Mechanism analysis of gas products from catalytic pyrolysis of tire rubber based on reaction thermodynamics and kinetics

Abstract

In this paper, the gas products from pyrolysis of tire rubber was respectively studied by fixed bed pyrolysis experiments—gas chromatography analysis and molecular dynamics simulations. The results of experiments showed that the main gas products of pyrolysis were CH4, H2, and C2H4. The simulation results showed that the long rubber chain broke into four main rubber monomers at low temperature: isoprene, styrene, 1,3-butadiene and uncondensated C4H6·. And at higher temperature, the generated monomers were pyrolyzed into small molecule gases. Fe2O3 reduced the final pyrolysis temperature and increased the pyrolysis rate with a good catalytic reactively. And it changed the gas products distribution, in which the proportion of CH4 and H2 were promoted while the proportion of C2H4 was reduced. In order to obtain the thermodynamic and kinetic data of each reaction path, DFT calculation was carried out. The reaction paths of three major radicals H·, CH3·, and CH2 = CH· were further discussed. The results showed that Fe2O3(commercial) promoted the release of CH3· from isoprene monomer and CH3· attack on isoprene monomer and 1,3-butadiene to produce CH4. Moreover, Fe2O3 promoted H· attacking styrene monomer to generate H2.