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Peroxynitrous acid and peroxynitrite anion have been studied using pulse radiolysis of nitrite and nitrate solutions.The formation rate constant determined to be k(OH + NO2) = (4.5 +/- 1.0) * 109 M-1 s-1, and the rate constant for the OH radical reaction with nitrite is determined to be k(OH +NO2-) = (6.0 +/- 1.0) * 109 M-1 s-1.In nitrate solutions, the competing reaction between OH and NO32- is found to have a rate constant of k(OH + NO32- = (3.0 +/- 1.0) * 109 M-1 s-1.The intermediate species in the nitrate system, NO32-, HNO3-, and H2NO3, decay into NO2 according to the first-order rate constants: (5.6 +/ - 0.5) * 104, (2.0 +/- 0.5) * 105, and (7.0 +/- 2.0) * 105 s-1, respectively.The rate constants k(H + NO3-) = (1.0 +/- 0.3) * 107 M-1 s-1 and k(H + NO2) = (1.0 +/- 0.2) * 1010 M-1 s-1 were also determined.The pKa of NOOH is found to be 6.5 +/- 0.1 by absorption measurements, and the maximum extinction coefficient at 240 nm is ε240(ONOOH) = 770 +/- 50 M-1 cm-1.The decay of peroxynitrous acid is detrmined to proceed through the first-order isomerization of ONOOH to HNO3 according to the rate equation kobs = kiso/(1 + Ka/+>) with rate constants kiso = 1.0 +/- 0.2 s-1 and Ka = (1.0 +/- 0.3) * 10-7.A comparison of all available literature values for the pKa and the decay rate is reported.

The visible light active catalysts, PtOx-doped TiO2 (PtOx-TiO2) and PtOx-loaded TiO2 (PtOx/TiO2), were successfully synthesized by the acid-catalyzed sol-gel process and the impregnation method. Pt(NH3)4(NO3)2 or H2Pt(OH)6 was employed as the PtOx precursor. By comparing the results of De-NOx, the modified photocatalysts exhibited a higher visible-light-responsive activity, and a lower NO2 selectivity than the unmodified ones. The FE-SEM images suggested that the particle size was unchanged after modification. The XRD patterns showed that the crystal structure still remained as anatase phase. Nitrogen adsorption revealed no significant change in surface areas for all samples. The UV-vis spectra indicated that PtOx promoted the absorption of visible light. Furthermore, the XPS spectra evidenced that the mixed valence states of PtO-PtO2 coexisted on the surface of TiO2. The adding of PtOx on TiO2 not only promoted the visible-light-responsive activity of converting NO to NO2 but also increased the consecutive reaction rate of NO2 to NO3-.

Gas - liquid scattering experiments are used to measure the fraction of N2O5 molecules that are converted to HNO3 after colliding with 72 wt % H2SO4 containing 1-hexanol or 1-butanol at 216 K. These alcohols segregate to the surface of the acid, with saturation coverages estimated to be 60% of a close-packed monolayer for 1-hexanol and 44% of a close-packed monolayer for 1-butanol. We find that the alkyl films reduce the conversion of N2O5 to HNO 3 from 0.15 on bare acid to 0.06 on the hexyl-coated acid and to 0.10 on the butyl-coated acid. The entry of HC1 and HBr, however, is enhanced by the hexanol and butanol films. The hydrolysis of N2O5 may be inhibited because the alkyl chains restrict the transport of this large molecule and because the alcohol OH groups dilute the surface region, suppressing reaction between N2O5 and near-interfacial H 3O+ or H2O. In contrast, the interfacial alcohol OH groups provide additional binding sites for HC1 and HBr and help initiate ionization. These and previous scattering experiments indicate that short-chain alcohol surfactants impede or enhance sulfuric acid-mediated reactions in ways that depend on the chain length, liquid phase acidity, and nature of the gas molecule.

The photocatalytic decomposition of nitrogen monoxide (NO) was achieved for the first time using Si-based nanomaterials. Nanocomposite powders composed of Si nanoflakes and metallic particles (Ni and Ni3Si) were synthesized using a simple one-pot reaction of layered CaSi2 and NiCl2. The synthesized nanocomposites have a wide optical absorption band from the visible to the ultraviolet. Under the assumption of a direct transition, the photoabsorption behavior is well described and an absorption edge of ca. 1.8 eV is indicated. Conventional Si and SiO powders with indirect absorption edges of 1.1 and 1.4 eV, respectively, exhibit considerably low photocatalytic activities for NO decomposition. In contrast, the synthesized nanocomposites exhibited photocatalytic activities under irradiation with light at wavelengths >290 nm (4.28 eV). The photocatalytic activities of the nanocomposites were confirmed to be constant and did not degrade with the light irradiation time.

The reaction HCl + ClONO2 -> Cl2 + HNO3 has been studied by FTIR spectroscopy and by a static wallless UV absorption technique.An upper limit to the homogeneous bimolecular rate constant of 1E-19 cm3 molecule-1 s-1 was established, making the reaction unimportant in the stratosphere.

Comparison of ZnO nanoparticles and its nano-crystalline particles on the photocatalytic degradation of methylene blue was investigated. ZnO nanoparticles and its nano-crystalline particles were synthesized from sprayed droplets of an aqueous zinc nitrate solution by flame spray pyrolysis and spray pyrolysis assisted with an electrical furnace, respectively. ZnO nanoparticles of 20 nm in average diameter and ZnO nano-crystalline particles of 20 nm in the grain size were prepared to compare the photocatalytic activity. The photocatalytic activity of those ZnO particles was evaluated by measuring the degradation of methylene blue in water under the illumination of ultraviolet rays. Effect of the particle morphology, initial concentration of methylene blue, and photocatalyst loading on the degradation of the methylene blue was investigated under the illumination of ultraviolet rays. The photocatalytic degradation capacity of the ZnO nanoparticles was higher than that of the ZnO nano-crystalline particles. The efficiency of photocatalytic degradation of methylene blue increased with increase in photocatalyst loading and decrease in initial concentration regardless of particle morphology.

The influence of water vapor on the production of nitric acid in the gas-phase HO2 + NO reaction was determined at 298 K and 200 Torr using a high-pressure turbulent flow reactor coupled with a chemical ionization mass spectrometer. The yield o

The interaction of nitric acid with dinitrogen, carbon monoxide and nitric oxide has been investigated by IR spectroscopy in low-temperature argon matrices.The spectra show that under these conditions N2 interacts strongly and specifically with HNO3, forming several distinct 1 : 1 complexes.The probable structures of these complexes are discussed.CO behaves in a similar manner to N2, forming complexes of the type -ONO2; weak bands due to a -ONO2 complex were generated by photolysis.For NO, complexes of HNO3 were observed with both monomeric and dimeric NO.The strength of interaction with HNO3 was found to increase in the order N2 NO CO.

