THE PHOTOLYSIS OF BIACETYL

1955 ◽  
Vol 33 (1) ◽  
pp. 39-46 ◽  
Author(s):  
P. Ausloos ◽  
E. W. R. Steacie
Keyword(s):  
Activation Energy ◽  
Excellent Agreement ◽  
Low Temperatures ◽  
Arrhenius Plot ◽  
Disproportionation Reaction ◽  
Methyl Radicals

The photolysis of biacetyl has been reinvestigated. The results are, in general, in excellent agreement with those of Blacet and Bell. Curvature occurs at low temperatures in the Arrhenius plot of [Formula: see text][Biacetyl], and this is attributed to wall reactions, and to the disproportionation reaction[Formula: see text]Azomethane–biacetyl mixtures have been photolyzed to give further information on these points. An activation energy of 8.5 kcal. has been found for the reaction of methyl radicals with biacetyl.

Direct observation of dienols produced by photochemical enolisation of α,β-unsaturated ketones: rates and activation parameters for dienol reketonisation via a 1,5-hydrogen shift

1987 ◽  
Vol 65 (8) ◽  
pp. 1867-1872 ◽  
Author(s):  
Randy M. Duhaime ◽  
Alan C. Weedon
Keyword(s):  
Activation Energy ◽  
Low Temperatures ◽  
Nmr Spectra ◽  
Arrhenius Plot ◽  
Activation Parameters ◽  
Activation Entropy ◽  
Hydrogen Shift ◽  
Unsaturated Ketones ◽  
Ultraviolet Light Irradiation ◽  
Stable Solutions

The production of stable solutions of Z-dienols by ultraviolet light irradiation of α,β-unsaturated ketones at low temperatures (ca. −76 °C) in d4-methanol is reported. The rates of reketonisation of the dienols via a 1,5-sigmatropic hydrogen shift were determined at various temperatures between −43 °C and + 2 °C by monitoring the proton nmr spectra of the dienols. From the data the activation parameters for the reaction were calculated. For the dienol Z-2-hydroxy-4-methyl-2,4-pentadiene, 2, derived from photoenolisation of 4-methyl-3-penten-2-one, 1, the activation energy from the Arrhenius plot is 62 ± 4 kJ/mol, and the activation entropy and enthalpy from the Eyring plot are −87 ± 15 J/mol K and 60 ± 4 kJ/mol, respectively. For the dienol Z-4-tert-butyl-2-hydroxy-2,4-pentadiene, 4, obtained from photoenolisation of 4,5,5-trimethyl-3-hexen-2-one, 3, the activation energy, entropy, and enthalpy were found to be 47 ± 5 kJ/mol, −135 ± 19 J/mol K, and 45 ± 5 kJ/mol, respectively.

Impurity Conduction in Silicon Carbide

2007 ◽  
Vol 556-557 ◽  
pp. 367-370 ◽  
Author(s):  
Michael Krieger ◽  
Kurt Semmelroth ◽  
Heiko B. Weber ◽  
Gerhard Pensl ◽  
Martin Rambach ◽  
...  
Keyword(s):  
Activation Energy ◽  
Low Temperature ◽  
Low Temperatures ◽  
Nearest Neighbor ◽  
Arrhenius Plot ◽  
Schottky Contacts ◽  
Steep Slope ◽  
Admittance Spectroscopy ◽  
Resistivity Measurements ◽  
Impurity Conduction

We report on admittance spectroscopy (AS) investigations taken on aluminum (Al)- doped 6H-SiC crystals at low temperatures. Admittance spectra taken on Schottky contacts of highly doped samples (NA ≥ 7.2×1017 cm-3) reveal two series of conductance peaks, which cause two different slopes of the Arrhenius plot. The steep slope is attributed to the Al acceptor, while the flatter one - obtained from the low temperature peaks - is attributed to the activation energy ε3 of nearest neighbor hopping. We propose a model, which explains the unexpected sharpness of the low temperature conductance peaks and the disappearance of these peaks for low acceptor concentrations. The model is verified by simulation, and the AS results are compared with corresponding results obtained from resistivity measurements taken on 4H- and the identical 6HSiC samples.

