Thermal decomposition of potassium hexacyanoferrate(II) trihydrate

Potassium hexacyanoferrate(II) trihydrate, K₄Fe(CN)₆·3H₂O, was heated under controlled conditions of mass and rate in a derivatograph in the presence of oxygen. The heating was stopped at different temperatures and Mössbauer spectra and X-ray diffractograms were taken on the quenched material at room temperature. The reaction pathway was studied in this way and the advantages and drawbacks of each of the techniques are described. At different stages of the thermal process we were able to show the presence of K₄Fe(CN)₆,-Fe₂O₃, Fe₃O₄, Fe₃C, Fe, FeO, KFeO₂,-FeOOH, KOCN, K₂CO₃ and KCN.

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Zusammenfassung Kaliumhexacyanoferrat(II)trihydrat, K₄[Fe(CN)₆.3H₂O wurde unter kontrollierten Bedingungen in einem Derivatographen in Gegenwart von Sauerstoff erhitzt. Das Aufheizen wurde bei verschiedenen Temperaturen gestoppt und Mössbauer-Spektren, sowie Röntgendiffraktogramme aufgenommen. Der Reaktionsweg wurde auf diese Weise untersucht und die Vor- und Nachteile jeder der Techniken beschrieben. Bei den verschiedenen Stufen des thermischen Vorganges konnten K₄[Fe(CN)₆],-Fe₂O₃, Fe₃O₄, Fe₃C, Fe, FeO, KFeO₂,-FeOOH, KOCN, K₂CO₃ und KCN nachgewiesen werden.

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Resumé Le ferrocyanure de potassium trihydraté, K₄Fe(CN)₆·3H₂O, a été chauffé en présence d'oxygÊne dans un Derivatograph, dans des conditions bien déterminées de masse et de vitesse de chauffage. Le chauffage a été interrompu à diverses températures et les spectres Mössbauer ainsi que les diffractogrammes de rayons X ont été enregistrés aprÊs trempe du matériau à la température ambiante. On a étudié de cette faÇon le déroulement de la réaction; on décrit les avantages et les inconvénients de chacune de ces techniques. On a pu déceler la présence de K₄Fe(CN)₆,-Fe₂O₃, Fe₃O₄ Fe₃C, Fe, FeO, KFeO₂,-FeOOH, KOCN, K₂CO₃ et KCN aux différentes étapes du traitement thermique.

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- (II)- -₄F/)₆. 3₃- . . . K₄Fe(CN)₆, -Fe₂O₃, Fe₃O₄, Fe₃C, Fe, FeO, KFeO₂,-FeOOH, KOCN, K₂CO₃ KCN.

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This research was performed with financial support from the Conselho Nacional de Desenvolvimento Científico e TecnolÔgico (CNPq) and Financiadora de Estudos e Projetos (FINEP). We are grateful to Profs. A. Bristoti, J. Danon, P. J. Aymonino, E. Baran and M. A. Blessa for valuable suggestions and criticisms, and Miss E. A. Veit for performing the thermal measurements at the Pontificia Universidade Católica, Porto Alegre. This work was submitted in partial fulfilment of the conditions for the degree of Livre Docente by one of us (J. I. K.).     

Broadening and shift of Ν(AH)IR bands in a series of H complexes of one base with various acids

The parameters of the IR bands for the (AH) stretching vibration (the frequencies, the widths, and partly the intensities) were measured in a series of AH ... B H complexes between one base B (ethylene oxide) and 17 various OH, NH, and CH acids in carbon tetrachloride solutions. The width _1/2 and shift =₀ ⁰– (from the frequency ₀ ⁰ of the gaseous AH) of the investigated bands amount to 530 and 740 cm^–1. A relationship close to direct proportionality between the broadening and the shift of the band for the H bond was found for all the H complexes. The relationship was insensitive to the medium and was preserved for the gaseous complex and in the undiluted ethylene oxide; it did not change greatly when was calculated from the free AH in carbon tetrachloride. This partial (with constant B) proportionality is not observed in the traditional series of acids (phenol, alcohol) with various bases, where agreement is only observed for _1/2 and . cThe electric-donating power of ethylene oxide (0.79±0.03) on the E scale (with reference to diethyl ether, E=1) was determined from the increase and shift of (AH).Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 4, pp. 461–466, July–August, 1988.     

