Exploration of operating conditions in the direct aqueous-phase reforming of plastics

Plastic materials are employed in countless applications, resulting in a high amount of waste and the need for alternatives to landfill. In the current work, an alternative to reduce and revalorize waste plastic using direct aqueous-phase reforming (APR), a catalytic process to produce hydrogen and/or alkanes from organic molecules, is proposed with a focus on polyethylene terephthalate. The effect of operating conditions including temperature (190–235 °C), pH (3–12), and the type of metal catalyst and support, was studied. Pt catalysts yielded at 220 °C 5 mmol of H2/g of plastic in 4-hour reaction tests, which increased up to 10 mmol of H2/g of plastic for an 8-hour reaction time. Additionally, low amounts of short-chain alkanes were detected (<1.4 mmol of alkanes/g of plastic). The production of H2 was also improved by increasing reaction temperature up to 235 °C, and by using Pt-based bimetallic catalysts and supports with well-developed mesopore area. The results obtained confirm the potential of this strategy as a useful and simple way to transform plastic waste, especially PET, into H2.