Carbon black production characteristics and mechanisms from pyrolysis of rubbers

Pyrolysis is a promising way to treat the waste tires for high value carbon black production. However, the carbon black formation mechanism is still unclear due to the complex decomposition and polymerization reactions during the pyrolysis of tire components. In this study, the production behavior, characters, and mechanism of carbon black from pyrolysis of natural rubber (NR), butadiene rubber (BR), and styrene-butadiene rubber (SBR) were investigated. The yield of carbon black was increased from 20.8%–24.4% to 47.9%–56.7% with the increase of pyrolysis temperature from 1100 to 1300°C. Although the carbon black production yield from NR was lower than that of BR and SBR at 1300°C, the graphitization degree (I_D/I_G = 2.22), microcrystal length (3.17 nm) and mean particle diameter (90.3 nm) of the carbon black derived from NR were the highest. The volatile evolution, carbon black nucleation mechanisms were revealed by reactive force-field molecular dynamics simulations. The pyrolysis of BR and SBR generated more C₂H₂, C₂H₃⋅, long carbon-chains and cyclic molecules than NR, which probably resulted in a higher carbon black yield than NR. With few defect borders, regular stacking and wrapping of the aromatic layers, the carbon black from NR exhibited more ordered nucleation and high graphitization degree.