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.