- Degradation of gaseous unsymmetrical dimethylhydrazine by vacuum ultraviolet coupled with MnO2
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In this study, α-, β-, and δ-MnO2 were prepared by a uniform hydrothermal method and then coupled with vacuum ultraviolet (VUV) for the degradation of gaseous unsymmetrical dimethylhydrazine (UDMH). The performance in the removal of UDMH, by-product distribution and mechanism were systematically investigated. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption/desorption, Field Emission Scanning Electron Microscopy (FE-SEM), Raman, thermogravimetry (TG), Fourier-transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) to investigate the factors affecting the catalytic activity. The results showed that O2 and H2O were essential for the removal of UDMH. Photooxidation and ozone catalytic oxidation contribute to the removal and mineralization of UDMH. The integrated process considerably improved the removal and mineralization of UDMH by ozone catalytic oxidation. More reactive oxygen species were generated in the integrated process. The catalytic activity of the prepared catalysts follows the order: δ-MnO2 > α-MnO2 > β-MnO2. δ-MnO2 displayed the highest removal rate of 100% and a CO2 concentration of 42 ppmv. The good performance of δ-MnO2 was mainly attributed to the large number of surface oxygen vacancies.
- Huang, Yuanzheng,Jia, Ying,Shen, Keke,Hou, Ruomeng,Zhang, Yongyong,Hou, Li'an
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supporting information
p. 1194 - 1202
(2021/02/06)
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- TiO2-reduced graphene oxide for the removal of gas-phase unsymmetrical dimethylhydrazine
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Unsymmetrical dimethylhydrazine (UDMH) contaminated waste gas and related intermediates pose a great threat to human health. TiO2-reduced graphene oxide aerogel (rGA) samples with different graphene content levels were synthetized and characterized for the degradation of UDMH. The effects of GO content, humidity, and temperature were investigated under UV and VUV light, with highest UDMH conversion values of 68% and 95%, respectively. Compared with pure TiO2, the enhanced degradation activity of TiO2-rGA under UV light can be attributed to a synergetic effect between absorption and photocatalysis, while the high UDMH conversion under VUV light relies on photolysis and ozonation. The high oxygen-containing group content, rather than a high SSA, and electron trapping by graphene are key factors determining the outstanding performance of TiO2-rGA with 80 mg of GO. The prepared TiO2-graphene aerogels are promising for the degradation of gas-phase UDMH. This journal is
- Ruomeng, Hou,Ying, Jia,Yuanzheng, Huang,Keke, Shen,Huixin, Zhu
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p. 394 - 402
(2021/01/11)
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- Thermal behavior of ammonium dinitramide and amine nitrate mixtures
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This paper focuses on the thermal behavior of mixtures of ammonium dinitramide (ADN) and amine nitrates. Because some mixtures of ADN and amine nitrate exhibit low melting points and high-energy content, they represent potential liquid propellants for spacecraft. This study focused on the melting behavior and thermal-decomposition mechanisms in the condensed phase of ADN/amine nitrate mixtures during heating. We measured the melting point and exothermal behavior during constant-rate heating using differential scanning calorimetry and performed thermogravimetry–differential thermal analysis–mass spectrometry (TG–DTA–MS) to analyze the thermal behavior and evolved gases of ADN/amine nitrate mixtures during simultaneous heating to investigate their reaction mechanisms. Results showed that the melting point of ADN was significantly lowered upon the addition of amine nitrate with relatively low molecular volume and low melting point. TG–DTA–MS results showed that the onset temperature of the thermal decomposition of ADN/amine nitrates was similar to that of pure ADN. Furthermore, during thermal decomposition in the condensed phase, ADN produced highly acidic products that promoted exothermic reactions, and we observed the nitration and nitrosation of amines from the dissociation of amine nitrates.
