Testing of nickel phosphate (NiP) catalyst for ethylbenzene oxydehydrogenation by means of isopropanol dehydration

It has been shown that NiP catalyst, if fresh, contains a high concentration of the same type acid-base surface centers as those participating in i-PrOH dehydration on -Al₂O₃. The concentration of these centers diminishes rapidly after a modification of NiP surface in a stream of ethylbenzene (EtPh) oxydehydrogenation products.

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, NiP - , , i-PrOH -Al₂O₃. NiP .

     

Solvent effects in the photolysis of 1,2,3,4-tetrahydro-1-naphthylhydroperoxide. Photocatalytic effect of Co(III) 2,4-pentanedionate

The effect of various solvents on the photoinitiated decomposition of 1,2,3,4-tetrahydro-1-naphthylhydroperoxide (THP) with and without added Co(III) 2,4-pentanedionate has been studied. The conversion of THP, formation of major products and change in the oxidation state of the metal ion have been investigated in different solvents.

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1, 2, 3, 4--1- () Co(III) 2,4-. , .

     

Liquid-phase hydrogenation on new AlPO4?SiO2 supported rhodium catalysts

The liquid-phase catalytic hydrogenation of various organic compounds was carried out using new rhodium catalysts supported on AlPO₄–SiO₂ (2080 wt. %) system, in methanol as solvent, under low hydrogen pressure (0.55 MPa) and at 293 K. Neither alkene isomerization nor hydrogenolysis products were detected in any of the cases.

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AlPO₄–SiO₂ (2080 . %), , , (0,55 MPa) 293 . , .

     

Properties of template-free synthetic (B, Al) pentasil type zeolites

Template-free synthetic, boron-containing pentasil type zeolites exhibit structural and catalytic properties similar to those of SABO zeolites made in the presence of n-propylamine.

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, , , SABO, -.

     

Sticking probability for oxygen adsorption and readsorption on thin iron films

Sticking probability for oxygen adsorption on thin iron films and readsorption on surface sites liberated due to incorporation of the adsorbate adatoms below the surface during thermal treatment has been studied by means of the Wagener flow method. Sticking probability for oxygen adsorption on oxidized thin iron films has also been measured for comparison.

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, . .

     

Correlation between apparent activation energy and selectivity in the oxidation of benzene over vanadia-molybdena catalysts

The existence of a linear correlation between the apparent activation energy of catalytic benzene oxidation and selectivity with respect to maleic anhydride was found in a series of unsupported vanadia-molybdena catalysts. A plausible explanation for such a correlation is given.

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- . .

     

Conversion of toluene on NiNaY and CeNaY zeolites

Ce–Y and Ni–Y zeolites were studied in the toluen conversion reaction before and after poisoning the acid centers by Na⁺ ions. It has been found that both Ce–Y and Ni–Y zeolites were active in the disproportionation of toluene at elevated pressures, which occur on strong Brönsted acid centers. The poisoning of the acid centers in Ni–Y zeolite led to the appearance of the activity of metallic Ni and complete change in the selectivity.

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Ce- Ni- Na⁺. , , . Ni- .

     

New method for determination of the equilibrium state in systems involving reactions of the type A(s)=B(s)+C(g)

A static method is described for measurement of the equilibrium values of temperature, pressure and composition of the solid phase, and determination of the number of degrees of freedom in heterogeneous systems containing a gaseous phase, including water vapour. With this method, it has been found that in the system formed in the thermal dehydration of CaC₂O₄·H₂O a solid solution of monohydrate and anhydride coexists in equilibrium with water vapour. The composition of the solid solution changes with the temperature and the pressure of water vapour. The dehydration enthalpy of the solid solution referred to 1 mol H₂O does not depend on its composition. It was found to be H _deh=(69+-3) kJ·mol^–1.

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Zusammenfassung Eine isotherme Methode zur Messung von Temperatur, Druck und Zusammensetzung der festen Phase im Gleichgewicht und zur Bestimmung der Anzahl der Freiheitsgrade in heterogen Systemen mit einer Gasphase (z.B. Wasserdampf) wird beschrieben. Mit dieser Methode wurde nachgewiesen, dass bei der thermischen Entwässerung von CaC₂O₄·H₂O eine feste Lösung von Monohydrat und Anhydrid im Gleichgewicht mit Wasserdampf existiert. Die Zusammensetzung dieser festen Lösung ändert sich mit der Temperatur und dem Wasserdampfdruck, ihre Dehydratationsenthalpie (pro 1 mol Wasser) hängt nicht von der Zusammensetzung ab und wurde zu H _deh=(69±3) kJ mol^–1 bestimmt.

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, , , , . , , ₂₄·₂ . . , 1 , H .=69±3 .^–1.

