Interaction of ammonia with the surface of Cr?Mo and Cr?Mo?Te oxide catalysts

The adsorption of NH₃ on Cr–Mo and Cr–Mo–Te catalysts has been investigated by IR spectroscopy. It is shown that there are both electron acceptor and proton donor acid centers on the surface of these catalysts. The introduction of tellurium into a Cr–Mo catalyst decreases adsorption on the electron acceptor centers.

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NH₃ Cr–Mo Cr–Mo–Te . , -, - . Cr–Mo .

     

Ammonia decomposition on Ir and Pt wires

The rates of ammonia decomposition on polycrystalline Ir and Pd wires were measured at temperatures between 900 and 2000 K and at pressures between 50 and 770 Torr. Rates on Ir were fitted with a Langmuir-Hinshelwood unimolecular reaction rate expression. Rates on Pd could not be fitted with a rate expression, although activation energies were obtained.

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Ir Pd 900–2000 50–770 . Ir --. Pd . .

     

Relation between the catalytic and acidic properties of zeolite catalysts

Influence of the strength and concentration of non protic centers on the catalytic activity of metal-zeolite catalysts in isomerization of n-butane has been studied. A relationship between the specific activity and the center strength is suggested.

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-. , .

     

Zur thermoanalytischen charakterisierung von amorphen synthetischen,organisch nachbehandelten Kieselsäureprodukten

Zusammenfassung Für eine anwendungstechnische Beurteilung von amorphen synthetischen Kieselsäuren sind neben der Dispersität und Morphologie insbesondere auch strukturelle Eigenschaften bedeutsam. Die vorliegende Veröffentlichung zeigt, daß auf der Basis von thermoanalytischen Untersuchungen eine Unterscheidung unterschiedlicher Kieselsäuretypen möglich ist. Aus den TG- und DTA-Ergebnissen sind dabei Aussagen über die Art und Menge des adsorptiv bzw. chemisch gebundenen Wassers, sowie die oxydative Zersetzung des organischen Beschichtungsmittels abzuleiten.

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Besides dispersity and morphology, structural characteristics are of importance for the estimation of amorphous synthetic silicic acids with regard to their application. The present publication shows that it is possible to identify the different silicic acid types on the basis of thermoanalytical studies. The TG and DTA results provide information on the type and quantity of adsorbed or chemically bound water, and on the oxidative decomposition of the organic coating agent.

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, . . , .

     

Thermal analysis of Australian coals—A short review

It is evident that thermal analysis studies of Australian coals are of primary significance in the rationalisation of the various physical and chemical processes inherent in energy generation from these fossil fuels. To data, considerable such data has been accumulated correlating combustion efficiency with the coal primary structure, surface phenomena, included metal ions, volatile matter release profiles, particle size and corresponding char properties. The kinetics of these complex processes are now also modelled.

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Zusammenfassung Für die Rationalisierung der physikalischen und chemischen Prozesse bei der Energiegewinnung aus australischer Kohle sind thermoanalytische Untersuchungen dieser fossilen Rohstoffe von erstrangiger Bedeutung. Es wurde eine bedeutende Menge von Angaben gesammelt, die eine Beziehung zwischen dem Verbrennungsgrad und der Primärstruktur der Kohle, Oberflächenerscheinungen, enthaltenen Metallionen, des Emissionsprofiles flüchtiger Verbindungen, der Partikelgröße und der entsprechenden Halbkokseigenschaften herstellen. Die Kinetik dieser komplexen Vorgänge wurde nun auch modelliert.

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, , . , , , , , . .

     

Infrared spectroscopic study of the interaction between furan and a vanadium oxide catalyst

The results of the infrared spectroscopic study of the interaction between furan and a vanadium oxide catalyst permit to suppose that the intermediates in furan oxidation are surface succinyl oxide and maleates.

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, , , - .

     

Alumina as a nickel catalysts support for steam reforming of hydrocarbons

The coking resistance of six alumina supported nickel catalysts in n-butane steam reforming mainly depends on the average size of nickel crystallites. Thus, by using suitable preparative methods, it is possible to produce good, coking resistant nickel catalysts even with Al₂O₃ support.

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Al₂O₃ -, , . . ., , - Al₂O₃.

     

Benzene hydrogenation on platinum-tin bimetallic catalysts

Various catalysts were prepared by impregnating a commercial alumina with solutions containing the complex dichlorobis(trichlorostannato)platinate (II). [Pt Cl₂ (SnCl₃)₂]^2–. After reduction, 1–20 fold variations in the catalytic activity in benzene hydrogenation were observed in direct proportion to the stability of the complex in the impregnating solution.

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, — - ( ()-(II) [PtCl₂(SnCl₃)₂]^–2. , 1–20 . .

     

Catalytic deactivation dynamics of zeolites in multicycle processes

Catalytic deactivation dynamics of zeolites in multicycle processes has been calculated. It has been revealed that in naphthalene sorption on NaX zeolites surface deactivation is predominant with its similarity criterion close to unity and a high fraction of deactivation. Calculated data for several multicycle processes are given.

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. , NaX . .

     

Unimolecular decomposition of CF3OF-calculation by reduced Kassel integral in factorized form

The fall-off curves were calculated for the unimolecular decomposition of the trifluoromethyl hypofluorite at 475.8, 496.9 and 507.3 K by means of the Reduced Kassel Integral in Factorized Form.

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475,8,496,9 507,3 .

