Changes in the surface characteristics of residues from the thermal decomposition of nickel oxysalts

The changes in surface area and density which occur during the decomposition of eight nickel oxysalts have been reported. Surface area peaks were observed in the temperature range 473 K to 673 K. An equation relating to the number of product particles (n) produced from a single particle of original material has been derived. Logn was shown to vary linearly with temperature, wheren is the number of product particles formed from one original reactant particle.

---

Zusammenfassung Es wird über die Veränderungen der Oberfläche und Dichte berichtet, welche bei der Zersetzung von acht Nickeloxysalzen auftreten. Oberflächenpeaks wurden im Temperaturbereich von 473 K bis 673 K beobachtet. Eine Gleichung wurde abgeleitet, welche sich auf die Zahl (n) der sich aus einem einzigen Partikel der Ausgangssubstanz bildenden Produktpartikel bezieht. Es wurde bewiesen, daß sich logn linear zur Temperatur ändert, wobein die Zahl der sich aus einem reagierenden Ausgangspartikel bildenden Produktpartikel ist.

---

Résumé Etude des changements de surface spécifique et de densité pendant la décomposition de huits oxysels du nickel entre 473 K à 673 K. En désignant parn le nombre de particules issues d'une particule unique du matériau initial, on montre que logn varie linéairement avec la température.

---

8 - , . , , 473–673 . , (), . logn .

     

Influence of the gas phase on metallic reference electrodes used in work function measurements

Contact potential differences between electrodes of Pt, Au and Ta of different surface finishing were measured by the dynamic condenser method in propylene and oxygen. Propylene is irreversibly adsorbed, thus changing the work function. This renders the electrodes unsuitable as standard electrodes for work function measurements on catalysts in the atmosphere of hydrocarbons, but they may be used in adsorption studies on oxygen.

---

Pt, Au Ta . , , . , .

     

Influence of water vapor on propylene oxidation on VMo catalyst

The dependence of reaction rates for acetone and acetic acid formation on the concentration of water vapor is determined on the basis of the participation of surface hydroxy groups and Brönsted acid centers of the catalyst.

---

.

     

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.

---

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.

---

. , , . -l₂₃-SiO₂-F23 . .

     

Thermal behaviour of trimethoxy silane modified alkyl methacrylates

The paper deals with the thermal behaviour of trimethoxy silane (MTS) modified ethyl methacrylate (EMA) and butyl methacrylate (BMA). Several copolymer samples were prepared by varying the molar ratio of MTS with respect to EMA or BMA. The copolymerisation was carried out at 78 °C for 120 min using benzoyl peroxide as an initiator. Incorporation of MTS in alkyl methacrylates resulted in an increase in thermal stability. Hydrolytic cross-linking of copolymer having higher mole fraction of MTS gave a cross-linked product with better thermal stability.

---

Zusammenfassung Vorliegende Arbeit beschäftigt sich mit dem thermischen Verhalten von Äthylmethakrylat (EMA) und Bulhylmethakrylat (BMA), das mit Trimethoxysilan (MTS) modifiziert wurde. Unter Anwendung verschiedener Molverhältnisse von MTS und EMA bzw. BMA wurden einige Kopolymerproben hergestellt. Die Kopolymerisation wurde 120 Minuten lang bei 78 °C und mit Benzoylperpxid als Initiator durchgeführt. Der Einbau von MTS in Alkylmethakrylate führt zu einer Steigerung der thermischen Stabilität. Eine hydrolytische Vernetzung der Kopolymere mit größeren Molanteilen an MTS ergeben vernetzte Produkte mit verbesserter thermischer Stabilität.

---

() ( ), (). . 78 °C 120 , . . , , .

     

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.

---

.

     

Quantitative thermal analysis,I Mathematical problems of quantitative differential thermal analysis

A highly simplified method for calculating heat of phase transitions from DTA data is presented. Two DTA curves are needed to calculate the heat of transition and the specific heat of the sample: one is for the original sample and one is for a sample prepared by mixing the original sample with some unreactive diluent the specific heat of which is known. The data of the DTA curves used in the calculations are the peak area, the rate of heating and the deviation of the DTA curve from the base line.

