Hydrogen from Waste Plastics by Two-Stage Pyrolysis/Low-Temperature Plasma Catalytic Processing

Hydrogen was produced from waste plastic (polyethylene) using a novel two-stage pyrolysis–low-temperature (250 °C) plasma catalytic steam reforming process. Pyrolysis of the polyethylene generated pyrolysis gases, which were catalytically steam-reformed in the presence of low-temperature non-thermal plasma (dielectric barrier discharge) to produce hydrogen gas. In the absence of a catalyst, increasing the plasma power resulted in a significant increase in the hydrogen yield. Different catalysts (Ni/Al2O3, Fe/Al2O3, Co/Al2O3, and Cu/Al2O3) were incorporated in the discharge region of the plasma reactor, and Ni/Al2O3 produced the highest yield of hydrogen at 1.5 mmol g–1plastic. The addition of steam to the plasma catalytic process was investigated at different steam weight hourly space velocities (WHSVs) using the Ni/Al2O3 catalyst. The addition of steam to promote catalytic steam reforming reactions resulted in a marked increase in the hydrogen yield, producing the highest hydrogen yield of 4.56 mmol g–1plastic at a WHSV of 4 g h–1 g–1catalyst.