HYDRODESULPHURIZATION OF THIOPHENE: II. REACTIONS OVER A CHROMIA CATALYST

1962 ◽  
Vol 40 (5) ◽  
pp. 941-946 ◽  
Author(s):  
P. J. Owens ◽  
C. H. Amberg
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Mixed Oxide ◽  
Kcal Mole ◽  
Hydrogenation Activity ◽  
Flow Reaction

The hydrodesulphurization of thiophene to butane and H2S over chromia has been studied by flow and microreactor techniques. The sulphided, i.e. mixed oxide–sulphide, catalyst showed improved desulphurization activity compared to pure chromia, while butene hydrogenation activity was reduced by a factor of at least 103. The apparent activation energy of the flow reaction was 24–25 kcal/mole. No organosulphur compounds were found among the products. The reaction proceeded predominantly via butadiene and butene intermediates, with a preference for 1-butene; their rates of hydrogenation as well as the rates of isomerization of the butenes have been compared as a function of temperature. The reaction also partly went to completion at the original desulphurization site, without the desorption of intermediates, presumably by a series of analogous steps on the surface.

The Langmuir-Hinshelwood Reaction between Oxygen and CO at Ir(111) Surfaces

1979 ◽  
Vol 34 (1) ◽  
pp. 81-88 ◽  
Author(s):  
J. Küppers ◽  
A. Plagge
Keyword(s):  
Activation Energy ◽  
Computer Program ◽  
Apparent Activation Energy ◽  
Gas Phase ◽  
Close Agreement ◽  
Reaction Path ◽  
Kcal Mole ◽  
Reaction Step ◽  
Per Se ◽  
Reaction Processes

Abstract The reaction of oxygen and CO to form CO2 has been investigated using an Ir (111) surface as an acting catalyst. Both instationary and stationary reaction processes have been established via separate gas exposing techniques. The instationary reaction process, achieved from coadsorbed CO and O which per se is an LH reaction is found to be controlled by an apparent activation energy of 10.7 kcal/mole. The stationary reaction with both CO and O2 continuously present in the gas phase has been simulated using a proper computer program, involving both LH and ER reaction steps. By comparison with experimental results, close agreement is found when ruling out any ER reaction step from the reaction path.

Kinetics of the addition of acids to olefins with and without boron fluoride catalysis

1967 ◽  
Vol 45 (1) ◽  
pp. 11-16 ◽  
Author(s):  
G. A. Latrèmouille ◽  
A. M. Eastham
Keyword(s):  
Activation Energy ◽  
Acetic Acid ◽  
Apparent Activation Energy ◽  
Trifluoroacetic Acid ◽  
Similar Rate ◽  
Ethylene Dichloride ◽  
Kcal Mole ◽  
Rate Law ◽  
Boron Fluoride ◽  
Kinetics Of

Isobutene reacts readily with excess trifluoroacetic acid in ethylene dichloride solution at ordinary temperatures to give t-butyl trifluoroacetate. The rate of the reaction is given, within the range of the experiments, by the expression d[ester]/dt = k[acid]2[olefin], and the apparent activation energy is about 6 kcal/mole. The rate of addition is markedly dependent on the strength of the reacting acid and is drastically reduced in the presence of mildly basic materials, such as dioxane. The boron fluoride catalyzed addition of acetic acid to 2-butene can be considered to follow a similar rate law, i.e. d[ester]/dt = k[acid·BF3]2[olefin], but only if some assumptions are made about the position of the equilibrium [Formula: see text]since only the 1:1 complex is reactive.

