Decomposition Of Nitric Acid Research Articles

Ab Initio Molecular Dynamics Study of Heterogeneous Nitric Acid Decomposition Reactions on Graphite Surfaces

The goal of the present work is to unravel the role of the soot surface on the decomposition of nitric acid as a possible renoxification process. We study the monomolecular and the bimolecular decomposition reactions of gas-phase nitric acid on a pristine and on a defective graphite surface as a simple model of the interactions occurring on the surface of atmospheric soot particles. The metadynamics method is employed to reproduce the atomistic details of the reaction paths for both monomolecular and bimolecular processes. Several different intermediate states, which are encountered along the reactive trajectory, are analyzed, and the role of the surface in catalyzing the reactions is discussed.

High-Temperature Reactions of OH Radicals with Benzene and Toluene

The rate constants for the reactions of OH radicals with benzene and toluene have been measured directly by a shock tube/pulsed laser-induced fluorescence imaging method at high temperatures. The OH radicals were generated by the thermal decomposition of nitric acid or tert-butyl hydroperoxide. The derived Arrhenius expressions for the rate constants were k(OH + benzene) = 8.0 x 10(-11) exp(-26.6 kJ mol(-1)/RT) [908-1736 K] and k(OH + toluene) = 8.9 x 10(-11) exp(-19.7 kJ mol(-1)/RT) [919-1481 K] in the units of cubic centimeters per molecule per second. Transition-state theory (TST) calculations based on quantum chemically predicted energetics confirmed the dominance of the H-atom abstraction channel for OH + benzene and the methyl-H abstraction channel for OH + toluene in the experimental temperature range. The TST calculation indicated that the anharmonicity of the C-H-O bending vibrations of the transition states is essential to reproduce the observed rate constants. Possible implications to the other analogous H-transfer reactions were discussed.

沸騰硝酸水溶液の酸化還元反応に対する熱力学的考察

In order to understand corrosion of metals in nitric acid solutions, it is necessary to know the generation mechanism of high equilibrium potential in the solutions, especially under boiling conditions. Existing nitrogen oxides in nitric acid solutions were first analyzed by Raman spectroscopy and then existing amount of nitrogen oxides were examined by thermodynamic calculation using the SOLGASMIX software. The Raman spectroscopic analysis showed that the existing amount of un-dissociated HNO3 increased with increasing nitric acid concentration and solution temperature. The existing amount of NO2 also increased by thermal decomposition. The thermodynamic calculation showed that the important nitrogen oxides in nitric acid solutions are HNO3, NO3-, HNO2, NO2, and NO. The equilibrium potential of nitric acid solutions is, however, mainly decided by the HNO3/HNO2 equilibrium. The thermodynamic calculation also suggested that the increased oxidization potential on the heat-transfer surface is attributed to the reduction of nitrous acid concentration by the thermal decomposition of nitrous acid on the surface and the continuous removal of decomposition product from the solutions by boiling bubbles.

NITROGEN OXIDE TRACE GAS TRANSPORT AND TRANSFORMATION: II. MODEL SIMULATIONS COMPARED WITH DATA

The development of process-based models describing N oxide trace gas emissions from agricultural soils will assist in the assessment of pre- sent sources, prediction of future trends, and development of mitigation strategies. We compare the predictions of a transport and transformation model with data from intact soil core experiments and then use the model to evaluate the relative importance of individual processes after application of anhydrous ammonia to moderately acidic soil. Soil-gas concentrations of NO and N2O are adequately described using previously obtained kinetic expressions. Net NO surface fluxes are shown to be the result of high rates of subsurface gross NO production (>100 mg N m � 2 h � 1 ) balanced by gross consumption rates equivalent to 92-97% of gross production. The overall temperature dependency of NO emissions is de- scribed adequately as the net result of individual temperature-dependent processes. Denitrification was estimated to contribute only 8-14% of the total N2O source under primarily aerobic conditions, with the balance caused by abiotic nitrous acid decomposition. The bulk soil reactivity of NO2 was estimated to be at least 500 times greater than the reactivity of NO. The potential for nonbiological nitrate formation is examined, and the effectiveness of pH control and subsurface fertilizer injection for min- imizing gas losses are evaluated. (Soil Science 2002;167:49-61)

