Kinetic Mechanism for Simulating the Temperature and Pressure Effect on the Explosive Decomposition of Acetylene by ReaxFF Molecular Dynamics

Abstract

In the utilization of acetylene as the raw material in chemical engineering, understanding its pyrolysis mechanism is a vital issue in avoiding its explosion. The ReaxFF MD simulation was adopted to investigate the pyrolytic behavior of acetylene at various temperatures and pressures. The simulation results revealed that the pyrolysis mechanism of acetylene could be divided into three temperature ranges: (i) T < 1200 K, where homogenous molecular polymerization of acetylene occurs, producing polymerization products primarily C 4 H 4 and C 6 H 6 ; (ii) 1200 < T < 1800 K, where the free radical path competes with the molecular path, and free radicals such as C 2 H 3 * and C 4 H 3 * participate in the polymerization reaction; (iii) T > 1800 K, where the acetylene molecule is cracked, and H * and C 2 H * drive the formation of polyacetylene and hydrogen. Finally, a reaction network for the pyrolysis of acetylene to yield compounds below C 10 is generated through the identification, quantification, and evaluation of the reaction trajectory. The kinetic model of acetylene pyrolysis has been dramatically improved and supplemented, which is in satisfactory agreement with experimental values.