Decomposition Of Hydroxylamine Research Articles

A detailed kinetic model for the thermal decomposition of hydroxylamine

Hydroxylamine may decompose explosively if processed and stored in certain conditions, posing critical safety issues that need to be carefully addressed. A key aspect is related to the characterization of chemical aspects involved in the explosive decomposition of hydroxylamine (HA), requiring accurate and detailed kinetic mechanisms. This work was devoted to the experimental and numerical characterization of the thermal decomposition of aqueous solutions of HA included in the range of 10%w to 50%w. The onset temperatures of thermal decomposition were determined in the range of 143–198 °C under heating rates of 2 and 5 °C min–1, respectively. A reduced mechanism listing 13 species and 11 reactions involving nitrogen-containing species was produced and validated against experimental measurements. Reaction pathways ruling the decomposition of HA were identified. The hydrogen abstraction toward HNOH and H2NO dominates the primary steps of NH2OH decomposition. The generated mechanism was adopted for the definition of a dimensionless stability diagram for the safe use of HA. Finally, results show a self-accelerating behaviour for any temperature larger than 186 °C, defining a monitoring criterion for safe storage of hydroxylamine-solutions.

Orthophosphate enhances N2O production from aerobic hydroxylamine decomposition: implications to N2O emissions from nitrification in ornithogenic and manure-fertilized soils

Soils affected by animal wastes have simultaneously high N and P contents. Despite the reports of high nitrous oxide (N2O) emissions in such environments, the role that P plays in N2O dynamics has not yet been systematically investigated. Here, we report the enhancement effect of orthophosphate (PO43−-P) abundance on N2O yields from abiotic NH2OH decomposition, which may have substantial implications to N2O emissions from nitrification in such P-rich soils. The axenic cultures of Nitrosomonas europaea, an ammonia-oxidizing bacterium previously reported to leak NH2OH, exhibited significantly higher N2O yields when incubated at higher PO43−-P concentrations. As NH4+-to-NO2− turnover and growth rates were unaffected even at the highest PO43−-P concentration examined, the abiotic interaction between extracellularly released NH2OH and PO43−-P was the most plausible mechanism of enhanced N2O emission in these nitrifier cultures. This proposed mechanism was supported by the results of abiotic NH2OH incubation whereby higher PO43−-P concentration resulted in higher N2O yield. Orthophosphate enhancement of NH2OH-to-N2O turnover was then simulated with addition of 5 μmol NH2OH to an ornithogenic soil with high PO43−-P content (23.9 ± 6.7 g/kg wet soil) and active nitrification activity after sterilization. The N2O yield, 69.0 ± 4.6%, was significantly higher than the N2O yields for other examined soils with lower PO43−-P contents (0–1.94 g/kg wet soil), and the PO43−-P contents of the examined soils exhibited strong correlation with the N2O yields. These findings suggest that N2O production from nitrification via abiotic turnover of released NH2OH may be a consequential mechanism of N2O emissions in PO43−-P-rich soils.

Thermal decomposition of hydroxylamine in aqueous solutions in the presence of NaCl, KCl or Na2SO4 in the temperature range 120 °C–140 °C

The thermal decomposition of hydroxylamine aqueous solutions in two different concentrations and three temperatures was studied in the presence of NaCl, KCl and Na2SO4 using isoperibolic calorimetry. The purpose of this study was to generate data for comparison of the thermal decomposition of different nitrogen containing compounds towards the ultimate, long-term goal to reveal the decomposition pathways of nitrogen containing species and to pinpoint the factors affecting these paths. It was found that Na2SO4 was substantially reducing hydroxylamine decomposition rate, while the other two inorganic salts had a non-measurable effect on hydroxylamine decomposition rate. When NaCl and Na2SO4 were used together the effect of the latter predominated. In all cases the non-condensable gas generation was not practically affected by the presence of any of the additives. The results were compared with the effect that KCl and Na2SO4 had on ammonium nitrate thermal-decomposition rate and similarities and differences are discussed. It is believed that rate deceleration effects of Na2SO4 are owing to the alkaline character of SO42− anion.

Catalytic Decomposition of Hydroxylammonium Nitrate Ionic Liquid: Enhancement of NO Formation.

