The cool-flame oxidation of 3-methylpentane

1972 ◽  
Vol 329 (1579) ◽  
pp. 433-452 ◽  
Keyword(s):  
Hydrogen Transfer ◽  
Detailed Comparison ◽  
Combustion Products ◽  
Experimental Conditions ◽  
Cool Flame ◽  
Slow Combustion ◽  
Flame Region ◽  
The Difference ◽  
Increasing Temperature ◽  
Flame Oxidation

Kinetic and analytical studies of the gaseous oxidation of 3-methylpentane have been carried out both under slow combustion conditions and more especially in the cool-flame region. Analysis of the complex mixtures of in termediate products provides strong evidence for the occurrence of 3-methylpentylperoxy radical isomerization, which leads initially to the formation mainly of the corresponding β- and γ-hydroperoxyalkyl radicals. Detailed comparison of the yields of partial combustion products with those obtained from 3-ethylpentane under similar experimental conditions shows that formation of γ-hydro-peroxyalkyl radicals takes place less readily during the oxidation of 3-methylpentane due to the restricted number of modes of 1:6 hydrogen transfer. In consequence, this branched C 6 alkane gives smaller yields of the corresponding O -heterocycles but larger amounts of β-scission products. During the isomerization of 3-methylpentylperoxy radicals there is evidence for the occurrence of some alkyl group shifts. The results show that there is a somewhat greater tendency for m ethyl groups to migrate than there is for ethyl groups, the difference becoming more marked with increasing temperature.

The cool-flame combustion of decane

1982 ◽  
Vol 382 (1783) ◽  
pp. 429-440 ◽  
Keyword(s):  
Carbonyl Compounds ◽  
Hydrogen Bromide ◽  
Combustion Products ◽  
Cool Flame ◽  
Flame Combustion ◽  
Hydroperoxide Formation ◽  
Slow Combustion ◽  
Flame Region ◽  
Increasing Temperature ◽  
Oxidative Attack

Three approaches have been used to elucidate the mechanism of combustion of decane in the cool-flame region. First, measurements have been made of cool-flame and ignition parameters. These show a well defined change in activation energy at about 530 K. Second, analytical studies have been made of the effect of increasing temperature on the combustion products. These indicate that hydroperoxide formation ceases and that C 10 O-heterocycles become the predominant products at 500-530 K; the relative amounts of decanal and decanone do not however change. Finally, small amounts of hydrogen bromide have been added. These cause the complete conversion of hydroperoxides into decanones even at low temperatures; no lower carbonyl compounds are formed above 500 K. This work has led to two principal conclusions. One, which is shown by all three methods of study, is that the cool-flame combustion of decane involves two distinct mechanisms with a transition at 500-530 K. The other is that the selectivity of initial oxidative attack on decane remains low over the whole of the slow combustion and cool-flame regions between 440 and 680 K, suggesting that hydroxyl radicals are the main attacking species throughout.

Alkylperoxy radical rearrangements during the gaseous oxidation of isobutene

1963 ◽  
Vol 273 (1354) ◽  
pp. 427-434 ◽  
Keyword(s):  
Methyl Ethyl Ketone ◽  
Peroxy Radical ◽  
Methyl Ethyl ◽  
Isotopic Tracer ◽  
Cool Flame ◽  
Cool Flames ◽  
Tracer Techniques ◽  
Slow Combustion ◽  
Flame Region ◽  
Subsequent Decomposition

Isotopic tracer techniques have been used to elucidate the mechanism of production of ketones in the gaseous oxidation of isobutane. Both acetone and methyl ethyl ketone are formed from this hydrocarbon, the former predominating in the products of slow combustion and the latter in the products of cool flames. Addition of [1,3- 14 C] acetone to reacting isobutane + oxygen mixtures has established that none of the methyl ethyl ketone formed in the cool-flame region and only 25% of that formed during slow combustion arises from further reactions of acetone. The formation of methyl ethyl ketone probably involves predominantly rearrangement and subsequent decomposition of the tert .-butyl peroxy radical and this indeed appears to be the almost exclusive fate of this radical under cool-flame conditions.