- Matsunaga, Hiroki,Katoh, Katsumi,Habu, Hiroto,Noda, Masaru,Miyake, Atsumi
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p. 2677 - 2685
(2018/11/23)
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- Formation of N-nitrosamines and N-nitramines by the reaction of secondary amines peroxynitrite and other reactive nitrogen species: Comparison with nitrotyrosine formation
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Reactive nitrogen species, including nitrogen oxides (N2O3 and N2O4), peroxynitrite (ONOO-), and nitryl chloride (NO2Cl), have been implicated as causes of inflammation and cancer. We studied reactions of secondary amines with peroxynitrite and found that both N-nitrosamines and N- nitramines were formed. Morpholine was more easily nitrosated by peroxynitrite at alkaline pH than at neutral pH, whereas its nitration by peroxynitrite was optimal at pH 8.5. The yield of nitrosomorpholine in this reaction was 3 times higher than that of nitromorpholine at alkaline pH, whereas 2 times more nitromorpholine than nitrosomorpholine was formed at pH 2N·), which react with nitric oxide (·NO) or nitrogen dioxide (·NO2) to yield nitroso and nitro secondary amines, respectively. Reaction of morpholine with NO· and superoxide anion (O2·-), which were concomitantly produced from spermine NONOate and by the xanthine oxidase systems, respectively, also yielded nitromorpholine, but its yield was 2·- inhibited its formation. Reactions of morpholine with nitrite plus HOCl or nitrite plus H2O2, with or without addition of myeloperoxidase or horseradish peroxidase, also yielded nitration and nitrosation products, in yields that depended on the reactants. Tyrosine was nitrated easily by synthetic peroxynitrite, by NaNO2 plus H2O2 with myeloperoxidase, and by NaNO2 plus H2O2 under acidic conditions. Nitrated secondary amines, e.g., N-nitroproline, could be identified as specific markers for endogenous nitration mediated by reactive nitrogen species.
- Masuda, Mitsuharu,Mower, Howard F.,Pignatelli, Brigitte,Celan, Irena,Friesen, Marlin D.,Nishino, Hoyoku,Ohshima, Hiroshi
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p. 301 - 308
(2007/10/03)
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- Gas-Phase Reactions of (CH3)2N Radicals with NO and NO2
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The absolute rate constants for the reactions of (CH3)2N radicals with NO and NO2 were determined in the gas phase and at room temperature by using the very low pressure reactor (VLPR) technique.The rates were k(CH3)2N + NO = (8.53 +/- 1.42) x 1E-14 Cm3 molecule-1s-1 and k(CH3)2N + NO2 = (9.08 +/- 1.36) x 1E-13 cm3 molecule-1s-1.The reaction with NO2 proceeds via two competitive pathways: the recombination patway (CH3)2N + NO2 -> (CH3)2NNO2, with a rate constant k2a = (3.18 +/- 0.48) x 1E-13 cm3molecule-1s-1, and the oxidation patway (CH3)2N + NO2 -> (CH3)2NONO* -> (CH3)2NO + NO, with a rate constant k2b = (6.36 +/- 0.74) x 1E-13 cm3molecule-1s-1.The oxidation pathway is ca. 2.2 times faster than the recombination one, and the ratio k2a/k2b = 0.45 +/- 0.15.Conventional transition state theory analysis indicates that the involved transition states are loose, with the NN or bond lengths equal to ca. 2.5 Angstroem.
- Lazarou, Yannis G.,Kambanis, Kyriakos G.,Papagiannakopoulos, Panos
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p. 2110 - 2115
(2007/10/02)
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- Oxidation of N-Nitrosodibenzylamine and Related Compounds by Metalloporphyrin-catalysed Model Systems for the Cytochrome P450 Dependent Mono-oxygenases
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N-Nitrosodibenzylamine has been oxidised to benzaldehyde and benzyl alcohol by iodosylbenzene, 3-chloroperoxybenzoic acid and t-butyl hydroperoxide catalysed by tetraphenylporphyrinato-iron(III) chloride or -manganese(III) chloride.The influence of reaction conditions on the product yields and distribution have been studied.Kinetic isotope effects have been measured with deuteriated N-nitrosodibenzylamines for inter- and intra-molecular competition for the oxidants.The evidence presented is in favour of the iodosylbenzene and t-butyl hydroperoxide oxidations being initiated by hydrogen-atom abstraction by the oxidant from the α-hydrogen of the benzyl group.However, oxidations by the peroxy acid systems may proceed by an initial electron transfer.The reactions of N-nitrosodimethylamine and N-nitrosopiperidine with the metalloporphyrin-catalysed systems show that these substrates are surprisingly unreactive towards oxidation.
- Smith, John R. Lindsay,Nee, Michael W.,Noar, J. Barry,Bruice, Thomas C.
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p. 255 - 260
(2007/10/02)
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- Analysis of the Ignition Products of Unsymmetrical Dimethyl Hydrazine with Nitric Acid and the Probable Reaction Mechanism
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The reaction products of unsymmetrical dimethyl hydrazine (UDMH) with nitric acid, under ignition and near ignition conditions have been examined through methods of intrumental analysis.Spectroscopic methods which include uv, ir, nmr and mass spectra have been used for the liquid products and gas chromatography for the gaseous and the liquid products.A mechanism for the reaction is proposed on the basis of the known chemistry of UDMH and HNO3 as well as reactions and intermediates that are known and on analogous reactions of similar reagents.
- Singh, S. P.,Prasad, R. K.
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p. 170 - 175
(2007/10/02)
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