Hydroxylammonium nitrate (HAN) is a promising candidate to replace highly toxic hydrazine in monopropellant thruster space applications. The reactivity of HAN aerosols on heated copper and iridium targets was investigated using tunable vacuum ultraviolet photoionization time-of-flight aerosol mass spectrometry. The reaction products were identified by their mass-to-charge ratios and their ionization energies. Products include NH3, H2O, NO, hydroxylamine (HA), HNO3, and a small amount of NO2 at high temperature. No N2O was detected under these experimental conditions, despite the fact that N2O is one of the expected products according to the generally accepted thermal decomposition mechanism of HAN. Upon introduction of iridium catalyst, a significant enhancement of the NO/HA ratio was observed. This observation indicates that the formation of NO via decomposition of HA is an important pathway in the catalytic decomposition of HAN.

Combined experimental and kinetic modeling approaches of ammonium nitrate thermal decomposition

This experimental and modeling study aimed at better understanding the impact of the operating conditions on the interplay between ammonium nitrate (AN) decomposition pathways and their coupling with gas-phase chemistry. Experimental analysis and kinetic modeling were combined to elucidate the role of operating conditions on ammonium nitrate thermal decomposition. A new condensed-phase semi-detailed kinetic mechanism was developed and validated against original experiments performed in this study and experiments from other groups. This mechanism was coupled to a gas-phase mechanism, making it possible to quantify the contributions of condensed-phase and gas-phase reaction pathways to AN thermal decomposition at different heating rates. The study revealed that T50 (temperature at 50% conversion) increases strongly with the heating rate, favoring highly activated reactions. Even at typical burning surface temperatures (350 °C), gas-phase reactions involving nitramide and nitric acid play a significant role. The thermal deNOx pathway and hydroxylamine decomposition impact significantly NH3 consumption in the monopropellant flame zone.

Distinctions of hydroxylamine formation and decomposition in cyclohexanone ammoximation over microporous titanosilicates

A comprehensive investigation has been carried out to study hydroxylamine formation and decomposition in the ammoximation of cyclohexanone over three typical microporous titanosilicates, Ti-MOR, Ti-MWW, and TS-1. Cyclohexanone ammoximation involved the formation and decomposition of hydroxylamine intermediate as well as noncatalytic oximation. Ti-MOR and TS-1 were found to be extremely effective catalysts for hydroxylamine formation by ammonia oxidation with hydrogen peroxide; meanwhile, they showed low catalytic activity for hydroxylamine decomposition. Thus, Ti-MOR and TS-1 were capable of achieving high hydroxylamine yields such as 82.7–95.1% and cyclohexanone conversion of >97%. Serving as an effective ammoximation catalyst, however, Ti-MWW was less efficient for hydroxylamine formation because of its high catalytic activity for the decomposition of hydroxylamine. Ion exchange with alkali metal cations has been carried out on titanosilicates to remove the hydroxyl-related acid sites. Introduction of alkali cations by ion exchange removed the acid sites of titanosilicates selectively, resulting in enhanced activity for hydroxylamine formation and ammoximation without altering the hydroxylamine decomposition, and the exchange then enhanced their catalytic activity significantly for both hydroxylamine formation and ammoximation.

Thermal decomposition of hydroxylamine: Isoperibolic calorimetric measurements at different conditions

Thermal decomposition of hydroxylamine, NH2OH, was responsible for two serious accidents. However, its reactive behavior and the synergy of factors affecting its decomposition are not being understood. In this work, the global enthalpy of hydroxylamine decomposition has been measured in the temperature range of 130–150°C employing isoperibolic calorimetry. Measurements were performed in a metal reactor, employing 30–80ml solutions containing 1.4–20g of pure hydroxylamine (2.8–40g of the supplied reagent). The measurements showed that increased concentration or temperature, results in higher global enthalpies of reaction per unit mass of reactant. At 150°C, specific enthalpies as high as 8kJ per gram of hydroxylamine were measured, although in general they were in the range of 3−5kJg−1. The accurate measurement of the generated heat was proven to be a cumbersome task as (a) it is difficult to identify the end of decomposition, which after a fast initial stage, proceeds very slowly, especially at lower temperatures and (b) the environment of gases affects the reaction rate.

