Kinetics of carbon monoxide methanation on a Ni/SiO2 catalyst

1990 ◽  
Vol 55 (7) ◽  
pp. 1678-1685
Author(s):  
Vladimír Stuchlý ◽  
Karel Klusáček
Keyword(s):  
Carbon Monoxide ◽  
Reaction Rate ◽  
Catalyst Activity ◽  
Adsorbed Hydrogen ◽  
Reaction Products ◽  
Co Methanation ◽  
Molar Ratios ◽  
Rate Determining Step ◽  
Higher Temperature ◽  
Kinetics Of

Kinetics of CO methanation on a commercial Ni/SiO2 catalyst was evaluated at atmospheric pressure, between 528 and 550 K and for hydrogen to carbon monoxide molar ratios ranging from 3 : 1 to 200 : 1. The effect of reaction products on the reaction rate was also examined. Below 550 K, only methane was selectively formed. Above this temperature, the formation of carbon dioxide was also observed. The experimental data could be described by two modified Langmuir-Hinshelwood kinetic models, based on hydrogenation of surface CO by molecularly or by dissociatively adsorbed hydrogen in the rate-determining step. Water reversibly lowered catalyst activity and its effect was more pronounced at higher temperature.

Kinetics of the Substitution of Norbornadiene in Tetracarbonyl(norbomadiene)molybdenum(0) by 2,2'-Bipyridine

2001 ◽  
Vol 56 (3) ◽  
pp. 281-286 ◽  
Author(s):  
Ceyhan Kayran ◽  
Eser Okan
Keyword(s):  
Reaction Rate ◽  
Activation Parameters ◽  
Bipy Ligand ◽  
First Order ◽  
Rate Determining Step ◽  
Vis Spectroscopy ◽  
Different Temperatures ◽  
Ft Ir ◽  
Thermal Substitution ◽  
Kinetics Of

Abstract The kinetics of the thermal substitution of norbornadiene (nbd) by 2,2'-bipyridine (2,2'-bipy) in (CO)4Mo(C7H9) was studied by quantitative FT-IR and UV-VIS spectroscopy. The reaction rate exhibits first-order dependence on the concentration of the starting complex, and the observed rate constant depends on the concentration of both leaving nbd and entering 2,2'-bipy ligand. The mechanism was found to be consistent with the previously proposed one, where the rate determining step is the cleavage of one of the two Mo-olefin bonds. The reaction was performed at four different temperatures (35 -50 °C) and the evaluation of the kinetic data gives the activation parameters which now support states.

Kinetics of oxidation of cis-bis(ethylenediamine)isothiocyanatonitrocobalt(III) ion with peroxodisulphate

1979 ◽  
Vol 44 (12) ◽  
pp. 3588-3594 ◽  
Author(s):  
Vladislav Holba ◽  
Olga Volárová
Keyword(s):  
Ionic Strength ◽  
Rate Constants ◽  
Oxidation Kinetics ◽  
Reaction Rate ◽  
Salt Effect ◽  
Activation Parameters ◽  
Reaction Products ◽  
Kinetics Of Oxidation ◽  
Thermodynamic Activation Parameters ◽  
Kinetics Of

The oxidation kinetics of cis-bis(ethylenediamine)isothiocyanonitrocobalt(III) ion with peroxodisulphate was investigated in the medium of 0.01 M-HClO4 in dependence on the ionic strength and temperature and the reaction products were identified. Extrapolated values of thermodynamic activation parameters were determined from the temperature dependence of the rate constants extrapolated to zero ionic strength. The distance of the closest approach was estimated for the reacting ions by evaluating the primary salt effect. To elucidate the mechanism, the influence of the cyclic polyether 18-crown-6 on the reaction rate was followed.

Effect of irradiation and of replacement of hydrogen by deuterium on the kinetics of hydrogenation of maleic acid on a nickel catalyst

1980 ◽  
Vol 45 (6) ◽  
pp. 1632-1638 ◽  
Author(s):  
Rostislav Kudláček ◽  
Růžena Jelínková
Keyword(s):  
Reaction Rate ◽  
Catalyst Surface ◽  
Catalyst Activity ◽  
Hydrogenation Reaction ◽  
Gamma Dose ◽  
Model Reaction ◽  
Solid Catalyst ◽  
Liquid Phase Hydrogenation ◽  
Kinetics Of ◽  
Preliminary Irradiation

Liquid phase hydrogenation reaction was studied on modifying the solid catalyst by preliminary irradiation and replacing the reacting hydrogen by deuterium; the changes in the reaction rate were measured and the phenomena on the catalyst surface, particularly the change in the catalyst activity, were investigated. For the model reaction, the dependences of the reaction rate on the temperature of reduction and of the successive activation of the catalyst on the absorbed gamma dose were followed, and the dependences of the reaction rate on the reaction temperature were compared for the hydrogenation and deuteration. Isotope effect was found in the influence of the reacting medium on the catalyst property. The activity of the nickel carrier catalyst is governed by its interaction with hydrogen after the reduction, particularly by the temperature of this process.