Quantum chemical calculations on the catalytic dehydration of 2-propanol

The charge on atoms and the bond strengths in CH₃CHOHCH₃, CH₃ CH₃, CH₃CHOHCH ₂ ^– , CH₃ CH ₂ ^– and CH₃ CH₃...O(H)CH(CH₃)₂ have been calculated by the CNDO/2 method. The results are in agreement with published experimental observations on catalytic dehydration. A modified mechanism of anti-elimination on solid catalysts is proposed.

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CH₃CHOHCH₃, CH₃ CH₃, CH₃CHOHCH ₂ ^– , CH₃ CH ₂ ^– CH₃ CH₃...O(H)CH(CH₃)₂, CNDO/2. . .

     

VUV-Photolyse von Methanol bei 1236 Å

Zusammenfassung Es wird über die indirekte und die direkte VUV-Photolyse von luftfreiem Methanol in flüssiger Phase bei 1236 Å berichtet. Bei der Bestrahlung von wäßr. 0,01m-Methanol wurden folgende Produkte und Ausbeuten erhalten: (H₂)=1,00, (HCHO)=0,27, (CH₂OH)₂=0,12, (CH₂OH·CHO)=0,04 und (HCOOH)=0,02. Die Photolyse von flüssigem Methanol lieferte die gleichen Produkte, jedoch mit höheren Ausbeuten: (H₂)=1,50, (HCHO)=0,98, (CH₂OH)₂=0,28 und (CH₂OH·CHO)=0,06. Unter Anwendung von Methanol als Radikalfänger konnte auch die Quantenausbeute der Wasserphotolyse bei 1236 Å, (H,OH)=1,025 verifiziert werden. Wahrscheinliche Reaktionsmechanismen werden diskutiert.

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V.U.V.-Photolysis of methanol at 1236 Å

The indirect and the direct v.u.v.-photolysis of air free methanol in liquid phase at 1236 Å is reported. After irradiation of aqueous 0.01M-methanol the following products were obtained: (H₂)=1.00, (HCHO)=0.27, (CH₂OH)₂=0.12, (CH₂OH·CHO)=0.04 and (HCOOH)=0.02. The photolysis of liquid methanol yielded the same compounds, however with higher amount as follows: (H₂)=1.50, (HCHO)=0.98, (CH₂OH)₂=0.28 and (CH₂OH·CHO)=0.06. Using methanol as a scavenger for the H and OH radicals the quantum yield of the water photolysis at 1236 Å could be verified to be (H,OH)=1.025. Probable reaction mechanisms are discussed.

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Mit 3 Abbildungen

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Herrn Prof. Dr.E. Broda zum 60. Geburtstag gewidmet.     

Thermochemical studies on the systems ACl/CeCl3 (A=Na-Cs)

The pseudobinary systems ACl/CeCl₃ (A=Na-Cs) were reinvestigated by means of DTA. The following compounds were found and identified through their X-ray patterns (primarily detected compounds in italics):NaCe _1.67 Cl ₆; K₃CeCl₆, K₂CeCl₅,KCe _1.67 Cl ₆;Rb ₃ CeCl ₆, Rb₂CeCl₅,RbCe ₂ Cl ₇; Cs₃CeCl₆, Cs₂CeCl₅,CsCe ₂ Cl ₇. The compounds A₂CeCl₅ crystallize with the K₂PrCl₅ structure. The high-temperature modifications of the compounds A₃CeCl₆ have the cubic elpasolite structure. The hexagonal unit cell of KCe_1.67Cl₆ is related to the CeCl₃ structure: 0.33 Ce³⁺ are substituted by one K^s+. The structure of CsCe₂Cl₇ can be described with a hexagonal subcellZ=4,a=9.72 andc=14.94 Å; however, small superstructure reflexions reduce the symmetry.The thermodynamic functions for the reactionsnACl+CeCl₃=A _n CeCl _n+3(A=K, Rb) were determined by means of e.m.f. measurements.Measurements of the e.m.f.E vs. T yielded the Gibbs enthalpiesG ^r . The temperature-dependence was found to be linear.The most important result is the formation of the elpasolites (A₃CeCl₆) and ACe₂Cl₇.

