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1.On high-silica zeolites of the pentasil family, xylenes are converted to isomerization products with high selectivity. In the presence of wider-pore zeolites, the isomerization is accompanied with a considerable degree of disproportionation, the contribution of which increases with increasing diameter of the zeolite pores.2.The hydroxyl cover in the pentasils has a far higher thermal stability than in the mordenites; and as a consequence, the pentasils retain high catalytic activities even when heat-treated at 700°C.3The acidic centers of zeolites of the pentasil and mordenite types are similar in heats of ammonia adsorption and in their specific activity in xylene conversion.

1.The introduction of 0.3% vanadium into decationized SHSZ increases the overall yield of aromatic products in isobutylene conversion at 320°C by a factor of 1.5. This effect is considerably less pronounced at 500°C.2.Increases of the vanadium concentration in the zeolite lead to higher contents of p-xylene in the C8-alkylbenzene fraction.

1.Mordenite catalysts dealuminated by 50% show the highest activity for the isomerization of o-xylene.2.At low degree of conversion, the ratio of the disproportionation and isomerization rates of o-xylene is independent of the aluminum content of the mordenite framework, and the closer one approaches equilibrium, the more the disproportionation contribution increases with increasing degree of dealumination.

Capture and reversible high-temperature chemisorption of hydrogen is observed on catalysts containing reduced V2O5 supported on MgO and Al2O3 which have been heated to 500°C. The amount of hydrogen taken up in chemisorption varies with the concentration of V2O5 and the nature of the carrier, the latter factor determining the relative ease of desorption.

1.The Bi, Sn, Sb, and In oxides are inactive as catalysts for the aromatization of isobutylene. The Zn, Ti, Th, and V oxides are slightly active in this reaction, but in the case of the Ti and Zn oxides the liquid reaction products contain mainly p-xylene (respectively 80.8 and 63.2%).2.The catalysts, obtained by depositing V2O3 on Al2O5, Al2O3(F), and SiO2, have a high activity, in which connection the main reaction products are xylenes, the amount of which in the catalyzates is respectively 76.2, 75.4, and 93.4%. The ratio between the individual reaction products and, in particular, between the C8 aromatic hydrocarbons, depends on the V2O5 concentration in the catalyst.3.The relative amount of the isomeric xylenes and ethylbenzene in the reaction products is apparently due to the isomerization of the isobutylene dimer, which is formed in the first step of the aromatization reaction.

1.An increase in the temperature of the aromatization of propylene and isobutylene in the presence of aluminum oxide from 300 to 625°C is accompanied by an increase in the conversion of the original olefins; appreciable formation of aromatic hydrocarbons occurs only above 500°C. The greatest selectivity with respect to aromatic hydrocarbons is achieved at 550–625°C.2.An increase in contact time is accompanied by a significant increase in the conversion of the original olefins, but does not exhibit an appreciable influence on the composition of the liquid reaction products nor on the selectivity with respect to aromatization.

The catalytic and acid properties of erionites with a different degree of decationization were studied. IR spectroscopy showed that Brönsted acid sites are formed on the outer surface of the erionites as a result of decationization. It was shown that these sites are responsible for the occurrence of reactions of oligomerization of isobutylene and structural isomerization of trimethylpentenes.

1.With a constant concentration of Zn (1.5%), the catalytic activity of pentasils in aromatization of C3-C4 alkanes increases as the concentration of Al in the framework increases.2.The selectivity with respect to the formation of aromatic hydrocarbons from propane and isobutane on Zn-containing pentasils is not a function of the Si/Al ratio. Transformation of propane and isobutane into products of aromatization and C1-C2 alkanes takes place parallelly.3.Strong Lewis acid sites responsible for activation of the molecules of lower alkanes are formed as a result of modification of the pentasils with zinc.

1.In studying the isomerization and disproportionation of xylenes, the temperature range of the formation and destruction of active centers in zeolites of the pentasil and mordenite type was established. Active centers resistant to heat treatment at 973–1073 K are present on the surface of zeolites prepared by direct synthesis.2.After treatment of zeolite of the pentasil type with air at 1073–1273 K, the selectivity with respect to formation of p-xylene increased significantly, and the reaction of disproportionation of the xylenes with a decrease in the total catalytic activity was inhibited.

