The effect of mechanical activation on the thermal decomposition of chalcopyrite

Experimental results on the influence of preliminary mechanical activation on the thermal decomposition of chalcopyrite are presented and discussed. The following experimental facts were found:

Catalytic decomposition of isopropyl alcohol on iron(II) sulfide

The decomposition of isopropyl alcohol on troilite (FeS) which was thermally activated at 873, 973 and 1073 K, is described in this paper. The catalyst subjected to thermal activation exhibits improved activity, which increases with temperature of activation. It has been observed that the apparent activation energy E and the preexponential factor A have a compensating effect. The experiments involving the preadsorption of pyridine have shown that this substance is preferentially and irreversibly adsorbed on hydrogenation active centers.

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Influence of rhenium additives on the activity of Nu/sibunite catalyst in transformations of isopropyl alcohol

The dehydrogenating and dehydrating properties of the Cu(2%)/sibunite catalyst with rhenium additives were studied in the transformations of isopropyl alcohol at 200—270 °C. The catalyst containing 0.25% Re was found to possess the maximum dehydrogenating activity at 200 °C.     

Effect of countercations in catalytic photooxidation of isopropyl alcohol by decatungstate isopolyanion

By utilizing homogeneous decatungstate solution, we have found a novel catalyst system for photooxidation of isopropyl alcohol under excess of O₂. The decatungstate with countercation ratio of K: TBA (tetrabutylammonium) = 3 : 1 shows an activity about double that of the homogeneous K or TBA salt of decatungstate. A new redox cycle considering the ion-pair between decatungstate and countercations is proposed.     

Self-assembled CuO nanoarchitectures and their catalytic activity in the thermal decomposition of ammonium perchlorate

CuO shuttle-like and flower-like nanocrystals were synthesized through a one-step, low-temperature solution-phase method in the presence of a cation surfactant, hexadecyl trimethyl ammonium bromide. These nanocrystals were studied as an additive for promoting the thermal decomposition of ammonium perchlorate (AP). With the addition of CuO shuttle-like and flower-like nanocrystals, the thermal decomposition temperature of AP decreased. The structure, particle size, and morphology of resulting CuO powders were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Thermogravimetric analysis technique was applied to investigate the thermal decomposition of mixtures of AP and as-prepared CuO nanocrystals.     

Evaluation of the catocene/graphene oxide nanocomposite catalytic activity on ammonium perchlorate thermal decomposition

A novel nanocomposite catalyst for thermal degradation of the ammonium perchlorate (AP) has been synthesized, and its effect on the thermal behavior of AP has been investigated. Preparation of the catalyst was carried out via functionalization of the graphene oxide with phenyl isocyanate and its noncovalent bonding to catocene. The catalytic activity of the catalyst was studied by thermal gravimetric analysis/differential scanning calorimetry at various heating rates. In addition, the effect of the catalyst on the AP thermal decomposition has been investigated by Kissinger and Friedman methods as two model-free methods for calculation of the activation energy parameter. According to the Kissinger method calculations, the E_a of AP decomposition reduced about 151 kJ⋅mol⁻¹ lower than the reported value for pure AP in the presence of the catalyst. Calculation of the E_a value for various reaction conversion rates by the Friedman method also confirmed the Kissinger method results.     

The catalytic effect of NiO on thermal decomposition of nitrocellulose

The catalytic effect of NiO on thermal decomposition of nitrocellulose (NC) has been investigated via thermogravimetry–mass spectrometry (TG–MS) coupling technique, and the residue of NC with 20% NiO reacted in tubular furnace was analyzed by X-ray diffraction (XRD). TG–MS analysis showed that adding 2% NiO to NC accelerated the thermal decomposition process and promoted the generation of gaseous products. The catalytic mechanism was based on the accelerated generation of NO₂, which further reacted with the radical to produce other gaseous products. XRD analysis of catalyst residue showed that Ni was formed during the catalytic reaction.     

Effect of gamma-irradiation on the catalytic activity and selectivity of gamma-alumina

Methanol conversion reaction was carried out in contact with a poorly crystalline -alumina pre-irradiated with different doses of -rays. The reaction was conducted at 140–440°C using a flow technique under atmospheric pressure. The results obtained revealed that -irradiation of Al₂O₃ resulted in drastic modifications of its activity and selectivity in methanol conversion reaction. The dose of 15 Mrad was sufficient to suppress completely the formation of dimethyl ether (DME) and stimulated the formation of methane, which started at 200°C instead of 300°C in the case of the unirradiated alumina specimen. However, the rate of CH₄ formation was found to decrease as a function of the dose employed. When the dose reached 140 Mrad, DME was reproduced with a rate comparable to that measured for the unirradiated catalyst sample. These results permitted us to conclude that DME is produced on the weak acidic sites (Brönsted acidity of Al₂O₃) and is not necessarily an intermediate compound for methane formation that takes place directly from methanol on strong acidic sites (Lewis acidity). The doses of 15–75 Mrad expelled completely the Brönsted acidic sites from Al₂O₃ surface, and the doses above this limit brought about a transformation of Lewis acidic sites into Brönsted acidity that is responsible for dimethyl ether formation. This transformation occurs by the action of liberated water from the dehydration of methyl alcohol.     

Influence of thermal and hydrothermal activation on the adsorptive, acidic and catalytic properties of high-silica zeolites

Influence of HS-zeolite calcination up to 1023 K in air and steam on its adsorptive, acidic and catalytic properties in n-hexane cracking has been studied.

