10024-97-2

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• Kinetics and mechanism of the iron phthalocyanine catalyzed reduction of nitrite by dithionite and sulfoxylate in aqueous solution
• The reactions of sodium nitrite with sodium dithionite and sulfoxylate ion were studied in the presence of iron(III) tetrasulfophthalocyanine, Fe III(TSPc)3-, in aqueous alkaline solution. Kinetic parameters for the different reaction steps in the catalytic reduction by dithionite were determined. The final product of the reaction was found to be nitrous oxide. Contrary to this, the product of the catalytic reduction of nitrite by sulfoxylate was found to be ammonia. The striking difference in the reaction products is accounted for in terms of different structures of the intermediate complexes formed during the reduction by dithionite and sulfoxylate, in which nitrite is suggested to coordinate to the iron complex via nitrogen and oxygen, respectively. Sulfoxylate is shown to be a convenient reductant for the synthesis of the highly reduced iron phthalocyanine species FeI(TSPc?)6- in aqueous solution. The kinetics of the reduction of FeI(TSPc)5- to Fe I(TSPc?)6-, as well as the oxidation of the latter species by nitrite, was studied in detail.
• Kudrik, Evgeny V.,Makarov, Sergei V.,Zahl, Achim,Van Eldik, Rudi

• p. 6470 - 6475

  (2005)
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• Reaction between Nitrogen Monoxide and Carbon Monoxide over Superconducting Bi-Sr-Ca-Cu and Related Mixed Oxides
• Bi-Sr-Ca-Cu-O mixed oxides having Bi2Sr2CaCu2Oy structure were very active for reactions between nitrogen monoxide and carbon monoxide among the prepared catalysts having perovskite and related structures.
• Mizuno, Noritaka,Toyama, Hisashi,Tanaka, Mika,Yamato, Mika,Misono, Makoto

• p. 1383 - 1385

  (1991)
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• Investigation of N2O production from 266 and 532 nm laser flash photolysis of O3/N2/O2 mixtures
• Tunable diode laser absorption spectroscopy has been employed to measure the amount of N2O produced from laser flash photolysis of O3/N2/O2 mixtures at 266 and 532 nm. In the 532 nm photolysis experiments very little N2O is observed, thus allowing an upper limit yield of 7 × 10-8 to be established for the process O3? + N2 → N2O + O2, where O3? is nascent O3 that is newly formed via O(3PJ) + O2 recombination (with vibrational excitation near the dissociation energy of O3). The measured upper limit yield is a factor of ～600 smaller than a previous literature value and is approximately a factor of 10 below the threshold for atmospheric importance. In the 266 nm photolysis experiments, significant N2O production is observed and the N2O quantum yield is found to increase linearly with pressure over the range 100-900 Torr in air bath gas. The source of N2O in the 266 nm photolysis experiments is believed to be the addition reaction O(1D2) + N2 + M k6 → N2O + M, although reaction of (very short-lived) electronically excited O3 with N2 cannot be ruled out by the available data. Assuming that all observed N2O comes from the O(1D2) + N2 + M reaction, the following expression describes the temperature dependence of k6 (in its third-order low-pressure limit) that is consistent with the N2O yield data: k6 = (2.8 ± 0.1) × 10-36(T/300)-(0.88±0.36) cm6 molecule-2s-1, where the uncertainties are 2σ and represent precision only. The accuracy of the reported rate coefficients at the 95% confidence level is estimated to be 30-40% depending on the temperature. Model calculations suggest that gas phase processes initiated by ozone absorption of a UV photon represent about 1.4% of the currently estimated global source strength of atmospheric N2O. However, these processes could account for a significant fraction of the oxygen mass-independent enrichment observed in atmospheric N2O, and they appear to be the first suggested photochemical mechanism that is capable of explaining the altitude dependence of the observed mass-independent isotopic signature.
• Estupinan,Nicovich,Li,Cunnold,Wine

• p. 5880 - 5890

  (2002)
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• Reactivity of Rh+(CO)2 during the NO-CO and CO-O2 Reactions over Rh/Al2O3
• Exposure of Rh+(CO)2 on Rh/Al2O3 to NO causes CO desorption and adsorption of NO as Rh-NO+; exposure of Rh+(CO)2 to NO/H2 produced N2O at 573 K. The presenc
• Almusaiteer, Khalid A.,Chuang, Steven S. C.,Tan, Cher-Dip

• p. 247 - 247

  (2000)
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• Pd/NaY-zeolite and Pd-W/NaY-zeolite catalysts: Preparation, characterization and NO decomposition activity
• Pd/NaY-zeolite and Pd-W/NaY-zeolite catalysts were prepared from the compounds Pd(NO3)2 and [W(CO)6]. Tungsten was added by photochemical activation of [W(CO)6] to obtain a Pd-W interaction. The prepared catalysts were active for NO decomposition at 573 K leading mainly to N2 and N2O. NO conversion and the selectivity to N2O were studied as a function of time and the reduction temperature. The Pd/NaY-zeolite and the Pd-W/NaY-zeolite samples showed an initial period of high and constant activity followed by deactivation. Tungsten prevented the sintering of small Pd particles. Bimetallic sample deactivated faster, indicating that the Pd-W interaction decreased the fraction of exposed Pd atoms. The onset of N2O formation was in accord with the initiation of the deactivation.
• Pergher, Sibele B.C.,Dallago, Rogerio M.,Veses, Renato Cataluna,Gigola, Carlos E.,Baibich, Ione M.

• p. 107 - 115

  (2004)
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• Exploiting the synergy of titania and alumina in lean NOx reduction: In situ ammonia generation during the Pd/TiO2/Al 2O3-catalysed H2/CO/NO/O2 reaction
• In situ DRIFTS, XPS, HREM, XRD, and reactor studies have been used to examine and elucidate the catalytic performance of Pd particles supported on TiO2/Al2O3. These materials deliver 100% NOx conversion under demanding and technically relevant conditions (low temperature, high oxygen excess) in the presence of mixed H2+CO reductant feeds. In particular, they are far superior to the corresponding Pd/TiO2 and Pd/Al2O3 catalysts. It is shown that the synergy that operates between the titania and the alumina components involves the intrinsic surface chemistry of these oxides rather than formation of mixed oxide phases. Specifically, titania is critical for the formation of NCO on Pd while alumina promotes subsequent hydrolysis of NCO to ammonia, which then reduces NOx. At high temperature a second NOx reduction channel operates with Pd/TiO2/Al2O3 which greatly extends the useful temperature range. This also involves in situ formation of ammonia - in this case directly from reaction between H 2and NO.
• Macleod, Norman,Cropley, Rachael,Keel, James M.,Lambert, Richard M.

• p. 20 - 31

  (2004)
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• Rate constants for formation of NO in vibrational levels v=2 through 7 from the reaction N(4S) + O2 -> NO* + O
• Vibration-rotation spectra of the Δv=2 sequence of the nitric oxide formed by the chemiluminescent reaction N(4S) + O2 -> NO(X2Π) + O have been obtained with a spectral resolution of 15 cm-1.Emission bands due to N2O were observed to occur in the same spectral region as the first overtone of NO.These were experimentally eliminated and the resulting NO spectra were used to derive rate constants for formation of NO in vibrational levels v=2 through v=7.In units of 10-19 cm3/sec, these room temperature rate constants are, respectively, 55 +/- 14, 57 +/- 9, 33 +/- 3, 24 +/- 4, 7 +/- 2, and 5 +/- 2.Of all the nitric oxide molecules formed in the reaction, only 18percent are formed in levels v > 2.In terms of energy, of the 1.39 eV exothermicity of the reaction, about 10 percent goes into vibrational energy in levels v > 2.
• Rahbee, A.,Gibson, J. J.

• p. 5143 - 5148

  (1981)
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• Light-induced N2O production from a non-heme iron-nitrosyl dimer
• Two non-heme iron-nitrosyl species, [Fe2(N-Et-HPTB)(O2CPh)(NO)2](BF4)2 (1a) and [Fe2(N-Et-HPTB)(DMF)2(NO)(OH)](BF4)3 (2a), are characterized by FTIR and resonance Raman spectroscopy. Binding of NO is reversible in both complexes, which are prone to NO photolysis under visible light illumination. Photoproduction of N2O occurs in high yield for 1a but not 2a. Low-temperature FTIR photolysis experiments with 1a in acetonitrile do not reveal any intermediate species, but in THF at room temperature, a new {FeNO}7 species quickly forms under illumination and exhibits a η(NO) vibration indicative of nitroxyl-like character. This metastable species reacts further under illumination to produce N2O. A reaction mechanism is proposed, and implications for NO reduction in flavodiiron proteins are discussed.
• Jiang, Yunbo,Hayashi, Takahiro,Matsumura, Hirotoshi,Do, Loi H.,Majumdar, Amit,Lippard, Stephen J.,Monne-Loccoz, Pierre

• p. 12524 - 12527

  (2014)
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• Stabilization of ammonium dinitramide in the liquid phase
• The kinetics of accumulation of the main products of thermal decomposition of ammonium dinitramide in the melt was investigated. The isotope composition of nitrogen-containing gases evolved by the decomposition of 15NH4N(NO2/su
• Andreev,Anikin,Ivanov,Krylov,Pak

• p. 1974 - 1976

  (2000)
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• Photoassisted NO reduction with NH3 over TiO2 photocatalyst
• Photoassisted selective catalytic reduction of NO with ammonia (photo-SCR) at low temperature over irradiated TiO2 in a flow reactor was confirmed to proceed efficiently and the adsorbed ammonia reacted with NO under irradiation of TiO2.
• Tanaka, Tsunehiro,Teramura, Kentaro,Arakaki, Kyoko,Funabiki, Takuzo

• p. 2742 - 2743

  (2002)
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• The catalytic chemistry of HCN + NO2 over Na- and Ba-Y,FAU: An in situ FTIR and TPD/TPR study
• The adsorption of HCN and the reaction of HCN with NO2 over Na-, and Ba-Y,FAU zeolite catalysts were investigated using in situ FTIR and TPD/ TPR spectroscopies. Both catalysts adsorb HCN molecularly at room temperature, and the strength of ads
• Szanyi, János,Kwak, Ja Hun,Peden, Charles H. F.

• p. 1481 - 1490

  (2005)
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• Studies on the chemistry of tetraamminezinc(II) dipermanganate ([Zn(NH 3)4](MnO4)2): Low-temperature synthesis of the manganese zinc oxide (ZnMn2O4) catalyst precursor
• Tetraamminezinc(II) dipermanganate ([Zn(NH3)4] (MnO4)2 ; 1) was prepared, and its structure was elucidated with XRD-Rietveld-refinement and vibrational-spectroscopy methods. Compound 1 has a cubic lattice consisting of a 3D H-bound network built from blocks formed by four MnO4- anions and four [Zn(NH 3)4]2+ cations. The other four MnO 41 anions are located in a crystallographically different environment, namely in the cavities formed by the attachment of the building blocks. A low-temperature quasi-intramolecular redox reaction producing NH 4NO3 and amorphous ZnMn2O4 could be established occurring even at 100°. Due to H-bonds between the [Zn(NH 3)4]2+ cation and the MnO4 - anion, a redox reaction took place between the NH3 and the anion; thus, thermal deammoniation of compound 1 cannot be used to prepare [Zn(NH3)2](MnO4)2 (contrary to the behavior of the analogous perrhenate (ReO4-) complex). In solution-phase deammoniation, a temperature-dependent hydrolysis process leading to the formation of Zn(OH)2 and NH4MnO4 was observed. Refluxing 1 in toluene offering the heat convecting medium, followed by the removal of NH4NO3 by washing with H2O, proved to be an easy and convenient technique for the synthesis of the amorphous ZnMn2O4.
• Sajo, Istvan E.,Kotai, Laszlo,Keresztury, Gabor,Gacs, Istvan,Pokol, Gyoergy,Kristof, Janos,Soptrayanov, Bojan,Petrusevski, Vladimir M.,Timpu, Daniel,Sharma, Pradeep K.

