A kinetic study of the decomposition of HNO3 and its reaction with NO

The rate of reaction between NO and HNO3 and the rate of thermal decomposition of HNO3 have been measured by FTIR spectroscopy. The measurements were made in a teflon lined batch reactor having a surface to volume ratio of 14 m−1. During the experiments, with initial HNO3 concentrations between 2 and 12 ppm and NO concentrations between 2 and 30 ppm, a reactant stoichiometry of unity and a first order NO and HNO3 dependence were confirmed. The observed rate constant for the reaction at 22°C and atmospheric pressure was determined to 1.1 (±0.3) 10−5 ppm−1 min−1. At atmospheric pressure, HNO3 decomposes into NO2 and other products with a first order HNO3 dependence and with a rate constant of 2.0 (±0.2) 10−3 min−1. The apparent activation energy for the decomposition is 13 (±4) kJ mol−1.