Microperoxidase-11 (MP11) is an undecapeptide derived from horse heart cytochrome c offering the possibility to study the reactivity of the heme group relatively unshielded by the protein. Here, the peroxynitrite isomerization to NO3-/sup

High-level electronic structure calculations were used to study the mechanism of the reaction of ClONO2 with HCl in neutral water clusters containing one to five solvating water molecules. For the reaction between molecular HCl and ClONO2, the barrier decreases from 42 kcal mol-1 (uncatalyzed) to essentially zero when catalyzed by only two water molecules, where the reaction products involve Cl2 and HONO2. The calculations thus predict that the gas-phase reaction may be important in the stratospheric reactivation of ClONO2. The reaction between ClONO2 and solvated H3O+Cl-, as on the polar stratospheric cloud (PSC) surface, was investigated with clusters involving up to seven water molecules. The ice-catalyzed reaction involves an ionic mechanism whereby charge transfer to ClONO2 from the attacking nucleophile leads to significant ionization along the Cl-ONO2 bond. The effect of the size of the first solvation shell of Cl- is addressed by our calculations. In a cluster containing three waters and a five-water cluster structurally related to hexagonal ice, ClONO2 reacts spontaneously with HCl to yield Cl2/HONO2 in the three-water reaction and Cl2/H3O+-NO3- in the five-water-catalyzed reaction. The calculations thus predict that the reaction of ClONO2 with HCl on PSC ice aerosols can proceed spontaneously via an ionic pathway.

The hydrolysis of CIONO2 takes place very readily on a variety of laboratory surfaces and may also occur catalytically on particulate surfaces in the stratosphere. The reaction can be considered as an oxide exchange between two X-O-Y molecules with X and Y = H, C1, or NO2. Two other reactions in this class which might occur in the stratosphere are HOCl plus HOCl, and HOCl plus ClONO2. Each of these three is approximately thermoneutral and should be accompanied by the reverse reaction with a comparable reaction rate constant. Current atmospheric models have not explained the very large ozone depletions which have taken place during Antarctic spring in the past decade. The chemical reactions included in these models may need to include heterogeneous catalysis of one or more of these oxide exchange reactions.

The kinetics of the forward and backward processes of the reaction NO3- + 2 Br- + 3 H+ Br2 + HNO2 + H2O have been studied.The overall process is true dynamic equilibrium.The same equilibrium position can be reached fro

The heterogeneous reactions of N2O5 with HC1 and HBr on ice have been studied in the temperature range 180 to 200 K using a Knudsen flow reactor. The uptake of N2O5 on ice in the presence of HBr was found to be strongly dependent on :he HBr concentration. For the highest HBr concentrations used a maximum uptake coefficient of N2O5 of 7 = 0.11 has been determined. We observed Br2 and MONO in 80% yield as products with respect to N2O5 taken up. The uptake coefficient of N2O5 on ice in the presence of HC1 was found to be 3.2-10-2 and increased with increasing HCl concentration. C1NO2 was detected as the sole reaction product with a maximum yield of 63% with respect to N2O5 consumed. Hydrolysis of N2O5 resulting in HNO3 was found to be competitive with the title reaction. For the case of the HBr reaction the branching ratio between Br2 and HONO formation, on the one hand, and hydrolysis of N2O5, on the other hand, has been determined. Mechanistic aspects of the heterogeneous reaction of N2O5 with HX have been discussed. WILEY-VCH Verlag GmbH, 1998.

The reactive uptake of ClONO2 onto 18O-labeled ice and onto organic liquids was measured in a cylindrical flow tube reactor using chemical ionization detection.The hydrolysis of ClONO2 on H2(18)O ice produced primarily H(18)OCl, indicating that the Cl-ONO2 bond is broken upon hydrolysis on ice.The loss of ClONO2 onto liquid organic surfaces (ethylene glycol, cyclohexanone, decanol, and tridecane) was found to be efficient (reaction probability > 0.06), and the product HNO3 was detected in the gas phase.This suggests that dissociation or ionization are not prerequisites for heterogeneous reactions of ClONO2.

Peroxynitrous acid, an inorganic toxin of biological importance, acts both as an oxidizing and a nitrating agent during its conversion to nitric acid. In discussions of the mechanism of this conversion, activation volumes have been invoked to distinguish between possible mechanisms, viz., homolysis of the O-O bond versus rotation via the N-O bond of peroxynitrous acid. A reinvestigation of the activation volume for the conversion of peroxynitrous acid to nitric acid by high-pressure stopped-flow spectrophotometry yielded an average value of 6.9 ± 0.9 cm3 mol-1 at 25 °C. Activation volumes currently cited in the literature for this process range from 6 to 10 cm3 mol-1 in the temperature range 18-25 °C. Such moderately positive values do not support a definite conclusion regarding the mechanism of the conversion.

The removal of nitrogen oxides (NOX) by semiconductor photocatalysis is an emerging technology in recent years. However, due to incomplete oxidation, the photocatalytic oxidation of NOX is usually accompanied by the generation of toxic intermediate by-products nitrogen dioxide (NO2), which causes secondary pollution and seriously limits its practical application. To tackle the issue, ZIF-67/CoOOH (ZIF-CH) cocatalyst was constructed via flexible strongly alkali oxidation treatment to modify g-C3N4, in which ZIF-67 was selected as a cobalt source of CoOOH. XRD, SEM, TEM and XPS demonstrated the ZIF-CH was successfully synthesized and anchored on CN. UV–vis, PL, EIS, transfer photocurrent response and DFT indicated that the introduction of ZIF-CH enlarged the response range to visible light, favored the separation and transfer of carriers and improved NO/NO2 adsorption ability. Consequently, the optimized ZIF-67/CoOOH/g-C3N4 (ZIF-CH/CN) exhibited a superior NO removal efficiency of 52.5% without any generation of toxic by-product NO2, and the cycling tests indicated the high stability of ZIF-CH/CN was obtained. In-suit DRIFTS and ESR were used to investigate the reaction pathway by comparing adsorption energy and detecting the reaction intermediates and products. More importantly, this result reveal that amount of hydroxyl radical (·OH) increased after introducing ZIF-CH cocatalyst, which promotes the deep oxidation of NO. These findings could supply a convenient and effective strategy for the design of a cocatalyst to enhance the photocatalytic oxidation performance of NO and inhibit the production of toxic by-product NO2.

A Knudsen cell flow reactor was used to study the heterogeneous reaction of N2O5 on laboratory ice surfaces and nitric acid trihydrate (NAT) surfaces representative of polar stratospheric clouds (PSCs).N2O5 was quantitatively converted to HNO3 on ice surfaces at 188 K.On initially pure ice surfaces, a gradual increase in the N2O5 uptake efficiency was observed up to a maximum value near 0.03.The slow rise in reactivity with time is consistent with an acid-catalyzed surface reaction.With increasing initial nitric acid concentrations, the maximum reactivity occurred more rapidly although the overall reactivity was depressed.The uptake efficiency for N2O5 on NAT at 188 K was found to be 0.015 +/- 0.006.

