Influence of NO on the Reduction of NO2 with CO over Pt/SiO2 in the Presence of O2

Reduction of NO2 with CO in the presence of NO and excess oxygen, a model mixture for flue gas, over a 0.1% Pt/SiO2 catalyst was studied. The related reaction mechanisms, such as oxidation of CO and NO, were discussed. It was found that there was a narrow temperature window （180-190 ℃） for the reduction of NO2 by CO. When the temperature was lower than the lower limit of the window, the reduction hardly occurred, while when the temperature was higher than the upper limit of the window, the direct oxidation of CO by O2 occurred and thereby NO2 could not be effectively reduced by CO. The presence of NO shifted the window to higher temperatures owing to the inhibition effect of NO on the activation of O2 on Pt, which made it possible to reduce NO2 by CO in flue gas.     

Temperature dependence of the reaction NO + NO3 → 2NO2

The flash photolysis-visible absorption technique has been used to measure rate constants for the reaction NO + NO₃ → 2NO₂ (1) over the temperature range 224–328 K. The temperature dependence of the rate constant is given by the expression k₁(T) = (1.59 ± 0.32) × 10⁻¹¹exp(122/T) cm³ molecule⁻¹ s⁻¹ where the stated uncertainties refer to the ± 2σ limits from both random and systematic errors.     

Radiation-Thermal Decomposition of NO2–NO Mixtures in a 60Co γ-Radiation Field

The effect of nitrogen monoxide (up to 60 wt %) on the radiation-thermal decomposition of a dissociating mixture based on N₂O₄ in a ⁶⁰Co -radiation field was studied over the temperature range 200–300° at a pressure of 2 MPa. A comparison of the experimental results with data calculated using an additive mathematical model of radiolysis and data obtained in previous studies on processes in an n,-radiation field led to the conclusion that the role of intermolecular energy-transfer processes is insignificant. The currently available mathematical model adequately describes the radiolysis of nitrogen oxides over wide temperature and pressure ranges.     

Separation of15N by chemical exchange in NO, NO2−HNO3 system under pressure

The basic isotopic exchange reaction is responsible for the separation of¹⁵N in the Nitrox system that between gaseous nitrogen oxides and aqueous nitric acid with a single stage separation factor α=1.055 for 10M nitric acid, at 25°C and atmospheric pressure takes place. In order to know what happens in¹⁵N separation at higher pressure, when the isotopic transport between two phases is improved, a stainless steel laboratory experimental plant with a 1000 mm long × 18 mm i.d. column, packed with triangular wire springs 1.8×1.8×0.2 mm², was utilised. At 1.5 atm (absolute), and 2.36 ml·cm⁻²·min⁻¹ flow rate HETP was 7% smaller than at atmospheric pressure and 1.5 times smaller flow rate. HETP at 3.14 ml·cm⁻²·min⁻¹ flow rate and 1.8 atm is practically equal with that obtained at atmospheric pressure and 2 times smaller flow rate. The operation of the¹⁵N separation plant at 1.8 atm (absolute), instead of atmospheric pressure, will permit doubling of the 10M nitric acid flow rate and of¹⁵N production of the given column.     

Plasma-catalytic Selective Reduction of NO with C2H4 in the Presence of Excess Oxygen

This paper reports observations of significant synergistic effects between dielectric barrier discharge (DBD) plasmas and Cu-ZSM-5 catalysts for C2H4 selective reduction of NOx at 250℃ in the presence of excess oxygen by using a one-stage plasma-over-catalyst (POC) reactor. With the reactant gas mixture of 530 ppm NO, 650ppm C2H4, 5.8% 02 in N2and GHSV = 12000h^-1, the pure catalytic, pure plasma-induced (discharges over fused silica pellets) and plasma-catalytic (in the POC reactor) NOx conversion are 39%, 1.5% and 79%, respectively. The in-situ optical emission spectra of the reactive systems imply some short-lived active species formed from plasma-induced and plasma-catalytic processes may be responsible to the observed synergistic effects in this one-stage POC system.     

Interference peaks in translational energy loss spectra. An example in the spectrum of NO2+·

Translation energy loss (TEL) spectra for NO^2+· in collision with helium were obtained using the methods of O'Keefe et al. [2]. The results are in generally satisfactory agreement with the previous work, and are compared with other information on states of NO^2+·, particularly data from double-charge-transfer spectroscopy which are in serious disagreement with the present and previous TEL results. In the course of the present work and in other translational energy studies in this laboratory, a problem, inherent in TEL spectroscopy conducted on a double-focusing mass spectrometer, that can lead to spurious peaks, became apparent and is discussed.     

