Catalytic Performance of Calcium Titanate for Catalytic Decomposition of Waste Polypropylene to Carbon Nanotubes in a Single-Stage CVD Reactor

Helen Uchenna Modekwe,Messai Adenew Mamo,Kapil Moothi,Michael Olawale Daramola

doi:10.3390/catal10091030

Helen Uchenna Modekwe, Messai Adenew Mamo + Show 2 more

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https://doi.org/10.3390/catal10091030

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Abstract

Calcium titanate mixed metal oxides with different contents were used as supports for NiMo catalyst prepared by the sol–gel method. The activities of these catalysts were tested in the catalytic decomposition of waste polypropylene (PP) for the synthesis of carbon nanotubes (CNTs) using a single-stage chemical vapor deposition technique. The physico-chemical properties of the catalysts and deposited carbon over the catalysts were checked by X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature-programmed reduction (TPR), N2 physisorption, transmission electron microscopy (TEM), Raman spectroscopy, and thermogravimetric analysis (TGA). The TEM and XRD results presented a high dispersion of the active metal species on the surface of the support materials. The result showed that increasing the support content led to an increased crystallite size of the catalysts and a resultant reduction in CNTs yield from 44% to 35%. NiMo-supported CaTiO3 catalyst displayed good catalytic activity and stability toward CNTs growth. Furthermore, the effect of calcination temperature on the morphology, yield, and quality of CNTs was also studied, and it was observed that thermal treatment up to 700 °C could produce well graphitized, high-quality, and high-yield CNTs from the waste PP.

Highlights

Carbon nanotubes (CNTs) are one-dimensional graphene sheets rolled up into seamless tubes and they are generally classified according to their number of wall(s) as single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (MWCNTs) [1,2]
The yield, quality, and morphology of carbon nanotubes (CNTs) obtained from waste PP is greatly influenced by the amount of catalyst support in the catalyst
CaTiO3 catalysts with excellent stability and superior activity for the synthesis of CNTs from waste PP

Summary

Introduction

Carbon nanotubes (CNTs) are one-dimensional graphene sheets rolled up into seamless tubes and they are generally classified according to their number of wall(s) as single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (MWCNTs) [1,2]. Considering the enormous global demand and application of CNTs, it is plausible that the cost of production is minimized while yield and quality are maximized. Wang et al [18] synthesized high yield (93%) filamentous carbon from the catalytic pyrolysis of waste PP over Ni-based catalyst in a two-stage fixed bed reactor system. Yao and Wang [19] obtained an improved yield of bamboo-like MWCNTs with average diameter of 22 nm during the catalytic decomposition of PP, and they revealed that the catalyst component and preparation method significantly affect the carbon yield. The growing demand and consumption of PP materials from different sectors such as in packaging, automobile, etc., resulted in their increased prevalence in the waste stream, since it is expected that most consumed plastics should constitute the highest waste given their non-biodegradability. PP is estimated to contribute over 24.3% to the waste stream globally, and it is the largest class of waste found in municipal solid wastes (MSW) [20,21]

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