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1
Lee, Sang Ji, Jae Geun Yun, Han Min Lee, Ji Yeop Kim, Jin Han Yun, and Jung Goo Hong. "Dependence of N2O/NO Decomposition and Formation on Temperature and Residence Time in Thermal Reactor." Energies 14, no. 4 (February 22, 2021): 1153. http://dx.doi.org/10.3390/en14041153.
Повний текст джерелаАнотація:
Nitrogen dioxide (N2O) is a greenhouse gas that is harmful to the ozone layer and contributes to global warming. Many other nitrogen oxide emissions are controlled using the selective non-catalytic reaction (SNCR) process, but N2O reduction methods are few. To avoid future air pollution problems, N2O reduction from industrial sources is essential. In this study, a N2O decomposition and NO formation under an argon atmospheric N2O gas mixture were observed in a lab-scale SNCR system. The reaction rate and mechanism of N2O were calculated using a reaction path analyzer (CHEMKIN-PRO). The residence time of the gas mixture and the temperature in the reactor were set as experimental variables. The results confirmed that most of the N2O was converted to N2 and NO. The change in the N2O reduction rate increased with the residence time at 1013 and 1113 K, but decreased at 1213 K due to the inverse reaction. NO concentration increased with the residence time at 1013 and 1113 K, but decreased at 1213 K owing to the conversion of NO back to N2O.
2
Sheldon, JC, RAJ Ohair, KM Downard, S. Gronert, M. Krempp, CH Depuy, and JH Bowie. "A Potential Surface Map of the H-/N2O System. The Gas Phase Ion Chemistry of HN2O-." Australian Journal of Chemistry 48, no. 2 (1995): 155. http://dx.doi.org/10.1071/ch9950155.
Повний текст джерелаАнотація:
Dunkin, Fehsenfeld and Ferguson have reported that the gas phase reaction between H- and N2O in a flowing afterglow instrument forms HO- and N2 with medium efficiency. The potential surface (UMP2-FC/6-311++G**//RHF/6-311++G**) for the H-/N2O system confirms this to be the predominant reaction following initial approach of H- towards the central nitrogen of N2O to form unstable intermediate [H-(N2O)]. The intermediate then decomposes to HO- and N2 via a deep channel. The potential surface also shows the direct formation of adducts -O-+N(H)=N- and cis HN=NO-. However, these are formed with excess energy: the former converts principally into reactants, while the latter decomposes to HO- and N2. Ions having the formula 'HN2O-' may be formed in the gas phase by the reactions ( i ) HNO-+N2O → HN2O-+NO, and (ii) NH2-+Me3CCH2ONO → HN2O-+Me3CCH2OH. The product anion is stabilized by removal of some of its excess energy by the eliminated neutral. Evidence is presented which indicates that the product is either cis or trans HN=NO-, or a mixture of both. The characteristic ion molecule reaction of HN=NO- involves oxidative oxygen transfer to suitable neutral substrates. For example: HN2O-+CS2 → HS-+N2+COS.
3
Smith, D. M., W. F. Welch, S. M. Graham, A. R. Chughtai, Brian G. Wicke, and Karen A. Grady. "Reaction of Nitrogen Oxides with Black Carbon: An FT-IR Study." Applied Spectroscopy 42, no. 4 (May 1988): 674–80. http://dx.doi.org/10.1366/0003702884429247.
Повний текст джерелаАнотація:
Qualitative and quantitative studies of the reaction of black carbon with the oxides of nitrogen, including NO, NO2/N2O4, N2O, and N2O3, have been carried out with the use of Fourier transform infrared spectroscopy (FT-IR). The active reactant is shown to be NO2, whether it acts as a disproportionation product or as an impurity in the gas under study. FT-IR spectra of the surface species identify them as resulting from reaction of carbon with NO2. For paraffin candle soot which was exposed simultaneously to oxygen atoms, and nitric oxide at 298 K, the surface species also are due to NO2, formed by oxidative adsorption of NO on the soot surface.
4
Li, Songfeng, Chunhua Zhang, Ao Zhou, Yangyang Li, Peng Yin, Chunfang Mu, and Jinyuan Xu. "Experimental and kinetic modeling study for N2O formation of NH3-SCR over commercial Cu-zeolite catalyst." Advances in Mechanical Engineering 13, no. 4 (April 2021): 168781402110106. http://dx.doi.org/10.1177/16878140211010648.
Повний текст джерелаАнотація:
In this paper, a systematic experimental and kinetic model investigation was conducted over Cu-SSZ-13 catalyst to study the DeNOx efficiency and N2O formation for selective catalytic reduction of NOx with NH3 (NH3-SCR). The kinetic model was developed for various reactions to take place in the NH3-SCR system, including NH3 adsorption/desorption, NH3 oxidation, NO oxidation, standard SCR, fast SCR, slow SCR and N2O formation reactions. In addition, the reaction of N2O formation from NH3 non-selective oxidation was taken into account. All the experiments were performed in a flow reactor with a feed stream near to the real application of diesel engine vehicles exhaust. The current model can satisfactorily predict the steady state conversion rate of various species at the reactor outlet and the effect of gas hourly space velocities and ammonia nitrogen ratio on N2O formation. The results show that the kinetic model can simulate the reaction process of the Cu-SSZ-13 catalyst well. This is significant for the optimization of NH3-SCR system for achieving the higher DeNOx efficiency and the lower N2O emission.
5
Yamazaki, T., T. Hozuki, K. Arai, S. Toyoda, K. Koba, T. Fujiwara, and N. Yoshida. "Isotopomeric characterization of nitrous oxide produced by reaction of enzymes extracted from nitrifying and denitrifying bacteria." Biogeosciences 11, no. 10 (May 21, 2014): 2679–89. http://dx.doi.org/10.5194/bg-11-2679-2014.
Повний текст джерелаАнотація:
Abstract. Nitrous oxide (N2O) is a potent greenhouse gas and produced in denitrification and nitrification by various microorganisms. Site preference (SP) of 15N in N2O, which is defined as the difference in the natural abundance of isotopomers 14N15NO and 15N14NO relative to 14N14NO, has been reported to be a useful tool to quantitatively distinguish N2O production pathways. To determine representative SP values for each microbial process, we firstly measured SP of N2O produced in the enzyme reaction of hydroxylamine oxidoreductase (HAO) purified from two species of ammonia oxidizing bacteria (AOB), Nitrosomonas europaea and Nitrosococcus oceani, and that of nitric oxide reductase (NOR) from Paracoccus denitrificans. The SP value for NOR reaction (−5.9 ± 2.1‰) showed nearly the same value as that reported for N2O produced by P. denitrificans in pure culture. In contrast, SP value for HAO reaction (36.3 ± 2.3‰) was a little higher than the values reported for N2O produced by AOB in aerobic pure culture. Using the SP values obtained by HAO and NOR reactions, we calculated relative contribution of the nitrite (NO2–) reduction (which is followed by NO reduction) to N2O production by N. oceani incubated under different O2 availability. Our calculations revealed that previous in vivo studies might have underestimated the SP value for the NH2OH oxidation pathway possibly due to a small contribution of NO2– reduction pathway. Further evaluation of isotopomer signatures of N2O using common enzymes of other processes related to N2O would improve the isotopomer analysis of N2O in various environments.
6
Yamaguchi, Naoya, Eichi Nagatomi, Takahiro Kato, Koichiro Ohishi, Yasuhiro Tamayama, and Kanji Yasui. "Effects of N2O addition on the properties of ZnO thin films grown using high-temperature H2O generated by catalytic reaction." MRS Proceedings 1633 (2014): 61–67. http://dx.doi.org/10.1557/opl.2014.20.
Повний текст джерелаАнотація:
ABSTRACTThe effects of N2O gas addition on the properties of zinc oxide films grown on a-plane (11-20) sapphire (a-Al2O3) substrates were investigated, using a chemical vapor deposition method based on the reaction between dimethylzinc and high-energy H2O produced by a Pt-catalyzed H2-O2 reaction. By employing an optimal N2O gas pressure, both the film crystallinity and crystal orientation were improved. Subsequent to treatment with N2O, the electron mobility of films at room temperature increased from 207 to 234 cm2/Vs while the electron concentration decreased at low temperatures. In addition, the photoluminescence peak intensity of the nearband-edge emission was increased.
7
Yamazaki, T., T. Hozuki, K. Arai, S. Toyoda, K. Koba, T. Fujiwara, and N. Yoshida. "Isotopomeric characterization of nitrous oxide produced by reaction of enzymes extracted from nitrifying and denitrifying bacteria." Biogeosciences Discussions 10, no. 10 (October 25, 2013): 16615–43. http://dx.doi.org/10.5194/bgd-10-16615-2013.
