Vacancies in the solids of low molecular weight organic compounds observed by positron annihilation

PAL were measured for several low molecular organic compounds, normal and cyclic-hydrocarbons and their perfluorinated ones, from room temperature down to about 40 K, and information about the vacancies in them has been extracted from ₃ andI ₃. Normally the size of vacancies were larger in the solids comprising larger molecules, showing thato-Ps can represent the vacancy size. In a special case of perfluorocyclohexane whose solid had to be prepared by sublimation the vacancy size was larger than expected. In all the solid molecules studied twoo-Ps states could be observed and their relative importance could easily change showing a hysteresis-like behavior. At further lower temperatures of around 40 K theo-Ps state with longer lifetime and larger intensity became overwhelming for all molecules. Also ₃ andI ₃ were not very sensitive to most of the phase transitions, including the melting points.     

Positron annihilation in polyvinylalcohol doped with CuCl2

Positron annihilation lifetime spectra were measured forpolyvinylalcohol (PVA) doped with CuCl₂ (0.5 to 5.0 wt%) at temperature range from room temperature to 160°C. For a fresh pure PVA (without annealing) ₃ belowT _g was larger in the heating runs than in the cooling runs, but aboveT _g, ₃ was the same for both runs. The larger ₃ values in the heating run were considered to be due to the existence of strain brought forth in the process of preparation. For annealed pure PVA ₃ was the same for the heating and the cooling runs andT _g was shifted to lower temperature, 88 and 80°C for fresh and annealed samples, respectively. This shift was attributed to loss of H-bonded water in the annealed pure PVA by heating above 100°C. BothI ₃ ⁰ and ₃ were decreased by the added CuCl₂, being interpreted as the result of inhibition and quenching, respectively. The results show that both the inhibition coefficient and the quenching rate constantk were smaller than the corresponding values in liquids. The small diffusion constant ofo-Ps estimated fromk implies thato-Ps is not very mobile in the polymer.     

Differential thermal analysis studies on the kinetics of crystallization of calcium tungstate from solutions in sodium tungstate melts

The kinetics of calcium tungstate crystallization from solutions in sodium tungstate melts were studied in a platinum crucible by continuous cooling from an initial crystallization temperatureT ₀=800 to 1000 to below the eutectic temperature at cooling ratesR _T=0.67 to 3.3 min^–1. The main crystal growth was diffusion rate-controlled. The diffusion rate-constant (k _D) values for the growth along the major axis were estimated. Such values increased with the cooling rate and initial crystallization temperature. They were lower than those for diffusion-controlled growth of calcium tungstate from sodium tungstate melts in alumina crucibles. The experimentalk _D values were compared with the theoreticalk _D values.

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Zusammenfassung Die Kinetik der Kristallisation von Calciumwolframat aus Lösungen von Natriumwolframatschmelzen wurde im Platintiegel durch kontinuierliches Kühlen von der AnfangskristallisationstemperaturT ₀=800 bis 1000 bis unter die eutektische Temperatur, bei Abkühlgeschwindigkeiten vonR _T =0.67 bis 3.3 min^–1, untersucht. Das Hauptkristallwachstum wurde durch die Diffusionsgeschwindigkeit bedingt. Die Werte der Diffusionsgeschwindigkeitskonstante (k _D) in Richtung der Hauptachse wurden geschÄtzt. Diese Werte nahmen mit der Abkühlgeschwindigkeit und der Anfangskristallisationstemperatur zu. Sie waren niedriger als jene des diffusionsbedingten Wachstums von Calciumwolframat aus Natriumwolframatschmelzen in Aluminiumtiegeln. Die experimentellenk _D-Werte wurden mit den theoretischenk _D-Werten verglichen.

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Résumé La cinétique de la cristallisation du tungstate de calcium à partir de ses solutions dans le tungstate de sodium fondu a été étudiée dans un creuset de platine au cours du refroidissement continu depuis la température initiale de cristallisationT ₀=800 à 1000 C jusqu'à température inférieure à celle de l'eutectique, avec des vitesses de refroidissement allant de 0.67 à 3.3 C · min^–1. La croissance des cristaux est contrÔlée principalement par le processus de diffusion. Les valeurs de la constante de vitesse de diffusion (k _D) ont été estimées pour la croissance le long de l'axe principal. Ces valeurs augmentent avec la vitesse de refroidissement et la température initiale de cristallisation et sont plus faibles que les valeurs correspondantes en creusets d'alumine. Les valeurs expérimentales et théoriques dek _D sont comparées.