Argon matrix infrared spectra of sulphur dioxide complexes with nitric or nitrous acid indicate formation of hydrogen-bonded structures. The red shifts of the OH stretching modes are equal to ca. 179, 51 and 40 cm-1 in SO2-HNO3

The kinetics of the hydrolysis reaction of N2O5 on secondary organic aerosol (SOA) produced through the ozonolysis of α-pinene and on mixed ammonium bisulfate-SOA particles was investigated using an entrained aerosol flow tube coupled to a chemical ionization mass spectrometer. We report room temperature uptake coefficients, γ, on ammonium bisulfate and SOA particles at 50% relative humidity of 1.5 × 10-2 ± 1.5 × 10-3 and 1.5 × 10 -4 ± 2 × 10-5, respectively. For the mixed ammonium bisulfate-SOA particles, γ decreased from 2.6 × 10 -3 ± 4 × 10-4 to 3.0 × 10-4 ± 3 × 10-5 as the SOA mass fraction increased from 9 to 79, indicating a strong suppression in γ with the addition of organic material. There is an order-of-magnitude reduction in the uptake coefficient with the smallest amount of SOA material present and smaller additional reductions with increasing aerosol organic content. This newly coated organic layer may either decrease the mass accommodation coefficient of N 2O5 onto the particle or hinder the dissolution and diffusion of N2O5 into the remainder of the aerosol after it has been accommodated onto the surface. The former corresponds to a surface effect and the latter to bulk processes. The low value of the uptake coefficient on pure SOA particles will likely make N2O5 hydrolysis insignificant on such an aerosol, but atmospheric chemistry models need to account for the role that organics may play in suppressing the kinetics of this reaction on mixed organic-inorganic particles.

Ultraviolet resonance Raman spectroscopy (UVRR) is being developed for standoff trace explosives detection. To accomplish this, it is important to develop a deep understanding of the accompanying UV excited photochemistry of explosives, as well as the impact of reactions on the resulting photoproducts. In the work here we used 229 nm excited UVRR spectroscopy to monitor the photochemistry of pentaerythritol tetranitrate (PETN) in acetonitrile. We find that solutions of PETN in CD3CN photodegrade with a quantum yield of 0.08 ± 0.02, as measured by high performance liquid chromatography (HPLC). The initial step in the 229 nm UV photolysis of PETN in CD3CN is cleavage of an O-NO2 bond to form NO2. The accompanying photoproduct is pentaerythritol trinitrate (PETriN), (CH2ONO2)3CCH2OH formed by photolysis of a single O-NO2. The resulting UVRR spectra show a dominant photoproduct band at ～1308 cm-1, which derives from the symmetric stretch of dissolved NO2. This photoproduct NO2 is hydrolyzed by trace amounts of water, which downshifts this 1308 cm-1 NO2 Raman band due to the formation of molecular HNO3. The dissociation of HNO3 to NO3- in the presence of additional water results in an intense NO3- symmetric stretching UVRR band at 1044 cm-1.

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In order to eliminate the inhibition effect of the toxic nitric oxide (NO) in flue gas on microalgal growth and CO2fixation, NO was converted by a wet UV/H2O2method to produce nitrate (NO3-), which then be used as a nitrogen source for microalgae to improve its growth. The growth ability and biomass compositions of the microalgae cultivated with the produced NO3-from NO gas were similar to those of the microalgae cultivated with equivalent moles of commercial NaNO3. The NO3-concentration produced from NO increased with UV lamp power, H2O2, and NO concentrations, resulting in an improved microalgal growth. The concentration of NO3-from 500 ppm NO wet-oxidized by 6% (v/v) H2O2and 55 W UV light was up to 8.8 mM. When the produced nitrate was used as supplementary nitrogen source, the maximum growth productivity of Chlorella PY-ZU1 at 15% (v/v) CO2reached 1.18 g L-1per day (0.97 times higher than that cultivated with the standard medium). The peak fixation efficiency of 15% (v/v) CO2was 69.6% (1.13 times higher than that cultivated with the standard medium). This journal is

The uptake and decomposition of HNO3 on black carbon (soot) surfaces were investigated in order to evaluate the proposal that HNO3 decomposition on aircraft-generated soot aerosols may alter the NOx/NOy partitioning in the upper troposphere and lower stratosphere. The experimental measurements were performed by using a fast flow-tube reactor coupled to a quadrupole mass spectrometer. Black carbon samples used as surrogate material for aircraft soot in this study included Degussa FW2 (an amorphous carbon black comprising medium oxides), graphite, hexane soot, and kerosene soot. The measurements of uptake were performed by varying P(HNO3) in the range of 5 × 10-7 to 5 × 10-4 Torr at 220 and 295 K. The results are summarized as follows. Significant HNO3 decomposition was observed on FW2 at 295 K with P(HNO3) ≥ 1 × 10-4 Torr, while it did not occur at 220 K. Similar HNO3 decomposition behavior on graphite was also observed under the condition of P(HNO3) ≥ 10-4 Torr and T = 295 K, although the extent of the decomposition was much smaller than that on FW2. The decomposition of HNO3 on soot produced NO, NO2, H2O, oxidized soot surface, and some unidentified volatile products. To explain the observed decomposition behavior at higher partial pressures of HNO3, a bimolecular HNO3 decomposition mechanism on soot surfaces was proposed. However, HNO3 immediately decomposed on an FW2 surface at 503 K even at lower partial pressure (～10-6 Torr). On flame-deposited hexane and kerosene soot film, no HNO3 decomposition was observed up to P(HNO3) = 5 × 10-4 Torr. Moreover, the uptake and desorption of HNO3 were reversible at 295 K and irreversible at 220 K. Adsorbed HNO3 molecules on hexane soot film were saturated to a monolayer coverage at P(HNO3) ～ 2 × 10-4 Torr according to Langmuir adsorption isotherm; further increase in P(HNO3) resulted in multilayer adsorption. Under the experimental conditions (P(HNO3) = 5 × 10-7 Torr and T = 220 K), the uptake of HNO3 was found to involve purely physical adsorption without showing any sign of irreversible decomposition over all black carbon samples. Subsequent heating of the sample following the uptake at 220 K desorbed most of the adsorbed HNO3 molecules. Physical adsorption of HNO3 was found to take place on the surface of concentrated H2SO4-coated soot at 230 K, but decomposition of HNO3 took place at 296 K. Finally, the present results suggest that the HNO3 decomposition on soot aerosols through a direct gas-solid interaction, which was proposed as a possible NOy-reactivation mechanism in the atmospheric modeling of upper troposphere and lower stratosphere, should be dismissed.

Titanium dioxide (Tio2) oxidized nitric oxide (NO) to nitric acid (HNO3) very rapidly under ultraviolet light illumination, but some NO was oxidized to nitrogen dioxide (NO2), while activated carbon (AC) adsorbed NO2 well. A mixture of TiO2 and AC was thus confirmed to be an excellent photoassisted catalyst for removal of low concentration (sub-ppm) NOx from air. Addition of 1-3 wt % of ferric oxide to the mixture could markedly increase the catalytic activity. Even though the catalytic activity gradually declined with the reaction time, it could be completely recovery only by washing the catalyst was removed.

We demonstrate for the first time the complete, reversible H+/Li+ ion exchange reaction between HMO3 and LiMO3 (M=Nb, Ta) using molten LiNO3 at 320°C for 5 days. HMO3 were prepared from LiMO3 by ion exchange reactions using dilute HNO3. The results reveal that both LiMO3 prepared by normal solid state reaction between Li2CO3 and M2O5, and by ion exchanged from HMO3 using molten LiNO3 are isostructural. LiMO3 prepared using HMO3 yields nearly uniformly sized crystallites in contrast to those prepared by conventional solid state synthesis. The present method is simple and inexpensive compared to other methods of preparation of high purity LiMO3 powders.

