In situ crystallization of bacterial cellulose II. Influences of different polymeric additives on the formation of celluloses Iα and Iβ at the early stage of incubation

Effects of polymeric additives with different degrees of polymerization (DP) or substitution (DS) on the crystallization of celluloses I and I have been examined at an early stage of the incubation of Acetobactor xylinum by using newly developed FT-IR spectroscopy. It was found that the mass fraction of cellulose I is greatly decreased with increasing concentrations of carboxymethyl cellulose sodium salt (CMC) or xyloglucan (XG) in the incubation medium. Such a decrease in the mass fraction of cellulose I, which corresponds to the enhanced crystallization of cellulose I, is more prominent for CMC or XG with lower DPs, but the additives with too low DPs are not so effective probably due to higher solubility and the lower adhesion on the surface of microfibrils. Moreover, the mass fractions of celluloses I and I are highly correlated with the crystallite size of microfibrils, indicating that I is crystallized in larger-size microfibrils while I is produced in smaller-size microfibrils. On the basis of these experimental results, the mechanism of the crystallization of celluloses I and I is discussed in the Acetobactor xylinum system.     

Kinetic analysis of thermogravimetric data. XI thermal decomposition of some metal dithionates

A thermal analytical study of Li, Na, K, Rb, Cs, NH₄, Mg, Ca, Sr, Ba and Zn dithionates is reported. The decomposition of the dithionate ion is endothermic in the case of the Na, K, Rb, Cs and NH₄ salts, but exothermic with Li, Mg, Sr, Ba and Zn. Kinetic parameters have been derived from the TG curves by means of the Coats-Redfern method. The validity of a linear kinetic compensation law is reported for the loss of crystal water and separately for the decomposition of the dithionate ion.

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Zusammenfassung Es wird über eine thermoanalytische Untersuchung der Dithionate von Li, Na, K, Rb, Cs, NH₄, Mg, Ca, Sr, Ba und Zn berichtet. Die Zersetzung des DithionatIons ist im Falle von Na, K, Rb, Cs und NH₄-Salzen endotherm, im Falle von Li, Mg, Sr, Ba und Zn hingegen exotherm. Die kinetischen Parameter wurden aus den TG-Kurven mittels der Coats-Redfern-Methode abgeleitet. Es wird über die Gültigkeit eines linearen kinetischen Kompensationsgesetzes für den Verlust von Kristallwasser berichtet und gesondert für die Zersetzung des Dithionat-Ions.

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Résumé On présente les résultats d'une étude par analyse thermique des dithionates de Li, Na, K, Rb, Cs, NH₄, Mg, Ca, Sr, Ba et Zn. La décomposition est endothermique dans le cas des sels de Na, K, Rb, Cs et ammonium tandis qu'elle est exothermique dans le cas des sels de Li, Mg, Sr, Ba et Zn. Les paramètres cinétiques sont déduits des courbes TG par la méthode de Coats-Redfern. La validité d'une loi de compensation cinétique linéaire est étudiée pour la perte de l'eau d'hydratation ainsi que pour la décomposition de l'ion dithionate.

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Li, Na, K, Rb, Cs,. NH₄, Mg, Ca, Sr, Ba Zn. [ Na, K, Rb, Cs NH₄ , Li, Mg, Sr, Ba Zn . - . .

     

Monolayer vanadia on titania systems from alkoxide precursors. Part III. Activity in secondary alcohol oxidation

The activity of V⁵⁺ ion monolayer supported on anatase, rutile, and anatase-rutile mixed carrier and of bulk V₂O₅ was examined in isopropyl alcohol and cyclohexanol oxidation. Catalysts exhibited remarkable activity in ketone formation. At higher temperatures benzene was the predominant product of cyclohexanol reaction.

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V⁵⁺, , - V₂O₅, . . .