     

The thermal behaviour of some clathrates based upon Dianin's Compound

Clathrates based upon Dianin's Compound (4-p-hydroxyphenyl-2,2,4-trimethylchroman) exhibit shape and size selectivity towards included guest molecules in a manner similar to that shown by some commercially important zeolites. Clathrates derived from Dianin's Compound and a wide range of guest solvents were heated to their melting points and beyond, and their behaviour observed.

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Zusammenfassung Auf Dianin's Verbindung (4-p-Hydroxyphenyl-2,2,4-trimethylchroman) basierende Klathrate weisen gegenüber eingeschlossenen Gastmolekülen eine ähnliche Form- und Grössenselektivität auf wie einige wichtige kommerzielle Zeolithe. Von Dianin's Verbindung und einer Reihe von Lösungsmitteln erhaltene Klathrate wurden bis zum Schmelzpunkt und darüber hinaus erhitzt und dabei ihr Verhalten beobachtet.

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—4-- -2,2,4- — , , . , , , .

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The assistance of Mr Carl Garland and Miss Marianne McCusker in the early stages and Miss Cathy Kennedy in the later stages of this work is acknowledged with thanks. Instruction in the use of the Thermal Analyser and interpretation of several of the calorimetric analyses were generously provided by Dr Geoff Irvine.     

Infrared study of the interaction of nitric oxide with CuY zeolites

Infrared studies of the interaction of NO with CuY–A zelites have been made over the temperature range from –100°C to 400°C. Several forms of NO adsorption have been found, in particular, a stable cis-dimer at low temperatures.

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- (–100+400°C) NO CuY–A . NO, ë - .

     

Study of the thermal decomposition processes of clathrate compounds

The decompositions of the clathrate compounds [M(NCS)₂(4-MePy)₄]·nG (whereM=Mn, Co, Ni or Cd;G=4-methylpyridine (4-MePy), benzene or xylenes) were studied on a Q-derivatograph under quasi-equilibrium conditions and with linear heating. These clathrates can be divided into two groups, in which the loss of guest is either (I) accompanied by destruction of the host complex, or (II) occurs before decomposition of the host complex. Kinetic parameters were obtained.

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Zusammenfassung Die Zersetzung von Clathrat-Verbindungen der Zusammensetzung [M(NCS)₂(4-MePy)₄]·nG (M=Mn, Co, Ni, Cd;G=4-Methylpyridin (4-MePy), Benzen, o-,m, p-Xylen) wurde mittels Q-Derivatograph unter Quasi-Gleichgewichtsbedingungen und bei linearer Aufheizung untersucht.Die studierten Clathrate lassen sich in zwei Gruppen einteilen, je nachdem ob die Abgabe des Gastmoleküls G entweder vor oder unter Gleichzeitiger Zerstörung des Wirtskomplexes erfolgt. Kinetische Parameter wurden ermittelt.

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Q- [M(NCS)₂(4-MePy)₂]·nG, M , , , G — 4- , . , . .

     

Effect of nickel on the hydrogenating activity of MoS2

The activating effect of nickel on MoS₂ impregnated with an aqueous solution of Ni(CH₃COO)₂ and sulfided has been established to be proportional to the amount of active nickel incorporated as Ni²⁺ cations in the MoS₂ lattice. MoS₂ capacity for active nickel is limited and determined by the preparation method of the parent MoS₂.

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MoS₂ ( Ni(CH₃COO)₂, ) Ni²⁺, . MoS₂ «» .

     

Temperature-programmed desorption (TPD) of hydrogen from a NiNaY zeolite after reduction

By TPD it could be shown that hydrogen desorption of a reduced NiY-zeolite stoichiometrically corresponds to the decrease of reduction degree. Therefore, the reason for hydrogen abstraction should be a partial reoxidation of Ni⁰.

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, NiY- . Ni⁰.

     

CO oxidation to CO2 by Mo?V?P heteropolyacid in the presence of an aqua complex of Pd(II)

Kinetic oxidation of CO to CO₂ by Mo–V–P heteropolyacid in the presence of an aqua complex of Pd(II) has been studied. The reaction is suggested to involve the participation of carbonyl complexes of Pd(I). It has been established that VO ₂ ⁺ ions formed in HPA dissociation inhibits the reaction.

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CO CO₂ - Pd(II). Pd(I). , VO ₂ ⁺ , , .

     

Kinetic studies of Pt/Al2O3 catalyst pellets with nonuniform activity

Catalysts with nonuniform distribution of the catalytically active component (Pt) over their porous support (Al₂O₃) have been studied. A nonuniform activity distribution changes not only the reaction rate but also the kinetics can be different on these catalysts.

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(Pt) (Al₂O₃). , , .