Reduction of Pu(IV) and Np(VI) with hydroxylamine in solutions of low acidity with high uranium content

Decomposition of hydroxylamine in HNO3 solutions containing 350 to 920 g l−1 U(VI) was studied. In the absence of fission and corrosion products (Zr, Pd, Tc, Mo, Fe, etc.), hydroxylamine is stable for no less than 6 h at [HNO3] < 1 M and 60°C. In the presence of these products, the stability of hydroxylamine appreciably decreases. The reduction of Pu(IV) and Np(VI) with hydroxylamine in aqueous 0.33 and 0.5 M HNO3 solutions containing 850 g l−1 U(VI) and fission and corrosion products at 60°C was studied. Np(VI) is rapidly reduced to Np(V), after which Np(V) is partially reduced to Np(IV). The rate of the latter reaction in such solutions is considerably higher than the rate of the Np(V) reduction with hydroxylamine in HNO3 solutions without U(VI). At [HNO3] = 0.33 M, the use of hydroxylamine results in the conversion of Pu to Pu(III) and of Np to a Np(IV,V) mixture, whereas at [HNO3] = 0.5 M the final products are Pu(IV) and Np(V).

Formation of hybrid N2O in a suspended soil due to co‐denitrification of NH2OH

AbstractA few studies have shown that amine compounds (e.g., hydroxylamine) can be co‐metabolically introduced into the reaction pathway of denitrification. During this microbial process, the N atom of the amine species is bound to a N atom of nitrite. In case of hydroxylamine, this concomitant reaction ultimately results in the formation of hybrid N2O. Due to its co‐metabolic character the process has been termed co‐denitrification. Hybrid N2O production during co‐denitrification has been proven to occur in prokaryotic (e.g., Pseudomonas sp.) as well as eukaryotic (e.g., Fusarium sp.) species. Many of them are already well‐known as common denitrifiers. However, until now no clear evidence has been provided to show that N2O production by co‐denitrification really takes place in a soil. In the present study, a formation of hybrid N2O was revealed by an adapted 15N‐tracer model, when both hydroxylamine and 15N‐nitrate were applied (mol ratio 10:1) to an anaerobically incubated soil suspension from a Haplic Chernozem. The presence of hybrid N2O was also indicated by a novel characteristic factor (Rbinom) developed for a hybrid‐N‐N‐gas detection. By contrast, no hybrid N2O was found when either an autoclaved soil suspension, only nitrate or only hydroxylamine was used. Thus, it appears that hybrid‐N2O formation occurred due to co‐denitrification of hydroxylamine. Hence, this is the first study which demonstrates hybrid‐N2O production by co‐denitrification beyond a microbial species level. The 15N‐tracer model revealed that under the given experimental conditions N2O production by co‐denitrification prevailed against N2O from denitrification and abiotic hydroxylamine decomposition. In addition, a formation of hybrid N2 was also calculated by the model. However, the experimental results lead to the conclusion that it was most likely caused by a reduction of hybrid N2O due to conventional denitrification.

Simple Reaction Conditions for the Formation of Ketonitrones from Ketones and Hydroxylamines

The condensation of ketones and hydroxylamines to form ketonitrones was reinvestigated by using thermal conditions previously found to minimize hydroxylamine decomposition (t-BuOH, 110 degrees C). This simple approach allows the formation of exocyclic, acyclic, and alpha,beta-unsaturated ketonitrones with benzylic, linear, and branched nitrogen substituents in modest to excellent isolated yields.

Thermal Behavior of Aqueous Solutions of Hydroxylamine During Isothermal and Isoperibolic Decomposition in a Closed System

Hydroxylamine (HA) has been independently involved in several tragic accidents, which incurred numerous fatalities and injuries. Following these incidents, adiabatic calorimetry and computational chemistry research was conducted, suggesting potential reaction pathways of HA decomposition, but the mechanism of HA behavior still has not been completely understood. In the present work, the thermal decomposition of hydroxylamine was studied via isothermal and isoperibolic calorimetric measurements in a glass and in a metal reactor, respectively. Identification of stable intermediates, like ammonia, nitrates, or nitrites during the course of the reaction did not provide any conclusive results. The calorimetric measurements presented here show condition-dependent endothermic and exothermic reaction steps that are consistent with previous findings of computational chemistry. These findings corroborate previously reported results, according to which the NH2− moiety may trigger reaction runaway.

Isothermal decomposition of hydroxylamine and hydroxylamine nitrate in aqueous solutions in the temperature range 80–160 °C

Hydroxylamine (HA) and hydroxylamine nitrate (HAN) have been involved independently in several tragic accidents, which incurred numerous fatalities and injuries. Following these incidents, adiabatic calorimetry and computational chemistry research was conducted on those compounds, suggesting potential reaction pathways of their decomposition, but the mechanism of their unstable behavior, still have not been completely understood. In the present work, isothermal decomposition tests were performed accompanied with HPLC, ion chromatography and UV analyses in the temperature range 80–160 °C. Condition-dependent autocatalytic decompositions were demonstrated for HA and HAN, and an intermediate formation has been observed that is most likely responsible for their autocatalytic behavior. These findings corroborate previously reported computational chemistry results.

