Thermal Decomposition Of Hydrazine Research Articles

Large Intermediates in Hydrazine Decomposition: A Theoretical Study of the N3H5 and N4H6 Potential Energy Surfaces.

Large complex formation involved in the thermal decomposition of hydrazine (N2H4) is studied using transition state theory-based theoretical kinetics. A comprehensive analysis of the N3H5 and N4H6 potential energy surfaces was performed at the CCSD(T)-F12a/aug-cc-pVTZ//ωB97x-D3/6-311++G(3df,3pd) level of theory, and pressure-dependent rate coefficients were determined. There are no low-barrier unimolecular decomposition pathways for triazane (n-N3H5), and its formation becomes more significant as the pressure increases; it is the primary product of N2H3 + NH2 below 550, 800, 1150, and 1600 K at 0.1, 1, 10, and 100 bar, respectively. The N4H6 surface has two important entry channels, N2H4 + H2NN and N2H3 + N2H3, each with different primary products. Interestingly, N2H4 + H2NN primarily forms N2H3 + N2H3, while disproportionation of N2H3 + N2H3 predominantly leads to the other N2H2 isomer, HNNH. Stabilized tetrazane (n-N4H6) formation from N2H3 + N2H3 becomes significant only at relatively high pressures and low temperatures because of fall-off back into N2H3 + N2H3. Pressure-dependent rate coefficients for all considered reactions as well as thermodynamic properties of triazane and tetrazane, which should be considered for kinetic modeling of chemical processes involving nitrogen- and hydrogen-containing species, are reported.

Evaluation of nitrogen containing reducing agents for the corrosion control of materials relevant to nuclear reactors

Materials undergo enhanced corrosion in the presence of oxidants in aqueous media. Usually, hydrogen gas or water soluble reducing agents are used for inhibiting corrosion. In the present study, the feasibility of using alternate reducing agents such as hydrazine, aqueous ammonia, and hydroxylamine that can stay in the liquid phase was investigated. A comparative study of corrosion behavior of the structural materials of the nuclear reactor viz. carbon steel (CS), stainless steel (SS-304 LN), monel-400 and incoloy-800 in the oxidizing and reducing conditions was also made. In nuclear industry, the presence of radiation field adds to the corrosion problems. The radiolysis products of water such as oxygen and hydrogen peroxide create an oxidizing environment that enhances the corrosion. Electrochemical studies at 90 °C showed that the reducing agents investigated were efficient in controlling corrosion processes in the presence of oxygen and hydrogen peroxide. Evaluation of thermal stability of hydrazine and its effect on corrosion potential of SS-304 LN were also investigated in the temperature range of 200–280 °C. The results showed that the thermal decomposition of hydrazine followed a first order kinetics. Besides, a change in electrochemical corrosion potential (ECP) was observed from −0.4 V (Vs SHE) to −0.67 V (Vs SHE) on addition of 5 ppm of hydrazine at 240 °C. Investigations were also made to understand the distribution behavior of hydrogen peroxide and hydrazine in water-steam phases and it was found that both the phases showed identical behavior.

Stability of Hydrazine, Morpholine and Ethanolamine at 275 °C and In Situ Measurement of Redox and Acid–Base Properties

The hydrothermal reduction of nitrogen is important in several fields. Hydrazine and amines are injected in the secondary circuit of the pressurized water reactors (PWR) nuclear plants to minimize materials corrosion. Amines are also possible reactants in the nitrogen chemistry of submarine hydrothermal vents. To better evaluate the chemical properties of N-bearing hydrothermal solutions, experiments have been carried out at 275 °C using a hydrothermal reactor equipped for a potentiometric monitoring, allowing in situ pH and Eh measurements. The thermal decomposition of hydrazine in simulated feed waters steam generators of PWR plants was monitored and appeared to be catalyzed by the surface of the titanium vessel or by magnetite particles, present as a model of the usual corrosion products. Rates are also dependent on pH or, keeping in mind that it is a catalyzed reaction, on the increasing proportion of N2H4 relative to N2H 5 + , the hydrazinium cation being less sorbed under acidic conditions. Ethanolamine appears to be stable for over a month while morpholine is decomposed in few days in contact with magnetite. The in situ pH measurements are consistent with theoretical predictions using acidity constants of morpholine and ethanolamine from the limited literature data. The redox potential imposed by hydrazine was measured and was between −0.45 V (pHT = 5) and −0.65 V (pHT = 7) provided that the concentration of hydrazine exceeds the threshold concentration of 20–50 μg·kg−1. Above this concentration, the potential was poorly dependent on the hydrazine concentration. The observed pH–Eh relationship reflects proton production during the oxidation of N2H4 to N2. From the Eh values, a standard potential of −1.1 V at 275 °C has been calculated for this reaction.