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₀=800 1000 R =0.67 3.3 ^–1. . (k _d ) . . , - . k _d .

     

Localization of gallium in erionite type Ga?Al zeolites by71Ga,27Al and29Si NMR

The state of Al³⁺, Ga³⁺ and Si⁴⁺ in erionites obtained by hydrothermal crystallization from Ga–Al–Si gels has been examined. The results suggest that gallium cations can isomorphously substitute a part of silicon cations in the zeolite framework, to a notable extent in the sites having no aluminium cations in the second coordination sphere of silicon.

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Al³⁺, Ga³⁺ Si⁴⁺ , . , , .

     

Correlation between solvent-reorganization dynamics and the kinetics of metallotropy in polar media

The kinetics of metallotropy of the 3,6-di-tert-butyl-2-(triphenylstannyl)oxyphenoxyl radical has been studied by ESR. The correlation between chemical exchange time _ex, solvent polarity, and longitudinal relaxation time of the solvent corresponds to the model of a process controlled by molecular dynamics. A linear relation between _ex and correlation time _c for reorientation movements of the radical is found: _ex = · _c. The coefficient depends on the dielectric properties of the solvent.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 410–413, March, 1994.This work was supported by the Russian Foundation for Basic Research, project No. 93-03-4372.     

Results of thermal analysis for investigation of salt hydrates as latent heat-storage materials

DTA and DSC methods and quasi-isothermal and quasi-isobaric thermogravimetry are of great importance in the investigation of salt hydrates as latent heat-storage materials. However, the transferability of the DTA and DSC results is given only for application in static latent heatstorage units. Special calorimetric methods adapted to the storage principle are preferred for the study of salt hydrates under dynamic storage conditions. The findings are discussed in connection with the examples of Na₂SO₄·10H₂O, CH₃COONa·3H₂O, Na₂S·9H₂O, Na₂S·5H₂O, Mg(NO₃)₂·6H₂O, MgCl₂·6H₂O and the eutectic mixture of Mg(NO₃)₂·6H₂O-MgCl₂·6H₂O.

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Zusammenfassung Bei der Untersuchung von Salzhydraten als Latentwärmespeichermaterialien besitzen DTA-, DSC-Methoden und die quasi-isotherme und quasi-isobare Thermogravimetrie eine wesentliche Bedeutung. Die Übertragbarkeit der DTA- und DSC-Ergebnisse ist jedoch nur für den Einsatz in statischen latentwärmespeichern gegeben. Für das Studium der Salzhydrate under dynamischen Speicherbedingungen werden spezielle, dem Speicherprinzip angepaßte kalorimetrische Methoden bevorzugt. Die Aussagen werden an den Beispielen Na₂SO₄·10H₂O, CH₃COONa·3H₂O, Na₂S·9H₂O, Na₂S·5H₂O, Mg(NO₃)₂·6H₂O, MgCl₂·6H₂O und der eutektischen Mischung von Mg(NO₃)₂·6H₂O-MgCl₂·6H₂O diskutiert.

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, . , . , . Na₂SO₄·10H₂O, CH₃COONa·3H₂O, Na₂S·5H₂O, Na₂S·9H₂O, Mg(NO₃)₂·6H₂O, MgCl₂·6H₂O Mg(NO₃)₂·6H₂O·MgCl₂·6H₂O.

     

Intramolecular Mobility in the Complexes 2SbCl3· p-C6H4(CH3)2and SbCl3· C6H5COCH3according to 35Cl NQR Data

Temperature dependences of the ³⁵Cl and ¹²¹Sb spin-lattice relaxation time ₁in antimony trichloride complexes with p-xylene and acetophenone were studied using NQR spectroscopy. The activation energies of the retarded motion (similar to that discovered in some v complexes of SbCl₃) of chlorine atoms were determined from the ³⁵Cl ₁(T) function. New data on the shape of the ¹²¹Sb ₁(T) function are discussed.     

Differential Thermal and Thermogravimetric Studies of Carbonatodiphenanthrolinecobalt(III) Complexes

The [CoPhen₂CO₃]X ·nH₂O complexes, where Phen, phenanthroline; X · nH₂O = Cl · 5H₂O, Br · 4H₂O, I · 4H₂O, NCS · 3H₂O, NO₂ · 5H₂O, NO₃ · 3H₂O, ClO₄, and ClO₃, are studied by the differential thermal and thermogravimetric methods. After the endoeffect of complete dehydration of the complexes, the DTA curves exhibit effects of the ^III reduction to ^II by the outer-sphere chloride, bromide, and iodide anions. In the case of the outer-sphere nitrite anion, the endoeffect of the reduction of ^III with the nitrito group is followed by the exoeffect of oxidation of the organic ligand with the nitrogen dioxide formed. In the case of the outer-sphere chlorate and perchlorate anions, the complexes are decomposed at temperatures of 250 and 310°, respectively, without preliminary ^III reduction.     

