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1.
D. S. Hwang K. I. Lee Y. D. Choi S. T. Hwang J. H. Park 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(2):327-333
The Korea Atomic Energy Research Institute (KAERI) has launched a decommissioning program of the uranium conversion plant.
The sludge waste, which was generated during the operation of the plant and stored in the lagoon, was characterized for the
development of the treatment process. The physical properties were measured and chemical compositions and radiological properties
analyzed. The main compounds of the sludge were ammonium nitrate, sodium nitrate, calcium nitrate, and calcium carbonate.
All heavy radioactive elements such as uranium, thorium and 226Ra were precipitated and deposited at the bottom, and were not dissolved in the concentrated nitrate solution. A possible
flow-scheme for processing is presented.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
O.A. Vita 《Analytica chimica acta》1976,81(1):45-52
Uranium hexafluoride reacts with nitrosyl fluoride (NOF), nitryl fluoride (NO2F), and nitrogen oxides to form solid compounds such as nitrosyl heptafluorouranate (NOUF7) and nitryl heptafluorouranate (NO2UF7). Since these compounds are undesirable impurities in uranium hexafluoride, a method has been developed for the determination of these nitrogen oxyfluorides in uranium hexafluoride. Uranium hexafluoride is hydrolyzed in a potassium permanganate solution which converts the uranium hexafluoride to uranyl fluoride and the nitrogen oxyfluorides to nitric acid. The nitrate is reduced with aluminum powder to ammonia, which is then measured with an ammonia electrode in a basic solution. The method is relatively interference-free because the electrode is a gas-sensing device. The detection limit is 0.8 μg bound N/g U, and the precision at 3 μg bound N/g U is ± 16%. 相似文献
3.
Hydrazo-carbonates are complex compounds and products of the reactions between solutions of metal ion and solutions of hydrazido-carbonic acid. The decomposition of Mg(N2H3COO)2. 2H2O, Ca(N2H3COO)2·H2O and Zn(N2H3COO)2 in inert atmosphere were studied. By classical thermoanalytical methods and data on the composition of the intermediates and final products the mechanisms of the thermal decomposition could not be resolved therefore also evolved gas analysis was used (EGA). The first step of thermal decomposition of Ca and Mg hydrazidocarbonates is dehydration. With the heating the decomposition of the hydrazido-carbonates proceeds under evolution of the ammonia, carbon monoxide and/or nitrogen and carbon dioxide giving as the intermediates for calcium and magnesium compounds the corresponding carbonates oxides as the final products. The zinc compound decomposes to the oxide, ZnO but also zinc cyanamide was detected during to the thermal treatment. 相似文献
4.
Thermal decomposition of [Cd(NH3)6](NO3)2 was studied by thermogravimetry (TG) with simultaneous differential thermal analysis (SDTA) for two samples and at two different
sets of measurement parameters. The gaseous products of the decomposition were on-line identified by evolved gas analysis
(EGA) with a quadruple mass spectrometer (QMS). The decomposition of the title compound proceeds, for both cases, in the three
main stages. In the first stage, deammination of [Cd(NH3)6](NO3)2 to [Cd(NH3)](NO3)2 undergoes by three steps and 5/6 of all NH3 molecules are liberated. At second stage the liberation of residual 1/6NH3 molecules and the formation of Cd(NO3)2 undergoes. However, during this process simultaneously a two-step oxidation of a part of ammonia molecules also takes place.
In a first step as a result a mixture of ammonia, water vapour and nitrogen is formatted. At the second step, subsequent oxidation
of a next part of NH3 molecules undergoes. As a result, a mixture of nitrogen oxide, nitrogen and water vapour is formatted, what for these both
steps clearly indicates the EGA analysis. The third stage of the thermal decomposition is connected with the melting and subsequent
decomposition of residual Cd(NO3)2 to oxygen, nitrogen dioxide and solid CdO. Additionally, third sample was measured by differential scanning calorimetry (DSC)
and the results are fully consistent with those obtained by TG. 相似文献
5.