     

Reduction of CuO-containing catalysts: CuO/Cox/ZnO

Cu²⁺ in CuO/ZnO reduces more extensively and rapidly than Co²⁺ in CoO_x/ZnO in the presence of CO or H₂. XRD, TPR and thermal analysis of the combined CuO–CoO_x/ZnO catalysts prepared by precipitation suggests that the component CuO and promoter CoO_x phases are in intimate contact. The addition of Co²⁺ to CuO/ZnO catalystsdecreases the reducibility of the Cu²⁺ by CO and this is relevant to Cu–Co catalysts for ethanol synthesis.

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Cu²⁺ CO H₂ CuO/ZnO, Co²⁺ CoO_x/ZnO. , CuO–CoO_x/ZnO, , CuO CoO_x. Co²⁺ CuO/ZnO Cu²⁺ CO Cu–Co .

     

Effect of carbon support on the hydrogen sorption of platinum

The hydrogen sorption of carbon-supported platinum catalysts, studied by the potentiodynamic method, differs significantly from that of unsupported platinum. The difference depends on the preparation method and on the nature of the support. Possible explanations are suggested as (i) some kind of interaction between metal and support atoms during impregnation, (ii) high dispersity (amorphous structure) and (iii) hydrogen spillover onto the carbon support.

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Pt/C, . . (I) , (II) ( ), (III) .

     

Activation of magnesia by hydrogen spillover

Magnesia aerogel activated by hydrogen spillover at 430 °C or at 200 °C becomes a catalyst for the hydrogenation of ethylene. This catalytic activity, observed already at 50 °C, is further enhanced by a treatment in oxygen at 430 °C.

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, 430 200°C, . 50°C 430°C.

     

Physico-chemical properties of silica-supported vanadium oxide catalysts

- . TiO₂ ZnO. - CO₂ H₂O. — .

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The effect of visible light on propane and n-butane oxidation has been sutied on a seires of metal oxides. TiO₂ and ZnO have been found to exert a photocatalytic effect. On TiO₂, propane and n-butane are oxidized to CO₂ and H₂O. On ZnO as catalyst, partial oxidation products, aldehydes and ketones, are formed.

     

Formation of N-butane in the pyrolysis of ethylene [1]

Yields of n-C₄H₁₀ have been measured from the flow pyrolysis of C₂H₄ at 897 (±7) K. From 77 to 720 Torr the order of n-C₄H₁₀ formation was found to be 2.0±0.3 The rate constant for the reaction, was estimated to be 2.4(±0.6)×10^–4l mol^–1s^–1.

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-C₄H₁₀ C₂H₄ 897 (±7) . -C₄H₁₀ 77 720 2.0±0.3. 2C₂H₄C₂H₃+C₂H₅ 2,4 (±0,6)×10^{–4 –1–1}.

     

Some remarks on the periodical change of the stability constants of the lanthanide complexes

The correlations between the values of the lgK (K = stability constant of the lanthanide complex) and the reciprocal of the ionic radius 1/r or the sum of the ionization potentials ₁ ³ I for the lanthanide ions were reviewed for different ligands. A straight-line relationship (lgK – lgK)/lgK vs. (1/r – 1/r)/(1/r) or vs. ( ₁ ³ I – ₁ ³ I)/ ₁ ³ I was found within the tetrads La-Nd, Gd-Ho, and Er-Lu.

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Bemerkungen zum periodischen Wechsel der Stabilitätskonstanten von Lanthaniden-Komplexen

Zusammenfassung Es wurde eine Übersicht der Korrelationen zwischen den Werten von logK (K = Stabilitätskonstante der Lanthanidenkomplexe) und den reziproken Ionenradien 1/r oder der Summe der Ionisierungspotentiale ₁ ³ I für die Lanthanidenionen für verschiedene Liganden gegeben. Dabei wurde eine lineare Korrelation für (lgK – lgK)/lgK gegen (1/r – 1/r)/(1/r) oder gegen ( ₁ ³ I – ₁ ³ I)/_1/3 I innerhalb der Tetraden La-Nd, Gd-Ho und Er-Lu aufgefunden.

