Nitrous oxide kinetics

One-step hydroxylation of aromatic nucleus with nitrous oxide (N2O) is among recently discovered organic reactions. A high eflSciency of FeZSM-5 zeolites in this reaction relates to a pronounced biomimetic-type activity of iron complexes stabilized in ZSM-5 matrix. N2O decomposition on these complexes produces particular atomic oj gen form (a-oxygen), whose chemistry is similar to that performed by the active oxygen of enzyme monooxygenases. Room temperature oxidation reactions of a-oxygen as well as the data on the kinetic isotope effect and Moessbauer spectroscopy show FeZSM-5 zeolite to be a successfiil biomimetic model. 

MgO Catalyst. A charge of 42.6 g MgO catalyst was used in this experiment and kinetic measurements were made at 409°C. The response of a MgO catalyst equilibrated with helium stream to a step inflow of nitrous oxide was followed by monitoring N2 and O2 in the downflow stream and the results were presented in Figure 6. 

These kinetic relationships suggest the following reaction mechanism including the adsorption of nitrous oxide as the slowest step. 

Although the pathway of Eq. (1) is now based on much evidence (Section 111) and is unambiguous in the case of at least one bacterium [Pseudomonas stutzeri strain Zobell (f. sp. P. perfectomarina)], there have been alternative hypothesis. One hypothesis, advanced by the Hollocher group (Garber and Hollocher, 1981 St. John and Hollocher, 1977), considered NO as a likely intermediate, but one that remained at least partly enzyme-bound and was not entirely free to diffuse. This view was based on the outcome of certain kinetic and isotope experiments which can be summarized as follows. When denitrifying bacteria were challenged simultaneously with [ N]nitrite and ordinary NO, the cells reduced both compounds concomitantly to N2 (or to N2O in the presence of acetylene which is a specific inhibitor (Balderston et al., 1976 Yoshinari and Knowles, 1976) of nitrous oxide reductase). In the process, little NO was generally detected in the gas phase pool of NO and there was relatively little isotopically mixed N2O formed. That is, most of the N and N reduced to NjO appeared as N2O... 

Betlach, M. R., and Tiedje, J. M. (1981). Kinetic explanation for accumulation of nitrite, nitric oxide, and nitrous oxide during bacterial denitrification. Appl. Environ. Microbiol. 

New theories and findings on the formation of ionic species and radicals, which become trapped in the polymers, are discussed in the first two chapters, written by the two European authorities, Chapiro and Charlesby. The kinetics of crosslinking polyethylene is the subject of the American authority, Dole. A higher yield of crosslinking polyolefins was observed in the presence of nitrous oxide by the Japanese scientist, Okada. 

P. Glarborg, K. Dam-Johansen, J.A. Miller, R.J. Kee, and M.E. Coltrin. Modeling the Thermal DeNOx Process in Flow Reactors. Surface Effects and Nitrous Oxide Formation. Int. J. Chem. Kinetics, 26 421-436,1994. 

P. Glarborg, J.E. Johnson, and K. Dam-Johansen. Kinetics of Homogeneous Nitrous Oxide Decomposition. Combust. Flame, 99 523-532,1994. 

A study of the kinetics of the decomposition of ammonium perchlorate has been made by Bircumshaw and Newman [5]. The gaseous products, up to a temperature of 300°C, were found to be oxygen, chlorine, chlorine dioxide, nitrous oxide, nitrogen tetroxide, chlorine dioxide, hydrochloric acid, perchloric acid and water. The total volume of oxygen and nitrogen produced by unit weight of the solid showed practically no variation up to about 300°C. 

The epoxidation of cyclobutene (1) to cyclobutane oxide (2) with nitrous oxide (Figure 2.20) was studied by Useless Polymers Inc. as a possible step in the route to 1,2-cyclobutadiol. Researchers Hannah and John chose two catalysts for kinetic studies, catalyst A and catalyst B. 

CA 45, 5020(1951)(Spectra of nitrous oxide flames and reaction kinetics) 3) H. 

Fig. 4. Absorption kinetics over the time range of 1.7 ms of (SCN) " at 515 nm in an aqueous solution of 10 M of thiocyanate saturated with nitrous oxide after a 5-ps pulse of The dose was 4 Gy/pulse and the number of accumulations was 3899 with a repetition rate of 20 Hz. ...

Schmidt, H. L., Werner, R. A., Yoshida, N., and Well, R. (2004). Is the isotopic composition of nitrous oxide an indicator for its origin from nitrification or denitrification A theoretical approach from referred data and microbiological and enzyme kinetic aspects. Rapid Communication Mass Spectrometry 18(18), 2036—2040. 

Reaction of hydroxylamine with nitrous acid has been the subject of kinetic - " and isotopic-tracer " ° studies. In addition to formation of nitrous oxide (2), there is a minor reaction (3) forming hyponitrous acid. 

As stated above, most users of the headspace technique make no distinction between dynamic HS and PT. In one of the few publications that distinguished and compared these two HS modes, dynamic HS and PT were assessed as steps preceding high-resolution GC-electron capture detection for the determination of nitrous oxide in sea water. The process was found to exhibit a first-order kinetics in both cases and the matrix to exert a significant effect that was proportional to the nitrous oxide concentration in bidistilled water, as well as in synthetic and natural sea water. As expected, PT provided better extraction recovery, sensitivity and limits of detection — which fell in the pico-mole-per-millilitre range [46]. 

The reaction was performed in a static reactor and was followed by pressure measurements (55). Change of pressure with time (initial pressure of nitrous oxide, 148 torr) and the corresponding yield for the reaction at 250° on a freshly prepared sample of NiO(250°) are reported in Fig. 39. The reaction rate decreases with time according to the kinetic law already proposed by Winter (86)... 

It is clear that a detailed reaction mechanism cannot be deduced from kinetic measurements only. However, since different kinetic laws have been deduced from the results of the kinetic study of the reaction on fresh, regenerated and oxygenated samples, the kinetic results demonstrate that the surface of NiO(250°) is modified when it contacts nitrous oxide or oxygen at 250° and that each gas produces a specific surface modification. 

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