Homogeneous gas-phase pyrolyses using a wall-less reactor. II. Absolute evaluation of surface effects with neopentane

Hutchings, David A.; Taylor, Jay E.; Frech, Kenneth J.

doi:10.1021/j100843a070

Cited by 6 publications

(8 citation statements)

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“…Our observations and conclusions, which have been summarized in communications during 1968 and 1969, are compared to those of other authors, particularly to the recent ones of Purnell and colleagues [13] and of Taylor and colleagues [14], [15].…”

Section: Introductionmentioning

confidence: 51%

“…In a short communication, Taylor and coworkers [15] have very recently pointed out that a stainless steel packing accelerates the global reaction of the neopentane pyrolysis, decreases its activation energy, and increases the ratio of methane to ethane. But it is possible that this packing accelerates the secondary decomposition of primary products (isobutene particularly) rather than the primary neopentane pyrolysis.…”

Section: (D)mentioning

confidence: 99%

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The pyrolysis of neopentane at small extents of reaction

Baronnet¹,

Dzierzynski²,

Côme³

et al. 1971

Int J of Chemical Kinetics

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The pyrolysis of neopentane, at small extents of reaction, was studied by gas chromatography, in Pyrex reaction vessels between 450' and 530°C and in the initial pressure range 25-200 mm Hg. At initial time, this thermal decomposition can be essentially represented by a homogeneous long-chain radical mechanism. The rate constant of the unimolecular initiation process is approximately given by the expressionThe initial rate constant of the global reaction (order s/z) is nearly equal to This reaction is strongly inhibited by propene or isobutene and self-inhibited by the isobutene formed; an interpretation of all these inhibition phenomena of the neopentane pyrolysis is proposed. Our observations and conclusions, which have been summarized in communications during 1968 and 1969, are compared to those of other authors, particularly to the recent ones of Purnell and colleagues [13] and of Taylor and colleagues [14], [15].

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Section: Introductionmentioning

confidence: 51%

Section: (D)mentioning

confidence: 99%

The pyrolysis of neopentane at small extents of reaction

Baronnet¹,

Dzierzynski²,

Côme³

et al. 1971

Int J of Chemical Kinetics

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“…The isomerization may be In the first determinations of the absolute proceed as effects of surfaces on various gas-phase pyrolyses using the wall-less reactor, results ranging from [I1 activation to inhibition have been noted. The compounds reported to date include neopentane (1,2) and ethane under both oxidative and [21 ' , , / / ' % nonoxidative conditions (3) and now cycloprov pane. Neopentane exhibits a strong positive surface effect with alteration of both products and activation energy.…”

Section: Introductionmentioning

confidence: 99%

Homogeneous Gas-phase Pyrolyses using a Wall-less Reactor. IV. Comparative Surface-Nonsurface Effects with Cyclopropane

Kulich¹,

Taylor²,

Hutchings³

1974

Can. J. Chem.

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The rates of pyrolysis of cyclopropane in nitrogen have been determined using a wall-less reactor at temperatures of 600-740 "C and a total pressure of 1 atm. In the presence of oxidized stainless steel. quartz, o r carbon coated steel rods the rate of conversion to propylene is 1.9 times the rate under homogeneous conditions. A maximum in surface effect was observed at S / V = 0.6 a n -' . A small but increased amount of methane and ethene are formed under surface conditions as compared to homogeneous conditions. Several possible mechanisms for the rate enhancement by surface are discussed. The most likely possibility is surface interaction with the cyclopropane molecule to form the diradical followed by its surface promoted conversion to propene. The importance of determining surface effects by comparing surface rates with totally homogeneous rates is emphasized.On a evalue les differentes vitesses de pyrolyse dans I'azote du cyclopropane en utilisant un reacteur sans paroi a des temperatures de 600 a 740 "C et a une pression totale d'un atmosphere. En presence de tiges d'acier recouvertes de quartz, de carbone ou d'acier inoxydable oxyde, la vitesse de transformation en propylene est superieure par un facteur de 1.9 a celle enregistree dans des conditions hornogenes. On a observe a S / V = 0.6 cm-' un effet de surface maximum. D e m&me, uneltgtre augmentation d e la quantite produite de methane et d'ethane a Ctt enregistree dans les conditions impliquant une surface par rapport aux conditions homogenes. On discute de plusieurs mecanismes probables tenant compte de I'augmentation de vitesse due a une interaction surface-cyclopropane conduisant i u n biradical puis a s a transformation, favorisee par la surface, en propene. On discute aussi de I'importance d'evaluer les effets de surface par comparaison entre les vitesses observtes lors de la presence d'une surface et celles obtenues dans des conditions parfaitement homogenes.[Traduit p a r le journal]Can.