Kinetic parameters for thermal decomposition of hydrazine

The propulsion of most of the operating satellites comprises monopropellant (hydrazine––N2H4) or bipropellant (monometilydrazine—MMH and nitrogen tetroxide) chemical systems. When some sample of the propellant tested fails, the entire sample lot shall be rejected, and this action has turned into a health problem due to the high toxicity of N2H4. Thus, it is interesting to know hydrazine thermal behavior in several storage conditions. The kinetic parameters for thermal decomposition of hydrazine in oxygen and nitrogen atmospheres were determined by Capela–Ribeiro nonlinear isoconversional method. From TG data at heating rates of 5, 10, and 20 °C min−1, kinetic parameters could be determined in nitrogen (E = 47.3 ± 3.1 kJ mol−1, lnA = 14.2 ± 0.9 and Tb = 69 °C) and oxygen (E = 64.9 ± 8.6 kJ mol−1, lnA = 20.7 ± 3.1 and Tb = 75 °C) atmospheres. It was not possible to identify a specific kinetic model for hydrazine thermal decomposition due to high heterogeneity in reaction; however, experimental f(α)g(α) master-plot curves were closed to F1/3 model.

Thermal properties of hydrazine in nitric acid solution

Since some combustible, oxidative and reductive chemicals are used in the extracting process in the nuclear reprocessing plant the process has potential hazards of a fire and explosion due to the undesired reaction. In this study to obtain a better understanding of the thermal properties of hydrazine in nitric acid solution which is used for preventing the oxidation of extracted plutonium, thermal analysis was carried out for the mixtures in various conditions. From the results of DSC it was revealed that the vessel material has an influence on the thermal decomposition of hydrazine. It was also found that hydrazine reacted with nitric acid in an autocatalytic manner, and concentration of nitric acid has a strong influence on the thermal hazard of hydrazine and nitric acid mixtures.

Calculating the amplitude and frequency of thermokinetic self-oscillations in the chamber of a liquid-fuel rocket motor with thermal decomposition of hydrazine

Calculating the amplitude and frequency of thermokinetic self-oscillations in the chamber of a liquid-fuel rocket motor with thermal decomposition of hydrazine

Hydrazine and Hydrogen Co-injection to Mitigate Stress Corrosion Cracking of Structural Materials in Boiling Water Reactors, (I) Temperature Dependence of Hydrazine Reactions

Hydrazine and hydrogen co-injection into reactor water is considered a new mitigation method of stress corrosion cracking in BWRs. Fundamental data such as the thermal decomposition of hydrazine, the reaction of hydrazine with oxygen and with hydrogen peroxide at temperatures ranging from 150 to 280°C are needed to evaluate suitability of this method. Reactions in bulk water were studied in a polytetrafluoroethylene pipe to separate surface reaction effects. The results were as follows. (1) The orders of the apparent reaction rate of hydrazine with oxygen were 1 and 0.5 for hydrazine and oxygen concentrations, respectively . Arrhenius parameters were k 0=69.0 s−1.μM−0.5 and (2) The orders of apparent reaction rate of hydrazine with hydrogen peroxide were each 0.5 for hydrazine and hydrogen peroxide concentrations kC 0.5 N2H4 C 0.5 H2O2 . Arrhenius parameters were k 0=1.42x 106 s−1, Ea =78.8 kJ.mol−1. Based on these data, the applicability of hydrazine and hydrogen co-injection into BWRs was considered. Hydrazine introduction to reactor water was confirmed to be accompanied by only 1% decomposition. The concentration of oxygen, which is injected to suppress the flow-assisted corrosion of carbon steel in current BWR operation, would decrease due to the reaction of hydrazine with oxygen. However oxygen concentration in feed water could be maintained at the required level if the concentration of oxygen injected in condensate water was at most doubled compared to the current operating concentration.

