Acid hydrolysis of cellulose in a differential scanning calorimeter

Differential scanning calorimetry was applied to the decompositions of cellulose and D-glucose with several concentration of sulfuric acid. The heat of reaction for cellulose was slightly less than that for glucose. It suggests that the heat of hydrolysis of the (-1,4-glucosidic linkage is endothermic.The degree of reaction obtained by means of a commercial kinetic program was 1.1±0.1, which was independent of the acid concentration for both cellulose and glucose.The quantity of D-glucose produced by saccharification of cellulose was estimated using kinetic parameters obtained for cellulose and glucose, which were assumed to express the respective parameters for the successive first-order reactions cellulose to D-glucose, and glucose to decomposition products.

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Zusammenfassung Die Zersetzung von Cellulose und D-Glucose durch Schwefelsäure unterschiedlicher Konzentration wurde mittels DSC untersucht. Die Reaktionswärme ist bei Cellulose etwas geringer als bei Glucose, was zeigt, daß die Hydrolyse der-1,4-Glucosidbindung ein endothermer Vorgang ist. Der mittels eines kommerziellen kinetischen Programms erhaltene Reaktionsgrad beträgt 1.1±0.1 und erwies sich sowohl bei Cellulose als auch bei Glucose als unabhängig von der Säurekonzentration. Die durch Verzuckerung von Cellulose gebildete Menge an D-Glucose wurde unter Verwendung von für Cellulose und Glucose erhaltenen kinetischen Parametern bestimmt, für die angenommen wurde, daß sie die entsprechenden Parameter der Folgereaktionen erster Ordnung Cellulose D-Glucose und Glucose Zersetzungsprodukte darstellen.

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-. - , . , - -1,4- . , , 1.1±0.1 . -, , , , - .

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We express our sincere gratitutde to Dr. S. Tanaka for useful discussions.     

Influence of the number of active sites on kinetic characteristics

The possibility for a complicated dependence of the steady-state reaction rate on the total number of catalyst active sites is shown for nonlinear mechanisms.

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.

     

Methane synthesis from CO/H2O mixture on supported nickel catalysts, II. Surface species in CO?H2 and CO?D2O interaction by IR spectroscopy

The species resulting in CO, CO+H₂ or CO+D₂O adsorption on supported Ni catalysts were followed by IR spectroscopy and their role in methane synthesis mechanism is discussed.

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- , CO, CO+H₂ CO+D₂O . .

     

Chelated amines as ligands in olefin hydrogenation catalysts

Activities of catalysts obtained in the reaction of [MCl(C₈H₁₄)₂]₂, (M=Rh, Ir) with amines NH₂(CH₂)_nNH₂, (N=2–5), (CH₃)₂NC₂H₄(CH₃)₂ and 1.8=diaminonaphthalene have been examined. The most efficient catalyst was obtained with 1.3-diaminopropane.

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, [MCl(C₈H₁₄)₂]₂. (M=Rh, Ir) NH₂(CH₂)_nNH₂, (n=2–5). (CH₃)₂NC₂H₄(CH₃)₂ 1,8-. , 1,3-.

     

Influence of oxygen compound structural elements of stretching vibration frequency of surface hydroxy groups

Stretching vibration frequencies of OH groups ( OH) in acidic oxygen compounds are determined by the electrostatic characteristics (E_p) of the polyhedron containing this group. Empirical dependence of OH various hydroxy groups on the number and nature of their binding cations is suggested.

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, OH- ( OH) (). .

     

DSC characterization of ZSM-5/MgO/Al2O3 catalysts

The physico-chemical characterization of magnesium-modified ZSM-5 zeolite catalysts has been performed by differential scanning calorimetry. Evidence has been found of the formation of magnesium oxide and the magnesium spinel phase in alumina-bonded ZSM-5 catalysts. DSC proved a suitable technique for characterization of these systems.

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Zusammenfassung Mg-modifizierte ZSM-5-Zeolithkatalysatoren wurden durch DSC charakterisiert. Es wurden Beweise für die Bildung von Magnesiumoxid und Magnesiumspinell in ZSM-5/Aluminiumoxid-Katalysatoren gefunden. DSC hat sich zur Characterisierung dieser Systeme als geeignet erwiesen.

