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 degrees 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(-1) plastic. 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(-1) plastic at a WHSV of 4 g h(-1) g(-1) catalyst.