---

Zusammenfassung Eine einfache Methode zur Errechnung der Werte der Phasenübergangswärme aus den DTA Daten wird besprochen. Die Kenntnis der spezifischen Wärme der betreffenden Substanz und zwei Thermogramme sind hierzu nötig, jenes der Originalprobe und jenes einer Mischung der zu prüfenden Substanz mit einem indifferenten Stoff von bekannter spezifischer Wärme. Die notwendigen DTA Daten sind die Spitzenflächen, die Erhitzungsgeschwindigkeit und die Abweichung der DTA Kurve von der Nullinie.

---

Résumé On décrit une méthode simple pour caIculer les chaleurs des transitions de phase à l'aide des données d'analyse thermique différentielle. Il est nécessaire de connaître la chaleur spécifique et les thermogrammes de l'échantillon pur et en mélange avec une substance indifférente, de chaleur spécific connue. Pour les calculs, on se sert des données suivantes: surface des pics d'A. T. D., vitesse de chauffage et déviation de la courbe d'A. T. D. par rapport à la ligne de base.

---

(). () , . : , () .

     

Dissociative adsorption of propene on chromium molybdate

TPD studies of the interaction of propene with oxidized chromium molybdate have revealed that propene is reversibly chemisorbed on the Cr(MoO₄)₃ surface. The kinetic order of propene desorption is close to 2, which indicates a dissociative character of adsorption. It permits to suggest the presence of a -allyl complex of propene on the surface.

---

. , . , . - .

     

Cerium(III) ion catalysis in the oxalic acid-bromate reaction: Anomalous kinetic behavior of oxalic acid

The kinetics of cerium(III) ion catalyzed Br(V) oxidation of oxalic acid in the presence of HClO₄/H₂SO₄ and mercury(II)-a bromide removing ion, exhibits second order each in [br(V)] and [acid], 0.4 and zero order in [Ce(III)]. However, the kinetic behavior of oxalic acid is anomalous with –0.7, zero and 1.4 order. The chemistry underlying the phenomena is discussed.

---

Br(V), Ce(III), HClO₄/H₂SO₄ (II), , [Br(V)], [], 0,4 [Ce(III)]. , , .. –0,7, 0 1,4. , .

     

Character of hydrocarbon activation and catalytic activity of solid catalysts in deep oxidation reactions

In terms of a single conception, the relative reactivity of hydrocarbons and the activity of solid catalysts in reactions of deep oxidation are interpreted for the IT_i type mechanism. It is shown that for the oxidation of saturated hydrocarbons the most important is the acceptor interaction of hydrocarbons with catalysts, whereas for the oxidation of unsaturated compounds, of significance are both the donor and acceptor interactions.

---

. , , , .

     

Toluene disproportionation over decationized and aluminium deficient zeolites

The activities of aluminium deficient HL, HY, HX, H-mordenite zeolites are predominantly higher in comparison with those of normal H-zeolites. The increase in acid strength with dealumination of these zeolites enhances the catalytic activity.

---

- HL, HY, HX, , -. .

     

Reactions of isoflavone and 2-hydroxyisoflavanone with sodium ethoxide in anhydrous ethanol

Recent observation /1,4/ on the existence and unreactivity of IV under basic conditions, as well as its part in the inhibitory effect on the decomposition into deoxybenzoin is unequivocally proved by comparing the decompositions of I and VI. It is also shown that the decomposition of I is detemined neither by the character of the solvent nor by the nucleophilic character of the reactant, but by the possibility of the formation of IV.

---

IV , I VI. , I . , , IV.

     

Catalytic properties of silica-molybdenum catalysts in propylene oxidation

The activity of silica-molybdenum catalyts in propylene oxidation is shown to be determined by the partially dehydrated silica-molybdenum heteropolyacid stabilized by the SiO₂ surface.

---

, , SiO₂.

     

The possible formation of surface ethylidyne on platinum black and its effect on some catalytic properties

Secondary Ion Mass Spectra of Pt-black exposed to ethylene at 633 K contain a PtC₂H₃ cluster identified tentatively with adsorbed ethylidyne like that reported for single crystal surfaces. The catalytic properties of Pt pretreated by ethylene are, to some respect, superior in hydrocarbon transformations to those containing other, less defined carbonaceous overlayers.

---

- Pt-, 633 , PtC₂H₃, , . Pt, , , , , .

     

Catalytic properties of Hf?Eu oxide fine crystalline powders. Isomerization of n-butenes

Catalytic properties of a series of HfO₂–Eu₂O₃ fine crystalline powders were examined by the isomerization of n-butenes. HfO₂ pretreated at 873 K showed a high activity. It decreased with the addition of the Eu component. The product distributions are discussed on the basis of the acid-base properties.

