LAUSR

Abstract In this work real polypropylene (PP) waste plastic was used as a feedstock for synthesis of carbon nanomaterials (CNMs) via a two-stage process. Lanthanum oxide (La2O3) was reported as a promising support for the active metals in thermocatalytic decomposition of hydrocarbons. This is due to the fact that it produces highly dispersed metal particles with an appropriate metal support interaction. Accordingly, La2O3 supported monometallic 50%Ni and bimetallic 40%Ni–10%Cu catalysts with the total metal content of 50 wt % were prepared and examined for the first time for the decomposition of non-condensable gases obtained from pyrolysis of PP to produce CNMs. The main target of this work is to study the impact of Cu addition on the yield and nature of as-deposited carbon product. The prepared catalysts were tested at the same pyrolysis and decomposition temperatures of 500 °C and 700 °C, respectively, and reaction time of 2.5 h. Various characterization techniques such as XRD, H2-TPR, BET surface area and FTIR were used to study the physicochemical properties of fresh catalysts. While, HR-TEM, XRD, Raman spectroscopy and TGA-DTG techniques were employed on the spent catalysts to explore the nature, morphology, quality and thermal properties of CNMs product. It was observed that the bimetallic Ni–Cu/La2O3 catalyst exhibited higher surface area, higher metal dispersion as well as lower reduction temperature compared to the monometallic 50%Ni/La2O3 catalyst. These factors were found to be responsible for the improved catalytic growth activity of the 40%Ni–10%Cu/La2O3 catalyst in terms of carbon yield. The CNMs yield remarkably increased from 944% to 1458% after incorporating 10 wt% Cu in 40%Ni/La2O3 catalyst. TEM images showed that multi-walled carbon nanotubes (MWCNTs) with regular diameters were formed over 50%Ni/La2O3 catalyst, while a mixture of large diameter carbon nanofibers (CNFs) and MWCNTs were produced over the 40%Ni–10%Cu/La2O3 catalyst.