• p. 1646 - 1658

  (2008)
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• Reversible N-N coupling of NO ligands on dinuclear ruthenium complexes and subsequent N2O evolution: Relevance to nitric oxide reductase
• Unprecedented N-N coupling of two nitrosyl ligands on dinuclear complexes was discovered, which is proposed as a critical step in the bacterial NO reductase (NOR). The N-N coupled complex (TpRu)2(μ-Cl)(μ-pz){μ-κ2-N(=O)-N(=O)} (2a) (Tp = BH(pyrazol-1-yl)3) was prepared from the reaction of TpRuCl2(NO) (1) with pyrazole in the presence of Et3N. The curious N-N bond distance was X-ray crystallographically determined to be 1.861(3) A for the N-N coupled analogue with a 4-methylpyrazolato bridge, and was confirmed by DFT calculation. The N-N bond of 2a was cleaved by oxidation to give [{TpRu(NO)}2(μ-Cl)(μ-pz)](BF4)2 (4a·(BF4)2), which on reduction reformed 2a. It is interesting to note that the N-N coupled complex 2a was also transformed into the oxo-bridged dinuclear species 5a with the evolution of N2O. These findings would provide valuable information regarding the mechanism of NO reduction to N2O by NOR. Copyright
• Arikawa, Yasuhiro,Asayama, Taiki,Moriguchi, Yusuke,Agari, Shoko,Onishi, Masayoshi

• p. 14160 - 14161

  (2007)
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• Efficient conversion of NO2 into N2 and O2 in N2 or into N2O5 in Air by 172-nm Xe 2 excimer lamp at atmospheric pressure
• Decomposition of NO2 (200 ppm) in N2 or air by 172-nm Xe2 excimer lamp was studied at 1 atm. The NO2 conversion in N2 was 99%, and the formation ratios of N2, O 2, NO, and N2O were 47, 98, 0, and 2%, respectively, after 30 min irradiation. The NO2 in air (5-20% O2) could be completely converted to N2O5 and HNO3 due to reactions by O3 and H2O after only 1.0-1.5 min irradiation. The present results give a new simple photochemical aftertreatment technique of NO2 in air without using any catalysts. Copyright
• Tsuji, Masaharu,Kawahara, Masashi,Senda, Makoto,Noda, Kenji

• p. 376 - 377

  (2007)
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• The mechanism of low-temperature ammonia oxidation on metal oxides according to the data of spectrokinetic measurements
• Low temperature NH3 oxidation on MoO3, Fe2O3, Cr2O3, and ZnO was studied by the spectrokinetic method. The following adsorbed species were intermediates in this reaction: NH3 and N2O on Fe2O3 and ZnO; NH3, N2O, and NO on Cr2O3. The following absorption bands were observed in the IR spectra obtained in the transmittance and diffuse-reflectance regimes under the reaction conditions: 2200/cm (ZnO and Fe2O3 and 2080/cm (Cr2O3). Taking into account that surface complexes with bands at 2200 and 2080/cm were formed in hydrazine oxidation, it was assumed that a hydrazine-like structure participates in NH3 oxidation. The presence of readsorption was associated with the high adsorption ability of NH3 (the characteristic time during which the stationary value of NH3 absorption band is settled in several seconds), the low flow rate of feed supply (50 mL/min), and the relatively small amount of the catalyst used (in the diffuse-reflectance method, ～1 cc of the catalyst was used). Under these conditions, the measurements of the rate constant of adsorbed NH3 consumption resulted in the underestimation of the values (for Cr2O3, the measured value was k6 = 3.5 × 10-3/sec, the calculated value, k6 = 0.2/sec).
• Sil'chenkova,Korchak,Matyshak

• p. 363 - 371

  (2002)
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• Mesostructured CeO2 and Pd/CeO2 nanophases: Templated synthesis, crystalline structure and catalytic properties
• This work reports a ceria solid and Pd/ceria catalyst prepared through a surfactant-templated synthesis route used for simultaneous abasement of NO and CO emissions. The surface features, textural properties and crystalline structure of ceria and Pd/ceria catalyst were studied by means of thermogravimetric analysis (TGA), N2 physisorption isotherms and in situ Fourier transform infrared (FT-IR) spectroscopy, high resolution electron transmission microscopy (TEM) and X-ray diffraction (XRD) techniques. In the calcination procedure, part of the adsorbed water on the surface of the solid was derived into unidentate and bidentate hydroxyls associated with surface cationic ions of ceria. The surfactant cations were strongly interacted with the solid during the preparation, which induces defects formation in the crystalline structure of the annealed ceria. The retained surfactant in the solid could be combusted to yield CO2, water and organic molecules with a small amount of coke-like deposits. The resultant ceria showed mesoporous texture and cubic phase containing lattice defects in the crystalline structure. The Pd/CeO2 catalyst was very active for NO reduction via CO with a high selectivity to N2. A 100% NO conversion with a selectivity to 100% N2 was achieved over the Pd/ceria catalyst at a reaction temperature of 300 °C. The catalytic activity and selectivity of this catalyst are much superior to the catalysts of Pt or Rh supported on TiO2, Al2O3, TiO 2-Al2O3 and ZrO2-Al 2O3 prepared by a sol-gel method. A possible reaction mechanism of NO reduction by CO over the Pd/CeO2 catalyst was discussed.
• Zhang,Yang,Shen,Wang

• p. 182 - 190

  (2005)
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• Nickel-mediated N-N bond formation and N2O liberationvianitrogen oxyanion reduction
• The syntheses of (DIM)Ni(NO3)2and (DIM)Ni(NO2)2, where DIM is a 1,4-diazadiene bidentate donor, are reported to enable testing of bis boryl reduced N-heterocycles for their ability to carry out stepwise deoxygenation of coordinated nitrate and nitrite, forming O(Bpin)2. Single deoxygenation of (DIM)Ni(NO2)2yields the tetrahedral complex (DIM)Ni(NO)(ONO), with a linear nitrosyl and κ1-ONO. Further deoxygenation of (DIM)Ni(NO)(ONO) results in the formation of dimeric [(DIM)Ni(NO)]2, where the dimer is linked through a Ni-Ni bond. The lost reduced nitrogen byproduct is shown to be N2O, indicating N-N bond formation in the course of the reaction. Isotopic labelling studies establish that the N-N bond of N2O is formed in a bimetallic Ni2intermediate and that the two nitrogen atoms of (DIM)Ni(NO)(ONO) become symmetry equivalent prior to N-N bond formation. The [(DIM)Ni(NO)]2dimer is susceptible to oxidation by AgX (X = NO3?, NO2?, and OTf?) as well as nitric oxide, the latter of which undergoes nitric oxide disproportionation to yield N2O and (DIM)Ni(NO)(ONO). We show that the first step in the deoxygenation of (DIM)Ni(NO)(ONO) to liberate N2O is outer sphere electron transfer, providing insight into the organic reductants employed for deoxygenation. Lastly, we show that at elevated temperatures, deoxygenation is accompanied by loss of DIM to form either pyrazine or bipyridine bridged polymers, with retention of a BpinO?bridging ligand.
• Beagan, Daniel M.,Cabelof, Alyssa C.,Carta, Veronica,Caulton, Kenneth G.,Gao, Xinfeng,Pink, Maren

• p. 10664 - 10672

  (2021)
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• Effects of O2 on the reduction of NO over prereduced CaO surfaces: A mechanistic understanding
• The effect of O2 on the reduction of NO over prereduced CaO surfaces is investigated. The experimental results suggest the existence of at least three different reaction channels, of which two are related to the high-temperature reduction of the CaO surfaces and involve the use of extra electrons in breaking the NO bond. The third reaction channel does not employ extra electrons for bond breaking, but the activity is affected by the amount of adsorbed surface oxygens. The difference between the former two reaction channels is found in the temperature needed for an observable activity. The reaction channel which is already active at low temperatures is described by a model based on F-centers, whereas the one which needs elevated temperatures involves a hole transport through the bulk. The activation energy for this transport is determined experimentally using a temperature-programmed reaction technique as well as theoretically by means of ab initio quantum chemistry calculations. Room-temperature exposure to O2 is suggested to result in a poisoning of the F-centers, but has only a minor effect on the reaction channel proposed for high temperatures. Effects on the reduction of NO of time as well as temperature for the O2 exposure step are also investigated and found to be consistent with an understanding based on the coexistence of different reaction channels. ? 1999 American Chemical Society.
• Acke, Filip,Panas, Itai

• p. 2195 - 2201

  (1999)
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• Modified Electronic Structure and Enhanched Catalytic Activity of Cobalt Tetraphenylporphirin Supported by Titanium Dioxide
• The electronic structure and the catalytic activity of cobalt tetraphenylporphirin supported on titanium dioxide (CoTPP/TiO2) were studied in order to reveal the electronic interaction between the oxide and the planar complex, which can modify the nature of the latter substance.CoTPP/TiO2 showed a sharp isotropic ESR signal at a g value of 2.003 and a UV band around 590 nm, values which were completely different from those of the unsupported CoTTP.The formation of an anionic radical, which has an odd electron in the porphyrin ring, is suggested.CoTTP?TiO2 showed remarkable catalytic activity for the reduction of nitric oxide to nitrous oxide and molecular nitrogen even at 50 deg C with hydrogen, which was found to be adsorbed on CoTTP/TiO2.The activity was much accelerated at 150 deg C, where a successive reduction of nitric oxide in the sequence NO --> N2O --> N2 was clearly indicated.
• Mochida, Isao,Tsuji, Kazuhiko,Suetsugu, Katsuya,Fujitsu, Hiroshi,Takeshita, Kenjiro

• p. 3159 - 3162

  (1980)
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• Catalytic activity of Ir for NO-CO reaction in the presence of SO2 and excess oxygen
• Catalytic performance of Ir catalysts for reduction of nitric oxide with carbon monoxide in the presence of SO2 and excess oxygen was investigated. NO was selectively reduced with CO on Ir/silicalite in an oxidizing atmosphere containing 1% to
• Ogura, Masaru,Kawamura, Aya,Matsukata, Masahiko,Kikuchi, Eiichi

• p. 146 - 147

  (2000)
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• Copper(I) Complex Mediated Nitric Oxide Reductive Coupling: Ligand Hydrogen Bonding Derived Proton Transfer Promotes N2O(g) Release
• A cuprous chelate bearing a secondary sphere hydrogen bonding functionality, [(PV-tmpa)CuI]+, transforms NO(g) to N2O(g) in high-yields in methanol. Ligand derived proton transfer facilitates N-O bond cleavage of a putative hyponitrite intermediate releasing N2O(g), underscoring the crucial balance between H-bonding capabilities and acidities in (bio)chemical NO(g) coupling systems.
• Wijeratne, Gayan B.,Bhadra, Mayukh,Siegler, Maxime A.,Karlin, Kenneth D.

• p. 17962 - 17967

  (2019)
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• Selective Reduction of NO by NH3 over Chromia on Titania Catalyst: Investigation and Modeling of the Kinetic Behavior
• The kinetics and the parametric sensitivity of the selective catalytic reduction (SCR) of NO by NH3 were investigated over a chromia on titania catalyst. The chromium oxide phase was made up predominantly of X-ray amorphous Cr2O3. High SCR activity and selectivity to N2 was attained at low temperatures. The high selectivity is attributed to the absence of significant amounts of CrO2 and crystalline α-Cr2O3 which favor N2O formation. The selectivity to N2O increased with higher temperature. Addition of up to 6% H2O to the dry feed reduced the rate of NO conversion and decreased the undesired formation of N2O. The effect of water on the catalytic behavior was reversible. In the absence of oxygen, the reaction between NO and NH3 became marginal independently whether H2O was present or not. Small amounts of oxygen were sufficient to restore SCR activity. Admission of SO2 to the SCR feed resulted in a severe loss of activity. The poisoning of the catalyst by SO2 was already notable for low SO2 concentrations (30 ppm) and for temperatures up to 573 K. X-ray photoelectron and FTIR spectroscopy revealed the presence of sulfate species on the catalyst surface. Analysis of the kinetic data indicated that the SCR reaction is first order in NO and zeroth order in NH3 for temperatures in the range 400-520 K. The estimated activation energies for dry and wet feed amounted to 60.0 ± 1.6 kJ/mol (95% confidence limits). For temperatures in the range 400-520 K, and for a SO2 free feed, the steady-state kinetic data could be well described with a model based on an Eley-Rideal type reaction between activated ammonia surface species and gaseous or weakly adsorbed NO.
• Willi,Maciejewski,Goebel,Koeppel,Baiker

• p. 356 - 367

  (1997)
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• On the mechanism of the selective catalytic reduction of NO with higher hydrocarbons over a silver/alumina catalyst
• SCR of NO with hydrocarbons has received much attention as one of the most promising and straightforward methods for reducing NOx emissions under conditions of excess oxygen. The possibility of forming nitrogen in the gas phase by reaction of activated forms of NOx with amines and NH3 as well as with other organic intermediates, which could be converted to amines and/or ammonia, was studied. Nitrohexane, hexylisocyanate, heptanenitrile, hexylamine, and NH3 were used as model compounds. Both NH3 and hexylamine reacted in the gas phase with activated NOx species to produce N2. Thus, it is possible to homogeneously convert NO to N2 by reaction with NH3 in excess oxygen at temperatures far below those reported for selective noncatalytic reduction of NO. Nitrohexane was transformed to NH3 in the presence of O2 over the Ag/alumina already at 250°C and the amounts of NH3 produced increased by the addition of H2O. The role of hydrogen on the hydrocarbon-SCR process involved several functions. Improved oxidation of all components was obtained in the presence of H2. In the oxidation of octane, addition of hydrogen increased the conversion from 41 to 73% at 350°C. Consequently, the improved oxidation rate of the hydrocarbon also resulted in faster formation of different oxygenates, which reacted and formed N-containing species. Hydrogen activated NO over the Ag/alumina catalyst for further reactions with the produced amines and NH3 or with other N-containing species in the gas phase.
• Eraenen, Kari,Klingstedt, Fredrik,Arve, Kalle,Lindfors, Lars-Eric,Murzin, Dmitry Yu.