Повний текст джерелаАнотація:
Abstract. Nitrous oxide (N2O) is a potent greenhouse gas and produced in denitrification and nitrification in environmental nitrogen cycle by various microorganism. Site preference (SP) of 15N in N2O, which is defined as the difference in the natural abundance of isotopomers 14N15NO and 15N14NO relative to 14N14NO, has been reported to be a useful tool to quantitatively distinguish N2O production pathway. To determine representative SP value for each microbial process, we firstly measured SP of N2O produced in the enzyme reaction of hydroxylamine oxidoreductase (HAO) purified from two species of ammonia oxidizing bacteria (AOB), Nitrosomonas europaea and Nitrosococcus oceani, and that of nitric oxide reductase (NOR) from Paracoccus denitrificans, respectively. The SP value for NOR reaction (−5.9 ± 2.1‰) showed nearly the same value as that reported for N2O produced by P. denitrificans in pure culture. In contrast, SP value for HAO reaction (36.3 ± 2.3‰) was a little higher than the values reported for N2O produced by AOB in aerobic pure culture. Using the SP values obtained by HAO and NOR reactions, we calculated relative contribution of the nitrite (NO2–) reduction (which is followed by NO reduction) to N2O production by N. oceani incubated under different O2 availability. Our calculations revealed that previous in vivo studies might have underestimated the SP value for NH2OH oxidation pathway possibly due to a small contribution of NO2– reduction pathway. Further evaluation of isotopomer signatures of N2O using common enzymes of other processes related to N2O would improve the isotopomer analysis of N2O in various environments.
8
Bennett, Sophie P., Maria J. Torres, Manuel J. Soriano-Laguna, David J. Richardson, Andrew J. Gates, and Nick E. Le Brun. "nosX is essential for whole-cell N2O reduction in Paracoccus denitrificans but not for assembly of copper centres of nitrous oxide reductase." Microbiology 166, no. 10 (October 1, 2020): 909–17. http://dx.doi.org/10.1099/mic.0.000955.
Повний текст джерелаАнотація:
Nitrous oxide (N2O) is a potent greenhouse gas that is produced naturally as an intermediate during the process of denitrification carried out by some soil bacteria. It is consumed by nitrous oxide reductase (N2OR), the terminal enzyme of the denitrification pathway, which catalyses a reduction reaction to generate dinitrogen. N2OR contains two important copper cofactors (CuA and CuZ centres) that are essential for activity, and in copper-limited environments, N2OR fails to function, contributing to rising levels of atmospheric N2O and a major environmental challenge. Here we report studies of nosX, one of eight genes in the nos cluster of the soil dwelling α-proteobaterium Paraccocus denitrificans. A P. denitrificans ΔnosX deletion mutant failed to reduce N2O under both copper-sufficient and copper-limited conditions, demonstrating that NosX plays an essential role in N2OR activity. N2OR isolated from nosX-deficient cells was found to be unaffected in terms of the assembly of its copper cofactors, and to be active in in vitro assays, indicating that NosX is not required for the maturation of the enzyme; in particular, it plays no part in the assembly of either of the CuA and CuZ centres. Furthermore, quantitative Reverse Transcription PCR (qRT-PCR) studies showed that NosX does not significantly affect the expression of the N2OR-encoding nosZ gene. NosX is a homologue of the FAD-binding protein ApbE from Pseudomonas stutzeri , which functions in the flavinylation of another N2OR accessory protein, NosR. Thus, it is likely that NosX is a system-specific maturation factor of NosR, and so is indirectly involved in maintaining the reaction cycle of N2OR and cellular N2O reduction.
9
Cao, Xuesong, Chenxi Zhang, Zehua Wang, and Xiaomin Sun. "Catalytic Reaction Mechanism of NO–CO on the ZrO2 (110) and (111) Surfaces." International Journal of Molecular Sciences 20, no. 24 (December 5, 2019): 6129. http://dx.doi.org/10.3390/ijms20246129.
Повний текст джерелаАнотація:
Due to the large population of vehicles, significant amounts of carbon monoxide (CO), nitrogen oxides (NOx), and unburned hydrocarbons (HC) are emitted into the atmosphere, causing serious pollution to the environment. The use of catalysis prevents the exhaust from entering the atmosphere. To better understand the catalytic mechanism, it is necessary to establish a detailed chemical reaction mechanism. In this study, the adsorption behaviors of CO and NO, the reaction of NO reduction with CO on the ZrO2 (110) and (111) surfaces was performed through periodic density functional theory (DFT) calculations. The detailed mechanism for CO2 and N2 formation mainly involved two intermediates N2O complexes and NCO species. Moreover, the existence of oxygen vacancies was crucial for NO reduction reactions. From the calculated energy, it was found that the pathway involving NCO intermediate interaction occurring on the ZrO2 (110) surface was most favorable. Gas phase N2O formation and dissociation were also considered in this study. The results indicated the role of reaction intermediates NCO and N2O in catalytic reactions, which could solve the key scientific problems and disputes existing in the current experiments.
10
Takatsu, Yuta, Sharon Y. L. Lau, Li Li, and Yasuyuki Hashidoko. "Effects of Some Hill Reaction-Inhibiting Herbicides on Nitrous Oxide Emission from Nitrogen-Input Farming Soil." Applied Sciences 9, no. 9 (May 9, 2019): 1903. http://dx.doi.org/10.3390/app9091903.
Повний текст джерелаАнотація:
Nitrous oxide (N2O) emission-suppressing activity of some electron-transport inhibitors of the Hill reaction system was investigated. The Hill reaction inhibitors—paraquat, isouron, bromacil, diquat, and simazine—all of which have been or are currently being used as herbicides in farming activity are expected to inhibit the electron-transporting pathways of nitrate respiration in denitrifying bacteria. Using N2O-emitting soil bed (5.0 g of fresh weight) from a continuously manured Andisol corn farmland in Hokkaido, Japan, which was autoclaved and further supplemented with an active N2O-emitter, Pseudomonas sp. 5CFM15-6D, and 1 mL of 100 mM NH4NO3 or (NH4)2SO4 solution as the sole nitrogen source (final concentration, 0.2 mM) in a 30 mL gas-chromatography vial, the effects of the five herbicides on N2O emission were examined. Paraquat and isouron (each at 50 µM) showed a statistically significant suppression of N2O emission in both the nitrification and the denitrification processes after a 7-day-incubation, whereas diquat at the same concentration accelerated N2O emission in the presence of NO3−. These results suggest that paraquat and isouron inhibited both the nitrification and the denitrification processes for N2O generation, or its upstream stages, whereas diquat specifically inhibited N2O reductase, an enzyme that catalyzes the reduction of N2O to N2 gas. Incomplete denitrifiers are the key players in the potent emission of N2O from Andisol corn farmland soil because of the missing nosZ gene. The electron relay system-inhibiting herbicides—paraquat and isouron—possibly contribute to the prevention of denitrification-induced nitrogen loss from the farming soil.
11
Gao, Congru, Jianwei Li, Jie Zhang, and Xiuliang Sun. "DFT Study on the Combined Catalytic Removal of N2O, NO, and NO2 over Binuclear Cu-ZSM-5." Catalysts 12, no. 4 (April 13, 2022): 438. http://dx.doi.org/10.3390/catal12040438.
Повний текст джерелаАнотація:
The large amount of nitrogen oxides (N2O, NO, NO2, etc.) contained in the flue gas of industrial adipic acid production will seriously damage the environment. A designed binuclear Cu-ZSM-5 catalyst can be applied to decompose N2O and reduce NO and NO2, purifying the air environment. Using the density functional theory method, the catalytic decomposition mechanisms of N2O, NOX-NH3-SCR, and NOX-assisted N2O decomposition is simulated over the Cu-ZSM-5 model. The results indicate that N2O can be catalytically decomposed over the binuclear Cu active site in the sinusoidal channel. The speed-limiting step is the second N2O molecule activation process. After the decomposition of the first N2O molecule, a stable extra-frame [Cu-O-Cu]2+ structure will generate. The subsequent discussion proved that the NOX-NH3-SCR reaction can be realized over the [Cu-O-Cu]2+ active site. In addition, it proved that the decomposition reaction of NO and NO2 can be carried out over the [Cu-O-Cu]2+ active site, and NO can greatly reduce the energy barrier for the conversion of the active site from [Cu-O-Cu]2+ to the binuclear Cu form, while NO2 can be slightly reduced. Through discussion, it is found that the binuclear Cu-ZSM-5 can realize the combined removal of N2O and NOX from adipic acid flue gas, hoping to provide a theoretical basis for the development of a dual-functional catalyst.
12
Nováková, Jana, and Ludmila Kubelková. "N2O in NO Reduction by CO Over Pt/NaX Zeolite." Collection of Czechoslovak Chemical Communications 62, no. 2 (1997): 299–308. http://dx.doi.org/10.1135/cccc19970299.
