Adsorbed oxygen species formed by reaction with N2O on CaO

A considerable amount of adsorbed oxygen species is formed by the reaction of N₂O on CaO. It is suggested that these adsorbed species were practically held on 5-coordinated sites.

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- N₂O CaO. , 5-- .

     

The decomposition of iron(III) sulfate in air

The decomposition of initially hydrated powders of iron(III) sulfate was carried out in air over the temperature range 823–923 K. The decomposition process, which gave Fe₂O₃ as a solid product, was seen to have zero-order kinetics and an activation energy of 219 kJ·mol^–1. The nature of the product and the kinetics of decomposition were the same for samples decomposed in air and in argon. Sulfate samples with additives of FeS and Fe₂O₃ were also decomposed under similar conditions and the results confirmed the zero-order kinetics (for the case of the Fe₂O₃ additives) and the lack of effect of FeS on the decomposition of iron(III) sulfate.

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Zusammenfassung Anfänglich hydratiertes Eisen(III)-sulfatpulver wurde in Luft im Temperaturbereich 823–923 K zersetzt. Für die Reaktionsordnung des Zersetzungsprozesses, der als Endprodukt festes Fe₂O₃ lieferte, wurde Null und für die Aktivierungsenergie 219 kJ·mol^–1 ermittelt. Die Art des Produktes und der Kinetik der Zersetzung war in Luft und Argon gleich. Unter den gleichen Bedingungen wurden auch Sulfatproben mit Zusätzen von FeS und Fe₂O₃ zersetzt. Die Ergebnisse bekräftigen sowohl die nullte Reaktionsordnung (im Falle von Fe₂O₃ Zusätzen) als auch einen fehlenden Einfluß von FeS auf die Zersetzung von Eisen(III)-sulfat.

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823–923 . , , , 219 · ^–1. . FeS Fe₂O₃ . ( Fe₂O₃) - .

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This work was supported by a grant from the U.S. Department of Energy, Office of Basic Energy Sciences. The authors gratefully acknowledge this support.     

Thermal decomposition of metal polyacrylates

Results of thermal and pyrolysis-GC/MS analyses of Na, Ca and Mg polyacrylates are presented. It was confirmed that the main decomposition reactions of the Na salt take place in the temperature range 420 – 470 and those of the other two polymers in the range 450–490. It was found that the solid residue after decomposition was the metal carbonate or oxide, while the volatile products consisted of H₂, CO, CO₂, saturated and unsaturated hydrocarbons (including cycloolefins and aromatic hydrocarbons) and aliphatic ketones. This suggests that the thermal decomposition of the metal polyacrylates proceeds via side-chain splitting and breaking of the main chain of the polymer, without retropolymerization.

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Zusammenfassung Die Ergebnisse der Thermo- und Pyrolyse-GC/MS-analysen von Na-, Ca- und Mg-Polyacrylaten werden beschrieben. Es wurde bestÄtigt, dass die Hauptzersetzungsreaktionen des Natriumsalzes im Temperaturbereich von 420 bis 470, jene der anderen zwei Polymeren im Bereich von 450 bis 490 ablaufen. Es wurde nach der Zersetzung ein fester Rückstand von Metallkarbonat oder -oxid gefunden, wÄhrend die flüchtigen Produkte aus N₂, CO, CO₂, gesÄttigten und ungesÄttigten Kohlenwasserstoffen (darunter Zykloolefinen und aromatischen Kohlenwasserstoffen) und aliphatischen Ketonen bestanden. Dies lÄsst darauf schliessen, dass sich die thermische Zersetzung der Metallpolyacrylate über die Abspaltung der Seitenkette und der Spaltung der Hauptkette des Polymers ohne Retropolymerisation vollzieht.

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Résumé On présente les résultats des analyses thermiques et des produits de décomposition pyrolytique par chromatographie en phase gazeuse et spectrométrie de masse (GC/MS) des polyacrylates de Na, Ca et Mg. On confirme que la réaction de décomposition principale du sel de sodium a lieu entre 420 et 470 et celle des deux autres polymères entre 450 et 490. On trouve que le résidu solide après décomposition est le carbonate ou l'oxyde du métal, tandis que les produits volatils consistent en N₂, CO, CO₂, en hydrocarbures saturés et non-saturés (y compris les cyclooléfines et hydrocarbures aromatiques) et en cétones aliphatiques. Cela permet de supposer que la décomposition thermique des polyacrylates métalliques s'effectue par coupure de la chaÎne latérale et par rupture de la chaÎne principale du polymère, sans rétropolymérisation.

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-- -- Na, Ca Mg. , 420–470, — 450–490. , . H₂, CO, CO₂, , , . , .

     

Effect of the solvent on selective hydrogenation of 6, 10-dimethylundeca-3,5,9-trien-2-one

Reaction mechanism for selective hydrogenation of pseudo-ionon on Raney-Ni in the presence of n- and iso-alcohols has been studied. From the analysis of ESR spectra, the dependence of selectivity on the solvent is concluded.

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- Ni- . .