• p. 328 - 343

  (2004)
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• Reaction of trans-[RuNO(NH3)4(OH)]Cl2 with nitric acid and synthesis of ammine(nitrato)nitrosoruthenium complexes
• The reaction of trans-[RuNO(NH3)4(OH)]Cl2 with nitric acid has been studied. Reaction prod- ucts have been identified by IR spectroscopy, NMR, mass spectrometry, powder and single-crystal X-ray dif- fraction, and chemical
• Kabin,Emel'yanov,Vorob'yev,Alferova,Tkachev,Baidina

• p. 1146 - 1153

  (2012)
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• TG-FTIR, DSC and ESCA characterization of histamine complexes with transition metal ions
• The thermoanalytical study of some MeHmx complexes (Hm = histamine; x = 1, 2) and MeHmx(NO3)2 (x = 2, 4) with Co(II), Ni(II) and Cu(II) is reported. By TG-FTIR coupled analysis,
• Materazzi,Curini,Gentili,D'Ascenzo

• p. 45 - 50

  (1997)
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• On the surface steps of a heterogeneous catalytic reaction
• Based on a study of the properties of intermediate complexes in the reactions of low-temperature ammonia oxidation and nitrogen oxide reduction in the presence and absence of oxygen on various catalysts, it was hypothesized that the sequence of steps in the formation of reaction products on chemically different catalysts can be the same if the initial adsorption forms of reactants are identical. In this case, variations in catalysts or reaction conditions affect the ratio between reaction rates.
• Matyshak

• p. 812 - 817

  (2007)
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• NO disproportionation reactivity of Fe tropocoronand complexes
• The synthesis and characterization of divalent [Fe(TC-5,5)] (1) and trivalent [Fe(OTf)(TC-5,5)] (2) tropocoronand complexes are described. Compound 1 reacts with 1 equiv of NO to form the {FeNO}7 complex 3. A single-crystal X-ray structure determination of 3 reveals a trigonal bipyramidal geometry with a linearly coordinated nitrosyl (Fe-N-O = 174.3(4)°) having a short Fe-N distance of 1.670(4) A?. EPR and Mossbauer spectroscopy, SQUID susceptometry, and normal coordinate analysis indicate 3 to be a low-spin {Fe(III)(NO-)}2+ species. In the presence of excess NO, 3 converts to a metastable nitrosyl-nitrito complex that decomposes by losing NO2, which subsequently nitrates the aromatic tropolone rings of the ligand. The final products of the NO disproportionation reaction are N2O and [Fe(NO)(TC-5,5-NO2)] (4). The v(NO) stretching band of 4 is increased to 1716 cm-1 from its value of 1692 cm-1 in 3, owing to the electron- withdrawing nitro groups on the ligand, and the compound no longer promotes the disproportionation of NO. Mechanistic aspects of the reaction are discussed.
• Franz, Katherine J.,Lippard, Stephen J.

• p. 10504 - 10512

  (1999)
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• A novel mechanism for poisoning of metal oxide SCR catalysts: Base-acid explanation correlated with redox properties
• 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

• p. 10031 - 10034

  (2014)
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• Dynamics of NO and N2O decomposition over Cu-ZSM-5 under transient reducing and oxidizing conditions
• Cu-ZSM-5 shows high activity for NO and N2O decomposition, a promising technique for controlling NOx emission. N2O and NO decomposition pathways on Cu-ZSM-5 were investigated by analyzing the adsorbate dynamics and changes in reactant and product concentrations using IR and MS under transient reducing and oxidizing conditions. Adsorbed oxygen produced from N2O showed different reactivity and dynamics from the adsorbed oxygen produced during NO decomposition. N2O decomposition proceeded via Cu+-ON2, Cu2+O-, and Cu2+O--ON2 with Cu2+-ON2 serving as a precursor for N2 formation and Cu2+O- as a precursor for O2 formation. NO decomposition proceeded via Cu2+(NO), Cu2+O-, and Cu2+(NO3- with Cu2+ serving as a precursor for NO dissociation. Cu+ in Cu+(NO) differed from that of Cu+ in Cu+-ON2, since the former may be associated with Al(OH)4- of the zeolite and the latter with Si(OH)4-.
• Konduru, Mahesh V.,Chuang, Steven S. C.

• p. 271 - 286

  (2000)
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• Monitoring of the evolved gases in apatite-ammonium sulfate thermal reactions
• Thermal reactions in natural fluorapatite or fluorcarbonate apatite and ammonium sulfate mixtures with mole ratio 1:4 at calcination up to 500°C were studied by simultaneous thermogravimetry and FTIR analysis of the evolved gases. The composition of natur
• Tonsuaadu, Kaia,Pelt,Borissova, Maria

• p. 655 - 658

  (2005)
• Read Online

• Metal-catalyzed anaerobic disproportionation of hydroxylamine. Role of diazene and nitroxyl intermediates in the formation of N2, N 2O, NO+, and NH3
• The catalytic disproportionation of NH2OH has been studied in anaerobic aqueous solution, pH 6-9.3, at 25.0 °C, with Na 3[Fe(CN)5NH3]·3H2O as a precursor of the catalyst, [FeII(CN)5H2O] 3-. The oxidation products are N2, N2O, and NO+ (bound in the nitroprusside ion, NP), and NH3 is the reduction product. The yields of N2/N2O increase with pH and with the concentration of NH2OH. Fast regime conditions involve a chain process initiated by the NH2 radical, generated upon coordination of NH2OH to [FeII(CN)5H 2O]3-. NH3 and nitroxyl, HNO, are formed in this fast process, and HNO leads to the production of N2, N 2O, and NP. An intermediate absorbing at 440 nm is always observed, whose formation and decay depend on the medium conditions. It was identified by UV-vis, RR, and 15NMR spectroscopies as the diazene-bound [Fe II(CN)5N2H2]3- ion and is formed in a competitive process with the radical path, still under the fast regime. At high pH's or NH2OH concentrations, an inhibited regime is reached, with slow production of only N2 and NH3. The stable red diazene-bridged [(NC)5FeHN=NHFe(CN)5] 6- ion is formed at an advanced degree of NH2OH consumption.
• Alluisetti, Graciela E.,Almaraz, Alejandra E.,Amorebieta, Valentin T.,Doctorovich, Fabio,Olabe, Jose A.

• p. 13432 - 13442

  (2004)
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• Evidence for Homolytic Decomposition of Ammonium Nitrate at High Temperature
• Rates of decomposition of ammonium nitrate in the liquid and vapor state have been measured at temperatures up to 400 deg C.The evidence indicates that an ionic mechanism operating at temperatures below 290 deg C is overtaken by a homolytic mechanism at higher temperatures.The activation energy increases to 193 kJ/mol, which is nearly equal to the N-O bond energy in HNO3.Water and NH3 strogly inhibit the ionic reaction at low temperature, but the effect fades away at high temperature.There is no primary H/D kinetic isotope effect.The reaction rates of liquid and vapor are nearly the same at high temperature.The rate at high temperature is given by (kT/h)e4.06e-23300/T.
• Brower, K. R.,Oxley, Jimmie C.,Tewari, Mohan

• p. 4029 - 4033

  (1989)
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• Selective hydrogenation of nitrate to nitrite in water over Cu-Pd bimetallic clusters supported on active carbon
• Hydrogenation of nitrate (200 ppm) in water with H2 over Cu-Pd clusters supported on active carbon (AC) was investigated at 333 K using a gas-liquid co-current flow system. Two types of Cu-Pd bimetallic clusters, stabilized with either poly(vinylpyrrolidone) (PVP) or sodium citrate (SC), revealed that the catalysts possessed similar activity (per unit weight of Pd) and high selectivity toward nitrite when pH was 10.5 at the outlet of the reactor. The high selectivity toward nitrite on PVP-stabilized cluster/AC was minimally influenced by the atomic ratio of Cu/Pd (=0.5-4.0); activity was maximal at a ratio of 1:1. Increasing pH to 12.4 by addition of NaOH enhanced the selectivity toward nitrite to 93% over SC-stabilized Cu0.63-Pd cluster/AC, but caused a decrease in the reaction rate. Over Cu0.63-Pd cluster/AC, hydrogenation of nitrite as an intermediate occurred much more slowly than that of nitrate at pH 10.5, suggesting that high selectivity toward nitrite is attained by OH- inhibiting adsorption of nitrite. XRD and STEM gave the size of the Cu0.63-Pd cluster on AC as 4 nm; the structure of the cluster remained almost unchanged during the reaction. The activity and selectivity of the Cu0.63-Pd cluster/AC was superior to those of the Cu0.63-Pd cluster on oxides such as TiO2, Al2O3, and ZrO2. In addition, the Cu0.63-Pd cluster/AC was more active and selective than conventionally prepared Cu0.63-Pd/AC, indicating that the Cu-Pd cluster is an excellent precursor for selective catalysts in the hydrogenation of nitrate to nitrite.
• Sakamoto, Yoshinori,Kamiya, Yuichi,Okuhara, Toshio

• p. 80 - 86

  (2006)
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• Carbon-Nitrogen and Nitrogen-Nitrogen Bond Formation from Nucleophilic Attack at Coordinated Nitrosyls in Fe and Ru Heme Models
• The conversion of inorganic NOx species to organo-N compounds is an important component of the global N-cycle. Reaction of a C-based nucleophile, namely the phenyl anion, with the ferric heme nitrosyl [(OEP)Fe(NO)(5-MeIm)]+ generates a mixture of the C-nitroso derivative (OEP)Fe(PhNO)(5-MeIm) and (OEP)Fe(Ph). The related reaction with [(OEP)Ru(NO)(5-MeIm)]+ generates the (OEP)Ru(PhNO)(5-MeIm) product. Reactions with the N-based nucleophile diethylamide results in the formation of free diethylnitrosamine, whereas the reaction with azide results in N2O formation; these products derive from attack of the nucleophiles on the bound NO groups. These results provide the first demonstrations of C-N and N-N bond formation from attack of C-based and N-based nucleophiles on synthetic ferric-NO hemes.
• Abucayon, Erwin G.,Powell, Douglas R.,Richter-Addo, George B.

• p. 9495 - 9498

  (2017)
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• Large Amplitude pH Oscillation in the Oxidation of Hydroxylamine by Iodate in a Continuous-Flow Stirred Tank Reactor
• Large amplitude pH oscillation occurs in the iodate oxidation of hydroxylamine in a continuous-flow tank reactor (CSTR) in a narrow range of flow rates and input concentrations.In addition to pH, the redox potential, the iodide ion concentration, the rate of gas (N2O) formation, and the color of the solution (I2) change periodically.The oscillatory period is extremely long, 2-6 h.The dynamical behaviour of the reaction was modeled by a scheme that takes into account the following component processes: the protonation equilibrium of NH2OH, the dissociation of water,the direct redox reaction between IO3- and NH3OH+, the Dushman reaction between IO3- and I-, the autoinhibitory reaction between I2 and NH3OH+, the fast dimerization of NOH to N2O, the reaction of NOH with NH2OH, and the volatility of iodine.Empirical rate laws of the component reactions were used successfully to calculate the kinetic behaviour in a closed system, as well as in the CSTR.
• Rabai, Gyula,Epstein, Irving R.