     

IR and thermal studies on lithium oxomolybdenum(VI) oxalate

A new molybdenum(VI) complex, Li₂[Mo₂O₆(C₂O₄)] · 2 H₂O (LMO), was prepared and characterized by chemical analysis and IR spectral studies. Its thermal decomposition was studied by using TG and DTA techniques. LMO loses its two moles of water between 75 and 170° to give the anhydrous product, which decomposes in three stages between 240 and 380°. The first two stages occur in the temperature ranges 240–280° and 280–305°, to give intermediates with the tentative compositions Li₆[Mo₆O₁₉(C₂O₄)₂] and Li₆[Mo₆O₂₀(C₂O₄)], respectively. In the third stage, which extends up to 380°, Li₆[Mo₆O₂₀(C₂O₄)] decomposes to give the end-product, Li₂Mo₂O₇.

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Zusammenfassung Ein neuer Molybdän(VI)-Komplex der Formel Li₂[Mo₂O₆(C₂O₄)] · 2 H₂O (LMO) wurde dargestellt und durch chemische Analyse und IR-spektroskopisch charakterisiert. Die thermische Zersetzung dieses Komplexes wurde mittels TG und DTA untersucht. LMO verliert die zwei Wassermoleküle zwischen 75 und 170° unter Bildung des wasserfreien Produktes, das zwischen 240 und 380° in drei Stufen zersetzt wird. Die in den Temperaturbereich von 240–280° und 280–305° verlaufenden ersten zwei Reaktionsschritte ergeben Intermediäre der tentativen Zusammensetzung Li₆[Mo₆O₁₉(C₂O₄)₂] bzw. Li₆[Mo₆O₂₀(C₂O₄)]. In dem sich bis 380° erstreckenden dritten Reaktionsschritt wird Li₆[Mo₆O₂₀(C₂O₄)] unter Bildung des Endproduktes Li₂Mo₂O₇ zersetzt.

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Li₂[MO₂O₆(C₂O₄] · 2 ₂ . . - 70–170° , , 240–380°. 240–280° 280–305° - Li₆[Mo₆O₁₉(C₂O₄)₂] Li₆[Mo₆O₂₀(C₂O₄)]. - 380° Li₂Mo₂O₇.

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The authors are grateful to Prof. S. N. Tandon, Head of the Chemistry Department, for providing the research facilities.     

Transverse photothermal deflection spectroscopy (PDS) applied to thermal diffusiyity measurements

Transverse photothermal deflection spectroscopy(PDS) is applied for the determination of thermal diffusivities of solid surfaces. The theory of PDS is briefly recalled and some approximated analytical formulae concerning the transverse configuration are derived. In materials where the thermal diffusivity is smaller than that of the air, the dependence of the deflection angle on the displacement between pump and probe beams is shown to have a minimum that relates to the thermal diffusivity, thereby allowing its straightforward measurement. Measurements carried out on Al₂O₃ samples with different porosities at room temperature show a good agreement between experiment and theory.

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Zusammenfassung Die transverse photothermische Reflektionsspektroskopie (PDS) wird zur Bestimmung der thermischen Diffusivität von festen Oberflächen herangezogen. Die Theorie der PDS wird kurz dargelegt und einige sich auf die transverse Konfiguration beziehenden analytischen Näherungsgleichungen abgeleitet. Es wird gezeigt, daß bei Materialien mit kleinerer thermischer Diffusivität als Luft die Abhängigkeit des Deflektionswinkels von der Ablenkung zwischen Pumpen- und Probenstrahl ein Minimum aufweist, das mit der thermischen Diffusivität im Zusammenhang steht und somit deren zuverlässige Messung ermöglicht. An Al₂O₃-Proben unterschiedlicher Porosität bei Raumtemperatur ausgeführte Messungen zeigen gute Übereinstimmung von Experiment und Theorie.

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. , . , , , , . , , .

     

V2O5/TiO2 oxidation catalysts, III. Oxidation of CO on pure and sodium-doped systems

The activity of vanadia/titania catalysts in CO oxidation has been tested and found to be of the same order as that observed for unsupported vanadia; the simultaneous presence of vanadium-sodium compounds cancels the activity, probably because of the elimination of labile V=0 species at surface defects.

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V₂O₅/TiO₂ CO, V₂O₅; - , , V=0 .

     

CO/H2 and CO2/H2 reactions with amorphous carbon-metal catalysts

By metal impregnation of selected naturally occurring organic materials followed by controlled carbonization, metal semicoke catalysts can be readily prepared. These catalysts have been tested in the synthesis of hydrocarbons and alcohols from CO/H₂ and CO₂/H₂ mixtures. Fe and Co preparations have been used. Relatively high temperatures are required when using these catalysts, which are quite active for synthesis using CO₂ and H₂. The pressure (5150 kPa) is very favorable both for the synthesis of liquid hydrocarbons (C₅–C₃₀) and alcohols (C₁–C₅).

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. CO/H₂ CO₂/H₂. Fe Co. , CO₂ H₂. 5150 ) (C₅–C₃₀) (C₁–C₅).