D. E. Doronkin L. V. Piryutko E. V. Starokon’ G. I. Panov A. Yu. Stakheev 《Kinetics and Catalysis》2012,53(6):747-752
The catalytic properties of Fe-ZSM-5 zeolites with different iron contents have been investigated in the selective catalytic reduction (SCR) of NO x with ammonia. The observed catalytic properties the zeolites are correlated with the concentration of the iron-containing sites that are stabilized in the zeolite and effect N2O decomposition (??-sites). The catalysts activated at a high temperature to increase the ??-site concentration (by a factor of 5?C10) are more active in NO x SCR with ammonia than the unactivated samples. However, the difference between the activities of the activated and unactivated catalysts is well below the difference between the ??-site concentrations in these catalysts. The nonlinear relationship between these parameters is evidence that the ??-sites in Fe-ZSM-5 is not the only factor determining the activity of Fe-ZSM-5 in NO x SCR with ammonia. The activated catalysts show a low activity in nonselective ammonia oxidation and, accordingly, a high selectivity in the target process at high temperatures. 相似文献
6.
Stabilization of ammonium dinitramide in the liquid phase 总被引:1,自引:0,他引:1
Andreev A. B. Anikin O. V. Ivanov A. P. Krylov V. K. Pak Z. P. 《Russian Chemical Bulletin》2000,49(12):1974-1976
The kinetics of accumulation of the main products of thermal decomposition of ammonium dinitramide in the melt was investigated. The isotope composition of nitrogen-containing gases evolved by the decomposition of 15NH4N(NO2)2 and NH4
15N(NO2)2 was found. Easily oxidized salts, amines, amides, iodides, and other compounds soluble in the melt interfere with the liquid-phase decomposition of ammonium dinitramide. 相似文献
7.
Widening Synthesis Bottlenecks: Realization of Ultrafast and Continuous‐Flow Synthesis of High‐Silica Zeolite SSZ‐13 for NOx Removal
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Zhendong Liu Prof. Dr. Toru Wakihara Dr. Kazunori Oshima Daisuke Nishioka Yuusuke Hotta Dr. Shanmugam P. Elangovan Yutaka Yanaba Prof. Dr. Takeshi Yoshikawa Dr. Watcharop Chaikittisilp Takeshi Matsuo Takahiko Takewaki Prof. Dr. Tatsuya Okubo 《Angewandte Chemie (International ed. in English)》2015,54(19):5683-5687
Characteristics of zeolite formation, such as being kinetically slow and thermodynamically metastable, are the main bottlenecks that obstruct a fast zeolite synthesis. We present an ultrafast route, the first of its kind, to synthesize high‐silica zeolite SSZ‐13 in 10 min, instead of the several days usually required. Fast heating in a tubular reactor helps avoid thermal lag, and the synergistic effect of addition of a SSZ‐13 seed, choice of the proper aluminum source, and employment of high temperature prompted the crystallization. Thanks to the ultra‐short period of synthesis, we established a continuous‐flow preparation of SSZ‐13. The fast‐synthesized SSZ‐13, after copper‐ion exchange, exhibits outstanding performance in the ammonia selective catalytic reduction (NH3‐SCR) of nitrogen oxides (NOx), showing it to be a superior catalyst for NOx removal. Our results indicate that the formation of high‐silica zeolites can be extremely fast if bottlenecks are effectively widened. 相似文献
8.
The kinetics of thermal decomposition of melted hydroxylammonium nitrate have been investigated by the rate of heat production in the temperature range 84.8–120.9°C. The decomposition proceeds with autocatalysis and up to 60 % of conversion the rate of the process increases proportionally to the square of the degree of decomposition. The initial rate is proportional to the square of the concentration of HNO3 formed due to dissociation of the salt. The activation energy of this process is 15.3±1.8 kcal/mol. It is suggested that the initial stage the process proceeds via interaction between N2O3 and NH3OH+, whereas the subsequent acceleration is due to oxidation of NH3OH+ by nitrogen oxides formed as well as by nitrous acid.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1897–1901, November, 1993. 相似文献
9.