     

Hydrocarbon synthesis from methanol on erionite and mordenite catalysts synthesized in the presence of B3+, Ga3+ or Fe3+

Selectivity of erionite and mordenite type aluminosilicates synthesized in the presence of B³⁺, Ga³⁺ or Fe³⁺ has been studied in methanol conversion to hydrocarbons. The olefin to paraffin ratio in the product is proportional to the Al₂O₃ content of the zeolites.

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, B³⁺, Ga³⁺ Fe³⁺. , / Al₂O₃ .

     

Rate constants for the interaction of trifluoromethyl radicals with oxygen and fluorine

The absolute rate constants for the reactions of trifluoromethyl radicals with fluorine (I) and oxygen (II), k₁=(3.1±2.1)×10^–11 exp [–(4600±300)/RT] (cm³/molec sec) and k₂=(2.5±1.7)×10^–11 exp [–(2100±300)/RT] (cm³/molec sec). have been determined from the relative rate constants for the reactions of trifluoromethyl radicals with oxygen and chlorine (IV):k₂/k₄=(3.6±1.6)exp [(1600±300)/RT] (T=269–356 K) obtained by the photolysis of a mixture of hexafluoroacetone (HFA) with O₂ and Cl₂.

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(I) (II) k₁=(3,1±2,1)·10^–11 exp[–(4600±300)/RT] (cm³/. ), k₂=(2,5±1,7)·10^–11 exp[–(2100±300)/RT] (cm³/. ) O₂ Cl₂ (І) k₂/k₄=(3,6±1,6)exp[(1600±300)/RT](T=296–356° K).

     

IR study of isopropanol adsorption on haematite

The IR study shows that isopropanol interacts with haematite at IR beam temperature both as a physisorbed form, hydrogen bonded to basic sites of the surface, and as isopropoxide groups. At 423 K a decomposition of isopropoxide groups produces enolate anions of acetone.

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, , - , . 150 °C .

     

Molecular oxidic phases of diluted silica supported vanadia

Different surface phases of silica supported vanadia catalysts have been characterized by static adsorption, reduction, and reoxidation experiments under vacuum conditions. The obvious mobility of vanadium involved in some preparation steps gives rise to a diversification of initial precursor phases as a function of pretreatment conditions and SiOH concentration.

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SiO₂ , . , , SiOH.

     

CNDO study of the properties of the OH group

Using the CNDO method, a number of hydroxy-containing systems were calculated. The results are compared with IR spectroscopic data on the frequencies and acidity of surface OH groups and their dependence on the electronegativity of the atom to which the OH group is bonded.

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. - OH- , .

     

Studies on the thermal decompositions of As-triazine derivatives and their compounds with metal ions

The thermal decompositions of the new complex salts of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with 5,6-diethoxyearbonylmethyl-3-seleno-1,2,4-triazine (HSeTEK) and 5,6-diethoxycarbonylmethyl-3-thio-1,2,4-triazine (HTTEK) were investigated on the basis of the respective thermal curves. The thermoanalytical investigations indicate that HSeTEK, HTTEK, and their complexes with metal ions all undergo three-stage changes as the temperature is raised. The stages of pyrolysis established from the thermal data were compared, and the rates and stages of pyrolysis were related to the structures of the compounds.

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Zusammenfassung Die thermische Zersetzung der neuen Komplexsalze von Mn(II), Co(II), Ni(II) und Cu(II) mit 5,6-Diäthoxycarbonylmethyl-3-seleno-1,2,4-triazin (HSeTEK) und 5,6-Diäthoxycarbonylmethyl-3-thio-1,2,4-triazin (HTTEK) wurden auf der Grundlage der entsprechenden thermischen Kurven untersucht. Die thermoanalytischen Untersuchungen zeigen, daß HSeTEK, HTTEK und deren mit Metallionen gebildeten Komplexe bei Temperaturerhöhung einer jeweils dreistufigen Umwandlung unterliegen. Die auf der Basis der thermischen Daten festgestellten Pyrolysestufen wurden verglichen und Geschwindigkeit und Abschnitte der Pyrolyse mittels der Struktur der Verbindungen erläutert.

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, , 5,6- -3--1,2,4- 5,6 5,6 -3--1,2,4-. , . . - .

     

An investigation of the effects of pressure and temperature on the vapourization characteristics of crude oil using first approximation thermal analysis

This study investigates the effect of pressure and temperature on crude oil vaporization using first approximation thermal analysis. Developed here is a technique for quantifying the vaporization of fractions of a crude oil using an experimentally obtained thermogravimetric (TG) curve of the crude.The initial data utilized is the weight loss versus temperature values at atmospheric pressure, together with physical property data and equilibrium constant,k values.The results of this study allow the estimation of the volume of oil distilled underground when steam is injected into oil reservoirs at varying pressures and temperatures to recover crude oil.

