T. A. Isakova

Catalytic properties of synthetic mordenite in the isomerization, hydrogenation, and hydroisomerization of certain hydrocarbons

1. The catalytic properties of synthetic mordenite in the isomerization of n-pentane and cyclohexane, and the hydrogenation and hydroisomerization of benzene in the presence of hydrogen were investigated. 2. The hydrogen form of mordenite is an active catalyst of the isomerization of saturated hydrocarbons, while the introduction of palladium and nickel into the H-form of mordenite does not increase the activity of the catalyst. 3. The sodium-form of mordenite is an active catalyst of the hydrogenation of benzene.

Transformations of butyraldehyde in the presence of catalysts based on large-pore molecular sieves VPI-5 and AlPO4-8

It is found that zeolite-like crystalline aluminophosphates VPI-5, Si-VPI-5, and Mn-VPI-5 as well as those dirived from them, AlPO{in4}-8, SAPO{in4}-8, and MnAPO{in4}-8, are capable of catalyzing aldol condensation and crotonization of butyraldehyde (BA). Pd/AlPO{in4}-8 is catalytically active in hydrocondensation of BA with H{in2} at atmospheric pressure. The activities in BA conversion to 2-ethylhexane-3-ol-1-al increase in the following order: Mn-VPI-5 < Si-VPI-5 < VPI-5. The same order of activities is also found for AlPO{in4}-8, SAPO{in4}-8, and MnAPO{in4}-8. These catalysts are characterized by a lower initial activity in crotonization of BA than M{su+}NaX (CsNaX), but they are much more stable. Pd/AlPO{in4}-8 catalyzes BA conversion to 2-ethylhexanal even in the absence of H{in2} feed to the reaction zone. The influence of catalyst pretreatments and experimental conditions on the catalyst structures and catalytic activities is discussed.

A study of polyfunctional zeolite catalysts. Communication 7. Catalytic properties of metal-M1+NaX zeolite systems in the hydrocondensation of butyraldehyde

Conclusions1.Butyraldehyde and hydrogen are converted to 2-ethylhexanal and 2-ethyl-1-hexanol on systems containing and metal (Pt, Pd, Rh, Ni, and Co) and zeolite M1+NaX (M1+=Na+, K+, and Rb+) at atmospheric pressure and 100–200°C. This finding confirms the bifunctional catalytic effect of these systems.2.The Pd/M1+NaX systems displays the greatest selectivity of the catalysts studied in the one-step synthesis of 2-ethylhexanal from butyraldehyde and H2.

Selective alkylation of xylenes by alcohols on zeolite catalysts

The peculiarities of catalytic performance of crystalline aluminosilicates of different types and compositions (X, Y including dealuminated Y′, mordenite, pentasil ZSM-5), as well as of amorphous aluminosilicate catalyst in conversion of xylene + alcohol mixtures were studied. New data were obtained for alkylation ofo-xylene withtert-butyl alcohol, concerning controlling the selectivity and stability of the zeolite catalysts in reactions proceeding with the participation of water, including the water evolved during the reaction, in particular by controlling the acidic properties and hydrophobycity of the zeolites. A catalyst ensuring production of 1,2-dimethyl-4-tert-butylbenzene (DMTBB) with a 94% yield and selectivity of alcohol conversion to the target product of 94–97% was developed. The catalyst can be used as the basis for a high-performance and environmentally safe method for the synthesis of DMTBB. The catalysts developed can be also used for selective alkylation ofo-xylene by C3-C5 alcohols and for alkylation ofm-xylene bytert-butyl alcohol.

New Application of Zeolite Systems in Catalitic Organic Synthesis

The efficiency of zeolites as catalysts for the hydrolysis of 4-cyanopyridine into isonicotinamide, for the hydrolytic hydrazinolysis of 4-cyanopyridine resulting in hydrazide of isonicotine acid and for diene condensation of furane and mircene with methylvinylketone has been shown. The one step synthesis of sec. butyhl derivatives of aromatic compounds from C 6 H 5 R (R=H, CH 3 , Cl, Br) and ethylene or ethanol or ether as well as the synthesis of ethyltoluene and xylene from toluene and methanol were carried out by means of multifunctional catalytic systems.

Catalytic properties of X and Y zeolites in condensation of butyraldehyde

Conclusions1.On X and Y synthetic zeolites at atmospheric pressure and 100–200°, butyraldehyde (BA) is converted to 2-ethylhexenal and water.2.On the basis of the relationships observed in catalytic effects in the crotonaldehyde condensation of BA, crystallites containing the cations Na+, K+, Rb+, and/or Cs+ manifest the properties of solid bases. Samples of M+NaX are far more active catalysts than M+NaY, Mn+NaX, or Mn+NaY.3.NiNaX, dehydrated in a flow of air, catalyzes only the condensation of BA to 2-ethylhexenal, and it is a monfunctional catalyst. When this zeolite is treated with hydrogen at 350–400°, reducing the Ni2+ to Ni0, polyfunctional systems are formed, simultaneously accelerating reactions of BA condensation and hydrogenation of the carbonyl compounds, combined in a single process; the interaction of BA with H2 on these catalysts proceeds with the formation of 2-ethylhexanal and 2-ethylhexanol.

Catalytic properties of superhigh-silica zeolites in conversions of certain hydrocarbons

Conclusion1.On the basis of decationized forms of superhigh-silica zeolites with a mole ratio SiO2/Al2O3 from 33 to 83, new and effective Pd catalysts have been synthesized for n-pentane isomerization, n-butane disproportionation, n-hexane isomerization and hydrocracking, and benzene hydrogenation.2.A correlation has been established between the hydrocracking (or cracking) activity of the decationized forms of the zeolites and the isomerizing activity of the Pd/HTsVK catalysts in n-pentane conversions.

Dual action of hydrogen on the catalytic activity of Nay, Na-mordenite, and NaA zeolites in hydrogenation reactions of acetone and benzene

Conclusions1.The influence of hydrogen on the catalytic activity of Na-mordenite, NaY, and NaA zeolites in hydrogenation reactions of acetone and benzene was studied. Hydrogen at 400–500°C practically completely deactivates the catalysts. Air or helium reduces the hydrogenating activity of the catalysts.2.Treatment of NaY with hydrogen at 190–250° C and atmospheric pressure leads to a sharp increase in the hydrogenating activity of the catalyst.3.The obtained results in conjunction with literature data permits the assumption of the existence of two forms of hydrogen, chemisorbed on zeolites in the Na form. The first of these is formed mainly at relatively low temperature and pressure and activates the catalyst, whereas the second form, which is formed at relatively high temperature and pressure, suppresses the hydrogenating activity of the zeolites.

Kinetics and mechanism of hydrogenation of toluene on the Na form of synthetic mordenite

1. The authors have investigated the hydrogenation of toluene on the Na form of synthetic mordenite at 160–200° and 3–50 atm. 2. The rate of the reaction obeys the equation\(r = kP_{H_2 }^{0.5} \). It is suggested that the limiting stage of the reaction is the attachment of the first hydrogen atom or ion to the aromatic ring.

Investigation of the isomerization of cyclohexane on a palladium-zeolite catalyst by the method of mathematical planning of experiments

1. The reaction of isomerization of cyclohexane on a catalyst 0.5% Pd/CaY was investigated using the method of mathematical experimental planning. 2. On the basis of the regression equation, adequately describing the experimental data, the kinetic parameters of the reaction were calculated. 3. Depending on the conditions, the reaction does not reach equilibrium to a greater or lesser degree. The unachievability of equilibrium can be considered by introducing the corresponding coefficient.