The non-isothermal oxidation of 2-methylpentane. II. The chemistry of cool flames

1967 ◽  
Vol 298 (1453) ◽  
pp. 204-237 ◽  
Keyword(s):  
Flame Temperature ◽  
Complex Mixture ◽  
Isothermal Oxidation ◽  
Qualitative Description ◽  
Cool Flame ◽  
Slow Combustion ◽  
Aldehydes And Ketones ◽  
Flame Region ◽  
Alkylperoxy Radicals ◽  
Liquid Chromatographic

The products of all the modes of non-isothermal oxidation of 2-methylpentane by molecu­lar oxygen and of the attendant slow combustion reactions have been analysed by gas-liquid chromatographic and chemical methods. Oxidation in the cool-flame temperature range produces more than forty molecular species, including O -heterocycles, peroxides, alkenes and saturated and unsaturated aldehydes and ketones. A good qualitative description of the mode of formation of this complex mixture and of its variation with temperature is afforded by the alkylperoxy radical isomerization theory. This theory is developed semi-quantitatively and is in reasonable agreement with the quantitative experimental results. It is concluded that chain propagation in the cool-flame region occurs predominantly by attack on the fuel by hydroxyl radicals; the resulting oxidation is rapid and unselective. In contrast, at temperatures too low for cool-flame formation alkylperoxy radicals are the likely chain-propagating species, whereas at temperatures above the upper cool-flame limit hydroperoxy radicals probably propagate the chain. The mechanism of chain branch­ing is not clear but it is established that, in the cool-flame region, peroxidic compounds are involved.

The cool-flame oxidation of 3-ethylpentane

1971 ◽  
Vol 325 (1563) ◽  
pp. 469-492 ◽  
Keyword(s):  
Carbon Number ◽  
Sole Source ◽  
Initial Reaction ◽  
Cool Flame ◽  
Cool Flames ◽  
Lower Molecular Mass ◽  
Flame Region ◽  
Group Migration ◽  
Flame Oxidation ◽  
Alkylperoxy Radicals

Detailed studies have been carried out of the combustion of 3-ethylpentane with special reference to the chemical changes taking place in the cool-flame region, where at least 74 individual products are formed. At ca . 300 °C, the first products to appear are 3-ethylpent-1-ene and 3-ethylpent-2-ene, C 7 O -heterocycles and alkenes of carbon number less than seven; the rates of consumption of 3-ethylpentane and of formation of all products increase dramatically just before propagation of the first cool-flame but do not vary appreciably when subsequent cool-flames pass. As the temperature is raised to ca . 400 °C, the quantities of 3-ethylpentane consumed and of lower molecular mass products formed increase markedly while the amounts of most C 7 products decrease. Consideration of the analytical results indicates that alkylperoxy radical isomerization plays an important part in the primary chain-propagation cycle both in and out of the cool-flame region and at temperatures as high as 400 °C. It appears that the initial reaction of alkyl radicals with oxygen takes place, largely, if not exclusively, by direct addition to form alkylperoxy radicals. Different modes of isomerization of these radicals leads to the wide variety of products found and decomposition of the a-hydroperoxyalkyl radicals by direct loss of HO 2 is probably the sole source of the conjugate alkenes. The results also provide the first recorded evidence of ethyl group migration during alkylperoxy radical isomerization.

scholarly journals Potential Pitfalls in Membrane Fouling Evaluation: Merits of Data Representation as Resistance Instead of Flux Decline in Membrane Filtration

Membranes ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 460
Author(s):  
Bastiaan Blankert ◽  
Bart Van der Bruggen ◽  
Amy E. Childress ◽  
Noreddine Ghaffour ◽  
Johannes S. Vrouwenvelder
Keyword(s):  
Membrane Fouling ◽  
Membrane Filtration ◽  
Data Representation ◽  
Strong Impact ◽  
Experimental Conditions ◽  
Permeable Membrane ◽  
Dead End ◽  
Flux Decline ◽  
The Difference ◽  
Filtration Flux