     

Reaction of ammonium sulphate with aluminium oxide

The reaction between ammonium sulphate with aluminium oxide was studied. It was confirmed by X-ray diffraction and chemical analysis that three intermediate reaction products, (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ and Al₂(SO₄)₃, are formed. The thermal decompositions of these three compounds were carried out. It has been shown that the same rate law is valid for them. The activation energies for (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ and Al₂(SO₄)₃ are 95.9, 177.9 and 291.0 kj/mol, respectively.

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Zusammenfassung Die Reaktion von Ammoniumsulfat mit Aluminiumoxid wurde untersucht. Durch Röntgendiffraktion und chemische Analyse wurde bestätigt, daß drei Zwischenprodukte (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ und Al₂(SO₄)₃ gebildet werden. Die thermische Zersetzung der drei Verbindungen wurde durchgeführt. Es wurde gezeigt, daß für alle drei dasselbe Geschwindigkeitsgesetz Gültigkeit hat. Die Aktivierungsenergien für (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ und Al₂(SO₄)₃ sind 95.9, 177.9 und 291.0 kJ/Mol.

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. - : (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ Al₂(SO₄)₃. , , . (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ Al₂(SO₄)₃, , 95.9; 177.9 291.0 . ^–1.

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The authors are grateful to Dr. H. Osada and Mr. H. Nakamura, Department of Environmental Engineering, Kyushu Institute of Technology, for their helpful discussions.     

Thermal and some other properties of the complexes crystallizing from the system Ni(II)-en-[Ni(CN)4]2−-H2O

Seven complex compounds exhibiting the compositions Ni(en)₃Ni(CN)₄·H₂O (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄·2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2.5H₂O (VI) and-Ni(en)₂Ni(CN)₄ (VII) were prepared from the system Ni-en-[Ni(CN)₄]^2–-H₂O. These compounds were examined by the methods of infrared spectroscopy, X-ray powder diffractometry, UV-VIS reflectance spectroscopy, and also by the measurement of magnetic moments. The thermal stability, the stoichiometry of thermal decomposition and the mutual transformations were investigated with a derivatograph. The reactions proceeding according to the following schemes were observed if the system was heated to appropriate temperature: (I)(II)(III)(V)(IV) and (VI)(VII)(III)(V)(IV) Process (VII)(III) represents isomerization. The reversibility of the process (V)(IV) is due to the high hygroscopicity of the anhydrous complex. The changes in structure in the course of the individual processes are discussed.

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Zusammenfassung Aus einem System Ni-en-[Ni(CN)₄]^2–-H₂O wurden sieben Komplexe der Formeln Ni(en)₃Ni(CN)₄·H₂O (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄·2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2.5H₂O (VI) und-Ni(en)₂Ni(CN)₄ (VII) hergestellt. Diese Verbindungen wurden mittels IR-Spektroskopie, Röntgenpulverdiffraktometrie, UV-Reflexionsspektroskopie und durch Messungen des magnetischen Momentes untersucht. Die Wärmestabilität, die Stöchiometrie des thermischen Zerfalles und die gegenseitigen Umwandlungen wurden mittels eines Derivatographen untersucht. Wird das System auf geeignete Temperaturen erhitzt, kann der Reaktionsverlauf durch folgendes Schema dargestellt werden: (I)(II)(III)(V)(IV) und (VI)(VII)(III)(V)(IV).Der Prozeß (VII)(III) verkörpert eine Isomerisierung. Die Umkehrbarkeit von Prozeß (V)(IV) ist auf die ausgeprägten Hygroskopieeigenschaften des wasserfreien Komplexes zurückzuführen. Es werden die im Ablaufe der einzelnen Prozesse vorgehenden Strukturveränderungen besprochen.

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Ni- -[No(N)]² -₂ Ni(en)₃Ni(CN)₄ · ₂ (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄-2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2,5H₂O (VI) -Ni(en)₂Ni(CN)₄ (VII). , , - , . , . (I)(II)(III)(V)(IV) (VI)(VII)(III)(V)(IV). (VII)(III) . (V)(IV) . .

