Transient kinetics

Figure C3.1.8. Schematic diagram of a transient kinetic apparatus using iaser-induced fluorescence (LIF) as a probe and a CO2 iaser as a pump source. (From Steinfeid J I, Francisco J S and Fiase W L i989 Chemical Kinetics and. Dynamics (Engiewood Ciiffs, NJ Prentice-Fiaii).)...

This kinetics text contains a comprehensive chapter on experimentai techniques that overviews transient kinetic methods, as weii as a chapter devoted to photochemistry. 

A kinetics text with a strong theoreticai bent that overviews transient kinetic methods and discusses data anaiysis issues such as error propagation and sensitivity anaiysis. 

Reviews fast transient kinetic studies of bioiogicai moiecuies (exciuding fluorescence studies). 

This study presents kinetic data obtained with a microreactor set-up both at atmospheric pressure and at high pressures up to 50 bar as a function of temperature and of the partial pressures from which power-law expressions and apparent activation energies are derived. An additional microreactor set-up equipped with a calibrated mass spectrometer was used for the isotopic exchange reaction (DER) N2 + N2 = 2 N2 and the transient kinetic experiments. The transient experiments comprised the temperature-programmed desorption (TPD) of N2 and H2. Furthermore, the interaction of N2 with Ru surfaces was monitored by means of temperature-programmed adsorption (TPA) using a dilute mixture of N2 in He. The kinetic data set is intended to serve as basis for a detailed microkinetic analysis of NH3 synthesis kinetics [10] following the concepts by Dumesic et al. [11]. 

Analysis of the dynamics of SCR catalysts is also very important. It has been shown that surface heterogeneity must be considered to describe transient kinetics of NH3 adsorption-desorption and that the rate of NO conversion does not depend on the ammonia surface coverage above a critical value [79], There is probably a reservoir of adsorbed species which may migrate during the catalytic reaction to the active vanadium sites. It was also noted in these studies that ammonia desorption is a much slower process than ammonia adsorption, the rate of the latter being comparable to that of the surface reaction. In the S02 oxidation on the same catalysts, it was also noted in transient experiments [80] that the build up/depletion of sulphates at the catalyst surface is rate controlling in S02 oxidation. 

Transient kinetic experiments have also been carried out to complement the information deduced from the steady-state measurements [33], Systematic variations were observed during the transition from the clean surface to the steady-state catalytic regime that correlate well with the overall reaction rates in the latter. Specifically, there is a time delay in the production of molecular nitrogen because of the need to buildup a threshold of atomic nitrogen coverage on the surface. This atomic nitrogen coverage, which could... 

Gopinath, C. S. and Zaera, F. (2000) Transient kinetics during the isothermal reduction of NO by CO on Rh(lll) as studied with effusive collimated molecular beams , J. Phys. Chem. B, 104, 3194. 

Burch, R., Shestov, A.A. and Sullivan, J.A. (1999) A steady-state isotopic transient kinetic analysis of the N0/02/H2 reaction over Pt/Si02 catalysts, J. Catal. 188, 69. 

Agnelli, M., Swaan, H. M., Marquez-Alvarez, C., Martin, G. A., and Mirodatos, C. 1998. CO hydrogenation on a nickel catalyst. II. A mechanistic study by transient kinetics and infrared spectroscopy. J. Catal. 175 117-28. 

Li, S., Ding, W., Meitzner, G.D., and Iglesia, E. 2002. Spectroscopic and transient kinetic studies of site requirements in iron-catalyzed Fischer-Tropsch synthesis. J. Phys. Chem. B 106 85-91. 

Rothaemel, M., Hanssen, K.F., Blekkan, E.A., Schanke, D., and Holmen, A. 1997. The effect of water on cobalt Fischer-Tropsch catalysts studied by steady-state isotopic transient kinetic analysis (SSITKA). Catal. Today 38 79-84. 

In this contribution, the steady-state isotopic transient kinetic analysis-diffuse reflectance Fourier transform spectroscopy (SSITKA-DRIFTS) method provides further support to the conclusion that not only are infrared active formates likely intermediates in the water-gas shift (WGS) reaction, in agreement with the mechanism proposed by Shido and Iwasawa for Rh/ceria, but designing catalysts based on formate C-H bond weakening can lead to significantly higher... 

During steady-state isotopic transient kinetic analysis, the 12CO was switched to 13CO and the carbon-containing adsorbed and gas phase species were monitored in the IR as they exchanged from the 12C to the 13C label. Particular attention was made to those species that exchanged on a timescale similar to that of the exchange of the product C02, as that species could be a likely intermediate to the water-gas... 

Methylamine dehydrogenase of Methylophilus methylotro-phus, proton transfer from the methylamine adduct of tryptophan tryptophylquinone (TTQ) CHs-amine vs. CDs-amine, transient kinetics studies of H-transfer step, H/D IE 5-40 °C, Ah/Ad = 16.8 0.5, AH 42.2 1.1 (H), 43.2 1.8 (D) kJ/mol, rate constant unchanged. 

The oxidation of CO by Oj over group VIII metal catalysts has been the subject of a large body of ultrahigh vacuum surface science and high pressure catalysis work due to its importance in pollution control. Currently, the removal of CO as CO2 from automobile exhaust is accomplished by catalytic converters which employ a supported Pt, Pd, and Rh catalyst. The importance of CO oxidation has led to numerous recent studies of the kinetics of this reaction on supported metal catalysts and transient kinetic studies on polycrystalline foils , which have sought to identify and quantify the parameters of the elementary mechanistic steps in CO oxidation. 

The Langmuir-Hinshelwood reaction between adsorbed CO and O atoms is well established as the dominant reaction mechanism for conditions where CO is the primary surface species . This mechanism has been confirmed by numerous UHV studies of the coadsorption of the transient kinetic... 

A single turnover study of the conversion of the heme-HO-1 complex to free biliverdin has elucidated the relative rates of the catalytic steps 129). This transient kinetic study indicates that the conversion of Fe heme to Fe verdoheme is biphasic. Electron transfer to the Fe -heme HO-1 complex occurred at a rate of 0.11 s at 4°C and 0.49 s at 25°C with a 0.1 1 ratio of NADPH-cytochrome P450 reductase to heme HO-l complex. Oxygen binding to the reduced iron was sufficiently rapid im-der the experimental conditions that the species actually monitored... 

Ocal, M Oukaci, R Marcelin, G. Steady state isotopic transient kinetic analysis (SSITKA) investigation of NO reduetion with CO over perovskite eatalysts. Ind.Eng. Chem. Res., 1994, Volume 33, 2930-2934. 

---