Thermal processing of plastics from waste electrical and electronic equipment for hydrogen production

Plastic waste from waste electrical and electronic equipment (WEEE) produced from a real-world commercial WEEE recycling centre has been processed using pyrolysis–gasification using a two-stage reaction system to produce hydrogen. In the first stage, the plastic fraction was pyrolysed at 600 °C and the evolved pyrolysis gases were passed directly to a second reactor at 800 °C and reacted with steam in the presence of a Ni/Al2O3 catalyst. In addition, high impact polystyrene (HIPS) and acrylonitrile–butadiene–styrene (ABS) which were the main components of the WEEE plastic were reacted to compare with the WEEE plastic. The results showed that the introduction of steam and the catalyst increased the yield of hydrogen. Increasing the nickel content in the catalyst also resulted in higher hydrogen yield. The comparison of the results of WEEE with those of HIPS and ABS showed that WEEE plastic was mainly composed of ABS. The catalyst, after reaction, showed significant deposition of coke composed of filamentous and layered type carbon. Overall the novel processing of waste plastic from electrical and electronic equipment using a two stage pyrolysis–gasification reactor shows great promise for the production of hydrogen.

► Waste plastic from a WEEE recycling centre has been processed to produce H2. ► A pyrolysis–catalytic steam gasification system was used with an NiAl2O3 catalyst. ► Product yield and composition from WEEE plastic was compared with HIPS and ABS. ► Between 35 vol% and 55 vol% H2 was produced from WEEE plastic. ► High mol. wt. aromatics are cracked to lighter aromatics and hydrocarbon gases.