Influence of Sulfation on the Catalytic Activity of Ni-ZrO2 for NO Reduction with Propane in Excess Oxygen

Selective catalytic reduction （SCR） of nitric oxide with propane in excess oxygen was investigated on Ni-ZrO2 （NZ） and sulfated Ni-ZrO2 （SNZ）, prepared by coprecipitation from a mixture of nickel nitrate-zirconium oxychloride followed by modifying with （NH4）2SO4. It was found that sulfated Ni-ZrO2 catalyst showed higher activity for the SCR of NO with propane than that of Ni-ZrO2. The structural and surface properties of catalysts were studied by XRD, BET, SEM and FT-IR of pyridine adsorption. The experimental results indicated that the modification of （NH4）2SO4 resulted in the generation of strong BrOnsted and Lewis acid sites and promoted the dispersion of the Ni species, which could lead to higher NO conversion and propane efficiency in NO reduction.     

High Activity SnO2／Al2O3 Catalyst for NO Reduction in the Presence of Oxygen

The novel sol-gel SnO2/Al2O3 catalysts for selective catalytic reduction NO by propene under lean burn condition were investigated. The results showed thatthe maximum NO conversion was 82% on the SnO2/Al2O3 (5%Sn) catalyst, and the presence of H20 and SO2 improved the catalytic activity at low temperature. The catalytic activity of NO2 reduction by propene is much higher than that of NO at the entire temperature range, and the maximum NO2 conversion reached nearly 100% around the temperature 425℃.     

Damage of aromatic amino acids by the atmospheric free radical oxidant NO3˙ in the presence of NO2˙, N2O4, O3 and O2

Analysis of the products formed in the reaction of NO(3)˙ with the N- and C-protected aromatic amino acids 1-5, which was performed under conditions that simulate exposure of biosurfaces to environmental pollutants, revealed insight how this important atmospheric free-radical oxidant can cause irreversible damage. In general, NO(3)˙ induced electron transfer at the aromatic ring is the exclusive initial pathway in a multi-step sequence, which ultimately leads to nitroaromatic compounds. In the reaction of NO(3)˙ with tryptophan 5 tricyclic products 12 and 13 are formed through an intramolecular, oxidative cyclization involving the amide moiety. In addition to this, strong indication for formation of N-nitrosamides was obtained, which likely result from reaction with N(2)O(4) through an independent non-radical pathway.     

Oxidative degradation and pyrolysis of polyvinyl chloride in binary mixtures of the system K,Na, Ca ‖ NO3, NO2, OH

Oxidative degradation and pyrolysis of polyvinyl chloride in the temperature range 200–500°C in binary mixtures containing sodium, potassium, and calcium nitrates and nitrites and calcium hydroxide were studied. A scheme of oxidative degradation of polyvinyl chloride and of binding of chlorine and carbon present in the polymer in the reactions of the degradation products with the mixture components was suggested.     

Enhancement of Activity of SnO2-doped In2O3/Al2O3 Catalyst for NO Reduction with Propene in the Presence of H2O and SO2

The selective catalytic reduction of nitrogen oxides by hydrocarbons (HC-SCR) has attracted much attention as an efficient way to remove NO in the presence of excess oxygen1-2. The metal oxides are the most promising catalysts for the SCR of NO because of their high activity and selectivity3-5. In the previous work, the metal oxides such as Ag, Sn, In, Co supported on alumina for NO reduction were investigated6-8, however, the HC-SCR is usually suppressed in the presence of H2O and S…     

EPR evidence for the restricted mobility of NO2 in gamma irradiated thorium nitrate pentahydrate Th(NO3)4·5H2O

Electron paramagnetic resonance (EPR) studies were conducted on gamma irradiated polycrystalline sample of thorium nitrate pentahydrate, Th(NO(3))(4)·5H(2)O, in the temperature range of 100-300 K. The most prominent species with triplet hyperfine structure in the EPR spectrum was identified as NO(2). The EPR spectrum gave evidence for the stabilization of NO(2) in at least three different sites slightly differing in spin Hamiltonian parameters (Site(1): g(x)=2.0042, g(y)=1.9911, g(z)=2.0020, A(x)=54.20 G, A(y)=48.50 G and A(z)=65.25 G; Site(2): g(x)=2.0042, g(y)=1.9911, g(z)=2.0020, A(x)=54.20 G, A(y)=48.50 G and A(z)=67.85 G; Site(3): g(x)=2.0045, g(y)=1.9911, g(z)=2.0015, A(x)=54.20 G, A(y)=49.05 G and A(z)=72.45 G). The EPR spectra for Site(1) revealed molecular dynamics of NO(2) from a slow motion region to fast motion region as the sample temperature was varied from 100 to 300 K. This led to a change in EPR spectrum from orthorhombic to axial, indicating preferred rotation of NO(2) molecule about the O-O bond direction. However, the NO(2) molecule at Site(2) was found to be rigid throughout the entire temperature range. The differences in the mobility of NO(2) molecules occupying the two sites could be attributed to the fact that in one case NO(2) was bonded to thorium or water and in the other case it was weakly bound. The NO(2) bound to thorium through two oxygen atoms or bound to thorium on one side through one oxygen atom and hydrogen bonded to water on the other side remains rigid throughout the entire temperature range, while NO(2) situated at interstitial sites or adsorbed on the surface exhibits mobility with increase in temperature above 100K.     

