THE THERMAL DECOMPOSITION OF PERCHLORIC ACID VAPOR<sup>1,2</sup>

Levy, Joseph B.

doi:10.1021/j100812a030

Cited by 61 publications

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“…On the other hand, the decomposition of 83-100% HCIO, has received considerable attention (3)(4)(5)(6)(7)(8), as has the decomposition of HC10, vapor (9)(10)(11)(12).…”

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confidence: 99%

Kinetics of Thermal Decomposition of Aqueous Perchloric Acid

Henderson¹,

Miasek²,

Swaddle³

1971

Can. J. Chem.

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Thermal decpmposition of 1.1-6.6 m aqueous perchloric acid at 295-322" yields oxygen, chlorine, and a small quantity of hydrochloric acid. The initial rates of decomposition have been measured, using a perchlorate ion activity electrode, and show 3.5 order dependence on the stoichiometric perchloric acid concentration; the corresponding rate coefficient and activation energy at 300.0" are 3.1 x lo-' tn-2.5 s-' and 84 kcal mole-', respectively. The order of reaction with respect to time is less than 3.5 and depends upon the initial perchloric acid concentration; this effect is due to acceleration of the decomposition by the reaction products, notably chloride ion. It is suggested that the ratedetermining step in the decomposition of aqueous perchloric acid is the reaction of two undissociated HC10, molecules to give H 2 0 , CIO,, and C10,. Perchloric acid is used extensively in physical studies of phenomena in aqueous solution, since it is the strongest of the common acids and also because its anion has remarkably little tendency to form complexes with metal ions. The aqueous acid is, however, thermodynamically unstable (AGO = -26.3 kcal/mole-' at 25" for the hypothetical 1 rn solution (1)) with respect to decomposition to oxygen, chlorine, and water, and it is clear that the kinetics of this decomposition must be known if the acid is to be used in extending studies of aqueous electrolyte solutions to high temperatures.Accordingly, the present study was designed primarily to provide empirical rate data on the decomposition of aqueous perchloric acid as a function of temperature, and over a concentration range which would include the commonlychosen "swamping electrolyte" values, 1-6 m. A literature search for such information was unsuccessful, although it has been reported (2) that no chlorine, DOCI, DCIO,, or DCIO, can be detected spectroscopically in 1 m DCIO, after several days in a titanium vessel with sapphire windows at 250". On the other hand, the decomposition of 83-100% HCIO, has received considerable attention (3-8), as has the decomposition of HC10, vapor (9-12). ExperimentalAll the stock chemicals used in this study were "Baker Analyzed" reagent grade, with the exception of ammonium nitrate (Matheson, Coleman and Bell) and sodium nitrate (Fisher Certified reagent). The perchloric acid (72%) was used without further purification; the experi-'To whom correspondence should be addressed. mental results were independent of the manufacturer's batch. Lithium perchlorate trihydrate was made from lithium carbonate and perchloric acid. Distilled water was passed through Barnstead deionizer and organic removal cartridges before use. Red mercuric oxide was used as the primary standard in acidimetry. Spectrophotometric measurements were made using a Cary Model 15 spectrometer.The pressure vessels used consisted of a cylindrical body (2.54 cm i.d. x 4.60 cm 0.d.) of ATL-40 commercially pure titanium, 0.2% palladium alloy (Atlas Titanium, Welland, Ontario), with a plug of the same material, such that the cavity volum...

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“…On the other hand, the decomposition of 83-100% HCIO, has received considerable attention (3)(4)(5)(6)(7)(8), as has the decomposition of HC10, vapor (9)(10)(11)(12).…”

mentioning

confidence: 99%

Kinetics of Thermal Decomposition of Aqueous Perchloric Acid

Henderson¹,

Miasek²,

Swaddle³

1971

Can. J. Chem.

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“…At that time only the uncatalyzed thermal decomposition of perchloric acid had been studied (4). This reaction appears to be heterogeneous in Pyrex glass reaction vessels at low temperatures (4-6) but homogeneous at high temperatures (4,6).…”

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confidence: 99%

The Decomposition of Perchloric Acid on Metal Oxide Catalysts

Gilbert¹,

Jacobs²

1971

Can. J. Chem.

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The thermal decomposition of perchloric acid has been investigated on five Harshaw catalysts: copper chromite, alumina, iron(II1) oxide, copper(I1) oxide, and manganese(1V) oxide (the last three being supported on alumina). Manganese(1V) oxide gave complex kinetics which were not fully analyzed but on the other four catalysts the reaction was.first order. Activation energies were: copper chromite, 54 kcal/mol; alumina, 28.8 kcal/mol; iron(II1) oxide, 28.6.kcal/mol; copper(I1) oxide, 39.0 kcal/mol. A mechanism is proposed for the decomposition which involves proton transfer to an acceptor (typically an 0'-ion) in the catalyst surface followed by decomposition of the CI0,-anion formed in this process. Some observations on the catalyzed thermal decomposition of ammonium perchlorate are presented. L'Ctude de la dtcomposition thermique de I'acide perchlorique a Ct C faite a partir de cinq catalyseurs de Harshaw: le chromite de cuivre, I'alumine, les oxydes de fer(III), de cuivre(I1) et de manganeseQV) (les trois derniers ayant comme support I'alumine). L'oxyde de manganese(1V) donne des cinetiques complexes qui n'ont pas kt6 completement ClucidCes mais pour les quatre autres catalyseurs, la reaction est du premier ordre. Les energies d'activation sont de 54 kcal/mol pour le chromite de cuivre, de 28.8 kcal/mol pour I'alumine, de 28.6 kcal/mol pour I'oxyde de fer(II1) et de 39.0 kcal/mol pour I'oxyde de cuivre(I1). Un mecanisme est propose pour la dCcomposition: il y a transfert de proton sur un accepteur (un ion 0'-typique) a la surface du catalyseur puis dCcomposition de I'anion C10,-form6 dans ce processus. Quelques observations sur la decomposition thermique catalysie du perchlorate d'ammonium sont aussi presentees.

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“…) -6-flame. For instance, the H 2 -HCl0 4 flame haE an act'.vation energy of 15 kcal/mole(4) as compared to 45 kcal/Taole for tne pure HCI 4 flame (56).) These results suggest that the NH 3 /HC10 4 reaction is fast and has a low activation energy, as may be expected.…”

Section: Iia(vi) )mentioning

confidence: 53%