Sodium metavanadate catalyzed one-step amination of benzene to aniline with hydroxylamine

The direct amination of benzene to aniline with hydroxylamine catalyzed by sodium metavanadate in acetic acid water under mild conditions took place more efficiently in open air than in a closed system. The presence of oxygen significantly enhanced the yield of aniline. Satisfactory aniline yield (64%) and turnover number (48 mol of aniline per mol of vanadium) were obtained under optimized reaction conditions. The decomposition of hydroxylamine was studied to understand its function during the amination process. A computational study on the UV–vis spectra of some typical vanadium complexes was carried out by the time-dependent DFT method. A free-radical mechanism is proposed based on the results of EPR, 51V NMR, and UV–vis characterizations.

Calorimetric study on the decomposition of hydroxylamine in the presence of transition metals

Hydroxylamine (HA), hydroxylamine chloride (HAC1), and hydroxylamine nitrate (HAN) were each mixed with aqueous solutions of Cr 3+, Cr 6+, Mn 7+, Co 2+, Co 3+, and Cu 2+, and their heat flow profiles were monitored by a small-scaled reaction calorimeter, SuperCRC. These mixing tests demonstrated that HA was less reactive than HACl and HAN with Mn 7+ and Cr 6+. Their UV–vis spectra confirmed that the substrates reacted when Mn 7+ and Cr 6+ were reduced. HA was more reactive with Cu 2+ than HAC1 and HAN and exhibited the highest reactivity among the three substrates with regard to metals in the intermediate oxidation states: Cr 3+, Co 3+, and Co 2+. During the reaction of HA and Co 3+, an induction period was observed. All exothermic reactions were accompanied by precipitation or a change in the UV–vis spectra.

Effect of Iron Ion in the Thermal Decomposition of 50 mass % Hydroxylamine/Water Solutions

This paper presents thermal decomposition behavior of 50 mass % hydroxylamine/water solutions (HA) when contacted with iron in the form of ferric oxide, ferrous ion, and ferric ion. If HA comes in contact with iron ion (Fe3+ or Fe2+), even in small concentrations and at ambient temperatures, it reacts violently to produce a bubbling system with very little vapor−liquid disengagement. A great amount of energy, ∼4.0 kJ/g, is released, in a very short period of time, which results in boiling of the reaction mass. The measured heat of reaction for hydroxylamine without iron ion was 3.78 kJ/g. Rust causes heterogeneous iron catalysis of the reaction, which is not as violent as homogeneous iron catalysis, where even 0.0004 mol % (10 ppm) of iron ion added at room temperature will under adiabatic conditions trigger the complete decomposition of hydroxylamine.

Study on decomposition of hydroxylamine/water solution

Abstract The risk evaluation of decomposition of hydroxylamine(HA)/water solution was studied experimentally. The thermal property of HA/water solution was studied from the calorimetric data obtained using the differential thermal analysis (DTA). The intensity of decomposition was studied on the basis of the results of the mini closed pressure vessel test (MCPVT) and the pressure vessel test (PVT) in addition to the steel tube test. The thermal property of HA/water solution was evaluated on the basis of results of the DTA. The heat-release onset temperatures using the no-treated stainless steel cells were more than 70 K below those measured using the GSC. This result implies that the heat-release onset temperature depends on the materials of sample cell. On the other hand, the heat of reaction did not depend on the materials of sample cell. The intensity of the thermal decomposition was investigated on the basis of results of the MCPVT, the PVT and the steel tube test. The intensity of the thermal decomposition increased as the HA concentration increased in the MCPVT. The intensity of the thermal decomposition increased greatly when the HA concentration was beyond 80wt.% in the MCPVT. It was elucidated that the thermal decomposition of HA 70wt.%/water solutions was very violent in the PVT. In addition, HA/water solutions of more than 80wt.% concentration could detonate in the steel tube test. HA 80 wt.% water/solution was easily detonated by a detonator without RDX in the steel tube test. In addition, the decomposition hazard of HA/water solution by the metal ion and the iron powder was studied in this paper. The thermal stability of HA85%/water solution with the iron ion or the iron powder was discussed on the basis of the heat-release onset temperature by the DTA. The heat-release onset temperatures decreased when the concentration of the iron ion or the iron powder increased in the DTA measurements. The reactiveness of HA/water solution with the metal ion of iron, manganese, nickel, chromium and copper was examined by measuring the mass loss of HA/water solution after the metal ion was added to HA/water solution at room temperature. The reactiveness of HA/water solution with the iron powder was also studied in this paper. The ferrous ion, the ferric ion and the iron powder reacted with HA/water solution. Ignition automatically began when the 0.2wt.% ferric ion solution was added to HA85wt.%/water solution. The mass loss rate depended on the HA concentration greater than the iron ion concentration. The mass loss rate increased when an amount of the iron powder increased. On the other hand, the decomposition reaction of HA85wt.%/water solution with Cu2+ was calm compared to that of the iron ion. HA/water solution did not react with Mn2+, Ni2+ and Cr3+ at room temperature.

