Peculiarities of propylene metathesis over catalysts prepared by anchoring of Mo(V) oxalate to γ-Al2O3

Propylene metathesis over catalysts prepared by coordination of Mo(V) oxalate to -Al₂O₃ has been studied.

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, (V) -Al₂O₃.

     

Reactivity of Cl(2P1/2) atoms towards CH3F

The photochlorination of methyl fluoride has been studied at low pressures. Excited (²P_1/2) chlorine atoms have been found to participate in the reaction. The ratio of the excited and ground state rate constants has been estimated at room temperature.

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. (²P_1/2) . .

     

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), .

     

Influence of molecular nitrogen and irradiation temperature on radiolysis of N2O?Al2O3 system

Molecular nitrogen and irradiation temperature are shown to affect the radiationchemical yield of O _st ^– in the radiolysis of N₂O adsorbed on alumina with large surface areas and to exert no influence in the case of small surface areas of Al₂O₃.

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, - O _st ^– N₂O, Al₂O₃ .

     

Use of Pd/Sepiolite systems as hydrogenation catalysts I. Hydrogenolysis of N-blocked amino acids and dipeptides with molecular hydrogen

In this work we have assessed the use of sepiolites from Vallecas (Madrid, Spain) as supports of Pd catalysts applicable to the liquid-phase unblocking of amino acids and dipeptides protected by a benzyloxycarbonyl group (Z) with gaseous hydrogen. The sepiolites used have been compared with other supports employed by our team. We have also discussed the influence of the type of amino acid or dipeptide, the catalytic support and the precursor Pd salt on the unblocking rate.

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(, ) Pd , , (Z), . , . , Pd .

     

V2O5/TiO2 oxidation catalysts, IV. Adsorption of acrolein on sodium-containing systems

Adsorption of acrolein on vanadia/titania catalysts fits a polymerization kinetics if Na–V compounds are not present or the vanadium content is lower than that corresponding to formation of a monolayer of vanadia on the titania support.

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, Na–V .

     

Hydration of acetylene on Cd2+ exchanged zeolites

The reaction takes place on Cd-containing Lewis sites, whereas the irreversible adsorption and condensation of product acetaldehyde on acidic OH groups of Cd-X, FAU catalyst results in deactivation. Preadsorbed ammonia moderates the deactivation, because it reacts with acetylene, and pyridine homologues are formed which block the accessible OH groups. Since in divalent cationic forms of clinoptilolite no OH groups are generated, Cd-clinoptilolite proved to be a catalyst of permanent activity.

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, Cd, — OH FAU, Cd-X. , .. , OH . OH, Cd- .

     

Heterogeneous-homogeneous decomposition of HNO3

In contrast to ZSM zeolites impregnated with V⁵⁺ salts, catalysts prepared by adding V³⁺ salts during zeolite synthesis exhibited (even when transformed into cristobalite by oxidative activation) higher selectivity to furane in the oxidation of butadiene. Non-oxidative activation preserved the zeolitic structure and increased both the total activity and the selectivity to furane.

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ZSM, V⁵⁺, V³⁺ ( ) . , , .

     

Influence of fluorine-modified SiO2-surfaces on the properties of V2O5/SiO2 catalysts

The preparation of vanadium catalysts is described using fluorine modified Aerosil as support. It is shown that modification with fluorine changes the concentration and topology of the surface silanol groups and, as a consequence, the catalytic properties.

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, , . , , , .

     

Computation in kinetics, III. A new method for kinetic model search based on simultaneous regression estimation of rate constants, stoichiometry and/or reaction order

Modified samples of natural mordenites have been found to catalyze the oxidative condensation of methane to yield ethane and ethylene. The selectivity towards C₂ hydrocarbons increases, whereas the acidity of zeolites falls.

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, . C₂ .

     

Infrared spectroscopic study of CO adsorption on supported bimetallic Pt?Pb/SiO2 catalysts

With increasing Pb content, the IR band of linearly adsorbed CO is significantly shifted to lower frequencies. The greatest influence of lead is observed up to 15% Pb. An X-ray diffraction study indicates the formation of Pt_5–7–Pb and Pt–Pb alloys for bimetallic catalysts with a Pt/Pt+Pb ratio equal to 30%.