Повний текст джерелаАнотація:
Pt/NaX zeolite (3 Pt atoms per unit cell) was prepared by vacuum decomposition of [Pt(NH3)4]2+. NO + 13CO and N2O + 13CO reactions were studied under static conditions at 180, 205 and 230 °C and followed by temperature programmed desorption (TPD) of surface species adsorbed in zeolites during the reaction. The effect of different NO/CO ratios and of the added oxygen was examined for the former reaction. The experimental results agree with the assumption that N2O (and 13CO2) is (are) the primary product(s) released into the gaseous phase below 230 °C; above 205 °C, the complete reduction to N2 occurs. N2O could be a very rapidly decomposing surface intermediate for this complete reduction, and can act together with the recombination of N atoms. Nitrous oxide released into the gas phase cannot serve as the reaction intermediate, because its reduction by CO proceeds much more slowly than that of NO. The formation of nitrous oxide in the NO + CO reaction is, in addition to low temperatures, enhanced by the increased NO/CO ratio and by the presence of oxygen. The latter effect can be due to the occupation of Pt active sites by adsorbed oxygen and/or by the oxidation of NO to higher oxides which decompose, yielding N2O (together with NO and oxygen).
13
Liang, Jun-Xi, Zhi-Yuan Geng, Yong-Cheng Wang, Yan-Xia Han, and Peng-Ji Yan. "Theoretical study on reaction of with N2O in gas phase." Journal of Molecular Structure: THEOCHEM 859, no. 1-3 (June 2008): 79–85. http://dx.doi.org/10.1016/j.theochem.2008.03.008.
Повний текст джерела
14
Pan, James J., Donald J. Arseneau, Masayoshi Senba, Mee Shelly, and Donald G. Fleming. "Reaction Kinetics of Muonium with N2O in the Gas Phase." Journal of Physical Chemistry A 101, no. 45 (November 1997): 8470–79. http://dx.doi.org/10.1021/jp971677k.
Повний текст джерела
15
Haslun, Joshua A., Nathaniel E. Ostrom, Eric L. Hegg, and Peggy H. Ostrom. "Estimation of isotope variation of N<sub>2</sub>O during denitrification by <i>Pseudomonas aureofaciens</i> and <i>Pseudomonas chlororaphis</i>: implications for N<sub>2</sub>O source apportionment." Biogeosciences 15, no. 12 (June 27, 2018): 3873–82. http://dx.doi.org/10.5194/bg-15-3873-2018.
Повний текст джерелаАнотація:
Abstract. Soil microbial processes, stimulated by agricultural fertilization, account for 90 % of anthropogenic nitrous oxide (N2O), the leading source of ozone depletion and a potent greenhouse gas. Efforts to reduce N2O flux commonly focus on reducing fertilization rates. Management of microbial processes responsible for N2O production may also be used to reduce N2O emissions, but this requires knowledge of the prevailing process. To this end, stable isotopes of N2O have been applied to differentiate N2O produced by nitrification and denitrification. To better understand the factors contributing to isotopic variation during denitrification, we characterized the δ15N, δ18O and site preference (SP; the intramolecular distribution of 15N in N2O) of N2O produced during NO3- reduction by Pseudomonas chlororaphis subsp. aureofaciens and P. c. subsp. chlororaphis. The terminal product of denitrification for these two species is N2O because they lack the gene nitrous oxide reductase, which is responsible for the reduction of N2O to N2. In addition to species, treatments included electron donor (citrate and succinate) and electron donor concentration (0.01, 0.1, 1 and 10 mM) as factors. In contrast to the expectation of a Rayleigh model, all treatments exhibited curvilinear behaviour between δ15N or δ18O and the extent of the reaction. The curvilinear behaviour indicates that the fractionation factor changed over the course of the reaction, something that is not unexpected for a multi-step process such as denitrification. Using the derivative of the equation, we estimated that the net isotope effects (η) vary by as much as 100 ‰ over the course of a single reaction, presenting challenges for using δ15N and δ18O as apportionment tools. In contrast, SP for denitrification was not affected by the extent of the reaction, the electron donor source or concentration, although the mean SP of N2O produced by each species differed. Therefore, SP remains a robust indicator of the origin of N2O. To improve apportionment estimates with SP, future studies could evaluate other factors that contribute to the variation in SP.
16
Su, Ya Xin, and Cui Wu Chen. "Numerical Study on NO Mechanism during High Temperature Air Combustion of Natural Gas." Applied Mechanics and Materials 190-191 (July 2012): 609–14. http://dx.doi.org/10.4028/www.scientific.net/amm.190-191.609.
Повний текст джерелаАнотація:
A full nitric oxide mechanism including thermal NO, prompt NO, N2O intermediate model and NO reduction model through reburning was used to calculate the NO formation during high temperature air combustion of natural gas in industrial furnace. The turbulent transportation was simulated by Reynolds stress model (RSM) and a modified Eddy-Break-Up (EBU) combustion model was applied to model the combustion process. A three-step reaction scheme of the natural gas combustion reaction was considered. Experimental data from published literature was adopted to validate the present models. Numerical results showed that thermal NO formation mechanism and reburning NO reduction mechanism were the dominant NO models. Reburning NO reduction could not be ignored. Prompt NO gave a small contribution to NO emission and the N2O intermediate model for NO formation was of little importance.
17
Arseneau, D. J., D. G. Fleming, M. Senba, I. D. Reid, and D. M. Garner. "The ion–molecule reactivity of the positive muon molecular ions HeMu+ and NeMu+." Canadian Journal of Chemistry 66, no. 8 (August 1, 1988): 2018–24. http://dx.doi.org/10.1139/v88-325.
Повний текст джерелаАнотація:
Thermal (300 K) ion–molecule reaction rates are measured, using the µSR (muon spin rotation) technique, for the muonated rare gas molecular ions HeMu+ and NeMu+ reacting with NO, O2, N2O, NH3, CF4, C2H4, TMS, and CH3NO2. In almost every case (excepting O2), both charge transfer (ke) and muon transfer (kµ) contribute to the reaction rate. Reaction is believed to occur from ro-vibrational excited states, [HeMu+]* and [NeMu+]*, due to the poor efficiency of He and Ne moderators for collisional deactivation. The total experimental rate constants, kexp = kµ + ke, are generally in excellent agreement with total capture rates predicted by the simple ADO theory, regardless of the degree of internal excitation. Comparisons with literature values for corresponding protonated ion reaction rates with O2 and C2H4 reveal little or no isotope effect, although it is noted that these reactions are dominated by proton transfer, in contrast to the µSR results.
18
Wartha, C., F. Winter, and H. Hofbauer. "The Trade-Off Between N2, NO, and N2O Under Fluidized Bed Combustor Conditions." Journal of Energy Resources Technology 122, no. 2 (March 31, 2000): 94–100. http://dx.doi.org/10.1115/1.483169.
Повний текст джерелаАнотація:
NO and N2O are harmful pollutants. Under fluidized bed combustor conditions, the nitrogen of the solid fuel is partly converted to these species. The trade-off between N2, NO, and N2O depends on the fuel and fuel characteristics, the complex homogeneous and heterogeneous formation and destruction paths, temperature and residence times, and so forth. Because of these complex interrelations, it is necessary to study these processes separately and to analyze their relative importance. To obtain a better understanding of the formation and destruction paths of NO and N2O, comprehensive studies have been performed in a laboratory-scale fluidized bed reactor optimized to obtain formation rates. The influence of the temperature and radicals on the NO and N2O formation from HCN and NH3 and destruction reactions were studied. The results show that N2O is formed only from HCN. Oxidation of NH3 forms NO and N2, HCN forms NO, N2O, and N2. Typically, 30 to 70 percent of NH3 are converted to N2, depending on bed temperature. In the case of HCN, only 5 to 25 percent are converted to N2. At temperatures below 800°C, NO reacts with CH4 oxidation products to NO2. Tests with HCN show that HCN conversion starts already at 700°C in the fluidized bed, N2O is formed in significant amounts only in the presence of CH4. The results of the NO and N2O destruction tests show that the thermal mechanism is of minor importance. At 900°C, N2O destruction with H radicals can be seen. N2O formation shows a maximum at 850°C. The gas reaction studies were used to understand the NH3, HCN, NO, and N2O single-particle formation characteristics of coke, bituminous coal, peat, and spruce wood under fluidized bed combustor conditions. [S0195-0738(00)00702-0]
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Gil-Loaiza, Juliana, Joseph R. Roscioli, Joanne H. Shorter, Till H. M. Volkmann, Wei-Ren Ng, Jordan E. Krechmer, and Laura K. Meredith. "Versatile soil gas concentration and isotope monitoring: optimization and integration of novel soil gas probes with online trace gas detection." Biogeosciences 19, no. 1 (January 10, 2022): 165–85. http://dx.doi.org/10.5194/bg-19-165-2022.
