porous carbon sheets on magnesium oxide from mixed thermoplastics including polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate in a closed autoclave at 500 °C. The influence of the weight ratio of magnesium oxide to mixed plastics on the yield and textural properties of the carbon was examined. The morphology and structure of the porous carbon were also characterized. The maximum BET surface area was 713 m² g^-1 at a weight ratio of MgO/polymer of 4 and the maximum pore volume was 5.27 cm³ g^-1 at a weight ratio of MgO/polymer of 6. The reaction mechanism was explored by analyzing the product distribution and composition of gas and liquid at different reaction times. Aromatics were the main source for the growth of carbon. Model experiments of carbonization of different aromatics were conducted to evaluate the carbonization reactivity of aromatics. Polycyclic aromatic hydrocarbons, especially acenes, produced more carbon.