1.The transformation of ethylene, propylene, and isobutylene into aromatic hydrocarbons in the presence of Al2O3, Al2O3(F), Al2O3-SiO2, CaHY zeolite + 16% Al2O3, and active carbon has been studied in a noncirculatory system at 550°C. In all cases, the liquid reaction products contain mainly benzene, toluene, xylenes, ethylbenzene, and aromatic hydrocarbons with the composition C9-C11.2.With an increase in the number of carbon atoms in the olefine molecule, the conversion of the original hydrocarbons increases and the concentration of aromatic hydrocarbons in the liquid catalyzate also increases.3.The highest yield of liquid catalyzate, characterized by the maximum concentration of aromatic hydrocarbons, is obtained with the aromatization of ethylene, propylene, and isobutylene in the presence of fluorinated Al2O3. However, with respect to selectivity, this catalyst is less good than aluminum oxide without fluorine.

A study has been made of the catalytic and acidic properties together with the surface composition of the zeolite HZSM-5 modified by gallium by hydrothermal treatment with a sodium gallate solution and also by impregnation with gallium nitrate solution. It has been established that the first method of introducing gallium produces a more selective catalyst for aromatization of n-butane. It has been shown that under the conditions of the catalytic reaction several types of active centers incorporating Ga are formed: Ga2O3 on the zeolite surface, gallium ions inside the zeolite canals, and gallium atoms at the surface of and in the lattice that are bonded to OH groups.

1.L zeolite exhibits weak selectivity for NH4+ cations which decreases as the degree of ion exchange increases in substitution of potassium cations with ammonia ions.2.Only L zeolites with a degree of decationization above 50% exhibit catalytic activity in transformation of o-xylene.3.Isomerization of xylenes on L zeolites primarily takes place by means of intramolecular transformations.

1.A study has been made of the conversion of m- and o-xylenes in the presence of an ultra-high silica zeolite in the initial and decationized forms and in the presence of decationized and dealuminated mordenite at 150–550°C, atmospheric pressure, and a space velocity of 180 h-1.2.The Na- and H-forms of the ultrahigh-silica zeolite lead mainly to the isomerization of xylenes, while the isomerization and disproportionation of xylenes take place on the mordenites.3.In the presence of the Na- and H-forms of the ultrahigh-silica zeolite, which possesses a high stability in comparison with the decationized mordenite, the isomerization of m- and o-xylenes is characterized by an enhanced selectivity with respect to the formation of pxylene.

1.Depending on the temperature, in the transformations of propylene and isobutylene on decationized UHS zeolite the oligomerization, isomerization, aromatization, dealkylation, hydrogenation, cracking, and disproportionation of the hydrocarbons can proceed both as consecutive and parallel reactions.2.Isobutylene is selectively oligomerized on the decationized UHS zeolite at 90–210° to give a mixture of 85% isobutylene dimers and 15% trimers in ?45% yield.3.The decationized zeolite has a high activity and selectivity in oligomerization and aromatization reactions, which permits obtaining higher yields of mixtures of both aliphatic (>90%) and aromatic (?50%) hydrocarbons at lower temperatures than in the case of the starting form of this zeolite.4.In the reaction with isobutylene the decationized zeolite at 500° and t=7.2 sec does not lose its catalytic properties for 6 h, and gives a liquid catalyzate, containing 99% of aromatic hydrocarbons, in 47–48% yield.

In contrast to zeolites with ultrahigh silica content, type A, X, Y, and M zeolites in the Na form and also those modified by decationization, cation exchange, and addition of?-Al2O3, Al2O3-SiO2, Pt, and Rh show a low activity in the aromatization reaction of C3-C4 olefins at 450–550°C at times of contact of 2–14.4 sec. The zeolites studied become rapidly deactivated as the result of intense coke formation.