The three-body recombination of OH with NO2 plays a critical role in tropospheric and stratospheric chemistry. The reaction plays a particularly important role in tropospheric ozone formation in polluted environments, acting as a sink for NOsu

The temperature dependence of the rate of the reaction OH + NO2 + N2 --> HNO3 + N2 was investigated by using a discharge flow system for OH production and resonance fluorescence for its detection.The reaction was investigated at room temperature in He, and between 225 and 389 K in N2.The temperature dependence could be fit by the Arrhenius expression (1.6 +/- 0.4)E-31 exp cm6 molecule-2 s-1 or preferably by (2.3 +/- 0.6)E-30(T/298)-2.9 cm6 molecule-2 s-1.Earlier data have been used to determine the temperature dependence of the high-pressure limiting rate constant for this reaction.Troe's simplified expression for calculating rate constants in the falloff region was used to compare the appropriateness of different limiting values for the description of the experimentally observed pressure dependence of the rate constant.This reevaluation of the rate data suggests more appropriate values for k0 and k for use in atmospheric modeling: k0 = 2.3E-30(T/298)-2.9 cm6 molecule-2 s-1 and k = 1.2E-11(T/298)-1.6 cm3 molecule-1 s-1.

Characterization of autocatalytic decomposition reactions is important for the safe handling and storage of energetic materials. Isothermal differential scanning calorimetry (DSC) has been widely used to detect autocatalytic decomposition of energetic materials. However, isothermal DSC tests are time consuming and the choice of experimental temperature is crucial. This paper shows that an automatic pressure tracking calorimeter (APTAC) can be a reliable and efficient screening tool for the identification of autocatalytic decomposition behavior of energetic materials. Hydroxylamine nitrate (HAN) is an important member of the hydroxylamine family. High concentrations of HAN are used as liquid propellants, and low concentrations of HAN are used primarily in the nuclear industry for decontamination of equipment. Because of its instability and autocatalytic decomposition behavior, HAN has been involved in several incidents. This paper presents calorimetric measurements for the thermal decomposition of 24 mass% HAN/water. APTAC heat-wait-search and heat-soak-search modes are used to characterize the thermal decomposition of HAN. By comparing the kinetic analysis for the two modes, it is concluded that HAN shows strong autocatalytic decomposition behavior. The most likely decomposition pathway of HAN is proposed to explain the observed autocatalytic behavior.

TiO2, a component of atmospheric mineral aerosol, catalyses the reduction of NO2 to nitrous acid (HONO) when present as an aerosol and illuminated with near UV light under conditions pertinent to the troposphere. The Royal Society of Chemistry 2006.

Ag4V2O7/BiVO4 photocatalysts with double cone-shaped nanostructure were successfully synthesized by a facile sodium polyphosphate-assisted hydrothermal method. The results demonstrate that coupling Ag4V2O7 with BiVO4 can promote the separation of photoinduced charge carriers and enhance the photon absorption efficiency. Experimental results indicate that Ag4V2O7/BiVO4 composites exhibit the enhanced photocatalystic activity for degradation of methylene blue (MB) and oxidation of NO in high concentrate (1600?ppb) compared to the pure BiVO4 under visible light irradiation (λ?>?420?nm). The composite with 0.08 mol% Ag4V2O7 has the highest photocatalytic activity. MB degradation rate can reach 98.48% in 1?h and NO oxidation rate can reach 52.83% in 0.5?h on 0.08-Ag4V2O7/BiVO4, which are about 2.90 and 3.11 times higher than that of pure BiVO4 respectively. The excellent activity can be attributed to the efficient charge transfer between Ag4V2O7 and BiVO4, and active species h+ and [rad]O2? play important roles during MB degradation and NO oxidation. In addition, this composite exhibits favorable stability during the cycling experiment, suggesting it may be a promising visible light active photocatalyst for environmental applications.

Laser photolysis technique was used to study the reactivity of nitrate radical towards four dicarboxylic acids. The temperature dependence of the reactions was investigated in the range from 278K to 318K. The effect of the acid-base equilibrium was examined by measuring the activation parameters of the dissociated and undissociated acids at different pH. For droplets or aerosols under moderate acidic conditions, the charge exchange reaction at the carboxylate group might compete with the oxidation by the hydroxyl radical. On liquid particles enriched in nitrate (such as a deliquescent ammonium nitrate), the lifetime of carboxylic groups towards the NO3 radical may be as short as few hours (or less). by Oldenbourg Wissenschaftsverlag.

Platinum-acridines and analogs thereof as cytotoxic agents for cancer treatment. Also provided methods of using hMATE1 (SLC47A1) as a biomarker to identify tumors that are likely to respond to the agents, and epigenetically sensitizing tumor tissue to anticancer drugs targeting this membrane transporter.

This paper focuses on the thermal behavior of mixtures of ammonium dinitramide (ADN) and amine nitrates. Because some mixtures of ADN and amine nitrate exhibit low melting points and high-energy content, they represent potential liquid propellants for spacecraft. This study focused on the melting behavior and thermal-decomposition mechanisms in the condensed phase of ADN/amine nitrate mixtures during heating. We measured the melting point and exothermal behavior during constant-rate heating using differential scanning calorimetry and performed thermogravimetry–differential thermal analysis–mass spectrometry (TG–DTA–MS) to analyze the thermal behavior and evolved gases of ADN/amine nitrate mixtures during simultaneous heating to investigate their reaction mechanisms. Results showed that the melting point of ADN was significantly lowered upon the addition of amine nitrate with relatively low molecular volume and low melting point. TG–DTA–MS results showed that the onset temperature of the thermal decomposition of ADN/amine nitrates was similar to that of pure ADN. Furthermore, during thermal decomposition in the condensed phase, ADN produced highly acidic products that promoted exothermic reactions, and we observed the nitration and nitrosation of amines from the dissociation of amine nitrates.

Air pollution by nitrogen oxides, NOx, is a major problem, and new capture and abatement technologies are urgently required. Here, we report a metal–organic framework (Manchester Framework Material 520 (MFM-520)) that can efficiently confine dimers of NO2, which results in a high adsorption capacity of 4.2 mmol g–1 (298 K, 0.01 bar) with full reversibility and no loss of capacity over 125 cycles. Treatment of NO2?MFM-520 with water in air leads to a quantitative conversion of the captured NO2 into HNO3, an important feedstock for fertilizer production, and fully regenerates MFM-520. The confinement of N2O4 inside nanopores was established at a molecular level, and the dynamic breakthrough experiments using both dry and humid NO2 gas streams verify the excellent stability and selectivity of MFM-520 and confirm its potential for precious-metal-free deNOx technologies.

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.

