Characterization of the interaction of CO and H2 at the ZnO surface by adsorption microcalorimetry

CO and H₂ are both chemisorbed by ZnO but H₂ is more sensitive than CO to the surroundings of adsorption sites. When the two gases are coadsorbed, a strong interaction occurs, ascribed to the formation of a possible precursor in methanol synthesis.

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CO H₂ ZnO, H₂ , , CO. , , .

     

Active component of vanadium catalysts in oxidation of gases with low concentrations of SO2

EPR and NMR studies show that in oxidation of gases with low concentrations of SO₂ the molten active component of K/V and Cs/V catalysts becomes inhomogeneous and contains V⁵⁺ compounds having different activities.

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, SO₂ K/V Cs/V , V⁵⁺.

     

Decomposition of cumene hydroperoxide in the presence of metal 1,2-dithiolate complexes

Metal 1,2-dithiolate complexes were studied as catalysts for decomposition of cumene hydroperoxide. Reaction proceeds by a two-stage process and the first stage, corresponding to destruction of the metal complex, is influenced by the type of metal and substituents on the dithiolate ligand. On average, almost two sulfur atoms in each metal chelate are oxidized to SO₂ or SO₃, which decompose the main part of hydroperoxide.

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1,2- . : . SO₂ SO₃, .

     

ESR investigation of the adsorption of13CO on CoO?MgO catalysts

Adsorption of CO enriched with¹³C isotope was investigated on a CoO–MgO catalyst containing 3 at.% Co. It is argued that the ESR signal with g_1,2=2.0054±0.0005; g₃=2.0020±0.0005; A₁=33 0e^*; A₂=11 0e; A₃=63 0e, appearing in the course of adsorption may not be ascribed to CO ₂ ^– or CO ₃ ^– anion radicals but should be attributed to surface X–CO complexes of a carbonyl-like structure.

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CO, C¹³, CoO–MgO, 3 .%-a Co. , g _1,2 ¹ =2,0054±0,0005, g₃=2,0020±0,0005, A₁=33 , A₂=11 A₃=63 , , - CO ₂ ^– CO ₃ ^– , X–CO , .

     

The thermal decomposition of thaumasite from Mothae kimberlite pipe,Lesotho, Southern Africa

The endothermic decomposition of thaumasite from Mothae which has been investigated by DTA and TG shows a peak temperature of 138–203°, and reaction orders of 0.45–1.00, depending on the heating rate employed. The activation energy of the reaction was found to be about 19 kcal/mole; the enthalpy is 246 cal/g.The decomposition seems to be divided into one reaction withn=0.90, immediately followed by one withn=1.59. The first reaction is attributed to the loss of H₂O, the second one to the (partial) release of OH and CO₂.

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Zusammenfassung Die durch DTA und TG überprüfte endothermische Zersetzung von Thaumasit aus Mothae zeigt in Abhängigkeit der angewandten Aufheizgeschwindigkeiten Spitzentemperaturen zwischen 138 und 203° C, sowie Reaktionsordnungen von 0.45 bis 1.00. Die Aktivierungsenergie der Reaktion ergab sich zu 19 Kcal/Mol, die Enthalpie zu 246 cal/g.Die Zersetzung scheint in eine Reaktion vonn=0.90 und eine sofort darauffolgende vonn=1.59 geteilt zu sein. Die erste Reaktion wird dem Verlust von H₂O, die zweite der (teilweisen) Freisetzung von OH und CO₂ zugeschrieben.

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Résumé La décomposition endothermique de la thaumasite de Mothae a été étudiée par ATD et TG. Suivant la vitesse de chauffage utilisée la température au sommet du pic varie de 138 à 203° C et l'ordre de réaction de 0.45 à 1.00. On a trouvé que l'énergie d'activation s'élevait à 19 kcal, mol^–1 et l'enthalpie à 246 cal. g^–1.Il semble que la décomposition s'effectue suivant une réaction d'ordren=0.90, immédiatement suivie par une autre oùn=1.59. On attribue la première réaction à la perte d'eau et la seconde à la libération (partielle) d'hydroxyles OH et d'anhydride carbonique CO₂.

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, , 138–203° 0,45–1,00 . , 19 /, - 246 /. , n=0,90, n=1,59. , - OH CO₂.

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The material used for this study has been kindly supplied by Dr. P. H. Nixon, former chief geologist, Department of Mines, Maseru, Lesotho.     

IR spectroscopic studies of acetone adsorption on Sn/Mo oxide catalyst

The formation of coordinatively bound acetone and cleavage products (enolates and, apparently, C–C bond cleavage products) has been revealed on the Sn/Mo oxide catalyst.

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Sn/Mo (, , , C–C ).