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Zusammenfassung Diese Studie untersucht in erster Näherung mittels Thermoanalyse den Einfluß von Temperatur und Druck auf das Verdampfen von Rohöl. Es wird eine Methode zur quantitativen Bestimmung des Verdampfens von Rohölfraktionen entwickelt, die auf einer experimentell ermittelten thermogravimetrischen (TG) Kurve des Rohstoffes basiert. Als Anfangswerte werden die von der Temperatur abhängige Massenabnahme (unter Normaldruck) zusmmmen mit physikalischen Eigenschaften und der Gleichgewichtskonstantek verwendet. Die Ergebnisse dieser Untersuchung erlauben das Abschätzen des Umfanges des Öldestillationsrückstandes, insofern zur Gewinnung des Rohols Dampf in die Ölreservoir injeziert wird.

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, . , . , , . .

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o-Xylene hydrogenation on Ru, Pt, Rh and Pd supported catalysts: Dispersity effect on selectivity

Selectivity to 1,2-cis- and 1,2-trans-dimethylcyclohexane products was studied in o-xylene hydrogenation over Pt, Pd, Rh and Ru supported catalysts. The results show that selectivity is sensitive to particle size.

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1,2-- 1,2-- - Pt, Pd, Rh Ru. .

     

Response studies of the mechanism of o-xylene oxidation over a vanadium-titanium oxide catalyst

A response method has been used to study the mechanism of o-xylene oxidation over a vanadium-titanium oxide catalyst. The products of partial and destructive oxidation are shown to be formed under the influence of molecular oxygen on the surface intermediates produced by the interaction between o-xylene and oxidized surface sites.

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- . , , - .

     

Preparation of mixed-ligand complexes of nickel via thermal decomposition

If heated to around 270° in argon, [Ni(HSal)₂] (H₂Sal=salicylic acid) gives off gaseous H₂Sal and forms [NiSal], which reacts with monoprotic ligands HL (e.g. 8-hydroxyquinoline) to form mixed-ligand complexes [NiHSalL], or with diprotic ligands H₂L' (e.g. quadratic acid) to form dinuclear complexes [HSalNiL'NiHSal].

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Zusammenfassung Die Komplexverbindung [Ni(HSal)₂] spaltet beim Erhitzen auf 270 °C in Argon Salicylsäure ab und liefert [NiSal], das mit Monoproton-Liganden HL (z. B. 8-Hydroxychinolin) zu Gemischtliganden-Komplexen [NiHSalL], mit Zweiprotonen-Liganden H₂L' (z. B. Quadratsäure) dagegen Zweikernkomplexe [HSalNiL'NiHSal] bildet.

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[Ni(HSal)₂] 270°, [NiSal], HL (., 8-) [NiHSalL] H₂L [HSalNiLNiHSal].

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The preparative and thermoanalytical part of this work was performed by C. Gribi, D. Noukakis and M. Piccand, who also drew the Figures.

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This research was supported by the Swiss National Science Fundation, grant No. 2.053-0.99.     

ESR studies of free radicals formed during hydrogen and methane oxidation in contact with chalcopyrite

ESR studies have revealed that in the complex conjugated transformations of chalcopyrite under the effect of gasphase chain oxidation of methane and hydrogen, free radicals are formed. These radicals are sulfur-containing paramagnetic particles.

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. , .

     

FTIR investigation of the structure of vanadium oxides on ZrO2 and oxidation of toluene on it

The oxidation of toluene has been studied on V₂O₅/ZrO₂ by both FTIR spectroscopy and pulse method. The results suggest that Lewis-acidic sites play a significant role in the formation of benzaldehyde from toluene.

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V₂O₅/ZrO₂ - , . .

     

Low temperature oxidation of isobutene on heterogeneous photoimmobilized copper-containing catalysts

A new photoimmobilization method to synthesize heterogeneous metal complex catalysts for low temperature oxidation of isobutene to methacrolein is suggested. The process selectivity is 100%.

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- -- . - 100%.

     

Double bond migration of olefins on deuterated and chlorinated Al2O3 catalysts

Isomerization of normal and vinyl substituted olefins has been studied on pure and chlorinated alumina catalysts. The surface OH groups were deuterated before isomerization experiments. No deuterium was observed in product molecules either in the case of olefins with increased proton affinity (2-methyl-1-butene) or on the chlorinated catalysts with increased acidity.

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. OH . (2--1-) .

     

Effect of Sn addition on the catalytic properties of the metallic phase in Pt?Sn/Al2O3 catalysts

Platinum-tin/alumina supported catalysts have been studied. The TPR results show an assisted reduction of tin by platinum. The effect of alloying in cyclohexane dehydrogenation, o-xylene hydrogenation and cyclopentane hydrogenolysis is discussed.

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- , . . , - .

     

Investigation of n-hexane dehydrocyclization over supported Pt catalyst modified by adsorbed rhenium

A -Al₂O₃ supported Re–Pt bimetallic catalyst prepared by electrochemical adsorption has been studied in n-hexane dehydrocyclization, using the slug-pulse method. The activity of the Re–Pt/Al₂O₃ catalyst treated only in hydrogen was low, but markedly increased by a calcination step before hydrogen treatment. The modified catalyst showed higher activity and increased selectivities for benzene and iso-hexanes than the base Pt/Al₂O₃ catalyst.

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Pd/Pt, -Al₂O₃, -. Pd–Pt/Al₂O₃, , , . Pd–Pt/Al₂O₃ , Pt/Al₂O₃.