V. K. Duplyakin

Liquid-Phase Oxidation of Benzothiophene and Dibenzothiophene by Cumyl Hydroperoxide in the Presence of Catalysts Based on Supported Metal Oxides

The liquid-phase oxidation of benzothiophene and dibenzothiophene by cumyl hydroperoxide in the presence of supported metal oxide catalysts was carried out in octane in an N2 atmosphere at 50–80°C. The cumyl hydroperoxide, benzothiophene, and dibenzothiophene conversions and the yield of sulfones were determined for catalysts of various natures. In the presence of MoO3/SiO2, the most efficient and most readily regenerable catalyst, the benzothiophene conversion was ∼60% and the dibenzothiophene conversion was as high as 100% upon almost complete consumption of cumyl hydroperoxide. The influence of unsaturated and aromatic compounds (oct-1-ene, toluene) on the catalytic effect was studied. The kinetics of substrate oxidation and cumyl hydroperoxide decomposition and an analysis of the cumyl hydroperoxide conversion products suggested a benzothiophene and dibenzothiophene oxidation mechanism including the formation of an intermediate complex of the hydroperoxide with the catalyst and the substrate and its transformation via heterolytic and homolytic routes.

Chemical composition optimization and characterization of the NiO/B2O3-Al2O3 system as a catalyst for ethylene oligomerization

The samples of the NiO/B2O3-Al2O3 system with NiO contents from 0.48 to 38.30 wt % were synthesized by the impregnation of borate-containing alumina (20 wt % B2O3). It was found that nickel oxide occurred in an X-ray amorphous state in the samples containing to 23.20 wt % NiO. At a NiO content of 4.86 wt % or higher, the support was blocked by the modifier to cause a decrease in the specific surface area from 234 to 176 m2/g and in the amount of acid sites from 409–424 to 333 μmol/g. An extremal character of the dependence of catalyst activity in ethylene oligomerization on NiO content was found with a maximum in the range of 4.86–9.31 wt %. Based on spectroscopic data, it was found that ethylene activation on the NiO/B2O3-Al2O3 catalyst can be associated with the presence of Ni2+ cations, which chemically interact with the support. The catalyst containing 4.86 wt % NiO at 200°C, a pressure of 4 MPa, and an ethylene supply rate of 1.1 h−1 provided almost complete ethylene conversion at the yield of liquid oligomerization products to 90.0 wt %; the total concentration of C8+ alkenes in these products was 89.0 wt %.

Oligomerization of butenes on borate-containing alumina

The effects of the chemical composition of borate-containing alumina on its physicochemical properties, catalytic activity, and selectivity in the oligomerization of butenes are reported. The preparation of catalysts containing 2.6–12.4 wt % B2O3 by modifying γ-alumina with orthoboric acid leads to a 9–60 m2/g decrease in the specific surface area and to a 0.02–0.14 cm3/g decrease in the pore volume relative to the same parameters of the initial support. At boron oxide contents of ≥8.8 wt %, these changes are due to the buildup of B2O3 on the catalyst surface. This is accompanied by a decrease in the number of surface B-OH groups, which are active sites of oligomerization. This finding correlates well with the results of catalytic measurements. The catalyst containing 4.5 wt % B2O3 is the most active. It was found by experimental design methods that the most favorable combination of catalytic activity (total butene conversion of 77.8–86.8%) and selectivity (butene oligomer concentration of at least 90 wt % in the liquid product) is attained at T = 150°C, P = 8.0 MPa, and a butene WHSV of 0.5–1.0 h−1. Under these conditions, the butene conversion decreases by no more than 13% from the initial level in 14 h. The activity of the catalyst can be restored by oxidative regeneration.

Hydroisomerization of benzene-containing gasoline fractions on a Pt/SO42−-ZrO2-Al2O3 catalyst: I. Effect of chemical composition on the phase state and texture characteristics of SO42−-ZrO2-Al2O3 supports

A series of SO42−-ZrO2-Al2O3 oxide supports containing from 18.8 to 89.1 wt % alumina was prepared by mixing sulfated zirconia hydrate (weight ratio ZrO2: H2SO4 = 9 : 1) and pseudoboehmite followed by calcination at 650°C. For the subsequent use of the supports to optimize the acid and hydrogenating properties of bifunctional hydroisomerization catalysts of the Pt/SO42−-ZrO2-Al2O3 type, the formation of these catalysts in the course of thermal treatment and their texture characteristics and phase composition were studied. It was found by chemical and thermogravimetric analysis that the addition of pseudoboehmite to sulfated zirconia hydrate resulted in a decrease in sulfur losses in the course of support production from 55.0 to 2.0% with respect to its nominal amount. As the alumina content was increased from 18.8 to 89.1 wt %, the specific surface area and the pore volume of the support increased nonadditively with respect to mechanical mixtures of sulfated zirconia and γ-alumina (from 155 to 197 m2/g and from 0.24 to 0.52 cm3/g, respectively); in this case, a maximum deviation was 18–21%. The experimental results can be explained by chemical interactions between the initial components of the supports. The results of thermogravimetric and X-ray diffraction analysis suggest that the reaction products are sulfated alumina and a sulfated ZrO2-Al2O3 solid solution.