The oxidation of hydroxylamine (HONH2) by Ce(IV) in perchloric acid media took place fast and was followed by a stopped-flow spectrometer. A rate law of ?d[Ce(IV)]tot/dt?=?k′[HONH2]tot[Ce(IV)]tot was proved, where k′ stands for the observed second-order rate constant and [Ce(IV)]tot and [HONH2]tot represent the total concentrations of Ce(IV) and HONH2, respectively. The dependencies of k′ on [H+] and on ionic strength were investigated. Rapid scan spectra recorded for a typical reaction course and a stoichiometric measurement unraveled several additional characters for the redox reaction. Based on experimental results, a reaction mechanism is proposed, which involves Ce4+, Ce(OH)3+, and Ce(OH)22+ attacking on HONH3+ in parallel. Moreover, these parallel attacking reactions are the rate-determining steps, generating free radicals ?ONH2, which are rapidly oxidized to nitrate by Ce(IV). Rate constants of these rate-determining steps have been evaluated; a reactivity trend of Ce4+?>?Ce(OH)3+?>?Ce(OH)22+ is disclosed, but the reactivity differences among them are very small. The rate-determining steps are rationalized in terms of an outer-sphere electron transfer, and possible transition states are proposed in the cases of Ce(OH)3+ and Ce(OH)22+ to account for the small reactivity differences. The obtained kinetic and mechanistic results in the present work are compared with those acquired previously for the same reaction but in sulfuric acid and nitric media. It is concluded that the reaction media can play a dominant role in determining the reaction kinetics, mechanisms, and the product(s) in the oxidation of hydroxylamine by Ce(IV).

A visible-light driven photoelectrochemical (PEC) cell comprised of nanostructured BiVO4 photoanode and Pt cathode was established for organic compounds degradation with simultaneous H2 generation. BiVO4 electrode film fabricated by a simple drip-coating method showed a porous nanostructure and an intense absorption in visible light range. The PEC process possesses a rate of about 0.3207 h?1 for MO degradation, which is 8 times and 64 times faster than electrocatalytic (EC) and photocatalytic (PC) process, respectively. A simultaneous H2 generation via the PEC process was also observed and a rate of 34.44 μmol h?1 cm?2 for H2 generation was measured, which is 3 folds more efficient than the EC process. The nanostructured BiVO4 photoanode shows outstanding PEC photocurrent density and recycle performance. The proposed PEC system would be a promising strategy for wastewater treatment and energy recovery with an outstanding stability and recyclability performance.

A new strategy for capturing nitrogen oxide, NO, from the gas phase is presented. Dilute NO gas is removed from the gas phase by ionic liquids under ambient conditions. The nitrate anion of the ionic liquid catalyzes the oxidation of NO to nitric acid by atmospheric oxygen in the presence of water. The nitric acid is absorbed in the ionic liquid up to approximately one mole HNO3per mole of the ionic liquid due to the formation of hydrogen bonds. The nitric acid can be desorbed by heating, thereby regenerating the ionic liquid with excellent reproducibility. Here, time-resolved in-situ spectroscopic investigations of the reaction and products are presented. The procedure reveals a new vision for removing the pollutant NO by absorption into a non-volatile liquid and converting it into a useful bulk chemical, that is, HNO3.

The ordered mesoporous material SBA-15 (FCSBA-15) with an enhanced hydrothermal stability was successfully synthesized from natural kaolin in the presence of a fluorocarbon surfactant. FCSBA-15 was further used as the support for Fe/BiOCl with the aim of exploring its Fenton-like catalytic performance toward the degradation of 2-nitrophenol. Based on characterization techniques including X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), no phases referring to the Fe species were observed, suggesting that the Fe3+ ions may be present on the surface of flower-like BiOCl. It is noted that the Fe3+ ions could lead to a morphological reconstruction from BiOCl nanosheets to BiOCl flowers. The obtained Fe/BiOCl-FCSBA-15 exhibited an excellent degradation efficiency for 2-nitrophenol, which reached nearly 100% within 40 min by optimizing parameters such as the H2O2 dosage, pH value, temperature, Fe/Bi molar ratio and Bi/Si molar ratio. The finding reported here is important and may help to develop novel mesoporous matrix based systems for advanced catalysts.

This work comprises the photoactivity assessment of transparent sol-gel TiO2 coatings of various thickness using two test systems. The initial rates of both photocatalytic reactions, namely the oxidative bleaching of Acid Orange 7 (AO7) and the reductive bleaching of 2,6-dichlorindophenol (DCIP) increase linearly with increasing titania film thickness as well as with increasing absorbed light flux. The latter work revealed quantum yields (QY) of 0.19% and 92% for the AO7 and DCIP test system, respectively. The low QY for the AO7 oxidation is due to the combination of a slow irreversible reduction of oxygen and also for the oxidation of AO7, thus favouring the high efficiency for electron-hole recombination that is typical for aqueous organic pollutants. In contrast, the very high QY for the photocatalysed reduction of DCIP is due to the presence of a vast excess of glycerol which traps the photogenerated holes efficiently and so allow time for the slower reduction of dye to take place. Furthermore, the oxidation of glycerol results in the generation of highly reducing R-hydroxyalkyl radicals that are able to also reduce DCIP. As a consequence of this 'current doubling' effect, the observed QY (92%) is much higher than the apparent theoretical value of 50%.

Novel plasmonic 0D Ag nanocrystal decorated 3D (BiO)2CO 3 hierarchical microspheres were fabricated with a one-pot hydrothermal method. The as-prepared samples were systematically characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, photoluminescence spectra, ns-level time-resolved fluorescence spectra, photocurrent generation and EIS measurement. The results indicated that the 0D Ag nanoparticles were deposited on the surface of 3D (BiO)2CO3 hierarchical microspheres. The deposited Ag nanoparticles were reduced from Ag+ by the citrate ions from bismuth citrate. The photocatalytic activity of the as-prepared samples was evaluated towards the degradation of NO at ppb-level under visible light irradiation. The intermediate NO2 was monitored on-line during the photocatalytic reaction. The pure (BiO)2CO 3 microspheres exhibited decent visible light photocatalytic activity because of the surface scattering and reflecting (SSR effect) resulting from the special 3D hierarchical architecture. The Ag-decorated (BiO) 2CO3 microspheres (Ag/BOC) exhibited greatly enhanced photocatalytic activity, photocurrent generation and promoted NO2 oxidation compared to the pure (BiO)2CO3 microspheres. The enhanced photocatalytic activity and photocurrent generation of Ag/BOC was ascribed to the cooperative contribution of the surface plasmon resonance (SPR effect), efficient separation of electron-hole pairs and prolonged lifetime of charge carriers induced by Ag nanoparticles. The photocatalytic performance of Ag/BOC was dependent on the content of Ag loading. When the amount of Ag is controlled at 5%, the highest photocatalytic performance can be achieved. Further increasing the Ag loading content promotes aggregation of the Ag particles and transforms the uniform microspheres into non-uniform microspheres, which is not beneficial to improving the activity. Importantly, the as-prepared Ag/BOC composites exhibited high photochemical stability after multiple reaction runs. The concepts of enhancing the activity through the SSR and SPR effects provide a new avenue for the development of efficient noble metal/bismuth-based plasmonic photocatalysts with attractive nano/micro architectures for efficient visible light photocatalytic activity.

A new class of compounds, namely diamino alcohols, is described, along with a process for their production and their use as rheology modifiers in high solids mineral slurries, such as, kaolin clay slurries.

