Recycling of post-use starch-based plastic bags through pyrolysis to produce sulfonated catalysts and chemicals

Pyrolysis was explored as a technology for depolymerizing and charring starch-based plastic bags in a novel valorization perspective based on a chemical recycling strategy, alternative to anaerobic digestion or composting. The char obtained from the thermal treatment (420°C for 15 h) was sulfonated to give a highly active and recyclable heterogeneous acid catalyst (10 wt% yield based on starch-based plastic bags subjected to pyrolysis), comparable in terms of catalytic activity and reusability to the analog catalyst prepared from potato starch and tested on a model esterification reaction. From pyrolysis liquid of starch-based plastic bags, highly pure terephthalic acid (4 wt% yield) was isolated through self-precipitation, whereas the remaining pyrolysis liquid produced (21 wt%) was solvent-fractionated to give a polar fraction (7 wt% yield) enriched in levoglucosan, and a less polar fraction (14 wt% yield) enriched in monobutenyl adipate and terephthalate.