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- 3CM-5, . - - . .

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This work was carried out within the Progetto finalizzato Energetica 2 of the National Research Council of Italy.     

Reactions of C4?C6 alkanes on platinum and platium-gold films

Results are reported on the reactions of n-butane, n-pentane and n-hexane on Pt and Pt/Au alloy films. The results are compared with those obtained for Pt–Au alloys on a SiO₂ carrier. It is concluded that alloying can change the selectivity of the catalyst. No indication has been found for the possible role of oxygen in the high selectivity of Pt in non-destructive reactions.

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-, - - Pt . , Pt–Au SiO₂. , . - Pt .

     

Reaction kinetics by thermal analysis

The application of thermal analysis in the study of reaction kinetics and reaction mechanisms in combination with presently available powerful analytical tools, in the sphere of materials with particular reference to high energy materials is presented and discussed. Also an attempt has been made to correlate the kinetic data obtained by TA with the performance characteristics, for some important materials.

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Zusammenfassung Es wird die Anwendung der Thermoanalyse bei der Untersuchung der Reaktionskinetik und des Reaktionsmechanismus in Zusammenwirkung mit den gegenwärtig zur Verfügung stehenden leistungsfähigen analytischen Werkzeugen auf dem Gebiet von Materialien mit speziellem Bezug auf energiereiche Stoffe dargestellt Und besprochen. Es wurde auch versucht, die durch TA erhaltenen kinetischen Daten einiger wichtiger Stoffe mit deren Leistungskenndaten in Beziehung zu stellen.

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. , , .

     

Stochastic models of diffusion controlled reactions. Random walk on cubic lattice

Random walk on cubic lattice with annihilating interactions is shown to be an appropriate model of diffusion controlled reactions and diffusion in condensed phase. For homogeneous concentration the rate constantk is proportional to the parameter of random walk.

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, . k .

     

Electron microscopic studies of platinum catalysts prepared via decomposition of Al2O3-anchored metal complexes

Reduced alumoplatinum and alumoplatinum-tin catalysts prepared via interaction of an organometallic platinum complex and platinum-tin compounds of various composition with Al₂O₃ mainly contain platinum particles of 10 Å.

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, Al₂O₃, , , 10 Å.

     

Effect of Ga on catalytic behavior of Pt catalyst

Platinum-gallium/alumina supported catalysts have been studied. With gallium loadings increasing, the catalysts show very different catalytic performance in n-hexane conversion due to gallium effect on the bifunctionality.

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-, . -, .

     

Comparison of dynamic mechanical and dielectric thermal analysis on cure studies for composites

Dielectric measurements covering a wide frequency range provide one of the few practical methods for monitoring the cure of thermosets (epoxy, etc.) using relatively non-intrusive sensors. The measurements form the basis of a manufacturing control cycle, in the autoclave, provided the rheological state of the thermoset can be related to the dielectric constant (¹) and loss factor (tan). The present paper concerns further investigations in our laboratory of the correlation between mechanical and dielectric behaviour during cure (1).

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Zusammenfassung Dielektrische Messungen über einem weiten Frequenzbereich stellen die eine Methode dar, um unter Anwendung verhältnismässig nicht-intrusiver Fühler die Aushärtung von Duroplasten /Epoxid usw./ verfolgen zu können. Die Messungen bilden die Grundlage für einen Pertigungsüberwachungskreis des Autoklaven, da der rheologische Zustand des Duroplast mit der Dielektrizitätskonstanten // und dem dielektrischen Verlustfaktor /tan/ in Verbindung gebracht werden kann. Vorliegende Arbeit berichtet über weitere Untersuchungen unseres Laboratoriums über den Zusammenhang zwischen mechanischem und dielektrischen Verhaltens während der Aushärtung.

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120–230°. 2 3590 . . . 150°, . .

     

Effect of mechanical activation on the catalytic, physical and chemical properties of copper oxide

Mechano-chemical activation of copper oxide powders leads to structural disordering of the near-surface layers of particles and, thus, to considerable variations in the catalytic properties of copper oxide.

