Reaction Of Nitrous Oxide Research Articles

Bimolecular reaction of nitrous oxide (N2O) with hydroperoxy radical (HO[formula omitted]): A computational study

In the present work, we have studied the reaction of N2O with the HO2 radical, employing kinetics and quantum chemical calculations. For quantum chemical calculations, we used the post-CCSD(T) method, which includes corrections from full triple excitations and partial quadratic excitations at the coupled-cluster level, and for the rate calculation we used transition state theory (TST). Quantitatively, our study suggests that after the reaction of N2O with the Criegee intermediate, the N2O + HO2• can be the fastest among the known reactions of N2O with important atmospheric oxidizing agents. In addition, among various known reaction of the N2O, the title reaction is the only hydrogen atom transfer (HAT) reaction of N2O.

Deoxygenation reactions of nitrous oxide assisted by oriented external electric field

AbstractDue largely to the high stability and the potential ozone‐depleting, the transformation of greenhouse gas nitrous oxide has gained much attentions. In present paper, a new insight into the deoxygenation of nitrous oxide with silane was reported by using oriented external electric field (OEEF) as a catalytic strategy. When the OEEF was employed, the reaction barrier of deoxygenation was marvelously decreased as it was oriented along the positive NO/OSi bond‐axis. Especially the field strength is 300 × 10−4 a.u., the differences are up to 22.4/18.3 kcal mol−1 as compared with that of nonfield. In addition, once the H atom in SiH4 was replaced by methyl, two reaction modes were obtained, in which the deoxygenation process was easier when the N2O captured the H atom attached to the Si atom, not attached to the C atom. Further, the solvent effects of deoxygenation reaction were also considered, but with a weak influence were obtained.

Phenomenological regression rate model in axial injection end-burning hybrid rocket motor using different oxidizers

Compared with conventional configurations, axial-injection end-burning hybrid rocket motors work with multiport fuel grains, which mainly burn in the axial direction. The consumption rate is controlled by the several flames developed at the end of each port. Although many studies of performance and flame stability have been carried out in the past, a phenomenological model of the axial regression rate was never provided in the past, which is the objective of the current work. The validation of the physical model is performed by a comparative study between firing tests using gaseous oxygen and nitrous oxide. Two experimental campaigns performed by a pressure-controlled combustion chamber are carried out with a single port grain in operative conditions equivalent to the multiport configuration. The axial regression rate was measured by varying the port diameter in a range between 0.5 and 4.6 mm, the mass flow rate between 0.004 and 1.7 g/s, and the chamber pressure between 0.1 and 3.4 MPa. The measured axial regression rate was quantitatively lower with nitrous oxide than oxygen, and the pressure sensitivity exponent decreased from 1.85 to 1.5, respectively. The physical reason has been attributed to the decomposition reaction of nitrous oxide occurring upstream of the flame front. In addition, a general methodology for fuel grain design is given, highlighting the benefits and drawbacks of introducing multiport grains and the effect of the oxidizer choice on the motor geometry. Finally, multiport firing tests were carried out to confirm the evidence observed in the simplified single-port campaigns.

LaFe1-xNixO3 perovskites in the catalytic reaction of high-temperature decomposition of nitrous oxide.

The catalytic performance of LaFe1-xNixO3 perovskites prepared by the Pechini method was studied in the high-temperature decomposition reaction of nitrous oxide at temperatures of 750-900 °C. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), adsorption (Sbet) and hydrogen thermo-programmed reduction (H2-TPR) methods. The prepared single-phase solids with specific surface areas of 4.7-8.4 m2 g-1 are porous particles (aggregates) of 10-100 μm composed of microblock crystallites. The surface of all samples is enriched with lanthanum. Increasing the Ni content increases the normalized per m2 catalytic activity of LaFe1-xNixO3 perovskites, their reducibility in hydrogen, the ratio of Fe + Ni/La and the content of low bond oxygen forms on the sample surface. The correlation of activity and low bond oxygen forms was revealed, which is consistent with the mechanism of reaction of nitrous oxide decomposition. For future industrial applications the LaFe0.4Ni0.6O3 perovskite is proposed due to its higher stability in the reaction medium as compared with samples with x > 0.6.