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Zusammenfassung Die pseudobinären Systeme ACl/CeCl₃ (A=Na-Cs) wurden mittels Differenzthermoanalyse (DTA) neu untersucht. Folgende Verbindungen wurden gefunden und durch ihre Röntgenbeugungsmuster charakterisiert (erstmalig nachgewiesene Verbindungen sind kursiv):NaCe _1.67 Cl ₆; K₃CeCl₆, K₂CeCl₅,KCe _1.67 Cl ₆;Rb ₃ CeCl ₆, Rb₂CeCl₅,RbCe ₂ Cl ₇; Cs₃CeCl₆, Cs₂CeCl₅,CsCe ₂ Cl ₇. Die Verbindungen A₂CeCl₅ kristallisieren im K₂PrCl₅-Typ. Die Hochtemperaturmodifikationen der Verbindungen A₃CeCl₆ liegen in der kubischen Elpasolith-Struktur vor. Die hexagonale Elementarzelle des KCe_1.67Cl₆ ist mit der CeCl₃-Struktur verwandt: 0,33 Ce³⁺ sind durch ein K⁺ ersetzt. Die Struktur des CsCe₂Cl₇ kann mit einer hexagonalen Pseudozelle beschrieben werden:a=9,72;c=14,94Å;Z=4; schwache Überstrukturreflexe reduzieren jedoch die Symmetrie. Die thermodynamischen Funktionen für die Reaktionen:n ACl + CeCl₃=A _n CeCl _n+3 (A=K, Rb) wurden durch EMK-Messungen bestimmt. Messungen der Abhängigkeit von e. m. f.E gegenT ergaben die Gibbs-EnthalpienG ^r . Es wurde eine lineare Temperaturabhängigkeit gefunden. Als wichtigstes Resultat ist die Bildung von Elpasoliten (A₃CeCl₆) und von Verbindungen (ACe₂Cl₇) anzusehen.

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ACl/CeCl₃, A . - ( ):NaCe _1.67 Cl ₆; K₃CeCl₆, K₂CeCl₅,KCe _1.67 Cl ₆;Rb ₃ CeCl ₆, Rb₂CeCl₅,RbCe ₂ Cl ₇; Cs₃CeCl₆, Cs₂CeCl₅ CsCe ₂Cl₇. A₂CeCl₅ K₂PrCl₅. A₃CeCl₆ . KCe_1.67Cl₆ CeCl₃, 0,33 Ce³⁺ . CsCe₂Cl₇ a=9,72 Å,c=14,94 Å Z=4. , . n ACl + CeCl₃=A _n CeCl _n+3(A=K, Rb) . . . . . .E , G ^r . ACe₂Cl₇.

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Presented as a poster at the 8th ICTA, Bratislava, 1985.

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This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.     

Studies of immobilized V?P/SiO2 catalysts

It has been revealed by the ESR method that complexes of O ₂ ^– with palladium compounds are formed during the interaction of H₂O₂ with palladium acetate in various solutions.

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H₂O₂ O ₂ ^– .

     

A π-acceptor series for phosphines from51V N.M.R. data on [η5-CpV(CO)3L] complexes

Summary Qualitative molecular orbital considerations of the complexes [⁵-CPV(CO)₃ L] (L = substituted phosphane, SbPh₃, AsPh₃, CN^–) suggest that s' V chemical shift parameters () obtained for these compounds should correlate with the -acceptor abilities of L. Based on observed r-values, the ligands are arranged in sequence of their -acceptor ability, which lies in the order P(OR)₃ > CN^– > PR'₃3 SbPh₃ PPhF₂ > P(i-Bu)₃ P(NR ₂ )₃ > PPh₃ > AsPh₃ Nuclear spin-spin coupling constants J (⁵¹V-³¹ P), line widths H and i.r. data in the (CO) region are also presented.P(OR)₃ = P(OEt)₃, 4-Ethyl-l-phospha-2,6,7-trioxabicyclo[2.2.2]-octane; R = Me, n-Pr; R = Me, Et.     