Tracer Impurity Diffusion in Liquid Metals: Au in Ga

1974 ◽  
Vol 29 (6) ◽  
pp. 959-960 ◽  
Author(s):  
P.-E. Eriksson ◽  
S. J. Larsson
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Low Temperatures ◽  
Arrhenius Plot ◽  
Liquid Metals ◽  
Impurity Diffusion ◽  
Straight Line ◽  
Linear Plot

The diffusion coefficient of 198Au in liquid Ga has been measured between 35 and 460 °C. The results can be represented by a linear plot of D vs T or by an Arrhenius plot. The latter yields the parameters D0 = 4.9·10-4 cm2/s and Q = 2.65 kcal/mol. However, some distinct departures from the straight line characteristics, showing a considerably higher “activation energy” at the low temperatures, suggest the possibility that clusters composed of two or several atoms may partake in diffusion.

SOME COMPLICATING FACTORS IN THE PHOTOLYSIS OF ACETONE

1955 ◽  
Vol 33 (1) ◽  
pp. 47-55 ◽  
Author(s):  
P. Ausloos ◽  
E. W. R. Steacie
Keyword(s):  
Low Temperatures ◽  
Room Temperature ◽  
Disproportionation Reaction ◽  
Methyl Radicals ◽  
Wall Effects ◽  
Arrhenius Plots ◽  
Complicating Factors ◽  
Low Pressures

The photolysis of acetone has been investigated at room temperature using low pressures and high intensities. In addition an investigation was made of the photolysis of azomethane–acetone mixtures. The results indicate that the curvature at low temperatures of Arrhenius plots of[Formula: see text][Acetone] is due to two causes (a) a reaction between methyl radicals and adsorbed acetone and (b) to the occurrence of the disproportionation reaction [Formula: see text]Confirmatory evidence for wall effects was obtained from experiments at low pressures and higher temperatures.

ON THE DIELECTRIC BEHAVIOR OF LiCo3/5Fe2/5VO4 CERAMICS

2010 ◽  
Vol 24 (07) ◽  
pp. 665-670
Author(s):  
MOTI RAM
Keyword(s):  
Activation Energy ◽  
Dielectric Constant ◽  
Frequency Dependence ◽  
Chemical Method ◽  
Arrhenius Plot ◽  
Dielectric Behavior ◽  
Tangent Loss ◽  
Low Frequencies ◽  
Different Temperatures ◽  
Tan Δ

The LiCo 3/5 Fe 2/5 VO 4 ceramics has been fabricated by solution-based chemical method. Frequency dependence of the dielectric constant (εr) at different temperatures exhibits a dispersive behavior at low frequencies. Temperature dependence of εr at different frequencies indicates the dielectric anomalies in εr at Tc (transition temperature) = 190°C, 223°C, 263°C and 283°C with (εr) max ~ 5370, 1976, 690 and 429 for 1, 10, 50 and 100 kHz, respectively. Frequency dependence of tangent loss ( tan δ) at different temperatures indicates the presence of dielectric relaxation in the material. The value of activation energy estimated from the Arrhenius plot of log (τd) with 103/T is ~(0.396 ± 0.012) eV.

THE REACTION OF METHYL RADICALS WITH FORMALDEHYDE

1959 ◽  
Vol 37 (9) ◽  
pp. 1462-1468 ◽  
Author(s):  
A. R. Blake ◽  
K. O. Kutschke
Keyword(s):  
Activation Energy ◽  
Kinetic Analysis ◽  
Addition Reactions ◽  
Methyl Radicals ◽  
Kcal Mole ◽  
A Value ◽  
Abstraction Reaction ◽  
Butyl Peroxide

The pyrolysis of di-t-butyl peroxide has been reinvestigated and used as a source of methyl radicals to study the abstraction reaction between methyl radicals and formaldehyde. At low [HCHO]/[peroxide] ratios the system was simple enough for kinetic analysis, and a value of 6.6 kcal/mole was obtained for the activation energy. At higher [HCHO]/[peroxide] ratios the system became very complicated, possibly due to the increased importance of addition reactions.

Oxygen diffusion in amorphous and partially crystalline gallium oxide

2019 ◽  
Vol 21 (8) ◽  
pp. 4268-4275 ◽  
Author(s):  
Alexandra von der Heiden ◽  
Manuel Bornhöfft ◽  
Joachim Mayer ◽  
Manfred Martin
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficients ◽  
Low Temperatures ◽  
Oxygen Diffusion ◽  
Gallium Oxide ◽  
Tracer Diffusion ◽  
Tof Sims ◽  
Tracer Diffusion Coefficients ◽  
Oxygen Tracer

We established a TTT diagram of crystallisation of gallium oxide. Determination of oxygen tracer diffusion coefficients by IEDP/ToF-SIMS allowed us to access the activation energy for amorphous GaO1.5 at low temperatures.

scholarly journals Pyrolysis Kinetic Parameters of Omari Oil Shale Using Thermogravimetric Analysis

