Modeling Chemical Incompatibility: Ammonium Nitrate and Sodium Salt of Dichloroisocyanuric Acid as a Case Study

Abstract

Modeling chemical incompatibility : the ammonium nitrate and sodium salt of dichloroisocyanuric acid as a case study. AbstractThe dramatic accident involving ammonium nitrate (AN) that took place at Toulouse in September 2001 has once again focused attention on the hazards pertaining to chemical incompatibility in industrial environment. To complete the experimental results, a detailed theoretical study was performed in order to better understand the involved mechanisms, considering the reaction between ammonium nitrate and the sodium salt of dichloroisocyanuric acid (SDIC). Starting from theoretical results obtained for the pure reactants, the gas-phase decomposition mechanism of the mixture was investigated and fully characterized by means of Density Functional Theory (DFT) calculations. Beyond the complete characterization, in terms of intermediate structures and energies, of the decomposition pathways, our results evidenced as anticipated the role of water in catalyzing the decomposition reaction, through a significant decrease of the activation energy of the rate determining step. These results, in qualitative agreement with the calorimetric experiments, pointed out the instability of the AN-SDIC wet mixture and the underpinning incompatibility mechanism between these two chemicals.

Theoretical and Experimental Study of the Reaction between Ammonium Nitrate and Sodium Salts

“…Role of the water on AN-NaNO2 reaction Sodium nitrite and AN are two extremely hygroscopic salts and in the experimental protocol samples were not subjected to complete drying. But water could have a strong influence on decomposition mechanisms, as demonstrated for the AN-SDIC incompatibility 20 . Therefore, water was introduced in the theoretical model to simulate the experimental conditions and to better understand the reaction mechanism between sodium nitrite and nitric acid.…”

“…Therefore, water was introduced in the theoretical model to simulate the experimental conditions and to better understand the reaction mechanism between sodium nitrite and nitric acid. At first, the effect of a water molecule on the transition state was considered (see Figure 2), as done for the AN-SDIC mixture 20 . As shown in Figure 3 In order to have a clearer idea of the role of water, solvent bulk effects were also added using the PCM approach on both the AN-NaNO2 dimer, and the AN-NaNO2-H2O trimer.…”

“…[13][14][15] Indeed, such an incompatibility between AN and the sodium salt of dichloroisocyanurate (SDIC) has been demonstrated experimentally by calorimetric analysis [16][17] and more recently by theoretical simulations. [19][20][21] The focus of the present work is to study the incompatibility of AN towards two process chemicals, pure sodium nitrite (NaNO2) and sodium nitrate (NaNO3), using a combined experimental and theoretical approach. These chemicals are used in the manufacture of water-in-oil ammonium nitrate emulsion (ANE) explosives 22 and large quantities of these sodium salts may be present in the industrial environment.…”

“…In a similar way, this work aims to clarify the potential incompatibility of AN with sodium salts NaNO2 and NaNO3 using a combined experimental and theoretical approach based on calorimetric analysis and the DFT approaches. Our previous detailed work on the chemical incompatibility between AN and SDIC 20 suggested that through the analysis of the rate determining step, the reaction between ammonia and nitric acid in the presence of sodium salts already provides valuable information on the presence (or absence) of a chemical incompatibility. Following this indication, the present DFT work will be focused only on the evaluation of different chemical factors on the energetics of the rate-determining step of the reaction mechanism between AN and sodium salts in order to identify the presence of a chemical incompatibility.…”

Nitrogen‐Based Alternative Fuels: Progress and Future Prospects

“…This evaluation is specifically essential for aqueousU AN for two reasons: (a) it contains an nitrogenous species with high energy content (i.e., AN) that could potentially pose safety risks [86] and (b) it is am onofuel in which the oxidizing and the reducing species are in constant contact. First, aqueous UANh as ar elatively low vapor pressure,o fa bout 1.5 kPa at 20 8C, similar to the vapor pressureo fasaturated aqueousA Ns olution.…”