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Pb CO . 15% Pb. 30% , , Pt–Pb Pt_5–7–Pb.

     

Studies of fast relaxations in SO2 oxidation on active components of vanadium catalysts

Studies of the fast relaxations of the reaction mixture composition in the SO₂ oxidation on V₂O₅–K₂S₂C₇ have revealed O₂ and SO₂ evolution from the catalyst during the initial period of the reaction. An associative mechanism for the interaction of molecular oxygen with the molten active vanadium complex is suggested.

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є SO₂. . .

     

Some peculiarities in ESR spectra of titanium complexes in catalysts for isoprene polymerization in excess A1R3

It has been established that at low temperatures of TiCl₄+AOC catalyst preparation in solution (with Ti/Al1/15), ESR spectra exhibit rhombic anisotropy of the g-factor. Experiments with the sample having 61 % concentration of⁴⁷Ti isotopes suggest the formation of associates of Ti³⁺ with magnetic ordering, apparently due to the Jahn-Teller cooperative effect.

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TiCl₄+ AOC ( Ti/Al1/15) g-. ⁴⁷Ti (61%) Ti³⁺ , , -.

     

Calorimetric studies of adsorptive properties of metallic carbides and nitrides of transition elements. Adsorption of H2, CO and O2 on titanium nitrides

Adsorption heats of hydrogen, oxygen and carbon monoxide on titanium nitrides have been measured calorimetrically in the temperature range from 473 to 673 K. With increasing Me/N ratio, the adsorption heat of oxygen grows.

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, 473–673 . Me/N.

     

Hydrodenitrogenation activity of sulfided catalysts

Activities of hydrodenitrogenation catalysts were compared using a batch mode autoclave reactor. The hydrodenitrogenation of carbazole, a model coal nitrogen compound, was the reaction studied. The highest activity and the highest rate constant for carbazole and total nitrogen removal were found in the case of NiMo/Al₂O₃ catalyst.

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. , . , NiMo/Al₂O₃.

     

V2O5/TiO2 oxidation catalysts, III. Oxidation of CO on pure and sodium-doped systems

The activity of vanadia/titania catalysts in CO oxidation has been tested and found to be of the same order as that observed for unsupported vanadia; the simultaneous presence of vanadium-sodium compounds cancels the activity, probably because of the elimination of labile V=0 species at surface defects.

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V₂O₅/TiO₂ CO, V₂O₅; - , , V=0 .

     

Mutual effect of benzene and maleic acid anhydride in their adsorption on V2O5?MoO3 catalysts

TPD studies have revealed that benzene and maleic anhydride are adsorbed on different active sites of the V₂O₅–MoO₃ catalyst.

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, - .

     

Decomposition of dimethyl sulfide in the presence of Al2O3, and catalyst deactivation

The catalytic decomposition of dimethyl sulfide has been studied over the temperature range of 400–500 °C. The main reaction products are methylmercaptane, H₂S and methane. Catalyst deactivation is due to its coking during the reaction. The possibility of oxidative catalyst regeneration at 550 °C has been shown.

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400–500°C. , . , . 550°C.

     

Effect of rutile/anatase ratio on catalytic properties of Co?TiO2 catalysts for fischer-tropsch synthesis

CO hydrogenation on Co–TiO₂ catalysts with similar cobalt dispersity and rutile amount within f=0–1·0 in a rutile-anatase mixture has been studied. The highest activity and selectivity to liquid hydrocarbons is observed for the catalyst with f=0.7.

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CO CO–TiO₂, , , f, - . , f=0,7.

     

Modifying action of carbon dioxide in catalytic oxidation of ethylene on silver

Carbon dioxide exerts a strong inhibitory effect on oxygen adsorption and complete oxidation of ethylene on silver but has little effect on the rate of ethylene oxidation to ethylene oxide.

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