Low-Temperature Synthesis and Catalytic Activity of Cobalt Ferrite in Nitrous Oxide (N2O) Decomposition Reaction

Cobalt ferrite (CoFe2O4) nanoparticles were synthesized and investigated as a catalyst in the reaction of nitrous oxide (N2O) decomposition. Cobalt ferrite was synthesized by solid–phase interaction at 1100 °C and by preliminary mechanochemical activation in a roller-ring vibrating mill at 400 °C. The nanoparticles were characterized by X-ray diffraction (XRD), synchronous thermal analysis (TG and DSC) and scanning electron microscopy (SEM). A low-temperature nitrogen adsorption/desorption test was used to evaluate the catalytic activity of the cobalt ferrite nanoparticles. Correlations between the structure and catalytic properties of the catalysts are reported. The highest catalytic activity of CoFe2O4 in the reaction of nitrous oxide decomposition was 98.1% at 475 °C for cobalt ferrite obtained by mechanochemical activation.

Synthesis of Organic Super-Electron-Donors by Reaction of Nitrous Oxide with N-Heterocyclic Olefins.

The reaction of nitrous oxide (N2O) with N-heterocyclic olefins (NHOs) results in cleavage of the N-O bond and formation of azo-bridged NHO dimers. The latter represent very electron-rich compounds with a low ionization energy. Cyclic voltammetry studies show that the dimers can be classified as new organic super-electron-donors, with a reducing power similar to what is found for tetraazafulvalene derivatives. Mild oxidants are able to convert the neutral dimers into radical cations, which can be isolated. Further oxidation gives stable dications.

Analysis of the potential atmospheric impact of the reaction of N2O with OH

The reaction of nitrous oxide (N2O) with hydroxyl (OH) is studied using high-level quantum chemistry and advanced chemical kinetics techniques. Three reaction mechanisms including a direct O-abstraction, an unusual indirect O-abstraction, and OH-addition/NO-elimination have been characterized. Reaction enthalpies calculated from first principles agree well with those of experiment. Chemical kinetics results show that the title reaction is not a candidate for short or long-time removal of N2O (with an atmospheric lifetime of at least 1 × 1013 years) from the atmosphere but may play a minor role in high-temperature combustion where it may convert N2O pollutants to N2.

Hydrogenation and Hydrosilylation of Nitrous Oxide Homogeneously Catalyzed by a Metal Complex.

Due to its significant contribution to stratospheric ozone depletion and its potent greenhouse effect, nitrous oxide has stimulated much research interest regarding its reactivity modes and its transformations, which can lead to its abatement. We report the homogeneously catalyzed reaction of nitrous oxide (N2O) with H2. The reaction is catalyzed by a PNP pincer ruthenium complex, generating efficiently only dinitrogen and water, under mild conditions, thus providing a green, mild methodology for removal of nitrous oxide. The reaction proceeds through a sequence of dihydrogen activation, “O”-atom transfer, and dehydration, in which metal–ligand cooperation plays a central role. This approach was further developed to catalytic O-transfer from N2O to Si–H bonds.

Reaction of nitrous oxide with methane to synthesis gas: A thermodynamic and catalytic study

The aim of the present study is to explore the coherence of thermodynamic equilibrium predictions with the actual catalytic reaction of CH4 with N2O, particularly at higher CH4 conversions. For this purpose, key process variables, such as temperature (300°C–550°C) and a molar feed ratio (N2O/CH4= 1, 3, and 5), were altered to establish the conditions for maximized H2 yield. The experimental study was conducted over the Co-ZSM-5 catalyst in a fixed bed tubular reactor and then compared with the thermodynamic equilibrium compositions, where the equilibrium composition was calculated via total Gibbs free energy minimization method.The results suggest that molar feed ratio plays an important role in the overall reaction products distribution. Generally for N2O conversions, and irrespective of N2O/CH4 feed ratio, the thermodynamic predictions coincide with experimental data obtained at approximately 475°C–550°C, indicating that the reactions are kinetically limited at lower range of temperatures. For example, theoretical calculations show that the H2 yield is zero in presence of excess N2O (N2O/CH4= 5). However over a Co-ZSM-5 catalyst, and with a same molar feed ratio (N2O/CH4) of 5, the H2 yield is initially 10% at 425°C, while above 450°C it drops to zero. Furthermore, H2 yield steadily increases with temperature and with the level of CH4 conversion for reactions limited by N2O concentration in a reactant feed. The maximum attainable (from thermodynamic calculations and at a feed ratio of N2O/CH4= 3) H2 yield at 550°C is 38%, whereas at same temperature and over Co-ZSM-5, the experimentally observed yield is about 19%.Carbon deposition on Co-ZSM-5 at lower temperatures and CH4 conversion (less than 50%) was also observed. At higher temperatures and levels of CH4 conversion (above 90%), the deposited carbon is suggested to react with N2O to form CO2.