     

On the problem of predicting the activity of oxide and carbonate catalysts in some reactions of petrochemical synthesis

The problem of predicting the activity of oxide and carbonate catalysts for some reactions of petrochemical synthesis (vapor phase conversion of carboxylic acids, catalytic oxidation of asphaltic tar to bitumen) according to the established dependence of thermal stability variations of intermediates on the formation enthalpy of metal oxides or standard ele.trode potentials is discussed.

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, ( , ) .

     

In Situ crystallization of bacterial cellulose I. Influences of polymeric additives,stirring and temperature on the formation celluloses I α and I β as revealed by cross polarization/magic angle spinning (CP/MAS)13C NMR spectroscopy

To obtain further information about the formation of cellulose I and I, cross polarization/magic angle spinning (CP/MAS)¹³C NMR spectroscopy was used to study the effects of polymeric additives, stirring and culture temperature on the I When xyloglucan (XG) or carboxymethyl cellulose sodium salt (CMC) was added to the incubation medium, the amount of cellulose I decreased markedly, from a normal level of 64% to as low as 30%, with the most additive giving the lowest levels of I. Moreover, stirring causes mixtures containing even small amounts of XG to have a large effect. These results suggest that CMC or XG interferes with the aggregation of fibrillar units into the normal ribbon assemblies. It may be that there is a strain associated with this aggregation that results in the higher-energy I form. Thus, cellulose I may grow preferentially when the strain caused by aggregation is not present. Lower temperatures (36–10 °C) gave an increase in I (from 56 to 72%).     

Interaction of PM12?nVnO40?(3+n) (M=Mo, W) heteropoly complexes with nitrogen oxide

In aqueous solution, PM_12–nV_nO₄₀ ^–(3+n) (M=Mo,W) hetero-polyanions provide a much faster oxidation of NO than mononuclear VO ₂ ⁺ ions, yielding HNO₂, NO ₃ ^– and reduced HPA.

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, PM_12–nV_nO₄₀ ^–(3+n) (M=Mo,W) , VO ₂ ⁺ , NO HNO₂ NO ₃ ^– .

     

m-Xylene conversion over dealuminated Y zeolites studied by the pulse method

m-Xylene conversion was studied over dealuminated Y type zeolites in hydrogen forms, SiO₂ to Al₂O₃ ratios were varied from 4.86 to 12.95.

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- . SiO₂/Al₂O₃ 4,86 12,95.

     

Catalysts for selective hydrogenation of conjugated dienes into olefins in the presence of PdCl2 complexes

Complexes of PdCl₂ with amines or pyridine reduced by (iso-Bu)₂ AlH are shown to be catalytically active in the selective hydrogenation of conjugated dienes into olefins in aromatic media. The promoting effect of H₂O and O₂ has been established.

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PdCl₂ , (-Bu)₂ AlH, . H₂O O₂.

     

Influence of substituents on rate constants for recombination of tertiary peroxy radicals

A linear correlation between the logarithm of rate constant (2k_t) for recombination of tertiary peroxy radicals (ROO)^* and ^* constants of substituents R was found to be 1g 2k_t=lg 2k _t ^° . The calculated values are 1g 2k _t ^° =4.59±0.08 and ^*=5.56±0.35.

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I (2k_t) (ROO) R: 1g 2k_t=lg 2k _t ^° . , 1g 1g 2k _t ^° =4,59±0,08 =5,56±0,35

     

Heterogeneous reactions of solid nickel(II) complexes

The influence of different modes of preparation on the stoichiometry of thermal decomposition of isothiocyanatonickel(II) complexes with ammonia was studied. It was found that the complex Ni(NCS)₂(NH₃)₄ (I) prepared by heterogeneous reaction undergoes decomposition in two steps (–2 NH₃, –2 NH₃), while for complex II, of the same composition but prepared by homogeneous reaction from solution, the decomposition proceeds in three steps (–1 NH₃, –1 NH₃, –2NH₃). Electronic and infrared absorption spectra were used for the study of the spectral properties of the starting complex. It was found that the different stoichiometries of thermal decompositions of complexes I and II do not cause differences in the bonding strength of the ammonia molecules (chemical factor); this effect is rather brought about by physical factors such as different imperfections of the crystal lattice.