Kinetics and mechanisms of the reaction between carbon monoxide and copper(II) in aqueous solution

1969 ◽  
Vol 47 (2) ◽  
pp. 313-321 ◽  
Author(s):  
J. J. Byerley ◽  
E. Peters
Keyword(s):  
Aqueous Solution ◽  
Carbon Monoxide ◽  
Reaction Path ◽  
Carbonyl Complex ◽  
Cupric Ion ◽  
Inhibiting Effect ◽  
Rate Determining Step ◽  
Ph Dependent ◽  
A Minor ◽  
Kinetics Of

The kinetics of the reduction of copper(II) to copper(I) by carbon monoxide in aqueous solutions have been investigated at 120 °C and carbon monoxide pressures up to 1360 atm. The reaction is homogeneous and proceeds by two paths, one of which is virtually independent of carbon monoxide pressure due to the formation of a stable cuprous carbonyl complex Cu(CO)+. The second reaction path contains both a pH-dependent and pH-independent component. The rate-determining step in both paths appears to be the decomposition of a carbon monoxide insertion complex by a cupric ion. Complexing ligands such as acetate were observed to have a minor inhibiting effect on the overall reaction.

scholarly journals PHYSICOCHEMICAL PROPERTIES OF THE PROTEOLYTIC ENZYME FROM THE LATEX OF THE MILKWEED, ASCLEPIAS SPECIOSA TORR. SOME COMPARISONS WITH OTHER PROTEASES

1940 ◽  
Vol 23 (3) ◽  
pp. 289-300 ◽  
Author(s):  
Theodore Winnick ◽  
Alva R. Davis ◽  
David M. Greenberg
Keyword(s):  
Reaction Rate ◽  
Enzyme Concentration ◽  
Second Order ◽  
Urea Solution ◽  
Reaction Products ◽  
Clotting Time ◽  
Milk Clotting ◽  
Enzyme Substrate ◽  
Asclepias Speciosa ◽  
Kinetics Of

1. The kinetics of milk clotting by asclepain, the protease of Asclepias speciosa, were investigated. At higher concentrations of enzyme, the clotting time was inversely proportional to the enzyme concentration. 2. The digestion of casein and hemoglobin in 6.6 M urea by asclepain follows the second order reaction rate. The rate was roughly second order for casein in water. 3. Evaluation of the nature of the enzyme-substrate intermediate indicates that one molecule of asclepain combines with one molecule of casein or hemoglobin in urea solution. 4. Inhibition by the reaction products was deduced from the fact that the digestion velocity of hemoglobin in urea solution varied with the asclepain concentration in agreement with the Schütz-Borissov rule.

scholarly journals Mechanism of Oxidation of (p-Substituted Phenylthio)acetic Acids withN-Chlorosaccharin

2011 ◽  
Vol 8 (1) ◽  
pp. 159-166 ◽  
Author(s):  
N. M. I. Alhaj ◽  
A. M. Uduman Mohideen ◽  
S. Sofia Lawrence Mary
Keyword(s):  
Phenyl Ring ◽  
Reaction Rate ◽  
Water Medium ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Rate Determining Step ◽  
Composition Variation ◽  
Mechanism Of Oxidation ◽  
Kinetics Of ◽  
Acetic Acids

The kinetics of oxidation of (phenylthio)acetic acid (PTAA) withN-chlorosaccharin (NCSA) have been studied potentiometrically in 80:20 (v/v) acetonitrile-water medium at 298 K. The reaction is first-order each with respect to PTAA and NCSA and shows a negative dependence on [H+]. NCSA itself is shown to be the active oxidizing species. Effects of ionic strength variation, added saccharin, added acrylonitrile, added NaCl and solvent composition variation have been studied. Effect of substituents on the reaction rate has been analysed by employing various (p-sustituted phenylthio)acetic acids. The electron-releasing substituent in the phenyl ring of PTAA accelerates the reaction rate while the electron-withdrawing substituent retards the rate. The excellently linear Hammett plot yields a large negative ρ value, supporting the involvement a chlorosulphonium ion intermediate in the rate-determining step.

