scholarly journals The combustion of aromatic and alicyclic hydrocarbons. V. The products of combustion of benzene and its monoalkyl derivatives

1940 ◽  
Vol 175 (963) ◽  
pp. 539-563 ◽  
Keyword(s):  
Analytical Methods ◽  
Aliphatic Aldehyde ◽  
Combustion Products ◽  
Side Chain ◽  
Benzene Nucleus ◽  
Rapid Degradation ◽  
Cool Flame ◽  
Cool Flames ◽  
Stage Process ◽  
Characteristic Features

The progressive formation of products in the combustion of benzene and its monoalkyl derivatives has been studied by analytical methods, and the characteristic features of the isothermal reactions at various temperatures have been established. A cool-flame reaction of n -propylbenzene has also been investigated, and by comparison with corresponding isothermal combustions, it is concluded that the propagation of cool-flames is conditioned by the accumulation of a phenylalkyl hydroperoxide. The results are interpreted in the light of the theory of the two-stage process, and a schematic mechanism for the main combustion reaction is outlined. This comprises degradation of the side-chain (if present) and rupture of the benzene nucleus, followed by rapid degradation of the higher aliphatic aldehyde thus formed, yielding finally formaldehyde and the ultimate combustion products CO 2 , CO and H 2 O.

Hydrocarbon cool flames and the influence of hydrogen bromide

1974 ◽  
Vol 338 (1614) ◽  
pp. 327-340 ◽  
Keyword(s):  
Induction Period ◽  
Initial Conditions ◽  
Hydrogen Bromide ◽  
Initial Pressure ◽  
Pressure Change ◽  
Two Stage ◽  
Cool Flame ◽  
The Third ◽  
Cool Flames ◽  
Stage Process

Small amounts of hydrogen bromide added to n -pentane + 1.33 O 2 mixtures lower both the limiting pressure for the onset of two-stage ignition and also, to a smaller extent, that for the appearance of cool flames. The induction period preceding the first cool flame, ז 1 , is shown to be related to the initial pressure, P 0 , by a relation of the form ז 1 = kP -n 0 + c , where k , n and c are constants for a given set of initial conditions. The results show that c ≠ 0 and that the addition of hydrogen bromide reduces both ז 1 and c . However, since ז 1 ≽ c and c is always finite, it is clear that, even at temperatures above the ignition profiles, ignition continues to take place as a two-stage process. Plots of lg ז 1 against reciprocal temper­ature are invariably characterized by a well-defined change in slope and the temperature at which this occurs decreases with increasing concentration of hydrogen bromide, eventually reaching a limiting value of ca . 270 °C. Above this temperature the slopes of the plots are more or less independent of hydrogen bromide and correspond to an overall activation energy of 82 kJ mol -1 . Below this temperature the apparent energy of activation decreases from 206 to 113 kJ mol -1 as the concentration of hydrogen bromide is increased. Similarly there is a limiting concentration of the additive above which the pressure change accompanying the first cool flame is not appreciably increased except at low temperatures. In systems which exhibit multiple cool flames, the second and fourth cool flames are generally too indistinct for their characteristics to be measured with any accuracy. However, the third cool flame appears as a well-defined but relatively weak pressure pulse. In striking contrast to the behaviour of the first cool flame, neither the third cool flame nor the induction period preceding it is appreciably affected by the presence of hydrogen bromide. It thus appears that, although the halogen compound is pre­sumably involved in the chemical reactions leading to the first cool flame, the third cool flame is propagated by intermediates whose mode of forma­tion is independent of the additive.

CAPRICCIOʼS GENRE IN MANDOLIN MUSIC AT THE END OF THE 19th – THE EARLY OF THE 20th CENTURIES (for example of the concert pieces by С. Munier)

2019 ◽  
pp. 60-71
Author(s):  
N. V. Bashmakova ◽  
K. V. Kravchenko
Keyword(s):  
19Th Century ◽  
Analytical Methods ◽  
17Th Century ◽  
Point Of View ◽  
Historical Approach ◽  
The Creation ◽  
Characteristic Features ◽  
Concert Works ◽  
In The Beginning ◽  
The 19Th Century