1.The authors have established the laws of hydrogenation during the reaction of alkali metals and hydrogen with elements of the gallium subgroup. They show the possibility of direct preparation of potassium and cesium tetrahydridogallates MGaH4, sodium and cesium hexahydridogallates M3GaH6, and complex hydrides of indium and thallium in impurity amounts.2.In M-E-H2 systems (M is an alkali metal, E=Ga, In, or Tl), besides hydrides intermetallides MnEm are formed.3.The effect of heating on the intermetallic and hydride phases has been investigated, the IR spectra have been recorded, and CsGaH4 and CsGa Identified by x-ray phase analysis.

1.As the Na2O content of ultrahigh-silica zeolites increases, the yield of liquid catalysate and aromatic hydrocarbons from isobutylene at 500°C decreases.2.As the temperature of preliminary calcination increases from 500 to 1000°C, the water-sorption capacity of ultrahigh-silica zeolites gradually decreases. Calcination at 800–1000°C hardly affects the total zeolite activity but decreases its activity in the dehydrocyclization and hydrogen redistribution reactions. After zeolite calcination at 1000°C, an increase in selectivity for p-xylene formation is observed.3.The change in the catalytic properties of ultrahigh-silica zeolites after calcination at 800–1000°C is related to the removal of a small number of OH groups which enter into the composition of the active centers. The selectivity increase for p-xylene formation can be attributed to some changes in the pore structure at high temperature which make the diffusion of m- and o-xylene difficult.

1.The original form of ultrahigh-silica zeolite shows activity in the aromatization of 1-octene at 400–500°C and atmospheric pressure. Modification of the zeolite by adding Pt, Rh, and V2O5 increases the aromatic hydrocarbon yield.2.In the presence of V2O5-modified ultrahigh-silica zeolite, 1-octene is predominantly converted to p-xylene. The p-xylene content in the catalysate increases with decreasing temperature.3.The hypothesis is proposed that selective formation of p-xylene is caused by blockage of the zeolite channels by the V2O5 additive, leading to difficulty in the desorption of the meta and ortho isomers of the dialkylbenzenes.

1.The method of adsorption of nickel carbonyl on aluminum oxide, followed by decomposition, can be used for the production of Ni/Al2O3 catalysts, the activity of which per gram of the catalyst in the hydrogenation of CO2 is somewhat greater than that of samples obtained by the usual methods of impregnation or coprecipitation. Repeated adsorption with blocking permits a substantial increase in the activity.2.In an investigation of the dependence of the catalytic activity on the nickel content, the existence of a lower concentration threshold was detected, the absolute value of which depends on the method of preparation of the catalyst and the properties of the initial aluminum oxide. Evidently this phenomenon is due to the different strength of the chemisorption bond to the surface and to difference in the sizes of the nickel crystallites.3.For the investigated catalysts the specific catalytic activity of Ni in the region of nickel concentrations above the critical threshold retains approximate constancy, while the activation energy changes appreciably in the region of very low and comparatively high concentrations. A substantial influence on the catalytic activity is exerted by the nature of the surface inhomogeneity of the initial aluminum oxide.

1.The solubility in the system RbGaH4-diglyme was studied in the interval from -66 to+115° by isothermal, visual-polythermal, and differential thermal methods.2.The existence of the solvates RbGaH4 · 6DG and RbGaH4 · 2DG, which melt incongruently at -36 and 80°, respectively, was established.3.Above 80°, nonsolvated RbGaH4 is at equilibrium with the solution.

1.In the reactions of propylene and isobutylene in the range 450–580‡ the ultrahighsilica zeolite catalyst (UHSZ-23) has a high aromatizing capacity and makes it possible to obtain liquid catalyzates, which contain 90–93% of aromatic hydrocarbons, in over 40% yield. At temperatures below 320‡ this catalyst actively catalyzes the oligomerization of the starting olefins and also the isomerization, hydrogenation, disproportionation, and cracking of the formed oligomers.2.In 6 h of operation the yields of the liquid catalyzate remain constant (42–43%). However, in the first 2 h of operation the yield of the aromatic hydrocarbons decreases (from 30 to 25%), while the yield of the aliphatic hydrocarbons increases (from 13 to 18%).3.It was established that significant differences are absent in the composition of the liquid and gaseous transformation products of propylene and isobutylene.