     

A mechanistic study of cycloaddition of carbon dioxide to propyne over supported Rh4 and Fex Rhy carbonyl cluster derived catalysts

CO₂ undergoes cycloaddition to propyne on a cationic rhodium site with the assistance of O^2–/OH^– of support or iron oxide over Rh₄ and Fex Rhy carbonyl clusterderived catalysts.¹³CO₁₂ labeling and FTIR studies suggest that monodentate carbonate formed on the catalyst surface is most likely a key species to offer an active CO₂ to be converted into a carbonyl intermediate prior to the product 4,6-dimethyl-2-pyrone.

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CO₂ O^2–/OH Rh₄ Fex Rhy. ¹³CO₂ , CO₂ , 4,6--2-.

     

Study of the thermal dissociation of processes of nickel(II) and cobalt(II) β-diketonate adducts

Thermal dissociation processes of-diketonate adducts with the composition ML₂ · 2B (L = acetylacetone and its substituted derivatives;M = Ni, Co;B = H₂O, BuNH₂CH₃OH, Py, NH₃) were investigated. Kinetics of dissociation were studied in a flow reactor. For dehydration processes a compensation relationship is observed (lgA=E+b), demonstrating analogous mechanisms.A semi-quantitative series of the thermodynamic stabilities of the dihydrates is obtained from experimental data at quasi-equilibrium conditions (Q-derivatograph).

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Zusammenfassung Es wurden die thermischen Dissoziationsprozesse von-Diketonataddukten der Zusammensetzung ML₂ · 2B (L=Azetylazeton und dessen substituierte Abkömmlinge;M=Ni, Co;B=H₂O, BuNH₂, CH₃OH, Py, NH₃) untersucht. Die Kinetik der Dissoziation wurde in einem Flowreaktor untersucht. Als Beweis für die Ähnlichkeit der Mechanismen der Dehydrierungsprozesse konnte eine lgA=aE+b Beziehung festgestellt werden. Von unter Quasi-Gleichgewichtsbedingungen gewonnenen Daten konnte eine semiquantitative Serie der thermodynamischen Stabilitäten der Dihydrate abgeleitet werden (Q-Derivatograph).

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- ML₂·2B (L = ;M= Ni, Co;B=H₂O, BuNH₂, CH₃OH, Py, NH₃). ; (lgA=aEs+b) . (Q- ).

     

Catalytic oxidation of cycloalkane heteroanalogs as a way to polyfunctional compounds

Liquid phase oxidation of cycloalkane diheteroanalogs catalyzed by compounds of Cu²⁺, Ni²⁺, Co²⁺, Cr³⁺, Fe³⁺ has been studied. It has been established that these catalysts can be applied to intensify, oxidize and increase the selectivity of this process.

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: Cu², Ni²⁺, Co²⁺, Cr³⁺, Fe³⁺. .

     

Hydrogenation of nitric oxide on platinum black in acidic solution

By comparison of the catalytic hydrogenation and electrochemical reduction of NO on platinum black catalysts it has been shown that the hydrogenation of NO to ammonia and to hydroxylamine occurs in the diffusion controlled region only.

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NO , NO .

     

Ba(OH)2 as catalyst in organic reactions, III. The structure of adsorbed ylids

The nature of adsorbed sulfonium and phosphonate ylids on a new barium hydroxide catalyst (C-200) is analyzed by IR. The catalytic activity of C-200 in solid-liquid phase transfer conditions is explained by these IR studies.

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(C-200) . C-200 - .

     

Nature of intermediates in the synthesis of hydrocarbons from methanol

According to the GC-MS analysis of the composition of liquid hydrocarbons obtained in methanol conversion on ZSM-5 zeolites and the selectivity of cyclohexene conversion on these catalysts, the sequence of the aromatization reaction steps is discussed.

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-- , ZSM-5, .

     

Influence of ammonia on propylene oxidation on tin-antimony and bismuth-antimony catalysts

The influence of ammonia on the direction of the oxidative transformations of propylene has been studied. Ammonia has been shown to block the surface oxygen of antimony catalysts. As a result, an increase in the selectivity with respect to the products of partial oxidation is observed.

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. , , .

     

Deactivation of reforming catalysts. Coke formation on metallic and acidic centers

To check coke formation on metallic (Pt^o) and acidic (Al₃₊) centers of Pt/Al₂O₃ and Pt–Sn/Al₂O₃ catalysts, the application of IR spectroscopy of adsorbed CO for detecting Pt^o–CO (2070 cm^–1) and Al³⁺–CO (2190 cm^–1) bonds has been substantiated. Decrease in the number of active Pt^o and Al³⁺ centers is shown to correlate with that in the dehydrogenation rate of cyclohexane and in the isomerization rate of heptane, respectively.

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(Pt^o) (Al³⁺) Pt/Al₂O₃ Pt–Sn/Al₂O₃ - CO Pt^o–CO (2070 ^–1) Al³⁺–CO (2190 ^–1). , Pt^o , Al³⁺- .

     

Determination of the surface hydroxy groups on alumina and silica-alumina catalysts by dimethylzinc

The earlier proposed pulse flow method for the determination of surface OH groups based on the reaction of gaseous dimethylzinc tetrahydrofuranate with active hydrogen was applied to alumina and silica-alumina catalysts. The concentrations of OH groups found by this method are in a good agreement with the published data, obtained by deuterium exchange and gravimetry.

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, , OH, , - . OH, , , .