The purpose of this article is process of analyzing in reference to concert capriccio by C. Munier for mandolin with piano («Bizzarria», op. 201, Spanish сapriccio, op. 276) from the point of view of their genre specificity. Methodology. The research is based on the historical approach, which determines the specifics of the genre of Capriccio in the music of the late 19th and early 20th centuries and in the work of C. Munier; the computational and analytical methods used to identify the peculiarities of the formulation and the performing interpretation of the original concert pianos for mandolins with piano that, according to the genre orientation (according to the composerʼs remarks), are defined as capriccio. Scientific novelty. The creation of Florentine composer,61mandolinist-vertuoso and pedagog C. Munier, which made about 300 compositions, is exponential for represented scientific vector. Concert works by C. Munier for mandolin and piano, created in the capriccio genre, were not yet considered in the art of the outdoors, as the creativity and composer’s style of the famous mandolinist. Conclusions. Thus, appealing to capriccio by С. Munier, which created only two works, embodied in them virtually all the evolutionary stages of the development of genre. In his opus of this genre there are a vocal, inherent in capriccio of the 17th century solo presentation, virtuosity, originality, which were embodied in the works of 17th – 18th centuries and the national color of the 19th century is clearly expressed. Thus, the Spanish capriccio is a kind of «musical encyclopedia» of national dance, which features are characteristic features of bolero, tarantella, habanera, and so forth. The originality of opus number 201 – «Bizzarria», is embodied in the parameters of shaping (expanded cadence of the soloist in the beginning) and emphasized virtuosity, which is realized in a wide register range, a variety of technical elements.

A mathematical model of the cool-flame oxidation of acetaldehyde

1971 ◽  
Vol 322 (1550) ◽  
pp. 377-403 ◽  
Keyword(s):  
Mathematical Model ◽  
Negative Temperature ◽  
Isothermal Oxidation ◽  
Limited Range ◽  
Detailed Model ◽  
Cool Flame ◽  
Induction Periods ◽  
Cool Flames ◽  
Satisfactory Account ◽  
Flame Oxidation

A detailed mathematical model of the non-isothermal oxidation of acetaldehyde has been found to give a realistic simulation of (i) single and multiple cool flames, their limits, amplitudes and induction periods; (ii) two-stage ignition; and (iii) the negative temperature coefficient for the maximum rate of slow combustion. A simplified form of the model, valid over a limited range of conditions, has been subjected to mathematical analysis to provide interpretations of the effects simulated by the detailed model. It is concluded that cool flames are thermokinetic effects often, but not exclusively, of an oscillatory nature, and that a satisfactory account of cool-flame phenomena must necessarily take reactant consumption into account.

scholarly journals DEFICIENCIES OF PLATO’S DEMOCRATIC SYSTEM

2019 ◽  
pp. 37-43
Author(s):  
Iryna Liashchenko
Keyword(s):  
Political System ◽  
Comparative Method ◽  
Human Soul ◽  
Systematic Method ◽  
Rapid Degradation ◽  
Methodological Basis ◽  
Democratic System ◽  
Characteristic Features ◽  
Democratic Election ◽  
Proper Operation

Main objective of the study. The objective of the study is to identify deficiencies of the democratic political system in order to protect democracy from rapid degradation into tyranny. Methodology. The systematic method was selected as the methodological basis for the research, as it enables the consideration of Plato’s democratic system as interdependent with other types of states. The comparative method proved to be effective for distinguishing the characteristic features of the aristocratic, timocratic, oligarchic, democratic and tyrannical state of the human soul and Plato’s system of government.Findings and conclusions. To enable proper operation of democracy, it requires protection from its own deficiencies. These deficiencies include the following: firstly, the flaw of haughty, arrogant attitude towards wise talented naturally eminent people and the fear of their coming to power originates from timocracy; secondly, just as «barns with gold» destroyed the timocratic and oligarchic type of state, so the residues of these «barns» turn into a flaw of democracy in the form of a social abyss between the most affluent and the most deprived strata of the society; thirdly, this is excessive will in democracy that is gradually turning into excessive slavery. Regarding the latter, Plato emphasizes the anarchic extreme of freedom in democracy, which turns it into arbitrariness. After all, in a democracy there is no need to participate in government; not necessarily obey; no go to war; neither obey peace or laws, etc. The main consequence of all these deficiencies in the democratic system is the fostering of a future tyrant rooting from a people’s deputy. Since the thinker points out that no matter how many times a tyrant appears, he does not come from somewhere, but only from a democratic election procedure.