Повний текст джерелаАнотація:
Abstract. Gas concentrations and isotopic signatures can unveil microbial metabolisms and their responses to environmental changes in soil. Currently, few methods measure in situ soil trace gases such as the products of nitrogen and carbon cycling or volatile organic compounds (VOCs) that constrain microbial biochemical processes like nitrification, methanogenesis, respiration, and microbial communication. Versatile trace gas sampling systems that integrate soil probes with sensitive trace gas analyzers could fill this gap with in situ soil gas measurements that resolve spatial (centimeters) and temporal (minutes) patterns. We developed a system that integrates new porous and hydrophobic sintered polytetrafluoroethylene (sPTFE) diffusive soil gas probes that non-disruptively collect soil gas samples with a transfer system to direct gas from multiple probes to one or more central gas analyzer(s) such as laser and mass spectrometers. Here, we demonstrate the feasibility and versatility of this automated multiprobe system for soil gas measurements of isotopic ratios of nitrous oxide (δ18O, δ15N, and the 15N site preference of N2O), methane, carbon dioxide (δ13C), and VOCs. First, we used an inert silica matrix to challenge probe measurements under controlled gas conditions. By changing and controlling system flow parameters, including the probe flow rate, we optimized recovery of representative soil gas samples while reducing sampling artifacts on subsurface concentrations. Second, we used this system to provide a real-time window into the impact of environmental manipulation of irrigation and soil redox conditions on in situ N2O and VOC concentrations. Moreover, to reveal the dynamics in the stable isotope ratios of N2O (i.e., 14N14N16O, 14N15N16O, 15N14N16O, and 14N14N18O), we developed a new high-precision laser spectrometer with a reduced sample volume demand. Our integrated system – a tunable infrared laser direct absorption spectrometry (TILDAS) in parallel with Vocus proton transfer reaction mass spectrometry (PTR-MS), in line with sPTFE soil gas probes – successfully quantified isotopic signatures for N2O, CO2, and VOCs in real time as responses to changes in the dry–wetting cycle and redox conditions. Broadening the collection of trace gases that can be monitored in the subsurface is critical for monitoring biogeochemical cycles, ecosystem health, and management practices at scales relevant to the soil system.
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Ambrožová, Nela, Miroslava Edelmannová, Ivana Troppová, Kamila Kocí, and Marta Valášková. "Photocatalytic Decomposition of N2O Over Ceramics Cordierite/CeO2 Nanoparticles." Journal of Nanoscience and Nanotechnology 19, no. 11 (November 1, 2019): 7339–44. http://dx.doi.org/10.1166/jnn.2019.15840.
Повний текст джерелаАнотація:
The study is focused on the testing of the photocatalytic ability to decompose nitrous oxide (N2O) over cordierite/CeO2 nanoparticles ceramic photocatalysts. The activity of ceramic materials was compared with the activity of industrially produced TiO2 (Evonik photocatalyst). Photocatalytic decomposition of N2O over the ceramic samples and the TiO2 Evonik was performed in annular batch reactor illuminated with 8 W Hg lamp (λ ═ 254 nm wavelength). Reaction kinetics was well described by pseudo 1st rate law. Photocatalytic activity of cordierite/CeO2 was better in comparison with TiO2 Evonik P25. The highest N2O conversion (56%) after 20 h of irradiation in inert gas was achieved over the sample with higher amount of CeO2. This photocatalyst sample was examined for photocatalytic activity in the decomposition of N2O in the three various gaseous feed mixtures. The gaseous feed mixtures were: N2O enriched with O2 (6.5 mol.%); N2O enriched with H2O(25 mol.%) and N2O enriched with mixture of O2 and H2O(6.5 mol.% and 25 mol.%, respectively). It is assumed that the reduced conversion of N2O (47%) observed in the flow of the mixture of N2O and H2Ocould be affected by the sorption of water vapor on/onto the photocatalyst “active sites” causing less penetration of light and thus reducing the efficiency of photocatalytic decomposition of N2O. The presence of oxygen in the N2O mixture had only little effect to photocatalytic decomposition of N2O.
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Li, Tao Hong, Chuan Ming Wang, Shi Wen Yu, Xiang Yi Liu, Hui Fu, and Xiao Guang Xie. "A computational study on the gas phase reaction of Os+ with N2O." Chinese Chemical Letters 20, no. 8 (August 2009): 1010–14. http://dx.doi.org/10.1016/j.cclet.2009.03.007.
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LIANG, Junxi, Zhiyuan GENG, and Yongcheng WANG. "Theoretical Study on Reaction of Furan Anion with N2O in Gas Phase." Chinese Journal of Chemistry 27, no. 7 (July 2009): 1261–68. http://dx.doi.org/10.1002/cjoc.200990211.
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Meloni, Eugenio, Marco Martino, Simona Renda, Olga Muccioli, Pluton Pullumbi, Federico Brandani, and Vincenzo Palma. "Development of Innovative Structured Catalysts for the Catalytic Decomposition of N2O at Low Temperatures." Catalysts 12, no. 11 (November 10, 2022): 1405. http://dx.doi.org/10.3390/catal12111405.
Повний текст джерелаАнотація:
Nitrous oxide (N2O), produced from several human activities, is considered a greenhouse gas with significant environmental impacts. The most promising abatement technology consists of the catalytic decomposition of N2O into nitrogen and oxygen. Many recently published papers dealing with N2O catalytic decomposition over Ni-substituted Co3O4 are related to the treatment of N2O concentrations less than 2 vol% in the feed stream. The present work is focused on developing catalysts active in the presence of a gaseous stream richer in N2O, up to 20 vol%, both as powder and in structured configurations suitable for industrial application. With this aim, different nickel-cobalt mixed oxides (NixCo1−xCo2O4) were prepared, characterized, and tested. Subsequently, since alumina-based slurries assure successful deposition of the catalytic species on the structured carrier, a screening was performed on three nickel-cobalt-alumina mixed oxides. As the latter samples turned out to be excellent catalysts for the N2O decomposition reaction, the final catalytic formulation was transferred to a silicon carbide monolith. The structured catalyst led to the following very promising results: total N2O conversion and selectivity towards N2 and O2 were reached at 510 °C by feeding 20 vol% of N2O. It represents an important achievement in the view of developing a more concretely applicable catalytic system for industrial processes.
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Humbert, Guillaume, Mathieu Sébilo, Justine Fiat, Longqi Lang, Ahlem Filali, Véronique Vaury, Mathieu Spérandio, and Anniet M. Laverman. "Isotopic evidence for alteration of nitrous oxide emissions and producing pathways' contribution under nitrifying conditions." Biogeosciences 17, no. 4 (February 24, 2020): 979–93. http://dx.doi.org/10.5194/bg-17-979-2020.
Повний текст джерелаАнотація:
Abstract. Nitrous oxide (N2O) emissions from a nitrifying biofilm reactor were investigated with N2O isotopocules. The nitrogen isotopomer site preference of N2O (15N-SP) indicated the contribution of producing and consuming pathways in response to changes in oxygenation level (from 0 % to 21 % O2 in the gas mix), temperature (from 13.5 to 22.3 ∘C) and ammonium concentrations (from 6.2 to 62.1 mg N L−1). Nitrite reduction, either nitrifier denitrification or heterotrophic denitrification, was the main N2O-producing pathway under the tested conditions. Difference between oxidative and reductive rates of nitrite consumption was discussed in relation to NO2- concentrations and N2O emissions. Hence, nitrite oxidation rates seem to decrease as compared to ammonium oxidation rates at temperatures above 20 ∘C and under oxygen-depleted atmosphere, increasing N2O production by the nitrite reduction pathway. Below 20 ∘C, a difference in temperature sensitivity between hydroxylamine and ammonium oxidation rates is most likely responsible for an increase in N2O production via the hydroxylamine oxidation pathway (nitrification). A negative correlation between the reaction kinetics and the apparent isotope fractionation was additionally shown from the variations of δ15N and δ18O values of N2O produced from ammonium. The approach and results obtained here, for a nitrifying biofilm reactor under variable environmental conditions, should allow for application and extrapolation of N2O emissions from other systems such as lakes, soils and sediments.
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Ma, Li, Hua Lin, Xiabing Xie, Minhan Dai, and Yao Zhang. "Major role of ammonia-oxidizing bacteria in N<sub>2</sub>O production in the Pearl River estuary." Biogeosciences 16, no. 24 (December 16, 2019): 4765–81. http://dx.doi.org/10.5194/bg-16-4765-2019.