Thermal studies on titanyl,zirconyl and hafnyl dithiocarbamato complexes

The dithiocarbamato complexes of titanyl(IV), zirconyl(IV) and hafnyl(IV), abbreviated as MO(S₂CNRR)₂·nH₂O(M=Ti, Zr or Hf,R=H,R=C₅H₉;R=H,R=C₇H₁₁,n=1 for Ti andn=2 for Zr and Hf), were prepared in aqueous medium and characterized by elemental analyses, magnetic susceptibility measurements and IR spectral studies. The thermal behaviour of these compounds under non-isothermal conditions was investigated by thermogravimetric, derivative thermogravimetric and differential scanning calorimctric techniques in nitrogen and oxygen atmospheres. The intermediates obtained at the end of various thermal decomposition steps were identified on the basis of analyses and IR spectral studies. Kinetic parameters, such as apparent activation energy and order of reaction, were determined by the graphical method of Coats and Redfern. The heats of reaction for the different decomposition steps were calculated from the DSC curves.

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Zusammenfassung Die Thiocarbamato-Komplexe von Titanyl(IV), Zirkonyl(IV) und Hafnyl(IV) der allgemeinen Formel MO(S₂CNRR)₂·n H₂O (M=Ti, Zr oder Hf;R=H, R=C₅H₉;R=H, R=C₇H₁₁;n=1 für Ti undn=2 für Zr und Hf) wurden in wässrigem Medium hergestellt und durch Elementaranalyse, Messung der magnetischen Suszeptibilität und IR-Spektraluntersuchungen charakterisiert. Das thermische Verhalten dieser Verbindungen unter nicht-isothermen Bedingungen wurde durch TG, DTG und DSC in Stickstoff- und Sauerstoffatmosphäre untersucht. Die nach verschiedenen thermischen Zersetzungsschritten erhaltenen Zwischenprodukte wurden durch chemische Analyse und IR-Spektroskopie identifiziert. Kinetische Parameter, wie die scheinbare Aktivierungsenergie und die Reaktionsordnung, wurden nach der graphischen Methode von Coats und Redfern bestimmt. Für die einzelnen Zersetzungsschritte wurden die Reaktionswärmen aus den DSC-Kurven berechnet.

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, . MO(S₂CNRR)₂·nH₂O (M=I, Zr, Hf,R=H,R ¹=C₅H₉, C₇H₁₁,n=1 I =2 ) , . , . , , . - . .

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The authors are grateful to Dr. Shyam Kumar for helpful discussions.     

Verfolgung der Verbrennungsreaktionen Exothermer Massen auf Basis von Aluminium,Fluoriden und Natriumverbindungen mit Differenzialthermoanalyse

Zusammenfassung Das Verbrennen von Mischungen der exothermen Systeme Al-NaF-NaNO₃ und Al-CaF₂-NaNO₃ wurde durch Röntgenanalyse ergänzte DTA untersucht. Um den Einfluß des durch Dissoziation von NaNO₃ gebildeten Sauerstoffs zu bestimmen wurden auch Mischungen, welche anstatt NaNO₃ NaNO₂ oder Na₂O₂ enthielten, geprüft.Zwei, bei 310° bzw. 850° einsetzende exotherme Reaktionen wurden in den Gemischen vom Typ Al-NaF-NaNO₃ gefunden. Die erste ist der Dissoziation von NaNO₃ zuzuschreiben, die zweite ist der Anwesenheit von Luft zuzuordnen.Beide exothermen Reaktionen wurden im System Al-CaF₂-NaNO₃ in Richtung höherer Temperaturen verschoben. Die Untersuchung der NaNO₂- oder Na₂O₂-haltigen Gemische anstatt NaNO₃ zeigte, daß die Dissoziation von NaNO₃ den zum Verbrennen benötigten Sauerstoff liefert, andererseits würde letztere Reaktion sonst nur in begrenztem Ausmaß stattfinden.

