Pellet size dependent steam reforming of polyethylene terephthalate waste for hydrogen production over Ni/La promoted Al2O3 catalyst

Abstract

The effect of different pellet sizes of nickel (Ni) and lanthanum (La) promoted Al2O3 support on the catalytic performance for selective hydrogen production from polyethylene terephthalate (PET) plastic waste via steam reforming process has been investigated. The catalysts were prepared by impregnation method and were characterized using XRD, BET, TPD-CO2, TPR, SEM, EDX, TEM and TGA. The results showed that NiLa-co-impregnated Al2O3 catalyst has excellent activity for the production of hydrogen. Feed conversion of 88.53% was achieved over 10% Ni/Al2O3 catalyst which increased to 95.83% in the case of 10% Ni-5% La/Al2O3 catalysts with a H2 selectivity of 70.44%. The catalyst performance in term of gas production and feed conversion was further investigated under various operating parameters, e.g., feed flow-rate, and catalyst pellet size. It was found that at 0.4 ml/min feed flow rate, highest feed conversion and H2 selectivity were achieved. The Ni particles, which are the noble-based active species are highly effective, thus offered good hydrogen production in the phenol-PET steam reforming process. Incorporation of La as a promoter in Ni/Al2O3 catalyst has significantly increased the catalyst reusability with prolonged stability. The NiLa/Al2O3 catalyst with larger size showed remarkable activity due to the presence of significant temperature gradients inside the pellet compared to smaller size. Additionally, the catalyst showed only slight decrease in H2 selectivity and feed conversion even after 24 h, although production of carbon nanotubes was evidenced on its surface.