- Product branching ratio of the HCCO + NO reaction
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Excimer laser photolysis of ketene precursor molocules followed by IR absorption spectroscopy were performed to study the reaction of ketenyl radical (HCCO) radicals with NO at room temperature. CO and CO2 were produced. Considering possible secondary chemistry, CO + (HCNO) was the main product channel, with a branching ratio of 0.88 ± 0.04:1 at 296 K. CO2 + (HCN) was a minor channel, with a branching ratio of 0.12 ±0.04:1. The relative quantum yield for HCCO production in the 193 nm photolysis of CH2CO was estimated to be 0.17 ± 0.02.
- Rim, Kwang Taeg,Hershberger, John F.
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- IR spectroscopic study of NOx adsorption and NOx-O2 coadsorption on Co2+/SiO2 catalysts
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Adsorption of nitrogen oxides (NO, NO2) and their coadsorption with oxygen on Co2+/SiO2 samples has been investigated by IR spectroscopy with a view to elucidating the mechanism of selective catalytic reduction (SCR) of NOx with hydrocarbons. A Co2+/SiO2 sample synthesized by ion exchange is characterized by a highly dispersed cobalt and a very weak surface acidity: CO is adsorbed only at low temperature (100 K) forming Co2+ - CO carbonyls [v(CO) = 2180 cm-1]. Adsorption of NO on Co2+/SiO2 leads to the formation of Co2+(NO)2 dinitrosyl complexes (1872 and 1804 cm-1) which are decomposed upon evacuation. Adsorption of NO2, as well as coadsorption of NO and O2, produce NO2 species weakly bound to the support (a band at 1681 cm-1) and N2O4 (a band at 1744 cm-1 with a shoulder at 1710 cm-1), the latter being adsorbed reversibly on both the support and the Co2+ ions. In the second case N2O4 is transformed into surface monodentate nitrates of Co2+ (a band at 1550-1526 cm-1) and partly into bridged nitrates (a band at ca. 1640 cm-1). The monodentate nitrates are stable with respect to evacuation up to 125°C and act as strong oxidising agents: they are reduced by NO, even at room temperature, and by methane at 100°C. In the latter case, organic nitro-compounds and isocyanate groups are registered as reaction products (probably intermediate compounds in SCR). The surface species obtained after NO and NO2 adsorption on Co2+/SiO2 prepared from cobalt acetate (active SCR catalyst) are essentially the same as those observed with the ion-exchanged sample. No monodentate nitrates, however, are formed during NO2 adsorption on a Co2+/SiO2 sample synthesized by impregnation with cobalt nitrate, which accounts for the lack of activity of this sample in the SCR.
- Djonev, Boyan,Tsyntsarski, Boyko,Klissurski, Dimitar,Hadjiivanov, Konstantin
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- 14N/15N kinetic isotope effect in the association reaction O(3P)+NO+Ar→NO2+Ar
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The termolecular rate constants for the O(3P)+14NO+Ar→14NO2+Ar and O(3P)+15NO+Ar→15NO2+Ar reactions were determined under room temperature bulk conditions. O(3P) was produced by the pulsed photodissociation of SO2 at 210.4 nm and was monitored by two-photon laser-induced fluorescence at 225.7 nm. The rate constants for 14NO and 15NO were determined to be 5.4±0.2 and 6.1±0.3×10-32cm6s-1, respectively. The error limits are twice the standard errors (S.E.). This isotope effect is opposite to that expected from a statistical model but is similar to that observed in the O3 formation reactions from O(3P) and O2.
- Umemoto, Hironobu,Tanaka, Kunikazu,Oguro, Shigeki,Ozeki, Ryoji,Ueda, Masashi
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- Use of a Stopped-flow Technique to measure the Rate Constants at Room Temperature for Reactions between the Nitrate Radical and Various Organic Species
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A stopped-flow apparatus, in which NO3 was detected by optical absorption at λ = 662 nm, has been used to measure overall rate constants at room temperature for reaction of NO3 in systems involving ethene, simple alkanes and chlorinated methanes.Modelling of the reaction with ethene led to a rate constant for the primary step of (1.7 +/- 0.5) * 10 -16 cm3 molecule -1 s-1.However, for H-atom abstraction by NO3 from the saturated organic species, the extensive and largely unquantified secondary chemistry occuring over reaction times of 5 - 20 s meant that only upper limits for the primary rate constants could be accurately assessed (the stoicheiometric factor being assumed to be two or more).The values thus obtained at room temperature were (in units of 10-17 cm3 molecule -1 s-1) 2.7 +/- 0.2, 4.8 +/- 1.7, 60 +/- 10, 0.85 +/- 0.25, 0.48 +/- 0.10 and 6.0 +/- 0.5 for ethane, propane, isobutane (2-methylpropane), acetone, dichloromethane and chloroform.For the reactions of NO3 with ethane and propane, modelling of the kinetics led to estimates of lower limit of the primary rate constants of ethane and propane, modelling of the kinetics led to estimates of lower limits of the primary rate constants of (1.1 +/- 0.2) and (2.2 +/- 0.2) * 10-17 cm3 molecule-1 s-1.No reaction was observed between NO3 and methane or chloromethane, suggesting upper limits (based on the noise levels) for the overall rate constants of these reactions of 8 * 10-19 and 1* 10-18 cm3 molecule-1 s-1.
- Boyd, Andrew A.,Canosa-Mas, Carlos E.,King, A. Douglas,Wayne, Richard P.,Wilson, Mark R.
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- Rate Coefficient for the Reaction NO + NO3 -> 2NO2 between 223 and 400 K
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The rate coefficient for the reaction NO + NO3 -> 2NO2 (1) has been measured in a discharge flow system between 223 and 400 K.Measurements were made by laser-induced fluorescence detection of NO3 in the presence of excess NO or by chemiluminescent detection of NO in the presence of excess NO3.Analysis of the kinetics was made using a modified form of the usual flow equations, which explicitly accounts for the viscous pressure drop.The rate coefficients are in excellent agreement with the determination of Sander and Kircher (Chem.Phys.Lett. 1986, 126, 149).The recommended rate coefficient from this study and that of Sander and Kircher can be adequately described by the expression k1 = (1.65 +/- 0.35) x 10-11e cm3 molecule-1 s-1.The possible effects of secondary chemistry on the rate coefficients determined are discussed.
- Tyndall, G. S.,Orlando, J. J.,Cantrell, C. A.,Shetter, R. E.,Calvert, J. G.
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- Reaction of OH with HO2NO2 (Peroxynitric Acid): Rate Coefficients between 218 and 335 K and Product Yields at 298 K
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HO2NO2 (peroxynitric acid, PNA) has an important role in determining the ozone abundance and its changes over time in the lower stratosphere. Rate coefficients (k3(T)) for the reaction of OH with PNA in the gas phase were
- Jimenez, Elena,Gierczak, Tomasz,Stark, Harald,Burkholder, James B.,Ravishankara
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- Manganese porphyrins as redox-coupled peroxynitrite reductases
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Superoxide (O2.-) and peroxynitrite (ONOO-) have been implicated in many pathophysiological conditions. To develop novel catalysts that have both ONOO- decomposition and O2.- dismutase activity, and to understand the mechanisms of these processes, we have explored the reactivity of 5,10,15,20-tetrakis- (N-methyl-4'-pyridyl)porphinatomanganese(III) [Mn(III)TMPyP] toward ONOO- and 02.-. The reaction of Mn(III)TMPyP with ONOO- to generate an oxomanganese(IV) porphyrin species [(oxoMn(IV)] is fast, but Mn(III)TMPyP is not catalytic for ONOO- decomposition because of the slow reduction of oxoMn(IV) back to the Mn(III) oxidation state. However, biological antioxidants such as ascorbate, glutathione, and Trolox rapidly turn over the catalytic cycle by reducing oxoMn(IV). Thus, Mn(III)TMPyP becomes an efficient peroxynitrite reductase when coupled with ascorbate, glutathione, and Trolox (k(c) ~2 x 106 M-1 s-1), though the direct reactions of ONOO- with these biological antioxidants are slow (88 M-1 s-1, 5.8 x 102 M-1 s-1 and 33 M-1 s-1, respectively). Mn(III)TMPyP is known to catalyze the dismutation of O2.-, and using stopped-flow spectrophotometry, the rate of Mn(III)TMPyP-catalyzed dismutation has been measured directly (k(c) = 1.1 x 107 M-1 s-1). Further, O2.-, like the biological antioxidants, rapidly reduces oxoMn(IV) to the Mn(III) oxidation state (k ~108 M-1 s-1), transforming Mn(III)TMPyP into a O2.--coupled ONOO- reductase. Under conditions of oxidative stress and reduced antioxidant levels, Mn(III)TMPyP may deplete O2.- primarily as a function of its ONOO- reductase activity, and not through its O2.- dismutase activity.
- Lee, Jinbo,Hunt, Julianne A.,Groves, John T.
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- Extracellular hydrogen peroxide measurements using a flow injection system in combination with microdialysis probes – Potential and challenges
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There is a strong need for techniques that can quantify the important reactive oxygen species hydrogen peroxide (H2O2) in complex media and in vivo. We combined chemiluminescence-based H2O2 measurements on a commercially available flow injection analysis (FIA) system with sampling of the analyte using microdialysis probes (MDPs), typically used for measurements in tissue. This allows minimally invasive, quantitative measurements of extracellular H2O2 concentration and dynamics utilizing the chemiluminescent reaction of H2O2 with acridinium ester. By coupling MDPs to the FIA system, measurements are no longer limited to filtered, liquid samples with low viscosity, as sampling via a MDP is based on a dynamic exchange through a permeable membrane with a specific cut-off. This allows continuous monitoring of dynamic changes in H2O2 concentrations, alleviates potential pH effects on the measurements, and allows for flexible application in different media and systems. We give a detailed description of the novel experimental setup and its measuring characteristics along with examples of application in different media and organisms to highlight its broad applicability, but also to discuss current limitations and challenges. The combined FIA-MDP approach for H2O2 quantification was used in different biological systems ranging from marine biology, using the model organism Exaiptasia pallida (light stress induced H2O2 release up to ~ 2.7 μM), over biomedical applications quantifying enzyme dynamics (glucose oxidase in a glucose solution producing up to ~ 60 μM H2O2 and the subsequent addition of catalase to monitor the H2O2 degradation process) and the ability of bacteria to modify their direct environment by regulating H2O2 concentrations in their surrounding media. This was shown by the bacteria Pseudomonas aeruginosa degrading ~ 18 μM background H2O2 in LB-broth. We also discuss advantages and current limitations of the FIA-MDP system, including a discussion of potential cross-sensitivity and interfering chemical species.
- Mo?hammer, Maria,Schrameyer, Verena,Jensen, Peter ?.,Koren, Klaus,Kühl, Michael
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- Complexes formed between nitrilotris(methylenephosphonic acid) and M2+ transition metals: Isostructural organic-inorganic hybrids
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Nitrilotris(methylenephosphonic acid) (NTP, [N(CH2PO3H2)3]) recently has been found to form three-dimensional porous structures with encapulation of templates as well as layered and linear structures with template intercalation. It was, therefore, of interest to examine the type of organic-inorganic hybrids that would form with metal cations. Mn(II) was found to replace two of the six acid protons, while a third proton bonds to the nitrilo nitrogen, forming a zwitter ion. Two types of compounds were obtained. When the ratio of acid to Mn(II) was less than 10, a trihydrate, Mn[HN(CH2PO3H)3(H2O)3] (2) formed. Compound 2 is monoclinic P21/c, with a = 9.283(2) A, b = 16,027(3) A, c = 9,7742(2) A, β = 115.209(3)°, V = 1315,0(5) A3, and Z= 4. The Mn atoms form zigzag chains bridged by two of the three phosphonate groups, The third phosphonate group is only involved in hydrogen bonding. The metal atoms are octahedrally coordinated with three of the sites occupied by water molecules, Adjacent chains are hydrogen-bonded to each other through POH and HN donors, and the additional participation of all the water hydrogens in H-bonding results in a corrugated sheetlike structure. Use of excess NTP at a ratio to metal of 10 to 1 yields an anhydrous compound Mn[HN(CH2PO3H)3] (1), P21/n, a = 9,129(1) A, b = 8,408(1) A, c = 13,453(1) A, β = 97,830(2)°, V = 1023,0(2) A3, and Z = 4, Manganese is five coordinate forming a distorted square pyramid with oxygens from five different phosphonate groups. The sixth oxygen is 2,85 A from an adjacent Mn, preventing octahedral coordination. All the protonated atoms, three phosphonate oxygens and N, form moderately strong hydrogen bonds in a compact three-dimensional structure. The open-structured trihydrate forms a series of isostructural compounds with other divalent transition metal ions as well as with mixed-metal compositions. This is indicative that the hydrogen bonding controls the type of structure formed irrespective of the cation.