Hydroisomerization of benzene-containing gasoline fractions on a Pt/SO42−-ZrO2-Al2O3 catalyst: II. Effect of chemical composition on acidic and hydrogenating and the occurrence of model isomerization reactions

The acidic and hydrogenating of Pt/SO42−-ZrO2-Al2O3 samples containing from 18.8 to 67.8 wt % Al2O3 as a support constituent were studied by the IR spectroscopy of adsorbed CO and pyridine, and the model reactions of n-heptane and cyclohexane isomerization on these catalysts were examined. The total catalyst activity in the conversion of n-heptane decreased with the concentration of Al2O3; this manifested itself in an increase in the temperature of 50% n-heptane conversion from 112 to 266°C and in an increase in the selectivity of isomerization to 94.2%. In this case, the maximum yield of isoheptanes was 47.1 wt %, which was reached on a sample whose support contained 67.8 wt % Al2O3. A maximum yield (69.6 wt %) and selectivity (93.7%) for methylcyclopentane formation from cyclohexane were also reached on the above catalyst sample. This can be explained by lower concentrations of Lewis and Brønsted acid sites in the Pt/SO42−-ZrO2-Al2O3 system, as compared with those in Pt/SO42−-ZrO2. The experimental results allowed us to make a preliminary conclusion that the Pt/SO42−-ZrO2-Al2O3 catalyst whose support contains 67.8 wt % Al2O3 is promising for use in the selective hydroisomerization of benzene-containing gasoline fractions in the thermodynamically favorable process temperature range of 250–300°C.

Interaction of nickel hydroxocarbonate, ammonium paramolybdate, and ammonium metatungstate under mechanical activation

The interaction of nickel hydroxocarbonate, ammonium paramolybdate, and ammonium metatungstate (Ni: Mo: W = 3: 1: 1) is reported. Under mechanical activation conditions, nickel hydroxocarbonate particles undergo comminution and ammonium paramolybdate and ammonium metatungstate particles soften and aggregate. It is demonstrated by DTA, X-ray diffraction, and IR spectroscopy that heat treatment of the mechanically activated mixture at 400–450°C yields the salts NiMoO4 and NiWO4.

Genesis of the active-component precursor in the synthesis of Pt/Al2O3 catalysts: I. Transformation of the [PtCl6]2− complex in the interaction between chloroplatinic acid and the γ-Al2O3 surface

Gradient elution experiments have revealed the difference between platinum complexes in terms of the strength of their interaction with the alumina surface. A considerable part (30–40%) of the supported platinum is nondesorbable via competitive ion exchange reactions or upon changes in the charge state of the support surface. The surface platinum complexes can be divided into ion-exchangeable and coordinatively fixed species according to the nature of their bonding with aluminum oxide. Combining desorption and spectroscopic methods (EXAFS and diffuse reflectance spectroscopy) has made it possible to characterize the surface complexes. The strongest metal-support interaction takes place in the fixation of hydrolyzed platinum species.

Effect of the concentration of Pt(IV) and Pd(II) chloro complexes on the proportions of their ion-exchanged and coordinatively bound species on the γ-Al2O3 surface

The interaction of platinum(IV) and palladium(II) chloro complexes with the γ-Al2O3 surface in a wide range of surface metal concentrations is reported. Varying the concentration of the adsorbed metal complex on the alumina surface causes changes both in the proportions of weakly and strongly bound desorbable platinum species and in the proportions of desorbable (ion-exchanged) and nondesorbable (coordinatively bound) complexes. The adsorbed palladium complexes are more uniform in chemical composition and binding strength and consist largely of desorbable species removable from the surface by competitive sorption of anions. The absolute amount of coordinatively bound platinum and palladium species increases as the total metal content of the sample is raised to 1.0% and remains almost invariable at higher metal contents.

Interaction between Pt(IV) and Pd(II) chloro complexes in solution and on the γ-Al2O3 surface

The conversions of a mixture of platinum(IV) and palladium(II) chloro complexes in aqueous solution and on the γ-Al2O3 surface at 25–150°C are reported. Heat treatment can initiate interaction between the complexes, both dissolved and adsorbed. The hydrolysis of the chloroplatinate ion is accelerated by the palladium chloro complex, whose composition remains unchanged.

Hydroisomerization of benzene-containing gasoline fractions on a Pt/SO42−-ZrO2-Al2O3 catalyst: III. The hydrogenating properties of the catalyst

The properties and state of platinum in Pt/SO42−-ZrO2-Al2O3 catalysts with various alumina contents have been investigated in benzene hydrogenation as a model reaction using IR spectroscopy, temperature-programmed reduction, and H2 chemisorption. As the Al2O3 content is raised, the hydrogenating activity of the catalyst increases, which is due to the increasing proportion of metallic platinum on the surface.