Modes of coordination and stereochemistry of the NO3 − anions in inorganic nitrates

Stereochemical features of 950 nitrate groups in the structures of 365 inorganic nitrates were analyzed using TOPOS software. The types of coordination of nitrate groups are systematized by means of Voronoi-Dirichlet polyhedra and the method of intersecting spheres. Terminal coordination (53% of the total number of nitrate groups), most of all terminal bidentate coordination (47%) was found to prevail. Bridging nitrate groups occur less frequently (20%). A considerable number of nitrate groups are not incorporated in the coordination sphere of the complexing atom but form H-bonds or bonds of mainly ionic nature (27%). A number of metal cations show clear-cut tendency for a certain mode of coordination of the NO₃ group. Criteria for classification of nitrate groups into four types (slightly distorted groups and groups with monodentate, bidentate and asymmetric type distortion) are proposed. Structural features of nitrate groups depending on the mode of coordination are considered. The geometry of mono- or bidentate nitrate groups can differ appreciably from the typical one because of participation of terminal oxygen atoms in ionic or hydrogen bonds. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 429–440, March, 2008.     

Pb（NO3）2 Mediated Synthesis of Pyrazine

Lead nitrate was used as an efficient catalyst in the oxidation and condensation reaction of hydroxy ketone with diamine leading to the formation of pyrazine derivatives in excellent yields.     

Reaction products and kinetics of the reaction of NO2 with γ-Fe2O3

The reaction of NO(2) with Fe(2)O(3) has relevance for both atmospheric chemistry and catalysis. Most studies have focused on hematite, α-Fe(2)O(3), as it is the thermodynamic stable state of iron oxide; however, other forms of Fe(2)O(3) naturally occur and may have different chemistries. In this study, we have investigated the reaction products and kinetics for NO(2) reacting with γ-Fe(2)O(3) powder using diffuse reflectance infrared Fourier transform spectroscopy and compared the results to those of previous studies of NO(2) reacting with α-Fe(2)O(3). Both α- and γ-Fe(2)O(3) produce surface-bound nitrate at the pressures examined in this study (24-212 mTorr); surface-bound nitrite products are observed at all pressures for γ-Fe(2)O(3) whereas nitrite was only observed on α-Fe(2)O(3) at lower pressures. Surface-bound NO(+) and Fe-NO products are observed on γ-Fe(2)O(3), which have not been observed with α-Fe(2)O(3). The reaction kinetics show a first-order dependence on NO(2) pressure and this is used to support the hypothesis of unimolecular reaction of adsorbed NO(2) with the γ-Fe(2)O(3) surface as the slow step in the reaction mechanism. The difference in product formation between NO(2) reacting with γ-Fe(2)O(3) and previous studies of α-Fe(2)O(3) illustrate the fact that care must be taken in generalizing reactivity of different polymorphs.     

Photoelectron spectrum of NO2−: SAC-CI gradient study of vibrational-rotational structures

Three-dimensional accurate potential energy surfaces around the local minima of NO₂⁻ and NO₂ were calculated with the SAC/SAC-CI analytical energy gradient method. Therefrom, the ionization photoelectron spectra of NO₂⁻, the equilibrium geometries and adiabatic electron affinity of NO₂, and the vibrational frequencies including harmonicity and anharmonicity of NO₂⁻ and NO₂ were obtained. The calculated electron affinity was in reasonable agreement with the experimental value. The SAC-CI photoelectron spectra of NO₂⁻ at 350 K and 700 K including the rotational effects were calculated using the Franck–Condon approximation. The theoretical spectra reproduced well the fine experimental photoelectron spectra observed by Ervin et al. (J. Phys. Chem. 1988, 92, 5405). The results showed that the ionizations from many vibrational excited states as well as the vibrational ground state are included in the experimental photoelectron spectra especially at 700 K and that the rotational effects are important to reproduce the experimental photoelectron spectra of both temperatures. The SAC/SAC-CI theoretical results supported the analyses of the spectra by Ervin et al., except that we could show some small contributions from the asymmetric-stretching mode of NO₂⁻. © 2018 Wiley Periodicals, Inc.     

Oxygen Spillover in the Conversion of NO on a Pd-Co/γ-Al2O3 Catalyst

Oxygen spillover was detected in the decomposition of NO on a Pd-Co/-Al₂O₃ catalyst obtained by the thermolysis of [Co(NH₃)₅Cl][PdCl₄].