Dynamics Of HOCO+H₂O Collision Under Combustion Condition

O₂/H₂O-fuel combustion technology is considered a promising technology,which can reduce effectively carbon dioxide emissions.And the presence of water molecule could have kinetic and dynamic effects on combustion reactions.The reaction OH+CO?CO₂+H is the final oxidation step for all hydrocarbon fuels,and it contributes to the control of atmospheric hydroxyl radical?OH?concentration and producing the carbon dioxide?CO₂?from carbon monoxide?CO?.Since the HOCO radical is a key intermediate produced in atmospheric and combustion processes,it is extremely significant to understand its reactions with H₂O.How the water molecule influences the behavior of HOCO,involving in chemical reaction or serving as a highly efficient third body,has been an interesting topic.The potential energy surface of the HOCO+H₂O system was established first using the M06-2X/aug-cc-pVDZ method.There are five possible open endothermic product channels.There are three reaction channels to generate CO₂+H+H₂O,which contains one H atom-transfer channel and two cis-trans isomerization channels;and there are two reaction channels to generate CO+OH+H₂O.Both product channels are endothermic,therefore,the product may not be easily formed.The barrier of the product channel for generating CO+OH+H₂O is lower than generating CO₂+H+H₂O,therefore the reaction has more chances to generate to the CO+OH+H₂O.it is obvious that the H₂O does not participate in the formation and breaking of bonds in the formation of the products which only affect the reaction by forming hydrogen bonds to form HOCO—H₂O complex.In the dynamics calculations,we have sampled four vibrational temperature points from 2839 to 3439 K.At these temperatures,the HOCO is in a vibration excited state.A total of 400 trajectories(100 trajectories at each given T_vib)were run at M06-2X/aug-cc-pVDZ.A total of 12 reaction channels were discovered.In this paper,the specific reaction process and reaction probability of 12 reaction channels are presented in detail,and compared with the potential energy surface.Under such simulation conditions,57%-74%of HOCO radical is stable before collision with H₂O.the reactive probability is much low?No more than 7%?.The energy distribution analysis of the trajectory is performed in all trajectories where no reaction occurs.It is found that after the collision between HOCO and H₂O,the vibrational energy of HOCO is reduced,and the vibrational energy and rotational energy of H₂O are increased,and the translational energy is also slightly increased.This indicates that the vibration energy of HOCO is transferred to the H₂O and translational energy of the reaction.In addition,there are some meaningful dynamic behaviors found in trajectory simulations.including direct mechanism and indirect mechanism.At the same time,the distribution of product scattering angle under different mechanisms was calculated to prove the accuracy of the mechanism.From the potential energy surface and simulation results,we can conclude that H₂O hardly participates in the formation and breaking of bonds in the formation of the products which only affect the reaction by forming hydrogen bonds to form HOCO—H₂O complex.At the same time,it is proved by the product energy distribution that the energy of HOCO is transferred to H₂O and Translational energy.Therefore,H₂O plays a role of collision and Energy transfer in this system.