Carbon nanotubes synthesis over coal ash based catalysts using polypropylene waste via CVD process: Influence of catalyst and reaction temperature

• Published in: Journal of environmental management Vol. 366; p. 121881
• Main Authors: Chitriv, Shubham P., Saini, Vageesh, Ratna, Debarshi, P, Vijayakumar R.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.08.2024
• Subjects: ash (inorganic matter); Carbon nanotubes; Catalysis; catalysts; catalytic activity; Chemical vapor deposition; circular economy; Coal ash; Coal Ash - chemistry; cobalt; iron; Nanotubes, Carbon - chemistry; nickel; plastics; polypropylenes; Polypropylenes - chemistry; Pyrolysis; Solid waste management; Temperature; thermal stability; Thermogravimetry; vapors; waste management; wastes; Carbon nanotubes; Pyrolysis; Chemical vapor deposition; Solid waste management; Coal ash
• ISSN: 0301-4797; 1095-8630; 1095-8630
• DOI: 10.1016/j.jenvman.2024.121881

Coal ash containing significant amount of SiO2 and Al2O3 is utilized as a catalyst substrate for carbon nanotubes (CNTs) synthesis. Three different types of catalysts were made by impregnating coal ash with cobalt, iron, and nickel. These catalysts were used to produce CNTs through pyrolysis of waste polypropylene followed by chemical vapor deposition. The influence of catalyst type and reaction temperature (700, 800 and 900 °C) on CNTs yield and its quality was studied in detail. The produced CNTs were characterized by thermogravimetric analysis (TGA), Raman scattering and electron microscopes (FESEM and HRTEM). The TGA results revealed that the Ni catalyst produced CNTs with highest yield (266 %) compared to those synthesized over and Fe (96 %) and Co (95 %). However, the yield of the CNTs from all three metal impregnated coal ash based catalysts was found to have decreased with increase in reaction temperature. The thermal stability of CNTs obtained over different catalysts followed the order of Fe (570 °C) > Ni (550 °C) > Co (530 °C). Further, the Raman analysis demonstrated that the produced CNTs over different catalysts showed increasing degree of graphitization with the rise in reaction temperature. Additionally, the ID/IG ratios indicated that CNTs produced from Fe catalyst showed highest degree of graphitization followed by Co and Ni. FESEM and HRTEM analysis showed that the coal ash based catalysts produced multiwalled CNTs and the diameter of the CNTs was increasing with the rise in catalysis temperature. Therefore, co-utilization of coal ash and waste plastic for production of high value CNTs can be a sustainable approach to waste management while actively contributing in circular economy. [Display omitted] •Co, Fe and Ni coal ash catalysts were used to obtain CNTs at various temperatures•Fe catalyst gave highly graphitized and thermally stable CNTs than Co and Ni•Highest CNTs yield of 266 % was obtained with Ni catalyst•Better graphitized CNTs were obtained at high reaction temperature of 900 °C•Bamboo type and cobweb structured CNTs were observed with all the catalysts