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Combustion of exothermic mixtures belonging to the system Al-NaF-NaNO₃ and Al-CaF₂-NaNO₃ was investigated by DTA and X-ray analysis. In order to determine the influence of the oxygen generated by dissociation of NaNO₃, the mixtures containing NaNO₂ or Na₂O₂ instead of NaNO₃ were also examined.Two exothermic reactions starting at 310° and 850° rsp. were found in the mixtures of the Al-NaF-NaNO₃ type. The first is due to the dissociation of NaNO₃ and the second proceeds independence of the availability of air.Both exothermic reactions were shifted to higher temperatures in the system Al-CaF₂-NaNO₃. Investigation of the mixtures containing NaNO₂ or Na₂O₂ instead of NaNO₃ has proved that the dissociation of NaNO₃ supplies the oxygen required for combustion which should otherwise proceed only in a limited extent.

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Résumé On a étudié, par ATD et par analyse aux rayons X, la combustion des mélanges exothermiques appartenant aux systèmes Al-NaF-NaNO₃ et Al-CaF₂-NaNO₃. Afin de déterminer l'influence de l'oxygène engendré par la dissociation de NaNO₃, on a étudié de même des mélanges contenant NaNO₂ ou Na₂O₂ au lieu de NaNO₃.On a trouvé, dans les mélanges du type Al-NaF-NaNO₃, des réactions exothermiques à partir des temperatures respectives de 310° et 850°. La première est due à la dissociation de NaNO₃ et la seconde dépend de l'air disponible.Dans le système Al-CaF₂-NaNO₃ les deux réactions sont déplacées vers les températures plus élevées. L'examen de mélanges contenant NaNO₂ ou Na₂O₂ au lieu de NaNO₃ à montré que c'est la dissociation de NaNO₃ qui fournit l'oxygène nécessaire pour la combustion. Celleci n'aurait lieu, autrement, que d'une manière limitée.

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, l-NaF-NaNO₃ Al-CaF₂-NaNO₃. , NaNO₃, , NaNO₃, , NaNO₂ Na₂. , Al-NaF-NaNO₃ , 310° 850°. , . Al-CaF₂-NaNO₃ . , NaNO₂ Na₂O₂, , , , , .

     

Dispersity and reducibility of the molybdenum oxide phase in SiO2, SiO2?Al2O3 and γ-Al2O3 supported molybdena catalysts

XRD, isothermal and temperature-programmed reduction (TPR) experiments were carried out with SiO₂, SiO₂–Al₂O₃ and -Al₂O₃ supported catalysts. Molybdena is in a more disperse state on supports containing more alumina and it is more reducible on SiO₂–Al₂O₃ than on SiO₂ or -Al₂O₃. TPR curves were shown to reflect connections between reduction kinetics and dispersity.

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-, , SiO₂, SiO₂–Al₂O₃ -Al₂O₃. , , SiO₂–Al₂O₃ SiO₂ -Al₂O₃. .

     

Spectral properties and temperature-dependence of semiconductivity of various doped bismuth trioxide polycrystals

Several samples of Nb₂O₅-doped Bi₂O₃ and Y₂O₃-doped Bi₂O₃ were carefully prepared and sintered at 700° for 3 hours. Extensive measurements were carried out on these samples, including X-ray diffraction spectra, infrared absorption spectra and the temperature-dependence of the DC-electrical conductivity in the solid state. The results obtained were discussed, correlated and interpreted. Finally, the optimum compositions were established and recommended for doped-Bi₂O₃ in the electronics industry.

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Zusammenfassung Einige Proben von mit Nb₂O₅ und Y₂O₃ gedopten Bi₂O₃ wurden hergestellt und bei 700 °C 3 Stunden gesintert. Von den Proben wurden Röntgendiffraktogramme und IR-Absorptionsspektren aufgenommen und die Temperaturabhängigkeit der elektrischen Gleichstromleitfähigkeit im festen Zustand gemessen. Die erhaltenen Ergebnisse werden diskutiert, zueinander in Beziehung gesetzt und interpretiert. Optimale Zusammensetzungen werden ermittelt und für gedoptes Bi₂O₃ in der Elektronikindustrie empfohlen.

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Bi₂O₃, Nb₂O₅ Y₂O₃, 3 700°. , . . , .