Hydrazine and Hydrogen Co-injection to Mitigate Stress Corrosion Cracking of Structural Materials in Boiling Water Reactors, (I) Temperature Dependence of Hydrazine Reactions

Hydrazine and hydrogen co-injection into reactor water is considered a new mitigation method of stress corrosion cracking in BWRs. Fundamental data such as the thermal decomposition of hydrazine, the reaction of hydrazine with oxygen and with hydrogen peroxide at temperatures ranging from 150 to 280°C are needed to evaluate suitability of this method. Reactions in bulk water were studied in a polytetrafluoroethylene pipe to separate surface reaction effects. The results were as follows. (1) The orders of the apparent reaction rate of hydrazine with oxygen were 1 and 0.5 for hydrazine and oxygen concentrations, respectively . Arrhenius parameters were k 0=69.0 s−1.μM−0.5 and (2) The orders of apparent reaction rate of hydrazine with hydrogen peroxide were each 0.5 for hydrazine and hydrogen peroxide concentrations kC 0.5 N2H4 C 0.5 H2O2 . Arrhenius parameters were k 0=1.42x 106 s−1, Ea =78.8 kJ.mol−1. Based on these data, the applicability of hydrazine and hydrogen co-injection into BWRs was considered. Hydrazine introduction to reactor water was confirmed to be accompanied by only 1% decomposition. The concentration of oxygen, which is injected to suppress the flow-assisted corrosion of carbon steel in current BWR operation, would decrease due to the reaction of hydrazine with oxygen. However oxygen concentration in feed water could be maintained at the required level if the concentration of oxygen injected in condensate water was at most doubled compared to the current operating concentration.

In situ studies of boron nitride crystallization from BN solutions in supercritical N–H fluid at high pressures and temperatures

The reaction of boron with products of the thermal decomposition of hydrazine and the crystallization of boron nitride from BN solutions in supercritical N–H fluid have been studies in situ at pressures up to 5.2 GPa and temperatures up to 1600 K using angle- and energy-dispersive X-ray diffraction with synchrotron radiation. Graphite-like boron nitride produced by the reaction between boron and N–H supercritical fluid dissolves in the latter to form associated solutions of different concentrations. On cooling, the disappearance of short-range order in this solution is observed, accompanied by the precipitation of solid phases (cBN or hBN and BN–NH3 intercalation compound depending on the pressure, temperature and concentration). Spontaneous crystallization of cubic boron nitride has been observed down to 1.9 ± 0.2 GPa, which is the lowest pressure of the cBN crystallization from a solution reported so far. The BN–NH3 hypothetical quasibinary section of the phase diagram of the B–N–H system at 4 GPa has been constructed.

Critical reactions for the hydrazine vapor detonations

A detailed kinetic model devoted to the hydrazine vapor detonation has been built. It consists of 33 reversible reactions and 13 species. A reduced kinetic model has been proposed by using the Principal Component Analysis of matrix F (PCAF) method as implemented in KINALC. It is constituted of 26 reactions and 11 species. This model has been shown to be valid over a pressure range of 0.1 to 10 atm. However, the predictions of the models are significantly affected by changes in the enthalpy of formation of N $_2$ H $_3$ . With the help of the full kinetic model, a value of A, the proportionality factor in the ZND model between the induction distance in the detonation wave and the detonation cell size, of $27.5 \pm 3.0$ has been derived if one considers that the collision efficiency of N $_2$ H $_4$ on the thermal decomposition of hydrazine is equal to the one of N $_2$ . The value of A for pure hydrazine detonation is shown to be strongly dependent on the value of the collision efficiency of N $_2$ H $_4$ .

The Thermal Decomposition of NH2 and NH Radicals

AbstractThe formation of NH2 and NH radicals as well as H and N atoms during the thermal decomposition of hydrazine was investigated over a wide temperature range. For the first time frequency‐modulated spectroscopy was used for the detection of NH2 radicals behind shock waves. In comparison with the dual beam laser absorption technique, the detection limit has been improved by one and a half orders of magnitude.For reaction (5a) NH2 + M → NH + H + M the rate constants were obtained in the temperature range from 2200 to 4000 Kk5a = (1.2 ± 0.5)1015 · exp[‐(318±10) kJ mol−1/RT] cm3/mol sand for reaction (6) NH + M → N + H + M in the temperature range from 2500 to 3400 Kk6 = (1.8 ± 0.8)1014 · exp[‐(313 ± 15)kJ mol−1/RT] cm3/mol s.The experimental apparent activation energies were found to be in good agreement with theoretical calculations and recently recommended enthalpies of formation for NH2 and NH. The competing NH2 decomposition channel (5b) NH2 + M → N + H2 + M was shown to be of minor importance (⩽ 5%). The kinetic behavior of the unimolecular decomposition of NH2 is compared with that of H20 and 3CH2.