Nitric and nitrous oxide emissions following fertilizer application to agricultural soil: Biotic and abiotic mechanisms and kinetics

Emissions of nitric and nitrous oxide (NO and N2O) from agricultural soils may have several consequences, including impacts on local tropospheric and global stratospheric chemistry. Elevated NO and N2O emissions following application of anhydrous ammonia to an agricultural field in California were driven by the biological generation of nitrite (NO2−) and subsequent abiotic decomposition of nitrous acid (HNO2). Maximum fluxes of > 1000 ng NO‐N cm−2 h−1 and > 400 ng N2O‐N cm−2 h−1 were observed, and emissions of > 100 ng NO‐N cm−2 h−1 and > 50 ng N2O‐N cm−2 h−1 persisted for >4 weeks. Laboratory experiments were performed to determine rate coefficients and activation energies for HNO2‐mediated NO and N2O production. Kinetic parameters describing the conversion of NO to N2O were measured and were found to vary with water‐filled pore space (WFPS). Regression models incorporating HNO2, WFPS, and temperature accounted for 75–77% of the variability in field fluxes. A previously developed NO emissions model was modified to incorporate a kinetic expression for HNO2‐ and temperature‐dependent production. The model tended to underestimate fluxes under low‐flux conditions and overestimate fluxes under high‐flux conditions. These data indicate that (1) control of acidity may be an effective means for minimizing gaseous N losses from fertilized soils and possibly for improving air quality in rural areas, (2) the transformation of HNO2‐derived NO may be an important mechanism of N2O production even under relatively aerobic conditions, and (3) mechanistic models which account for spatial heterogeneity and transient conditions may be required to better predict field NO fluxes.

Heterogeneous reactivity of nitrous acid on submicron sulfuric acid aerosol

An aerosol flow reactor has been employed to study nitrous acid decomposition (2HONO→NO+NO2+H2O) on submicron sulfuric acid aerosol. The reactive uptake coefficient was obtained for 60 wt.% sulfuric acid at room temperature and pressure. It was found to be linearly dependent upon the nitrous acid partial pressure with γr≈pHONO(ppb)×10-8. The bulk-liquid phase reaction rate constant was measured in a separate experiment and a value of kII=(19.5±2.0) d mol-1 s-1 was obtained for 60 wt.% sulfuric acid at room temperature. This value is too small to explain the observed loss of HONO to the aerosol particles implying that the heterogeneous decay of nitrous acid occurs on the surface of the aerosol. A second-order surface rate constant of ksurf=(4.6±1.5)×10-17 cm3 m molecule-1 s-1 was determined that was a factor of a thousand greater than that previously reported for other surfaces. Despite this relatively large decay constant, it is still too small to have any significance upon nitrous acid concentrations in the night-time boundary layer. This work adds to the increasing number of heterogeneous reactions that are found to be significantly enhanced at the surface of a liquid.

An Experimental Study of Worst Case Scenarios of Nitric Acid Decomposition in a Toluene Nitration Process

Several worst case scenarios were carried out for safety evaluation of an existing nitration process. Heterogeneous nitric acid decomposition is observed to be the worst credible scenario in the toluene nitration process. Fire or explosion may subsequently develop due to temperature or pressure runaway from the undesired reaction. Gassy nitric acid decomposition can easily be triggered by process derivation from the desired reaction. In this study, a heat-flux calorimeter (C80–II) and an adiabatic calorimeter (VSP2) were used to measure the thermokinetics and determine the runaway characteristics for assessing worst credible scenarios. The heat of reaction of toluene mononitration is measured to be 190.9±6 3.6/(kJ mol −1 ). The calculated Arrhenius parameters are Ea (kJ mol −1 ) = 30.9±2.1 and A (mol −1.5 l 1.5 s −1 ) = (1.38 ± 0.07) × 10 −2 . The ‘worst case’ scenarios were chosen at the following conditions: loss of cooling, stirrer failure, batch-wise charging, and decomposition of reactants. The experimentally determined worst case was found to be a combination of a loss of cooling with batch-wise charging coupled with decomposition of nitric acid with full mixing. Adiabatic temperature rise, self-heat rate, final pressure and non-condensable gas quantity in the VSP2 experiment were used to assess thermal explosion in a nitration reactor. Unstable and critical onset temperature to runaway is determined as about 140°C for the process in this study.