Повний текст джерелаАнотація:
Abstract. Nitrous oxide (N2O) has significant global warming potential as a greenhouse gas. Estuarine and coastal regimes are the major zones of N2O production in the marine system. However, knowledge on biological sources of N2O in estuarine ecosystems remains controversial but is of great importance for understanding global N2O emission patterns. Here, we measured concentrations and isotopic compositions of N2O as well as distributions of ammonia-oxidizing bacterial and archaeal amoA and denitrifier nirS genes by quantitative polymerase chain reaction along a salinity gradient in the Pearl River estuary, and we performed in situ incubation experiments to estimate N2O yields. Our results indicated that nitrification predominantly occurred, with significant N2O production during ammonia oxidation. In the hypoxic waters of the upper estuary, strong nitrification resulted in the observed maximum N2O and ΔN2Oexcess concentrations, although minor denitrification might be concurrent at the site with the lowest dissolved oxygen. Ammonia-oxidizing β-proteobacteria (AOB) were significantly positively correlated with all N2O-related parameters, although their amoA gene abundances were distinctly lower than ammonia-oxidizing archaea (AOA) throughout the estuary. Furthermore, the N2O production rate and the N2O yield normalized to amoA gene copies or transcripts estimated a higher relative contribution of AOB to the N2O production in the upper estuary. Taken together, the in situ incubation experiments, N2O isotopic composition and concentrations, and gene datasets suggested that the high concentration of N2O (oversaturated) is mainly produced from strong nitrification by the relatively high abundance of AOB in the upper reaches and is the major source of N2O emitted to the atmosphere in the Pearl River estuary.
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Dvořák, Bohumír, Antonín Hudec, and Josef Pašek. "Measurements of specific copper surface area by a pulse chromatographic technique." Collection of Czechoslovak Chemical Communications 54, no. 6 (1989): 1514–29. http://dx.doi.org/10.1135/cccc19891514.
Повний текст джерелаАнотація:
The method for determination of specific copper area by decompositive adsorption of N2O has been investigated using pulse chromatographic technique. The reaction is accompanied by activated adsorption of oxygen. The amount of oxygen adsorbed depends linearly upon the temperature in the range of -20 to +90 °C. The existence of an oxygen monolayer in the temperature range from 90 to 120 °C has been proved. On the surface, the Cu:O ratio is equal to 2. The rate of decompositive N2O adsorption is very high. The weakly bonded oxygen can be desorbed at 100 °C into a stream of inert gas and the rate of oxygen desorption depends on the temperature of decompositive N2O adsorption. An improved procedure for measuring copper surface area by pulse chromatographic technique have been suggested.
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Inger, Marek, Agnieszka Dobrzyńska-Inger, Jakub Rajewski, and Marcin Wilk. "The Use of Response Surface Methodology in Ammonia Oxidation Reaction Study." Journal of Chemistry 2019 (February 6, 2019): 1–8. http://dx.doi.org/10.1155/2019/2641315.
Повний текст джерелаАнотація:
The design of experiments (DoEs) with response surface methodology (RSM) were used to investigate the effect of operating parameters on the ammonia oxidation process. In this paper, the influence of reactor’s load and temperature of reaction as independent variables was investigated. The efficiency of NH3 oxidation to NO and N2O concentration in nitrous gases gas was identified as response variables. As a result of these studies, statistically significant models for two responses variables were developed.
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Wang, Yan-Bin, Qiong Su, and Rong-Min Wang. "Exploring the gas-phase reaction of methylenecyclopropane anion with N2O from theoretical viewpoint." Computational and Theoretical Chemistry 983 (March 2012): 45–53. http://dx.doi.org/10.1016/j.comptc.2011.12.021.
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Liang, J. X., Y. B. Wang, Z. Y. Geng, Y. Z. Wang, and Y. C. Wang. "Gas-phase reaction of the isobutenyl anion with N2O from ab initio calculations." Journal of Structural Chemistry 54, no. 2 (March 2013): 292–300. http://dx.doi.org/10.1134/s0022476613020030.
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Fueno, Takayuki, Masayuki Fukuda та Keiichi Yokoyama. "Mechanism of the reaction NH(1Δ)+NO→N2O+H in the gas phase". Chemical Physics 124, № 2 (серпень 1988): 265–72. http://dx.doi.org/10.1016/0301-0104(88)87156-8.
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Weissenberger, Tobias, Ralf Zapf, Helmut Pennemann, and Gunther Kolb. "Effect of the Active Metal on the NOx Formation during Catalytic Combustion of Ammonia SOFC Off-Gas." Catalysts 12, no. 10 (October 7, 2022): 1186. http://dx.doi.org/10.3390/catal12101186.
Повний текст джерелаАнотація:
Catalytic combustion of hydrogen and ammonia containing off-gas surrogate from an ammonia solid oxide fuel cell (SOFC) was studied with a focus on nitrogen oxides (NOx) mitigation. Noble and transition metals (Pt, Pd, Ir, Ru, Rh, Cu, Fe, Ni) supported on Al2O3 were tested in the range of 100 to 800 °C. The tested catalysts were able to completely convert hydrogen and ammonia present in the off-gas. The selectivity to NOx increased with reaction temperature and stagnated at temperatures of 600 °C and higher. At low temperatures, the formation of N2O was evident, which declined with increasing temperature until no N2O was observed at temperatures exceeding 400 °C. Over nickel and iridium-based catalysts, the NOx formation was reduced drastically, especially at 300 to 400 °C. To the best knowledge of the authors, the current paper is the first study about catalytic combustion of hydrogen-ammonia mixtures as a surrogate of an ammonia-fed SOFC off-gas.
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Sadovskaya, Ekaterina, Larisa Pinaeva, Valerii Skazka, and Igor Prosvirin. "Kinetics of Oxygen Exchange and N2O Decomposition Reaction over MeOx/CeO2 (Me = Fe, Co, Ni) Catalysts." Materials 16, no. 3 (January 18, 2023): 929. http://dx.doi.org/10.3390/ma16030929.
Повний текст джерелаАнотація:
MeOx/CeO2 (Me = Fe, Co, Ni) samples were tested in an 18O2 temperature-programmed isotope exchange and N2O decomposition (deN2O). A decrease in the rate of deN2O in the presence of oxygen evidences the competitive adsorption of N2O and O2 on the same sites. A study of isotope oxygen exchange revealed dissociative oxygen adsorption with the subsequent formation of surface oxygen species. The same species, more probably, result from N2O adsorption and the following N2 evolution to the gas phase. We supposed the same mechanism of O2 formation from surface oxygen species in both reactions, including the stages responsible for its mobility. A detailed analysis of the kinetics of isotope exchange has been performed, and the rates of one-atom (RI) and two-atom (RII) types of exchange were evaluated. The rate of the stage characterizing the mobility of surface oxygen was calculated, supposing the same two-step mechanism was relevant for both types of exchange. The effect of oxygen mobility on the kinetics of deN2O was estimated. An analysis of the possible pathways of isotope transfer from MeOx to CeOx showed that direct oxygen exchange on the Me–Ce interface makes a valuable contribution to the rate of this reaction. The principal role of the Me–Ce interface in deN2O was confirmed with independent experiments on FeOx/CeO2 samples with a different iron content.
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Weymann, D., H. Geistlinger, R. Well, C. von der Heide, and H. Flessa. "Kinetics of N<sub>2</sub>O production and reduction in a nitrate-contaminated aquifer inferred from laboratory incubation experiments." Biogeosciences Discussions 7, no. 1 (January 20, 2010): 503–43. http://dx.doi.org/10.5194/bgd-7-503-2010.
Повний текст джерелаАнотація:
Abstract. Knowledge of the kinetics of N2O production and reduction in groundwater is essential for the assessment of potential indirect emissions of the greenhouse gas. In this study, we investigated this kinetics using a laboratory approach. The results were compared to field measurements in order to examine their transferability to the in situ conditions. The study site was the unconfined, predominantly sandy Fuhrberger Feld aquifer in Northern Germany. A special characteristic of the aquifer is the occurrence of the vertically separated process zones of heterotrophic denitrification in the surface groundwater and of autotrophic denitrification in the deeper groundwater, respectively. The kinetics of N2O production and reduction in both process zones was studied during long-term anaerobic laboratory incubations of aquifer slurries using the 15N tracer technique. We measured N2O, N2 and NO3− concentrations as well as parameters of the aquifer material that were related to the relevant electron donors, i.e. organic carbon and sulfur. The anaerobic incubations showed a low denitrification activity of heterotrophic denitrification with initial rates between 0.0002 and 0.0133 mg N kg−1 day−1. The process was carbon limited due to the poor availability of its electron donor. In the autotrophic denitrification zone, initial denitrification rates were considerably higher, ranging between 0.0303 and 0.1480 mg N kg−1 d−1 and NO3− as well as N2O were completely removed within 60 to 198 days. N2O accumulated during heterotrophic and autotrophic denitrification, but maximum concentrations were substantially higher during the autotrophic process. The results revealed a satisfactory transferability of the laboratory incubations to the field scale for autotrophic denitrification, whereas the heterotrophic process less reflected the field conditions due to considerably lower N2O accumulation during laboratory incubation. Finally, we applied a conventional model using first-order-kinetics to determine the reaction rates of the NO3−-to-N2O step and the N2O-to-N2 step, and evaluated the reaction rate constants for both steps. The model yielded fits to the experimental data that were of limited goodness, indicating that a more sophisticated approach is essential to describe the investigated reaction kinetics satisfactorily.
