Fe-Ni-MCM-41 Catalysts for Hydrogen-Rich Syngas Production from Waste Plastics by Pyrolysis-Catalytic Steam Reforming

A two-stage pyrolysis-catalytic steam reforming process was used with mesoporous MCM-41 supported iron and nickel bimetallic catalysts for hydrogen-rich syngas production from a simulated mixture of waste plastics. Different Fe/Ni weight ratios (00:20, 05:15, 10:10, 05:15, and 20:00) have been investigated to determine the influence on hydrogen production. The results showed that the presence of Fe and Ni together produced a synergistic enhancement of the total gas yield and hydrogen and carbon monoxide production. For example, the (10:10) Fe-Ni-MCM-41 catalyst produced the highest gas yield of 95 wt %, the highest H-2 production of 46.1 mmol H-2 g(-1)plastic, and the highest CO production at 31.8 mm g(-1)plastic. The (10:10) Fe-Ni-MCM-41 catalyst produced a volumetric hydrogen concentration of 46.7 vol %, and carbon monoxide was 32.2 vol %. The (10:10) Fe-Ni-MCM-41 catalyst also showed the lowest carbon deposition on the catalyst. The carbon deposits were mainly of the amorphous encapsulating type for the iron catalyst, but when nickel was present, the carbon deposits were mainly filamentous. The carbon deposits were also analyzed by transmission electron microscopy with energy-dispersive X-ray spectroscopy elemental mapping and showed that the iron/nickel metal particles were involved in the formation of the filamentous carbons, which were found to be both solid and hollow filaments.