Gravity Effect on Copper Corrosion

With a new gravity electrode by means of centrifugal force, gravity effect on copper corrosion in nitric acid was examined. The electrode system could control the gravity field up to 350 g by changing rotation speed. The experiments were performed in three different configuration modes of copper electrode; parallel, upward- vertical and downward-vertical to the gravity. After immersing copper electrode into 3 moldm -3 HNO 3 solution, under given gravity, corrosion currents and weight losses of the electrodes were measured. Consequently, it became obvious that copper corrosion is drastically protected in high gravity field. As long as the gravity is not so high, the upward-vertical mode indicated the most drastic change in corrosion rate with increasing gravity. In high gravity field, the corrosion rates in all modes converged to negligibly small values. On the contrary, in the solution with 0.01 moldm -3 HNO 3 + 3 moldm -3 NaNO 3 , the corrosion rate increased with increasing gravity. All these results was attributed to the facts that the convection flow induced by gravity affects the corrosion processes in different two ways; one is the blocking effect on copper dissolution and another the promoting effect on nitric-acid decomposition.

Nitrous and nitric acid ionisation equilibria and nitrous acid-catalysed nitration of 4-fluorophenol, in aqueous trifluoroacetic acid

The acidity dependencies of the equilibria between nitrous acid and nitrosonium ion, and between nitrate ion and nitric acid in aqueous trifluoroacetic acid (TFA) have been investigated. The decomposition of nitrous acid in air-saturated aqueous TFA has been studied and is considerably faster than in dilute HCl. Nitrous acid and 4-fluorophenol in TFA react to give quantitatively 4-fluoro-2-nitrophenol. The kinetics are shown to be consistent with the mechanism previously proposed for similar substrates in dilute aqueous acid.

On the voltammetric and spectroscopic characterization of nitric oxide adlayers formed from nitrous acid on Pt(h,k,l) and Rh(h,k,l) electrodes

Cyclic voltammetry and in situ FTIR spectroscopy have been employed to characterize NO adlayers at platinum and rhodium single-crystal electrodes. These adlayers, which are generated upon surface decomposition of nitrous acid, give infrared spectra similar to those observed for the same surface at high NO coverages under UHV conditions. The NO stretching frequency turned out to be potential dependent with a significant upward shift as the electrode potential increased. The analysis of the absolute spectra obtained for NO-covered Pt(111) and Rh(111) electrodes shows a linear variation of the band center frequency of linearly bonded NO with slopes of 65 and 20cm −1 V −1, respectively. In addition to this potential dependence of the NO stretching frequency, the spectra obtained with the Rh(111) electrode suggests the existence of a change from bridge to linearly bonded NO as the electrode potential increases. Parallel voltammetric experiments allowed the determination of the surface coverage.

Role of the reaction of nitric oxide with oxygen in the decomposition of nitrous acid in aqueous acid solution

The decomposition of nitrous acid in air-saturated aqueous acid has been monitored. Comparison with numerical integrations indicate that this decomposition occurs via reaction of dissolved oxygen with nitric oxide.