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Campbell, Mark L. "Kinetic Study of the Reaction of Rh(a4F9/2) with N2O, O2 and NO." Laser Chemistry 17, no. 4 (January 1, 1998): 219–37. http://dx.doi.org/10.1155/1998/82640.
Повний текст джерелаАнотація:
The gas phase reactivity of Rh(a4F9/2) with N2O, O2 and NO is reported. Removal rate constants for the excited states of rhodium below 13,000cm-1 are also reported. The reaction rate of Rh(a4F9/2) with N2O is relatively temperature insensitive. The rate constants for the bimolecular reaction are described in Arrhenius form by (1.3±0.3)×10−12exp(−1.3±0.8KJ/mol/RT)cm3s−1 The reaction rates of the a4F9/2 state with O2 and NO are pressure dependent. For O2, the limiting low-pressure thirdorder, K0, and limiting high-pressure second-order, K∞, room temperature rate constants in argon buffer are (6.6±0.6)×10−30cm6s−1 and (2.1±0.2)×10−11cm3s−1, respectively. For NO, K2 and K∞ are (1.3±0.2×10−30cm6s−1) and (2.1±0.4)×10−11cm3s−1, respectively. The removal rates of the excited states are faster than the ground state by a factor of 2 or more.
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Kelley, Patrick M., and Arthur B. DuBois. "Comparison between the uptake of nitrous oxide and nitric oxide in the human nose." Journal of Applied Physiology 85, no. 4 (October 1, 1998): 1203–9. http://dx.doi.org/10.1152/jappl.1998.85.4.1203.
Повний текст джерелаАнотація:
The absorption of nitrous oxide (N2O) during unidirectional flow was compared with the rate of uptake of nitric oxide (NO). At flow rates of 10, 20, and 60 ml/min from one nostril to the other, with the soft palate closed, the N2O reached a steady-state rate of absorption in 5–15 min. The mean superficial capillary blood flow ( n = 5) calculated from solubility and the steady-state rate of N2O absorption ranged from 13.3 to 15.9 ml/min. The relation between absorption of N2O in the nose and capillary blood flow fits a ventilation-perfusion model used by others to describe uptake of inert, soluble gases in the rat nose. By contrast, the rate of uptake of NO gas, which is chemically reactive, is 25–31 times as great as predicted by just its blood-to-air partition coefficient. Exogenous NO (16.9 parts/million) did not induce nasal vasodilation as measured with laser Doppler and N2O absorption methods. The difference between the measured rate of uptake of NO and the rate of uptake attributable to its partition coefficient in blood at the rate of blood flow calculated from N2O uptake is probably due to chemical reaction of NO in mucous secretions, nasal tissues, and capillary blood.
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Wang, Zhe-Chen, Ya-Ke Li, Sheng-Gui He, and Veronica M. Bierbaum. "The HNO− radical anion: A proposed intermediate in diazeniumdiolate synthesis using nitric oxide and alkoxides." European Journal of Mass Spectrometry 25, no. 1 (September 6, 2018): 82–85. http://dx.doi.org/10.1177/1469066718799732.
Повний текст джерелаАнотація:
The strategy of synthesizing diazeniumdiolates (X–N(O)=NO−) through the coexistence of nitric oxide and alkoxides (RO−) was introduced by Wilhelm Traube 120 years ago. Today, despite the wide use of diazeniumdiolate derivatives to release nitric oxide in the treatment of cancer, the first step of the reaction mechanism for diazeniumdiolate synthesis remains a mystery and is thought to be complex. We have studied the gas-phase reactions of nitric oxide with alkoxides at room temperature. An electron-coupled hydrogen transfer is observed, and the radical anion HNO− is the only ionic product in these reactions. HNO− can further react with nitric oxide to form N2O and HO−.
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Obalová, Lucie, František Kovanda, Květuše Jirátová, Kateřina Pacultová, and Zdenek Lacný. "Application of Calcined Layered Double Hydroxides as Catalysts for Abatement of N2O Emissions." Collection of Czechoslovak Chemical Communications 73, no. 8-9 (2008): 1045–60. http://dx.doi.org/10.1135/cccc20081045.
Повний текст джерелаАнотація:
The results of catalytic decomposition of N2O over mixed oxide catalysts obtained by calcination of layered double hydroxides (LDHs) are summarized. Mixed oxides were prepared by thermal treatment (500 °C) of coprecipitated LDH precursors with general chemical composition of MII1-xMIIIx(OH)2(CO3)x/2·yH2O, where MII was Ni, Co, Cu and/or Mg, MIII was Mn, Fe and/or Al, and the MII/MIII molar ratio was adjusted to 2. The influence of chemical composition of the MII-MIII mixed oxide catalysts on their activity and stability in N2O decomposition was examined. The highest N2O conversion was reached over Ni-Al (4:2) and Co-Mn-Al (4:1:1) catalysts. Their suitability for practical application was proved in simulated process stream in the presence of O2, NO, NO2 and H2O. It was found that N2O conversion decreased with increasing amount of oxygen in the feed. The presence of NO in the feed caused a slight decrease in N2O conversion. A strong decrease in the reaction rate was observed over the Ni-Al catalyst in the presence of NO2 while no N2O conversion decrease was observed over the Co-Mn-Al catalyst. Water vapor inhibited the N2O decomposition over all tested catalysts. The obtained kinetic data for N2O decomposition in a simulated process stream over the Co-Mn-Al catalyst were used for a preliminary reactor design. The packed bed volume necessary for N2O emission abatement in a HNO3 production plant was calculated as 35 m3 for waste gas flow rate of 30 000 m3 h-1.
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A, Tumendelger, Byambadorj T, C. Bors, and A. Lorke. "Investigation of dissolved N2O production processes during wastewater treatment system in Ulaanbaatar." Mongolian Journal of Chemistry 17, no. 43 (February 3, 2017): 23–27. http://dx.doi.org/10.5564/mjc.v17i43.742.
Повний текст джерелаАнотація:
Nitrous oxide (N2O) is an increasing greenhouse gas in the troposphere and a potential destroyer of stratospheric ozone layer. Wastewater treatment plant (WWTP) is one of the anthropogenic N2O sources because inorganic and organic nitrogen compounds are converted to nitrate (NO3-, in the case of standard system) or N2 (in the case of advanced system) by bacterial nitrification and denitrifcation processes in WWTP. These major processes can be distinguished by isotopocule analysis. In order to reveal production mechanisms of N2O in a standard wastewater treatment, we made water sampling at the central WWTP in Ulaanbaatar. The water samples collected from seven stations including biological reaction tanks were measured for concentration and isotopocule ratios of dissolved N2O and other inorganic nitrogen. Dissolved N2O concentration was extremely higher than that expected under atmospheric equilibrium (about 9 nmol/l) at all stations, indicating that this system is a potential source of N2O. It showed a gradual increase with the progress of biological reaction and the highest concentration (335.7 nmol/l) was observed at station N5-4 of the aeration tank when the DO was 5.7 mg/l. Nitrification by nitrifying bacteria could actively occur by the concentration of NH4+ decreased whereas NO2- and NO3- showed a temporal and monotonic increase, respectively, under high DO concentration. Although the reported values of site preference (SP) of N2O, the difference in 15N/14N ratio between central (α) and terminal (β) nitrogen, produced via NO2- reduction (SP(ND)), including both nitrifier and denitrifier denitrification, and NH2OH oxidation (SP(HO)) ranged from -10.7‰ to 0‰ and 31.4‰ to 36.3‰, respectively, the observed SP at aeration tank was close to SP(ND) rather than SP(HO). It was ranged from 0.4‰ to 13.3‰ when N2O concentration was high, implying that the NO2- reduction made a greater contribution to N2O production. Slightly elevated SP (13.3‰) only at station N5-1 was derived from the mixing of N2O produced via NH2OH oxidation and the maximal contribution of this pathway was estimated to be about 40%. In other words, the contribution of NO2- reduction was more than 60%.