• p. 6361 - 6365

  (1990)
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• Thermal behaviour of ammonium nitrate prills coated with limestone and dolomite powder
• The thermal behaviour of ammonium nitrate (AN) and its prills coated with limestone and dolomite powder was studied on the basis of commercial fertilizer-grade AN and six Estonian limestone and dolomite samples. Coating of AN prills was carried out on a plate granulator and a saturated solution of AN was used as a binding agent. The mass of AN prills and coating material was calculated based on the mole ratio of AN/(CaO + MgO) = 2:1. Thermal behaviour of AN and its coated prills was studied using combined TG-DTA-FTIR equipment. The experiments were carried out under dynamic heating conditions up to 900 °C at the heating rate of 10 °C min-1 and for calculation of kinetic parameters, additionally, at 2, 5 and 20 °C min-1 in a stream of dry air. A model-free kinetic analysis approach based on the differential isoconversional method of Friedman was used to calculate the kinetic parameters. The results of TG-DTA-FTIR analyses and the variation of the value of activation energy E along the reaction progress α indicate the complex character of the decomposition of neat AN as well as of the interactions occurring at thermal treatment of AN prills coated with limestone and dolomite powder.
• Rudjak,Kaljuvee,Trikkel,Mikli

• p. 749 - 754

  (2010)
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• Correlation of structural characteristics with catalytic performance of CuO/CexZr1-xO2 catalysts for NO reduction by CO
• NO reduction by CO reaction was studied over a series of CuO/Ce xZr1-xO2 catalysts with different copper loadings and Ce/Zr molar ratios to evaluate the correlation of their structural characteristics with catalytic performance. These catalysts were investigated in detail by means of thermogravimetric analysis (TGA/DSC), X-ray diffraction (XRD), Raman spectroscopy, high-resolution transmission electron microscopy (HR-TEM), electron paramagnetic resonance (EPR), UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS) and H2-temperature-programmed reduction (H2-TPR) and in situ Fourier transform infrared spectroscopy (FTIR). The results demonstrated that the ceria-rich (pseudocubic t″) phase could disperse and stabilize the copper species more effectively and resulted in stronger interaction with copper than the zirconia-rich (t) phase. Furthermore, compared with the zirconia-rich phase, the synergistic interaction of copper with ceria-rich phase easily promoted the reduction of copper species and support surface oxygen, as well as the activation of adsorbed NO species. Therefore, CuO/Ce0.8Zr0.2O2 catalyst exhibited the higher activity for NO reduction than CuO/Ce 0.5Zr0.5O2 and CuO/Ce0.2Zr 0.8O2. A surface model was proposed to discuss these catalytic properties. The copper species at the interfacial area did not maintain an epitaxial relationship with CexZr1- xO2, while could penetrate into the CexZr 1-xO2 surface lattice by occupying the vacant site on the exposed (1 1 1) plane. The type and coordination environment of copper species were different in ceria-rich and zirconia-rich phases surface, and their stabilities were related to the lattice strains.
• Liu, Lianjun,Yao, Zhijian,Liu, Bin,Dong, Lin

• p. 45 - 60

  (2010)
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• Characterization and catalytic activity for the NO decomposition and reduction by CO of nanosized Co3O4
• Nanosized Co3O4 prepared by a precipitation method was characterized by TEM, XRD, BET and TPD techniques, and studied for NO decomposition and reduction by CO. It is found that Co3O4 thus obtained has a specific surface area of 23.4 m2/g and an average particle size of 26 nm. Catalytic tests showed that full NO conversion to N2 was obtained above 300 °C. A redox mechanism between Co 3+ and Co2+ ions based on NO decomposition is proposed.
• Zhang, Zhaoliang,Geng, Haoran,Zheng, Lisheng,Du, Bin

• p. 317 - 321

  (2005)
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• Electron transfer between azide and chlorine dioxide: The effect of solvent barrier nonadditivity
• The reaction of chlorine dioxide with excess azide in aqueous media proceeds with complex kinetics and produces N2, N2O, NO3-, Cl-, and ClO2-. In the presence of the spin trap PBN, the reaction is much simpler, and the rate law is -d [ClO2]/dt = k1 [ClO2] [N3-] [PBN]/([PBN] + [ClO2-]k-1/k2), with k1 = 809 M-1 s-1 and k-1/k2 = 19.0 at 25 °C. The inferred mechanism implies that k1 is the rate constant of electron transfer between ClO2 and N3-, k-1 is the reverse rate constant (N3 with ClO2-), and k2 is the rate constant for reaction of N3 with PBN. A dramatically lower value for k1 of 0.62 M-1 s-1 is calculated from the Marcus cross relationship and literature values for the self-exchange rates. The discrepancy is attributed to systematic errors in the literature self-exchange rates that were derived by applying the Marcus cross relationship to reactions of coordination complexes with N3- and ClO2. Such errors develop whenever this method is applied to reactions between species of widely differing size. Correcting for this effect leads to a calculated value of 56 M-1 s-1 for k1, which is in much improved agreement with the observed value. Similar corrections lead to greatly improved correlations for the self-exchange reaction of NO2 with NO2- and the electrontransfer reaction of ClO2 with NO2-.
• Awad,Stanbury

• p. 3636 - 3642

  (1993)
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• SURFACE STATES OF MoO3 ON ZrO2 AND CATALYTIC PROPERTIES FOR THE REACTION OF NO WITH H2
• The adsorption and reaction of nitric oxide on reduced molybdena-zirconia were studied by means of e.s.r., i.r. and u.v. spectroscopies.On the surface, at least two types of nitrosyl complex exist.At an early stage of reduction, a diamagnetic dinitrosyl complex with i.r. bands at ca. 1790 and 1690 cm-1 formed on NO adsorption and was ascribed to Mo(4+)(NO)2.After reduction at a higher temperature, a paramagnetic dinitrosyl species appeared upon NO adsorption and was tentatively assigned to Mo(5+)(NO)2.Nitric oxide can adsorb on Mo(5+) in tetrahedral coordination, but not on Mo(5+) in octahedral coordination.This can be explained by the coordination being limited.For the reaction of NO with H2, the species of Mo(5+)(NO)2 was concluded to be a main active complex in the catalytic cycle.
• Iizuka, Tokio,Itoh, Masahumi,Hattori, Hideshi,Tanabe, Kozo

• p. 501 - 508

  (1982)
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• Theoretical Evidence for Two New Intermediate Xenon Species: Xenon Azide Fluoride, FXe(N3), and Xenon Isocyanate Fluoride, FXe(NCO)
• The reaction behavior of xenon difluoride, XeF2, toward HN3, NaN3, and NaOCN was investigated in H2O, aHF (anhydrous HF), and SO2ClF solution. The analysis of the final reaction products (XeF2 + HN3 (NaN3) in H2O → HF, N2, N2O, Xe; XeF2 + HN3 in aHF → N2, Xe, N2F2; XeF2 + HOCN (NaOCN) in H2O → HF, N2, N2O, NH3, CO2, Xe) indicated the intermediate formation of FXe(N3) and FXe(NCO) and revealed different reaction mechanisms for both compounds. Both intermediates, FXe(N3) and FXe(NCO), were studied on the basis of ab initio computations at HF and correlated MP2 levels using a quasirelativistic LANL2DZ pseudopotential for Xe. Both were shown to possess stable minima at HF and MP2 levels (no imaginary frequencies) with the following structural parameters (MP2/LANL2DZ). FXe(N3): Cs; d(F-Xe) = 2.051, d(Xe-N1) = 2.318, d(N1-N2) = 1.241, d(N2-N3) = 1.180 ?; s; d(F-Xe) = 2.024, d(Xe-N) = 2.206, d(N-C) = 1.194, d(C-N) = 1.231 ?; -1.
• Schulz, Axel,Klap?tke, Thomas M.

• p. 1929 - 1933

  (1997)
• Read Online

• Investigation of the NO reduction by CO reaction over oxidized and reduced NiOx/CeO2catalysts
• CeO2-supported NiOxcatalysts have been widely studied in various catalytic reactions including NO reduction by CO. This work is mainly focused on investigation of the impact of catalyst synthesis conditions (e.g., oxidation and reduc
• Boscoboinik, Jorge Anibal,Hwang, Sooyeon,Kim, Taejin,Kwon, Gihan,Lee, Kyung-Min

• p. 7850 - 7865

  (2021/12/27)
• 

• The influence of Ba addition on thermal stability and catalytic activity of Cu-based mixed oxide
• Catalytic reduction of NO by CO was studied over La2-xBaxCuO4 (x = 0.0 or 0.4) mixed oxides prepared by coprecipitation method. The catalysts were characterized by X ray diffraction (XRD), O2 temperature-programmed desorption (O2-TPD), H2 temperature-programmed reduction (H2-TPR) and X-ray absorption near edge structure (XANES). NO + CO reaction was carried out in a fixed-bed flow reactor, from room temperature to 500 °C, at atmospheric pressure. Both fresh catalysts were active for the NO + CO reaction but when were submitted to thermal aging, the barium free catalyst significantly lost its activity. The partial substitution of La by Ba enhanced the thermal stability and although the activity of the catalyst has decreased, it remains high, approaching 100 % at 500 °C. These results can be associated with reducible copper species observed by XANES in the thermal aged catalyst containing Ba.
• Rachele, Karen Gon?alves,Palacio, Luz Amparo,Zotin, Fatima Maria Zanon

• p. 234 - 242

  (2020/07/15)
• 

• Short-lived intermediate in N2O generation by P450 NO reductase captured by time-resolved IR spectroscopy and XFEL crystallography
• Nitric oxide (NO) reductase from the fungus Fusarium oxysporum is a P450-type enzyme (P450nor) that catalyzes the reduction of NO to nitrous oxide (N2O) in the global nitrogen cycle. In this enzymatic reaction, the heme-bound NO is activated by the direct hydride transfer from NADH to generate a short-lived intermediate (I), a key state to promote N–N bond formation and N–O bond cleavage. This study applied time-resolved (TR) techniques in conjunction with photolabile-caged NO to gain direct experimental results for the characterization of the coordination and electronic structures of I. TR freeze-trap crystallography using an X-ray free electron laser (XFEL) reveals highly bent Fe–NO coordination in I, with an elongated Fe–NO bond length (Fe–NO = 1.91 ?, Fe–N–O = 138°) in the absence of NAD+. TR-infrared (IR) spectroscopy detects the formation of I with an N–O stretching frequency of 1,290 cm?1 upon hydride transfer from NADH to the Fe3+–NO enzyme via the dissociation of NAD+ from a transient state, with an N–O stretching of 1,330 cm?1 and a lifetime of ca. 16 ms. Quantum mechanics/ molecular mechanics calculations, based on these crystallographic and IR spectroscopic results, demonstrate that the electronic structure of I is characterized by a singly protonated Fe3+–NHO?? radical. The current findings provide conclusive evidence for the N2O generation mechanism via a radical–radical coupling of the heme nitroxyl complex with the second NO molecule.
• Nomura, Takashi,Kimura, Tetsunari,Kanematsu, Yusuke,Yamada, Daichi,Yamashita, Keitaro,Hirata, Kunio,Ueno, Go,Murakami, Hironori,Hisano, Tamao,Yamagiwa, Raika,Takeda, Hanae,Gopalasingam, Chai,Kousaka, Ryota,Yanagisawa, Sachiko,Shoji, Osami,Kumasaka, Takashi,Yamamoto, Masaki,Takano, Yu,Sugimoto, Hiroshi,Tosha, Takehiko,Kubo, Minoru,Shiro, Yoshitsugu

• (2021/05/28)
• 

• The Effects of Platinum Dispersion and Pt State on Catalytic Properties of Pt/Al2O3 in NH3 Oxidation
• Dependence of NH3 oxidation on the state and dispersion of Pt species in Pt/γ-Al2O3 catalysts was investigated. Prereduced Pt/γ-Al2O3 catalysts containing Pt0 nanoparticles exhibited significantly higher activity than preoxidized ones with the same Pt dispersion. The most significant improvement of the catalytic activity (TOF increased by 30 times) was observed when the size of Pt0 particles increased from ～1 to ～8 nm. N2 selectivity was found to be mainly determined by the reaction temperature, with a minor influence of Pt particle size. Preoxidized catalysts containing ionic Pt were activated by the reaction medium, while partial deactivation was observed for the prereduced ones. The activity improvement was associated with the presence of Pt4+/Pt2+ species on the surface of preoxidized catalysts. The activity decrease of the prereduced catalysts was due to the partial oxidation and subsequent redispersion of Pt particles. Introduction of H2O and CO2 to the reaction mixture only moderately influenced NH3 oxidation activity shifting NH3 conversion curves by about +15 °C.
• Slavinskaya, Elena M.,Kibis, Lidiya S.,Stonkus, Olga A.,Svintsitskiy, Dmitry A.,Stadnichenko, Andrei I.,Fedorova, Elizaveta A.,Romanenko, Anatolii V.,Marchuk, Vasyl,Doronkin, Dmitry E.,Boronin, Andrei I.