     

Crystallization of iron phosphate glasses

Differential thermal analysis (DTA), thermogravimetric analysis (TG), X-ray diffraction and Mössbauer spectroscopy were employed in the investigation of crystalline products of FeO_x-P₂O₅ glasses generated by various heat treatments. In glasses with a high value of =Fe²⁺/(Fe²⁺ + Fe³⁺), absorption of oxygen occurs in a broad temperature range identified by TG. Depending on the value of , two exotherms appear in the DTA curves, the low-temperature one corresponding to crystallization of the Fe₃(PO₄)₂ type regions, and the high-temperature one being related to various phases with dominating FePO₄. Each exotherm has its own transformation region, identical in absolute value. The Mössbauer spectra of glasses which underwent thermal treatment at higher temperatures exhibit some indication of phases of the types Fe₃(PO₄)₂ · xH₂O and FePO₄ · xH₂O.

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Zusammenfassung Differentialthermoanalyse (DTA), thermogravimetrische Analyse (TG), Röntgendiffraktion und Mössbauerspektroskopie wurden bei der Untersuchung (von kristalliner Produkte) durch verschiedene thermische Behandlungen hergestellten FeO_x-P₂O₅ Gläsern eingesetzt. In den Glasarten mit einem hohen Wert von =Fe²⁺/(Fe²⁺ + Fe³⁺) erfolgt die Sauerstoffabsorption in einem durch TG [nachgewiesenen breiten Temperaturbereich. In Abhängigkeit von dem -Wert erscheinen zwei Exothermen in den DTA-Kurven, von denen der bei niedriger Temperatur die Kristallisation des Fe₃(PO₄)₂ entspricht, und jener bei höheren Temperaturen in verschiedenen Phasen dem FePO₄. Jede Exotherme hat ihr eigenes Umwandlungsgebiet, das in absolutem Wert identisch ist. Die Mössbauer-Spektren der Gläser welche einer Wärmebehandlung bei höheren Temperaturen unterzogen worden sind, weisen einige Indikationsphasen der Typen Fe₃(PO₄)₂ · xH₂O und FePO₄ · xH₂O auf.

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, , FeO_x-P₂O₅, . , =Fe²⁺/(Fe²⁺+Fe³⁺) . , - : Fe₃(PO₄)₂, – FePO₄. , . , , Fe₃(PO₄)₂ · ₂ FePO₄ · ₂.

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The authors thank Mrs. Simonyiová for assistance in the experimental part of these investigations, and Dr. Horváth and Dr. Vondrovic for performing the X-ray and TG analyses.     

α BB Resonance in the ν8 Band of Borazine –10B

The high-resolution FTIR spectrum of the fundamental ₈ of borazine ¹⁰B₃ ¹⁴N₃ ¹H₆ was reanalyzed taking into account the ^BB resonance with the combination band (₁₀ + ₁₇). A parameter set for the states ₈ = 1 and ₁₀ = ₁₇ = 1, respectively, is given, reproducing the observed spectrum at least up to J = 30 with experimental accuracy.     

Vibrational isotope effect of linear and planar molecules: Deuterated bromoethenes

Linear (planar) molecules A and B which are identical except for isotopic substitutions at the atomic sites are considered. Stretching (bending, out-of-plane) frequencies _k and normal modes _k of the isotopically perturbed molecule B are expressed in terms of stretching (bending, out-of-plane) frequencies _i and the corresponding normal modes _i of the unperturbed molecule A. Complete specification of the unperturbed normal modes is not required. All that is needed are stretching (bending, out-of-plane) amplitudes | _i of the normal modes _i at those sites that are affected by isotopic substitution. The rule which interlaces frequencies _k of molecule A with frequencies _i of molecule B is derived. Given two isotopic molecules A and B that differ by a single isotopic substitution at site , the inversion relation is derived. This relation expresses unperturbed stretching (bending, out-of-plane) amplitudes at the site in terms of stretching (bending, out-of-plane) frequencies of molecules A and B . As an example, out-of-plane vibrations of deuterated bromoethene were considered. In the simplest method 12 out-of-plane frequencies of four polydeuterated bromoethenes were calculated from 12 out-of-plane frequencies of bromoethene and three monodeuterated bromoethenes. Standard deviation of thus calculated frequencies from experimental frequencies is =2.74 cm^–1. In another method, 15 out-of-plane frequencies of four polydeuterated bromoethenes and selected monodeuterated bromoethene are calculated from 9 out-of-plane frequencies of bromoethene and the remaining two monodeuterated bromoethenes. Depending on which monodeuterated bromoethene is selected (1-, cis- or trans-), standard deviation of thus obtained frequencies from experimental frequencies is 1=2.84 cm^–1, c=2.96 cm^–1 and t=2.72 cm^–1.     

