Discrimination of active sites for ethylene homologation and ethylene metathesis on molybdena silica catalyst

Active sites for ethylene homologation (3C₂H₄2C₃H₆) and ethylene metathesis (C₂H₄–¹²C₂+C₂H₄–¹³C₂2C₂H₄–¹³C₁) were discriminated by adding platinum to a reduced molybdena silica catalyst, and the former was presumed to be composed of several molybdenum species, while the latter was presumed to be composed of one molybdenum species.

---

(3C₂H₄2C₃H₆) (C₂H₄–¹²C₂+C₂H₄–¹³C₂2C₂H₄–¹³C₁) . , , .

     

Sintering of supported palladium

Sintering results of Pd supported on carbon black at 723–973 K, in water vapor, in H₂ and under high vacuum are reported. They are compared with sintering data of Pd on other supports. The observed sequences are: SiO₂C>sepioliteAl₂O₃>AlPO₄ and H₂O>high vacuum>H₂.

---

Pd 723–973 , , H₂ . Pd . : SiO₂Al₂O₃>AlPO₄ H₂O> >H₂.

     

Study of the adsorption properties of a natural Hungarian mordenite and its ion-exchanged derivatives

The texture and adsorption properties of a natural, Hungarian mordenite were investigated by electron microscopy and BET adsorption measurements. The properties of the ion-exchanged adsorbents were characterized by CO₂ and SO₂ isotherms. The measurements were evaluated on the basis of the pore-filling theory of Dubinin. We have found that at 20°C the H⁺-form of mordenite interacts preferably with CO₂, while on the Na⁺- and Ca²⁺-derivatives stronger adsorption of SO₂ takes place. This fact accounts for their applicability as selective adsorbents.

---

, . CO₂ SO₂. . , 20°C H⁺- CO₂, Na⁺- Ca²⁺- SO₂ . .

     

On the dioximine complexes of transition metals

Twelve new complexes NH₄[Co(DH)₂(SO₃)(amine)]·t H₂O (DH ₂=dimethylglyoxime) have been synthesized and characterized. Their i.r. spectra show the SO₃ to be co-ordinated to the Co atom through the S atom. The thermal decompositions of a series of derivatives of this type have been investigated with a derivatograph. The first process is an endothermic dehydration reaction, occurring in a single stage or in two successive ones. The loss of the crystallization water is followed by another endothermic reaction, without a clear stoichiometry, which is referred to as deamination. At higher temperatures, exothermic pyrolysis processes occur. From the TG curves, kinetic parameters have been derived for the dehydration and deamination reactions.

---

Zusammenfassung Zwölf neue Komplexe der allgemeinen Formel NH₄[Co(DH)₂(SO₃)(amin)]·t H₂O (DH=Dimethylglyoxim) wurden synthetisiert und charakterisiert. Die IR-Spektren zeigen, daß SO₃ über das S-Atom koordinativ an das Co-Atom gebunden ist. Die thermische Zersetzung einer Reihe von Derivaten dieses Typs wurde mittels eines Derivatographen untersucht. Der erste Prozeß ist die in einem einzigen oder in zwei aufeinander folgenden Schritten verlaufende endotherme Dehydratisierung. Auf die Abgabe des Kristallwassers folgt eine andere endotherme Reaktion unklarer Stöchiometrie, die als Deaminierung bezeichnet wird. Bei höheren Temperaturen verlaufen exotherme Pyrolyseprozesse. Aus den TG-Kurven wurden kinetische Parameter für die Dehydratisierung und die Deaminierung bestimmt.

---

NH₄Co(DH)₂(SO₃)(a)]·tH₂O, DH ₂ — . , . . , . «». . .

     

Effect of oxygen on the catalytic reduction of nitric oxides by carbon monoxide over NiO

The catalytic reduction of nitrogen oxides (NO, N₂O and NO₂) by carbon monoxide over NiO has been studied in the temperature range from 200 to 500°C. The reaction of NO₂ with CO is much faster than that of NO with CO. The former reaction in the presence of a 3–4-fold excess of oxygen proceeds at a significant rate. In the temperature range studied, NO₂ decomposes to N₂ and O₂.

---

200–500°C (NO, N₂O NO₂) NiO. NO₂ CO NO CO. NO₂ CO 3–4- . NO₂ N₂ O₂.

