Investigation of Ni-Al, Ni-Mg-Al and Ni-Cu-Al catalyst for hydrogen production from pyrolysis-gasification of polypropylene

Co-precipitated nickel-based catalysts with different metallic molar ratios and calcination temperature were investigated for the production of hydrogen from the pyrolysis-gasification of polypropylene. The experiments were carried out at a pyrolysis temperature of 500 °C and gasification temperature of 800 °C in the presence of steam using a two-stage reaction system. The results suggest that with increasing Ni content in the Ni-Al or Ni-Mg-Al catalyst, the catalytic activity of the catalyst increased, in relation to hydrogen production. For example, the potential hydrogen production increased from 48.8 to 57.7 wt.%, and the amount of water reacted increased from 1.2 to 1.3 (g water/g polypropylene), when the Ni-Al molar ratio was increased from 1:4 to 1:1. After reaction in the pyrolysis-gasification process, the non-reduced Ni-Al catalyst was reduced into metallic Ni, as observed from XRD and TGA analysis. The introduction of Mg into the Ni-Al catalyst significantly increased the amount of reacted water and improved the performance of the catalyst in relation to coke formation, although the hydrogen production was not significantly improved. For the Ni-Al or Ni-Mg-Al catalyst, a 850 °C calcination temperature resulted in a lower catalytic activity compared to the lower calcination temperature of 750 °C. The substitution of Cu for Mg in the Ni-Mg-Al catalyst significantly reduced the catalytic ability for hydrogen production.