Upcycling Waste Plastics into Multi-Walled Carbon Nanotube Composites via NiCo2O4 Catalytic Pyrolysis

Abstract

In this work, multi-walled carbon nanotube composites (MWCNCs) were produced by catalytic pyrolysis of post-consumer plastics with aluminium oxide-supported nickel, cobalt, and their bimetallic (Ni/α–Al2O3, Co/α–Al2O3, and NiCo/α–Al2O3) oxide-based catalysts. The influence of catalyst composition and catalytic reaction temperature on the carbon yield and structure of CNCs were investigated. Different temperatures (800, 900, 950, and 1000 °C) and catalyst compositions (Ni, Co, and Ni/Co) were explored to maximize the yield of carbon deposited on the catalyst. The obtained results showed that at the same catalytic temperature (900 °C), a Ni/Co bimetallic catalyst exhibited higher carbon yield than the individual monometallic catalysts due to a better cracking capability on carbon-hydrogen bonds. With the increase of temperature, the carbon yield of the Ni/Co bimetallic catalyst increased first and then decreased. At a temperature of 950 °C, the Ni/Co bimetallic catalyst achieved its largest carbon yield, which can reach 255 mg g−1plastic. The growth of CNCs followed a “particle-wire-tube” mechanism for all studied catalysts. This work finds the potential application of complex oxide composite material catalysts for the generation of CNCs in catalytic pyrolysis of wasted plastic.

Efficient transformation of plastic wastes to H2 and electromagnetic nanocarbon absorbents over molecular-level engineered 3D NiCo/MnO

“…Interestingly, the particles with diameters of lower than 100 nm were found to insert in the carbon nanotubes, while those with larger diameters were found to be adjacent to the filamentous materials. Based on our former work [22,27] , the particles inserted in the carbon nanotubes should be NiCo catalysts, while the larger particles adjacent to the carbon nanotubes are composites of NiCo/MnO. The existence of the MnO phase could improve the impedance matching of the carbon nanotubes and NiCo metals, as well as form MnO-carbon and MnO-NiCo hetero nanointerfaces, which will lead to interface polarization loss.…”

“…The features of catalysts (e.g., metal composition, homogeneity, and number of active sites) have been proven to be the most critical factor for recycling efficiency in terms of the yield of CNCs and H2, as well as the quality of CNCs (e.g., aspect ratio and graphitic degree of CNTs) [2][3][4][5][6][19][20][21][22][23] . Non-noble transition metals (e.g., Fe, Co, and Ni) mixed with support materials (e.g., γ/α-Al2O3, SiO2, and zeolites) are the most widely used pre-catalysts due to the low cost, high catalytic activity and easy processability [2][3][4][5][6][19][20][21][22][23] . However, in pre-catalyst preparation the homogeneous mixing is challenging due to the poor compatibility between the transition metal and support, which decreases the catalytic activity.…”

“…Moreover, the precise engineering of the nano/microstructure (e.g., particle size, porosity, and specific surface area) of pre-catalysts via the traditional mixing method has been an unsurmountable challenge, which always results in dense structures and less active sites. To increase the accessible active sites of pre-catalysts, a commonly used way would make the supporting phase account for 90 wt.% of the catalyst [2][3][4][5][6][19][20][21][22][23][24][25][26] . Consequently, the resulting CNCs always possess large amounts of support materials and inferior functional properties, indicating a low commercial value of the CNCs products.…”

Multi-scale designed Co Mn3–O4 spinels: Smart pre-catalysts towards high-efficiency pyrolysis-catalysis recycling of waste plastics

“…Besides, incorporating a significant fraction of support materials always leads to a poor surface-area-to-volume ratio due to the dense structure and formation of catalyst/support materials interfaces. Hence, a high catalyst-to-feedstock ratio had to be employed in the thermocatalytic process (S. Table 1) [20] , which seriously limited the industrial application. Moreover, the incorporation of large amounts of support materials also complicated the purification process of CNTs from the CNCs after the conversion.…”

Graphene Oxide Facilitates Transformation of Waste PET into MOF Nanorods in Ionic Liquids

“…Despite the ease of incineration technique, the process is unsustainable and results in the release of greenhouse gases that pollute the environment. Controlled pyrolysis can transform waste PET into carbon materials such as graphite [5], graphene [6], carbon nanotubes [7,8], etc.…”