Isomerization and secondary metathesis of 2-butenes over a MoO3/Al2O3 catalyst

Transformation of cis- and trans-2-butene at 40°C was investigated over a MoO₃/A₂O₃ catalyst reduced with hydrogen and subjected to different pretreatments. Isomerization is accelerated by hydrogen preadsorbed either at low or high temperatures. The cometathesis of 2-butenes with the 1-butene intermediate, however, is enhanced only by hydrogen preadsorbed at low and suppressed by hydrogen adsorbed at high temperatures.

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- -2- 40°C MoO₃/Al₂O₃, . , , . 2- 1- , ; , .

     

AlPO4?ZrO2 catalysts, IV. Cyclohexene skeletal isomerization activity of systems obtained in ethylene oxide

The use of AlPO₄–ZrO₂ (weight ratio AlPO₄/ZrO₂=3) as catalyst systems obtained with ethylene oxide and subjected to different stages of heat treatments has been studied through their catalytic activity in the skeletal isomerization of cyclohexene to 1- and 3-methylcyclopentenes (1- and 3MCP). The apparent rate constants and selectivity to 1-MCP are used for an evaluation of the presence and amount of strong acid sites, the only ones capable of giving rise to skeletal isomerization. The decrease in catalytic activity as calcination increases is consistent with not only the decrease in the amount of acid sites measured vs. weaker organic bases but also with the decrease in Brönsted acidity, as shown by the decrease in O–H band intensity.

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AlPO₄–ZrO₂ ( AlPO₄/ZrO₂=3), , 1- 3- (1- 3-). 1- , . , , , O–H.

     

Studies on catalytically active surface compounds, IX. Formation of O2? radicals on VCl4/SiO2 catalysts

The conditions for the formation of O ₂ ^– on VCl₄/SiO₂ catalysts have been investigated. It is shown that thermal vacuum treatment (TVT) of unhydrolyzed catalysts leads to partial hydrolysis of the surface vanadium complex caused by the silanol groups of the support. The ability of the catalysts to generate O ₂ ^– radicals was found to depend on the degree of hydrolysis caused by thermal vacuum treatment.

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O ₂ ^– VCl₄/SiO₂. , , . , O ₂ ^– , .

     

Kinetics of SO2 oxidation on K2S2O7?V2O5 catalyst in non-steady conditions

Studies of SO₂ oxidation on a molten component of vanadium catalysts in non-steadystate conditions indicates that the kinetics agree fairly well with an oxidation-reduction mechanism. In the low temperature range (<790 K) tetravalent vanadium can be partially crystallized.

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. , - . ( 790 ) .

     

Catalytic oxidative hydrolysis of H2PO2? anions in the presence of RhCl3

Kinetics of H₂ evolution in the RhCl₃–NaH₂PO₂–HCl–H₂O system has been studied. As found by³¹P NMR, Rh(I) complexes with the Rh–P(OH)₂O^– bond are formed and play the role of catalysts in the subsequent H₂ evolution reaction.

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H₂ RhCl₃–NaH₂PO₂–HCl–H₂O. ³¹P Rh(I) Rh–P(OH)₂O^–, H₂.

     

Stereoselectivity observed in cross metathesis of cis- and trans-2-butene with 1-butene over Re2O7/Al2O3 catalyst

Cross metathesis of cis- and trans-2-butene with 1-butene was studied over Re₂O₇/Al₂O₃ catalyst in a recirculation system at 313 K. Formation of ethylene and hexenes was inhibited by 2-butenes; formation of propene and pentene proceeded without induction from trans- and with induction from cis-2-butene and 1-butene. Selective formation of trans-2-pentene was observed from trans-2-butene, but no such selectivity was characteristic for cis-isomers.

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- -2- 1- Re₂O₇/Al₂O₃ 313 . 2-; - -2- 1-. -2 -2-, , - .

     

Partial oxidation of methane on Cr2O3/Al2O3

The oxidation of methane on supported chromia was studied at temperatures varying between 423 and 743 K and CH₄/O₂ ratios between 1 and 9 in a differential reactor. The main reaction products observed were carbon monoxide and formaldehyde. The rates of reaction obey a power law expression.

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, 423 743 CH₄/O₂ 1 9, . . .

     

Catalytic hydrogenation of carbon monoxide on RuFe/SiO2 catalysts

The H₂+CO reaction on silica supported Ru, Fe and RuFe catalysts prepared from metal carbonyl clusters has been investigated under atmospheric and 20 bar pressure. According to the change of selectivity values with temperature and with pressure, the participation of surface carbon proposed earlier by several authors seems to be confirmed by this work.

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H₂+CO Ru, Fe RuFe, , 20 . , , , .

     

Critical phenomena in the flash photolysis of Cl2?H2?O2?HCl and Cl2?F2 mixtures

Critical phenomena in the flash photolysis of gaseous mixtures: 1. Cl₂–H₂ with added O₂ and HCl, and 2. Cl₂–F₂ have been studied by kinetic spectroscopy to measure the rate constants of the processes: Cl+H₂HCl+H, Cl+F₂ClF+F and Cl+O₂+MClO₂+M.

