n-Butane oxidation over a vanadium-phosphorus catalyst

The activity of vanadium-phosphorus oxide catalysts with respect to maleic anhydride formation in n-butane oxidation has been found to correlate with the concentration of V⁴⁺ ions in the catalysts. The steady catalytic activitv of the samples examined is achieved more rapidly upon prereduction.

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Mathematical simulation of the oxidation of ortho-xylene to phthalic anhydride in a fluidized catalyst bed

Kinetics and Catalysis - The oxidation of ortho-xylene to phthalic anhydride in a catalytic fluidized-bed reactor was simulated. The mathematical model implied that the reactor was separated into...     

Reactivation of vanadium-titanium oxide catalysts foro-xylene oxidation to phthalic anhydride

Reactivation with sulfur containing compounds of vanadium-titanium oxide catalysts for partial oxidation ofo-xylene is studied. The efficiency depends on the kind and quantity of sulfur additives. Most proper reactivation towardso-xylene is reached with sulfur in concentrations of 0.20 wt.%.     

Routes of catalytic oxidation of o-xylene to phthalic anhydride

Relative reactivity of o-xylene, o-tolualdehyde, phthalide, and phthalane and the rate of phthalic anhydride formation from them have been determined. The main route of o-xylene oxidation to phthalic anhydride is due to the o-arrangement of methyl groups, proceeding through bicyclic products, such as dihydrobenzofuran (phthalane) and 3,4-benzofuran.

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-, - , , . - - : () 3,4-.

     

Relaxation of the rate of o-xylene oxidation to phthalic anhydride on vanadium catalysts

Based on numerical analysis of experimental data, the main ideas of the reaction mechanism have been confirmed and kinetic principles of the non-steady=state reaction have been determined.

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Catalyst optimization strategy: selective oxidation of o-xylene to phthalic anhydride

The oxidation of o-xylene and/or naphthalene to phthalic anhydride is one of the important industrial processes based on catalytic selective oxidation reactions. Vanadia--titania catalysts have been used in the industrial phthalic anyhdride process for the last 50 years. The operation parameters like the temperature range of operation, reactor inlet pressures, contact times, o-xylene loadings, etc. were constantly improved during this period of continuous process optimization so as to optimize catalyst performance and increase its life time. However, a fundamental understanding of the mutual interaction of the rather complex reaction network and the catalyst formulation is still missing. Recently, a detailed study of by-product formation as function of process conditions allowed us to develop a novel, improved reaction scheme for the catalytic oxidation of o-xylene. Based on this understanding, a detailed investigation was conducted for the first time of the by-product formation under varying operation conditions and as a function of the active mass variation exploiting high-throughput, as well as bench scales reactors. This high-throughput testing allowed us to relate reaction kinetics to novel catalyst formulations.     

Heat transfer in the desublimation of phthalic anhydride

The heat transfer in the desublimation of phthalic anhydride has been investigated experimentally for the purpose of modelling and developing the design calculation procedure.Experiments were performed on a pilot installation connected to the industrial plant. On the basis of the experimental data, new correlations for the equivalent local heat transfer resistance and the mean equivalent density of the condensate were obtained. The formula for the equivalent heat transfer coefficient in the gaseous phase and the diagram for determination of the efficiency of the process are also given. The validity of the proposed formulae was verified by comparison of the calculated temperature profiles along the condenser with the measured values.     

Unexpected regiospecific reactivity of a substituted phthalic anhydride

Regioselective nucleophilic addition at C1 of anhydride 7 by a range of nucleophiles occurs to produce amide, ester and thioester derivatives 8-15 (60-99%). The increased electrophilic reactivity of the C1 carbonyl group of anhydride 7 is supported by a competition experiment with phthalic anhydride. Unexpected formation of lactams 18 and 19 from amides 12 and 13 was shown to proceed via the lactamols 16 and 17 and could be controlled by the reaction conditions. The solid-state structure of 19 is reported.     

Kinetics of oxidation of acrolein on a vanadium-molybdenum oxide catalyst

A kinetic study has shown that, in the range of low conversions, the reaction rate depends only on the partial pressure of oxygen. Comparison of the oxidation of acrolein and I-deuteroacrolein suggests that the splitting of the H–CO bond is not rate-limiting.

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, , , . 1- , H–CO .

