Reactive molecular dynamics simulation of cellulose thermal decomposition using ReaxFF

Abstract

This study focused on applying reactive molecular dynamics simulations to computer simulations of the pyrolysis reaction of cellulose, which is the main component of biomass. Reactive molecular dynamics simulations were performed using the ReaxFF package implemented within LAMMPS for large-scale parallel molecular dynamics calculations. The cellulose molecular model is composed of a total of 25,212 atoms using 6 cellulose chains formed by binding 1,4-β-D-glucopyranose at a degree of polymerization of 200. The cellulose molecular model used in the simulation was equilibrated to the final equilibrium conditions (500 K, 1 atm) by a predetermined method. Simulations were performed at seven relatively high temperatures (1000, 1300, 1500, 1800, 2000, 2300, 2500) in order to observe a sufficient pyrolysis reaction at a limited computational cost. In order to analyze the pyrolysis characteristics and reaction mechanism of cellulose by reaction molecular dynamics simulation, reaction products, formation behavior, and the dependence on simulation temperature was evaluated. The simulation results showed results that are consistent with the basic properties of cellulose for the pyrolysis reaction, which is well known in previous studies, in the reaction molecular dynamics simulation. In particular, cleavage of the glycosidic bond was a common reaction in the first step of cellulose, and it was found that the amount of C6 and C12 products produced was large. It was also suggested that C6 is a product derived from the glucose ring of cellulose, and that many of the important products from cellulose are produced through the cleavage of the glucose ring.