- Cabeza, Aurelio,Ouyang, Xiang,Sharma, C. V. Krishnamohan,Aranda, Miguel A. G.,Bruque, Sebastian,Clearfield, Abraham
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- Synthesis and Identification by Infrared Spectroscopy of Gaseous Nitryl Bromide
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The reactions at 298 K of gaseous N2O5 with NaBr(s) or with BrNO(g) in 1 atm of helium were followed by using Fourier transform infrared spectroscopy.In both cases, the formation of infrared absorption bands at 787, 1292, and approximately 1660 cm-1
- Finlayson-Pitts, Barbara J.,Livingston, Frank E.,Berko, Henry N.
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- Mesocrystalline anatase nanoparticles synthesized using a simple hydrothermal approach with enhanced light harvesting for gas-phase reaction
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Mesocrystalline TiO2 nanoparticles were synthesized using a hydrothermal approach. A simple two-step procedure at low temperature (2 crystalline phase. The mesocrystalline structure of the anatase aggregates was clearly evidenced by HRTEM and SAED results. The mesocrystalline nanopowders exhibit a mesoporous structure with a surface area and pore volume of 63.5 m2 g-1 and 0.22 cm3 g-1, respectively. Ultraviolet (UV) and visible light (Vis) absorption ability were recorded. The combined high effectiveness and selectivity for the NOx abatement of the new mesocrystalline photocatalyst are reported. It is worth remarking that the maximised selectivity values reached for the NOx process are reported for the first time and could be associated with the mesoporous nature of the anatase photocatalyst.
- Balbuena, José,Calatayud, José Miguel,Cruz-Yusta, Manuel,Pardo, Pablo,Martín, Francisco,Alarcón, Javier,Sánchez, Luis
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- Kinetics and mechanism of the thermal decomposition of M(NO3)2·nH2O (M = Cu, Co, Ni)
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This paper presents the results of simultaneous DTA-TG-DTG and DSC studies on the thermal decomposition of Cu(NO3)2·3H2O, Co(NO3)2·6H2O and Ni(NO3)2·6H2O in
- Zivkovic,Zivkovic,Grujicic
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- Disproportionation reaction of NO2/N2O4 with a Ru(II) porphyrin
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A Ru(II) porphyrin rapidly reacts with NO2/N2O 4 with the formation of a stable Ru(II) nitrosyl nitrato complex.
- Kang, Yanlong,Zyryanov, Grigory V.,Rudkevich, Dmitry M.
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- First spectroscopic observation of gas-phase HOONO
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The three-body association reaction of hydroxyl radical with NO2, OH + NO2 + M → HONO2 + M is one of the most important processes in the chemistry of the Earth's lower atmosphere. The first direct spectroscopic observation of HOONO formed in the reaction of OH with NO2 was reported. Rich vibrational structure, consistent with the existence of several HOONO conformers, was observed. A tentative vibrational assignment of the observed bands was suggested, although the complete assignment is not possible without further spectroscopic information. The ratio HOONO/HONO2 formed in the reaction of OH with NO2 was ~ 5% at 253 K and 20 torr.
- Nizkorodov,Wennberg
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- The synergy between Fe and Ru in N2O decomposition over FeRu-FER catalysts: A mechanistic explanation
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Fe-FER is an active catalyst for the abatement of N2O in the tail gas of nitric acid plants. The activity of Fe-FER can be increased if Ru is added as a second active component. This is a surprising finding, because noble metals are usually strongly inhibited by NO, which is always present in tail gas. Yet the bimetallic FeRu-FER catalyst is more active than the sum of the components, Fe-FER and Ru-FER. A synergy between Fe and Ru can explain this phenomenon. This work discusses the role of Fe and Ru in the reaction mechanism as well as the interplay of these two components. In situ IR measurements show that the preferential adsorption of NO and its reaction products on Fe in the bimetallic catalyst reduces the inhibiting effect of NO on the Ru component; this effect largely contributes to the synergy between Fe and Ru. Moreover, in situ X-ray absorption data are presented, which allow for tracing the average oxidation state of the two active components Fe and Ru under reaction conditions.
- Pirngruber, Gerhard D.,Frunz, Lukas,Pieterse, Johannis A.Z.
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- Photolysis of nitric acid at 308 nm in the absence and in the presence of water vapor
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We have re-examined the NOx channels from the 308 nm gas-phase photolysis of nitric acid (HNO3) by using excimer laser photolysis combined with cavity ring-down spectroscopy. The photolysis products were monitored in the 552-560 and 640-648 nm regions. Direct comparison of the photolysis product spectrum in the 640-648 nm region with literature vibronic band origins and line intensities in electronically excited NO2 (NO2) suggests that NO2 is not formed from HNO3 photolysis at 308 nm. A comparison of the photolysis product spectrum in the 552-560 nm region with a standard NO2 spectrum indicates that ground-state NO2 is a photolysis product. We have determined the NO2 quantum yield from the 308 nm HNO3 photolysis. We also investigated HNO3 photolysis in the presence of water vapor. For equilibrated HNO3/H2O mixtures, we did not observe significant variation of product absorption around 552 nm with delay times between the firing of the photolysis and the probe lasers. Transient product absorption measurements at 342.0 and 343.5 nm (respective wavelengths where the peak and valley of HONO absorptions are located) are consistent with ground-state NO2 being the predominant NOx product from the 308 nm photolysis of a HNO3/H2O mixture. Atmospheric implications are also discussed.
- Zhu, Lei,Sangwan, Manuvesh,Huang, Li,Du, Juan,Chu, Liang T.
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- Observation of gas-phase peroxynitrous and peroxynitric acid during the photolysis of nitrate in acidified frozen solutions
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The photolysis of nitrate embedded in ice and snow can be a significant source of volatile nitrogen oxides affecting the composition of the planetary boundary layer. In this work, we examined the nitrogen oxides evolved from irradiated frozen solutions containing nitrate. Products were monitored by cavity ring-down spectroscopy (CRDS), NO-O3 chemiluminescence (CL), and chemical ionization mass spectrometry (CIMS). Under acidic conditions, the nitrogen oxides volatilized were mainly in the form of NOz, i.e., nitrous (HONO), nitric (HONO2), peroxynitrous (HOONO), and peroxynitric acid (HO2NO2). Identification of acidic nitrogen oxides by CIMS and possible HOONO, HONO2 and HO 2NO2 formation pathways are discussed.
- Abida, Otman,Mielke, Levi H.,Osthoff, Hans D.
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- Overtone dissociation of peroxynitric acid (HO2NO2): Absorption cross sections and photolysis products
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Band strengths for the second (3vOH) and third (4VOH) overtones of the OH stretch vibration of peroxynitric acid, HO 2NO2 (PNA) in the gas-phase were measured using Cavity Ring-Down Spectroscopy (CRDS). Both OH overtone transitions show diffuse smoothly varying symmetrical absorption profiles without observable rotational structure. Integrated band strengths (base e) at 2% K were determined to be S3vOH = (5.7 ± 1.1) × 10-20 and S 4vOH = (4.9 ± 0.9) × 10-21 cm2 molecule-1 cm-1 with peak cross sections of (8.8 ± 1.7) × 10-22 and (7.0 ± 1.3) × 10-23 cm2 molecule-1 at 10086.0 ± 0.2 cm-1 and 13095.8 ± 0.4 cm-1, respectively, using PNA concentrations measured on line by Fourier-transform infrared and ultraviolet absorption spectroscopy. The quoted uncertainties are 2σ (95% confidence level) and include estimated systematic errors in the measurements. OH overtone spectra measured at lower temperature, 231 K, showed a narrowing of the 3vOH band along with an increase in its peak absorption cross section, but no change in S3vOH to within the precision of the measurement (±9%). Measurement of a PNA action spectrum showed that HO2 is produced from second overtone photodissociation. The action spectrum agreed with the CRDS absorption spectra. The PNA cross sections determined in this work for 3v OH and 4vOH will increase calculated atmospheric photolysis rates of PNA slightly.
- Stark, Harald,Brown, Steven S.,Burkholder, James B.,Aldener, Mattias,Riffault, Veronique,Gierczak, Tomasz,Ravishankara
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- Time-dependent Chemiluminescence from the Surface-catalyzed Recombination of O and NO on Polycrystalline Ni
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The near-infrared chemiluminescence produced by the surface-catalyzed recombination of nitric oxide with a supersonic beam of atomic oxygen on polycrystalline nickel has been studied.The dependence of the luminescence on time, substrate temperature, O and NO fluxes and pre-exposure to the O atom beam has been investigated.The spectrum of the luminescence has also been determined.Strong initial luminescence was observed decaying with time to a steady state.The use of argon-ion bombardement to clean the sample prior to each experiment was essential to the observation of this time-dependent luminescence.The initial luminescence shows a strong dependence on the substrate temperature, increasing by a factor of 80 when the substrate temperature is reduced from 300 to 195 K.The luminescence showed an initial first-order dependence on the atomic oxygen and nitric oxide fluxes, before levelling off at higher fluxes.The spectrum of the luminescence shows intensity rising from a threshold of 530 nm to a maximum at 800 nm, which is shifted significantly towards longer wavelengths compared to that from the termolecular gas-phase recombination of O and NO.Pre-exposure of the substrate to the O-atom beam suggests that a monolayer of chemisorbed oxygen, which reduces both the binding energy and dissociative adsorption of NO on the substrate, is resposible for the production of a weakly bound electronically excited NO2 which may leave the surface and emit light.A mechanism involving surface poisoning by NO2 product molecules has been suggested.
- Ardebili, M. H. Parviz,Grice, Roger,Hughes, Christopher J.,Whitehead, J. Christopher
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- Measurement of the V-T energy transfer rates of highly excited 2A1 NO2
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Production of electronic ground state NO2 (2A1) from 248 nm photolysis of HNO3 was detected by laser induced fluorescence (LIF).A growth in the LIF signal was observed following the photolysis and has been interpreted as the relaxation of NO2 through the higher vibrational levels of the X(2A1) state; an energy region where the probe laser photodissociates the NO2 instead of inducing fluorescence.The rate coefficients for NO2 relaxation through these high vibrational levels were determined by fits of time resolved LIF signal to a stepladder kinetic model.The results of the kinetic analysis suggest that the observed relaxation begins at the 2B2 threshold near 9500 cm-1 and extends downward through approximately 5 vibrational levels of the ground electronic surface.The derived quenching rate coefficients (in units of 10-12 cm3 molecule-1 s-1) are 0.51+/-0.05, 1.0+/-0.1, 1.4+/-0.2, 2.6+/-0.6, and 8.7+/-1.1 for Ar, He, N2, O2, and CO2 collision partners, respectively.The discrepancies between these coefficients and previous literature values are rationalized in terms of a dependence of the vibrational relaxation rate on total internal energy.
- Mazely, Troy L.,Friedl, Randall R.,Sander, Stanley P.
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- Kinetics of the Reaction NO + O3 -> NO2 + O2 from 212 to 422 K
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The reaction of nitric oxide with ozone has been studied over a wide range of temperature (212-422 K) by utilizing the discharge flow / mass spectrometric technique.The pseudo-first-order decay of ozone was measured in the presence of a large excess concentration of nitric oxide.The value of the bimolecular rate coefficient at 299 K and the Arrhenius expression determined are k = (1.80 +/- 0.08 ) X 1E-14 cm3 molecule-1 s-1 (T = 299 K) and k = (3.16 +/- 0.90) X 1E-12 exp(-(1566 +/- 80)/T) cm3 molecule-1 s-1.These results are compared with previous measurements.
- Ray, Gary W.,Watson, Robert T.
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- Stereodynamics of Photon-induced Reactions via Doppler-resolved Laser-induced Fluorescence Spectroscopy: Photodissociation of HONO2 and the Reaction of O(1D) with CH4
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The application of polarised, Doppler-resolved laser-induced fluorescence (LIF) probing of the products scattered from photon-induced 'half-collision' (photodissociation) and 'full-collision' (bimolecular reaction) processes is developed to include the velocity dependence of their stereodynamics.Fourier-transform inversion procedures are used to derive the products' speed distributions W(v') and vector correlations βij(v') (a) in the photodissociation of HONO2 and (b) in the bimolecular reaction of O(1D) with CH4.In the former example, they provide new insight into the stereodynamics of the photodissociation HONO2 + hν -> (v=0,N) + NO2 ().In the latter, together with newly developed LAB -> CM simulation methods, they provide new insight into the stereodynamics of the reaction O(1D) + CH4 -> OH(v=4,N) + CH3.The OH is shown to be generated with its rotational angular momentum J', constrained to lie in a plane directed perpendicular to its centre-of-mass relative velocity, k'.
- Brouard, Mark,Duxon, Simon,Enriquez, Pedro A.,Simons, John P.