A Study about the Reactions of NH2 (X̃2B1) Radicals with Unsaturated Hydrocarbons in the Gas Phase

AbstractThe reactions of NH2(X̃2B1) with the hydrocarbons ethene (1), propene (2) and acetylene (3) were investigated behind incident shock waves at temperatures between 1500 K and 2000 K. The decay of NH2 was measured by laser absorption. NH2 was formed by the thermal decomposition of hydrazine. The following rate constants were obtained for the temperature range mentioned: These measurements extend the results obtained at low temperatures by Bosco et al. (240 K–460 K) and by Khe and Lesclaux (300 K–500 K) into the range of interest for combustion processes.The apparent energies of activation correlate well with the ionisation potentials of the unsaturated hydrocarbons and can therefore be used for the extrapolation to the addition reactions of the higher alkenes. For the reaction of propene with NH2 a contribution of an abstraction reaction channel besides electrophilic addition cannot be excluded at high temperatures.

A Kinetic Study About the Reactions of NH2(X̄2B1) Radicals with Saturated Hydrocarbons in the Gas Phase

AbstractThe reactions of NH2(X̄2B1) with the hydrocarbons methane (1), ethane (2) and propane (3) were investigated behind incident shock waves at temperatures between 1500 K and 2100 K. The decay of NH2 was measured by laser absorption. NH2 was formed by the thermal decomposition of hydrazine. The following rate constants were obtained for the temperature range mentioned:k1 = (1.2±0.6)·1013 exp(‐(63.4±3.4) kJ/mol/RT) cm3 mol−1 s−1k2 = (9.7±0.3)·1012 exp(‐(48.0±1.8) kJ/mol/RT) cm3 mol−1 s−1k3 = (1.7±0.4)·1013 exp(‐(44.6±2.0) kJ/mol/RT) cm3 mol−1 s−1.These measurements extend the results obtained at low temperatures by Demissy and Lesclaux (330 K–250 K) and by Hack et al. (400 K–1080 K) into the range of interest for combustion processes.The apparent energies of activation fit rather well into an Evans Polanyi plot. They correlate with the energies of activation of the corresponding reactions of OH(X2II)and those of CH3(X2A2) radicals.

Surface chemistry of hydrazine on Pt(111)

Abstract The thermal decomposition of hydrazine, N2H4, adsorbed on a Pt(111) surface at 60 K has been investigated by temperature programmed desorption (TPD), high resolution electron energy loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and temperature programmed secondary ion mass spectroscopy (TPSIMS). Condensed multilayer and chemisorbed states of hydrazine can be distinguished. Submonolayer hydrazine coverages start to decompose between 150 and 200 K by dissociation of NH, not NN, bonds. In TPD, H2, NH3, and N2 all peak near 310 K. N2 and NH2 desorb in processes limited by the rates of the reactions forming them. N2 is formed by an intramolecular process. No nitrogen containing species are detected above 400 K in HREELS or XPS. Depending on the surface coverage and temperature, dihydrogen desorption is probably limited by both the recombination rate and the rate of NH cleavage. We propose that: (1) the low temperature NH bond cleavage and the retention of NN bonds are facilitated by the chemisorption of N2H4 through both nitrogen atoms, and (2) relative to the N-metal bond, the H-metal bond is stronger on Pt(111). As a result, the barrier to NH cleavage is lowered much more than the barrier to NN cleavage, and the former is preferred.