Iron is an essential metal ion with numerous roles in biological systems and advanced abiotic materials. d-(-)-Quinic acid is a cellular metal ion chelator, capable of promoting reactions with metal M(II,III) ions under pH-specific conditions. In an effort to comprehend the chemical reactivity of well-defined forms of Fe(III)/Fe(II) toward α-hydroxycarboxylic acids, pH-specific reactions of: (a) [Fe3O(CH3COO) 6(H2O)3]·(NO3)·4H 2O with d-(-)-quinic acid in a molar ratio 1:3 at pH 2.5 and (b) Mohr's salt with d-(-)-quinic acid in a molar ratio 1:3 at pH 7.5, respectively, led to the isolation of the first two heptanuclear Fe(III)-quinato complexes, [Fe7O3(OH)3(C7H10O 6)6]·20.5H2O (1) and (NH 4)[Fe7(OH)6(C7H10O 6)6]·(SO4)2·18H 2O (2). Compounds 1 and 2 were characterized by analytical, spectroscopic (UV-vis, FT-IR, EPR, and Moessbauer) techniques, CV, TGA-DTG, and magnetic susceptibility measurements. The X-ray structures of 1 and 2 reveal heptanuclear assemblies of six Fe(III) ions bound by six doubly deprotonated quinates and one Fe(III) ion bound by oxido- and hydroxido-bridges (1), and hydroxido-bridges (2), all in an octahedral fashion. Moessbauer spectroscopy on 1 and 2 suggests the presence of Fe(III) ions in an all-oxygen environment. EPR measurements indicate that 1 and 2 retain their structure in solution, while magnetic measurements reveal an overall antiferromagnetic behavior with a ground state S = 3/2. The collective physicochemical properties of 1 and 2 suggest that the (a) nature of the ligand, (b) precursor form of iron, (c) pH, and (d) molecular stoichiometry are key factors influencing the chemical reactivity of the binary Fe(II,III)-hydroxycarboxylato systems, their aqueous speciation, and ultimately through variably emerging hydrogen bonding interactions, the assembly of multinuclear Fe(III)-hydroxycarboxylato clusters with distinct lattice architectures of specific dimensionality (2D-3D) and magnetic signature.

Octahedral Cu2O particles were prepared on an indium-tin oxide glass via electrodeposition and were employed in the catalytic degradation of p-nitrophenol in the presence of H2O2. Under irradiation of a warm visible-light source, tungsten halogen lamp, Cu2O particles not only acted as a photocatalyst, but might also act as a thermal-catalyst to induce the decomposition of H2O2 and produce O2 at higher temperatures. The photogenerated electrons and holes could react with H2O2, O2, and H2O to produce abundant OH radicals, resulting in the effective oxidation of p-nitrophenol. High-performance liquid chromatography measurements of degradation intermediates showed that p-nitrophenol was first decomposed into hydroquinone and benzoquinone and then mineralized. The degradation efficiency was dependent on electrodeposition time, light intensity, H2O2 amount, and solution temperature. This catalyst could be easily recycled and used in the efficient degradation of other phenolic compounds.

Bridging superoxide in [(en)(dien)CoIII(O2)Co III(en)(dien)]5+ quantitatively oxidizes N(III) to N(V), itself being reduced to hydroperoxo group. Kinetic study and solvent isotope effect indicate two parallel paths: (a) electron transfer and (b) proton coupled electron transfer. The present study also indicates that the ancillary ligands affect the reaction rate substantially. Studies on redox behavior of metal bound superoxide are not many and this study is expected to shed some light on the redox nature of metal bound superoxide.

The invention discloses a method for preparation of mononitrated aromatic compounds in a liquid-liquid biphasic solvent system with aqueous nitric acid as one phase and ionic liquids (ILs) as the second phase, wherein the nitric acid is continuously exchanged during the reaction, or the water, that is generated during the reaction, is removed by addition of NO2 and an oxidizing agent during the reaction.

The efficiency of TiO2 (Degussa P-25) modified with an alkaline admixture (urea, BaO), sulfuric acid, or platinum in the photocatalytic oxidation of NO (50 ppm) with a flowing 7% O2 + N2 mixture under UV irradiation in a flow reactor at room temperature and atmospheric pressure is reported. Because of the progressive blocking of active sites of the photocatalyst by the reaction products (NO2, NO 3 - ), it is impossible to realize prolonged continuous removal of NO x (NO + NO2) from air without catalyst regeneration at elevated temperatures. The efficiency of the photocatalysts is characterized by specific photoadsorption capacity (SPC) calculated from the total amount of NO x adsorbed during 2-h-long irradiation. Modification of TiO 2 with 5% BaO or 5% urea raises the SPC of the catalyst by a factor of 2-3. Presumably, this promoting effect is due to the basic properties of these dopants, which readily sorb NO2 and NO 3 - . A considerable favorable effect on SPC is also attained by adding 0.5% Pt to (5% BaO)/TiO2. The SPC of the (0.5% Pt)/TiO2 catalyst depends on the state of the platinum. The samples calcined in air at 500°C, which contain Pt+ and Pt2+, have an approximately 2 times higher SPC than unpromoted TiO2 and ensure a much larger NO2/NO ratio at the reactor outlet. Conversely, the samples reduced in an H2 atmosphere at 200°C, whose platinum is in the Pt0 state, show a lower SPC than the initial TiO2 and cause no significant change in the NO2/NO ratio.

The photolysis of nitrate embedded in ice and snow can be a significant source of volatile nitrogen oxides affecting the composition of the planetary boundary layer. In this work, we examined the nitrogen oxides evolved from irradiated frozen solutions containing nitrate. Products were monitored by cavity ring-down spectroscopy (CRDS), NO-O3 chemiluminescence (CL), and chemical ionization mass spectrometry (CIMS). Under acidic conditions, the nitrogen oxides volatilized were mainly in the form of NOz, i.e., nitrous (HONO), nitric (HONO2), peroxynitrous (HOONO), and peroxynitric acid (HO2NO2). Identification of acidic nitrogen oxides by CIMS and possible HOONO, HONO2 and HO 2NO2 formation pathways are discussed.

Fundamental kinetic aspects of the decomposition of mixtures and double salts of ammonium nitrate and ammonium sulfate were studied. The effect of water and sulfuric acid additives on the thermal decomposition rate of ammonium nitrate and sulfate mixtures was examined. The constant of proton exchange between nitric acid and the sulfate anion in molten ammonium nitrate was estimated.

A new high-pressure phase of pure nitric acid (HNO3) has been characterised at 1.6 GPa at room temperature by high-pressure neutron powder and X-ray single-crystal diffraction techniques. This is the first crystalline phase obtained upon compression of liquid nitric acid at room temperature and appears to be the stable phase up to pressures of at least 4 GPa. The crystal structure of this new phase shows some similarities to that of the low-temperature phase of nitric acid at ambient pressure, which has been redetermined as part of this study. Both structures share a herringbone packing of hydrogen-bonded molecular catemers, although the presence of disorder within the hydrogen bonds within one of the catemers of the low-temperature phase makes its structure comparatively more complex.