The oxidation of hexane in the cool-flame region

1952 ◽  
Vol 212 (1110) ◽  
pp. 311-330 ◽  
Keyword(s):  
Atmospheric Pressure ◽  
Chemical Nature ◽  
Complex Mixture ◽  
Cyclic Ethers ◽  
Reaction Products ◽  
Cool Flame ◽  
Oxidation Of Methane ◽  
Cool Flames ◽  
Flame Region ◽  
Considerable Support

The chemical nature of the cool flame of hexane at 300°C, maintained stationary in a flow system at atmospheric pressure, has been investigated. The relative intensities of cool flames obtained from mixtures of differing composition have been measured, using a photomultiplier cell, and correlated with analyses made of the complex mixture of reaction products. The stationary two-stage flames which may be obtained at either higher oxygen concentrations or higher pressures than the cool flame are also described, and investigated similarly. The results are examined in the light of a theory of combustion of the higher hydrocarbons via aldehydes and hydroxyl radicals, which is an extension of a mechanism derived for the oxidation of methane. This receives considerable support, particularly from the identification of the complete homologous series of saturated aldehydes which can result from the hexane molecule. Associated with these reactions are others due to the greater stability of peroxide radicals at 300°C than at the higher temperatures of methane oxidation. Thus the building up of a partial pressure of hydroperoxide sufficient to ignite in the presence of oxygen may initiate the cool flame, and considerable amounts of cyclic ethers have been found which probably had a peroxidic precursor.

Cool flames in the combustion of toluene and ethylbenzene

1956 ◽  
Vol 238 (1213) ◽  
pp. 143-153 ◽  
Keyword(s):  
Hydrogen Peroxide ◽  
Light Intensity ◽  
Benzoic Acid ◽  
Aromatic Compounds ◽  
Flow System ◽  
Reaction Vessel ◽  
Static System ◽  
Cool Flame ◽  
Cool Flames ◽  
Blue Flame

The oxidation of toluene and ethylbenzene has been studied in a static system using a spherical reaction vessel (700 ml.) over the temperature range 300 to 500°C, and at total pressures up to 600 mm. Cool flames were observed in the oxidation of both hydrocarbons, but only the reaction of ethylbenzene gave rise to a ‘blue’ flame at higher temperatures. With neither hydrocarbon did periodicity in light intensity, or pressure pulses, occur. The ignition diagrams for 4 to 1 fuel + oxygen mixtures have been mapped out. With ethyl­benzene, the cool flame was maintained in a flow system, its spectrum was photographed and shown to be similar to that of fluorescent formaldehyde. The products of the reaction con­tained acetophenone, benzaldehyde and benzoic acid, phenol, quinol, hydrogen peroxide and methoxyhydroperoxide. The results have been compared with corresponding data for the oxidation of paraffin hydrocarbons, and it is concluded that, with both aromatic compounds, the processes allowing the possibility of cool-flame formation are themselves secondary in nature.

Isotopic tracer studies of the further reactions of pentenes in the combusion of pentane

1978 ◽  
Vol 364 (1718) ◽  
pp. 309-329 ◽  
Keyword(s):  
Molecular Mass ◽  
Peroxy Radical ◽  
Combustion Products ◽  
Secondary Products ◽  
Tracer Studies ◽  
Isotopic Tracer ◽  
Cool Flames ◽  
Hydroperoxy Radical ◽  
Lower Molecular Mass ◽  
Before And After

Detailed studies have been made of the mechanisms by which products other than the conjugate alkenes are formed when pentane undergoes combustion in the presence of small quantities of isotopically labelled pent-1-ene and pent-2-ene. Seven pentenes, specifically labelled with 14 C in different skeletal positions, have been synthesized and the fate of the labelled carbon atoms during combustion has been determined. Special attention has been paid to the formation and destruction of the pentadienes, acrolein and ethylene, as products derived from pent-1-ene. In particular, measurements have been made of the instantaneous fraction of the original pentene converted into each of these compounds and of the percentages have been shown to be derived exclusively from the pentenes, whilst acrolein and ethylene, which are complementary products resulting simultaneously from the same pentene molecule, are formed principally from the alkenes. It has also been possible to determine the distribution of the points of abstractive attack in the pentenes and the reactivity rations of pent-1-ene to secondary products. There are sharply defined changes in the relative rates for the pentadienes and pent-1-ene before and after the passage of cool flames; the results suggest that penta-1, 2-diene is oxidized to acrolein and ethylene. A significant amount of 2, 4-dimethyloxetan is formed from both pent-1-ene and pent-2-ene; this compound appears to be produced by a somewhat unusual route, involving the isomerization of one hydroperoxy radical to another through a peroxy radical. The majority of these compounds result from reactions involving free radial addition to the alkene molecule. However, abstractive modes of attack, although leading almost exclusively to the pentadienes, acrolein and ethylene, are quantitatively very important in terms of the total amount of attack on the pentenes. The principal products formed from the pentenes are only minor constituents of the combustion products of pentane. This shows that the coujugate alkenes do not play nearly as important a part in the combustion of pentane as they do in the case of alkanes of lower molecular mass.