Surface chemistry of hydrazine on Pt(111)

The thermal decomposition of hydrazine, N 2H 4, adsorbed on a Pt(111) surface at 60 K has been investigated by temperature programmed desorption (TPD), high resolution electron energy loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and temperature programmed secondary ion mass spectroscopy (TPSIMS). Condensed multilayer and chemisorbed states of hydrazine can be distinguished. Submonolayer hydrazine coverages start to decompose between 150 and 200 K by dissociation of NH, not NN, bonds. In TPD, H 2, NH 3, and N 2 all peak near 310 K. N 2 and NH 2 desorb in processes limited by the rates of the reactions forming them. N 2 is formed by an intramolecular process. No nitrogen containing species are detected above 400 K in HREELS or XPS. Depending on the surface coverage and temperature, dihydrogen desorption is probably limited by both the recombination rate and the rate of NH cleavage. We propose that: (1) the low temperature NH bond cleavage and the retention of NN bonds are facilitated by the chemisorption of N 2H 4 through both nitrogen atoms, and (2) relative to the N-metal bond, the H-metal bond is stronger on Pt(111). As a result, the barrier to NH cleavage is lowered much more than the barrier to NN cleavage, and the former is preferred.

Corrosion product build-up on stainless steel and its influence on hydrazine decomposition.60Co deposition in loop tests using borated water at 300�C

The corrosion rate of stainless steel decreases with time of operation under conditions characteristic of the primary circuit of pressurized-water reactors. Due to this the concentration of corrosion products in solution rapidly increases during heating-up and decreases after reaching the operation product levels is up to about three orders of magnitude. By a preoxidation treatment using potassium dichromate, the corrosion product release can be essentially diminished. In order to describe the influence of corrosion products in solution we investigate the thermal decomposition of hydrazine as well as the deposition behavior of60Co. the half life of the thermal N2H4 decomposition at 300°C in borated water increases from about 1 to about 60 minutes, starting with glossy loop surfaces. Without adding boric acid to the water, half lives between 1 and 120 minutes were found; with an activation energy for the decomposition being estimated in the temperature region 270–310°C. The deposition behavior of60Co is characterized by a very fast primary step, followed by retarded secondary deposition steps. The primary deposition step can be described by half lives of about 5 seconds. The influence of preoxidation treatment and subsequent decrease of corrosion product concentration on decomposition of N2H4 and deposition of60Co is discussed.

Messung der Geschwindigkeitskonstanten der Reaktion NH2+CH4→NH3+CH3 hinter einfallenden Stoßwellen / Measurements of the Rate Constant of the Reaction NH2+CH4→NH3+CH3 behind Incident Shock Waves

The rate constant of the reaction NH2+CH4→NH3+CH3 was measured at temperatures of about 1800 K by time-resolved UV-spectroscopy of the products behind incident shock waves. NH2 was produced by the presence and thermal decomposition of hydrazine. The data were evaluated by fitting simulated concentration-time-profiles to the measured ones. A mean rate constant k = (4±2) 1011 cm3 mol-1 s-1 1730 <T/K < 1950 was obtained. The temperature dependence of the reaction is discussed.

Investigation on an electrothermal hydrazine thruster

Thermal decomposition of hydrazine can be achieved when the fluid propellant is sprayed on an electrically heated surface. After the exothermal hydrazine decomposition reaction has been triggered, the electrical heating may be reduced or stopped completely. Investigations are made using an experimental thruster at a thrust level of 100 mN to 500 mN to achieve advantageous power consumption and thruster behavior by means of an optimal adjustment of heater configuration and propellant distribution within the reactor. Uniform distribution of very small quantities of propellant over the heater surface is essential for good performance. Tests have been most successful when the propellant is sprayed on fine-meshed screen. Further tests have been made using metal foam for distributing the propellant over a large surface. The foam pack has been heated up by internal heater coils to initiate decomposition. Metal foam offers some advantages when especially low propellant mass flowrates are used, but suitable foam materials are not available at this time.

Mass spectral studies of kinetics behind shock waves. II. Thermal decomposition of hydrazine : R. W. Diesen, J. Chem. Phys., 39 (9), 1 Nov. 1963, 2121–2128

Mass spectral studies of kinetics behind shock waves. II. Thermal decomposition of hydrazine : R. W. Diesen, J. Chem. Phys., 39 (9), 1 Nov. 1963, 2121–2128

Shock wave studies in nitrogen + hydrogen systems. Part 2.—Thermal decomposition of hydrazine

Shock wave studies in nitrogen + hydrogen systems. Part 2.—Thermal decomposition of hydrazine