We have observed the infrared spectrum of 15NO3 by a high resolution Fourier transform infrared (FT-IR) spectrometer using the reaction of F atoms with H15NO3. Five 2E' - 2A2' bands are identified in the 1850 - 3150 cm-1 region. The rotational analyses indicate that these bands have the lower state in common, which coincides with the ground state of planar D3h symmetry. The upper 2E' states more or less suffer from perturbations by close-lying dark states. Among them, those of the 2004, 2128, and 2492 cm-1 bands are analyzed to determine molecular parameters in these states by fixing the ground-state constants to those derived by a combination difference method. The spin - orbit and Coriolis coupling constants in the 2E' states are substantially different for different vibronic states. The vibrational assignments of NO3 in the ground electronic state are discussed using experimental data heretof ore available, supplemented by those obtained by the present study.

Thermal decomposition of the energetic ionic liquids 1-methyl-4-amino-1,2, 4-triazolium iodide (Me4ATI), 1-methyl-4-amino-1,2,4-triazolium nitrate (Me4ATN), 1-amino-3-methyl-1,2,3-triazolium iodide (Me1ATI), and 1-amino-3-methyl-1,2,3-triazolium nitrate (Me1ATN) was studied by confined rapid thermolysis. Sub-milligram quantities of the compounds were subjected to decomposition under isothermal conditions achieved by initially heating the sample at rates of approximately 2000 K/s. The products formed by decomposition under the afore-mentioned conditions were sampled by rapid scan FTIR spectroscopy and time-of-flight mass spectrometry. Decomposition studies involving the iodide salts were carried out around 270-290.C, whereas the nitrate salts were subjected to 320-340.C. The amino group was found to be involved in the initiation reaction, forming copious quantities of ammonia from the iodide compounds and, N2O and H2 O from the nitrate compounds. The extent of decomposition of the triazole ring was minimal at the considered temperatures.

The effects of fullerenes, including fellerene soot (FS), extracted fullerene soot (EFS) and pure C60 on the thermal decomposition of ammonium perchlorate (AP) compared with traditional carbon black (CB) catalyst has been studied by employing t

The syntheses of the triorganochalcogenium dinitramide salts [Ph 3Te][N(NO2)2] (1), [Me3Te][N(NO 2)2] (2), [Ph3Se]-[N(NO2) 2] (3), [Me3Se][N(NO2)2] (4), [Ph3S][N(NO2)2] (5), and [Me 3S][N(NO2)2] (6), their characterization by multinuclear NMR spectroscopy, vibrational spectra, and single-crystal structures are described. The syntheses of the compounds were achieved with the help of [Ag(py)2][N(NO2)2] and [Ag(NCCH 3)][N(NO2)2] as dinitramide transfer reagents. Whereas in the crystal structure of 1 different coordination modes to dinitramide moieties are present, the crystal structure of 3 shows only a single intermolecular contact to the dinitramide moiety. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Band strengths for the second (3vOH) and third (4VOH) overtones of the OH stretch vibration of peroxynitric acid, HO 2NO2 (PNA) in the gas-phase were measured using Cavity Ring-Down Spectroscopy (CRDS). Both OH overtone transitions show diffuse smoothly varying symmetrical absorption profiles without observable rotational structure. Integrated band strengths (base e) at 2% K were determined to be S3vOH = (5.7 ± 1.1) × 10-20 and S 4vOH = (4.9 ± 0.9) × 10-21 cm2 molecule-1 cm-1 with peak cross sections of (8.8 ± 1.7) × 10-22 and (7.0 ± 1.3) × 10-23 cm2 molecule-1 at 10086.0 ± 0.2 cm-1 and 13095.8 ± 0.4 cm-1, respectively, using PNA concentrations measured on line by Fourier-transform infrared and ultraviolet absorption spectroscopy. The quoted uncertainties are 2σ (95% confidence level) and include estimated systematic errors in the measurements. OH overtone spectra measured at lower temperature, 231 K, showed a narrowing of the 3vOH band along with an increase in its peak absorption cross section, but no change in S3vOH to within the precision of the measurement (±9%). Measurement of a PNA action spectrum showed that HO2 is produced from second overtone photodissociation. The action spectrum agreed with the CRDS absorption spectra. The PNA cross sections determined in this work for 3v OH and 4vOH will increase calculated atmospheric photolysis rates of PNA slightly.

Ultraviolet and visible-light-responsive titania was synthesized and employed in the NOx photomineralization. A thermal decomposition reaction of titanium isopropoxide was carried out with a metal-organic chemical vapor deposition (MOCVD), enabling continuous production of TiO2 nanoparticles. Carbon-containing titanium dioxide with the anatase phase prepared at 500 °C under nitrogen atmosphere exhibited high photocatalytic activity for NO oxidation under visible-light illumination. Experimental results indicate that up to 48% removal of NOx can be achieved in a continuous flow type of reaction system under visible-light illumination (green LED). The chamber temperature in this MOCVD process plays an important role in lattice structure formation, and also affected TiO2 carbon content. The carbonaceous species on the TiO2 surface, shown by X-ray diffractometry (XRD), and Raman, UV-vis, and X-ray photoelectron spectroscopies (XPS), is important to the visible-light absorption and visible-light-catalytic mineralization of NOx.

The interaction of NO3 free radical and N2O 5 with laboratory flame soot was investigated in a Knudsen flow reactor at T = 298 K equipped with beam-sampling mass spectrometry and in situ REMPI detection of NO2 and NO. Decane (C10H22) has been used as a fuel in a co-flow device for the generation of gray and black soot from a rich and a lean diffusion flame, respectively. The gas-phase reaction products of NO3 reacting with gray soot were NO, N 2O5, HONO, and HNO3 with MONO being absent on black soot. The major loss of NO3 is adsorption on gray and black soot at yields of 65 and 59%, respectively, and the main gas-phase reaction product is N2O5 owing to heterogeneous recombination of NO3 with NO2 and NO according to NO3 + {C} → NO + products. HONO was quantitatively accounted for by the interaction of NO2 with gray soot in agreement with previous work. Product N 2O5 was generated through heterogeneous recombination of NO3 with excess NO2, and the small quantity of HNO 3 was explained by heterogeneous hydrolysis of N2O 5. The reaction products of N2O5 on both types of soot were equimolar amounts of NO and NO2, which suggest the reaction N2O5 + {C} → N2O3(ads) + products with N2O3(ads) decomposing into NO + NO 2. The initial and steady-state uptake coefficients γ0 and γss of both NO3 and N 2O5 based on the geometric surface area continuously increase with decreasing concentration at a concentration threshold for both types of soot. γss of NO3 extrapolated to [NO 3] → 0 is independent of the type of soot and is 0.33 ± 0.06 whereas γss for [N2O5] → 0 is (2.7 ± 1.0) × 10-2 and (5.2 ± 0.2) × 10-2 for gray and black soot, respectively. Above the concentration threshold of both NO3 and N2O5, γss is independent of concentration with γ ss(NO3) = 5.0 × 10-2 and γss-(N2O5) = 5.0 × 10-3. The inverse concentration dependence of γ below the concentration threshold reveals a complex reaction mechanism for both NO3 and N2O5. The atmospheric significance of these results is briefly discussed.