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Basic properties of alkaline earth metal oxides and their catalytic activity in the decomposition of diacetone alcohol

The effect of CO₂ adsorption on the catalytic activity of alkaline earth metal oxides in the title reaction reveals that the number of active (basic) sites follows the order MgO>CaO>SrO>BaO, and the order of base strength is MgO

CO₂ , () : MgO>CaO>SrO>BaO, : MgO     

Effect of explosion on the catalytic activity and selectivity of natural fluorite

The effect of various types of shock waves on the catalytic activity of natural fluorite in isopropanol dehydrogenation and dehydration reactions has been studied. Shock treatment is shown to decrease the catalytic reaction temperature and to increase the selective

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Dehydrogenation of isopropyl alcohol on modified cobalt catalyst

The effects of plasmochemical processing and of Ce, K, and Hf additives on the rate of dehydrogenation for isopropyl alcohol on a 5 wt % Co/SiO₂ catalyst is studied under static and flow conditions. Glow discharge plasma in O₂ and Ar and high-frequency electrodeless plasma in H₂ (HF-H₂) are used. Except for one sample containing Hf, an increase in catalytic activity is observed due to the formation of new active centers. The change in the composition of the initial catalyst’s surface after treatment with Ce and with oxygen, argon, and HF-H₂ plasmas is determined by means of X-ray photoelectron spectroscopy. The change in the size and shape of Co particles after treating the catalyst with HF-H₂ plasma and Ce is determined via X-ray phase analysis. It is suggested that the new catalytic centers formed after treatment in O₂ and Ar plasma contain carbon atoms with C1s bond energies of 282.1 eV; after treatment with HF-H₂ plasma, active centers contain hydrogen and carbon atoms with C1s bond energies of 282.5 eV; with cerium, the C1s bond energy is 297.7 eV.     

Irradiation of terephthalophenone in isopropyl alcohol

Irradiation of terephthalophenone in isopropyl alcohol gave a bright yellow-colored intermediate which decayed rather rapidly. The products were complex and depended upon the mode of irradiation. They ranged from a mixed polymer I to a dimer II. I consisted of about 5 terephthalophenone units capped with hydrogen or isopropyl alcohol radicals or terminated by cyclization. II, the dimer, was capped by hydrogen atoms.     

The catalytic effects of metal oxides on thermal decomposition reactions,III

The catalytic activity of a series of iron oxides on the thermal decomposition of potassium chlorate was investigated by methods of thermal analysis. Structural and electronic defects were introduced into the oxide by doping, heat treatment in different atmospheres, and irradiation with-rays. These induced defects changed in a systematic way the conductive properties of the iron oxides and correspondingly, their catalytic activity. The results are consistent with ann-type semiconductive behavior of the oxides.

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Zusammenfassung Die katalytische Aktivität einer Reihe von Eisenoxiden gegenüber der thermischen Zersetzung von Kaliumchlorat wurde durch Methoden der Thermoanalyse untersucht. Strukturelle und elektronische Defekte wurden in das Oxid durch Dosierung, Wärmebehandlung in verschiedenen Atmosphären und Bestrahlung mit-Strahlen eingebaut. Diese induzierten Defekte änderten systematisch die Leitfähigkeitseigenschaften der Eisenoxide und dementsprechend ihre katalytische Aktivität. Die Ergebnisse stimmen mit dem Halbleiterverhalten desn-Typs der Oxide gut überein.

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This work was supported by the U.S. Army Edgewood Arsenal under Project No. DA-18-035-AMC-341(A). The authors are grateful to Mr. B. Zeffert and Mr. Harry A. Brown for valuable discussions and useful suggestions.

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The authors also wish to acknowledge Brent Boldt for the laboratory work which he conducted on this program.     

Thermal decomposition of ethyl and isopropyl amine perchlorates

Thermal decomposition of ethyl and isopropyl amine perchlorates has been studied by methods such as DTA, TG, isothermal weight loss measurements and the decomposition products have been analyzed in a mass spectrometer. Activation energy values for thermal decomposition have been calculated from-t plots. The proton transfer dissociation mechanism proposed for the thermal decomposition of ammonium perchlorate (AP) has been extended to explain the decomposition products of these twosubstituted amine perchlorates.

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Zusammenfassung Die thermische Zersetzung von Äthyl- und Isopropylaminperchloraten wurde durch die Methoden der DTA, TGA sowie durch isotherme Gewichtsverlustmessungen untersucht und die Zersetzungsprodukte in einem Massenspektrometer analysiert. Die Werte der Aktivierungsenergien der thermischen Zersetzung wurden aus-t Funktionen berechnet. Der für die thermische Zersetzung von Ammoniumperchlorat (AP) vorgeschlagene Proton-Übergangs-Dissoziationsmechanismus wurde erweitert um die Zersetzungsprodukte dieser zwei substituierten Aminperchlorate zu erklären.

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Résumé On a étudié, par des méthodes comme l'ATD, la TG et les mesures de pertes de poids isothermes, la décomposition thermique des perchlorates d'amines éthylique et isopropylique et on a analysé les produits de décomposition dans un spectromètre de masse. On a calculé les valeurs de l'énergie d'activation de la décomposition thermique à partir des fonctions-t. On a étendu le mécanisme de dissociation du transfert de protons, proposé pour la décomposition thermique du perchlorate d'ammonium (AP), afin d'expliquer la formation des produits de décomposition de ces deux perchlorates d'amines substitués.

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