ESR studies of photoinduced centers on weakly reduced anatase

The paramagnetic centers of reduced anatase (g₁=1.999, g₂=1.984, g₃=1.979) and (g₁=2.046, g₂=2.008), assigned to the stabilization of photoinduced holes near anion vacancies, have been studied. For the reduced oxide a new type of O₂ photoadsorption at h >1 eV due to the generation of only electron surface centers has been discovered.

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, : (g₁=1,999, g₂=1,984, g₃=1,979) (g₁=2,046, g₂=2,008), . O₂ h>1 , .

     

Energetic and kinetic investigation of thermally induced molecular rearrangements of esters of (hydroxymethyl) hydridosilanes by DSC

Silanes of the type R¹R²Si(H)CH₂OEl(O)_xR _y ³ [R=organyl; El=C (x=y=1), S (x=2,y=1), P (x=1y=2)] undergo a thermally induced rearrangement to give silanes of the type R¹R²Si (CH₃)OEl(O)_xR _y ³ . The energetic (reaction enthalpy) and kinetic data (reaction order, enthalpy and entropy of activation) of this reaction were determined by means of differential scanning calorimetry. The results obtained are discussed in terms of mechanistic aspects.

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Zusammenfassung Silane des Typs R¹R²Si(H)CH₂OE10_xR _y ³ mit R=organyl; E1=C (x=y=1), S(x=2, y=1) oder P (x=1,y=2) zeigen eine thermisch induzierte Umlagerung zu Silanen des Typs R¹R²Si(CH₃)OE10_xR _y ³ . Energetische (Reaktionsenthalpie) und kinetische Daten (Reaktionsordnung, Aktivierungsenthalpie und -entropie) dieser Umlagerungsreaktion wurden mittels DSC ermittelt. Die mechanistischen Aspekte der Ergebnisse werden diskutiert.

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R¹R²Si(H)OE1(O)_xR _y ³ , R= , E1=C (x=y=1), S (x=2,y=1), P (x=1,y=2), R¹R²Si(CH₃)OE1(O)_xR _y ³ . ( ) ( , ) . .

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Kinetics and selectivity of the oxidation of alkanes in Cl2?H2O and Cl2?Hg2+?H2O solutions

Relative oxidation rate constants of several normal, iso-, cyclo-and methylcycloalkanes have been measured in Cl₂–H₂O and Cl₂–Hg²⁺–H₂O solutions at 343K. The selectivity of C–H bond dissociation in both systems is the same. HOCl is assumed to be the active species for the two systems.

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Cl₂–H₂O Cl₂–Hg²⁺–H₂O 343 , -,- ; C–H . , HOCl.

     

Simple statistical mechanics of electrolytes with a concentration dependent dielectric constant. Part 1. The pressure equation

We have used an approximation of the Adelman's theory of solutions to take into account the non-pairwise additive effects on the interaction potentials for a real electrolyte solution. As a result, a solute concentration dependent dielectric constant appears. The comparison with experimental data is done by means of the pressure equation. The influence of on solution properties is analyzed in two molality ranges using as a reference simplified models but with the dielectric constant of the pure solvent instead of .     

Effect of pretreatment in benzene hydrogenation on Pt/nylon catalyst

Benzene hydrogenation on Pt/nylon catalyst produced cyclohexene and cyclohexane, in contrast to Pt/SiO₂ on which only cyclohexane was detected. Higher selectivity to cyclohexene was found at higher temperature and after air pretreatment. It is suggested that an oxidized platinum species is responsible for cyclohexene formation.

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Pt/ , Pt/SiO₂, . . , .

