Quantum chemical study of the O(~3P) interaction with poly aromatic hydrocarbons and heterogeneous CO_2 evolution under combustion conditions

摘要

Reactions of aliphatic and aromatic hydrocarbons with ground state (~3P) atomic oxygen are very important in combustion processes, atmospheric chemistry, and photochemical contamination. In this study we evaluate two paths of the reaction of large polyaromatic hydrocarbons with O(~3P) using quantum chemical calculations. A systematic analysis of the O-addition and H-abstraction reactions by atomic oxygen O(~3P) with a series of aromatic hydrocarbons (benzene, naphthalene, anthracene, phenanthrene, pyrene and naphthacene) was carried out using the Density Functional Theory method. Thermal rate constants were calculated for each elementary reaction and used to estimate the total rate constants. The results predict that O-addition is more dominant at almost all temperatures of the combustion systems for each one of the hydrocarbons evaluated. One of the main results of the O-addition reactions is the evolution of heterogeneous CO_2 mainly by two paths which can explain how some of the experimentally observed CO_2 is formed. It was suggested to consist of four main steps, namely: 1) adsorption of an oxygen atom; 2) insertion of the adsorbed O atom into the ring; 3) rearrangement to form a five-member ring; and 4) desorption of CO_2.