The urea decomposition in the process of the heterogeneous catalytic denitration of nitric acid solutions: Part I. Kinetics of the reaction

Kinetics of the urea catalytic decomposition reaction in the system (NH2)2CO–HNO3–HCOOH were studied in the presence of the catalyst 1% Pt/SiO2. shown that a platinum catalyzed decomposition of urea in 2–8 M HNO3 proceeds in the presence of 0.2–1.5 M formic acid as a result of the reaction with nitrous acid generated in the process of catalytic denitration. The decomposition proceeds according to a “zero”-order with respect to the urea concentration and exhibits an induction period for [HNO3]<2.5 M. The order of the process with respect to [HCOOH] is 1. The rate of reaction decreases when the concentration of nitric acid is increased that is explained by the hydrogen ions competitive adsorption on the catalyst’s surface. The rate-determining step of the urea catalytic decomposition is a reaction of heterogeneous catalytic formation of nitrous acid. found that an activity of the Pt/SiO2 catalyst decreases reversibly with the increase of the drying temperature during its regeneration.