Thermal Decomposition of Gaseous Ammonium Nitrate at Low Pressure: Kinetic Modeling of Product Formation and Heterogeneous Decomposition of Nitric Acid

Abstract

The thermal decomposition of ammonium nitrate, NH(4)NO(3) (AN), in the gas phase has been studied at 423-56 K by pyrolysis/mass spectrometry under low-pressure conditions using a Saalfeld reactor coated with boric acid. The sublimation of NH(4)NO(3) at 423 K was proposed to produce equal amounts of NH(3) and HNO(3), followed by the decomposition reaction of HNO(3), HNO(3) + M --> OH + NO(2) + M (where M = third-body and reactor surface). The absolute yields of N(2), N(2)O, H(2)O, and NH(3), which can be unambiguously measured and quantitatively calibrated under a constant pressure at 5-6.2 torr He are kinetically modeled using the detailed [H,N,O]-mechanism established earlier for the simulation of NH(3)-NO(2) (Park, J.; Lin, M. C. Technologies and Combustion for a Clean Environment. Proc. 4th Int. Conf. 1997, 34-1, 1-5) and ADN decomposition reactions (Park, J.; Chakraborty, D.; Lin, M. C. Proc. Combust. Inst. 1998, 27, 2351-2357). Since the homogeneous decomposition reaction of HNO(3) itself was found to be too slow to account for the consumption of reactants and the formation of products, we also introduced the heterogeneous decomposition of HNO(3) in our kinetic modeling. The heterogeneous decomposition rate of HNO(3), HNO(3) + (B(2)O(3)/SiO(2)) --> OH + NO(2) + (B(2)O(3)/SiO(2)), was determined by varying its rate to match the modeled result to the measured concentrations of NH(3) and H(2)O; the rate could be represented by k(2b) = 7.91 x 10(7) exp(-12 600/T) s(-1), which appears to be consistent with those reported by Johnston and co-workers (Johnston, H. S.; Foering, L.; Tao, Y.-S.; Messerly, G. H. J. Am. Chem. Soc. 1951, 73, 2319-2321) for HNO(3) decomposition on glass reactors at higher temperatures. Notably, the concentration profiles of all species measured could be satisfactorily predicted by the existing [H,N,O]-mechanism with the heterogeneous initiation process.

Thermal decomposition of ammonium nitrate

“…Park and Lin modeled the decomposition of AN at very low pressures (5‐6.2 Torr) using 115 reactions. The authors also conducted decomposition study experiments by pyrolysis/MS in a Saalfeld reactor.…”

“…Xu et al studied the reaction of AN with coal. They concluded that while the inorganic portion is nearly nonreactive with AN, the organic portion reacts readily.…”

Ammonium Nitrate Temperature‐Programmed Decomposition on Fe–Zeolite Catalysts: Effect of Deposition Method

“…[10][11][12][13][14][15][16][17][18][19] Yet, few studies have been done on the catalytic decomposition of AN. [20,21] Also, these studies were generally performed under static conditions.…”

Identification of Thermal Decomposition Products and Reactions for Liquid Ammonium Nitrate on the Basis of Ab Initio Calculation

“…Park and Lin and Skarlis et al have also proposed a decomposition path via NH 3 OH + as summarized in the following series of reactions:…”

“…In some energetic materials, the condensed phase reaction has the greatest effect on the combustion characteristics, and AN is included among these . Various reliable models of gas‐phase reactions have been proposed to date, all of which work to explain observed combustion behaviors . More recently, models for the liquid‐phase reactions of energetic salts have also been developed .…”