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- EXCESSIVELY COPPER ION-EXCHANGED ZSM-5 ZEOLITES AS HIGHLY ACTIVE CATALYSTS FOR DIRECT DECOMPOSITION OF NITROGEN MONOXIDE
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Repeated ion exchange of the ZSM-5 zeolite using aqueous copper(II) acetate solution was found to bring about excess loading of copper ions above 100percent of exchange level.The catalytic activities of the resulting Cu-ZSM-5 zeolites for direct decomposi
- Iwamoto, Masakazu,Yahiro, Hidenori,Mine, Yoshihiro,Kagawa, Shuichi
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- Molten sodium nitrite-sodium nitrate-potassium nitrate eutectic: The reactions and spectra of iron(III), cobalt(II), nickel(II) and copper(II) compounds
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In the sodium nitrite sodium nitrate-potassium nitrate ternary eutectic, iron(III), cobalt(II) and nickel(II) chlorides were found to undergo Lux Flood acid base reactions to form their most stable oxides, which were insoluble, while copper(II) sulphate reacted to form a basic nitrate. The stoichiometry of the reactions in the presence of the competing basic anions was much more similar to those found in pure nitrite than in pure nitrate melts, but the oxidation of nitrite to nitrate, possibly via nitric oxide and nitrogen dioxide, was shown to be important. The green solution of nickel(II) chloride had a spectrum which was much more similar to that in pure nitrite than in pure nitrate melts. Octahedral coordination by nitro, nitrito and nitrato ligands is suggested, in the ratio 2:1:3.
- Eweka,Kerridge
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- Thermal Decomposition of Peroxyacetyl Nitrate in the Presence of O2, NO2 and NO
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The thermal decomposition of pure PAN in N2 as well as in the presence of added O2, NO2 and NO was studied at 1 atm pressure.In addition to methyl nitrate, NO2 was a significant N-product of pure PAN in N2 thermal decomposition.In the presence of sufficiently large amounts of O2, no methyl nitrate was formed at 333 K, indicating that the homolytic PAN decay to methyl nitrate and carbon dioxide is not occurring.In the presence of NO (in contrast to former studies) methyl nitrite was found to be the major organo-nitrogen compound instead of methyl nitrate.The systemPAN-NO-N2 allowed the determination of the rate constant 3.1*10-4 s-1 at 298 K for reaction (1): PAN --> CH3COO2 + NO2, in agreement with prior studies.Computer simulations based on the free radical mechanism starting with reaction (1) fitted very well the experimental results.Keywords: PAN; Thermal decomposition; O2; NO2; NO.
- Roumelis, Nikolaos,Glavas, Sotirios
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- MANUFACTURING PROCESS OF SODIUM HYDROXIDE AND NITRIC ACID FROM THERMOCHEMICALLY SPLIT SODIUM NITRATE.
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For the manufacture of sodium hydroxide and nitric acid a new thermochemical process of splitting sodium nitrate has been proposed which consists of (i) splitting of sodium nitrate by iron(III) oxide, (ii) hydrolysis of sodium ferrate, and (iii) absorption of nitrogen dioxide into water. Key reactions (i) and (ii) have experimentally been verified. The overall heat requirement for the process is discussed on the basis of a material and heat flow-sheet of the process constructed.
- Takeuchi
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- A novel composite of α-MoO3/BiVO4 for triethylamine selective detection
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One-dimensional α-MoO3 nanorods were synthesized by a hydrothermal method and BiVO4 nanoparticles were grown directly onto the α-MoO3 nanorods using a simple metal organic decomposition process in order to construct an α-MoO3/BiVO4 composite with a heterojunction, for the fabrication of a rapid response triethylamine (TEA) sensor. The morphology and structure of the composite were characterized via various spectral techniques and the sensing properties of the sensor for TEA were investigated via resistance measurements. The results showed that the response of the 16Mo/Bi composite to 20 ppm TEA was 1.86 times and 15 times higher than those of α-MoO3 and BiVO4, respectively, at an optimum operating temperature of 125 °C. The enhancement can be ascribed to the existence of a heterojunction between α-MoO3 and BiVO4, creating an additional barrier at the interface of the heterojunction, and this increases the resistance of the composite in air and decreases the resistance in TEA, thus enhancing the response of the composite to TEA.
- Bai, Shouli,Han, Jingyi,Fan, Xiangxiang,Guo, Jian,Luo, Ruixian,Li, Dianqing,Chen, Aifan
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- Reaction of cyclic nitroxides with nitrogen dioxide: The intermediacy of the oxoammonium cations
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Piperidine and pyrrolidine nitroxides, such as 2,2,6,6-tetramethylpiperidinoxyl (TPO) and 3-carbamoylproxyl (3-CP), respectively, are cell-permeable stable radicals, which effectively protect cells, tissues, isolated organs, and laboratory animals from radical-induced damage. The kinetics and mechanism of their reactions with .OH, superoxide, and carbon-centered radicals have been extensively studied, but not with .NO2, although the latter is a key intermediate in cellular nitrosative stress. In this research, .NO2 was generated by pulse radiolysis, and its reactions with TPO, 4-OH-TPO, 4-oxo-TPO, and 3-CP were studied by fast kinetic spectroscopy, either directly or by using ferrocyanide or 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate), which effectively scavenge the product of this reaction, the oxoammonium cation. The rate constants for the reactions of .NO2 with these nitroxides were determined to be (7-8) × 108 M-1 s-1, independent of the pH over the range 3.9-10.2. These are among the highest rate constants measured for .NO2 and are close to that of the reaction of .NO2 with .NO, that is, 1.1 × 109 M-1 s-1. The hydroxylamines TPO-H and 4-OH-TPO-H are less reactive toward .NO2, and an upper limit for the rate constant for these reactions was estimated to be 1 × 105 M-1 s-1. The kinetics results demonstrate that the reaction of nitroxides with .NO2 proceeds via an inner-sphere electron-transfer mechanism to form the respective oxoammonium cation, which is reduced back to the nitroxide through the oxidation of nitrite to .NO2. Hence, the nitroxide slows down the decomposition of .NO2 into nitrite and nitrate and could serve as a reservoir of .NO2 unless the respective oxoammonium is rapidly scavenged by other reductant. This mechanism can contribute toward the protective effect of nitroxides against reactive nitrogen-derived species, although the oxoammonium cations themselves might oxidize essential cellular targets if they are not scavenged by common biological reductants, such as thiols.
- Goldstein, Sara,Samuni, Amram,Russo, Angelo
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- Reactions of HO2 with NO and NO2 studied by Mid-infrared Laser Magnetic Resonance
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The technique of mid-infrared laser magnetic resonance spectroscopy combined with a discharge-flow system has been used to study reactions of the HO2 radical at total pressure up to 13 Torr, corresponding to conditions in the middle stratosphere.The validity of the technique was confirmed by the detrmination of a rate coefficient of (8.5 +/- 1.3) * 10-12 cm3 molec-1 s-1 at 297 K for the reaction HO2 + NO -> OH + NO2 in excellent agreement with previous studies.The reaction HO2 + NO2 + M -> HO2NO2 + M was also studied.For M = He, the rate coefficient is (6.0 +/- 1.5) * 10-32 cm6 molec-2 s-1 at 297 K, while the data for M = Ar were fitted by the expression 1.24 * 10-31 (T/300)-2.37 +/- 0.16 cm6 molec-2 s-1 between 275 and 326 K.
- Jemi-Alade, Allan A.,Thrush, Brian A.
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- Studies with ClONO2: Thermal Dissociation Rate and Catalytic Conversion to NO Using an NO/O3 Chmiluminescence Detector
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A NO/O3 chemiluminescence detector equipped with a gold catalyst is adapted to provide a measure of the thermal decomposition rate of ClONO2 in an N2/O2 gas mixture and, in a related way, provide the absolute concentration of ClONO2 in a flowing gas stream.The apptoach is to add ClONO2, in the parts per million by volume (ppmv) range, to the flow stream of the detector in the presence of excess NO.As the sample is heated, ClONO2 is thermally dissociated and the subsequent scavenging reaction of ClO with NO produces Cl and NO2.Cl goes on to react with ClONO2 to form NO3 which, in turn, reacts with NO to produce NO2.The loss of NO from the flow is precisely monitored downstream in the detector by the change in the chemiluminescence produced in the reaction of NO with reagent O3.If the reaction rates with NO are given, the NO loss at fixed temperature can be modeled to yield a dissociation rate constant for ClONO2.Results were obtained for temperatures between 353 and 413 K and for pressures in the range of 66-160 Torr (8.8-21.3 kPa).The data is best fit by the expression 1E-6.16exp(-90.7 kJmol-1/RT)cm3s-1molecule-1, which is in good agreement with earlier results.When combined with the rate constant for the association reaction of ClO and NO2, these results yield a larger equilibrium constant for the reactiothan indicated in previous direct measurements.A value for Δaf289.15 for ClONO2 of 22.9 kJmol-1 is obtained from a third-law thermochemical analysis of the data.The initial ClONO2 concentration in the sample is assumed to equal the absolute loss of NO measured when the dissociation and scavenging reactions have gone to completion.This affords the opportunity to calibrate the efficienty of other methods for the detection of ClONO2.Results are presented for the conversion efficienty of ClONO2 to NO found for a gold catalyst at 573 K with CO present as a reducing agent.
- Anderson, L. C.,Fahey, D. W.
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- Parahalogenated phenols accelerate the photochemical release of nitrogen oxides from frozen solutions containing nitrate
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The photolysis of nitrate anion (NO3-) contained in surface ice and snow can be a regionally significant source of gas-phase nitrogen oxides and affect the composition of the planetary boundary layer. In this study, the photochemical release of nitrogen oxides from frozen solutions containing NO3- in the presence of organic compounds was investigated. Gas-phase nitrogen oxides were quantified primarily by NO-O 3 chemiluminescence detection of NO and NOy (=NO + NO 2 + HONO + HNO3 + -PAN + -AN...) and cavity ring-down spectroscopy of NO2 and total alkyl nitrates (-AN). The photochemical production of gas-phase NOy was suppressed by the presence of formate, methanesulfonate, toluene, or phenol. In contrast, para-halogenated phenols (in the order of Cl > Br > F) promoted the conversion of NO 3- to gas-phase NOy, rationalized by acidification of the ice surface.
- Abida, Otman,Osthoff, Hans D.
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- Identification of BrONO as the Major Product in the Gas-Phase Reaction of Br with NO2
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Products of the gas-phase reaction of Br atoms with NO2 have been quantitatively determined at temperatures between 215 and 300 K in an environmental chamber interfaced to an FT-IR spectrometer. The major product of the reaction (yield > 75%) was found to be the cis isomer of BrONO, which was identified and quantified by means of its N=O stretching fundamental at 1660 cm-1; this represents the first gas-phase detection of this species. Although rapid thermal decomposition back to Br and NO2 precludes its detection at room temperature (lifetime 2 was found to be an important fate of BrONO at low temperatures. The rate coefficient for this process was found to increase with decreasing pressure, indicative of a heterogeneous process. At 700 Torr, this isomerization rate was (0.013 ± 0.003) s-1, independent of temperature over the range 218-243 K. Evidence was also obtained for rapid reactions between Br atoms and both BrONO and BrNO2 (10-10 > k > 10-11 cm3 molecule-1 s-1).
- Orlando, John J.,Burkholder, James B.
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- Kinetic Studies of the Reactions of IO Radicals Determined by Cavity Ring-Down Spectroscopy
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We demonstrate the application of cavity ring-down spectroscopy (CRDS) to the measurement of concentrations of IO radical and of reaction rate coefficients for the reaction systems, IO + IO and IO + NO, using the source reaction, O(3P) + CF3I. By monitoring IO radicals, we obtain the 295 K rate coefficients, k(O + CF3I → IO + CF3) = (5.8 ± 1.5) × 10-12 cm3 molec-1 s-1; k(IO + IO) = (1.0 ± 0.3) × 10-10 cm3 molec-1 s-1, and k(IO + NO) = (1.9 ± 0.5) × 10-11 cm3 molec-1 s-1 at the pressures of 1250 Pa (9.4 Torr) and 4000 Pa (30.1 Torr). For the IO A 2Π3/2 - X 2Π3/2 (2, 0) bandhead at 445.04 nm we have determined an absorption cross-section, σ = (7.3 ± 0.7) × 10-17 cm2. Error limits indicate the confidence of two standard deviations and propagate the uncertainty in the absorption cross-section.
- Atkinson, Dean B.,Hudgens, Jeffrey W.,Orr-Ewing, Andrew J.
