Pyrolysis–catalysis of waste plastic using a nickel–stainless-steel mesh catalyst for high-value carbon products

Abstract

A stainless-steel mesh loaded with nickel catalyst was produced and used for the pyrolysis-catalysis of waste high-density polyethylene with the aim of producing high-value carbon products, including carbon nanotubes (CNTs). The catalysis temperature and plastic-to-catalyst ratio were investigated to determine the influence on the formation of different types of carbon deposited on the nickel-stainless-steel mesh catalyst. Increasing temperature from 700 to 900°C resulted in an increase in the carbon deposited on the nickel-loaded stainless-steel mesh catalyst from 32.5 to 38.0 wt%. The increase in sample-to-catalyst ratio reduced the amount of carbon deposited on the mesh catalyst in terms of g carbon g −1 plastic. The carbons were found to be largely composed of filamentous carbons, with negligible disordered (amorphous) carbons. Transmission electron microscopy analysis of the filamentous carbons revealed them to be composed of a large proportion (estimated at ∼40%) multi-walled carbon nanotubes (MWCNTs). The optimum process conditions for CNT production, in terms of yield and graphitic nature, determined by Raman spectroscopy, was catalysis temperature of 800°C and plastic-to-catalyst ratio of 1:2, where a mass of 334 mg of filamentous/MWCNTs g −1 plastic was produced.ARTICLE HISTORY

Fine structural changes of fluid catalytic catalysts and characterization of coke formed resulting from heavy oil devolatilization

“…By comparing the different oxidation characteristics of the FCC catalysts, the results enable the identification of the different phases of carbon/coke present, based on the differing thermal stability of the two types of carbon/coke depositions. Amorphous carbon is oxidized at a lower temperature (<600 o C), compared with the graphitic carbon, since the latter filamentous carbon has higher thermal stability [36][37][38][39][40][41].…”

Coke formation and deactivation during catalytic reforming of biomass and waste pyrolysis products: A review

“…Considering the unwanted nature of the generation of these carbon deposits, the economic throughput of the H2 production process from hydrocarbons may be enhanced by means of the production of value-added carbon materials ( Figure 17). For instance, char is reported in the literature as a promising precursor for graphene production [305,306], whereas the coke deposited on the catalyst (catalytic routes) may be in the form of carbon nanotubes [307,308], whose morphology shows multiple favorable applications [309].…”

Hydrogen and Carbon Nanotubes from Pyrolysis-Catalysis of Waste Plastics: A Review

“…Recovery of the carbon nanotubes from the catalysts via acid dissolution of the catalyst has been used, but reported to damage the structure of the carbon nanotubes [76]. A novel catalyst in the form of nickel impregnated steel mesh was reported to produce high yields of carbon nanotubes and carbon nanofibers which were reported to be easily removed from the mesh substrate by a mechanical process [121].…”

“…The carbon nanotubes can become encapsulated and intermingled with the catalyst particles, making recovery of the carbon nanotubes difficult. Zhang et al [121] used a two-stage pyrolysiscatalytic reactor with a novel nickel impregnated stainless steel mesh in the catalyst stage to produce carbon nanotubes. The plastic used was high density polyethylene.…”

“…The production of carbon nanotubes produced from waste plastics by pyrolysis and chemical vapour deposition catalysis are often accompanied by the production of carbon nanofibers, that is, solid filaments rather than hollow tubes [76,121,129]. Indeed, Zhang et al [121] estimated that the proportion of carbon nanofibers compared to carbon nanotubes was up to 40% for filamentous type carbons produced from waste plastics using their nickel-stainless steel mesh catalyst. Chatterjee and Deopura [130] have discussed the mechanism of formation for carbon nanofibers compared to carbon nanotubes.…”