Studying the mechanisms of natural rubber pyrolysis gas generation using RMD simulations and TG-FTIR experiments

Highlights: • The pyrolysis process of natural rubber was studied at atomic level. • The reaction path models of gaseous products were established. • The combination simulation method was used to verify the accuracy of paths. -- Abstract: Based on pyrolysis technology, natural rubber can be converted to gases of high calorific value and then be used as fuels. In order to further explain the generation mechanisms of natural rubber pyrolysis gas, a combination of reaction molecular dynamics (RMD) simulations and thermogravimetry-infrared spectroscopy (TG-FTIR) experiments were used to study the pyrolysis process. The results show that the pyrolysis gases include CH₄, C₂H₄ and a small amount of C₃H₆ and C₄H₆. The TG-FTIR also shows the presence of CH₄ and functional groups (CH, CH₂, CH₃ and CC) in C₂H_4, C₃H₆ and C₄H₈. The kinetics data of each reaction which obtained based on the chain reaction mechanism and transition state theory, were input into Aspen Plus® process simulations to further get reasonable reaction path. The simulation results show that CH₃ separated from the main chain abstracts H from other molecules to generate CH₄, while C₂H₄ is mainly generated by the breaking of CC bonds on long chains. Other small gas molecules are generated by the breaking up of large olefins or free radicals with low activity. This study provides a theoretical basis for the recycling of pyrolysis gas and may ultimately help to increase the energy efficiency of the pyrolysis process.