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Recently,upcycling waste plastics into high-value-added carbonnanomaterials has attracted much attention; however, few studies havefocused on the conversion of waste plastics into graphene with highyield. Herein, we report a simple novel method to synthesize grapheneflakes (GFs) with high yield through catalytic carbonization of wastepolypropylene (PP) using organically modified montmorillonite (OMMT)as degradation catalyst and template at 700 °C. The yield, morphology,microstructure, phase structure, thermal stability, and surface elementcomposition of GFs were investigated. In addition, it was found thatOMMT not only promoted the degradation of waste PP into light hydrocarbonsand aromatics but also acted as template and catalyzed carbonizationof the light hydrocarbons and aromatics into GFs. At last, a possiblemechanism for the formation of GFs was put forward. This simple approachprovides a novel way to effectively prepare high-value-added GFs usingwaste plastics as carbon sources. [ABSTRACT FROM AUTHOR]

A one-potapproach was established to effectively convert polypropylene(PP) and linear low density polyethylene (LLDPE) into carbon nanomaterials(CNMs) including cup-stacked carbon nanotubes and carbon nanofibersunder the combined catalysis of HZSM-5/NiO or HZSM-5/Ni2O3at 700 °C. The effects of HZSM-5 content, a nickelcatalyst, and the carbon precursor on the morphology, microstructure,phase structure, and thermal stability of CNMs were investigated withscanning electron microscopy, transmission electron microscopy (TEM),high-resolution TEM, X-ray diffraction, Raman spectroscopy, and thermalgravimetric analysis. The effect of HZSM-5 content on the degradationproducts of PP and LLDPE was analyzed by gas chromatography and gaschromatography–mass spectrometry. With increasing HZSM-5 content,the yields of light hydrocarbons and aromatics increased due to protonacid sites on the surface of HZSM-5 catalyzing cracking of PP or LLDPEdegradation products. This one-pot approach provides a novel potentialway to largely transform mixed waste polyolefin into high value-addedCNMs. [ABSTRACT FROM AUTHOR]