• p. 313 - 327

  (2020/10/30)
• 

• Solid-gas reactions for nitroxyl (HNO) generation in the gas phase
• We present a novel nitroxyl (HNO) generation method, which avoids the need of using a liquid system or extreme experimental conditions. This method consists of the reaction between a gaseous base and an HNO donor (Piloty's acid) in the solid phase, allowi
• Carrone, Guillermo,Mazzeo, Agostina,Marceca, Ernesto,Pellegrino, Juan,Suárez, Sebastián,Zarenkiewicz, Jessica,Toscano, John P.,Doctorovich, Fabio

• (2021/07/25)
• 

• Electrochemical Nitric Oxide Reduction on Metal Surfaces
• Electrocatalytic denitrification is a promising technology for removing NOx species (NO3?, NO2? and NO). For NOx electroreduction (NOxRR), there is a desire for understanding the catalytic parameters that control the product distribution. Here, we elucidate selectivity and activity of catalyst for NOxRR. At low potential we classify metals by the binding of *NO versus *H. Analogous to classifying CO2 reduction by *CO vs. *H, Cu is able to bind *NO while not binding *H giving rise to a selective NH3 formation. Besides being selective, Cu is active for the reaction found by an activity-volcano. For metals that does not bind NO the reaction stops at NO, similar to CO2-to-CO. At potential above 0.3 V vs. RHE, we speculate a low barrier for N coupling with NO causing N2O formation. The work provides a clear strategy for selectivity and aims to inspire future research on NOxRR.
• Bagger, Alexander,Rossmeisl, Jan,Wan, Hao
• supporting information

  p. 21966 - 21972

  (2021/09/02)
• 

• Preparation of g-C3N4 Nanosheets/CuO with Enhanced Catalytic Activity on the Thermal Decomposition of Ammonium Perchlorate
• 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

• p. 982 - 988

  (2021/02/26)
• 

• Investigation of kinetic parameters for ammonium perchlorate thermal decomposition in presence of gCN/CuO by TG-MS analysis and kinetic compensation correction
• 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.

• (2021/06/25)
• 

• NO Reduction to N2O Triggered by a Dinuclear Dinitrosyl Iron Complex via the Associated Pathways of Hyponitrite Formation and NO Disproportionation
• In spite of the comprehensive study of the metal-mediated conversion of NO to N2O disclosing the conceivable processes/mechanism in biological and biomimetic studies, in this study, the synthesis cycles and mechanism of NO reduction to N2O triggered by the electronically localized dinuclear {Fe(NO)2}10-{Fe(NO)2}9 dinitrosyl iron complex (DNIC) [Fe(NO)2(μ-bdmap)Fe(NO)2(THF)] (1) (bdmap = 1,3- bis(dimethylamino)-2-propanolate) were investigated in detail. Reductive conversion of NO to N2O triggered by complex 1 in the presence of exogenous ·NO occurs via the simultaneous formation of hyponitrite-bound {[Fe2(NO)4(μ-bdmap)]2(κ4-N2O2)} (2) and [NO2]-bridged [Fe2(NO)4(μ-bdmap)(μ-NO2)] (3) (NO disproportionation yielding N2O and complex 3). EPR/IR spectra, single-crystal X-ray diffraction, and the electrochemical study uncover the reversible redox transformation of {Fe(NO)2}9-{Fe(NO)2}9 [Fe2(NO)4(μ-bdmap)(μ-OC4H8)]+ (7) ? {Fe(NO)2}10-{Fe(NO)2}9 1 ? {Fe(NO)2}10-{Fe(NO)2}10 [Fe(NO)2(μ-bdmap)Fe(NO)2]- (6) and characterize the formation of complex 1. Also, the synthesis study and DFT computation feature the detailed mechanism of electronically localized {Fe(NO)2}10-{Fe(NO)2}9 DNIC 1 reducing NO to N2O via the associated hyponitrite-formation and NO-disproportionation pathways. Presumably, the THF-bound {Fe(NO)2}9 unit of electronically localized {Fe(NO)2}10-{Fe(NO)2}9 complex 1 served as an electron buffering reservoir for accommodating electron redistribution, and the {Fe(NO)2}10 unit of complex 1 acted as an electron-transfer channel to drive exogeneous ·NO coordination to yield proposed relay intermediate κ2-N,O-[NO]-bridged [Fe2(NO)4(μ-bdmap)(μ-NO)] (A) for NO reduction to N2O.
• Wu, Wun-Yan,Tsai, Ming-Li,Lai, Yi-An,Hsieh, Chieh-Hsin,Liaw, Wen-Feng

• p. 15874 - 15889

  (2021/06/21)
• 

• A Monohydrosulfidodinitrosyldiiron Complex That Generates N2O as a Model for Flavodiiron Nitric Oxide Reductases: Reaction Mechanism and Electronic Structure
• Flavodiiron nitric oxide reductases (FNORs) protect microbes from nitrosative stress under anaerobic conditions by mediating the reduction of nitric oxide (NO) to nitrous oxide (N2O). The proposed mechanism for the catalytic reduction of NO by FNORs involves a dinitrosyldiiron intermediate with a [hs-{FeNO}7]2 formulation, which produces N2O and a diferric species. Moreover, both NO and hydrogen sulfide (H2S) have been implicated in several similar physiological functions in biology and are also known to cross paths in cell signaling. Here we report the synthesis, spectroscopic and theoretical characterization, and N2O production activity of an unprecedented monohydrosulfidodinitrosyldiiron compound, with a [(HS)hs-{FeNO}7/hs-{FeNO}7] formulation, that models the key dinitrosyl intermediate of FNORs. The generation of N2O from this unique compound follows a semireduced pathway, where one-electron reduction generates a reactive hs-{FeNO}8 center via the occupation of an Fe-NO antibonding orbital. In contrast to the well-known reactivity of H2S and NO, the coordinated hydrosulfide remains unreactive toward NO and acts only as a spectator ligand during the NO reduction process.
• Pal, Nabhendu,White, Corey J.,Demeshko, Serhiy,Meyer, Franc,Lehnert, Nicolai,Majumdar, Amit

• p. 15890 - 15900

  (2021/06/28)
• 

• Mechanistic Pathways for N2O Elimination from trans-R3Sn-O-N=N-O-SnR3and for Reversible Binding of CO2to R3Sn-O-SnR3(R = Ph, Cy)
• The rate and mechanism of the elimination of N2O from trans-R3Sn-O-N=N-O-SnR3 (R = Ph (1Ph) and R = Cy (1Cy)) to form R3Sn-O-SnR3 (R = Ph (2Ph) and R = Cy (2Cy)) have been studied using both NMR and IR techniques to monitor the reactions in the temperature range of 39-79 °C in C6D6. Activation parameters for this reaction are ΔH? = 15.8 ± 2.0 kcal·mol-1 and ΔS? = -28.5 ± 5 cal·mol-1·K-1 for 1Ph and ΔH? = 22.7 ± 2.5 kcal·mol-1 and ΔS? = -12.4 ± 6 cal·mol-1·K-1 for 1Cy. Addition of O2, CO2, N2O, or PPh3 to sealed tube NMR experiments did not alter in a detectable way the rate or product distribution of the reactions. Computational DFT studies of elimination of hyponitrite from trans-Me3Sn-O-N=N-O-SnMe3 (1Me) yield a mechanism involving initial migration of the R3Sn group from O to N passing through a marginally stable intermediate product and subsequent N2O elimination. Reactions of 1Ph with protic acids HX are rapid and lead to formation of R3SnX and trans-H2N2O2. Reaction of 1Ph with the metal radical ?Cr(CO)3C5Me5 at low concentrations results in rapid evolution of N2O. At higher ?Cr(CO)3C5Me5 concentrations, evolution of CO2 rather than N2O is observed. Addition of 1 atm or less CO2 to benzene or toluene solutions of 2Ph and 2Cy resulted in very rapid reaction to form the corresponding carbonates R3Sn-O-C(=O)-O-SnR3 (R = Ph (3Ph) and R = Cy (3Cy)) at room temperature. Evacuation results in fast loss of bound CO2 and regeneration of 2Ph and 2Cy. Variable temperature data for formation of 3Cy yield ΔHo = -8.7 ± 0.6 kcal·mol-1, ΔSo = -17.1 ± 2.0 cal·mol-1·K-1, and ΔGo298K = -3.6 ± 1.2 kcal·mol-1. DFT studies were performed and provide additional insight into the energetics and mechanisms for the reactions.
• Captain, Burjor,Davis, Jack V.,Gamage, Mohan M.,Guio, Oswaldo,Hoff, Carl D.,Temprado, Manuel
• supporting information

  p. 12075 - 12084

  (2021/08/24)
• 

• FeVO4-supported Mn-Ce oxides for the low-temperature selective catalytic reduction of NOxby NH3
• Iron vanadate (FeVO4) nanorods are used as a carrier to support manganese (Mn) and cerium (Ce) oxides for the selective catalytic reduction (SCR) of nitrogen oxides (NOx) with NH3for the first time. Among these developed Ce-Mn/FeVO4catalysts with different molar ratios of Ce/Mn, the Ce0.2Mn0.2/FeVO4catalyst exhibits the best de-NOxperformance and N2selectivity, which are higher than 90% in a wide temperature window of 90-420 °C. Through a series of characterization techniques, it is found that the synergistic effect between Ce and Mn enhances the reduction ability and the number of acid sites on the catalyst, which facilitates the adsorption and conversion of flue gas. The introduction of an appropriate ratio of Ce/Mn increases the concentration of Mn4+and chemisorbed oxygen (OS) on the catalyst, leading to a “fast SCR reaction” with oxidizing NO to NO2, which significantly improves the low-temperature de-NOxefficiency. In addition, the interaction between the active components (Ce/Mn) and the support (FeVO4) increases the de-NOxperformance of Ce0.2Mn0.2/FeVO4at high temperatures. In the meantime, the Mn4++ Ce3+? Mn3++ Ce4+reduction electron pair formed between Ce and Mn promotes the transport of electrons, which is also beneficial for the SCR reaction at low temperature. Thein situdiffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) reveals that the SCR reaction over Ce0.2Mn0.2/FeVO4catalyst follows both Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) reaction mechanisms.
• Cheng, Yonghong,He, Chi,Liu, Wei,Ma, Dandan,Niu, Cihang,Shi, Jian-Wen,Wang, Baorui,Wang, Hongkang,Xiao, Lei,Zhao, Shuqi

• p. 6770 - 6781

  (2021/10/25)
• 

• NO Coupling by Nonclassical Dinuclear Dinitrosyliron Complexes to Form N2O Dictated by Hemilability
• Selective coupling of NO by a nonclassical dinuclear dinitrosyliron complex (D-DNIC) to form N2O is reported. The coupling is facilitated by the pyridinediimine (PDI) ligand scaffold, which enables the necessary denticity changes to produce mixed-valent, electron-deficient tethered DNICs. One-electron oxidation of the [{Fe(NO)2}]210/10 complex Fe2(PyrrPDI)(NO)4 (4) results in NO coupling to form N2O via the mixed-valent {[Fe(NO)2]2}9/10 species, which possesses an electron-deficient four-coordinate {Fe(NO)2}10 site, crucial in N-N bond formation. The hemilability of the PDI scaffold dictates the selectivity in N-N bond formation because stabilization of the five-coordinate {Fe(NO)2}9 site in the mixed-valent [{Fe(NO)2}]29/10 species, [Fe2(Pyr2PDI)(NO)4][PF6] (6), does not result in an electron-deficient, four-coordinate {Fe(NO)2}10 site, and hence no N-N coupling is observed.
• Marks, Walker R.,Reinheimer, Eric W.,Seda, Takele,Zakharov, Lev N.,Gilbertson, John D.