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Weymann, D., H. Geistlinger, R. Well, C. von der Heide, and H. Flessa. "Kinetics of N<sub>2</sub>O production and reduction in a nitrate-contaminated aquifer inferred from laboratory incubation experiments." Biogeosciences 7, no. 6 (June 20, 2010): 1953–72. http://dx.doi.org/10.5194/bg-7-1953-2010.
Повний текст джерелаАнотація:
Abstract. Knowledge of the kinetics of N2O production and reduction in groundwater is essential for the assessment of potential indirect emissions of the greenhouse gas. In the present study, we investigated this kinetics using a laboratory approach. The results were compared to field measurements in order to examine their transferability to the in situ conditions. The study site was the unconfined, predominantly sandy Fuhrberger Feld aquifer in northern Germany. A special characteristic of the aquifer is the occurrence of the vertically separated process zones of heterotrophic denitrification in the near-surface groundwater and of autotrophic denitrification in depths beyond 2–3 m below the groundwater table, respectively. The kinetics of N2O production and reduction in both process zones was studied during long-term anaerobic laboratory incubations of aquifer slurries using the 15N tracer technique. We measured N2O, N2, NO3-, NO2-, and SO42- concentrations as well as parameters of the aquifer material that were related to the relevant electron donors, i.e. organic carbon and pyrite. The laboratory incubations showed a low denitrification activity of heterotrophic denitrification with initial rates between 0.2 and 13 μg N kg−1 d−1. The process was carbon limited due to the poor availability of its electron donor. In the autotrophic denitrification zone, initial denitrification rates were considerably higher, ranging between 30 and 148 μg N kg−1 d−1, and NO3- as well as N2O were completely removed within 60 to 198 days. N2O accumulated during heterotrophic and autotrophic denitrification, but maximum concentrations were substantially higher during the autotrophic process. The results revealed a satisfactory transferability of the laboratory incubations to the field scale for autotrophic denitrification, whereas the heterotrophic process less reflected the field conditions due to considerably lower N2O accumulation during laboratory incubation. Finally, we applied a conventional model using first-order-kinetics to determine the reaction rate constants k1 for N2O production and k2 for N2O reduction, respectively. The goodness of fit to the experimental data was partly limited, indicating that a more sophisticated approach is essential to describe the investigated reaction kinetics satisfactorily.
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Luckmann, Monique, Daniel Mania, Melanie Kern, Lars R. Bakken, Åsa Frostegård, and Jörg Simon. "Production and consumption of nitrous oxide in nitrate-ammonifying Wolinella succinogenes cells." Microbiology 160, no. 8 (August 1, 2014): 1749–59. http://dx.doi.org/10.1099/mic.0.079293-0.
Повний текст джерелаАнотація:
Global warming is moving more and more into the public consciousness. Besides the commonly mentioned carbon dioxide and methane, nitrous oxide (N2O) is a powerful greenhouse gas in addition to its contribution to depletion of stratospheric ozone. The increasing concern about N2O emission has focused interest on underlying microbial energy-converting processes and organisms harbouring N2O reductase (NosZ), such as denitrifiers and ammonifiers of nitrate and nitrite. Here, the epsilonproteobacterial model organism Wolinella succinogenes is investigated with regard to its capacity to produce and consume N2O during growth by anaerobic nitrate ammonification. This organism synthesizes an unconventional cytochrome c nitrous oxide reductase (cNosZ), which is encoded by the first gene of an atypical nos gene cluster. However, W. succinogenes lacks a nitric oxide (NO)-producing nitrite reductase of the NirS- or NirK-type as well as an NO reductase of the Nor-type. Using a robotized incubation system, the wild-type strain and suitable mutants of W. succinogenes that either produced or lacked cNosZ were analysed as to their production of NO, N2O and N2 in both nitrate-sufficient and nitrate-limited growth medium using formate as electron donor. It was found that cells growing in nitrate-sufficient medium produced small amounts of N2O, which derived from nitrite and, most likely, from the presence of NO. Furthermore, cells employing cNosZ were able to reduce N2O to N2. This reaction, which was fully inhibited by acetylene, was also observed after adding N2O to the culture headspace. The results indicate that W. succinogenes cells are competent in N2O and N2 production despite being correctly grouped as respiratory nitrate ammonifiers. N2O production is assumed to result from NO detoxification and nitrosative stress defence, while N2O serves as a terminal electron acceptor in anaerobic respiration. The ecological implications of these findings are discussed.
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Kachina, Anna, Sergei Preis, German Charles Lluellas, and Juha Kallas. "Gas-Phase and Aqueous Photocatalytic Oxidation of Methylamine: The Reaction Pathways." International Journal of Photoenergy 2007 (2007): 1–6. http://dx.doi.org/10.1155/2007/32524.
Повний текст джерелаАнотація:
Photocatalytic oxidation (PCO) of methylamine (MA) on titanium dioxide in aqueous and gaseous phases was studied. A simple batch glass reactor for aqueous PCO and an annular continuous flow reactor for the gas-phase PCO were used. Maximum aqueous PCO efficiency was achieved in alkaline media. Two mechanisms of aqueous PCO—decomposition to formate and ammonia, and oxidation of organic nitrogen directly to nitrite—lead ultimately toCO2, water, ammonia, and nitrate: formate and nitrite were observed as intermediates. A part of the ammonia formed in the reaction was oxidized to nitrite and nitrate. Volatile PCO products of MA included ammonia, nitrogen dioxide(NO2), nitrous oxide(N2O), carbon dioxide, and water. Thermal catalytic oxidation (TCO) resulted in the formation of ammonia, hydrogen cyanide, carbon monoxide, carbon dioxide, and water. The gas-phase PCO kinetics is described by the monomolecular Langmuir-Hinshelwood model. No deactivation ofTiO2catalyst was observed.
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Nagieva, I. T., N. I. Ali-zadeh, and T. М. Nagiev. "COHERENT SYNCHRONIZATION OF PYRIDINE DIMERIZATION REACTIONS AND DECOMPOSITION OF “GREEN OXIDANTS” – H2O2 AND N2O." Azerbaijan Chemical Journal, no. 4 (December 8, 2021): 6–11. http://dx.doi.org/10.32737/0005-2531-2021-4-6-11.
Повний текст джерелаАнотація:
In recent years, hydrogen peroxide and nitrous oxide (1) "green oxidants" – have attracted much attention of researchers as a selective oxidizing agent for the catalytic oxidation of pyridine bases. In this regard, the reaction of pyridine oxidation by hydrogen peroxide and nitrous oxide under homogeneous conditions, in the gas phase, without the use of catalysts, at atmospheric pressure, has been experimentally investigated. Areas of selective oxidation of pyridine with hydrogen peroxide and nitrous oxide have been established, and optimal conditions have been found for obtaining valuable raw materials required in the petrochemical, chemical, and pharmaceutical industries
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Weymann, D., R. Well, H. Flessa, C. von der Heide, M. Deurer, K. Meyer, C. Konrad, and W. Walther. "Assessment of excess N<sub>2</sub> and groundwater N<sub>2</sub>O emission factors of nitrate-contaminated aquifers in northern Germany." Biogeosciences Discussions 5, no. 2 (April 1, 2008): 1263–92. http://dx.doi.org/10.5194/bgd-5-1263-2008.
Повний текст джерелаАнотація:
Abstract. We investigated the dynamics of denitrification and nitrous oxide (N2O) accumulation in 4 nitrate (NO3−) contaminated denitrifying sand and gravel aquifers of northern Germany (Fuhrberg, Sulingen, Thülsfelde and Göttingen) to quantify their potential N2O emission and to evaluate existing concepts of N2O emission factors. Excess N2-N2produced by denitrification – was determined by using the argon (Ar) concentration in groundwater as a natural inert tracer, assuming that this noble gas functions as a stable component and does not change during denitrification. Furthermore, initial NO3− concentrations (NO3− that enters the groundwater) were derived from excess N2 and actual NO3− concentrations in groundwater in order to determine potential indirect N2O emissions as a function of the N input. Median concentrations of N2O and excess N2 ranged from 3 to 89 μg N L−1 and from 3 to 10 mg N L−1 respectively. Reaction progress (RP) of denitrification was determined as the ratio between products (N2O-N + excess N2) and starting material (initial NO3− concentration) of the process, characterizing the different stages of denitrification. N2O concentrations were lowest at RP close to 0 and RP close to 1 but relatively high at a RP between 0.2 and 0.6. For the first time, we report groundwater N2O emission factors consisting of the ratio between N2O-N and initial NO3−-N concentrations (EF1). According to denitrification intensity, EF(1) was smaller than the ratio between N2O-N and actual NO3−-N concentrations EF(2). In general, these emission factors were highly variable within the aquifers. The site medians ranged between 0.00043–0.00438 for EF(1) and 0.00092–0.01801 for EF(2), respectively. For the aquifers of Fuhrberg and Sulingen, we found EF(1) median values which are close to the 2006 IPCC default value of 0.0025. In contrast, we determined significant lower EFs for the aquifers of Thülsfelde and Göttingen.