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- Experimental and quantum chemical studies of a new organic proton transfer compound, 1H-imidazole-3-ium-3-hydroxy-2,4,6-trinitrophenolate
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A new proton transfer compound, 1H-imidazole-3-ium-3-hydroxy-2,4,6-trinitrophenolate (IMHTP), was crystallized by slow evaporation-solution growth technique. 1H and 13C NMR spectral studies confirm the molecular structure of the grown crystal. Single crystal X-ray diffraction study confirms that IMHTP crystallizes in monoclinic system with space group P21/c. Thermal curves (TG/DTA) show that the material is thermally stable up to 198 °C. The crystal emits fluorescence at 510 nm, proving its utility in making green light emitting materials in optical applications. The stable molecular structure was optimized by Gaussian 09 program with B3LYP/6-311++G(d,p) level of basis set. The frontier molecular orbital study shows that the charge transfer interaction occurs within the complex. The calculated first-order hyperpolarizability value of IMHTP is 44 times higher than that the reference material, urea. The electrostatic potential map was used to probe into electrophilic and nucleophilic reactive sites present in the molecule.
- Dhamodharan,Sathya,Dhandapani
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- 308 nm photolysis of nitric acid in the gas phase, on aluminum surfaces, and on ice films
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We have studied the photolysis of nitric acid (HNO3) in the gas phase at 253 and 295 K, on aluminum surfaces at 253 and 295 K, and on ice films at 253 K, by using 308 nm excimer laser photolysis combined with cavity ring-down spectroscopy. We monitored both the ground-state NO2 and the electronically excited NO2, NO2*, produced from the HNO3 photolysis. NO2* + OH is a predominant photolysis pathway (if not the only photolysis pathway) from the gas-phase photolysis of HNO3 at 308 nm. The NO2* quantum yields from the HNO3 photolysis on aluminum surfaces are 0.80 ± 0.15 at 295 K and 0.92 ± 0.26 at 253 K, where errors quoted represent 2σ measurement uncertainty. The corresponding NO 2* quantum yield from the HNO3 photolysis on ice films is 0.60 ± 0.34 at 253 K. The 308 nm absorption cross sections of HNO3 on Al surfaces and on ice films have been directly measured. Absorption cross sections of HNO3 on Al surface at 308 nm are (4.19 ± 0.17) x 10-18 and (4.23 ± 0.45) x 10-18 cm2/molecule at 253 and at 295 K, whereas the corresponding absorption cross section of HNO3 on ice films is (1.21 ± 0.31) x 10-18 cm2/molecule at 253 K (errors quoted represent 2σ measurement uncertainty). Atmospheric implications of the results are discussed.
- Zhu, Chengzhu,Xiang, Bin,Chu, Liang T.,Zhu, Lei
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- Thermal behavior of copper(II) 4-nitroimidazolate
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The thermal behavior of copper(II) 4-nitroimidazolate (CuNI) under static and dynamic states are studied by means of high-pressure DSC (PDSC) and TG with the different heating rates and the combination technique of in situ thermolysis cell with rapid-scan
- Ji-Zhen,Xue-Zhong,Rong-Zu,Xiao-Dong,Feng-Qi,Hong-Xu
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- Absolute rate constant for the chemiluminescent reaction of atomic oxygen with nitric oxide
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The absolute rate constant for light emission from the NO-O reaction has been determined, as a function of wavelength, by using a standard brightness source, which has a surface of uniform brightness.The spectral distribution measured between 0.4 and 1.4 μm is in good agreement with those of the previous studies except for a little difference in the near infrared region.The influence from NO-O3 chemiluminescence is demonstrated for atomic oxygen production from O2 discharges.
- Sutoh, Masako,Morioka, Yumio,Nakamura, Masatoshi
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- Decomposition of Nitric Oxide over Y-Ba-Cu-O Mixed Oxide Catalysts
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Y-Ba-Cu-O mixed oxide catalysts supported on MgO were found to have higher catalytic activity for NO decomposition than a commercial Pt supported catalyst at 800 deg C.XPS analysis suggests that the decomposition of NO is facilitated by the redox cycle of Cu.
- Shimada, Hiromichi,Miyama, Susumu,Kuroda, Haruo
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- Thermal decomposition of N-substituted N-methylnitroamines
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Thermal decomposition of the N-methylnitroamines based on azoles in the liquid phase proceeds as a first-order reaction and is limited by the homolysis of the N-NO2 bond. The reaction rate is affected by the steric effect of the azole substituent. The activation parameters for the limiting stage of thermal decomposition were determined, and correlations between the logarithm of the rate constant, activation energy, and the steric constant E s of the substituent were elucidated.
- Stepanov,Kruglyakova
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- Cu, Fe and Mn oxides intercalated SiO2 pillared magadiite and ilerite catalysts for NO decomposition
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Synthesized magadiite and ilerite samples were pillared with SiO2 and then intercalated with Cu, Fe and Mn oxides to utilize for direct NO decomposition between 400 and 600 °C. Cu-SiO2-pil-ile and Cu-SiO2-pil-mag catalysts exhibited high NO decomposition activity compared to Fe and Mn oxide intercalated catalysts. Remarkably, Cu-SiO2-pil-ile offered 90 % NO conversion and 83 % N2 selectivity at 600 °C. Elemental analysis, XRD, FESEM, DR UV-vis, Raman spectroscopy, N2-adsorption, H2-TPR, O2-TPD and XPS were utilized to study physicochemical characteristics of the materials. The results from XRD and N2 adsorption demonstrated that the samples possessed different pore structures from SiO2-pillared silicates, due to different nature of metal oxides. The Cu-SiO2-pil-ile and Cu-SiO2-pil-mag samples possess a smaller number of Lewis and Br?nsted acid sites compared with Fe and Mn oxide intercalated samples. Presence of Cu2+/Cu+ and Fe3+/Fe2+, and synergism between redox centers are major reason for superior performance in NO decomposition. Therefore, the impact of redox properties and NO adsorption on the surface of the catalyst are significant.
- Katabathini, Narasimharao,El Maksod, Islam Hamdy Abd,Mokhtar, Mohamed
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- Preparation of g-C3N4 Nanosheets/CuO with Enhanced Catalytic Activity on the Thermal Decomposition of Ammonium Perchlorate
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The thermal oxidation etching assisted g-C3N4 nanosheets/CuO was prepared through a facile co-precipitation strategy. In this work, the structure, morphology, and composition of g-C3N4 (UCN, prepared by urea), g-C3N4 nanosheets (TCN, prepared by thermal oxidation etching of UCN), g-C3N4/CuO (UCN/CuO), g-C3N4 nanosheets/CuO (TCN/CuO) were characterized via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Furthermore, the catalytic effect of the obtained samples on the thermal decomposition of ammonium perchlorate (AP) was examined by thermal gravimetric analysis (TGA). As a result, in the case of 5 wt% TCN/CuO, the high decomposition temperature of AP decreased by 120.6 °C, which is much lower than that of UCN, TCN, CuO and UCN/CuO. In addition, the exothermic heat released from the decomposition of AP increased from 430.64 J g?1 to 2856.08 J g?1. This evident catalytic activity may be related to the synergistic effect of CuO and TCN. This work provides a novel strategy for the construction of composite catalyst for the thermal decomposition of AP, which is supposed to possess significant potential in the solid propellant field.
- Ma, Dan Na,Li, Xiao Meng,Wang, Xiao Qing,Luo, Yun Jun
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p. 982 - 988
(2021/02/26)
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- Investigation of kinetic parameters for ammonium perchlorate thermal decomposition in presence of gCN/CuO by TG-MS analysis and kinetic compensation correction
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The desire to develop a benign burn rate modifier for propellants has accentuated polymeric carbon nitride (gCN) as a potential candidate for the thermal decomposition of ammonium perchlorate (AP). Here, we have synthesized composites of leaf-shaped CuO and gCN via a facile sonochemical approach. From DSC analysis, the addition of gCNCuO1 reduced the decomposition temperature of AP by 59°C and increased the heat release by ~ 1.4 times that of pure AP. The kinetics of AP decomposition was well investigated via in-situ TG-MS technique. From evolved gas analysis evolution of NO, Cl, HCl, N2O/CO2, NO2 and Cl2 fragments were detected. The quantitative interpretation of kinetic parameters for AP decomposition was done using Coats-Redfern method and the normalization of E values were carried out by applying Kinetic Compensation Correction (KCC). After normalization, E values were decreased by 17 ?kJ/mol and 18 ?kJ/mol for the first and second stages respectively.
- Jos, Jisna,Mani, Gladiya,Mathew, Suresh,Radhakrishnan Nair, P.
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- Biochemical Characterization, Phytotoxic Effect and Antimicrobial Activity against Some Phytopathogens of New Gemifloxacin Schiff Base Metal Complexes
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String of Fe(III), Cu(II), Zn(II) and Zr(IV) complexes were synthesized with tetradentateamino Schiff base ligand derived by condensation of ethylene diamine with gemifloxacin. The novel Schiff base (4E,4′E)-4,4′-(ethane-1,2-diyldiazanylylidene)bis{7-[(4Z
- Mohamed, Amira A.,Elshafie, Hazem S.,Sadeek, Sadeek A.,Camele, Ippolito
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- Ultrafast synthesis of near-zero-cost S-doped Ni(OH)2on C3N5under ambient conditions with enhanced photocatalytic activity
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Planting highly efficient and low-cost Ni-based noble-metal-free active sites on semiconductors is of great significance in the field of photocatalysis. Herein, taking wide visible-light-responsive 2D C3N5 as a model semiconductor, an impressive near-zero-cost 2D S-doped nickel hydroxide (S-Ni(OH)2) is grown on C3N5 ultrafast within 30 min under ambient conditions by facile reaction between extremely low-cost Ni(NO3)2 and Na2S in aqueous solution. The fabricated 2D S-Ni(OH)2-C3N5 hybrid exhibits enhanced photocatalytic performance for both H2 production from water and NO removal for air purification. The H2 production rate on S-Ni(OH)2-C3N5 is ~7 times higher than that of Ni(OH)2-C3N5 and even slightly higher than that of Pt-C3N5, demonstrating its potential as a candidate for noble metal catalysts like Pt. In particular, an apparent quantum yield (AQY) value of 30.9% at 420 nm for H2 production is reached on 1.0 wt% S-Ni(OH)2-C3N5 due to quick internal charge transfer efficiency. In addition, ~42% of NO can be purified in a continuous flow reaction system. This work affords a cost-efficient strategy to steer the photocatalytic property of Ni-based catalysts.
- Chen, Hao,Han, Lixiao,Huang, Jinming,Peng, Cong,Wang, Shengyao,Yang, Yi,Zhang, Xiaohu
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p. 36166 - 36173
(2021/12/04)
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- Selective catalytic oxidation of ammonia over LaMAl11O19-: δ (M = Fe, Cu, Co, and Mn) hexaaluminates catalysts at high temperatures in the Claus process
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A method for the selective catalytic oxidation of ammonia at high temperature was innovatively proposed to substitute the traditional combustion method to remove the ammonia impurity in the Claus process. In the present work, transition metal (Fe, Cu Co, and Mn)-substituted La-hexaaluminate catalysts were synthesized and investigated for the selective catalytic oxidation of ammonia (NH3-SCO) at high temperature. It was observed that Cu-substituted catalysts could achieve the highest N2 yield at around 520 °C. It was confirmed that the conversion of NH3 was closely related to the reducibility of the prepared catalyst. In particular, it was observed that the molecular O2 could not be dissociatively adsorbed on the prepared catalyst surface. However, both lattice oxygen and gas-phase O2 could participate in NH3-SCO, with gas-phase O2 being the most favorable under the experimental conditions. It was evidenced that the NH3-SCO reaction over the prepared catalysts followed the i-SCR mechanism. Moreover, monodentate nitrates were the main reactive intermediates toward forming N2. Therefore, the development of high-temperature SCO technology and an efficient catalyst are beneficial for the sustainable development of the chemical industry.
- Hao, Zhengping,Jiang, Guoxia,Lin, Caihong,Sun, Yu,Wang, Zhuo,Wei, Zheng,Zhang, Fenglian,Zhang, Xin,Zhang, Yumeng
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p. 1477 - 1491
(2020/03/23)
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- Evaluation of Co/SSZ-13 Zeolite Catalysts Prepared by Solid-Phase Reaction for NO-SCR by Methane
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Co/SSZ-13 zeolites were prepared by heating the finely dispersed mixture of NH4-SSZ-13 and different cobalt salts up to 550 °C. Investigations by thermogravimetry – differential scanning calorimetry – mass spectrometry provided new insight into
- Ayari, Faouzi,Charrad, Rania,Hancsók, Jen?,Lónyi, Ferenc,Mhamdi, Mourad,Solt, Hanna E.,Trif, László,Valyon, József
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p. 1123 - 1134
(2020/12/03)
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- VOX supported on TiO2-Ce0.9Zr0.1O2 core-shell structure catalyst for NH3-SCR of NO
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In this experiment, a TiO2-Ce0.9Zr0.1O2 support with core-shell structure was successfully prepared by a precipitation method and VOX/TiO2-Ce0.9Zr0.1O2 catalyst was prepared by an impregnation method, and the catalyst was used to catalyze the NH3-SCR of NO. Based on the results of HRTEM, XRD, BET, H2-TPR, NH3-TPD, XPS, Py-IR, it was speculated that due to the interaction between TiO2 and Ce0.9Zr0.1O2, more oxygen vacancies and Ce3+ are generated, which are beneficial to the existence of low-valence V by electron transfer between high valence state V and Ce3+and increase the acidic sites on the catalyst surface. The catalytic activity (>97%) of the VOX/TiO2-Ce0.9Zr0.1O2 catalyst is superior to the current commercial catalyst (V2O5-WO3/TiO2) and has a higher N2 selectivity (>97.5%) at 40000 h-1 GHSV and 250-400 °C.