Relation between reduction and sulphidation process during the activation of a Co-Mo/Al2O3 hydrodesulphurization catalyst

1985 ◽  
Vol 50 (7) ◽  
pp. 1573-1581 ◽  
Author(s):  
Hana Zahradníková ◽  
Václav Kárník ◽  
Ludvík Beránek
Keyword(s):  
Activation Energy ◽  
Catalytic Activity ◽  
Apparent Activation Energy ◽  
Ethylene Hydrogenation ◽  
Hydrogenation Activity ◽  
Oxygen Chemisorption ◽  
Predominant Process ◽  
Chemisorption Capacity

The course of activation at 673 and 773 K of an industrial hydrodesulphurization catalyst CHEROX 36-01 was followed gravimetrically. Reduction with hydrogen, reductive sulphidation with a H2S/H2 mixture, non-reductive sulphidation with a H2S/He mixture and sulphidation of prereduced catalysts were compared. All sulphidation procedures are much faster than the reduction alone, the latter has, however, a higher apparent activation energy. In the reductive sulphidation with H2S/H2, reduction and sulphidation take place simultaneously, sulphidation being a predominant process at the beginning of the activation, especially at 673 K. It has been shown how the two processes can be decoupled or superposed. The catalytic activity in ethylene hydrogenation develops much more slowly when the catalyst is activated only by reduction than when it is activated by reductive sulphidation, in accordance with the relative velocities of these two activation procedures. The hydrogenation activity of catalysts reduced to a different extent correlates with their oxygen chemisorption capacity at 195 K.

scholarly journals The State of Water in Human and Dog Red Cell Membranes

1970 ◽  
Vol 55 (4) ◽  
pp. 451-466 ◽  
Author(s):  
F. L. Vieira ◽  
R. I. Sha'afi ◽  
A. K. Solomon
Keyword(s):  
Activation Energy ◽  
Cell Membrane ◽  
Apparent Activation Energy ◽  
Water Diffusion ◽  
Red Cells ◽  
Red Cell ◽  
Kcal Mole ◽  
Red Cell Membrane ◽  
Temperature Range ◽  
Human Red Cells

The apparent activation energy for the water diffusion permeability coefficient, Pd, across the red cell membrane has been found to be 4.9 ± 0.3 kcal/mole in the dog and 6.0 ± 0.2 kcal/mole in the human being over the temperature range, 7° to 37°C. The apparent activation energy for the hydraulic conductivity, Lp, in dog red cells has been found to be 3.7 ± 0.4 kcal/mole and in human red cells, 3.3 ± 0.4 kcal/mole over the same temperature range. The product of Lp and the bulk viscosity of water, η, was independent of temperature for both dog and man which indicates that the geometry of the red cell membrane is not temperature-sensitive over our experimental temperature range in either species. In the case of the dog, the apparent activation energy for diffusion is the same as that for self-diffusion of water, 4.6–4.8 kcal/mole, which indicates that the process of water diffusion across the dog red cell membrane is the same as that in free solution. The slightly, but significantly, higher activation energy for water diffusion in human red cells is consonant with water-membrane interaction in the narrower equivalent pores characteristic of these cells. The observation that the apparent activation energy for hydraulic conductivity is less than that for water diffusion across the red cell membrane is characteristic of viscous flow and suggests that the flow of water across the membranes of these red cells under an osmotic pressure gradient is a viscous process.

The decomposition of nitrous oxide catalysed by palladium-gold alloy wires

1966 ◽  
Vol 294 (1436) ◽  
pp. 1-19 ◽  
Keyword(s):  
Activation Energy ◽  
Nitrous Oxide ◽  
Fermi Level ◽  
Apparent Activation Energy ◽  
Frequency Factor ◽  
Kcal Mole ◽  
Dissociative Chemisorption ◽  
Retarding Effect ◽  
Effect Of Oxygen ◽  
Decomposition Of Nitrous Oxide