     

Catalytic oxidation of isobutyraldehyde over a molybdenum-vanadium oxide catalyst

The effect of composition of reaction mixture on the gas-phase oxidation of isobutyraldehyde has been studied over a Mo–V oxide catalyst supported on Aerosil. It was found that oxygen, in contrast to water vapor, markedly changes the conversion of isobutyraldehyde and yields of acetone and methacrolein.     

Catalytic oxidation of propylene to acrolein on a multicomponent oxide catalyst

Rate equations have been found and reaction schemes for oxidation of propylene to acrolein and acrylic acid have been suggested.

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Investigation of propylene oxidation on multicomponent a Bi-and Mo-based oxide catalyst

It has been established that porpylene oxidation to acrolein on a multicomponent oxide catalyst containing Mo, Bi, Fe, Ni, Co, K, P and SiO₂ follows an alternating oxidation-reduction mechanism and involves the participation of lattice oxygen with the bond energy of about 280 kJ/mol.

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, Mo, Bi, Fe, Ni, Co, K, P SiO₂ 280 /.

     

Influence of ammonia on propane oxidation over a gallium-antimony oxide catalyst

The influence of ammonia on propane oxidation over a Ga–Sb oxide catalyst has been studied. Acrylonitrile is formed upon the interaction of acrolein with partially dehydrogenated ammonia. Ammonia increases the rates of overall and selective oxidation of propane. This is assumed to be due to the formation of electron-donor sites promoting proton separation from the propane molecule.

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Mechanism of catalysis and factors responsible for oxide catalyst activity in deep oxidation reactions

A general scheme for the deep oxidation mechanism on oxide catalysts including stepwise and concerted mechanisms as well as their mutual transformations is suggested. The principal factor responsible for the activity in the concerted mechanism region is the rate of oxygen binding. For the stepwise mechanism the main factor is the rate of catalyst interaction with oxidizable reactant.

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Effect of catalyst surface modification on pentachlorobutene-1 oxidation to dichloromaleic anhydride

Modification of V–P–O catalyst surface by reaction products changes the reaction course and increases its catalytic activity in pentachlorobutene-1 oxidation to dichloromaleic anhydride.

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V–P–O . -1 .

     

Au/FeOx-TiO2 as an efficient catalyst for the selective hydrogenation of phthalic anhydride to phthalide

<正>Au/FeO_x-TiO_2,prepared by deposition-precipitation method,is an efficient and stable catalyst for the liquid phase selective hydrogenation of phthalic anhydride to phthalide under mild reaction conditions.     

Modification of the surface of a vanadium-phosphorus catalyst by heat and pressure treatment inn-butanol medium

Using X-ray diffraction, X-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD) of NH₃, and mercury porosimetry, we have shown that heat and pressure treatment of a VPBiO catalyst with n-butanol vapors leads to a change in the structure of the sample (increase in the relative content of the [001] plane) and its surface properties (an increase in the P/V ratio, concentration, and strength of acid centers). The modification of the sample occurring under heat and pressure treatment leads to an increase in its activity in oxidation of n-butane and the selectivity of formation of maleic anhydride. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 2, pp. 103–106, March–April, 1999.     

Formation of the active component of a vanadium-molybdenum oxide catalyst in acrolein oxidation

An acrolein-containing reaction mixture reduces V⁵⁺ to V⁴⁺, accompanied by decomposition of the ammonium salt of vanadium-molybdenum-silicon heteropolyacid (HPA) to form a compound with the tentative composition of VMo₃O_11+x, which is the active component of the catalyst.

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V⁵⁺ V⁴⁺, VMo₃O_II+X, .

     

Kinetics of the vapor-phase oxidation of o-xylene over a vanadium oxide catalyst

(Pt–Sn)/Al₂O₃. , , , , .

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The catalytic and adsorption properties of the (Pt–Sn)/Al₂O₃ system have been studied. The results of benzene hydrogenation, cyclohexane dehydrogenation and temperature-programmed hydrogen desorption show that the introduction of tin into the Pt/Al₂O₃ catalyst significantly changes the dispersity and electronic state of supported platinum.

     

Active surface formation on a promoted copper catalyst of the partial oxidation of ethanol

The catalytic properties, chemical composition, and morphology of the surface of electrolytic copper crystals promoted with phosphorus as catalysts of the partial oxidation of ethanol into acetaldehyde were studied. A mechanism of active copper surface formation under the action of the promoting admixture was suggested. Promotion was shown to cause the formation of copper polyphosphates on the surface. Particles of copper metal responsible for selective alcohol transformation are formed in a promoter layer under the action of the reaction medium.