- Sun, Lvesheng,Cao, Shunxin,Huang, Yun,Zhang, Yiming,Xiao, Youhong,Dong, Guojun,Su, Yu
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p. 30340 - 30349
(2019/10/04)
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- Coordinative interaction between nitrogen oxides and iron-molybdenum POM Mo72Fe30
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The process of adsorption of nitrogen monoxide and dioxide by the giant Keplerate nanocluster Mo72Fe30 was studied in detail under ambient conditions and air/argon atmosphere. The obtained Raman and IR spectra showed that the coordination of NOx to the Mo72Fe30 leads to the formation of nitrate ions by sharing the bridged or terminal oxygen in FeO6 polyhedra with the adsorbed NO2 molecules. In accordance with elemental analysis and X-ray photoelectron spectroscopy, the composition of the produced complex was found to be [POM-(NO2)x]·(NO2)y (where x = 6, y = 14 ± 3). The carried out thermal analysis revealed the significant influence of NOx coordination in the release of water molecules and decomposition of the constitutional acetate ligands for Mo72Fe30. Furthermore, the performed measurements of the temperature dependency of the electron paramagnetic resonance spectra for the pure nanocluster and that treated with NO2 allowed us to draw up a conclusion about the delocalization of weak-bonded NO2 molecules in the pores of the Mo72Fe30 crystal at 25 °C. The opposite situation was observed under cryogenic temperatures. The localization of NO2 molecules occurs resulting in the distortion of FeO6 octahedra towards tetrahedral symmetry accompanied with the appearance of the signal at g-factor 4.3. The produced complex compound [POM-(NO2)x]·(NO2)y possesses sufficient NO2 capacity, water solubility and pH-dependant decomposition; these are important properties of a potential NOx donor, which can be hypothetically applied in biomedicine.
- Grzhegorzhevskii, Kirill V.,Tonkushina, Margarita O.,Fokin, Andrei V.,Belova, Ksenia G.,Ostroushko, Alexander A.
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p. 6984 - 6996
(2019/05/27)
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- Probing the Reaction Mechanisms Involved in the Decomposition of Solid 1,3,5-Trinitro-1,3,5-triazinane by Energetic Electrons
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The decomposition mechanisms of 1,3,5-trinitro-1,3,5-triazinane (RDX) have been explored over the past decades, but as of now, a complete picture on these pathways has not yet emerged, as evident from the discrepancies in proposed reaction mechanisms and the critical lack of products and intermediates observed experimentally. This study exploited a surface science machine to investigate the decomposition of solid-phase RDX by energetic electrons at a temperature of 5 K. The products formed during irradiation were monitored online and in situ via infrared and UV-vis spectroscopy, and products subliming in the temperature programmed desorption phase were probed with a reflectron time-of-flight mass spectrometer coupled with soft photoionization at 10.49 eV (ReTOF-MS-PI). Infrared spectroscopy revealed the formation of water (H2O), carbon dioxide (CO2), dinitrogen oxide (N2O), nitrogen monoxide (NO), formaldehyde (H2CO), nitrous acid (HONO), and nitrogen dioxide (NO2). ReTOF-MS-PI identified 38 cyclic and acyclic products arranged into, for example, dinitro, mononitro, mononitroso, nitro-nitroso, and amines species. Among these molecules, 21 products such as N-methylnitrous amide (CH4N2O), 1,3,5-triazinane (C3H9N3), and N-(aminomethyl)methanediamine (C2H9N3) were detected for the first time in laboratory experiments; mechanisms based on the gas phase and condensed phase calculations were exploited to rationalize the formation of the observed products. The present studies reveal a rich, unprecedented chemistry in the condensed phase decomposition of RDX, which is significantly more complex than the unimolecular gas phase decomposition of RDX, thus leading us closer to an understanding of the decomposition chemistry of nitramine-based explosives.
- Singh, Santosh K.,Zhu, Cheng,Vuppuluri, Vasant,Son, Steven F.,Kaiser, Ralf I.
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p. 9479 - 9497
(2019/11/11)
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- PROCESS FOR PREPARATION OF NITROGEN OXIDES AND NITRIC ACID FROM NITROUS OXIDE
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Described herein is an improved conversion of nitrous oxide (N2O) present as a by-product in a chemical process to NOx which can be further converted to a useful compound or material, such as nitric acid.
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Paragraph 000137; 000140
(2019/06/23)
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- Controlling a burn: Outer-sphere gating of hydroxylamine oxidation by a distal base in cytochrome P460
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Ammonia oxidizing bacteria (AOB) use the cytotoxic, energetic molecule hydroxylamine (NH2OH) as a source of reducing equivalents for cellular respiration. Despite disproportionation or violent decomposition being typical outcomes of reactions of NH2OH with iron, AOB and anammox heme P460 proteins including cytochrome (cyt) P460 and hydroxylamine oxidoreductase (HAO) effect controlled, stepwise oxidation of NH2OH to nitric oxide (NO). Curiously, a recently characterized cyt P460 variant from the AOB Nitrosomonas sp. AL212 is able to form all intermediates of cyt P460 catalysis, but is nevertheless incompetent for NH2OH oxidation. We now show via site-directed mutagenesis, activity assays, spectroscopy, and structural biology that this lack of activity is attributable to the absence of a critical basic glutamate residue in the distal pocket above the heme P460 cofactor. This substitution is the only distinguishing characteristic of a protein that is otherwise effectively structurally and spectroscopically identical to an active variant. This highlights and reinforces a fundamental principal of metalloenzymology: metallocofactor inner-sphere geometric and electronic structures are in many cases insufficient for imbuing reactivity; a precisely defined outer coordination sphere contributed by the polypeptide matrix can be the key differentiator between a metalloenzyme and an unreactive metalloprotein.
- Smith, Meghan A.,Majer, Sean H.,Vilbert, Avery C.,Lancaster, Kyle M.
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p. 3756 - 3764
(2019/04/01)
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- Improvement of low-temperature catalytic activity over hierarchical Fe-Beta catalysts for selective catalytic reduction of NOx with NH3
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Hierarchical Fe-Beta obtained by hydrothermal synthesis exhibited higher low-temperature NH3-SCR activity than conventional Fe-Beta. In order to identify the main factors leading to the difference in catalytic activity, we investigated the pore
- Zhu, Na,Lian, Zhihua,Zhang, Yan,Shan, Wenpo,He, Hong
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supporting information
p. 867 - 870
(2019/03/23)
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- Mid-infrared quantum cascade laser spectroscopy probing of the kinetics of an atmospherically significant radical reaction, CH 3O 2+ NO 2+ M → CH 3O 2NO 2+ M , in the gas phase
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Abstract: The kinetic parameters of an important atmospheric reaction, CH 3O 2+ NO 2+ M → CH 3O 2NO 2+ M , have been recorded by monitoring directly the changes in concentrations of methylperoxy radicals (CH 3O 2) in the gas phase employing a new mid-infrared quantum cascade laser (QCL)-based apparatus. CH 3O 2 radicals in our apparatus have been generated by pulsed UV laser (266?nm) photolysis of CH 3I in a gaseous mixture with oxygen. The absorption band corresponding to the mid-infrared O-O stretching fundamental of the peroxy radical, within a narrow spectral range, 1070–1120?cm - 1, has been recorded by tuning the wavelength of the QCL operated in CW mode. The kinetics of the aforementioned reaction of CH 3O 2 with NO 2 has been followed by analyzing the changes of the infrared (QCL) decay profile of CH 3O 2 at 9.1μm(1098.9cm-1) maintaining a pseudo first order reaction condition. We noticed that the rate constant of the reaction at 298?K varies in the range of (1.21–3.08) × 10 - 12cm3molecule-1s-1 for changing the total pressure in the range of 75–730?mbar. The absorption cross-section of CH 3O 2 at the probe wavelength (1098.9cm-1), has been estimated for the first time to be 8.3±0.4×10-20cm2. Graphical Abstract?: Kinetics measurement of an atmospherically important gas phase reaction, CH 3O 2+ NO 2+ M → CH 3O 2NO 2+ M , is studied using a newly developed apparatus based on pulsed UV laser photolysis time-resolved mid-infrared absorption spectroscopy. CH 3O 2 radicals are probed in the mid-infrared by a CW quantum cascade laser (QCL). [Figure not available: see fulltext.].
- Chattopadhyay, Aparajeo,Samanta, Monoj,Mondal, Koushik,Chakraborty, Tapas
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- Synthesis, structural exploration, spectral and combinatorial analysis of racemic-3-isobutyl-5-phenyl-5-(pyridin-4-yl)imida-zolidine-2,4-dione: Comparison between experimental and DFT calculations
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New racemic 3-isobutyl-5-phenyl-5-(pyridin-4-yl)imidazolidine-2,4-dione was synthesized, isolated, characterized spectrally, thermally and finally the structure was confirmed by X-ray diffraction studies. Both XRD and DFT/B3LYP/6-31G(d,p) optimized structures of the compound revealed the diketo monomer as favored tautomer isomer structure. The molecular geometry optimization parameters were compared with the experimental XRD results. The electronic spectrum which allocated basis of the TD-SCF result and the MO energy level diagram were compared with the experimental one. The electrophilic and nucleophilic receptors and acceptor functional groups with their interactions on the molecule surface was established by packing diagrams and then compared with Hirshfeld surface, electrostatic potential map and Mullikan population theoretical calculations. The experimental 1H NMR results, compared to the theoretical ACD-lab and NMR-db showed an excellent agreement. The desired organic compound revealed a high thermal stability in an open atmosphere.
- Benaka Prasad,Naveen,Ananda Kumar,Lokanath,Raghu,Daraghmeh, Iqab,Reddy, Kakarla Raghava,Warad, Ismail
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p. 215 - 226
(2018/09/12)
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- Mechanochemical fabrication and properties of CL-20/RDX nano co/mixed crystals
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By milling 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) together, a nano CL-20/RDX co/mixed crystal explosive with a mean particle size of 141.6?nm is prepared from the raw materials, and the co/mixed crystals are characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC) and thermal-infrared spectrometry online (DSC-IR) technology; furthermore, the impact, friction and thermal sensitivity of the samples are tested. The results show that after milling, the morphology of the co/mixed crystal explosive is near-spherical, and the particle size reveals a normal distribution. The milled sample showed the same molecular structure and surface elements as the raw materials, but the XRD test shows that CL-20/RDX has a new crystal phase and the Raman and IR spectra gave a supplementary confirmation for the existence of a cocrystal phase in the milled sample. The activation energy of the thermal decomposition of CL-20/RDX is 206.49 kJ mol?1 higher than that of raw RDX. DSC-IR analysis showed that the thermolysis of CL-20/RDX produces a large amount of CO2 and N2O and a small amount of H2O, NO2 and NO. The mechanical sensitivity of CL-20/RDX is very low. In impact sensitivity tests with a 5 kg hammer, the special height (H50) is 51.43 cm, which is higher than the values of 36.43 cm for raw CL-20 and 9.78 cm for raw RDX. In the friction sensitivity tests, the explosion probability (P) is 56%; however, the thermal sensitivity of CL-20/RDX is higher than that of the raw materials, with its 5 s burst point being only 243.51 °C.
- Song, Xiaolan,Wang, Yi,Zhao, Shanshan,Li, Fengsheng
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p. 34126 - 34135
(2018/10/17)
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- Cerium oxide based active catalyst for hydroxylammonium nitrate (HAN) fueled monopropellant thrusters
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Hydroxylammonium nitrate (HAN) is an energetic ionic liquid which is fast emerging as a promising environmentally friendly, high performing monopropellant for space propulsion application. The high performance due to the higher adiabatic temperature for HAN based compositions also poses challenges as high temperature tolerant catalysts have to be developed for its decomposition. A novel cobalt doped cerium oxide based catalyst has been prepared by the co-precipitation route and characterized by SEM/EDS, XRD, and XPS. The effectiveness of the catalyst in decomposing HAN has been tested using thermo-analytical techniques. An evolved gas analysis (EGA) to examine decomposition products and the possible reaction mechanism was also performed using the hyphenated DTA-TG-FTIR technique. Formation of an in situ Ce3+/Ce4+ ion couple in ceria during co-precipitation was found to be critical in deciding the reactivity of HAN decomposition over the catalyst. The activity of the catalyst was also examined in a batch reactor for its longevity. The prepared catalyst was found to be more versatile and durable than a hitherto reported alumina supported iridium catalyst in the present studies.