     

Electronic state of the active site of A V?P?O/SiO2 catalyst in oxidation of chlorine-containing hydrocarbons

V⁴⁺ ions in slightly associated states are supposed to play the role of V–P–O/SiO₂ active sites. V⁴⁺ ions are reduced to V³⁺ during deactivation of the V–P–O/SiO₂ catalyst.

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V–P–O/SiO₂ V⁴⁺ . V–P–O/SiO₂ V⁴⁺ V³⁺.

     

The influence of CSH phase nuclei on Ca3SiO4Cl2 hydration

The influence of CSH phase nuclei on calcium chlorosilicate hydration has been studied by means of calorimetry, QXRD, DTA and TG methods.

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Zusammenfassung Mittels kalorimetrischen, QXRD-, DTA- und TG-Verfahren wurde der Einfluß von CSH Phasenkörpern auf die Hydratierung von Kalziumchlorosilikat untersucht.

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, , .

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C=CaO, S=SiO₂, H=H₂O     

Thermal and related studies of some basic zirconium salts

Studies of basic zirconium carbonate, oxalate, nitrate and sulphate using TG, DTA and DTG methods, combined with isothermal gaseous product analyses, IR spectroscopy and X-ray diffraction techniques, have shown that the ease of ligand removal from such salts follows the sequence: loosely bound H₂O>CO ₃ ^2– C₂O ₄ ^2– >NO ₃ ^– >OH^– (or tightly bound H₂O)>SO ₄ ^2– .With the exception of the basic sulphate where the high temperature necessary for complete removal of the sulphato groups resulted in direct formation of crystalline monoclinic zirconia, such ligand removal generally led to generation of the cubic crystalline variety.

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Zusammenfassung Auf Grund von TG-, DTA- und DTG-Untersuchungen, verbunden mit einer isothermen Gasprodukteanalyse, sowie IR-spektsoskopischen und Röntgendiffraktionsuntersuchungen von basischen Zirkoniumkarbonaten, -oxalaten, -nitraten und -sulfaten wurde festgestellt, dass die relative Abspaltbarkeit eines Liganden solcher Salze der folgenden Reihenfolge entspricht: locker gebundenes H₂O>CO ₃ ^2– >C₂O ₄ ^2– >NO ₃ ^– >OH^– (bzw. stark gebundenes H₂O)>SO ₄ ^2– . Mit Ausnahme des basischen Sulfates, bei dem zur vollständigen Abspaltung der Sulfatogruppen eioe hohe Temperatur notwendig ist und sich die direkte Bildung von kristallinem, monoklinem Zirkoniumdioxid abspielt, führen solche Ligandenabspaltungen im allgemeinen zu einer kubischen Kristallmodifikation.

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, , , , , , , , : ₂> ₃ ^2– C₂Ol ₄ ^2– > N ₃ ^– > ^– — H₂O>SO ₄ ^2– . , , .

     

Influence of sodium on the catalytic properties of bismuth-molybdenum oxide catalysts

In the ammoxidation of propylene, the presence of a normal NaBi(MoO₄)₂ phase in bismuth molybdenum oxide catalysts decreases the acrylonitrile yield due to its oxidation

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NaBi(MoO₄)₂ -- .

     

Thermische Zersetzung von Blei(II)-Acetat

Zusammenfassung Die Zersetzung von Pb(CH₃COO)₃ · 3 H₃O wurde im Bereich von Raumtemperatur bis 450° unter N₃ mittels TG, DTA verfolgt und die Produkte wurden analytisch charakterisiert. PbO ist das hauptsächliche feste Endprodukt, neben dem im wesentlichen nur Pb entsteht. Als feste Zwischenprodukte wurden neben Pb(CH₃COO)₃ die basischen Acetate Pb(CH₃COO)₂ · PbO und Pb(CH₃COO)₂ · 2 PbO gefunden und durch Röntgenpulveraufnahmen identifiziert; diese basischen Acetate wurden durch isotherme Zersetzung bei 240 bzw. 305° dargestellt. Unter den durch GC und MS erfaßten und quantitativ bestimmten flüchtigen Zersetzungsprodukten sind CO₂ und Aceton Hauptbestandteile. Verschiedene Bildungsweisen der übrigen Produkte, CH₃COOH, (CH₃CO)₂O, Acetylaceton und des Zwischenproduktes Keten werden aufgezeigt.