Comparison between NOx Evolution Mechanisms of Wild-Type and nr1 Mutant Soybean Leaves

The nr(1) soybean (Glycine max [L.] Merr.) mutant does not contain the two constitutive nitrate reductases, one of which is responsible for enzymic conversion of nitrite to NO(x) (NO + NO(2)). It was tested for possible nonenzymic NO(x) formation and evolution because of known chemical reactions between NO(2) (-) and plant metabolites and the instability of nitrous acid. It did not evolve NO(x) during the in vivo NR assay, but intact leaves did evolve small amounts of NO(x) under dark, anaerobic conditions. Experiments were conducted to compare NO(3) (-) reduction, NO(2) (-) accumulation, and the NO(x) evolution processes of the wild type (cv Williams) and the nr(1) mutant. In vivo NR assays showed that wild-type leaves had three times more NO(3) (-) reducing capacity than the nr(1) mutant. NO(x) evolution from intact, anerobic nr(1) leaves was approximately 10 to 20% that from wild-type leaves. Nitrite content of the nr(1) mutant leaves was usually higher than wild type due to low NO(x) evolution. Lag times and threshold NO(2) (-) concentrations for NO(x) evolution were similar for the two genotypes. While only 1 to 2% of NO(x) from wild type is NO(2), the nr(1) mutant evolved 15 to 30% NO(2). The kinetic patterns of NO(x) evolution with time weré completely different for the mutant and wild type. Comparisons of light and heat treatments also gave very different results. It is generally accepted that the NO(x) evolution by wild type is primarily an enzymic conversion of NO(2) (-) to NO. However, this report concludes that NO(x) evolution by the nr(1) mutant was due to nonenzymic, chemical reactions between plant metabolites and accumulated NO(2) (-) and/or decomposition of nitrous acid. Nonenzymic NO(x) evolution probably also occurs in wild type to a degree but could be easily masked by high rates of the enzymic process.

State-resolved unimolecular reactions: The vibrational overtone initiated decomposition of nitric acid

We have determined the internal state distribution of the OH fragment from the unimolecular dissociation on nitric acid initiated by excitation in the regions of the fourth (5νOH) and fifth (6νOH) overtones of the O–H stretching vibration. The two excitations correspond to average excess energies of 350 and 2700 cm−1, respectively. In the case of 5νOH excitation, where states near the threshold energy for dissociation dominate the decomposition, phase-space theory (PST) correctly predicts the observed populations of both the rotational and spin–orbit states of the OH fragment. This observation, which is consistent with there being no barrier to the unimolecular dissociation on the ground electronic state potential-energy surface, illustrates the ability of simple statistical theory to describe spin–orbit state populations, at least in near-threshold decomposition of nitric acid. In contrast, the same model does not reproduce the quantitative details of the decomposition initiated by excitation of the fifth overtone vibration, although it does reproduce the general shape of the OH rotational state distribution. The observed rotational state distribution for the 6νOH initiated decomposition is less energetic than the PST prediction, and the measured spin–orbit state population ratio P(2Π3/2)/P(2Π1/2) is larger than the calculation.

Voltammetric determination of metal traces in marine samples after nitric acid decomposition

For the inverse voltammetric metal determination in biological materials disturbing organic compounds must be destroyed completely during sample decomposition. Using the example of marine sample materials, it is shown that the oxidation of organic samples using concentrated nitric acid in closed quartz vessels under pressure at 320°C leads to solutions free of organic carbon. No additional treatment with perchloric acid is necessary. The inverse voltammetric determination of Zn, Cd, Pb and Cu is free of interferences.

Stoicheiometric and nitrogen-15 labelling studies on the hyponitrous acid–nitrous acid reaction

The stoicheiometry of the hyponitrous acid–nitrous acid reaction has been determined over a wide acidity range, up to 8.5 mol dm–3 HClO4. For approximately 1 : 1 reaction conditions, the major reaction pathway gives N2 and HNO3 as products, together with the production of N2O (by self decomposition of hyponitrous acid) and NO (by self decomposition of nitrous acid). In addition, 15NO produced by self decomposition of H15NO2 reacts with H214N2O2 to give some 14NO and N2O of mixed isotopic composition. Reactions under other conditions gave products that may be accounted for by varying contributions from these reactions.