- Agnihotri, Ruchika,Oommen, Charlie
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p. 22293 - 22302
(2018/06/29)
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- Conversion of dilute nitrous oxide (N2O) in N2 and N2-O2 mixtures by plasma and plasma-catalytic processes
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A coaxial dielectric barrier discharge (DBD) reactor has been developed for plasma and plasma-catalytic conversion of dilute N2O in N2 and N2-O2 mixtures at both room and high temperature (300 °C). The effects of catalyst introduction, O2 content and inlet N2O concentration on N2O conversion and the mechanism involved in the conversion of N2O have been investigated. The results show that N2O in N2 could be effectively decomposed to N2 and O2 by plasma and plasma-catalytic processes at both room and high temperature, with much higher decomposition efficiency at 300 °C than at room temperature for the same discharge power. Under an N2-O2 atmosphere, however, N2O could be removed only at high temperature, producing not only N2 and O2 but also NO and NO2. Production and conversion of N2O occur simultaneously during the plasma and plasma-catalytic processing of N2O in a N2-O2 mixture, with production and conversion being the dominant processes at room and high temperature, respectively. N2O conversion increases with the increase of discharge power and decreases with the increase of O2 content. Increasing the inlet N2O concentration from 100 to 400 ppm decreases the conversion of N2O under an N2 atmosphere but increases that under an N2-O2 atmosphere. Concentrating N2O in the N2-O2 mixture could alleviate the negative influence of O2 by increasing the involvement of plasma reactive species (e.g., N2(A3Σu+) and O(1D)) in N2O conversion. Packing the discharge zone with a RuO2/Al2O3 catalyst significantly enhances the conversion of N2O and improves the selectivity of N2O decomposition under an N2-O2 atmosphere, revealing the synergy of plasma and catalyst in promoting N2O conversion, especially its decomposition to N2 and O2.
- Fan, Xing,Kang, Sijing,Li, Jian,Zhu, Tianle
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p. 26998 - 27007
(2018/08/07)
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- Ex Vivo Tracking of Endogenous CO with a Ruthenium(II) Complex
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A two-photon fluorescent probe based on a ruthenium(II) vinyl complex is capable of selectively detecting carbon monoxide in cells and ex vivo using mice with a subcutaneous air pouch as a model for inflammation. This probe combines highly selective and sensitive ex vivo detection of endogenous CO in a realistic model with facile, inexpensive synthesis, and displays many advantages over the widely used palladium-based systems.
- Torre, Cristina De La,Toscani, Anita,Marín-Hernández, Cristina,Robson, Jonathan A.,Terencio, María Carmen,White, Andrew J. P.,Alcaraz, María José,Wilton-Ely, James D. E. T.,Martínez-Má?ez, Ramón,Sancenón, Félix
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supporting information
p. 18484 - 18487
(2017/12/26)
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- Promotional effect of niobium substitution on the low-temperature activity of a WO3/CeZrOx monolithic catalyst for the selective catalytic reduction of NOx with NH3
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A series of Nb-substituted WO3/CeZrOx catalysts were prepared by the co-impregnation method and applied in the selective catalytic reduction of NOx with NH3 (NH3-SCR). NH3 oxidation, N2 sorption, XRD, Raman, UV-vis, XPS, H2-TPR, O2/NH3-TPD and in situ DRIFTS were performed to correlate the redox property and surface acidity to NH3-SCR performance of Nb-substituted catalysts. The catalyst with 5 wt% substitution amount of Nb2O5 presented excellent deNOx activity and N2 selectivity in a broad reaction temperature window of 190-434 °C at a gas space velocity of 30 000 h-1. The characterization results demonstrated that the partial substitution of WO3 by Nb2O5 not only led to strong redox properties arising from abundant surface active oxygen species, but also promoted the adsorption of NH3 and the redistribution of acid sites due to Nb-OH related to Br?nsted acid sites and NbO bonded to strong Lewis acid sites. The enhancement of surface active oxygen species and Br?nsted acid sites promoted the low-temperature (below 250 °C) deNOx activity. However, the preoxidation of NH3 at high temperatures slightly suppressed the NOx conversion of the catalyst with more strong Lewis acid sites at above 400 °C. Moreover, the catalyst also showed excellent sulfur tolerance and could be a promising candidate for practical applications in NOx abatement.
- Xu, Haidi,Lin, Qingjin,Wang, Yun,Lan, Li,Liu, Shuang,Lin, Chenlu,Wang, Qin,Wang, Jianli,Chen, Yaoiqng
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p. 47570 - 47582
(2017/10/19)
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- Kinetics of the Anaerobic Reaction of para-Substituted Phenols with Nitrogen Dioxide
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para-Substituted phenols in aqueous solution under anaerobic conditions readily react with nitrogen dioxide (NO2 ●) over a wide range of experimental conditions. The rate and rate law of the process were dependent on phenol concentration and solution pH. The kinetic order in phenol changed from one (low concentration) to zero (high concentration), a result attributable to total NO2 ● capture. Initial consumption rate (r0) of phenols versus pH plots showed parabolic behavior with a minimum rate at pH ca. 5. On the other hand, the maximum rate took place at high pH (pH>10) and involved the protonated phenols. The reaction rate of para-substituted phenols with NO2 ● correlated with the bond dissociation energy and with Hammett's parameter. Based on such results and also supported by analysis of products carried out by HPLC-MS/MS, our data conclusively show that, in spite of the fast acid–base interchanges of phenols and the interconversion of the different nitrogen oxides, the mechanisms of phenols nitration mediated by NO2 ● or HONO are clearly different.
- Reyes, Jael,Lissi, Eduardo,López-Alarcón, Camilo,Rubio, María A.
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- Atomic-Layer-Deposited ZnO on Carbon Black as High-Performance Catalysts for the Thermal Decomposition of Ammonium Perchlorate
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Hybrid materials with ZnO anchored on carbon black (CB) are fabricated by using the atomic-layer deposition (ALD) technique. The oxygen-containing functional groups on the surface of the CB act as the reactive sites to facilitate stable deposition of ZnO, and further create a unique hybrid structure with a C–O–Zn bond between CB and ZnO. The catalytic performance of the ZnO/CB hybrids for thermal decomposition of ammonium perchlorate (AP, NH4ClO4) is investigated, showing that two exothermic peaks are merged into one and the peak temperature decreases from 432 °C to 295 °C, even lower than that of ZnO (311 °C). The superior catalytic activity of ZnO/CB hybrids is attributed to the fast electron transfer from ZnO to CB and restricted electron recombination in the hybrids, which significantly benefits from the C–O–Zn bond fabricated by the ALD process. The present study provides a new insight into the catalytic mechanism of metal oxide/carbon hybrids, showing promise for catalyst and reaction accelerator applications.
- Wang, Jingfeng,Li, Yang,Wang, Huanhuan,Tian, Tian,Zhu, Shanxu,Zhou, Jia,Wu, Xiaohong,Qin, Wei
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p. 3154 - 3160
(2017/07/22)
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- Highly effective direct decomposition of nitric oxide by microwave catalysis over BaMeO3 (Me=Mn, Co, Fe) mixed oxides at low temperature under excess oxygen
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The direct catalytic decomposition of NO with high activity and N2 selectivity is a great challenge at low temperature under excess oxygen. Herein, we report the NO decomposition by microwave catalysis over BaMeO3 (Me=Mn, Co, Fe) mixed oxides for the first time at low temperature under excess oxygen, for which the BaCoO3 catalyst has an outstanding activity with a high NO conversion and N2 selectivity up to 99.8 % and 99.9 %, respectively, even at 250 °C. Comparatively, the best NO conversion is 93.7 % for BaMnO3 and only 64.1 % for BaFeO3 under microwave irradiation. H2 temperature-programmed reduction, O2 temperature-programmed desorption, and the microwave-absorbing properties of the mixed oxides were characterized to illustrate possible reasons that cause such clear differences in the catalytic performance. Importantly, the apparent activation energies for BaMnO3, BaCoO3, and BaFeO3 are as low as 33.4, 13.7, and 46.7 kJ mol-1, respectively, which suggests a significant microwave catalytic effect. NO limits: NO decomposition is reported by microwave catalysis over BaMeO3 (Me=Mn, Co, Fe) mixed oxides for the first time at low temperature under excess oxygen, for which the BaCoO3 catalyst has an outstanding activity with a high NO conversion and N2 selectivity up to 99.8 and 99.9 %, respectively, even at 250 °C.
- Xu, Wentao,Cai, Jinjun,Zhou, Jicheng,Ou, Yingpiao,Long, Wei,You, Zhimin,Luo, Yushang
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p. 417 - 425
(2016/02/05)
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- Investigations on HONO formation from photolysis of adsorbed HNO3 on quartz glass surfaces
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During the last few decades, nitrous acid (HONO) has attracted significant attention as a major source of the OH radical, the detergent of the atmosphere. However, the different daytime sources identified in the laboratory are still the subject of controversial discussion. In the present study, one of these postulated HONO sources, the heterogeneous photolysis of nitric acid (HNO3), was studied on quartz glass surfaces in a photo flow-reactor under atmospherically relevant conditions. In contrast to other investigations, a very low HNO3 photolysis frequency for HONO formation of J(HNO3 → HONO) = 2.4 × 10-7 s-1 (0° SZA, 50% r.h.) was determined. If these results can be translated to atmospheric surfaces, HNO3 photolysis cannot explain the significant HONO levels in the daytime atmosphere. In addition, it is demonstrated that even the small measured yields of HONO did not result from the direct photolysis of HNO3 but rather from the consecutive heterogeneous conversion of the primary photolysis product NO2 on the humid surfaces. The secondary NO2 conversion was not photo-enhanced on pure quartz glass surfaces in good agreement with former studies. A photolysis frequency for the primary reaction product NO2 of J(HNO3 → NO2) = 1.1 × 10-6 s-1 has been calculated (0° SZA, 50% r.h.), which indicates that renoxification by photolysis of adsorbed HNO3 on non-reactive surfaces is also a minor process in the atmosphere.
- Laufs, Sebastian,Kleffmann, J?rg
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p. 9616 - 9625
(2016/04/19)
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- Investigation of the thermal decomposition and stability of energetic 1,2,4-triazole derivatives using a UV laser based pulsed photoacoustic technique
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This paper is in continuation of our previous report which was based on a 532 nm wavelength pulsed photoacoustic (PA) technique with nitro rich energetic materials named 1-(4-methyl-3,5-dinitrophenyl)-1H-1,2,4-triazole (p-Me-DNPT), 1-(4-methoxy-3,5-dinitrophenyl)-1H-1,2,4-triazole (p-OMe-DNPT), and 2,6-dinitro-4-(1H-1,2,4-triazol-1-yl) aniline (p-NH2-DNPT) in the 30-350 °C temperature range. In the present work, the PA fingerprint spectra, thermal stability and efficiency of these compounds as rocket fuel have been evaluated using the fourth harmonic i.e. 266 nm wavelength of 7 ns pulse duration and 10 Hz repetition rate as an excitation source. The entire study is based on the photodissociation process due to the π? ← n electronic transition in NO2 molecules which is initiated inside the PA cell. The result obtained from the PA technique and thermogravimetric-differential thermal analysis (TG-DTA) data confirm the multistep decomposition mechanism. The study also provides the stable thermal quality factor "Q" which is linked to the stability of the compound.
- Rao,Chaudhary
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p. 47646 - 47654
(2016/06/09)
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- Synthesis and characterization of a new energetic salt 1H-pyrazole-1-carboxamidine dinitramide and its thermal properties
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The new energetic compound 1H-pyrazole-1-carboxamidine dinitramide (PACADN) was synthesized by the reaction of silver dinitramide with 1H-pyrazole-1-carboxamidine hydrochloride. Its structure was confirmed by single-crystal X-ray diffraction, elemental analysis and Fourier transform infrared, ultraviolet–visible and nuclear magnetic resonance spectroscopy analyses. PACADN crystallizes in the orthorhombic space group Pnna. The thermal decomposition was studied with differential scanning calorimetry, thermogravimetry analysis and thermogravimetric tandem infrared spectrum. The results indicated that PACADN exhibits good resistance to thermal decomposition up to 433?K and has 90.24?% mass loss between 433 and 523?K by undergoing exothermic decomposition. The kinetic parameters of the thermal decomposition of PACADN were also obtained from the derivative thermogravimetry analysis data using Kissinger’s method, with Ea?=?143.2?kJ?mol?1. Moreover, the detonation velocity and detonation pressure of PACADN were calculated as 7.2?km?s?1 and 21?GPa by applying the Kamlet–Jacobs (as follows).(Formula presented.).