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Liu, Hui-Wen, Yong-Cheng Wang, Zhi-Yuan Geng, Ling-Ling Lv, Bing Yan, Qiang Wang, and Dan-Dan Cui. "A theoretical study of the reaction of La+ with N2O in the gas phase." Journal of Molecular Structure: THEOCHEM 944, no. 1-3 (March 2010): 89–96. http://dx.doi.org/10.1016/j.theochem.2009.12.031.
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Okada, Satoshi, Yasuo Abe, Setsuo Taniguchi, and Shinichi Yamabe. "Five-membered ring intermediates in the gas-phase CN− + N2O reaction. A theoretical study." Chemical Physics Letters 209, no. 1-2 (June 1993): 161–66. http://dx.doi.org/10.1016/0009-2614(93)87217-q.
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Mazely, T. L., and M. A. Smith. "Gas phase reaction rates of C+ with O2, NO and N2O near 0.6 K." Chemical Physics Letters 144, no. 5-6 (May 1988): 563–69. http://dx.doi.org/10.1016/0009-2614(88)87316-0.
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Paranjpe, Rucha, A. K. Suresh, and Preeti Aghalayam. "Understanding Pt–Rh Synergy in a Three-Way Catalytic Converter." International Journal of Chemical Reactor Engineering 11, no. 1 (October 30, 2013): 535–42. http://dx.doi.org/10.1515/ijcre-2013-0072.
Повний текст джерелаАнотація:
Abstract NO reduction to N2 is the key reaction for efficient operation of a three-way catalytic converter (TWC). It is reported that metal catalysts Pt and Rh co-exist as individual metals in a TWC to give synergistic performance. In this article, we have studied the NO + CO reaction for a 1:1 physical mixture of silica supported Pt and Rh catalysts using fixed bed experiments and microkinetic modeling. The microkinetic model [14] for the reaction on single metals Pt and Rh is simulated for the mixture case in CHEMKIN PRO®. It is observed that the mixture maintains the activity while producing less N2O (by-product of NO + CO reaction) thus enhancing N2 selectivity inspite of having only half amount of Rh. Analysis of surface coverages on individual metals in mixture shows that in the presence of Pt, CO poisoning of Rh is reduced at lower temperature leading to better overall conversion and selectivity. This has potential benefit in automotive catalysis, as it results in the formation of significantly lower amounts of N2O, an undesirable side-product and greenhouse gas; at a lower cost than if pure Pt/Rh catalysts were used.
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Palmer, Katharina, and Marcus A. Horn. "Actinobacterial Nitrate Reducers and Proteobacterial Denitrifiers Are Abundant in N2O-Metabolizing Palsa Peat." Applied and Environmental Microbiology 78, no. 16 (June 1, 2012): 5584–96. http://dx.doi.org/10.1128/aem.00810-12.
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ABSTRACTPalsa peats are characterized by elevated, circular frost heaves (peat soil on top of a permanently frozen ice lens) and are strong to moderate sources or even temporary sinks for the greenhouse gas nitrous oxide (N2O). Palsa peats are predicted to react sensitively to global warming. The acidic palsa peat Skalluvaara (approximate pH 4.4) is located in the discontinuous permafrost zone in northwestern Finnish Lapland.In situN2O fluxes were spatially variable, ranging from 0.01 to −0.02 μmol of N2O m−2h−1. Fertilization with nitrate stimulatedin situN2O emissions and N2O production in anoxic microcosms without apparent delay. N2O was subsequently consumed in microcosms. Maximal reaction velocities (vmax) of nitrate-dependent denitrification approximated 3 and 1 nmol of N2O per h per gram (dry weight [gDW]) in soil from 0 to 20 cm and below 20 cm of depth, respectively.vmaxvalues of nitrite-dependent denitrification were 2- to 5-fold higher than thevmaxnitrate-dependent denitrification, andvmaxof N2O consumption was 1- to 6-fold higher than that of nitrite-dependent denitrification, highlighting a high N2O consumption potential. Up to 12 species-level operational taxonomic units (OTUs) ofnarG,nirKandnirS, andnosZwere retrieved. Detected OTUs suggested the presence of diverse uncultured soil denitrifiers and dissimilatory nitrate reducers, hitherto undetected species, as well asActino-,Alpha-, andBetaproteobacteria. Copy numbers ofnirSalways outnumbered those ofnirKby 2 orders of magnitude. Copy numbers ofnirStended to be higher, while copy numbers ofnarGandnosZtended to be lower in 0- to 20-cm soil than in soil below 20 cm. The collective data suggest that (i) the source and sink functions of palsa peat soils for N2O are associated with denitrification, (ii) actinobacterial nitrate reducers andnirS-type andnosZ-harboring proteobacterial denitrifiers are important players, and (iii) acidic soils like palsa peats represent reservoirs of diverse acid-tolerant denitrifiers associated with N2O fluxes.
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Flynn, Bryan, Amanda Graham, Neal Scott, David B. Layzell, and Zhongmin Dong. "Nitrogen fixation, hydrogen production and N2O emissions." Canadian Journal of Plant Science 94, no. 6 (August 2014): 1037–41. http://dx.doi.org/10.4141/cjps2013-210.
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Flynn, B., Scott, N. and Dong, Z. 2014. Nitrogen fixation, hydrogen production and N2O emissions. Can. J. Plant Sci. 94: 1037–1041. H2 is a by-product of the nitrogenase reaction. Exposure to H2 is linked to increased N2O production, increased CO2 fixation and plant growth promotion in soil. The effects of H2 exposure on soil were observed using controlled H2 gas treatments and field trials with legumes. In field trials, increased N2O production was observed in soil adjacent to legume nodules and inoculation of H2-oxidizing isolates led to increased N2O emissions in corn fields. Many H2-oxidizing isolates tested positive for key denitrification genes, indicating a connection between H2 uptake and N2O emissions. H2 treatment significantly increased copy number of the nitrite reductase (nirK) gene suggesting increased denitrification as the source of N2O. There was also a significant increase in copy number and expression of the RubisCO (cbbL) gene in soil. H2-oxidizing bacterial isolates (JM63 and JM162a) were found to promote plant growth, increasing tiller number and yield in spring wheat and barley. Combined results of T-RFLP and 16S rDNA clone libraries analysis revealed bacterial community structure changes in response to H2 treatment, primarily with increases to the Gammaproteobacteria and Betaproteobacteria groups. The results of these studies help provide a better understanding of the soil bacterial community's responses to H2 exposure and may lead to the development of a commercially viable plant growth promoting inoculant.
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Lambe, Andrew, Paola Massoli, Xuan Zhang, Manjula Canagaratna, John Nowak, Conner Daube, Chao Yan, et al. "Controlled nitric oxide production via O(<sup>1</sup>D) + N<sub>2</sub>O reactions for use in oxidation flow reactor studies." Atmospheric Measurement Techniques 10, no. 6 (June 22, 2017): 2283–98. http://dx.doi.org/10.5194/amt-10-2283-2017.
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Abstract. Oxidation flow reactors that use low-pressure mercury lamps to produce hydroxyl (OH) radicals are an emerging technique for studying the oxidative aging of organic aerosols. Here, ozone (O3) is photolyzed at 254 nm to produce O(1D) radicals, which react with water vapor to produce OH. However, the need to use parts-per-million levels of O3 hinders the ability of oxidation flow reactors to simulate NOx-dependent secondary organic aerosol (SOA) formation pathways. Simple addition of nitric oxide (NO) results in fast conversion of NOx (NO + NO2) to nitric acid (HNO3), making it impossible to sustain NOx at levels that are sufficient to compete with hydroperoxy (HO2) radicals as a sink for organic peroxy (RO2) radicals. We developed a new method that is well suited to the characterization of NOx-dependent SOA formation pathways in oxidation flow reactors. NO and NO2 are produced via the reaction O(1D) + N2O → 2NO, followed by the reaction NO + O3 → NO2 + O2. Laboratory measurements coupled with photochemical model simulations suggest that O(1D) + N2O reactions can be used to systematically vary the relative branching ratio of RO2 + NO reactions relative to RO2 + HO2 and/or RO2 + RO2 reactions over a range of conditions relevant to atmospheric SOA formation. We demonstrate proof of concept using high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) measurements with nitrate (NO3−) reagent ion to detect gas-phase oxidation products of isoprene and α-pinene previously observed in NOx-influenced environments and in laboratory chamber experiments.