Reaction Mechanism of Arsenic and Nitrogen Oxides in Coal Combustion

The reaction mechanism of arsenic and nitrogen oxides (N2O, NO2 and NO) was studied by using density functional theory of quantum chemistry B3LYP method. All parameters optimize the geometric configuration of each reactant, intermediate, transition state and product. The authenticity of intermediate and transition state is confirmed by frequency analysis, and the transition state is further determined by calculation of intrinsic reaction coordinate (IRC). In order to obtain more accurate energy information, the single point energy of each structure is calculated at B2PLYP level, and its reaction mechanism is deeply analyzed through kinetic parameters. The results show that the reaction energy barrier between arsenic and three nitrogen oxides (N2O, NO2 and NO) is 78.45, 2.58, 155.85kJ/mol respectively. At 298-1800 K, each reaction rate increases with the increase of temperature. Due to the low reaction energy barrier between arsenic and NO2, the reaction rate is greater than 1012 cm3/(mol s), indicating that the reaction is easy to occur and extremely fast. Arsenic reacts with N2O and NO at 298-900 K, and the reaction rate increases obviously with the increase of temperature. When the temperature rises further, its increasing trend slows down.