The effect of NO3? contaminant on the thermal decomposition of chromia gel has been thoroughly investigated. NO3?free gel, prepared by treating a dilute solution of chromium nitrate with aqueous ammonia, and a simulated NO3?-contaminated one, obtained by mechanically mixing calculated amounts of the pure gel and NH4NO3 (4.7–33.3% by weight), have been subjected to thermogravimetric and differential thermal analyses. The thermal behaviour thus monitored has been physicochemically characterized by means of infrared and X-ray diffraction techniques. The results obtained have revealed a notable disparity between the reaction pathways conceded by the pure and the contaminated gel yielding chromias of different properties. 相似文献
10.
Hiroki Matsunaga Hiroto Habu Atsumi Miyake 《Journal of Thermal Analysis and Calorimetry》2013,113(3):1387-1394
Ammonium dinitramide (ADN) is one of the several promising new solid propellant oxidizers. ADN is of interest because its oxygen balance and energy content are high, and it also halogen-free. One of the most important characteristics of a propellant oxidizer, however, is stability and ADN is known to degrade to ammonium nitrate (AN) during storage, which will affect its performance. This study focused on the effects of aging on the thermal decomposition mechanism of ADN. The thermal behaviors of ADN and ADN/AN mixtures were studied, as were the gases evolved during their decomposition, using differential scanning calorimetry (DSC), thermogravimetry–differential thermal analysis-infrared spectrometry (TG–DTA-IR), and thermogravimetry–differential thermal analysis-mass spectrometry (TG–DTA-MS). The results of these analyses demonstrated that the decomposition of ADN occurs via a series of distinct stages in the condensed phase. The gases evolved from ADN decomposition were N2O, NO2, N2, and H2O. In contrast, ADN mixed with AN (to simulate aging) did not exhibit the same initial reaction. We conclude that aging inhibits early stage, low temperature decomposition reactions of ADN. Two possible reasons were proposed, these being either a decrease in the acidity of the material due to the presence of AN, or inhibition of the acidic dissociation of dinitramic acid by NO 3 ? . 相似文献
11.
A. V. Ivanov S. V. Filimonov O. N. Shornikova A. P. Malakho 《Russian Chemical Bulletin》2016,65(1):282-286
The composition of gas evolved upon thermal decomposition of individual and carbamidemodified graphite nitrates was determined. The addition of carbamide was shown to result in the 2—4-fold decrease in the content of nitrogen oxides and the 2—5-fold increase in the content of carbon monoxide. The content of nitrogen oxides in the gas phase decreased when the HNO3 : (NH2)2CO molar ratio was equal to 1 : (0.4—1). Combination of carbamide addition with catalytic afterburning provides the 5-fold decrease in the gas-phase amount of nitrogen oxides at the minimum CO content. 相似文献
12.
Investigation of the Effect of Various Substituents on the Density of Tetrazolium Nitrate Salts as Green Energetic Materials
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The substitution effect of various functional groups such as –NO2, –CN, –N3, –NF2, and –NH2 on the density of tetrazolium nitrate salts is investigated through multiple linear regression method. The methodology of this work introduces a new model, which related density of tetrazolium nitrate salts to the number of fluorine and nitrogen atoms, the presence of NF2 groups, NO2 groups, as well as CH3 groups in the structural formula. The new reliable correlation shows that the NF2 and NO2 group can cause increasing the density of tetrazolium nitrate salts, especially NO2, whereas the CH3 group can decrease their density. The new proposed relationship has good reliability and predictability, so it can be used to design new rich nitrogen compounds based on tetrazolium nitrate salts as green energetic materials. These results are also tested for N,N′‐azo‐1,2,4‐triazolium nitrate salts, which is caused to derive another correlation. This correlation shows that the presence of NF2 functional groups increases the density of N,N′‐azo‐1,2,4‐triazolium nitrate salts as well as the value of nO/nC. 相似文献
13.
