Hydrogen Production from Glycerol and Plastics by Sorption-Enhanced Steam Reforming

Hydrogen (H-2) serves as a vital precursor in numerous processes, and it is envisioned to serve as a clean energy source in the future. The utilization of waste materials for the production of H-2 presents a noteworthy opportunity to advance the sustainability of H-2-based energy. In this study, the effect of cofeeding three different types of plastic, polyethylene (PE), polypropylene (PP), and polystyrene (PS), with glycerol was investigated in the two-step process of pyrolysis and steam reforming (PSR) to produce H-2. Experiments were performed using a two-stage fixed bed reactor at 973 K. For each type of plastic, the yield of H-2 in the copresence of glycerol was higher than the combined yield of that from the plastic and glycerol separately. This result demonstrated the effectiveness of the synergistic relationship between plastics and glycerol in enhancing H-2 production through PSR. Among the plastics, PE gave the highest H-2 yield followed by PP and PS. Bifunctional nickel oxide/calcium oxide (NiO-CaO) catalysts were synthesized for the pyrolysis sorption-enhanced steam reforming process (PSESR) of plastics with glycerol at 973 K. The maximum H-2 yield was obtained from the PSESR of PE with glycerol when using a NiCa/silica fiber (SF) catalyst. Using NiO combined with CaO in PSESR can promote the cracking of volatile pyrolysis products, reducing the coke deposition and increasing CO2 adsorption. Furthermore, the nonporous structure of the SF support afforded easier access to the active sites in comparison to the conventional porous alumina support.