- Zhao, Jun,Jin, Bo,Peng, Rufang,Liu, Qiangqiang,Tan, Bisheng,Chu, Shijin
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p. 1431 - 1439
(2016/06/01)
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- Biosynthesis of ZnO nanoparticles using rambutan (Nephelium lappaceumL.) peel extract and their photocatalytic activity on methyl orange dye
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In the present study, describes the synthesis of ZnO nanoparticles from rambutan (Nephelium lappaceumL.) peel extract via bio synthesis method and developed a new low cost technology to prepare ZnO nanoparticles. During the synthesis, fruit peel extract act as a natural ligation agent. The successfully prepared product was analyzed with some standard characterization studies like X-Ray Diffraction (XRD), UV-VIS Diffuse reflectance spectra (UV–Vis DRS), Field Emission Scanning Electron Microscope (FESEM), High resolution transmittance electron microscope (HR-TEM), N2 adsorption-desorption isotherm and UV–Vis absorption Spectroscopy. The photocatalytic activity of ZnO nanoparticles was evaluated by photodegradation of methyl orange (MO) dye under UV light and the result depicts around 83.99% decolorisation efficiency at 120?min of illumination. In addition with photodecolorisation, mineralization was also achieved. The mineralization has been confirmed by measuring Chemical Oxygen Demand (COD) values.
- Karnan, Thenmozhi,Selvakumar, Stanly Arul Samuel
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p. 358 - 365
(2016/07/20)
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- Coupling catalytic hydrolysis and oxidation on metal-modified activated carbon for HCN removal
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A method of coupling catalytic hydrolysis and oxidation for HCN removal by metal-modified activated carbon (denoted as AC-M) was studied using a dynamic method in a fixed bed reactor. The results showed that impregnation of metal oxides on the activated carbon significantly enhanced the removal capacity for HCN. Among the different types of metal-modified catalysts, AC-Cu exhibited the highest catalytic activity. The AC-Cu catalyst showed >96% conversion of HCN at 200-350 °C. The selectivity of N2 in the conversion of HCN reached 48.8% at 300 °C. Oxygen concentration, relative humidity and calcination temperature can greatly influence the catalytic activity. In particular, the reaction temperature was determined to be a crucial factor. The detailed characterization of the catalyst was performed using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), and temperature programmed desorption (TPD). The Cu 2p XPS spectra and XRD patterns indicated that CuO was formed as an active species for the catalytic removal of HCN. We concluded that AC-Cu could be used as a catalyst for the removal of HCN by coupling catalytic hydrolysis and oxidation.
- Wang, Xueqian,Jing, Xuli,Wang, Fei,Ma, Yixing,Cheng, Jinhuan,Wang, Langlang,Xu, Ke,Cheng, Chen,Ning, Ping
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p. 57108 - 57116
(2016/07/06)
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- Structure-performance relationships of MnO2 nanocatalyst for the low-temperature SCR removal of NOX under ammonia
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To investigate the corresponding relationship between catalytic efficiency and structure, MnO2 nanomaterials (nanospheres, nanosheets, nanorods) have been prepared successfully, and were thoroughly characterized by SEM and TEM. Furthermore, the selective catalytic reduction (SCR) performance of NOX under ammonia was used as an indicative reaction. Among the MnO2 nanomaterials with different morphologies, it was found that their SCR activities showed an interesting variation tendency: nanospheres > nanosheets > nanorods of MnO2. The NO conversion ratio of the MnO2 nanospheres could reach 100% from 200 to 350 °C. Moreover, in order to study the probable mechanism for the best removal efficiency of the nanospheres, XRD, H2-TPR, NH3-TPD, BET, XPS and in situ DRIFTS were performed in detail. It is found that surface chemisorbed oxygen, specific surface area, reducibility and acid sites have great influence on the NO removal efficiency in the SCR reaction. In addition, how several process parameters affect the NOX removal efficiency was carried out, such as time, H2O and SO2.
- Li, Yi,Li, Yanping,Wan, Yuan,Zhan, Sihui,Guan, Qingxin,Tian, Yang
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p. 54926 - 54937
(2016/07/06)
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- Oxygen vacancies on nanosized ceria govern the NOX storage capacity of NSR catalysts
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Pt/BaO/CeO2 catalysts derived from CeO2 nanomaterials with shapes of rods, cubes, and particles were investigated for NOx storage/reduction. Catalytic tests were performed in a transient flow reactor system. A series of characterization techniques including XRD, TEM, XPS, EXAFS, NOx-TPD, H2-TPR and in situ DRIFTS were conducted to investigate the electrical, chemical, and structural properties. The NOx storage-reduction performance ranked by the CeO2 support was nanorods > nanoparticles > nanocubes. Amazingly, the CeO2-nanorod based NSR catalyst possessed a superior NOx storage capacity (NSC) of 913.8 μmol NOx gcat-1 at 350 °C in the absence of H2O and CO2, which almost reached the theoretical value. Even under harsh lean-rich cycling conditions (90 s vs. 6 s) and a high GHSV of 360000 h-1, the nanorod-based catalyst also showed the best reduction efficiency, affording ~ 99% NOx conversion levels from 200 °C to 400 °C under the conditions without H2O and CO2. The morphology of ceria has significant influences on the selectivity of ammonia, and on the H2O and CO2 tolerance during the NSR process. For the first time, a close linear correlation was drawn between the NOx storage capacity and the amount of oxygen vacancies of NSR catalysts. Over the NSR catalysts, oxygen vacancies play a crucial role in anchoring Pt. Meanwhile, H2-TPR results showed that the number of active surface oxygen species trapped in oxygen vacancies was closely related to the NSC value. This suggests that the oxygen vacancies on the NSR surface govern the NOx storage capacity by creating efficient sites or channels for the formation of nitrate and its further transformation to Ba-based storage sites. These findings may be fundamental for designing ceria-based NSR catalysts with better performance.
- Zhang, Yan,Yu, Yunbo,He, Hong
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p. 3950 - 3962
(2016/06/13)
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- Ammonia synthesis and by-product formation from H2O, H2 and N2 by dielectric barrier discharge combined with an Ru/Al2O3 catalyst
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NH3 synthesis from H2O + N2, H2 + N2 or H2O + H2 + N2 by dielectric barrier discharge combined with an Ru/Al2O3 catalyst is studied at atmospheric pressure and room temperature. Additionally, the effects of reaction gas composition, energy density, and discharge frequency on NH3 yield and by-product formation are investigated. The results show that NH3 can be formed from reaction gases consisting of H2O and N2. The NH3 yield of the reaction gas containing H2 is much higher than that of the reaction gas consisting of H2O and N2. The presence of H2O has a promotion effect on NH3 synthesis from H2 and N2, especially for reaction gases with an H2 content less than 10%. The NH3 yield first increases and then decreases with an increase in the energy density. The maximum yield of 680 mg kW?1 h?1 occurs at the energy density of 1400 J L?1 and in the reaction gas of 0.14% H2O, 40% H2 and N2. The discharge frequency has a great effect on the NH3 yield, and maximum NH3 yield is obtained at the frequency of 13 kHz. Besides NH3, some by-products, such as N2O and NO2, are also formed with reaction gases containing H2O. However, their formation can be suppressed in the presence of H2, which is attributed to the reduction effect of H2 on the by-products.
- Xie, Deyuan,Sun, Ye,Zhu, Tianle,Fan, Xing,Hong, Xiaowei,Yang, Wenhao
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p. 105338 - 105346
(2016/11/17)
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- Selective catalytic oxidation of ammonia over MnO: X-TiO2 mixed oxides
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The selective catalytic oxidation of ammonia to nitrogen (NH3-SCO) was investigated over MnOx-TiO2. The physicochemical properties of MnOx-TiO2 were characterized by XRD, O2-TPD, NH3/
- Song, Dongdong,Shao, Xunzhe,Yuan, Menglong,Wang, Li,Zhan, Wangcheng,Guo, Yanglong,Guo, Yun,Lu, Guanzhong
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p. 88117 - 88125
(2016/09/28)
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- Potential synergic effect between MOR and BEA zeolites in NOx SCR with methane: A dual bed design approach
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The selective catalytic reduction of NOx with methane (NOx CH4-SCR) under lean conditions was investigated with catalysts based on two different zeolite structures (MOR and BEA) containing Pd and Ce. The catalytic performance for NO oxidation to NO2 reaction, considered an important first key step in the NOx CH4-SCR mechanism, was also assessed. Pd(0.3)Ce(2)-HBEA was found to be very active for NO oxidation but exhibits poor activity for NOx CH4-SCR. Conversely, Pd(0.3)Ce(2)-HMOR presents modest activity for NO oxidation, compared to Pd(0.3)Ce(2)-HBEA, but exhibits mild activity for NOx CH4-SCR reaction. Characterisation by H2-TPR, DRS UV-vis, TEM/EDS and FTIR-CO allowed the identification of palladium stabilised as Pd2+ ions in exchange positions in both monometallic and bimetallic MOR based catalysts, whereas, in BEA catalysts, it is presented as PdO clusters. Cerium is stabilised in Pd(0.3)Ce(2)-HMOR as small CeO2 particles, whereas, in Pd(0.3)Ce(2)-HBEA, it is present as large clusters. Catalysts were also tested in dual bed configuration, in which Pd(0.3)Ce(2)-HBEA was placed as first layer and Pd(0.3)Ce(2)-HMOR as second layer in the catalytic bed. The catalytic performance was significantly improved (higher NOx conversion into N2 and higher CH4 selectivity to SCR reaction), when compared to the catalytic performance of each catalyst individually, suggesting the existence of a synergic effect. This synergy is explained by the complementary roles that each catalyst play in HC-SCR mechanism.
- Mendes, Acácio Nobre,Matynia, Alexis,Toullec, Alain,Capela, Sandra,Ribeiro, M.Filipa,Henriques, Carlos,Da Costa, Patrick
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p. 246 - 253
(2015/10/12)
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- High-yield microwave synthesis of layered Y2(OH)5NO3·xH2O materials
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A novel, facile, and versatile microwave-assisted method of high-yield synthesis of layered rare earth hydroxo compounds (LRHs) is proposed. Layered yttrium hydroxonitrates synthesized by the microwave-assisted technique crystallize in the form of thin hexagonal plates aggregated into spheroidal particles. Depending on the conditions of microwave-assisted hydrothermal synthesis, the formation of several phases differing in interplanar spacing along the [00l] direction is possible. The materials obtained are shown to possess good anion-exchange properties. This work provides a route to large-scale synthesis of LRH-based advanced materials. This journal is
- Yapryntsev,Baranchikov,Skogareva,Goldt,Stolyarov,Ivanova,Kozik,Ivanov
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p. 2667 - 2674
(2015/03/30)
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- An anion-exchange strategy for 3D hierarchical (BiO)2CO3/amorphous Bi2S3 heterostructures with increased solar absorption and enhanced visible light photocatalysis
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Bismuth-based nanostructured materials have attracted great interest in a wide range of applications. In the present work, 3D (BiO)2CO3 hierarchical microspheres self-assembled by nanosheets were synthesized by a simple hydrothermal method. By using a facile anion-exchange strategy, (BiO)2CO3/amorphous Bi2S3 heterostructures were constructed through the controlled chemical reaction between (BiO)2CO3 microspheres and Na2S in an aqueous solution. The as-prepared samples were systematically characterized by XRD, SEM-EDX, TEM, FT-IR, XPS, UV-vis DRS and PL techniques. The heterostructured samples were applied for photocatalytic removal of ppb-level NO in air under visible light irradiation. The pure (BiO)2CO3 hierarchical microspheres exhibited decent visible light photocatalytic activity due to the surface reflecting and scattering effect. Amorphous Bi2S3 showed no photocatalytic activity due to narrow band gap. By hybridization of (BiO)2CO3 microspheres with amorphous Bi2S3 on the surface, 3D hierarchical (BiO)2CO3/amorphous Bi2S3 heterostructures were constructed, which demonstrated increased solar light absorption and highly enhanced visible photocatalytic activity and stability. The enhanced performance can be directly ascribed to the increased visible light utilization, promoted charge separation arising from the well-matched band structure and accelerated reactants transfer resulting from special 3D hierarchical structure. The present work opens a new avenue for modification of wide-band gap semiconductor with amorphous components, which could reduce the further thermal treatment and production cost.