Interaction and exchange of propene with OH groups of HX zeolites

The interaction of C₃H₆ and the exchange of C₃D₆ with a HX zeolite dehydroxylated to various degrees was studied at the temperature of the IR beam and at 300 °C. The exchange was followed by the analysis of the gas phase (MS) and the solid phase (IR). The properties of HX and HY zeolites were compared.

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C₃H₆ C₃D₆ 300 °C HX . () () . HX HY .

     

M?ssbauer spectroscopic studies of the state of Pt?Sn/Al2O3 catalyst for hydrocarbon conversion

Mössbauer spectroscopic studies of the state of Pt–Sn catalyst for hydrocarbon conversion supported on prechlorinated -Al₂O₃ indicate that, unlike nonchlorinated Al₂O₃, this system is much more reduced and besides Pt₃Sn–PtSn₂, its surface contains sigfificant amounts of Sn(II) and Sn(IV) chlorides bonded to the surface.

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Pt–Sn , -Al₂O₃. , Al₂O₃, Pt–Sn Pt₃Sn–PtSn₂ Sn(II) (IV), .

     

Possibilities of applying the piloyan method of determination of decomposition activation energies in the differential thermal analysis of polynitroaromatic compounds and their derivatives

Piloyan activation energiesE as well as initals of exothermT _D of sevenN-monoalkyl and fiveN,N-dialkyl-2,4-dinitroanilines were determined. Relationships were found between the T_D values and R_f factors as well asE values and those R_M functions and also theET _D ^–1 term and R_M functions.

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Zusammenfassung Die AktivierungsenergienE nach Piloyan sowie die Anfangswerte der ExothermenT _D wurden für siebenN-Monoalkyl- und fünfN,N-Dialkyl-2,4-dinitroaniline bestimmt. Die Zusammenhänge zwischen denT _D-Werten und den papierchromatographischenR _f-Faktoren der gemessenen Dinitroaniline wurden abgeleitet und erörtert. Desgleichen wurden auch die Zusammenhänge zwischen denE-Werten und denR _M-Funktionen der Papierchromatographie abgeleitet und erörtert. Auch zwischen dem AusdruckE ·T _D ^–1 und denR _M-Funktionen wurde ein Zusammenhang gefunden.

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Résumé On a déterminé les températures initialesT _D de l'effet exothermique ainsi que les énergies d'activationE d'après la méthode de Piloyan, de sept N-mono alcoyl et cinqN,N-dialcoyl-2, 4-dinitroanilines. Une corrélation entre les valeursT _D et les facteursR _f de la Chromatographie sur papier des dinitroanilines étudiées a été trouvée et discutée, ainsi qu'entre les valeursE et les fonctionsR _M de la Chromatographie sur papier. Une relation entre le termeE ·T _D ^–1 et les fonctionsR _M a également été trouvée.

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E T _D N- N,N- -2,4- . _D R _f , E R _M. E. _D ^–1 R _M.

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The authors would like to thank Mrs. Anna Collàkovà for careful DTA measurements, and Dr. Ladislav Smolka for help in treatment of the measured results with the Wang 600 computer.     

Effect of the Reaction Products on the Rate of Oxidation of Crotonaldehyde

Study of the oxidation of crotonaldehyde revealed an appreciable inhibitory effect of the products on the process. Analysis of the kinetic data obtained over a wide range of reaction conditions (c ₀ 1.5-3.3 M, pO₂ 1-16 atm, T 293-309 K) showed that the overall oxidation process (with account taken of the inhibitory effect of the products) is described by the equation: W _CA = k*_ap c _CA (pO₂)^0.6 (1 + 0.17c _CA)^{- 1}, where k*_ap is the apparent rate constant, and c _CA is the decrease of the aldehyde concentration by a moment .     

Reaction routes for hydrogenation of acetylene-ethylene mixtures using a double labelling method

Hydrogenation of C₂H₂:C₂H₄ mixtures using a double labelling method has been studied. Both in the presence and absence of ethylene the rate of acetylene hydrogenation on its partial pressure proceeds through a maximum and the rate is higher when ethylene is added. Using¹⁴C–C₂H₂ it was demonstrated that at low acetylene partial pressures the main route of acetylene hydrogenation was the formation of ethane and C₄ hydrocarbons. Using¹⁴C–C₂H₄ it was also shown that at certain acetylene partial pressures the formation of ethane from ethylene completely ceased. Different surface species are suggested and a reaction mechanism is proposed.

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C₂H₂:C₂H₄, . , , . C¹⁴–C₂H₂, , C₄. C¹⁴–C₂H₄, , . .