A high-pressure turbulent flow reactor coupled with a chemical ionization mass-spectrometer was used to determine the branching ratio of the HO 2 + NO reaction: HO2 + NO -OH + NO2 (1a), HO2 + N-O → HNO3 (1b). The branching ratio, β-k1b/k1a, was derived from the measurements of chemically amplified concentrations of the NO2 and HNO3 products in the presence of O2 and CO. The pressure and temperature dependence of βwas determined in the pressure range of 72-600 Torr of N2 carrier gas between 323 and 223 K. At each pressure, the branching ratio was found to increase with the decrease of temperature, the increase becoming less pronounced with the increase of pressure. In the 298-223 K range, the data could be fitted by the expression: β(T,P) = (530 ±10)/T(K) + (6.4 ±1.3) x 10-4P(Torr- (1.73 ±0.07), giving β 0.5% near the Earth's surface (298 K, 760 Torr) and 0.8% in the tropopause region (220 K, 200 Torr). The atmospheric implication of these results is briefly discussed.

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

Cis, cis-peroxynitrous acid is known to be an intermediate in atmospheric reactions between OH and N O2 as well as HOO and NO. The infrared absorption spectra of matrix-isolated cc-HOONO and cc-DOONO in argon have been observed in the range of 500-8000 cm-1. Besides the seven fundamentalvibrational modes that have been assigned earlier for this molecule [Zh ang, J. Chem. Phys. 124, 084305 (2006)], more than 50 of the overtone and combination bands have been observed for cc-HOONO and cc-DOONO. Ab initio CCSD(T)/atomic natural orbital anharmonic force field calculations were used to help guide the assignments. Based on this study of the vibrational overtone transitions of cis, cis-HOONO that go as high as 8000 cm-1 and the earlier paper on the vibrational fundamentals, we conclude that the CCSD(T)/ANO anharmonic frequencies seem to correct to ±35 cm-1. The success of the theoretically predicted anharmonic frequencies {} in assigning overtone spectra of HOONO up to 8000 cm-1 suggests that the CCSD(T)/ANO method is producing a reliable potential energy surface for this reactive molecule.

Nitrosyl perchlorate, [NO][ClO4], is a known and stable salt. In this contribution we describe the attempt to synthesize the isomeric compound nitryl chlorate, [NO2][ClO3]. The results are discussed on the basis of volume-based thermodynamics (VBT).

High pressure experiments on the OH + NO2 reaction are presented for 3 different temperatures. At 300 K, experiments in He (p = 2-500 bar) as well as in Ar (p = 2-4 bar) were performed. The rate constants obtained in Ar agree well with values which have been reported earlier by our group (Forster, R.; Frost, M.; Fulle, D.; Hamann, H. F.; Hippler, H.; Schlepegrell, A.; Troe, J. J. Chem. Phys. 1995, 103, 2949. Fulle, D.; Hamann, H. F.; Hippler, H.; Troe, J. J. Chem. Phys. 1998, 108, 5391). In contrast, the rate coefficients determined in He were found to be 15-25% lower than the values given in our earlier publications. Additionally, results for He as bath gas at elevated temperatures (T = 400 K, p = 3-150 bar; T = 600 K, p = 3-150 bar) are reported. The results obtained at elevated pressures are found to be in good agreement with existing literature data. The observed falloff behavior is analyzed in terms of the Troe formalism taking into account two reaction channels: one yielding HNO 3 and one yielding HOONO. It is found that the extracted parameters are in agreement with rate constants for vibrational relaxation and isotopic scrambling as well as with experimentally determined branching ratios. Based on our analysis we determine falloff parameters to calculate the rate constant for atmospheric conditions.

It was found that during thermal decomposition of hydrates of d-metal nitrates nitrous oxide (N2O) is always present among the other gaseous products: H2O, HNO3, NO, NO2 and O2. In all studied decomposition reactions the nitrous oxide formed contains approximately 5-8% of total nitrogen coming from nitrate. Two new mechanisms of N2O formation, based on the reaction between NO or NO2 and nitrate ion, have been proposed. The discussed third possible mechanism: (a) 2NO = N2O2 and (b) N2O2 + NO = N2O + NO2 is unlikely.

Kinetic studies and the mechanism determination of ClONO2 uptake on polycrystalline NaCl were carried out using a coated-insert flow tube reactor combined with high-resolution, low-energy electron-impact mass spectrometer under the following conditions: p =1-2 Torr, linear flow velocity v = 3.5-75 m s-1, T = 293 and 387 K, [ClONO2] = (0.5-25) × 1012 molecules cm-3. The salt was deposited as a film from nonsaturated aqueous solution on the sliding rod. The temporal dependences of the uptake coefficient and the partial uptake coefficients leading to a formation of the prime Cl2 and HOCl products were measured for different ClONO2 concentrations. These dependences are established to be described by γ = γ0 exp(-t/τ) + γs, γ0.s-1 = a0.S + b0.s[ClONO2]. In the framework of the proposed kinetic model, the data are explained and the main elementary kinetic parameters of the uptake are evaluated. The model is based on a combination of Langmuir adsorption, formation of surface complexes on initial active sites, Z ch, followed by their unimolecular decomposition. Decomposition is proposed to proceed concurrently in two channels, one of which is a released surface site that conserves the properties of the initial site. In the other channel, the initial Zch transforms into Zph followed by steady-state uptake and reproduction of final Zph. The model gives an analytical expression for experimental parameters γ0, γs, and τ in terms of elementary rate constants and the reactant volume concentration. The final objective of the proposed model is the extrapolation of γ0, γs, and r parameters to real tropospheric conditions.

Anatase TiO2 particles were uniformly and dispersedly deposited on the surface of glass fibers by a liquid phase deposition (LPD) method from a TiF4 aqueous solution upon addition of H3BO3 at 60 °C and then calcined at 60, 300 and 500 °C. The photocatalytic activity of the samples was evaluated by the photocatalytic oxidation of nitrogen monoxide (NO) in the gaseous phase. It was found that calcination temperatures obviously influenced the surface morphology and photocatalytic activity of the TiO2 particles deposited on the glass fibers. At 300 °C, the TiO2 samples exhibited the highest photocatalytic activity for the photocatalytic oxidation of NO and for the further conversion of NO2 (from NO2 to HNO3) due to the enhancement of crystallization of anatase TiO2 particles. At 500 °C, the photocatalytic activity of the sample decreased significantly due to the dropping of many TiO2 particles from the glass fibers. Compared with the TiO2 film photocatalyst, the TiO2 particles deposited on the glass fibers exhibited a lower deactivation rate.

Ring cycle: Iron and manganese corroles are among the most efficient decomposition catalysts of peroxynitrite reported to date. The catalytic rate of the iron complex is higher than that of analogous porphyrins, and the manganese complex operates through

We have applied cavity ring-down spectroscopy to a kinetic study of the reaction of NO3 with CH3I in 20-200 Torr of N2 diluent at 298 K. The rate constant of the reaction of NO3 + CH 3I was determined to be (4.1 ± 0.2) × 10-13 cm3 molecule-1 s-1 in 100 Torr of N2 diluent at 298 K and is pressure-independent. This reaction may significantly contribute to the formation of reactive iodine compounds in the atmosphere.