Solubility data in the diagonal sections of the quaternary reciprocal 2KCl + Ca(NO3)2 → 2KNO3 + CaCl2–H2O system at 25 and 15°C are presented. It has been shown that the quaternary system has no stable diagonal at the studied temperatures, but contains a stable pair of salts, namely, potassium nitrate and calcium chloride. The obtained data can be used to optimize the thermal and concentrational parameters of the synthesis of potassium nitrate from calcium nitrate and potassium chloride. 相似文献
14.
《Journal of photochemistry and photobiology. A, Chemistry》2007,185(2-3):371-382
Photochemical reactions of trace compounds in snow have important implications for the composition of the atmospheric boundary layer in snow-covered regions and for the interpretation of concentration profiles in snow and ice regarding the composition of the past atmosphere. One of the prominent reactions is the photolysis of nitrate, which leads to the formation of OH radicals in the snow and to the release of reactive nitrogen compounds, like nitrogen oxides (NO and NO2) and nitrous acid (HONO) to the atmosphere. We performed photolysis experiments using artificial snow, containing variable initial concentrations of nitrate and nitrite, to investigate the reaction mechanism responsible for the formation of the reactive nitrogen compounds. Increasing the initial nitrite concentrations resulted in the formation of significant amounts of nitrate in the snow. A possible precursor of nitrate is NO2, which can be transformed into nitrate either by the attack of a hydroxy radical or the hydrolysis of the dimer (N2O4). A mechanism for the transformation of the nitrogen-containing compounds in snow was developed, assuming that all reactions took place in a quasi-liquid layer (QLL) at the surface of the ice crystals. The unknown photolysis rates of nitrate and nitrite and the rates of NO and NO2 transfer from the snow to the gas phase, respectively, were adjusted to give an optimum fit of the calculated time series of nitrate, nitrite, and gas phase NOx with respect to the experimental data. Best agreement was obtained with a ∼25 times faster photolysis rate of nitrite compared to nitrate. The formation of NO2 is probably the dominant channel for the nitrate photolysis. We used the reaction mechanism further to investigate the release of NOx and HONO under natural conditions. We found that NOx emissions are by far dominated by the release of NO2. The release of HONO to the gas phase depends on the pH of the snow and the HONO transfer rate to the gas phase. However, due to the small amounts of nitrite produced under natural conditions, the formation of HONO in the QLL is probably negligible. We suggest that observed emissions of HONO from the surface snow are dominated by the heterogeneous formation of HONO in the firn air. The reaction of NO2 on the surfaces of the ice crystals is the most likely HONO source to the gas phase. 相似文献
15.
Lee Y. H. Chung J. W. Choi Y. R. Chung J. S. Cho M. H. Namkung W. 《Plasma Chemistry and Plasma Processing》2004,24(2):137-154
NOx removal characteristics and NO conversion trends were investigated for plasma process, catalytic process, and plasma catalytic hybrid process. In the experiments, we studied effects of the flow rate and the carrier gas on the NO conversion in the plasma process, and effects of ammonia concentration and temperature on the NOx removal in the catalytic process. We also investigated the synergetic effect of a plasma-catalytic hybrid process. Dielectric barrier discharge was combined with V2O5–WO3/TiO2 catalyst for removing nitrogen oxides. The maximum conversions of nitrogen oxides were approximately 52, 80, and 98% at the temperature of 100, 200, and 300°C, respectively. The optimal energy density, ammonia concentration, and ratio of nitrogen oxides exist for the highest removal of nitrogen oxides in the plasma catalytic hybrid process. 相似文献
16.
In this paper, a TG/DTG–DSC–FTIR study of type I collagen extracted from bovine Achilles tendon both in inert (nitrogen) and oxidative atmosphere (synthetic air and oxygen) from room temperature to 700 °C was performed. The thermal analysis results have shown that after initial dehydration, collagen exhibits a single decomposition step in nitrogen (due to pyrolysis), while in air and oxygen two steps are observed due to thermo-oxidative decomposition, the latter being highly exothermic. The CO2 bands dominate the FTIR spectra of evolved gases in all atmospheres (especially in air and oxygen), along with the characteristic bands of ammonia, water, HNCO, methane. In nitrogen, the bands of pyrrole, HCN, and ethane were also identified, while in oxidative atmospheres, nitrogen oxides and CO are released. A study was also performed by comparing the DTG and gas evolution curves observed for the three atmospheres. 相似文献
17.