• p. 15901 - 15909

  (2021/10/01)
• 

• An Integrated View of Nitrogen Oxyanion Deoxygenation in Solution Chemistry and Electrospray Ion Production
• There has been an increasing interest in chemistry involving nitrogen oxyanions, largely due to the environmental hazards associated with increased concentrations of these anions leading to eutrophication and aquatic dead zones . Herein, we report the synthesis and characterization of a suite of MNOx complexes (M = Co, Zn: x = 2, 3). Reductive deoxygenation of cobalt bis(nitrite) complexes with bis(boryl)pyrazine is faster for cobalt than previously reported nickel, and pendant O-bound nitrito ligand is still readily deoxygenated, despite potential implication of an isonitrosyl primary product. Deoxygenation of zinc oxyanion complexes is also facile, despite zinc being unable to stabilize a nitrosyl ligand, with liberation of nitric oxide and nitrous oxide, indicating N-N bond formation. X-ray photoelectron spectroscopy is effective for discriminating the types of nitrogen in these molecules. ESI mass spectrometry of a suite of M(NOx)y (x = 2, 3 and y = 1, 2) shows that the primary form of ionization is loss of an oxyanion ligand, which can be alleviated via the addition of tetrabutylammonium (TBA) as a nonintuitive cation pair for the neutral oxyanion complexes. We have shown these complexes to be subject to deoxygenation, and there is evidence for nitrogen oxyanion reduction in several cases in the ESI plume. The attractive force between cation and neutral is explored experimentally and computationally and attributed to hydrogen bonding of the nitrogen oxyanion ligands with ammonium α-CH2 protons. One example of ESI-induced reductive dimerization is mimicked by bulk solution synthesis, and that product is characterized by X-ray diffraction to contain two Co(NO)2+ groups linked by a highly conjugated diazapolyene.
• Beagan, Daniel M.,Cabelof, Alyssa C.,Pepin, Robert,Pink, Maren,Carta, Veronica,Caulton, Kenneth G.
• supporting information

  p. 17241 - 17248

  (2021/11/17)
• 

• Effects of Ni loading on the physicochemical properties of NiO: X/CeO2 catalysts and catalytic activity for NO reduction by CO
• Transition metal oxide catalysts have been investigated extensively because of their relatively low cost and high activity in many chemical reactions. In this work, a series of NiOx/CeO2 catalysts (0.5-30 wt% Ni) were prepared using the incipient wetness impregnation method. These catalysts were tested with various characterization techniques, including Brunauer-Emmett-Teller (BET) theory, Raman spectroscopy, X-ray powder diffraction (XRD), hydrogen temperature-programmed reduction (H2-TPR) and gas chromatography (GC) for their physicochemical properties, surface properties, reduction properties and catalytic activities in the NO reduction by CO reaction. The increase in Ni loading of the catalyst (up to 5% NiOx/CeO2) led to the decrease in specific surface area, formation of NiOx crystalline structures on the CeO2 surface, easier reduction of the catalyst compared to bulk NiOx and bulk CeO2, and increase in catalytic activity in the NO reduction by CO reaction. From these results, the surface dispersion of NiOx and the formation of monolayer NiOx coverage of the catalysts were believed to affect the catalytic activity greatly. The results provided insights into the structure-activity relationship of NiOx/CeO2 catalysts for the NO reduction by CO reaction.
• Kim, Do Heui,Kim, Taejin,Lee, Jaeha,Zhang, Shuhao

• p. 2359 - 2368

  (2020/06/17)
• 

• Effects of iron precursor and loading on the catalytic performance of FeOx/CeO2 catalysts for NO reduction by CO
• During the catalyst synthesis process, the precursor chosen could have great impact on the physiochemical and surface properties of the catalysts. More importantly, the precursor could result in very different catalytic activities of the catalyst. In this work, two series of FeOx/CeO2 catalysts were prepared using iron nitrate/sulfate precursors with a wide range of Fe loading (1 wtpercent – 30 wtpercent). The catalytic activity, physical property, surface morphology and surface/molecular structure were investigated using GC, BET, XRD, Raman, FT-IR as well as SEM and EDS techniques. From the results, although the physical properties (specific surface area, total pore volume) of the catalyst were similar with different precursors, the surface composition and molecular structures were very different. The iron nitrate precursor fully transformed into FeOx after the calcination process, whereas the iron sulfate precursor only partially transformed into FeOx, leaving some FeSO4 on the catalyst surface. The catalytic activity results suggested that a near monolayer coverage of FeOx on the catalyst surface was crucial to increase the catalytic activity in the NO reduction by CO reaction, while the presence of FeSO4 had advert impacts on the catalytic activity.
• Kim, Taejin,Zhang, Shuhao

• (2020/07/27)
• 

• Selective catalytic oxidation of ammonia over LaMAl11O19-: δ (M = Fe, Cu, Co, and Mn) hexaaluminates catalysts at high temperatures in the Claus process
• 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

• p. 1477 - 1491

  (2020/03/23)
• 

• Ce regulated surface properties of Mn/SAPO-34 for improved NH3-SCR at low temperature
• Ce modified MnOx/SAPO-34 was prepared and investigated for low-temperature selective catalytic reduction of NOx with ammonia (NH3-SCR). The 0.3Ce-Mn/SAPO-34 catalyst had nearly 95% NO conversion at 200-350 °C at a space velocity of 10000 h-1. Microporous SAPO-34 as the support provided the catalyst with increased hydrothermal stability. XPS and H2-TPR results proved that the Mn4+ and Oα content increased after incorporation of Ce, this promoted the conversion of NO at low temperature via a 'fast SCR' route. NH3-TPD measurements combined oxidation experiments of NO, NH3 indicated the reduction of both the surface acidity and the amount of acid sites, which effectively decreased the NH3 oxditaion to NO or N2O at elevated temperature and promoted the catalytic selectivity for nitrogen. A redox cycle between manganese oxide and Ce was assumed for the active oxygen transfer and facilitated the catalyst durability.
• Chen, Qizhi,Du, Jun,Liu, Zuohua,Luo, Hang,Tao, Changyuan,Tong, Zhangfa,Yang, Yong

• p. 40047 - 40054

  (2020/11/18)
• 

• Spotlight on Large Surface Copper Cluster Role of Cu-SAPO-34 Catalyst in Standard NH3-SCR Performances
• In the present study, the catalytic role and behavior of different copper cluster configurations during NH3 SCR, NO and NH3 oxidation reactions will be studied in detail. For this purpose, two preparation methods were performed. The physico-chemical and surface properties were characterized by different techniques, such as XRD, ICP, N2 ads/des, HR-TEM, XPS, NMR, ex-situ/in-situ DRIFT, NH3 TPD and H2 TPR, in order to evaluate the impact of copper incorporation method on redox active sites, and, as a consequence, to better understand the mechanism of the NH3 SCR reaction.
• Gaillard, Fran?ois,Gil, Sonia,Giroir-Fendler, Anne,Pétaud, Guillaume,Tayakout, Melaz

• (2020/04/29)
• 

• A series of guanidine salts of 3,6-bis-nitroguanyl-1,2,4,5-tetrazine: Green nitrogen-rich gasgenerating agent
• Nitrogen-rich energetic materials (EMs) have been widely studied because of their high thermal stability, insensitivity, excellent detonation performance and non-toxic characteristics. In particular, these compounds are well applied as gas-generating agents (GGAs). As a nitrogen-rich heterocyclic framework, 1,2,4,5-tetrazine derivatives have shown great potential in the design of GGAs. The guanidine salts of 3,6-bis-nitroguanyl-1,2,4,5-tetrazine (DNGTz), guanidine (G2DNGTz) (1), aminoguanidine (AG2DNGTz) (2), diaminoguanidine (DAG2DNGTz) (3), and triaminoguanidine (TAG2DNGTz) (4) have been synthesized and characterized by elemental analysis and FT-IR. The crystal structures of 1 and 2 were obtained by X-ray single crystal diffraction. Crystal analysis shows that 1 and 2 arrange through zigzagchain- like assembly and face-to-face geometries, which is helpful in decreasing mechanical sensitivity. The thermal stability and thermal decomposition kinetics of these four salts were studied by Differential Scanning Calorimetry (DSC). Furthermore, the thermogravimetry-Fourier transform infrared-mass spectrometry (TG-FTIR-MS) analysis of thermal decomposition products reveals that the main decomposition gaseous products are H2O, N2O, CO2, NO, N2and NH3. Then, the cytotoxicity of the four salts was tested by MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide) method, and it was found that salts 1 4 show slight cytotoxicity in mouse fibroblasts (L929), at a concentration of 0.125 mg ml-1. The insensitivity, low toxicity, and production of clean gases without solid residue after burning of salt 1 indicate that it can be used as a potential green energetic material for GGAs.
• Cong, Zhang,Daidi, Fan,Haixia, Ma,Xiang, Chen,Yang, Bai,Yongpeng, Hu,Zhaoqi, Guo

• (2020/12/03)
• 

• The role of cobalt oxide or magnesium oxide in ozonation of ammonia nitrogen in water
• In this study, the reaction mechanisms for ozonation of ammonia nitrogen in the presence of Co3O4 or MgO were investigated. For the reaction over Co3O4, Cl– in the reaction solution was indispensable and ClO– was formed by a non-catalytic oxidation of Cl–. Co3O4 promoted the reaction of NH4+ with ClO– to give the products including NO3–, chloramines and gaseous products. In contrast, Cl– was unnecessary for the reaction with MgO. pH of the reaction solution was maintained at around 9 throughout the reaction owing to partial dissolution of MgO. Ammonia nitrogen was decomposed to mainly NO3– by non-catalytic radical reaction involving OH·, which was formed by the reaction of OH– with O3 in weakly basic solution. To keep the reaction solution weakly basic, H+ formed with the decomposition of NH4+ was neutralized. As a result, about the same amount of Mg2+ as that of decomposed ammonia nitrogen was dissolved.
• Anggo Krisbiantoro, Philip,Togawa, Tomokazu,Mahardiani, Lina,Aihara, Haruka,Otomo, Ryoichi,Kamiya, Yuichi

• (2020/03/23)
• 

• Photoinduced NO and HNO Production from Mononuclear {FeNO}6 Complex Bearing a Pendant Thiol
• Light triggers the formation of HNO from a metal-nitrosyl species, facilitated by an intramolecular pendant thiol proton. Two {FeNO}6 complexes (the Enemark-Felthan notation), [Fe(NO)(TMSPS2)(TMSPS2H)] (1, TMSPS2H2 = 2,2′-dimercapto-3,3′-bis(trimethylsilyl)diphenyl)phenylphosphine; H is a dissociable proton) with a pendant thiol and [Fe(NO)(TMSPS2)(TMSPS2CH3)] (2) bearing a pendant thioether, are spectroscopically and structurally characterized. Both complexes are highly sensitive to visible light. Upon photolysis, complex 2 undergoes NO dissociation to yield a mononuclear Fe(III) complex, [Fe(TMSPS2)(TMSPS2CH3)] (3). In contrast, the pendant SH of 1 can act as a trap for the departing NO radical upon irradiation, resulting in the formation of an intermediate A with an intramolecular [SH···ON-Fe] interaction. As suggested by computational results (density functional theory), the NO stretching frequency (νNO) is sensitive to the intramolecular interaction between the pendant ligand and the iron-bound NO, and a shift of νNO from 1833 (1) to 1823 cm-1 (A) is observed experimentally. Subsequent photolysis of the intermediate A results in HNO production and a thiyl group that then coordinates to the Fe center for the formation of [Fe(TMSPS2)2] (4). In contrast with the common acid-base coupling pathway, the HNO is not voluntarily yielded from 1 but rather is generated by the photopromoted pathway. The photogenerated HNO can further react with [MnIII(TMSPS3)(DABCO)] (TMSPS3H3 = (2,2′2′′-trimercapto-3,3′,3′′-tris(trimethylsilyl)triphenylphosphine; DABCO = 1,4-diazabicyclo[2.2.2]octane) in organic media to yield anionic [Mn(NO)(TMSPS3)]- (5-) with a {MnNO}6 electronic configuration, whereas [MnIII(TMSPS3)(DABCO)] reacts with NO gas for the formation of a {MnNO}5 species, [Mn(NO)(TMSPS3)] (6). Effective differentiation of the formation of HNO from complex 1 with the pendant SH versus NO from 2 with the pendant SMe is achieved by the employment of [MnIII(TMSPS3)(DABCO)].
• Chiang, Chuan-Kuei,Chu, Kai-Ti,Lin, Chia-Chin,Xie, Shi-Rou,Liu, Yu-Chiao,Demeshko, Serhiy,Lee, Gene-Hsiang,Meyer, Franc,Tsai, Ming-Li,Chiang, Ming-Hsi,Lee, Chien-Ming

• p. 8649 - 8661

  (2020/05/13)
• 

• Functional Models for the Mono- And Dinitrosyl Intermediates of FNORs: Semireduction versus Superreduction of NO
• The reduction of NO to N2O by flavodiiron nitric oxide reductases (FNORs) is related to the disruption of the defense mechanism in mammals against invading pathogens. The proposed mechanism for this catalytic reaction involves both nonheme mono- and dinitrosyl diiron(II) species as the key intermediates. Recently, we reported an initial account for NO reduction activity of an unprecedented mononitrosyl diiron(II) complex, [Fe2(N-Et-HPTB)(NO)(DMF)3](BF4)3 (1) (N-Et-HPTB is the anion of N,N,N′,N′-tetrakis(2-(l-ethylbenzimidazolyl))-2-hydroxy-1,3-diaminopropane; DMF = dimethylformamide) with [FeII{FeNO}7] formulation [ Jana et al. J. Am. Chem. Soc. 2017, 139, 14380 ]. Here we report the full account for the selective synthesis, characterization, and reactivity of FNOR model complexes, which include a dinitrosyl diiron(II) complex, [Fe2(N-Et-HPTB)(NO)2(DMF)2](BF4)3 (2) with [{FeNO}7]2 formulation and a related, mixed-valent diiron(II, III) complex, [Fe2(N-Et-HPTB)(OH)(DMF)3](BF4)3 (3). Importantly, whereas complex 2 is able to produce 89% of N2O via a semireduced mechanism (1 equiv of CoCp2 per dimer = 50% of NO reduced), complex 1, under the same conditions (0.5 equiv of CoCp2 per dimer = 50% of NO reduced), generates only ～50% of N2O. The mononitrosyl complex therefore requires superreduction for quantitative N2O generation, which constitutes an interesting dichotomy between 1 and 2. Reaction products obtained after N2O generation by 2 using 1 and 2 equiv of reductant were characterized by molecular structure determination and electron paramagnetic resonance spectroscopy. Despite several available literature reports on N2O generation by diiron complexes, this is the first case where the end products from these reactions could be characterized unambiguously, which clarifies a number of tantalizing observations about the nature of these products in the literature.
• Jana, Manish,White, Corey J.,Pal, Nabhendu,Demeshko, Serhiy,Cordes, Claudia,Meyer, Franc,Lehnert, Nicolai,Majumdar, Amit

