A kinetic model for the autocatalytic behavior of nitric acid/formic acid mixtures to predict induction period

Prevention of runaway reactions is one of the ultimate goals of process safety engineering. However, the lack of knowledge for mechanism and kinetics of autocatalytic reactions enables to design safer processes handling reactive materials. The purpose of the present study was to accurately predict the induction period of autocatalytic reaction system composed by nitric acid and formic acid using a sophisticated kinetic model for the autocatalytic behavior. The reactions of nitric acid with organic compounds are autocatalytic and so can rapidly generate large amounts of heat and pressure without obvious warning signs. Thermal analyses were carried out using a reaction calorimeter while ion chromatography was employed to quantify reaction products. Exothermic reactions were observed to begin when the concentration of nitrous acid, which was identified as the autocatalyst, exceeded 4.6 +/- 1.2 mmol L-1. A kinetic model was determined as d[HONO]/dt = 2.62 x 1012exp(1.06 x 104/T)center dot[HNO3]2.5 +/- 0.1[HCOOH]1.8 +/- 0.1[HONO]1.9 +/- 0.1. This model was in good agreement with other results obtained from reaction calorimetry. (c) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.