Effects of gasification temperature and catalyst ratio on hydrogen production from catalytic steam pyrolysis-gasification of polypropylene

A two-stage reaction system was used for the pyrolysis-gasification of polypropylene in the presence of stearn and a Ni/CeO₂/ Al₂O₃ catalyst. The influence of catalyst ratio 0, 0.25, 0.5, 1.0, and 2.0 and gasification temperature 600, 700, 800, and 900 °C) on the production of hydrogen were investigated. The reacted catalysts were characterized using thermogravimetric analysis and scanning electron microscopy-energy dispersive X-ray spectrometry. The maximum potential hydrogen production was only 5 wt % without the catalyst, however it increased to 52.8 wt % in the presence of the Ni/CeO₂ /Al₂O₃ catalyst at a catalyst/ polypropylene ration of 1. Increasing the catalyst:polypropylene ratio resulted in an increase in hydrogen production and a decrease of coke deposited on the catalyst surface but showed little influence on the CO and CO₂ concentrations. Increasing the gasification temperature resulted in a marked increase in potential hydrogen production from 13.4 to 52.0 wt %, as the gasification temperature was increased from 600 to 900 °C. In addition, the CO concentration increased from 9.3 to 27.2 vol %, and CO₂ concentration decreased from 17.8 to 4.5 vol % with increasing gasification temperature.