• p. 6600 - 6616

  (2020/04/30)
• 

• Light-Intensity-Responsive Changes of Products in Photocatalytic Reduction of Nitrous Acid on a Cu-Doped Covalent Triazine Framework–TiO2 Hybrid
• In the design of solar-energy conversion electrochemical systems, it is important to consider that natural sunlight fluctuates. By taking nitrous acid photoreduction as an example, this study has shown that the reaction pathway, and hence the reaction products, dynamically respond to variations in light intensity. Under irradiation, the photooxidation of methanol (as sacrificial agent) on TiO2 and the reduction of HNO2 on a Cu-modified covalent triazine framework (Cu-CTF) are electrically coupled, which leads to the photoreduction of HNO2 without an external bias. The major product of the reaction changes from N2O to NH4+ with an increase in the light intensity. The operating potential also shifts negatively (or positively) when the light intensity is increased (or decreased). These results indicate that a change in the reaction pathway is triggered by a change in the operating potential of the Cu-CTF catalyst under varying light intensity. Such a light-intensity-dependent change in the reaction pathway is particularly important in systems that use photoresponsive electrodes and where multiple products can be obtained, such as the solar-driven reduction of carbon dioxide and nitrogen oxides.
• Kamiya, Kazuhide,Sugimoto, Rino,Tatebe, Tomomi,Harada, Takashi,Nakanishi, Shuji

• p. 3462 - 3468

  (2020/06/01)
• 

• Three-dimensional nickel foam templated MgCo2O4 nanowires as an efficient catalyst for the thermal decomposition of ammonium perchlorate
• Spinel–type oxides MgCo2O4 and Co3O4 nanowires (NWs) were successfully prepared using nickel foam (NF) as a template. The catalytic performance of MgCo2O4 NWs on the thermal decomposition of ammonium perchlorate (AP) was investigated by differential scanning calorimetry (DSC) and simultaneous thermogravimetry–mass spectrometry (TG/MS) techniques. In the presence of MgCo2O4 NWs, the process of the high temperature decomposition (HTD) and the low temperature decomposition (LTD) of AP was combined to one with a peak temperature of 277.35 ?°C. Meanwhile, the apparent activation energy decreased from 139.05 to 123.61 ?kJ·mol?1 on the basis of thermal analysis kinetics. This was attributed to the synergistic effect between the metals of this ternary metal oxide and the larger specific surface area of MgCo2O4 NWs. Therefore, MgCo2O4 with nanowires morphology holds a promise to catalyze energetic components.
• Guo, Zhaoqi,Li, Cuicui,Li, Jiachen,Li, Yaoyao,Ma, Haixia,Zhang, Ting

• (2020/06/05)
• 

• Lewis Acid Coordination Redirects S-Nitrosothiol Signaling Output
• S-Nitrosothiols (RSNOs) serve as air-stable reservoirs for nitric oxide in biology. While copper enzymes promote NO release from RSNOs by serving as Lewis acids for intramolecular electron-transfer, redox-innocent Lewis acids separate these two functions
• Bakhoda, Abolghasem,Bertke, Jeffery A.,Hosseininasab, Valiallah,McQuilken, Alison C.,Timerghazin, Qadir K.,Warren, Timothy H.

• p. 10854 - 10858

  (2020/04/27)
• 

• Complete denitrification of nitrate and nitrite to N2gas by samarium(ii) iodide
• The reduction of nitrogen oxides (NxOyn?) to dinitrogen gas by samarium(ii) iodide is reported. The polyoxoanions nitrate (NO3?) and nitrite (NO2?), as well as nitrous oxide (Ns
• Marks, Walker R.,Baumgardner, Douglas F.,Reinheimer, Eric W.,Gilbertson, John D.
• supporting information

  p. 11441 - 11444

  (2020/10/12)
• 

• Investigation of Fe?Ni Mixed-Oxide Catalysts for the Reduction of NO by CO: Physicochemical Properties and Catalytic Performance
• A series of Fe?Ni mixed-oxide catalysts were synthesized by using the sol–gel method for the reduction of NO by CO. These Fe?Ni mixed-oxide catalysts exhibited tremendously enhanced catalytic performance compared to monometallic catalysts that were prepared by using the same method. The effects of Fe/Ni molar ratio and calcination temperature on the catalytic activity were examined and the physicochemical properties of the catalysts were characterized by using XRD, Raman spectroscopy, N2-adsorption/-desorption isotherms, temperature-programmed reduction with hydrogen (H2-TPR), temperature-programmed desorption of nitric oxide (NO-TPD), and X-ray photoelectron spectroscopy (XPS). The results indicated that the reduction behavior, surface oxygen species, and surface chemical valence states of iron and nickel in the catalysts were the key factors in the NO elimination. Fe0.5Ni0.5Ox that was calcined at 250 °C exhibited excellent catalytic activity of 100 % NO conversion at 130 °C and a lifetime of more than 40 hours. A plausible mechanism for the reduction of NO by CO over the Fe?Ni mixed-oxide catalysts is proposed, based on XPS and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analyses.
• Du, Xuexun,Yao, Tian-Liang,Wei, Qinglian,Zhang, Hao,Huang, Yongmin

• p. 2966 - 2978

  (2019/08/07)
• 

• A heterogeneous single Cu catalyst of Cu atoms confined in the spinel lattice of MgAl2O4 with good catalytic activity and stability for NO reduction by CO
• A heterogeneous single Cu catalyst of Cu atoms confined in the spinel lattice of MgAl2O4 (Cu1-MgAl2O4) was prepared by a facile method. Cu1-MgAl2O4 exhibits catalytic activity for NO reduction by CO that is much higher than that of 1.0 wt% Pt/CeO2. Moreover, Cu1-MgAl2O4 exhibits good catalytic stability at high reaction temperatures up to 700 °C during the long-term durability tests. The good stability is attributed to the confinement effect of the stable spinel lattice of Cu1-MgAl2O4 that stabilizes the confined Cu atoms. The high catalytic activity is attributed to the fact that oxygen bonding to Cu atoms of Cu1-MgAl2O4 participates in the oxidation of adsorbed CO with low activation energy, and the adsorption of NO on the resultant oxygen vacancies leads to the formation of N2O with low activation energy, which subsequently decomposes to N2.
• Wu, Jichun,Li, Yuanzhi,Yang, Yi,Zhang, Qian,Yun, Li,Wu, Shaowen,Zhou, Chongyang,Jiang, Zhongkai,Zhao, Xiujian

• p. 7202 - 7212

  (2019/03/26)
• 

• VOX supported on TiO2-Ce0.9Zr0.1O2 core-shell structure catalyst for NH3-SCR of NO
• 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

• p. 30340 - 30349

  (2019/10/04)
• 

• Hydroxylamine Oxidation on Polycrystalline Gold Electrodes in Aqueous Electrolytes: Quantitative On-Line Mass Spectrometry under Forced Convection
• Herein, a method is presented that allows quantitative determination of faradaic efficiencies for dinitrogen (N2) generation during the electrochemical oxidation of hydroxylamine (NH2OH), (Formula presented.), on a polycrystalline gold Au(poly) disk electrode in aqueous electrolytes over a wide pH range. This tactic involves the use of an impinging jet electrolyte configuration incorporating a gas porous ring connected in turn to a mass spectrometer. The actual amount of N2 generated at the Au(poly) disk was assayed using the oxidation of hydrazine (N2H4) in aqueous phosphate buffer (pH 7). This redox process yields N2 as the only product, allowing a direct correlation to be established between the changes in the partial pressures of N2 and the current flowing through the disk electrode. An analysis of the data collected revealed a strong dependence of (Formula presented.) both on pH and the applied potential. Although values of (Formula presented.) as high as 20 to 30 % were found in acid and neutral media over a narrow potential region, those in alkaline solution were far smaller in the entire potential range examined.
• Pozniak, Boguslaw,Treufeld, Imre,Scherson, Daniel

• p. 3128 - 3133

  (2019/11/03)
• 

• Nitrosyl Linkage Isomers: NO Coupling to N2O at a Mononuclear Site
• Linkage isomers of reduced metal-nitrosyl complexes serve as key species in nitric oxide (NO) reduction at monometallic sites to produce nitrous oxide (N2O), a potent greenhouse gas. While factors leading to extremely rare side-on nitrosyls are unclear, we describe a pair of nickel-nitrosyl linkage isomers through controlled tuning of noncovalent interactions between the nitrosyl ligands and differently encapsulated potassium cations. Furthermore, these reduced metal-nitrosyl species with N-centered spin density undergo radical coupling with free NO and provide a N-N coupled cis-hyponitrite intermediate whose protonation triggers the release of N2O. This report outlines a stepwise molecular mechanism of NO reduction to form N2O at a mononuclear metal site that provides insight into the related biological reduction of NO to N2O.
• Kundu, Subrata,Phu, Phan N.,Ghosh, Pokhraj,Kozimor, Stosh A.,Bertke, Jeffery A.,Stieber, S. Chantal E.,Warren, Timothy H.
• supporting information

  p. 1415 - 1419

  (2019/01/26)
• 

• Improvement of low-temperature catalytic activity over hierarchical Fe-Beta catalysts for selective catalytic reduction of NOx with NH3
• 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
• supporting information

  p. 867 - 870

  (2019/03/23)
• 

• Kinetics of Thermal Decomposition of 3,7-Dinitro-1,3,5,7-tetraazabicyclo[3.3.1]nonane
• The kinetics of thermal decomposition of 3,7-dinitro-1,3,5,7-tetraazabicyclo[3.3.1]nonane has been studied in solid phase and in solution. The mechanism, kinetic parameters of decomposition, and activation parameters of the rate-limiting step have been determined.
• Kruglyakova,Stepanov,Kekin, Yu. V.,Pekhotin

• p. 194 - 198

  (2019/04/13)
• 

• The Role of Alkali Metal in α-MnO2 Catalyzed Ammonia-Selective Catalysis
• The unexpected phenomenon and mechanism of the alkali metal involved NH3 selective catalysis are reported. Incorporation of K+ (4.22 wt %) in the tunnels of α-MnO2 greatly improved its activity at low temperature (50–200 °
• Hao, Zhifei,Shen, Zhurui,Li, Yi,Wang, Haitao,Zheng, Lirong,Wang, Ruihua,Liu, Guoquan,Zhan, Sihui
• supporting information

  p. 6351 - 6356

  (2019/04/08)
• 

• Nitrosonium reactivity of (NHC)Copper(I) sulfide complexes
• This study examines the reactivity of a series of copper(I) sulfide complexes stabilized by the expanded-ring N-heterocyclic carbene (NHC) 1,3-bis(2,6-diisopropylphenyl)-4,5,6,7-tetrahydro-1,3-diazepin-2-ylidene (7Dipp) toward the nitrosonium ion (NO+). 7Dipp is shown to support neutral sulfide- and disulfide-bridged dicopper(I) complexes, as well as mononuclear copper(I) hydrosulfide. The addition of NO+ to each of these results in the formation of NHC-supported copper(I) cations and elemental sulfur. Reduction of copper(I) to copper(0) is observed upon reaction of NO+ with dicopper(I) sulfide or disulfide, whereas ammonium ion formation is observed upon reaction of copper(I) hydrosulfide with NO+. Ammonium ion formation is likewise observed upon reaction of NO+ with (7Dipp)copper(I) hydride.
• Jordan, Abraham J.,Walde, Rebecca K.,Schultz, Kelly M.,Bacsa, John,Sadighi, Joseph P.
• supporting information

  p. 9592 - 9596

  (2019/08/22)
• 

• Sulfation effect of Ce/TiO2 catalyst for the selective catalytic reduction of NO: X with NH3: Mechanism and kinetic studies
• Ceria-based catalysts are competitive substitutes for the commercial SCR catalysts due to their high SCR activity and excellent redox performance. For a better understanding of the SO2 poisoning mechanism over ceria-based catalysts, the sulfation effect of the Ce/TiO2 catalyst on the SCR activity over a wide reaction temperature range was systematically studied via comprehensive characterizations, in situ DRIFT studies and kinetic studies. The results demonstrated that the NO conversion at 150 °C is significantly inhibited by the formation of cerium sulfites/sulfates due to the inhibited redox properties and excessive adsorption of NH3, which restrict the dissociation of NH3 to NH2, resulting in a much lower reaction rate of E-R reaction over the sulfated Ce/TiO2 catalyst. With the increase in the reaction temperature, the reaction rate of the E-R reaction significantly increased due to the improved redox properties and weakened adsorption of NH3. Moreover, the rate of the C-O reaction over the sulfated Ce/TiO2 catalysts is obviously lower than that of the fresh Ce/TiO2 catalyst. The promotion of NO conversion over the sulfated catalyst at 330 °C is attributed to both the increase in the reaction rate of E-R reaction and the inhibition of the C-O reaction.
• Zhang, Wenjie,Liu, Guofu,Jiang, Jie,Tan, Yuchen,Wang, Qi,Gong, Chenghong,Shen, Dekui,Wu, Chunfei

• p. 32110 - 32120

  (2019/10/22)
• 

• Probing the Reaction Mechanisms Involved in the Decomposition of Solid 1,3,5-Trinitro-1,3,5-triazinane by Energetic Electrons
• 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.