Effect of air in the thermal decomposition of 50 mass% hydroxylamine/water

This paper presents experimental measurements of 50 mass% hydroxylamine (HA)/water thermal decomposition in air and vacuum environments using an automatic pressure tracking adiabatic calorimeter (APTAC). Overall kinetics, onset temperatures, non-condensable pressures, times to maximum rate, heat and pressure rates versus temperature, and mixture vapor pressures for the experiments in vacuum were similar when compared to the corresponding data for HA decomposition in air. Determined was an overall activation energy of 119±8 kJ/mol (29±2 kcal/mol), which is low compared to 257 kJ/mol (61.3 kcal/mol) required to break the H 2NOH bond reported in the literature. The availability of oxygen from air did not affect detected runaway decomposition products, which were H 2, N 2, N 2O, NO, and NH 3, for samples run in vacuum or with air above the sample. A Δ H rxn of −117 kJ/mol (28 kcal/mol) was estimated for the HA decomposition reaction under runaway conditions.

Nitric oxide generation from hydroxylamine in the presence of neutrophils and in the cell-free system.

Conversion of hydroxylamine (HA) to nitric oxide (NO) has been studied in the presence or absence of human neutrophils with or without myristate acetate phorbol (PMA), catalase (CAT), hydrogen peroxide (H2O2), and superoxide dismutase (SOD) and nitric oxide synthase (NOS) inhibitors. The generation of NO from HA in the presence of neutrophils was higher than in the cell-free system. We found that catalase did not influence the nitrite generation from HA in the cell-free system and in the presence of neutrophils. The H2O2 enhanced the NO generation from HA in the presence of neutrophils only. When catalase and H2O2 were added together, a high increase of NO generation from HA in both systems was observed. The addition of SOD decreased whereas addition of PMA enhanced the NO generation from HA in the presence of neutrophils. The presented data show the possible role of oxygen radicals in the decomposition of HA to NO. The addition of NOS inhibitors to the culture of neutrophils decreased the generation of nitrite from HA. Our results suggest that NO generation from HA, which is an intermediate in NO production from L-arginine, may be supported by an enzymatic pathway in which cellular NO synthase is involved.

Nitric oxide generation from hydroxylamine in the presence of neutrophils and in the cell‐free system

Conversion of hydroxylamine (HA) to nitric oxide (NO) has been studied in the presence or absence of human neutrophils with or without myristate acetate phorbol (PMA), catalase (CAT), hydrogen peroxide (H2O2), and superoxide dismutase (SOD) and nitric oxide synthase (NOS) inhibitors. The generation of NO from HA in the presence of neutrophils was higher than in the cell‐free system. We found that catalase did not influence the nitrite generation from HA in the cell‐free system and in the presence of neutrophils. The H2O2 enhanced the NO generation from HA in the presence of neutrophils only. When catalase and H2O2 were added together, a high increase of NO generation from HA in both systems was observed. The addition of SOD decreased whereas addition of PMA enhanced the NO generation from HA in the presence of neutrophils. The presented data show the possible role of oxygen radicals in the decomposition of HA to NO. The addition of NOS inhibitors to the culture of neutrophils decreased the generation of nitrite from HA. Our results suggest that NO generation from HA, which is an intermediate in NO production from L‐arginine, may be supported by an enzymatic pathway in which cellular NO synthase is involved.

The Chemistry of the Hydrazine–Hydroxylamine–Nitric Acid System at High Temperatures

The kinetics of decomposition of hydrazine and hydroxylamine in concentrated nitric acid at 70 °C establish a critical concentration [hydrazine] ≍ 5 × 10−4 mol dm−3 below which a rapid autocalalytic decomposition of hydroxylamine occurs; this corresponds to the rate of nitrite scavenging by hydrazine balancing the rate of N2O4 formation.