     

The applicability of DTA and DSC techniques to the study of the kinetics of phase transition reactions

Differential thermal analysis and differential scanning calorimetry techniques have been used to study the kinetics of phase transitions. The aragonite/calcite transformation was chosen as test reaction.Marked discrepancies were observed between the DTA kinetic results and those obtained from isothermal kinetic measurements. This disagreement is associated with the difficulty of determining accurately the reaction rate of the process from a DTA curve.In contrast, in DSC measurements, where the reaction rate is given by the height of the peak from the base-line, it is possible to get a satisfactory fit of the data, and the kinetic results obtained with this technique are in good agreement with the isothermal ones.

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Zusammenfassung Die Differentialthermoanalyse und DSC wurden zur Untersuchung der Kinetik von Phasenübergängen eingesetzt. Die Umwandlung Aragonit/Calcit wurde als Testreaktion gewählt.Bedeutende Diskrepanzen wurden zwischen den kinetischen Ergebnissen der DTA und den durch isotherme kinetische Messungen erhaltenen Ergebnissen beobachtet. Diese Abweichungen sind damit verbunden, daß es schwierig ist, die Reaktionsgeschwindigkeit des Vorgangs aus einer DTA-Kurve genau zu ermitteln.Bei DSC-Messungen,wo die Reaktionsgeschwindigkeit durch die Höhe des Peaks von der Grundlinie gegeben ist, kann eine befriedigende Anpassung der Daten erhalten werden, und die durch diese Technik erhaltenen kinetischen Ergebnisse sind in guter Übereinstimmung mit den isothermen Ergebnissen.

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. /. , . -. , , , , , .

     

Interaction of super-finely dispersed Al powders with water

Interaction of super-finely dispersed Al powders (SFDP) with water is characterized by the presence of a considerable section on the kinetic curves, where the conversion rate is maximum and its degree is as high as =0.5–0.7. It is suggested that the essential factor accounting for the conversion kinetics and the phase composition of its products is the self-heating of Al particles.

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() , , () 0,5–0,7. , .

     

Mutual effect of benzene and maleic acid anhydride in their adsorption on V2O5?MoO3 catalysts

TPD studies have revealed that benzene and maleic anhydride are adsorbed on different active sites of the V₂O₅–MoO₃ catalyst.

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, - .

     

Reforming type Pt/Al2O3 catalyst prepared from [(CH3)3PtX]4 complexes by thermal decomposition

Pt/Al₂O₃ catalysts with good reforming activity were prepared from [(CH₃)₃PtX]₄ (X=Cl, Br, I) complexes and tested in pulse and continuous-flow reactors in n-hexane dehydrocyclization. It has been demonstrated that [(CH₃)₃PtX]₄ complexes are excellent precursors of supported platinum catalysts.

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Pt/Al₂O₃ [(CH₃)₃ PtX]₄ (X=Cl, Br, I) -. , [(CH₃)₃PtX]₄ .

     

Effect of specific and nonspecific interactions on deutero-protium exchange in solution

The effect of electrostatic type interactions on the deutero-protium heteroexchange of dihydrogen with solutions catalyzed by bases, with the decisive role of hydrogen bonds and particularly of the H-bonds having increased strength, is discussed.

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- .

     

A temperature programmed desorption study of H2 from supported nickel catalyst

The chemisorption of hydrogen on Ni/SiO₂ has been studied by measuring temperature programmed desorption on various samples under various experimental conditions. Two peaks are found, which can be related to a weakly and to a strongly bound species of chemisorbed hydrogen. Their analysis has been performed by a method which makes possible to determine whether a certain kinetic model can describe the entire desorption process or to assign a clear meaning to the corresponding kinetic parameters.

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Ni/SiO₂ - . . , , , , .

     

Differential thermal analysis of the phase transition of dicalcium orthosilicate Ca2SiO4 under a reducing atmosphere

The transformation of Ca₂SiO₄ was investigated with regard to the disintegration of the sinter in alumina manufacturing. DTA was applied to study the effect of the reducing atmosphere upon the course of the polymorphic transitions of Ca₂SiO₄, and particularly the self-disintegration process. Pure synthetic dicalcium orthosilicate and blends of pure components from the system CaO-Al₂O₃-SiO₂-Fe₂O₃ were compared with technological mixtures of limestone and fly ash. Data obtained from the DTA runs allowed the specification of technical parameter for both firing and cooling of the sinter.

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Zusammenfassung Die -Umwandlung in Ca₂SiO₄ wurde im Hinblick auf den Zerfall von Sinter in der Tonerdeproduktion untersucht. Mittels DTA wurde der Einfluß einer reduzierenden Atmosphäre auf den Verlauf der polymorphen Umwandlungen von Ca₂SiO₄ und insbesondere auf den Zerrieselungsprozeß verfolgt. Reines synthetisches Ca₂SiO₄ und Gemische reiner Komponenten des Systems CaO-Al₂O₃-SiO₂-Fe₂O₃ wurden mit technischen Mischungen aus Kalk und Flugasche verglichen. Die Ergebnisse von DTA-Versuchen erlauben die Spezifizierung der technischen Bedingungen für das Brennen und Abkühlen des Sinters.