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The decomposition of Pb(CH₃COO)₃ · 3 H₂O under N₂ has been studied by TG and DTA between room temperature and 450° and the products have been characterized analytically. PbO is the main solid product, besides which essentially only Pb is produced. As solid intermediates, aside from Pb(CH₃COO)₃ the basic acetates Pb(CH₃COO)₂ · PbO and Pb(CH₃COO)₂ · 2 PbO have been found and identified via their X-ray powder diagrams; these basic acetates have been prepared by isothermal decomposition at 240 and 305°, respectively. Among the volatile decomposition products analyzed by GC and MS and determined quantitatively, CO₂ and acetone are the main products. Different routes for the formation of the other products, CH₃COOH, (CH₃CO)₂O, acetylacetone and the intermediate ketene are shown.

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Résumé On a suivi, par TG et ATD sous N₂, dans l'intervalle de températures allant de l'ambiante jusqu'à 450°, la décomposition de Pb(CH₃COO)₂ · 3 H₂O dont on a caractérisé les produits par des méthodes analytiques. PbO est le principal produit final solide, en dehors duquel il ne se forme essentiellement que du Pb. Comme produits intermédiaires solides, on a trouvé, à part Pb(CH₃COO)₂, les acétates basiques Pb(CH₃COO)₃. PbO et Pb(CH₃COO)₂ · · 2 PbO qui ont été identifiés par analyse de poudres aux rayons X. Ces acétates basiques se sont formés, par décomposition isotherme, respectivement à 240 et à 305°. Parmi les produits de décomposition volatils décelés par GC et MS et dosés par des méthodes quantitatives, CO₃ et l'acétone sont les composants principaux. On montre les différents modes de formation des autres produits, comme CH₃COOH, (CH₃CO)₃O, l'acétylacétone et le cétène formé transitoirement.

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Pb(CH₃COO)₂. 3₂O 450°. . PbO , , . , Pb(CH₃COO)₂, Pb(CH₃COO)₂. PbO Pb(CH₃COO)₂. 2PbO, . , , 240 305°. , -, CO₂ . , CH₃COOH, (CH₃CO)₂O, .

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Dem Fonds der Chemischen Industrie danken wir für finanzielle Unterstützung.     

Influence of Pr ions on the properties of Pd/SiO2 and Pt/SiO2 catalysts in oxidation of n-butane

It has been established that (M_VIII+Pr)/SiO₂ catalysts (M_VIII=Pd or Pt) obtained from organometallic precursors, have increased the dispersity of Pt, but their TN in deep oxidation of n-butane is by 3–6 times lower than that of unmodified M_VIII/SiO₂.

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(M_VIII+Pr)/SiO₂ ( M_VIII=Pd, Pt), , Pt, 3–6 - M_VIII/SiO₂.

     

Contribution of air oxygen to photooxidation of alkanes by vanadium(V) and chromium(VI) oxocomplexes

In photochemical oxygenation of cyclohexane by KVO₃–CF₃COOH or K₂Cr₂O₇–Bu₄NBr–H₂O–CH₂Cl₂ in air the source of oxygen atoms in the product cyclohexanol and cyclohexanone is air dioxygen rather than a metal oxo-complex. In the absence of dioxygen the products of alkane oxygenation are not formed in either of the above systems. At pH=3, Cr(VI) does oxidize cyclohexane to cyclohexanol even in argon atmosphere.

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KVO₃–CF₃COOH K₂Cr₂O₇–Bu₄NBr–H₂O–CH₂Cl₂ , . . , pH=3, Cr(VI) .

     

Temperature programmed desorption (TPD) of carbon monoxide from cobalt surfaces

Three different binding states of CO on cobalt surfaces have been identified by TPD studies. The energetics of these adsorption states and their relevance in Fischer-Tropsch synthesis are considered.

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CO - . -.