The rate of decomposition of nitrous oxide has been examined by pressure measurements, at temperatures between 500 and 900 °C and pressures between 10 -2 and 1 torr. The reaction is first order, but shows retardation by oxygen, but not nitrogen. Over the range of alloys, from Pd to nearly 40 at. % Pd, the velocity at 650 °C falls by a factor of 104, the apparent activation energy falls from 30 to 13 kcal/mole, and the retarding effect of oxygen falls to zero. Over this range of alloys the Fermi level which lies in the d band hardly changes but the concentration of the d band vacancies falls to zero. Over the range of alloys from 40 at. % Pd to Au the velocity at 650 °C remains constant but the apparent activation energy and frequency factor, which show an abrupt increase at 40 at. % Pd, show a continuous fall. The retarding effect of oxygen remains zero. In this range the Fermi level has entered the s band and increases to Au. A steady state treatment of an irreversible dissociative chemisorption of nitrous oxide, together with an oxygen chemisorption equilibrium, yields an equation for the velocity in quantitative agreement with the results found. It is also possible to account for the increase in apparent activation energy with oxygen coverage of the surface. The heat of adsorption of oxygen is derived as 32-2±2 kcal/mole, and the activation energy for chemisorption of nitrous oxide as 12-7 ±0-5 kcal/mole.

An ESR Investigation of Illuminated Polycrystalline TiO,

1977 ◽  
Vol 32 (5) ◽  
pp. 501-504 ◽  
Author(s):  
Chr. Dyrek ◽  
R. N. Schindler
Keyword(s):  
Heat Treatment ◽  
Activation Energy ◽  
Apparent Activation Energy ◽  
Paramagnetic Centers ◽  
Kcal Mole

Abstract Formation of paramagnetic centers in polycrystalline TiO2 samples and changes thereof upon heat treatment, addition of oxygen, and illumination, respectively, are described. From the tem­perature dependence of the disappearance of a photoprodueed Ti3+ signal with g= 1.96 an apparent activation energy of ~ kcal/mole is estimated for the electron annihilation processes.

Kinetics of the Solid State Reaction between MoO3 and SrCO3

1972 ◽  
Vol 27 (6) ◽  
pp. 1020-1022 ◽  
Author(s):  
G. Flor ◽  
V. Massarotti ◽  
R. Riccardi
Keyword(s):  
Activation Energy ◽  
Solid State ◽  
Apparent Activation Energy ◽  
Solid State Reaction ◽  
Diffusion Mechanism ◽  
Optical Observations ◽  
Kcal Mole ◽  
Temperature Range ◽  
Kinetics Of

AbstractThe solid state reaction MoO3 + SrCO3 → SrMoO4+ CO2 has been studied on mixtures of powdered reagents. Thermogravimetric measurements in the temperature range 412° -498 °C have been made on different mixtures and under different atmospheres. Moreover, optical observations and conductometric measurements have been carried out. The results show that the reaction is governed by a diffusion mechanism with an apparent activation energy of (60 ± 1) kcal/mole and that the main diffusing species is the Mo6+ ion.

Aqueous dissolution kinetics of pyrochlore, zirconolite and brannerite at 25, 50, and 75 °C

2000 ◽  
Vol 88 (9-11) ◽  
Author(s):  
S. K. Roberts ◽  
W.L. Bourcier ◽  
H.F. Shaw
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Dissolution Rate ◽  
Dissolution Kinetics ◽  
Kcal Mole ◽  
Dissolution Rates ◽  
Flow Through ◽  
Kinetics Of ◽  
Total Dissolution ◽  
Calculated Average

We measured the rates of dissolution of pyrochlore, zirconolite, and brannerite in pH-buffered solutions of pH 2, 4, 6, 8, 10, and 12 at temperatures of 25, 50, and 75 °C in flow-through reactors. The dissolution rates for all phases show a minimum near pH 8. Zirconolite dissolves the slowest of the three phases, with a slightly higher rate for pyrochlore and a much higher dissolution rate for brannerite. Brannerite dissolves as much has 30 times faster than zirconolite. The rates increase with temperature, but the magnitude of the increase varies with pH. The calculated average apparent activation energy for dissolution is 6±3 kcal/mole. Dissolution is non-stoichiometric at all pHs. Ti and Hf are released most slowly, and are often below detection limits (1 ppb for Ti, 0.2 ppb for Hf). Releases of Ca, U, Gd, and Ce appear to be stoichiometric below pH 8. At pH 8 and above only U is measurable in solution. Dissolution rates are slow under all conditions, and commonly in the range of 1-100 nm total dissolution/year (between 10

scholarly journals The Hydrothermal Stability and the Properties of Non- and Strongly-Interacting Rh Species over Rh/γ, θ-Al2O3 Catalysts