     

Interactions between aminoacids and alcohols in water at 25 °C

The enthalpies of dilution of ternary aqueous solutions containing an alcohol (ethanol,n-propanol,n-butanol or tert-butanol) and an aminoacid or a peptide (glycine, glycyl-glycine or glycyl-glycyl-glycine), were measured at 25 °C. The results were used to calculate pair cross interaction parameters between solutes. The coefficients of virial expansion of the excess enthalpies are compared with those referring to solutions containing the same alcohols and other structure-breaking solutes (urea, thiourea and biuret). The enthalpic pair parameter for the systems glycine-alcohols shows the same trend, as reported in the literature, for similar structure-breaking solutes, with a maximum in the cross coefficients when reported versus the self pair interaction coefficients of alcohols. The results are interpreted in terms of a prevailing release of water from the cospheres of alcohols.

---

Zusammenfassung Die Verdünnungsenthalpien ternärer wässeriger Lösungen, die einen Alkohol (Ethanol,n-Propanol,n-Butanol odertert-Bulanol) und eine Aminosäure oder ein Peptid (Glycin, Glycil-glycin oder Glycyl-glycyl-glycin) enthalten, wurden bei 25 °C gemessen. Die erhaltenen Werte wurden zur Berechnung der Parameter der zwischen den Molekülen der verschiedenartigen gelösten Stoffe auftretenden Wechselwirkungen herangezogen. Die Koeffizienten der Virialentwicklung der Überschussenthalpien werden mit denen verglichen, die sich auf die gleichen Alkohole und andere strukturbrechende gelöste Stoffe (Harnstoff, Thioharnstoff und Biuret) enthaltenden Lösungen beziehen. Die Enthalpieparameter der Systeme Glycin-Alkohole zeigen den in der Literatur für ähnliche strukturbrechende gelöste Stoffe mitgeteilten Trend nämlich ein Maximum in der Kurve, die beim Auftragen der Koeffizienten der Wechselwirkung zwischen verschiedenartigen Molekülen gegen die Koeffizienten der Wechselwirkung zwischen den Alkoholmolekülen erhalten wird. Die Ergebnisse werden unter Annahme eines bevorzugten Austritts von Wasser aus der Kosphäre der Alkohole interpretiert.

---

25° , (, -, - - ), (, -- ). . , , (, ). — , - . .

---

---

This work is financially supported by the Italian Ministry of Public Education and by the Italian National Research Council.     

Sorption of H2, O2 and CO on bimetallic catalysts Pd?Ag/Al2O3 over a wide temperature range

Adsorption of hydrogen, oxygen and carbon monoxide on Pd–Ag/Al₂O₃ catalysts of different compositions within the temperature range from 293 to 773 K has been investigated. Adsorption measurements have been carried out by the pulse chromatographic method. The results obtained reflect interactions of the above adsorbates with the alloy surface, strongly enriched in silver atoms, as a result of surface segregation processes.

---

, Pd–Ag/Al₂O₃ 293–773 K. . , , .

     

Reaction kinetics of electron transfer between tungstovanadophosphoric heteropolyanions and Fe(II) ions

The reduction of PW_12–nV_nO₄₀ ^(3+n)– (n=1–4) heteropolyanions with Fe(II) ions occurs via intermediate complex formation. The rate constants of electron transfer in this complex tend to decrease in accord with the change of the oxidation potential of the heteropolyanions.

---

PW_12–nV_nO ₄₀ ^–(3+n) (n=1–4) Fe(II) . .

     

Ethylene oxidation by lithium nitrate in the presence of palladium acetate in acetic acid

Data are reported on variations of the gas phase volume and product accumulation in ethylene oxidation by lithium nitrate in acetic acid solutions, catalyzed by palladium acetate. An assumption is made on the routes of nitrate ion reduction.

---

, , . -.

     

Generation of model reactions leading to limit cycle behavior

The system of differential equations by Feistel and Ebeling has been generalized. Some new formal kinetic reactions with two internal components, which may exhibit limit cycle behavior have been studied. Based upon the numerical integration of the deterministic models of these reactions the oscillatory character of the systems has been confirmed.

---

. , . .

     

High-temperature reduction of SO2 by methane at various CH4/SO2 ratios

The character of the effect of initial reaction mixture and temperature on the selectivity of catalytic reduction of sulfur dioxide by methane in the presence of oxygen has been studied.

---

.

     

Study of selective dissociation in C6F5H?C6F5D mixtures induced by intense CO2 laser pulses

Irradiation of a C₆F₅H–C₆F₅D mixture at 1 Torr by a tunable CO₂ pulse laser brings about chiefly dissociation of one component depending on the frequency of emission absorbed by the proper molecules. The addition of radical acceptors increases the selectivity by suppressing secondary reactions.

---

C₆F₅H C₆F₅D 1 CO₂-, , . .