Functionalization of the sumanene by nitrous oxide: A mechanistic study

The mechanistic study of the cycloaddition reaction of nitrous oxide onto sumanene nanostructure carried out systematically using quantum chemistry methods. The 1,3-dipolar cycloaddition reaction of nitrous oxide with different kinds of C–C bond of sumanene in thirteen pathways was investigated. Geometry of reactants, transition states, intermediates and products were optimized at B3LYP/6-311+G(d) level of theory. Vibrational frequencies and relative energies for all stationary points were determined. Thirty-three transition states were identified for all pathways and confirmed by intrinsic reaction coordinate (IRC) calculations. The rate constants for all paths were calculated by using canonical transition state theory (CTST). Results showed that N2O addition to flank position is more favorable than other positions of sumanene, energetically. The major products are sumanene with an epoxide group in flank, spoke and hub6 positions; also products with an enol or oxepin group in rim and hub5 positions, respectively. Also, for all five positions, in the first step, C21H12N2O with a pentagon heterocycle contain O–N–N will be formed. In subsequent steps, either N2 extrusion or rearrangement can be done. Products related to outer positions of sumanene are more stable than corresponding products related to middle positions of sumanene (hub and spoke).

Continuous Thermal Oxidation of Alkenes with Nitrous Oxide in a Packed Bed Reactor

The reaction of nitrous oxide with internal olefins is investigated in a flow reactor. When using a mixture of dodecene isomers, ketones are formed as the primary product with conversions up to 77% and yields up to 45%. The multiphase system is studied experimentally and computationally to gain understanding of the residence time distribution and phase composition. Significant volatility of the dodecenes and solubility of the nitrous oxide result in a system where reaction occurs in both the vapor and liquid at elevated temperatures. The rate constant for oxidation with nitrous oxide is determined by considering both phases and the material transfer between them using 16 different physical parameters through nonlinear optimization. The determined rate constant is in good agreement with parameters estimated by quantum chemistry calculations.

Rate-ratio asymptotic analysis of the structure and mechanisms of extinction of nonpremixed CH4/N2–O2/N2O/N2 flames

Rate-ratio asymptotic analysis is carried out to elucidate the influence of nitrous oxide on the structure and critical conditions for extinction of nonpremixed methane flames. Steady, axisymmetric, laminar flow of two counterflowing streams toward a stagnation plane is considered. One stream is made up of a mixture of methane and nitrogen. The other stream is a mixture of oxygen, nitrous oxide, and nitrogen. A reduced mechanism of five global steps is employed in the analysis. Chemical reactions are presumed to take place in a thin reaction zone that is established in the vicinity of the stagnation plane. On either side of this thin reaction zone, the flow field is inert. These inert regions are called outer zones. Methane and nitrous oxide are completely consumed in the reaction zone, while oxygen is presumed to leak through the reaction zone. In the reaction zone, chemical reactions are presumed to take place in two layers—the inner layer and the oxidation layer. In the inner layer fuel (methane) is consumed and the intermediate species hydrogen and carbon monoxide are formed. These intermediate species are oxidized in the oxidation layer to water vapor and carbon dioxide. Radicals are produced in the oxidation layer from chain-branching reactions that consume hydrogen. Asymptotic analysis gives the scalar dissipation rate at extinction. Critical conditions for extinction predicted by the analysis agree well with previous experimental data. Nitrous oxide is found to have an inhibiting effect on the flame, promoting extinction. The inhibiting effect is attributed to the competition between the net reaction of nitrous oxide with hydrogen to form water vapor and nitrogen and the chain-branching reaction between oxygen and hydrogen that produces radicals.