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4060
Author(s):  
Ziad Abu El-Rub ◽  
Joanna Kujawa ◽  
Samer Al-Gharabli
Keyword(s):  
Activation Energy ◽  
Thermogravimetric Analysis ◽  
Kinetic Parameters ◽  
Oil Shale ◽  
Arrhenius Plot ◽  
Frequency Factor ◽  
Coefficient Of Determination ◽  
Assay Method ◽  
Temperature Integral ◽  
Integral Approximation

Oil shale is one of the alternative energies and fuel solutions in Jordan because of the scarcity of conventional sources, such as petroleum, coal, and gas. Oil from oil shale reservoirs can be produced commercially by pyrolysis technology. To optimize the process, mechanisms and rates of reactions need to be investigated. Omari oil shale formation in Jordan was selected as a case study, for which no kinetic models are available in the literature. Oil shale was analyzed using the Fischer assay method, proximate analysis (moisture, volatile, and ash), gross calorific value, elemental analysis (CHNS), and X-ray fluorescence (XRF) measurements. Non-isothermal thermogravimetric analysis was applied to study the kinetic parameters (activation energy and frequency factor) at four selected heating rates (5, 10, 15, and 20 °C/min). When oil shale was heated from room temperature to 1100 °C, the weight loss profile exhibited three different zones: drying (devolatilization), pyrolysis, and mineral decomposition. For each zone, the kinetic parameters were calculated using three selected methods: integral, temperature integral approximation, and direct Arrhenius plot. Furthermore, the activation energy in the pyrolysis zone was 112–116 kJ/mol, while the frequency factor was 2.0 × 107 − 1.5 × 109 min−1. Moreover, the heating rate has a directly proportional relationship with the rate constant at each zone. The three different methods gave comparable results for the kinetic parameters with a higher coefficient of determination (R2) for the integral and temperature integral approximation compared with the direct Arrhenius plot. The determined kinetic parameters for Omari formation can be employed in developing pyrolysis reactor models.

THE THERMAL DECOMPOSITION OF HYDROGEN PEROXIDE VAPOUR. II.

1947 ◽  
Vol 25b (2) ◽  
pp. 135-150 ◽  
Author(s):  
Paul A. Giguère
Keyword(s):  
Activation Energy ◽  
Hydrogen Peroxide ◽  
Thermal Decomposition ◽  
Low Temperatures ◽  
Hydrocyanic Acid ◽  
Quartz Surface ◽  
First Order ◽  
Acid Washing ◽  
Reaction Vessels ◽  
Low Pressures

The decomposition of hydrogen peroxide vapour has been investigated at low pressures (5 to 6 mm.) in the temperature range 50° to 420 °C., for the purpose of determining the effect of the nature and treatment of the active surfaces. The reaction was followed in an all-glass apparatus and, except in one case, with one-litre round flasks as reaction vessels. Soft glass, Pyrex, quartz, and metallized surfaces variously treated were used. In most cases the decomposition was found to be mainly of the first order but the rates varied markedly from one vessel to another, even with vessels made of the same type of glass. On a quartz surface the decomposition was preceded by an induction period at low temperatures. Fusing the glass vessels slowed the reaction considerably and increased its apparent activation energy; this effect was destroyed by acid washing. Attempts to poison the surface with hydrocyanic acid gave no noticeable result. The marked importance of surface effects at all temperatures is considered as an indication that the reaction was predominantly heterogeneous under the prevailing conditions. Values ranging from 8 to 20 kcal. were found for the apparent energy of activation. It is concluded that the decomposition of hydrogen peroxide vapour is not very specific as far as the nature of the catalyst is concerned.

Hydrogen Embrittlement Of Austenitic Stainless Steel

CORROSION ◽  
1965 ◽  
Vol 21 (2) ◽  
pp. 53-56 ◽  
Author(s):  
M. B. WHITEMAN ◽  
A. R. TROIANO
Keyword(s):  
Activation Energy ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Low Temperatures ◽  
High Strain ◽  
Complete Recovery ◽  
Strain Rates ◽  
Body Centered Cubic ◽  
Thin Sections ◽  
310 Stainless Steel

Abstract Type 310 stainless steel in thin sections was embrittled by hydrogen. The temperature and strain rate dependence of this embrittlement was almost analogous to that well-established for hydrogenated body-centered cubic (b.c.c.) metals, differing only in that at low temperatures and relatively high strain rates complete recovery in ductility was not achieved. The activation energy for recovery in ductility, determined by aging at several temperatures, was 10,900 cal/mole.

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