Highly accelerated kinetic Monte Carlo models for depolymerisation systems

• Novel kinetic Monte Carlo model reduces computation time by 3 orders of magnitude. • Secondary hydrocarbon yields accurately predicted for polystyrene pyrolysis. • Model captures entire product MWD without loss of structural detail. • Potential for optimising valuable hydrocarbon production. • Generalisable approach for accelerating kinetic depolymerisation models. Kinetic Monte Carlo (kMC) models are a well-established modelling framework for the simulation of complex free-radical kinetic systems. kMC models offer the advantage of discretely monitoring every chain sequence in the system, providing full accounting of the chain molecular weight distribution. These models are marred by the necessity to simulate a minimum number of molecules, which confers significant computational burden. This paper adapts and creates a highly generalizable methodology for scaling dilute radical populations in discrete stochastic models, such as Gillespie's Stochastic Simulation Algorithm (SSA). The methodology is then applied to a kMC simulation of polystyrene (PS) pyrolysis, using a modelling framework adapted from literature. The results show that the required number of simulated molecules can be successfully reduced by up to three orders of magnitude with minimal loss of convergent behaviour, corresponding to a wall-clock simulation speed reduction of between 95.2 to 99.6 % at common pyrolysis temperatures.