The relative contributions of self-heating and chain branching to the kinetics of hydrogen oxidation outside the ignition region close to the third limit

2008 ◽  
Vol 82 (1) ◽  
pp. 56-61 ◽  
Author(s):  
V. V. Azatyan ◽  
I. A. Bolod’yan ◽  
V. Yu. Navtsenya ◽  
Yu. N. Shebeko
Author(s):  
Lulu An ◽  
Xu Zhao ◽  
Tonghui Zhao ◽  
Deli Wang

Anion exchange membrane fuel cell (AEMFC) is becoming highly attractive for hydrogen utilization owing to the advantages of employing economic catalysts in alkaline electrolytes. Nevertheless, the kinetics of anodic hydrogen...


2016 ◽  
Vol 128 (33) ◽  
pp. 9719-9722 ◽  
Author(s):  
Supriya Pratihar ◽  
T. Michael Sabo ◽  
David Ban ◽  
R. Bryn Fenwick ◽  
Stefan Becker ◽  
...  

Author(s):  
lon Ganescu ◽  
George Bratulescu ◽  
Ion Papa ◽  
Anca Ganescu ◽  
Alin Barbu ◽  
...  

Salvation kinetics of [Cr(NCS)4(imidazole)2]- has been studied in ethanol-water mixtures at different temperatures. The first stage of the solvation consists of two competitive reactions: two NCS- ions are exchanged, presumably, by water molecules and simultaneously an imidazole molecule by ethanol, the latter in a second-order reaction, accelerated by hydrogen ions. The exchange of the amine is followed by the substitution of the first two NCS- ions. The third and fourth NCS- ions are substituted only in neutral and slightly acidic solutions. Kinetic parameters have been determined for reactions (1), (2), and (4). The influence of the solvent composition and acidity is discussed


2012 ◽  
Vol 58 ◽  
pp. 33-53
Author(s):  
Derek Bradley

Graham Dixon-Lewis was a physical chemist who pioneered both experimental and mathematical studies that revealed the nature of flames. His researches, based on what was known of the chemical kinetics of hydrogen oxidation, also showed the way forward for the mathematical modelling of laminar flame structures for other fuels. These models have proved invaluable in providing the input data also for the mathematical modelling of practical turbulent flames.


2010 ◽  
Vol 35 (23) ◽  
pp. 12878-12887 ◽  
Author(s):  
N.R. Elezović ◽  
Lj.M. Gajić-Krstajić ◽  
Lj.M. Vračar ◽  
N.V. Krstajić

1977 ◽  
Author(s):  
R.-M. Moeller ◽  
I. Mahn ◽  
G. Müller-Berqhaus

During gestation increased concentrations of fibrin (ogen)derivatives are observed indicative of intravascular action of thrombin. The aim of this study was to elucidate the kinetics of fibrinogen during gestation. The elimination of homologous 1-125-fibrinogen was studied in 14 pregnant rabbits during the first as well as during the third trimesters of gestation. Control studies were performed with 10 non-pregnant rabbits.The mean distribution volume of labeled fibrinogen did not significantly differ between pregnant and non-pregnant rabbits. During the third trimester pregnant rabbits demonstrated a pronounced shortening of T 1/2 of labeled fibrinogen from a mean of 55.3 hr during the first to a mean of 29.7 hr during the third trimester. The experiments showed a significant increase in the fractional catabolic rate from 45.0 to 69.9% per day in the course of gestation. The shortening of T 1/2 of labeled fibrinogen correlated to the number of fetusses per litter.This study indicates an average acceleration of the fibrinogen turnover during gestation of about 50%. These direct quantitative measurements demonstrate that fibrinogen catabolism is pronouncedly accelerated during pregnancy.


Molecules ◽  
2019 ◽  
Vol 24 (19) ◽  
pp. 3600 ◽  
Author(s):  
Maria Carta ◽  
Stuart L. James ◽  
Francesco Delogu

We focus on understanding the kinetics of a mechanically activated Knoevenagel condensation conducted in a ball mill, that is characterized by sigmoidal kinetics and the formation of a rubber-like cohesive intermediate state coating the milling ball. The previously described experimental findings are explained using a phenomenological kinetic model. It is assumed that reactants transform into products already at the very first collision of the ball with the wall of the jar. The portion of reactants that are transformed into products during each oscillation is taken to be a fraction of the amount of material that is trapped between the ball and the wall of the jar. This quantity is greater when the reaction mixture transforms from its initial powder form to the rubber-like cohesive coating on the ball. Further, the amount of reactants processed in each collision varies proportionally with the total area of the layer coating the ball. The total area of this coating layer is predicted to vary with the third power of time, thus accounting for the observed dramatic increase of the reaction rate. Supporting experiments, performed using a polyvinyl acetate adhesive as a nonreactive but cohesive material, confirm that the coating around the ball grows with the third power of time.


Although there are few gaseous reactions of more fundamental interest than the union of hydrogen and oxygen, it can hardly be said that the kinetics of this combination are at all completely understood. Many investigations have been made of the catalytic reaction which occurs in contact with various surfaces, and of the phenomena accompanying the production of flame or explosion in the gas. Little is known about the conditions governing the rate of the actual chemical change in the gas phase, because although flames and explosions depend very much upon these they are determined by a great many other factors as well. In 1899 Bodenstein, following up some work initiated by Victor Meyer, made a long series of experiments by streaming mixtures of the two gases through porcelain vessels, heated to a constant temperature, and then analysing the products. He came to the conclusion that the reaction is of the third order, following the equation d [H 2 O]/ dt = k [H 2 ] 2 [O 2 ]. Since the rate of combination was very different in different vessels, he inferred that the reaction was taking place almost entirely on the surface of the vessel.


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