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Zusammenfassung Der Einfluß der Herstellung auf die Stöchiometrie der thermischen Zersetzung von Amin-Komplexen des Isothiocyanatonickels wurde studiert. Der Zerfall des Komplexes Ni(NCS)₂(NH₃)₄ (I), hergestellt durch heterogene Reaktion, verlief in zwei Etappen (–2 NH₃, –2 NH₃). Beim selben Komplex (II), hergestellt durch homogene Reaktion in Lösung, wurden jedoch drei Etappen beobachtet (–1 NH₃, –1 NH₃, –2 NH₃). Die Eigenschaften des Ausgangsproduktes wurden durch Elektronen- und IR-Spektroskopie untersucht. Das unterschiedliche thermische Verhalten ist nicht auf eine verschiedene Bindungsstärke der NH₃ Moleküle, sondern auf physikalische Ursachen, wie z. B. Unregelmässigkeiten im Kristallgitter zurückzuführen.

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Résumé On a étudié l'influence des diverses méthodes de préparation sur la stoechiométrie de la réaction de décomposition thermique des complexes de l'isothiocyanate de nickel(II) avec l'ammoniac. On a établi que le complexe Ni(SCN)₂(NH₃)₄, (I), préparé rar réaction hétérogène, subit une décomposition en deux étapes (–2NH₃, –2NH₃), tandis que le complexe (II), de même composition, mais préparé par réaction homogène, à partir de solutions, se décompose en trois étapes (–1NH₃,–1NH₃, –2NH₃). Les propriétés spectrales du complexe initial ont été étudiées par absorption électronique et infrarouge. On a trouvé que les différences de stoechiométrie des réactions de décomposition thermique des complexes (I) et (II) n'apportaient pas de différences entre les énergies de liaison des molécules d'ammoniac (facteur chimique). C'est plutôt à des facteurs physiques, comme les différentes imperfections du réseau cristallin, que cet effet serait dû.

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(II) . , Ni(NCS)₂(NH₃)₄ (I), , (–2NH₃,–2NH₃). , II , , (–1 NH₃,–1 NH₃ –2NH₃). . , I II ( ), , .

     

A new type of crucible for TG and DTA

New types of crucibles for thermogravimetry and differential thermal analysis are described for use with conventional equipment, enabling extremely rapid movement of the gaseous species through the sample and sample holder. Its use in studies of oxidation or decomposition reactions is illustrated by considering the oxidation of UO₂ and the decomposition of CaC₂O₄·H₂O.

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Zusammenfassung Neuartige Tiegel werden zur Thermogravimetrie und Differential-thermoanalyse vorgeschlagen, die in den üblichen Einrichtungen benützt werden können. Sie ermöglichen eine extrem schnelle Bewegung der gasförmigen Produkte durch die Probe und den Probenhalter. Ihr Gebrauch zur Untersuchung von Oxydations- und Zersetzungsreaktionen ist am Beispiel der Oxydation von UO₂ und der Zersetzung von CaC₂O₄·H₂O illustriert worden.

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Résumé On décrit un nouveau type de creuset pour la thermogravimétrie et pour l'analyse thermique différentielle, adaptable aux dispositifs usuels et permettant un passage extrêmement rapide des gaz à travers l'échantillon et le support d'échantillon. L'exemple de l'oxydation de UO₂ et de la décomposition de CaC₂O₄·H₂O illustre son application à l'étude des réactions d'oxydation ou de décomposition.

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. . O₂ CaC₂O₄H₂O.

     

Temperature programmed reduction and oxidation of Ir/Al2O3 catalysts

3 % Ir/Al₂O₃ catalysts have been studied by means of temperature programmed reduction and oxidation. With growing degree of metal oxidation (higher T_ox) reducibility of the catalysts at low temperatures decreases.

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3% Ir/Al₂O₃ . ( ) .