Hydrogen Production by Pyrolysis-Nonthermal Plasma/Catalytic Reforming of Waste Plastic over Different Catalyst Support Materials

A two-stage pyrolysis-nonthermal plasma/catalytic steam reforming reactor system was used to produce hydrogen from waste high-density polyethylene in relation to different catalyst support materials. The catalyst support materials investigated were MCM-41, Y-zeolite, ZSM-5, Al2O3, TiO2, dolomite, BaTiO3, CaTiO3, and Mo2C. Some of the materials suppressed the generation of plasma, while others enhanced it by improving the generation of microdischarges and surface discharges. Among the tested materials, MCM-41 gave the highest gas yield of 29.2 wt % and a hydrogen yield of 11 mmol g(plastic)(-1). The coupling of the catalyst with the plasma environment resulted in synergy in terms of enhanced total gas yield and hydrogen production, which were higher than those in the absence of plasma (catalyst alone) or plasma alone (no catalyst). Other parameters investigated using the MCM-41 support material showed that the particle size and the catalyst bed depth affected the plasma discharge and the total gas yield. Impregnating nickel (10 wt %) on the MCM-41 support further enhanced the total gas yield to 33.3 wt % and the hydrogen yield to 18 mmol g(plastic)(-1) due to increased surface reactions. The 10 wt % Ni/MCM-41 was stable when subjected to a 3 h stability test showing no significant change in the yield of the gases.