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“…The purpose of this investigation is primarily to examine the initial stages of the oxygen-ethane reaction a t temperatures near 600°C under conditions free of heterogeneous catalysis. The wall-less technique was considered requisite to this study because of the following advantages over the conventional reactor: (1) the initial stages of the reaction can be studied in the absence of wall effects; (2) an absolute comparison of surface-versus-nonsurface conditions can be made; (3) highly reproducible data are obtained at very low conversions. With the low hydrocarbon injection rate (-20 ml/min), an extremely fast warm-up in the reactor is possible, and the problem of preliminary product formation in a preheater is avoided.…”

Section: Introductionmentioning

confidence: 99%

“…This paper deals with the reaction between oxygen and ethane at high temperatures and atmospheric pressure. The application of the wall-less technique [1,2] to this study permits a precise determination of reaction rates under totally homogeneous conditions; this has not been possible in previous investigations using conventional reactors. 'The oxidation of hydrocarbons at high temperatures ( > 500°C) produces predominantly cracking products (olefins and lower alkanes), in sharp contrast to the low-temperature reaction which produces oxidation products (alcohols, aldehydes, etc.)…”

Section: Introductionmentioning

confidence: 99%

Homogeneous gas‐phase pyrolyses with a wall‐less reactor. III. The oxygen–ethane reaction. A double reversal in oxygen and surface effects

Taylor

Kulich

1973

Int J of Chemical Kinetics

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The impact of surface and oxygen on the oxidative pyrolysis of ethane at temperatures above 590°C was studied using a wall-less reactor. At very low conversions under homogeneous conditions, ethene formation begins at the same temperature regardless of whether oxygen is present or absent. Between 0.00 and 0.13% conversion (592-632"C), the rate with oxygen is actually less than the rate in the absence of oxygen. A reversal occurs at about 633°C above which oxygen has a promoting effect. It is concluded that under homogeneous conditions the initiation step in the oxygen-promoted pyrolysis is the same as in the oxygen-free pyrolysis; therefore, initiation by direct attack of oxygen on ethane does not make an important contribution. The decrease in rate observed upon addition of oxygen implies the formation of the relatively unreactive HO2. radical. AS conversion of the HO2. radical to the more reactive H O . radical becomes significant, the reaction is highly accelerated. If a stainless steel surface is added, the reaction is inhibited at higher conversions in the presence of oxygen. Again at low conversions, a second reversal occurs, and the stainless steel surface acts as a promoter below 649°C. The rate of surfacecatalyzed ethene formation at 590°C equals the rate of homogeneous ethene formation at 630°C.

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Homogeneous gas-phase pyrolyses using a wall-less reactor. II. Absolute evaluation of surface effects with neopentane

Cited by 6 publications

References 0 publications

The pyrolysis of neopentane at small extents of reaction

The pyrolysis of neopentane at small extents of reaction

Homogeneous Gas-phase Pyrolyses using a Wall-less Reactor. IV. Comparative Surface-Nonsurface Effects with Cyclopropane

Homogeneous gas‐phase pyrolyses with a wall‐less reactor. III. The oxygen–ethane reaction. A double reversal in oxygen and surface effects

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