- Dong, Fan,Feng, Xin,Zhang, Yuxin,Gao, Chunfeng,Wu, Zhongbiao
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p. 11714 - 11723
(2015/02/19)
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- Improved low temperature NH3-SCR performance of FeMnTiOx mixed oxide with CTAB-assisted synthesis
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FeMnTiOx mixed oxide is prepared by the CTAB-assisted co-precipitation method, and the transformation of anatase into rutile is inhibited by CTAB to some extent. The catalyst obtained in the present work shows nearly 100% NO conversion at 100-350 °C, more than 80% N2 selectivity at 75-200 °C, and excellent H2O durability for the selective catalytic reduction of NO by NH3 with a space velocity of 30000 mL g-1 h-1. This journal is
- Wu, Shiguo,Yao, Xiaojiang,Zhang, Lei,Cao, Yuan,Zou, Weixin,Li, Lulu,Ma, Kaili,Tang, Changjin,Gao, Fei,Dong, Lin
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supporting information
p. 3470 - 3473
(2015/03/30)
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- Influence of hexagonal boron nitride on the selective catalytic reduction of NO with NH3 over CuOX/TiO2
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Hexagonal boron nitride (hBN) was used as a CuOX/TiO2 catalyst carrier and its effect on NO reduction with NH3 was studied. After hBN was treated with concentrated HNO3, CuOX/TiO2 nanoparticles were dispersed well onto hBN, and the addition of hBN was found to promote NO oxidation, while at the same time suppress NH3 oxidation to NO, and thus promoted the selective catalytic reduction of NO at reaction temperatures between 150 to 350°C, and a high de-NOX efficiency of 90.6% was achieved at 275°C. Our study indicates that hBN is a promising catalyst promoter and carrier with excellent stability compared to carbonaceous materials.
- Zhou, Dongsheng,Ren, Zhiyuan,Li, Bo,Ma, Zhaoxia,Zhang, Xiaobin,Yang, Hangsheng
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p. 31708 - 31715
(2015/04/22)
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- TeO2 Nanoparticle Loaded Graphitic Carbon Nitride Hybrids: Their Preparation and Catalytic Activities in the Thermal Decomposition of Ammonium Perchlorate
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TeO2 nanoparticle-loaded graphitic carbon nitride hybrids (TeO2NPs/g-C3N4) were successfully prepared by a calcination strategy. Various characterization and detection techniques were used to analyze its structu
- Li, Qi,He, Yi,Peng, Rufang
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p. 4062 - 4067
(2015/09/01)
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- Inhibitory effect of SO2 on side reactions of NH3-SCR over olivine
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Olivine catalysts prepared by calcination achieved high N2 selectivity and good NH3-SCR activity at 150-450 °C. The existence of SO2 significantly inhibited the formation of NO and N2O in the NH3-SCR reaction at the temperature range of 325-450 °C. This is mainly because of the reductive properties of SO2 that could restrain the over-oxidization of NH3. Therefore, both the NOx conversion and N2 selectivity were improved at high temperatures. Accordingly, the presence of SO2 shifted the optimal temperature window of the olivine catalyst by about 75 °C towards high temperature. Both the Langmuir-Hinshelwood mechanism and the Eley-Rideal mechanism contributed to the SCR reaction over the olivine catalyst. Temperature-programmed desorption experiments show that excess ammonium sulfate formed in the presence of SO2 suppressed the reaction of adsorbed NOx species with adsorbed NH3 species at low temperatures. Lots of activated NH3 species (-NH2) were formed by the decomposition of ammonium sulfate at high temperatures, promoting the reaction of adsorbed NH3 species (-NH2) with both adsorbed NOx and gaseous NOx. Preliminary results suggest that olivine is a potential catalyst for treating sulfur-containing exhausts.
- Shi, Yun,Tan, Shan,Li, Sujing,Zhao, Jingkai,Xia, Yinfeng,Lv, Bihong,Li, Wei
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p. 3613 - 3623
(2015/06/30)
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- Selective oxidation of bacterial cellulose by NO2-HNO 3
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Bacterial cellulose (BC) needs to be selectively oxidized by different oxidants such as TEMPO-NaClO-NaBr and NaIO4 in order to control its degradability in vivo. However, both of these two oxidants are difficult to remove and the oxidation process is often accompanied by undesirable degradation of the material. In this work, a highly selective and efficient method for producing oxidized bacterial cellulose (OBC) has been developed in the reaction with NO2 in HNO3 solution. Systematic characterization of the structure and property of the resulting OBCs demonstrated that the oxidation process not only avoided the secondary reaction but also significantly enhanced its mechanical properties, controllability of biodegradability and protein absorbability. Nuclear magnetic resonance (NMR) testing and Fourier transform infrared spectroscopy (FTIR) proved that the selective oxidation of BC took place only at C6 where primary alcohol groups were quickly oxidized to carboxyl groups, with a maximum oxidation degree achieved up to 32.54% after 40 h. The oxidation process not only retained the crystal structure of BC, but slightly increased its degree of crystallinity, thus contributing to the improvement of its strength and toughness. At the same time, OBC manifested more controllable degradability and higher protein adsorption than the original BC as a function of the oxidation time.
- Cui, Qiuyan,Zheng, Yudong,Lin, Qinghua,Song, Wenhui,Qiao, Kun,Liu, Shumin
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p. 1630 - 1639
(2014/01/06)
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- Mechanism of nitric acid reduction and kinetic modelling
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In France, the recycling of nuclear waste fuels involves the use of hot concentrated nitric acid. The understanding and prediction of the behaviour of the structural materials (mainly austenitic stainless steels) requires the determination and modelling of the nitric acid reduction process. Nitric acid is indirectly reduced by an autocatalytic mechanism depending on the cathodic overpotential and acid concentration. This mechanism has been widely studied. All the authors agree on its autocatalytic nature, characterized by the predominant role of the reduction products. It is also generally admitted that neither nitric acid nor the nitrate ion is the electroactive species. However, the nature of the electroactive species, the place where the catalytic species regenerates and the thermodynamic and kinetic behaviour of the reaction intermediates remain uncertain. The aim of this study was to clarify some of these uncertainties by performing an electrochemical investigation of the reduction of 4 M nitric acid at 40 °C at an inert electrode (platinum or gold). An inert electrode was chosen as the working electrode in a first step to avoid its oxidation and focus the research on the reduction mechanism. This experimental work enabled us to suggest a coherent sequence of electrochemical and chemical reactions. Kinetic modelling of this sequence was then carried out for a gold rotating disk electrode. A thermodynamic study at 25 °C allowed the composition of the liquid and gaseous phases of nitric acid solutions in the concentration range 0.5-22 M to be evaluated. The kinetics of the reduction of 4 M nitric acid was investigated by cyclic voltammetry and chronoamperometry at an inert electrode at 40 °C. The coupling of chronoamperometry and FTIR spectroscopy in the gaseous phase led to the identification of the gaseous reduction products as a function of the cathodic overpotential. The results showed that the reduction process is autocatalytic for potentials between 0.6 and 1.15 V/NHE. The electroactive species may be regenerated at the surface of the electrode for lower potentials, otherwise this regeneration process occurs in solution by a homogeneous chemical reaction. When the potential is less than 0.6 V/NHE, the fast reduction of nitrogen oxide may lead to rupture of the autocatalytic cycle. The kinetics of the reduction of 4 M nitric acid has been investigated at an inert electrode at 40 °C. The results show that the reduction process is autocatalytic for potentials between 0.6 and 1.15 V/NHE. HNO2 is the electroactive species and is regenerated at or near the electrode surface by a chemical reaction between HNO3 and NO(ads). Kinetic modelling of this mechanism was carried out.
- Sicsic, David,Balbaud-Célérier, Fanny,Tribollet, Bernard
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p. 6174 - 6184
(2015/02/19)
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- Solution combustion synthesis of Ti0.75Ce0.15Cu0.05W0.05O2-δ for low temperature selective catalytic reduction of NO
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A Ti-Ce-Cu-W catalyst prepared by solution combustion synthesis (SCS) showed high low temperature activity for selective catalytic reduction (SCR) of NO with ammonia. Different fuels and different fuel/oxidant (F/O) ratios were introduced to investigate the optimum synthesis conditions for the Ti0.75Ce0.15Cu0.05W0.05O2-δ catalyst. The results showed that samples using citric acid and glycine as a fuel showed good low temperature catalytic activity and the catalytic activity could be improved through increasing the F/O ratio. The sample with a F/O ratio of 1.5 obtained around 70% NO conversion at a temperature of 150°C.
- Chen, Ting,Lin, He,Cao, Qunhai,Huang, Zhen
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p. 63909 - 63916
(2015/02/19)
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- In situ gas bubble-assisted one-step synthesis of polymorphic Co 3O4 nanostructures with improved electrochemical performance for lithium ion batteries
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A novel and versatile gas bubble-assisted self-assembly technique was developed for the first-time preparation of Co3O4 nanobowl arrays by the rapid thermal decomposition of Co(NO3) 2×6H2O on a flat substrate. The morphological modulation from novel nanobowl arrays, to nanotube arrays, to nanorods, and even to microspheres can be realized by only tuning decomposition temperature from 150 C to 700 C. The in situ generated (O2, H2O, NO 2) bubbles guided the growth of Co3O4 nuclei, resulting in the final morphology of Co3O4 nanostructures. The Co3O4 nanostructures were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption isotherms. Analysis of electrochemical properties revealed that Co 3O4 nanobowl and nanotube arrays obtained at low temperatures displayed significant enhancement of electrochemical activity because of low crystallization, small grain size, high specific surface area, and hierarchically porous structure. This simple process was applicable to large-scale production and may be extended to other materials. The porous/hollow structure and high specific surface area of the as-obtained Co 3O4 nanobowl and nanotube arrays can enable their potential use in catalysis, chemical sensing, luminescence, energy storage, controlled release, and cellular applications.
- Tong, Guoxiu,Liu, Yun,Guan, Jianguo
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p. 167 - 174
(2014/04/03)
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- In situ decoration of plasmonic Ag nanocrystals on the surface of (BiO)2CO3 hierarchical microspheres for enhanced visible light photocatalysis
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Novel plasmonic 0D Ag nanocrystal decorated 3D (BiO)2CO 3 hierarchical microspheres were fabricated with a one-pot hydrothermal method. The as-prepared samples were systematically characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, photoluminescence spectra, ns-level time-resolved fluorescence spectra, photocurrent generation and EIS measurement. The results indicated that the 0D Ag nanoparticles were deposited on the surface of 3D (BiO)2CO3 hierarchical microspheres. The deposited Ag nanoparticles were reduced from Ag+ by the citrate ions from bismuth citrate. The photocatalytic activity of the as-prepared samples was evaluated towards the degradation of NO at ppb-level under visible light irradiation. The intermediate NO2 was monitored on-line during the photocatalytic reaction. The pure (BiO)2CO 3 microspheres exhibited decent visible light photocatalytic activity because of the surface scattering and reflecting (SSR effect) resulting from the special 3D hierarchical architecture. The Ag-decorated (BiO) 2CO3 microspheres (Ag/BOC) exhibited greatly enhanced photocatalytic activity, photocurrent generation and promoted NO2 oxidation compared to the pure (BiO)2CO3 microspheres. The enhanced photocatalytic activity and photocurrent generation of Ag/BOC was ascribed to the cooperative contribution of the surface plasmon resonance (SPR effect), efficient separation of electron-hole pairs and prolonged lifetime of charge carriers induced by Ag nanoparticles. The photocatalytic performance of Ag/BOC was dependent on the content of Ag loading. When the amount of Ag is controlled at 5%, the highest photocatalytic performance can be achieved. Further increasing the Ag loading content promotes aggregation of the Ag particles and transforms the uniform microspheres into non-uniform microspheres, which is not beneficial to improving the activity. Importantly, the as-prepared Ag/BOC composites exhibited high photochemical stability after multiple reaction runs. The concepts of enhancing the activity through the SSR and SPR effects provide a new avenue for the development of efficient noble metal/bismuth-based plasmonic photocatalysts with attractive nano/micro architectures for efficient visible light photocatalytic activity.
- Dong, Fan,Li, Qiuyan,Zhou, Ying,Sun, Yanjun,Zhang, Haidong,Wu, Zhongbiao
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p. 9468 - 9480
(2014/06/23)
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- A novel mechanism for poisoning of metal oxide SCR catalysts: Base-acid explanation correlated with redox properties
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A novel mechanism is proposed for the poisoning effect of acid gases and N2O formation on SCR catalysts involving base-acid properties correlated with redox ability of M-O or M-OH (M = Ce or V) of metal oxides and the strength of their basicity responsible for resistance to HCl and SO 2 at medium and low temperatures. This journal is the Partner Organisations 2014.
- Chang, Huazhen,Li, Junhua,Su, Wenkang,Shao, Yuankai,Hao, Jiming
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p. 10031 - 10034
(2014/08/18)
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