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 99
Author(s):  
Guanghao Cheng ◽  
Gurong Shen ◽  
Jun Wang ◽  
Yunhao Wang ◽  
Weibo Zhang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Aging Time ◽  
Reaction Path ◽  
Aging Treatment ◽  
Hydrothermal Stability ◽  
Hydrothermal Aging ◽  
Strongly Interacting

The present work reports the effects of γ-, θ-phase of alumina on the hydrothermal stability and the properties of non- and strongly-interacting Rh species of the Rh/Al2O3 catalysts. Comparing to γ-Al2O3, θ-Al2O3 can not only reduce the amount of occluded Rh but also better stabilize Rh during hydrothermal aging treatment. When the aging time was prolonged to 70 h, all the non-interacting Rh was transformed into strongly-interacting Rh and occluded Rh. The XPS results indicated that non- and strongly-interacting Rh might exist in the form of Rh/Rh3+ and Rh4+, respectively. CO-NO reaction was chosen as a probe reaction to research more information about non- and strongly-interacting Rh. The two Rh species had similar apparent activation energy (Eapp) of 170 kJ/mol, which indicated that non- and strongly-interacting Rh follow the same reaction path. The non-interacting Rh was removed from aged samples by the acid-treated method, and obtained results showed that only 2.5% and 4.0% non-interacting Rh was maintained in aged Rh/γ-Al2O3 and Rh/θ-Al2O3.

The activation energy U(T,B) in high temperature superconductor

2020 ◽  
Vol 92 (2) ◽  
pp. 20601
Author(s):  
Abdelaziz Labrag ◽  
Mustapha Bghour ◽  
Ahmed Abou El Hassan ◽  
Habiba El Hamidi ◽  
Ahmed Taoufik ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Activation Energy ◽  
Phase Diagram ◽  
High Temperature ◽  
Apparent Activation Energy ◽  
High Temperature Superconductor ◽  
Flux Flow ◽  
Resistivity Measurements ◽  
Vortex Phase ◽  
The Magnetic Field

It is reported in this paper on the thermally assisted flux flow in epitaxial YBa2Cu3O7-δ deposited by Laser ablation method on the SrTiO3 substrate. The resistivity measurements ρ (T, B) of the sample under various values of the magnetic field up to 14T in directions B∥ab-plane and B∥c-axis with a dc weak transport current density were investigated in order to determine the activation energy and then understand the vortex dynamic phenomena and therefore deduce the vortex phase diagram of this material. The apparent activation energy U0 (B) calculated using an Arrhenius relation. The measured results of the resistivity were then adjusted to the modified thermally assisted flux flow model in order to account for the temperature-field dependence of the activation energy U (T, B). The obtained values from the thermally assisted activation energy, exhibit a behavior similar to the one showed with the Arrhenius model, albeit larger than the apparent activation energy with ∼1.5 order on magnitude for both cases of the magnetic field directions. The vortex glass model was also used to obtain the vortex-glass transition temperature from the linear fitting of [d ln ρ/dT ] −1 plots. In the course of this work thanks to the resistivity measurements the upper critical magnetic field Hc2 (T), the irreversibility line Hirr (T) and the crossover field HCrossOver (T) were located. These three parameters allowed us to establish a phase diagram of the studied material where limits of each vortex phase are sketched in order to optimize its applicability as a practical high temperature superconductor used for diverse purposes.

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