Hydrogen production and value-added chemical recovery from the photo-reforming process using waste plastics

Abstract

Photo-reforming is a novel and promising green H2 production method with enhanced catalytic efficiency via optimizing the oxidation reaction by introducing an organic compound as the sacrificial agent. This study focuses on the degradation of different plastic wastes, such as polyethylene terephthalate (PET), low-density polyethylene (LDPE), and polystyrene (PS) as sacrificial agents in the photo-reforming process for H2 production. The process was optimized by evaluating H2 production under different plastic pretreatment methods and the polymer-to-catalyst ratio. Disodium terephthalate (Na2TP) and terephthalic acid (TPA) were identified as byproducts after the alkaline pretreatment of PET, and these extracted products were re-applied in the photo-reforming process and tested for their applicability in H2 generation. The degradation of plastics and their respective pretreatment byproducts were characterized using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and thermogravimetric analysis (TGA). PET was the best sacrificial agent in H2 production under almost all conditions whereas 4026 μmol/gcat/gPET was produced under ethanol-induced pretreatment at 40 °C. This combined analysis indicates H2 can be successfully generated from LDPE, PET, PS, and degradation byproducts. Further, TPA and Na2TP can be extracted from the reaction mixture for reuse. This study revealed the mechanisms of using plastics as sacrificial agents and the intermediate byproducts in the photo-reforming process on H2 evolution efficiency. It provides the opportunity for green H2 generation while degrading plastic waste by solving multiple environmental issues with revenue generation.