---

HfO₂–Eu₂O₃ -. HfO₂, 873 K, . Eu. - .

     

Influence of changes in fine structure on thermal properties of cotton fibres

Examinations of the structural changes of mercerized cottons in sodium hydroxide or liquid ammonia were followed by determination of the degree of polymerization, sorption ratio and X-ray percentage crystallinity. Comparisons were made of the thermal stability, as indicated by differential thermal analysis and thermogravimetric analysis of the mercerized cottons. A decrease in the percentage crystallinity was found to lower then onset and peak temperatures of the major decomposition reaction. It was also found that the temperature where the major weight loss began increased in the sequence: cellulose III, cellulose II, and cellulose I. Samples in cellulose III crystals form were less thermally stable than samples of cellulose I and cellulose II. It will be noted however that the difference between cellulose II and cellulose III was small. Cotton cellulose II gave a lower yield of levoglucosan than either cotton cellulose I or II.

---

Zusammenfassung Strukturelle Veränderungen von merzerisierter Baumwolle in Natriumhydroxid oder flüssigem Ammoniak wurden durch Bestimmung des Polymerisationsgrades, des Sorptionsverhältnisses und der röntgen-Kristallinität verfolgt. Die differentialthermoanalytisch und thermogravimetrisch bestimmte thermische Stabilität der merzerisierten Baumwollen wird verglichen. Eine Verminderung der Kristallinität hat eine Abnahme der Temperaturen zur Folge, bei der die Hauptzersetzungsreaktion einsetzt bzw. mit maximaler Geschwindigkeit verläuft. Es wurde ebenfalls festgestellt, daß die Temperatur, bei der der Hauptgewichtsverlust einsetzt, in der Reihenfolge Cellulose III-Cellulose II-Cellulose I ansteigt. Proben in der Kristallform Cellulose III sind thermisch weniger stabil als die in der Celluloseform I und II. Baumwollcellulose II ergab geringere Ausbeuten an Levoglucosan als Baumwollcellulose I oder III.

---

, , , , . . , . , : III, II I. , III , I II. II , 1 III.

     

Catalytic properties of rare earth manganites and related compounds

Perovskite-type oxides REMnO₃ (RE=La-Dy) and PrMn_1–xNi_xO₃ (x=0–0.8) have been prepared. The catalytic activity and the reducibility of these oxides were investigated. The effect of RE, Ni ions on catalytic property, and the relation between catalytic activity and reducibility are discussed.

---

, , REMnO₃ (RE=La, Pr, Nd, Sm, Eu, Gd, Dy) PrMn_1–xNi_xO₃ (x=00,8). . RE Ni , .

---

---

Project Supported by the Science Fund of the Chinese Academy of Sciences     

Thermal behaviour of mixed tetravalent metal salts

In contrast with the well-known zirconium and titanium phosphates, products containing these metal ions together are unknown. To investigate the thermal behaviour of such materials, samples were synthetized with various ratios of the two metal ions. The samples were identified by means of X-ray diffraction. Their thermal behaviour was investigated in the temperature interval 25–1000 °C via simultaneous TG, DTG and DTA measurements. The data obtained are presented in this paper.

---

Zusammenfassung Im Gegensatz zu den wohlbekannten Zirkonium- und Titanphosphaten sind beide Metallionen gleichzeitig enthaltende Produkte unbekannt. Zur Untersuchung solcher Substanzen wurden Proben mit unterschiedlichen Mengen der beiden Metallionen gefertigt und mittels Röntgendiffraktion identifiziert. Die Proben wurden im Temperaturbereich 25–1000 °C mittels simultaner TG-, DTG- und DTA-Messungen untersucht. Die Ergebnisse werden in dieser Arbeit mitgeteilt.

---

, . . - , , 25–1000°. .

     

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.

---

, . k .

     

Kinetics of the oxidation of some polycyclic aromatic hydrocarbons by lead tetraacetate in aqueous acetic acid and perchloric acid medium

The state of metal cations in CuCr₂O₄/-Al₂O₃ catalysts under its operation in catalytic heat generators has been examined. IR spectra of adsorbed CO indicate copper ion reduction in the catalyst to Cu⁺, whose surface concentration was determined. Diffuse reflectance spectra have revealed that the initial catalyst contains Cr(VI), disappearing after reaction.

---

CuCr₂O₄/-Al₂O₃ (). - CO , Cu⁺. Cu⁺. , Cr(VI), .