Gas products generation mechanism during co-pyrolysis of styrene-butadiene rubber and natural rubber

In this study, reaction molecular dynamics were combined with experiments to gain in-depth understanding of the gaseous pyrolysis products generation mechanism and optimal paths during natural rubber (NR), styrene-butadiene rubber (SBR) and mixed rubbers (NR-SBR) for effective recovery of waste rubber. The results show that the pyrolysis temperature of NR increases gradually with SBR addition. The monomers produced during the initial stage of SBR pyrolysis are mainly 1,3-butadiene and styrene, in which the energy barriers of the formed H and CH₂=CH in styrene are higher than those in 1,3-butadiene, and during further pyrolysis the main gas products are H₂ and CH₄. During co-pyrolysis of NR-SBR, the reaction paths show that increasing H₂ yield and decreasing CH₄ yield take place easily as SBR content rises. By contrast to pyrolysis of NR, the path of generating CH₂=CH in SBR is more difficult while that of CH₂=CH abstracting H occurred easily, leading to first enhancement in produced CH₂=CH₂ followed by a decline. Fixed bed experiments and gas chromatography (GC) analysis identify the main gas products of the three rubbers (NR, SBR, NR-SBR)as H₂, CH₄ and CH₂=CH₂ and the change of yield caused by the increase of SBR content are consistent with the simulation results.