Study on the Kinetics of Immersion of Photocatalyst in Bamboo

2012 ◽  
Vol 271-272 ◽  
pp. 218-221
Author(s):  
Xu Zhang ◽  
Zhong Feng Zhang ◽  
Kai Huang
Keyword(s):  
Reaction Rate ◽  
Reaction Order ◽  
Reaction Rate Constant ◽  
Exponential Factor ◽  
First Order ◽  
Higher Temperature ◽  
Three Stages ◽  
Increasing Temperature ◽  
Kinetics Of ◽  
Stable Stage

In order to improve the anti-mildew property of modified bamboo with photocatalyst, it used TiO2 which is one of the typical photocatalyst as the main study object to discussed the kinetics of immersion of photocatalyst in bamboo. The results show that immersion of TiO2 in bamboo can be divided into three stages, starting with the rapid immersion, the slow immersion in the middle stage, and the stable immersion in the later stage. In the stable stage, only little TiO2 immerse bamboo. The immersion rate is faster at higher temperature to take less time to reach equilibrium. By establishing the kinetic models, the reaction of immersion of photocatalyst can be regarded as the first order reaction with reaction order of 0.97, the reaction rate constant increases with increasing temperature, the activation energy is 5663.133J/mol, and the pre-exponential factor is 20.47h-1.

Kinetics of hydrolysis and rearrangements of S-acylthiouronium salts

1982 ◽  
Vol 47 (10) ◽  
pp. 2702-2710 ◽  
Author(s):  
Jaromír Kaválek ◽  
Jaroslav Novák ◽  
Vojeslav Štěrba
Keyword(s):  
Hydrochloric Acid ◽  
Dilute Hydrochloric Acid ◽  
Reaction Rate ◽  
Acetyl Derivative ◽  
Reaction Products ◽  
Acid Media ◽  
Hydroxyl Ion ◽  
Hydrochloric Acid Media ◽  
Kinetics Of ◽  
Acyl Derivatives

Kinetics of transformation of S-acetyl- and S-benzoylisothiouronium chlorides have been followed, and its reaction products in dilute hydrochloric acid media and aqueous buffers have been identified. In dilute hydrochloric acid the reaction rate is pH-independent, and the acetyl derivative reacts 8 times as rapidly as the benzoyl derivative. In acetate and phosphate buffers the decomposition rate of the both derivatives increases linearly with the buffer concentration. In acetate buffers the reaction rate is pH-independent, and acetate ion reacts as a nucleophile. In phosphate buffers the rate increases with increasing pH. The reaction catalyzed by the basic buffer component produces thiourea and carboxylic acid, that catalyzed by hydroxyl ion produces N-acetyl- or N-benzoylthiourea. The solvolysis rates of both S-acyl derivatives depend on percent composition of water-methanol solvent. The maximum solvolysis rate is reached in methanol with 25% (v/v) water.

scholarly journals Mechanism of Oxidation of (p-Substituted Phenylthio)acetic Acids withN-Bromophthalimide

2011 ◽  
Vol 8 (1) ◽  
pp. 1-8 ◽  
Author(s):  
N. M. I. Alhaji ◽  
A. M. Uduman Mohideen ◽  
K. Kalaimathi
Keyword(s):  
Reaction Rate ◽  
Reaction Medium ◽  
Solvent Mixture ◽  
Kinetics Of Oxidation ◽  
Rate Determining Step ◽  
Water Solvent ◽  
Rate Of Reaction ◽  
Species Effect ◽  
Kinetics Of ◽  
Acetic Acids

The kinetics of oxidation of (phenylthio)acetic acid (PTAA) byN-Bromophthalimide (NBP) in acetonitrile-water solvent mixture at 298 K in the presence of perchloric acid has been followed potentiometrically. The reaction is first-order each in NBP and PTAA and inverse fractional-order in H+. Also, it has been found that the reaction rate is not affected by changes in ionic strength of the reaction medium or by the addition of chemicals such as phthalimide, acrylonitrile and potassium bromide. However, an increase in the water content of the solvent mixture causes an increase in the rate of reaction. These observations have been well analyzed in favour of a SN2-type mechanism, involving NBP itself as the reactive species. Effect of substituents on the reaction rate has been analysed by employing various (p-sustituted phenylthio)acetic acids. The electron-releasing substituent in the phenyl ring of PTAA accelerates the reaction rate while the electron-withdrawing substituent retards the rate. The excellently linear Hammett plot yields a large negative ρ value, supporting the involvement a bromosulphonium ion intermediate in the rate-determining step.

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