Collisional Activation of N2O Decomposition and CO Oxidation Reactions on Isolated Rhodium Clusters

The reactions of nitrous oxide decorated rhodium clusters, RhnN2O(+) (n = 5, 6), have been studied by Fourier transform ion cyclotron resonance mass spectrometry. Collision induced dissociation with Ar is shown to lead to one of two processes; desorption of the intact N2O moiety (indicating molecular adsorption in the parent cluster) or N2O decomposition liberating molecular nitrogen with the latter becoming increasingly dominant at higher collision energies. Consistent with the results of earlier studies, which employed infrared excitation [Hermes, A. C.; et al. J. Phys. Chem. Lett. 2011, 2, 3053], Rh5ON2O(+) is observed to behave qualitatively differently to Rh5N2O(+) with decomposition of the nitrous oxide dominating the chemistry of the former. In other experiments, the reactivity of RhnN2O(+) clusters with CO has been studied. Chemisorption of (13)CO is calculated to deposit ca. 2 eV into the parent cluster, initiating a range of chemical processes on the cluster surface, which are fit to a simple reaction mechanism. Clear differences are again observed in the reaction branching ratios for Rh5N2O(+) and Rh6N2O(+) parent cluster ions. For the n = 5 cluster, the combined N2O reduction/CO oxidation is the most significant reaction channel, while the n = 6 cluster preferentially is oxidized to Rh6O(+) with loss of N2 and CO. Even larger differences are observed in the reactions of the N2O decorated cluster oxides, RhnON2O(+), for which more reaction possibilities arise. The results of all studies are discussed in relation to infrared driven processes on the same parent cluster species [Hamilton, S. M.; et al. J. Am. Chem. Soc. 2010, 132, 1448; J. Phys. Chem. A, 2011, 115, 2489].

O-Abstraction Reactions of Nitrous Oxide with Cp2Ti(II) and Other Middle Transition Metal Complexes

DFT calculations have been carried out to study the detailed mechanisms of the O-abstraction reaction of N2O with Cp2Ti(II). The reaction is initiated by coordination of N2O to Cp2Ti via the N-end to form a linear N2O-coordinated species Cp2Ti(N2O), from which the metal center transfers one of its metal d electrons to one π* orbital of the N2O ligand and gives a bent N2O-coordinated intermediate Cp2Ti←N═N−O. The intermediate then reacts barrierlessly with another molecule of Cp2Ti to form an N2O-bridged intermediate Cp2Ti←N═N−O−TiCp2, from which the singly oxo-bridged product (Cp2Ti)2O is formed with a release of N2. Reactions of N2O with other middle transition metal complexes have also been calculated and discussed. General mechanisms for O-abstraction reactions of N2O with early and middle transition metal complexes have been provided.

Theoretical Studies on O-Insertion Reactions of Nitrous Oxide with Ruthenium Hydride Complexes

DFT calculations have been carried out to study the mechanism of the N2O O-insertion into the Ru−H bonds of ruthenium hydride complexes (dmpe)2Ru(H)(X) (X = OH, H). The reaction pathways for the formation of the monoinsertion product (dmpe)2Ru(H)(OH) and the bis(hydroxo) complex (dmpe)2Ru(OH)(OH), which were obtained directly from the reactions of N2O with the ruthenium hydride complexes, have been investigated in detail. Focus has been made to understand how the kinetically inert N2O is activated by the hydride complexes. It is found that N2O is activated through the hydride ligand nucleophilically attacking the terminal nitrogen of N2O followed by coordination of the activated N2O via the O-end.

Kinetic Oscillations During the Catalytic Decomposition of Nitrous Oxide

AbstractFor Abstract see ChemInform Abstract in Full Text.

Kinetic oscillations during the catalytic decomposition of nitrous oxide

This review summarises experimental and modelling studies concerning the development of kinetic oscillations during the catalytic decomposition of nitrous oxide. Oscillations over Cu-ZSM-5 catalysts have been investigated using several methods and it could be shown that the formation of a strongly adsorbed nitrate formed in side reactions and the interaction of this species with atomic oxygen is responsible for the development of kinetic oscillations. The reaction of nitrous oxide over Fe-ZSM-5 catalysts shows similarities to the observations made with Cu-ZSM-5, but kinetic oscillations occur only in the presence of water vapour. On the other hand, isothermal oscillations observed over precious metal catalysts can be explained by an oxidation/reduction mechanism including the restructuring of the active catalyst surface under reaction conditions.