The manner in which membrane-fouling experiments are conducted and how fouling performance data are represented have a strong impact on both how the data are interpreted and on the conclusions that may be drawn. We provide a couple of examples to prove that it is possible to obtain misleading conclusions from commonly used representations of fouling data. Although the illustrative example revolves around dead-end ultrafiltration, the underlying principles are applicable to a wider range of membrane processes. When choosing the experimental conditions and how to represent fouling data, there are three main factors that should be considered: (I) the foulant mass is principally related to the filtered volume; (II) the filtration flux can exacerbate fouling effects (e.g., concentration polarization and cake compression); and (III) the practice of normalization, as in dividing by an initial value, disregards the difference in driving force and divides the fouling effect by different numbers. Thus, a bias may occur that favors the experimental condition with the lower filtration flux and the less-permeable membrane. It is recommended to: (I) avoid relative fouling performance indicators, such as relative flux decline (J/J0); (II) use resistance vs. specific volume; and (III) use flux-controlled experiments for fouling performance evaluation.

scholarly journals Validation of a Method Based on Triglycerides for the Detection of Low Percentages of Hazelnut Oil in Olive Oil by Column Liquid Chromatography

2007 ◽  
Vol 90 (5) ◽  
pp. 1346-1353 ◽  
Author(s):  
Diego L García-González ◽  
María Viera-Macías ◽  
Ramón Aparicio-Ruiz ◽  
Maria T Morales ◽  
Ramón Aparicio
Keyword(s):  
Liquid Chromatography ◽  
Olive Oil ◽  
Carbon Number ◽  
Hazelnut Oil ◽  
Equivalent Carbon Number ◽  
Experimental Conditions ◽  
Mathematical Algorithm ◽  
Relative Standard ◽  
Triglyceride Content ◽  
The Difference

Abstract The difference between theoretical and empirical triglyceride content is a powerful tool to detect the presence of any vegetable oil in olive oil. The current drawback of the method is the separation between equivalent carbon number ECN42 compounds, which affects the reliability of the method and, hence, its cutoff limit. The determination of the triglyceride profile by liquid chromatography using propionitrile as the mobile phase has recently been proposed to improve their quantification, together with a mathematical algorithm whose binary response determines the presence or absence of hazelnut oil. Twenty-one laboratories from 9 countries participated in an interlaboratory study to evaluate the performance characteristics of the whole analytical method. Participants analyzed 12 samples in duplicate, split into 3 intercomparison studies. Statistically significant differences due to the experimental conditions were found in some laboratories, which were detected as outliers by use of Cochran's and Grubbs' tests. The relative standard deviations (RSD) for repeatability and reproducibility were determined following the AOAC Guidelines for Collaborative Studies. The analytical properties of the method were determined by means of the sensitivity (0.86), selectivity (0.94), and reliability (72) for a cutoff limit of 8 (probability 94).

scholarly journals Alpha EEG Frontal Asymmetries during Audiovisual Perception in Cochlear Implant Users

2015 ◽  
Vol 54 (06) ◽  
pp. 500-504 ◽  
Author(s):  
A. G. Maglione ◽  
A. Scorpecci ◽  
P. Malerba ◽  
P. Marsella ◽  
S. Giannantonio ◽  
...  
Keyword(s):  
Cochlear Implant ◽  
Alpha Rhythm ◽  
Normal Hearing ◽  
Experimental Conditions ◽  
Audiovisual Perception ◽  
Audiovisual Stimuli ◽  
The Difference ◽  
Eeg Alpha ◽  
The One ◽  
Hearing Children

