Production of nanostructure carbon materials via non-oxidative
thermal degradation of real polypropylene waste plastic using La
2
O
3
supported Ni and NieCu catalysts
Ateyya A. Aboul-Enein
a, b
, Ahmed E. Awadallah
a, b, *
a
Process Development Division, Egyptian Petroleum Research Institute, Nasr City, PO Box 11727, Cairo, Egypt
b
EPRI-Nanotechnology Center, Egyptian Petroleum Research Institute, Nasr City, PO Box 11727, Cairo, Egypt
article info
Article history:
Received 23 January 2019
Received in revised form
16 June 2019
Accepted 18 June 2019
Available online 19 June 2019
Keywords:
Carbon nanomaterials
Polypropylene plastic waste
Pyrolysis
NieCu/La
2
O
3
catalyst
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 (La
2
O
3
) 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, La
2
O
3
supported monometallic 50%Ni and bimetallic 40%Nie10%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, H
2
-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 NieCu/La
2
O
3
catalyst exhibited higher surface area, higher metal dispersion as well as
lower reduction temperature compared to the monometallic 50%Ni/La
2
O
3
catalyst. These factors were
found to be responsible for the improved catalytic growth activity of the 40%Nie10%Cu/La
2
O
3
catalyst in
terms of carbon yield. The CNMs yield remarkably increased from 944% to 1458% after incorporating
10 wt% Cu in 40%Ni/La
2
O
3
catalyst. TEM images showed that multi-walled carbon nanotubes (MWCNTs)
with regular diameters were formed over 50%Ni/La
2
O
3
catalyst, while a mixture of large diameter carbon
nanofibers (CNFs) and MWCNTs were produced over the 40%Nie10%Cu/La
2
O
3
catalyst.
© 2019 Elsevier Ltd. All rights reserved.
1. Introduction
Plastics in particular polymer-based materials are one of the
most widely used substances in many industrial and social fields.
As a result, the global production and consumption of plastics have
increased rapidly, resulting in the generation of drastic quantities of
solid waste. This solid waste can be regarded as one of the main
sources of air, soil, water, and marine pollution [1e5]. At present,
landfill and incineration treatments are still broadly used for waste
management, inducing also dangerous problems in the
environment and human health as well as losing energy stored in
plastic [2,3]. Therefore, it is necessary to find economically alter-
native routes for the removal of plastic waste from the environ-
ment. One of the most prospective technologies is the manufacture
of high-value-added carbon nanomaterials (CNMs) products such
as multi-walled carbon nanotubes (MWCNTs) and carbon nano-
fibers (CNFs) by using plastic waste as a carbonaceous feedstock
[6e13]. In addition, the utilization of plastic waste for the synthesis
of CNMs instead of the traditional natural gas source is very
important from economic and environmental aspects. A further
merit of this process is the generation of hydrogen-rich gas as a
valuable by-product [14,15]. Among the various types of plastic
waste, polyethylene (PE) and polypropylene (PP) are considered as
a potential hydrocarbon source due to their high carbon content
* Corresponding author. Process Development Division, Egyptian Petroleum
Research Institute, Nasr City, PO Box 11727, Cairo, Egypt.
E-mail address: ahmedelsayed_epri@yahoo.com (A.E. Awadallah).
Contents lists available at ScienceDirect
Polymer Degradation and Stability
journal homepage: www.elsevier.com/locate/polydegstab
https://doi.org/10.1016/j.polymdegradstab.2019.06.015
0141-3910/© 2019 Elsevier Ltd. All rights reserved.
Polymer Degradation and Stability 167 (2019) 157e169