Spectroscopic Properties and Electronic Structure of Pentammineruthenium(II) Dinitrogen Oxide and Corresponding Nitrosyl Complexes: Binding Mode of N2O and Reactivity

The spectroscopic properties and the electronic structure of the only nitrous oxide complex existing in isolated form, [Ru(NH(3))(5)(N(2)O)]X(2) (1, X = Br(-), BF(4)(-)), are investigated in detail in comparison to the nitric oxide precursor, [Ru(NH(3))(5)(NO)]X(3) (2). IR and Raman spectra of 1 and of the corresponding (15)NNO labeled complex are presented and assigned with the help of normal coordinate analysis (NCA) and density functional (DFT) calculations. This allows for the identification of the Ru-N(2)O stretch at approximately 300 cm(-)(1) and for the unambiguous definition of the binding mode of the N(2)O ligand as N-terminal. Obtained force constants are 17.3, 9.6, and 1.4 mdyn/A for N-N, N-O, and Ru-N(2)O, respectively. The Ru(II)-N(2)O bond is dominated by pi back-donation, which, however, is weak compared to the NO complex. This bond is further weakened by Coulomb repulsion between the fully occupied t(2g) shell of Ru(II) and the HOMO of N(2)O. Hence, nitrous oxide is an extremely weak ligand to Ru(II). Calculated free energies and formation constants for [Ru(NH(3))(5)(L)](2+) (L = NNO, N(2), OH(2)) are in good agreement with experiment. The observed intense absorption at 238 nm of 1 is assigned to the t(2g) --> pi(*) charge transfer transition. These data are compared in detail to the spectroscopic and electronic structural properties of NO complex 2. Finally, the transition metal centered reaction of nitrous oxide to N(2) and H(2)O is investigated. Nitrous oxide is activated by back-donation. Initial protonation leads to a weakening of the N-O bond and triggers electron transfer from the metal to the NN-OH ligand through the pi system. The implications of this mechanism for biological nitrous oxide reduction are discussed.

Stable isotope fractionation of nitrous oxide during thermal decomposition and reduction processes

Kinetic isotope effects in nitrous oxide thermal decomposition and reduction reactions were investigated in flowing N2O/He and N2O/He/H2 systems. The intramolecular distribution of stable isotopes, isotopomer, was measured and evaluated using an isotope ratio mass spectrometer equipped with a modified collector system. Thermal decomposition and reduction of nitrous oxide were carried out using a flow tube reactor made of quartz glass in the temperature range of 1173–1373 K. Both thermal decomposition and hydrogen reduction of nitrous oxide proceeded by first‐order kinetics. Isotopomer ratios (δ15Nbulk, δ15Nα, δ15Nβ, and δ18O) of residual nitrous oxide were found to follow a Rayleigh model based on batch distillation. Residual nitrous oxide was depleted slightly in 15N during thermal decomposition but slightly enriched in 15N during hydrogen reduction. Regarding the nitrogen isotopomers, results showed that the central nitrogen atom, Nα, was enriched in 15N during both destruction reactions of nitrous oxide. Although the N2O destruction reactions proceeded at high temperature, large isotopic fractionations of nitrogen isotopomers were observed. Enrichment factors for nitrous oxide as a result of thermal decomposition and reduction reactions were evaluated.

Oxidation of Alkali-Metal Atoms with Nitrous Oxide: Molecular Mechanisms from First Principles Calculations

The reactions of nitrous oxide with alkali-metal atoms were studied theoretically by means of CASSCF(11/12)/MR-MP2 calculations. Critical points on the electronic ground-state 2A‘ potential energy surface (PES) were determined and characterized by harmonic vibrational frequencies at the CASSCF(11/12) level. The molecular mechanism is rather consistent involving in each reaction two distinct entrance channels. Small barriers of 5.9 kcal/mol for Li + N2O, 1.6 kcal/mol for Na + N2O, and 1.2 kcal/mol for K + N2O are predicted for the lower energy reaction channel, which is mainly determined by the NNO bending vibrational mode ν2. These barriers originate as a result of strong avoided crossings between the two lowest 2A‘ PESs that gradually transform the character of the electronic ground state from a neutral to an ionic one in going from reactants to products. Along this channel, the ground-state PES is fairly isolated and the reaction is adiabatic. By way of contrast, the reaction along its higher energy channel occurs via nonadiabatic electron transfer from alkali metal to N2O in the region of the 12A‘/22A‘ conical intersection and likely contributes to the observed non-Arrhenius behavior of the reaction rates. These findings provide clarifying insights into the nature of a number of previous kinetic and spectroscopic observations.