• p. 9479 - 9497

  (2019/11/11)
• 

• Not Limited to Iron: A Cobalt Heme–NO Model Facilitates N–N Coupling with External NO in the Presence of a Lewis Acid to Generate N2O
• Some bacterial heme proteins catalyze the coupling of two NO molecules to generate N2O. We previously reported that a heme Fe–NO model engages in this N?N bond-forming reaction with NO. We now demonstrate that (OEP)CoII(NO) similarly reacts with 1 equiv of NO in the presence of the Lewis acids BX3 (X=F, C6F5) to generate N2O. DFT calculations support retention of the CoII oxidation state for the experimentally observed adduct (OEP)CoII(NO?BF3), the presumed hyponitrite intermediate (P.+)CoII(ONNO?BF3), and the porphyrin π-radical cation by-product of this reaction, and that the π-radical cation formation likely occurs at the hyponitrite stage. In contrast, the Fe analogue undergoes a ferrous-to-ferric oxidation state conversion during this reaction. Our work shows that cobalt hemes are chemically competent to engage in the NO-to-N2O conversion reaction.
• Abucayon, Erwin G.,Khade, Rahul L.,Powell, Douglas R.,Zhang, Yong,Richter-Addo, George B.
• supporting information

  p. 18598 - 18603

  (2019/11/14)
• 

• Selective Electrocatalytic Reduction of Nitrite to Dinitrogen Based on Decoupled Proton-Electron Transfer
• The development of denitrification catalysts which can reduce nitrate and nitrite to dinitrogen is critical for sustaining the nitrogen cycle. However, regulating the selectivity has proven to be a challenge, due to the difficulty of controlling complex multielectron/proton reactions. Here we report that utilizing sequential proton-electron transfer (SPET) pathways is a viable strategy to enhance the selectivity of electrochemical reactions. The selectivity of an oxo-molybdenum sulfide electrocatalyst toward nitrite reduction to dinitrogen exhibited a volcano-type pH dependence with a maximum at pH 5. The pH-dependent formation of the intermediate species (distorted Mo(V) oxo species) identified using operando electron paramagnetic resonance (EPR) and Raman spectroscopy was in accord with a mathematical prediction that the pKa of the reaction intermediates determines the pH-dependence of the SPET-derived product. By utilizing this acute pH dependence, we achieved a Faradaic efficiency of 13.5% for nitrite reduction to dinitrogen, which is the highest value reported to date under neutral conditions.
• He, Daoping,Li, Yamei,Ooka, Hideshi,Go, Yoo Kyung,Jin, Fangming,Kim, Sun Hee,Nakamura, Ryuhei
• supporting information

  p. 2012 - 2015

  (2018/02/19)
• 

• A study on the NH3-SCR performance and reaction mechanism of a cost-effective and environment-friendly black TiO2 catalyst
• In this paper, black TiO2 without adding active components was developed for NH3-SCR-DeNOx. The catalytic activity tests showed that the NO removal efficiency of black TiO2 was always greater than 90% at 330-390 °C, which almost reached that of the commercial NH3-SCR-DeNOx catalyst. XRD, UV-vis, TG, EPR, XPS, H2-TPR, DFT and NH3-TPD analyses were carried out to study the structure-effectiveness relationship. We found that a large number of oxygen vacancies were formed over the black TiO2 surface. It was not only promoted the adsorption of NH3via direct (oxygen vacancies as Lewis acid sites for NH3 adsorption) and indirect (oxygen vacancies promote the formation of surface hydroxyl groups, which are Br?nsted acid sites for NH3 adsorption) forms, but also improved the redox properties by promoting the reduction of Ti4+ to Ti3+. These changes lead to the superior catalytic activity of black TiO2 for NH3-SCR-DeNOx. Additionally, an in situ DRIFT study demonstrated that the NH3-SCR-DeNOx reaction over black TiO2 occurred via the Eley-Rideal (E-R) mechanism. Finally, the catalytic stability and resistance to H2O and SO2 of the black TiO2 catalyst were studied, and it showed good performances. This study offered new and important insights into the understanding of the role of oxygen vacancies in determining the physical and chemical properties of catalysts.
• Zeng, Yiqing,Wang, Yanan,Zhang, Shule,Zhong, Qin

• p. 22744 - 22752

  (2018/09/25)
• 

• Selective Catalytic Reduction of NO by NH3 over MoO3 Promoted Fe2O3 Catalyst
• A series of MoO3 doped Fe2O3 catalysts prepared by the co-precipitation method were investigated in the selective catalytic reduction of NO by NH3 (NH3-SCR). The catalysts displayed excellent catalytic activity from 225 to 400°C and high tolerance to SO2/H2O poisoning at 300°C. To characterize the catalysts the N2-BET, XRD, Raman, NO-TPD, NH3-TPD and in situ DRIFTS were carried out. It was found that the main reason explaining a high NH3-SCR performance might be the synergistic effect between Fe and Mo species in the catalyst that could enhance the dispersion of Fe2O3 and increase NH3 adsorption on the catalyst surface.
• Li, X.,Wang, J.,Xu, Zh.,Zhao, W.

• p. 628 - 634

  (2018/10/02)
• 

• Effects of the Fe/Ce ratio on the activity of CuO/CeO2-Fe2O3 catalysts for NO reduction by CO
• Copper catalysts on Fe-loaded ceria were studied for NO reduction by CO. Catalysts with different Fe/Ce molar ratios (Cu/C1Fx) were synthesized by a wet impregnation method. Catalysts were characterized by XRD, BET, Raman, EPR, H2-TPR and in situ DRIFTS. CuO was highly dispersed on the support surface to form active species. Ceria modification by incorporation of a lower amount of Fe3+ was beneficial for NO conversion and N2 selectivity as compared with pure ceria and iron-rich ones, which resulted from the strong interaction between ceria and iron. Cu/C1F1 showed better catalytic performance at 100-200 °C, whereas Cu/C1F0.5 gave higher N2 selectivity than the other samples. In situ DRIFTS suggested that iron-rich catalysts ensured inhibition of NO reduction by increasing the partial pressure of NO. Two mechanisms could explain formation of the NCO intermediate and N2O intermediate over ceria-rich catalysts. With an increase in the Fe/Ce molar ratio and temperature, a mechanism in which N2O is the intermediate dominates the reaction, whereas a process in which NCO species are produced as intermediates results in their gradual disappearance.
• Zhang, Xingyu,Cheng, Xingxing,Ma, Chunyuan,Wang, Zhiqiang

• p. 3336 - 3345

  (2018/07/13)
• 

• Non-Heme Diiron Model Complexes Can Mediate Direct NO Reduction: Mechanistic Insight into Flavodiiron NO Reductases
• Flavodiiron nitric oxide reductases (FNORs), a common enzyme family found in various types of pathogenic bacteria, are capable of reducing nitric oxide (NO) to nitrous oxide (N2O) as a protective detoxification mechanism. Utilization of FNORs in pathogenic bacteria helps them survive and proliferate in the human body, thus causing chronic infections. In this paper, we present a new diiron model complex, [Fe2((Py2PhO2)MP)(OPr)2](OTf), with bridging propionate ligands (OPr-) that is capable of directly reducing NO to N2O in quantitative yield without the need to (super)reduce the complex. We first prepared the diferric precursor and characterized it by UV-vis, IR, NMR and M?ssbauer spectroscopies, cyclic voltammetry, and mass spectrometry. This complex can then conveniently be reduced to the diferrous complex using CoCp2. Even though this diferrous complex is highly reactive, we have successfully isolated and characterized this species using X-ray crystallography and various spectroscopic techniques. Most importantly, upon reacting this diferrous complex with NO gas, we observe quantitative formation of N2O via IR gas headspace analysis, the first demonstration of direct NO reduction by a non-heme diiron model complex. This finding directly supports recent mechanistic proposals for FNORs.
• Dong, Hai T.,White, Corey J.,Zhang, Bo,Krebs, Carsten,Lehnert, Nicolai
• supporting information

  p. 13429 - 13440

  (2018/10/20)
• 

• Cerium oxide based active catalyst for hydroxylammonium nitrate (HAN) fueled monopropellant thrusters
• 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

• p. 22293 - 22302

  (2018/06/29)
• 

• The Semireduced Mechanism for Nitric Oxide Reduction by Non-Heme Diiron Complexes: Modeling Flavodiiron Nitric Oxide Reductases
• Flavodiiron nitric oxide reductases (FNORs) are a subclass of flavodiiron proteins (FDPs) capable of preferential binding and subsequent reduction of NO to N2O. FNORs are found in certain pathogenic bacteria, equipping them with resistance to nitrosative stress, generated as a part of the immune defense in humans, and allowing them to proliferate. Here, we report the spectroscopic characterization and detailed reactivity studies of the diiron dinitrosyl model complex [Fe2(BPMP)(OPr)(NO)2](OTf)2 for the FNOR active site that is capable of reducing NO to N2O [Zheng et al., J. Am. Chem. Soc. 2013, 135, 4902-4905]. Using UV-vis spectroscopy, cyclic voltammetry, and spectro-electrochemistry, we show that one reductive equivalent is in fact sufficient for the quantitative generation of N2O, following a semireduced reaction mechanism. This reaction is very efficient and produces N2O with a first-order rate constant k > 102 s-1. Further isotope labeling studies confirm an intramolecular N-N coupling mechanism, consistent with the rapid time scale of the reduction and a very low barrier for N-N bond formation. Accordingly, the reaction proceeds at -80 °C, allowing for the direct observation of the mixed-valent product of the reaction. At higher temperatures, the initial reaction product is unstable and decays, ultimately generating the diferrous complex [Fe2(BPMP)(OPr)2](OTf) and an unidentified ferric product. These results combined offer deep insight into the mechanism of NO reduction by the relevant model complex [Fe2(BPMP)(OPr)(NO)2]2+ and provide direct evidence that the semireduced mechanism would constitute a highly efficient pathway to accomplish NO reduction to N2O in FNORs and in synthetic catalysts.
• White, Corey J.,Speelman, Amy L.,Kupper, Claudia,Demeshko, Serhiy,Meyer, Franc,Shanahan, James P.,Alp, E. Ercan,Hu, Michael,Zhao, Jiyong,Lehnert, Nicolai
• supporting information

  p. 2562 - 2574

  (2018/02/28)
• 

• Lewis Acid Activation of the Ferrous Heme-NO Fragment toward the N-N Coupling Reaction with NO to Generate N2O
• Bacterial NO reductase (bacNOR) enzymes utilize a heme/non-heme active site to couple two NO molecules to N2O. We show that BF3 coordination to the nitrosyl O-atom in (OEP)Fe(NO) activates it toward N-N bond formation with NO to generate N2O. 15N-isotopic labeling reveals a reversible nitrosyl exchange reaction and follow-up N-O bond cleavage in the N2O formation step. Other Lewis acids (B(C6F5)3 and K+) also promote the NO coupling reaction with (OEP)Fe(NO). These results, complemented by DFT calculations, provide experimental support for the cis:b3 pathway in bacNOR.
• Abucayon, Erwin G.,Khade, Rahul L.,Powell, Douglas R.,Zhang, Yong,Richter-Addo, George B.
• supporting information

  p. 4204 - 4207

  (2018/04/05)
• 

• Mechanochemical fabrication and properties of CL-20/RDX nano co/mixed crystals
• 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

• p. 34126 - 34135

  (2018/10/17)
•