Numerical studies of a thermokinetic model for oscillatory cool flame and complex ignition phenomena in ethanal oxidation under well-stirred flowing conditions

1989 ◽  
Vol 422 (1863) ◽  
pp. 289-310 ◽  
Keyword(s):  
Numerical Study ◽  
Thermal Characteristics ◽  
Kinetic Scheme ◽  
Ambient Conditions ◽  
Two Stage ◽  
Experimental Conditions ◽  
Cool Flame ◽  
Cool Flames ◽  
Spatial Uniformity ◽  
Acetyl Radical

A numerical study has been undertaken to predict quantitatively each of the non-isothermal reaction modes (stationary-state reaction, oscillatory cool flames and oscillatory two-stage and multiple-stage ignitions) associated with the oxidation of ethanal in a non-adiabatic well-stirred flow system (0.5 dm 3 ) at a mean residence time of 3 s. The kinetic scheme comprises 28 species involved in 60 reactions and it is coupled to the thermal characteristics through enthalpy change in each step, heat capacities of the major components and a heat transfer coefficient appropriate to heat loss through the reaction vessel wall. Spatial uniformity of temperature and concentrations is assumed, matching the experimental conditions. Very satisfactory accord is obtained between the experimentally measured and predicted location of the different reaction modes in the ( p - T a ) ignition diagram (where p is pressure and T a is temperature at ambient conditions), and the time-dependent patterns for oscillatory reaction agree with experimental measurements. The competition between degenerate branching and non-branching reaction modes is governed ultimately by the equilibrium CH 3 +O 2 ⇌CH 3 O 2 . The predicted behaviour is found also to be especially sensitive to the rate of decomposition of the acetyl radical CH 3 CO + M → CH 3 + CO + M. Corrections for its pressure dependence are essential if the predicted form of the oscillatory cool flame region in the ( p - T a ) diagram is to match the experimental results. Variations of the rate of this reaction also give new kinetic insight into the origins of complex oscillatory wave-forms for cool flames that have been observed experimentally. Relationships between the results of the detailed kinetic computations and the predictions from a three-variable, thermokinetic model are examined. This model is the simplest of all reduced schemes that makes successful predictions of two-stage ignition phenomena.

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 effect of hydrogen bromide on the products of the cool-flame combustion of n -pentane

1974 ◽  
Vol 341 (1625) ◽  
pp. 195-212 ◽  
Keyword(s):  
Initial Temperature ◽  
Hydrogen Bromide ◽  
Transient Temperature ◽  
Cool Flame ◽  
Flame Combustion ◽  
Cool Flames ◽  
Main Effect ◽  
Halogen Compound ◽  
Almost All ◽  
Uncatalysed Reaction

Detailed studies have been made of the products of the cool-flame combustion of n -pentane in the absence and presence of small concentrations (2-6 vol. %) of added hydrogen bromide. In the uncatalysed reaction, acetone and acetaldehyde are the principal products formed at low temperatures during the induction period preceding the first cool flame but increasing amounts of C 5 alkenes and O-heterocycles start to be formed as the initial temperature is increased. The main effect of hydrogen bromide is to increase dramatically the yields of C 5 ketones at the expense of almost all the other products. The results indicate that in the absence of the halogen compound the principal fate of the initially formed pentylperoxy radicals is isomerisation to hydroperoxypentyl radicals. At 250 °C, the latter radicals mainly add on further oxygen and are eventually converted to pentanedihydroperoxides; at higher temperatures, the hydroperoxypentyl radicals tend increasingly to decompose directly to give principally pentenes and C 5 O-heterocycles. Hydrogen bromide alters the mechanism operating with binary mixtures primarily by providing a source of readily abstractable hydrogen and thus enhancing the formation of pentenemonohydroperoxides. Control experiments on the homogeneous breakdown of pentane-2-monohydroperoxide show that the principal decomposition product is pentan-2-one and thus confirm the probable importance of pentanemonohydroperoxides as intermediates in the HBr-promoted reaction. Studies of the chemical changes accompanying the passage of cool flames show that these vary considerably with the prevailing conditions as well as with the number of previous cool flames which have propagated through the mixture. Hydrogen bromide causes well-defined differences in the nature and distribution of the products of the combustion of n -pentane, although these changes are not as great as those brought about by the passage of cool flames which generally lead to considerable transient temperature rises in the system.

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