The thermal decomposition behaviour of the complexes of rare earth metals with histidine: RE(His)(NO3)3H2O (RE=La—Nd, Sm—Lu and Y; His=histidine) was investigated by means of TG-DTG techniques. The results indicated that the thermal decomposition processes of the complexes can be divided into three steps. The first step is the loss of crystal water molecules or part of the histidine molecules from the complexes. The second step is the formation of alkaline salts or mixtures of nitrates with alkaline salts after the histidine has been completely lost from the complexes. The third step is the formation of oxides or mixtures of oxides with alkaline salts. The results relating to the three steps indicate that the stabilities of the complexes increase from La to Lu.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
18.
V. I. Zheivot T. A. Nikoro V. N. Krivoruchko L. I. Panina L. G. Pinaeva L. A. Isupova 《Journal of Analytical Chemistry》2007,62(12):1170-1175
Peculiarities of the determination of nitrogen oxides and ammonia in the reaction products of ammonia oxidation are studied by gas chromatography. Particular attention was paid to the sampling problem. It is shown that in the course of the transportation of samples containing nitrogen(II) oxide and oxygen, the oxidation of nitrogen(II) oxide to nitrogen(IV) oxide takes place in the vapor phase. The conditions were found for suppressing or even eliminating the gas-phase reaction of NO oxidation to NO2. A procedure for the gas-chromatographic analysis of the reaction products in the catalytic oxidation of ammonia is proposed using several samples and packed columns, including the determination of NO with respect to NO2 formed in the gas-phase oxidation of NO. 相似文献
19.
Nitrogen oxides are nowadays a subject of global concern. Several types of nitrogen oxides exist in the environment: N2O, NO, NO2, N2O3, N2O4, N2O5. The abbreviation NO
x
usually relates to nitric oxide NO, nitrogen dioxide NO2, and nitrous oxide N2O. The first two are harmful pollutants for both environment and human health, whereas the third is one of the greenhouse
gases. Implementation of stringent NO
x
emission regulations requires the development of new NO
x
removal technologies from exhaust gases. One of many proposals for NO
x
emission reduction is the application of an oxidizing agent which would transform NO
x
to higher nitrogen oxides with higher solubility in water. The main objective of the paper was to present the rate constant
of nitric oxide oxidation, determined in our studies. 相似文献
20.
Polymorphism and thermal decomposition of [Mg(DMSO)6](NO3)2, where DMSO =(CH3)2SO, were studied by differential scanning calorimetry (DSC) and thermogravimetry (TG). The gaseous products of the decomposition
were on-line identified by a quadruple mass spectrometer (QMS). Three phase transitions have been detected for this compound
in the temperature range of 95–370 K between the following solid phases: stable KIb↔stable KIa at T
C3=195 K, metastable KII↔supercooled K0 at T
C2=230 K and stable KIa→stable K0 at T
C1=337 K.
Thermal decomposition of the title compound proceeds in three main stages. In the first stage, which starts just above ca.
380 K, and is continued up to ca. 540 K, the compound loses in two steps four DMSO molecules per one formula unit and undergoes
into [Mg(DMSO)2](NO3)2. The second stage starts just immediately after liberating four DMSO ligands and is connected with the decomposition of [Mg(DMSO)2](NO3)2 and the formation of a mixture of solid anhydrous magnesium sulfate, magnesium nitrate and magnesium oxide and also a mixture
of gaseous products of the DMSO and Mg(NO3)2 decomposition. The third and the last stage corresponds to the decomposition of not decomposed yet magnesium nitrate and
formation of magnesium oxide, nitrogen oxides and oxygen. 相似文献