Carbanion nitrosation. Reaction of malononitrile with nitrous acid

Malononitrile reacts readily with nitrous acid in aqueous acid buffer solutions, particularly in the presence of nucleophilic catalysts X [Br–, SCN–, and SC(NH2)2] to give the corresponding oxime product C(CN)2NOH. In the absence of catalysts and also with Cl– as catalyst, reaction is slow and competes with the spontaneous decomposition of nitrous acid. The rate equation at one acidity for the catalysed reaction is established as rate =k1[CH2(CN)2][HNO2][X], which suggests that reaction occurs by rate-limiting attack of the XNO species. In the pH range 2–4.5 the dependence of k1 upon acidity varies from being approximately first order in [H+] at low acidities to being approximately zero order in [H+] at higher acidities. All the results are consistent with a mechanism involving a rate-limiting reaction between XNO and the carbanion –CH(CN)2. Analysis of the kinetic results reveals that the second-order rate constants k2 for this step are, respectively, 1.1 × 1010, 4.2 × 109, and 5.0 × 109 dm3 mol–1 s–1(at 25 °C) for the BrNO, ONSCN, and ONSC(NH2)2 reactions. Thus each of these nitrosating species appears to react at the diffusion-controlled limit. Comparison with literature values of other substrate nitrosations shows that this carbanion is the most reactive substrate studied in nitrosation. There are no other reported examples where (the less reactive) ONSCN and ONSC(NH2)2 species react upon encounter. Reaction also occurs in aqueous acetic acid solutions, again at convenient rates only in the presence of catalysts X, i.e. involving reaction via XNO.

Kinetics and mechanism of thermal decomposition of nitric acid in sulfuric acid solutions

1. The initial rates of thermal decomposition of HNO3 in aqueous and nonaqueous H2SO4 media were measured; their temperature dependences were determined for HNO3-H2SO4 systems. 2. The thermal decomposition of HNO3 in sulfuric acid solutions proceeds via the decomposition of N2O5.

INVITED REVIEW ABSORPTION OF NOX GASES

Oxidation of nitric oxide is an important step in NOx absorption. Recent advances namely catalytic oxidation and the use of slrong oxidizing agents have been reviewed. The refinements which have been made in the kinetics of NO oxidation have been discussed. Several liquid phase absorbents have been suggested for the NO removal, particularly for the purpose of pollution abatement. Different models for NO oxidation using nitric acid have been analysed and the limitations of published information have been brought out. Absorption of tetravalent nitrogen oxide (NO2 and N2O4) has received considerable attention. The absorbents include water, nitric and sulfuric acids, sodium hydroxide, sodium sulfite and sodium chlorite. Absorption in water and nitric acid is important in the manufacture of nitric acid. The published information on the mechanism of NO2 and N2O4 absorption in water has been critically analysed. The problem of nitrous acid decomposition has been analysed on the basis of film theory. The predicti...

Systematic design of chemical oscillators. 6. Nitrous acid decomposition catalyzed by an iron(II) complex: tris(3,4,7,8-tetramethyl-1,10-phenanthroline)iron(II)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSystematic design of chemical oscillators. 6. Nitrous acid decomposition catalyzed by an iron(II) complex: tris(3,4,7,8-tetramethyl-1,10-phenanthroline)iron(II)Irving R. Epstein, Kenneth Kustin, and Reuben H. SimoyiCite this: J. Am. Chem. Soc. 1982, 104, 3, 712–717Publication Date (Print):February 1, 1982Publication History Published online1 May 2002Published inissue 1 February 1982https://doi.org/10.1021/ja00367a013RIGHTS & PERMISSIONSArticle Views100Altmetric-Citations12LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (700 KB) Get e-Alerts Get e-Alerts

The Chemistry and Characteristics of Nitric Acid-Graphite Intercalation

ABSTRACTGas-phase intercalation of graphite by nitric acid is a one-step process. The weight uptake of the sample is a function of nitric acid vapor pressure. A pure second stage compound was formed when the HNO3 reservoir was maintained at 17°C. Only a fourth stage compound was formed when the acid was kept at 0°C. The product gases due to intercalation and gas species evolved during deintercalation were analyzed by mass spectrometry. NO2 and H2O were the major components detected from the intercalation product gases. A small amount of oxygen was also present. The existence of O2 is probably due to the photo-chemical decomposition of nitric acid. As such, the photodecomposition of nitric acid is not a contributory factor in the intercalation chemistry.