     

Non-empirical calculations for the probable coordinative binding of electron donor molecules by [AlO4] tetrahedra

Interaction of H₂O, NH₃ and C₅H₅N molecules with the aluminium atom of [AlO₄] tetrahedra has been calculated by the non-empirical SCF-MO LCAO method using an STO-3G basis set. The effect of Al–O bond lengths and O–Al–O angles on the calculated characteristics of chemisorbed complexes is discussed.

---

, TO-3C , [AlO₄]. Al–O O–Al–O .

     

Dehydration-dehydrogenation of 1- and 2-butanols on lanthanide oxide catalysts

Catalytic decomposition of 1- and 2-butanols on the rare earth oxides CeO₂, Pr₆O₁₁, and Me₂O₃ (Me=La, Sm, Eu, Dy, Ho and Yb) has been studied. Dehydration-dehydrogenation selectivity of these oxides was analyzed from the point of view of the fractional selectivity (S_F). For the decomposition of 2-butanol and the product distribution on the lanthanide oxides, preferential orientation to Hofmann olefin as well as a cis/trans ratio slightly higher than that of the equilibrium value is observed.

---

1- 2- CeO₂, Pr₆O₁₁ Me₂O₃ (Me=La, Sm, Eu, Dy, Ho Yb). - (S_F). 2- , , / .

     

Thermal analysis of thermosetting resins

Applications of thermoanalytical methods for the study of the resinification and curing of phenolic resins are reviewed. Examples are given to illustrate the use of DSC for practical industrial systems such as paper impregnants and saturated papers.

---

Zusammenfassung Es wird eine Übersicht über die Anwendungen thermoanalytischer Methoden zur Untersuchung der Harzbildung und der Aushrtung von phenolischen Harzen gegeben. Anhand von Beispielen wird die Verwendung der DSC für praktische industrielle Systeme wie Papierfüllstoffe und gefüllte Papiere aufgezeigt.

---

, . , .

     

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.

---

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.

---

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.

---

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

---

---

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

Effect of magnetic order on the conductivity in Co-Zn ferrites

A series of samples in the system Co_1–xZn_xFe₂O₄ (x=0.3, 0.4, 0.6, 0.8 and 1) were prepared by the usual ceramic technique. The D. C. electrical resistivity and thermoelectric power were measured in the temperature range from room temperature up to about 600 K. Transition from the ferrimagnetic region to the paramagnetic region is accompanied by an increase in the activation energy by an amountE, which varies in the range 0.052–0.090 eV. The large values ofE obtained may be due to the fairly strong B-B exchange interaction in Co-Zn ferrites.

---

Zusammenfassung Mittels üblicher Keramiktechniken wurden Proben des Systemes Co₁–xZn_xFe₂O₄ unterschiedlicher Zusammensetzung (x=0,3, 0,4, 0,6, 0,8, 1,0) dargestellt. Im Temperaturbereich Raumtemperatur-600 K wurde der elektrische Widerstand gegenüber Gleichstrom sowie die Thermospannung dieser Proben ermittelt. Der Übergang von der ferrimagnetischen zur paramagnetischen Region wird von einem Anwachsen der Aktivierungsenergie um den BetragE=0,052–0,090 eV begleitet. Den so erhaltenen grossen E-Werten liegen wahrscheinlich die ziemlich starken B-B Austausch Wechselwirkungen in Co-Zn Ferriten zu Grunde.

---

_1–xZn_xFe₂₄ =0,3;0,4;0,6;0,8 1, 600 . E, 0,052–0,090 . E - - .

     

Application of emissionless infrared diffuse reflectance spectrometry for following reactions of adsorbed alcohols on an alumina catalyst

IR spectra of adsorbed alcohols on alumina were measured under the reaction conditions at elevated temperatures. The transient response of IR absorption intensity indicates that alkoxides are reactive adsorbed species but carboxylates are not. The rate constants of surface reactions were calculated from the transient response.

---

, . , , , —, .

     

Preparation of catalysts by spray decomposition

Spray decomposition of solutions is an uncommon but very promising technique for the preparation of multicomponent solid systems with welldefined structure. The experimental arrangement is described and a summary of the systems prepared until now is given. These are MgO–ZnO, CaO, CdO, Al₂O₃. Fe₂O₃ solid solutions and CdO. CdSO₄ and Al₂O₃. Al₂(SO₄)₃ systems.

---

, , . : MgO·ZnO, CaO·CdO,. Al₂O₃·Fe₂O₃ CdO·CdSO₄ Al₂O₃·Al₂ (SO₄)₃.