SummaryObjectives: The aim of the present study is to investigate the variations of the electroencephalographic (EEG) alpha rhythm in order to measure the appreciation of bilateral and unilateral young cochlear implant users during the observation of a musical cartoon. The cartoon has been modified for the generation of three experimental conditions: one with the original audio, another one with a distorted sound and, finally, a mute version.Methods: The EEG data have been recorded during the observation of the cartoons in the three experimental conditions. The frontal alpha EEG imbalance has been calculated as a measure of motivation and pleasantness to be compared across experimental populations and conditions.Results: The EEG frontal imbalance of the alpha rhythm showed significant variations during the perception of the different cartoons. In particular, the pattern of activation of normal-hearing children is very similar to the one elicited by the bilateral implanted patients. On the other hand, results related to the unilateral subjects do not present significant variations of the imbalance index across the three cartoons.Conclusion: The presented results suggest that the unilateral patients could not appreciate the difference in the audio format as well as bilaterally implanted and normal hearing subjects. The frontal alpha EEG imbalance is a useful tool to detect the differences in the appreciation of audiovisual stimuli in cochlear implant patients.

Combined Experimental and CFD Study of a HP Blade Multi-Pass Cooling System

2009 ◽  
Author(s):  
D. Jackson ◽  
P. Ireland ◽  
B. Cheong
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Cooling System ◽  
Detailed Comparison ◽  
Bulk Temperature ◽  
Internal Cooling ◽  
3 Dimensional ◽  
Turbine Cooling ◽  
Cooling Hole ◽  
The Difference

Progress in the computing power available for CFD predictions now means that full geometry, 3 dimensional predictions are now routinely used in internal cooling system design. This paper reports recent work at Rolls-Royce which has compared the flow and htc predictions in a modern HP turbine cooling system to experiments. The triple pass cooling system includes film cooling vents and inclined ribs. The high resolution heat transfer experiments show that different cooling performance features are predicted with different levels of fidelity by the CFD. The research also revealed the sensitivity of the prediction to accurate modelling of the film cooling hole discharge coefficients and a detailed comparison of the authors’ computer predictions to data available in the literature is reported. Mixed bulk temperature is frequently used in the determination of heat transfer coefficient from experimental data. The current CFD data is used to compare the mixed bulk temperature to the duct centreline temperature. The latter is measured experimentally and the effect of the difference between mixed bulk and centreline temperature is considered in detail.

The diffusion of 75Se(IV) in Beishan granite – temperature, oxygen condition and ionic strength effects

2018 ◽  
Vol 107 (1) ◽  
pp. 39-54
Author(s):  
Chunli Wang ◽  
Xiaoyu Yang ◽  
Jiangang He ◽  
Fangxin Wei ◽  
Zhong Zheng ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Effective Diffusion ◽  
Aerobic Condition ◽  
Double Layers ◽  
Solution Viscosity ◽  
Formation Factor ◽  
Experimental Conditions ◽  
Beishan Granite ◽  
Oxygen Condition ◽  
The Difference

Abstract To explore the diffusion behavior of 75Se(IV) in Beishan granite (BsG), the influences of temperature, oxygen condition and ionic strength were investigated using the through-diffusion experimental method. The effective diffusion coefficient De of 75Se(IV) in BsG varied from 4.21×10−14 m2/s to 3.19×10−13 m2/s in our experimental conditions, increased with increasing temperature. The formation factor Ff of BsG was calculated to be nearly constant in the range of temperatures investigated, suggesting that the inner structure of BsG had no significant change in the temperature range of 20–55°C. Meanwhile, the De values of 75Se(IV) in BsG under anaerobic condition was significantly larger than that under aerobic condition, which may be attributed to the difference in the sorption characteristics and species distribution of Se and pH values. Moreover, the diffusion of 75Se(IV) was promoted with ionic strength increased from 0.01 M to 0.1 M, and then decreased at 0.5 M, mainly due to the combined effects of reduced double layers with increased ionic strength and increase of the solution viscosity at higher ionic strength.

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