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, , .

     

Role of tin in a PtSb alloy and a Pt-Sn/Al2O3 reforming catalyst

The conversion of n-hexane was studied on a Pt-Sn/Al₂O₃ catalyst, a PtSn alloy and on the corresponding Pt catalysts. The results indicate the same catalytic effect of tin in supported and unsupported catalysts. It is concluded that the role of tin is connected with alloy formation.

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- Pt-Sn/Al₂O₃, PtSn Pt-. . , .

     

Surface redox properties of Rh/AlPO4 and Rh/AlPO4?SiO2 catalysts

Electron donor and acceptor properties of AlPO₄ and AlPO₄–SiO₂ (2080 wt. %) supported rhodium catalysts have been studied. It was observed that the effect of metal deposition on both electron acceptor and donor properties depend on the support and precipitation agent. AlPO₄ supported rhodium showed better acoeptor than donor properties, while for Rh/AlPO₄–SiO₂, the acceptor properties were superior. However, the effect of metal on the redox properties is slight.

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AlPO₄ QlPO₄ SiO₂ (2080 .%). ]ye . AlPO₄ , , Rh/AlPO₄–SiO₂ . , - .

     

Cracking of cumene on vanadium doped silica-alumina

The influence of small admixtures of vanadium on the activity of a silica-alumina catalyst in cumene cracking has been investigated. A correlation has been established between the catalytic and acidic properties of the vanadium doped catalyst.

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Mathematical model for the thermal oxidation of coal in pseudo-fluidized catalyst bed

A mathematical model for the thermal oxidation of coal in a pseudo-fluidized catalyst bed is suggested. A three-phase system: catalyst, gas and coal, is considered. The boundary conditions for the pulse operation of the reactor are discussed.

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. : , , . , .

     

On the sub-Tg annealing of uniaxially oriented and unoriented atactic polystyrene

DSC analysis was performed on uniaxially oriented and unoriented atactic polystyrene samples prior to and after annealing at 80 °C. With increasing annealing times, an endothermic peak appeared, whose area increased with the duration of the annealing period. No difference was found between the endotherm areas for the oriented and the unoriented polymer.The DSC curve of the unannealed oriented polystyrene exhibited a relaxation exotherm. DSC and relaxation studies indicated that this relaxation exotherm was independent of the main chain orientation; it may rather be due to sample densification.

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Zusammenfassung Uniaxial orientierte und unorientierte ataktische Polystyrenproben wurden vor und nach dem Tempern bei 80° mittels DSC untersucht. Mit länger werdender Temperungszeit erscheint in endothermer Peak, dessen Fläche mit der Dauer der Temperungsperiode ansteigt. Die Flächen der endothermen Peaks von orientierten und unorientierten Polymeren unterscheiden sich nicht. Die DSC-Kurve von ungetempertem orientiertem Polystyren zeigt einen exothermen Relaxationseffekt. DSC und Relaxationsuntersuchungen ergaben, daß dieser exotherme Relaxationseffekt unabhängig von der Orientierung der Hauptkette ist und eher einer Probeverdichtung zuzuschreiben ist.

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80°. , . . , , . , , .

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We are grateful to Prof. B. Wunderlich of the Rensselaer Polytechnic Institute, New York, for useful discussions.

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The financial support of C.N.R. (progetto finalizzato chimica fine e secondaria) is gratefully acknowledged.     

Catalytic and surface properties of natural mordenite and chabazite from the Democratic People''s Republic of Korea

Natural mordenite and chabazite from the D.P.R. Korea were converted into their H⁺-forms by ion exchange and then characterized by the determination of their proton donor properties as well as by their reactivity in ethylene oligomerization The sample of natural mordenite in H⁺-form exhibits an activity which may be compared to that of synthetic H⁺-mordenite. The investigated natural chabazite in H⁺-form does not catalyze the oligomerization of C₂H₄, probably for steric reasons.

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- H⁺ , C₂H₄. H⁺ , , H⁺ C₂H₄, .