Multiscale Simulation on Product Distribution from Pyrolysis of Styrene-Butadiene Rubber

Abstract

Pyrolysis of styrene-butadiene rubber receives renewed attention due to its application in tackling the waste tire disposal problem while allowing energy recovery. The density functional theory calculation (DFT) and ReaxFF molecular dynamics simulation (MD) are adopted to study the pyrolysis process with the variation of temperature and pressure. The bond dissociation energies of intramonomer and intermonomer bonds in trimers with different linking methods are calculated by DFT, where the bond with low energy tends to break during the pyrolysis process. The following MD simulation shows the pyrolysis product distribution of chain segments in styrene-butadiene rubber, where bond breaking positions in MD agree well with corresponding results in DFT and experiment. The next nearest neighbor bonds (single bonds) connected with double bond or benzene usually have lower dissociation energies than other single bonds and prone to break during the pyrolysis process. And thus, the intermonomer bonds tend to break at relatively low temperatures (around 650 K in experiment) prior to intramonomer bonds, which result in the emergence of monomers. With the temperature increase, intramonomer bonds are broken and thus large fragments are further pyrolyzed into small ones (e.g., C2 and C). Besides, the pressure strongly influences the product distribution, where high pressures promote the occurrence of secondary reactions.

Formation Mechanism of Monocyclic Aromatic Hydrocarbons during Pyrolysis of Styrene Butadiene Rubber in Waste Passenger Car Tires

“…Our previous work by ReaxFF MD simulation also found that the single bond connected with a double bond or benzene was easy to break. 22 …”

“…Our previous work by ReaxFF MD simulation also found that the single bond connected with a double bond or benzene was easy to break. 22 The other short-chain segment derived from the SBR chain was the alkene-like segment. This kind of segment was also unstable at high temperatures and would be further hydrogenated to short-chain structures, such as ethylene, propylene, and 1,3-butadiene et al 47 We adopted C 9 H 12 as the alkene-like segment model to simulate the breaking of the alkene chain.…”

“…Computer simulation has always played an indispensable role in the fields of materials and chemical engineering, especially for complex systems or processes that are difficult to carry out in experiment. , The calculation work related to the pyrolysis process and reaction mechanism of the waste tire system has reported in recent years, and most of the work is reactive force field (ReaxFF) molecular dynamics (MD) simulation. − The ReaxFF MD can efficiently study the product distribution of the pyrolysis process under different reaction conditions and provide theoretical guidance on the experiment . However, due to the lack of a set of dedicated ReaxFF parameters for the waste tire system, it is difficult to use this method to effectively study the reaction pathway of specific products.…”

Understanding the Self‐Healing Mechanism of Polyurethane Elastomer Based on Hydrogen Bonding Interactions through Molecular Dynamics Simulation

“…MD simulation is one of the tools which can study the mechanism and properties which cannot be analyzed in experiments. [25][26][27] He et al [28] studied the movement solution of the asphalt binder by MD simulation and found that the diffusion coefficient of the asphaltene molecule was the highest at 360 K. The microcrack was healed owing to nonbonded molecules which can produce van der Waals forces. Bertran et al [29] found the formation of hydrogen bonds because of strong intermolecular three-centered…”

The Viable Fabrication of Gas Separation Membrane Used by Reclaimed Rubber from Waste Tires

“…Rapid population growth and industrialization are responsible for the significant increase in production and accumulation of solid waste. Advances in the automobile industry and increased use of vehicular modes of transport have led to an increase in the number of waste tires [1]. Currently, the global annual consumption of tires is up to 1 billion units [2,3].…”