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: I. Cl₂–H₂ O₂ HCl II. Cl₂–F₂ : Cl+H₂HCl+H, Cl+F₂ClF+F, Cl+O₂+MClO₂+M.

     

Electronic influence of water adsorbed on ZnO in H2 and Co oxidation

In this paper we calculate the effect of surface OH/OH^– on the simultaneous adsorption of H₂ and O₂ on ZnO. A quantitative comparison between H₂ and CO oxidation rates shows that the two mechanisms are similar for the same water recovery on ZnO.

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OH/OH^– H₂ O₂ ZnO. H₂ CO , ZnO.

     

Catalysts for metathesis of olefins, prepared by anchoring of MoO2(acac)2 to Al2O3

New highly active catalysts for metathesis of olefins were obtained through the interaction of bis(acetylacetonato)dioxymolybdenum(VI) with surface OH groups of -Al₂O₃ and subsequent reduction in H₂ or CO.

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()(VI) OH -Al₂O₃ H₂ CO .

     

Synthesis and studies of catalysts prepared by supporting Hf(CH2Ph)4 on SiO2 and Al2O3

Catalysts prepared by supporting Hf(CH₂Ph)₄ on silica and alumina were studied. Their catalytic activity in ethylene polymerization was shown to increase considerably upon heating in hydrogen. IR spectroscopic studies of catalysts heated in hydrogen show the formation of surface Hf hydrides.

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, Hf (CH₂Ph)₄ . , . .

     

XPS study of the in-depth profile of TiO2?Al2O3 catalysts prepared by different methods

An XPS study of in-depth profiles of Ti/Al ratio in TiO₂–Al₂O₃ catalysts in conjunction with sputter-etching by Ar⁺ has revealed that the sample prepared with ammonia as precipitation reagent has constant Ti/Al ratio from surface layer to bulk, while the smaple prepared with urea has much Al in the surface layer.

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Ti/Al TiO₂–Al₂O₃ Ar⁺ , , , Ti/Al , , , .

     

Studies of vanadium catalysts for sulfur dioxide oxidation by51V-NMR

Studies of the⁵¹V-NMR spectra of a series of industrial catalysts and systems modelling the active catalyst component indicate that the catalyst composition depends on the preparation method and during thermal treatment the support interacts with the active component. The local environment of vanadium is being formed in the process of catalytic reactions.

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⁵¹V , -I-4, , : KVO₃, KVO₃–SiO₂, KVO₃–K₂SO₄ , , . .

     

ESR studies of T3+ complexes formed in the catalytic system TiCl2(acac)1+Et2AlCl and their interaction with ethylene, carbon monoxide and pyridine

Coordination state of Ti³⁺ions formed in the homogeneous catalytic systems TiCl₂(acac)₂+Et₂AlCl, and its changes upon interaction with ethylene, carbon monoxide and pyridine have been studied by ESR.

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Ti³⁺, TiCl₂(acac)₂=Et₂AlCl, , .

     

Stopped-flow study of the oxidation of ascorbic acid by the oxo-bridged trinuclear ruthenium complex [(NH3)5RuORu(NH3)4 ORu(NH3)5]7+

The kinetics of the oxidation of ascorbic acid by [(NH₃)₅RuORu(NH₃)₄ORu(NH₃)₅]⁷⁺ has been studied by the stopped-flow method. The activation parameters have been calculated and a possible mechanism is suggested.

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[(NH₃)₅RuORu(NH₃)₄ORu·(NH₃)₅]⁷⁺ . .

     

Hydrogenolysis of n-butane on low-loaded Rh/TiO2. II. Catalysts obtained by impregnation

The activity in n-butane hydrogenolysis of Rh/TiO₂ (0.6 wt. % Rh) catalysts propared by impregnation and reduced at different heating rates is reported. The catalyst reduced at 5 K/min is ten times more active than that reduced at 20 K/min, despite the fact that the dispersion values are similar in both cases.

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Rh/TiO₂ (0,6 . % Rh), qv , -. , 5 /, , 20 /, , .

     

Mass-spectrometric analysis of SO3 in SO2 oxidation over vanadium catalysts

The detailed composition of the reaction mixture and, in particular, SO₃ concentration, in SO₂ oxidation over vanadium catalysts, have been determined experimentally. Both oxidized and reduced catalysts were shown to absorb a considerable amount of SO₃, the desorption rate of SO₃ being lower than that of its adsorption.

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, , . , , SO₃, .

     

Phase composition of a selective V2O5?Fe2O3 catalyst of methanol oxidation to formaldehyde

Redispersion of Re/SiO₂ catalysts during air-aging at ambient temperature has been confirmed by TEM analysis. The splitting of large primary crystallites (>10 nm) under the influence of the strain energy of the oxide layer formed on the Re surface has been proposed to explain the observed phenomenon.

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Re/SiO₂ . , Re(>10 nm), , .

     

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.