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. , , . -l₂₃-SiO₂-F23 . .

     

Thermal stabilities of copolymers of styrene and acrylic acid and their salts

The thermal stabilities of copolymers of styrene and acrylic acid and their alkali metal salts have studied.The thermal stability properties T_i and T_s, and the kinetic parametersn, E, S andZ were determined and the results are discussed. It was found that the thermal stabilities of the investigated copolymers of styrene and acrylic acid are somewhat lower than that of polystyrene and decrease with increase of the quantity of acrylic acid introduced into the copolymers.The thermal stabilities of the sodium salts of these copolymers are somewhat higher than those of the initial copolymers, and are almost equal to that of polystyrene.The thermal stabilities of the investigated ionomers depend on the nature of the alkali metal introduced into the copolymer.

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Zusammenfassung Es wurde die thermische Stabilität von Kopolymeren aus Styrol und Acrylsäure bzw. Acrylsäurealkalimetallsalzen untersucht. Die Werte T_i und T_s für die thermische Stabilität sowie die kinetischen Parametern, E,S undZ wurden bestimmt und die Ergebnisse diskutiert. Man fand, daß die thermische Stabilität der untersuchten Kopolymere aus Styrol und Acrylsäure etwas niedriger ist als die von Polystyrol und daß sie mit einer Zunahme des Anteiles an Acrylsäure an den Kopolymeren absinkt. Die thermische Stabilität der Natriumsalze dieser Kopolymere erwies sich als etwas höher als die die ursprünglichen Kopolymere, erreicht aber nur die von Polystyrol. Die thermische Stabilität der untersuchten Ionomere hängt von der Art der in die Kopolymere eingebrachten Alkalimetalle ab.

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. T _i ,T _s , E, n, S Z. , , . , , . , .

     

Role of strongly bound vanadia in V2O5/Al2O3 catalysts for selective catalytic reduction of nitric oxide by ammonia

V₂O₅/Al₂O₃ catalysts prepared by impregnation and by ammonia treatment of impregnated samples were tested for activity in the NO–NH₃ reaction. The ammonia treated samples, with higher proportions of strongly bound vanadia, were found to be comparable in activity to the impregnated catalysts and equally sensitive to the presence of oxygen.

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V₂O₅/Al₂O₃, , NO–NH₃. .

     

The thermoanalytical determination of deactivation types of cation-exchanger catalyst's

The dependence of the thermal decomposition of a cation-exchanger catalyst on its deactivation type has been ascertained, and thermal analysis has been suggested as a diagnostic method for the determination of the condition of such a catalyst.

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Zusammenfassung Die Abhängigkeit der thermischen Zersetzung eines Kationaustauscher-Katalysators von seinem Inaktivierungstyp wurde bewiesen und die Thermoanalyse als diagnostische Methods für die Bestimmung des Zustandes eines solchen Katalysators vorgeschlagen.

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. , .

     

Nature of the active oxygen of Co3O4

The differentiation of surface oxygen forms of Co₃O₄ by energy, reactivity and centers of adsorption has been carried out.

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Co₃O₄ , .

     

Textural changes in alumina coked by toluene cracking in fluidized bed

The texture of an alumina coked at 873–923 K has been studied by specific area measurements and determination of pore size distributions. Two opposite textural changes have been observed: a strong plugging of the microporosity (r=18–30 Å) and an increase of the porous volume and surface area of the larger porosity (r=30–1000 Å).

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, 873–923 , . : (r=18–30 Å) (r=30–100 Å).

     

Acidity and oxidation activity of MoO3?UO3/SiO2 catalysts

The effect of UO₃ on the acidity of MoO₃–UO₃/SiO₂ catalysts has been studied by means of infrared spectroscopy of adsorbed pyridine. The surface acidity exhibited a maximum for the same U/(U+Mo) atomic ratio (=0.11) that yielded a maximum in total conversion for isobutene oxidation. The catalytic properties for oxidation are discussed in terms of the acidic properties of the samples.

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UO₃ MoO₃–UO₃/SiO₂ . U/(U+Mo)=0,11, . , .

     

Response studies of the mechanism of o-xylene oxidation over a vanadium-titanium oxide catalyst

A response method has been used to study the mechanism of o-xylene oxidation over a vanadium-titanium oxide catalyst. The products of partial and destructive oxidation are shown to be formed under the influence of molecular oxygen on the surface intermediates produced by the interaction between o-xylene and oxidized surface sites.

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- . , , - .