A. V. Lavrenov

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 %.

Propylene production technology: Today and tomorrow

The current industrial and promising technologies and methods for the preparation of propylene from oil and gas raw materials, including combined processes, and processes based on biological raw materials were considered. Special attention was paid to Russian developments in this field.

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.

Heterogeneous oligomerization of light alkenes: 80 years in oil refining

Existing industrial technologies for the production of motor fuel compounds by the heterogeneous oligomerization of light С2–С4 alkenes are considered, along with ones promising for the practical use. Such basic types of systems used as heterogeneous catalysts in these processes as solid phosphoric acid, amorphous alumosilicates, zeolites, ion-exchange resins, anion-modified metal oxides, and nickel-containing catalysts, are described. Special attention is given to the dimerization of iso-butylene with the formation of iso-octene and its subsequent hydrogenation to iso-octane.

FTIR Spectroscopy of Adsorbed Probe Molecules for Analyzing the Surface Properties of Supported Pt (Pd) Catalysts

Supported metal catalysts are important for many fields of applied chemistry, including chemical synthesis, petrochemistry, environmental technology, and energy generation/storage. For prediction of catalyst performance in a chosen reaction and optimization of its functions, it is necessary to know the composition of the surface active sites and have methods for estimating their amount and strength. One of the most available and well-developed methods for studying the composition and structure of the surface functional groups of supported metal catalysts is vibrational spectroscopy, in particular with the use of adsorbed probe molecules.

Liquid-phase isobutane alkylation with butenes over aluminum chloride complexes synthesized in situ from activated aluminum and tert -butyl chloride

The liquid-phase interaction between isobutane and butenes at 303 K and 2.5–3.0 MPa has been investigated using activated aluminum (Al*)-tert-butyl chloride (TBC) model system (TBC: Al* = 0.35−4 mol/mol). It has been demonstrated by attenuated total reflection FT-IR (ATR-FT-IR) spectroscopy that the catalytically active aluminum chloride complexes forming in situ in the hydrocarbon medium vary in composition. Alkylation as such takes place at equimolar proportions of the reactants (TBC: Al* = 1: 1) and butenes feed 1mass flow rate of 5 h−1 per gram of Al*. According to ATR-FT-IR data, the most abundant aluminum complexes resulting under these conditions are the AlCl4− and Al2Cl7− ions and, probably, the molecular complex AlCl3 · sec-C4H9Cl. In a fourfold excess of TBC over Al* at butenes mass feed rate of 2.5 h−1, isobutane undergoes self-alkylation. In this case, the Al2Cl7− ion is not detected and the most abundant complexes are AlCl4−, Al3Cl10− and the molecular species AlCl3 · tert-C4H9Cl. It is hypothesized that the Al2Cl7− ion plays the key role in the liquid-phase alkylation of isobutane with butenes.

Mechanochemical synthesis of nanocrystalline nickel-molybdenum compounds, their morphology and application in catalysis: I. Effect of the Ni: Mo atomic ratio on the structure and properties of nickel-molybdenum compounds prepared under mechanochemical synthesis conditions

Mechanochemical activation in high-energy planetary activators was used for the preparation of highly dispersed nickel-molybdenum compounds. Nickel hydroxocarbonate [NiCO3 · 2Ni(OH)2 · nH2O] and ammonium paramolybdate [(NH4)6Mo7O24 · 4H2O] were chosen as starting compounds. The effect of the Ni: Mo atomic ratio on the composition and structure of products formed in the process of mechanochemical activation followed by calcination was studied. It was found that, at the Ni: Mo atomic ratios of 1.0 and 1.4, the mechanically activated product after calcination at 520°C contained 70–100% β-NiMoO4, which is a stable phase at temperatures lower than 180°C.

Effect of chemical composition and method of preparation on the physicochemical properties of the NiO/B2O3-Al2O3 system and its catalytic activity in ethylene oligomerization

The effect the chemical composition of a support, the content of nickel, and the method of its binding has on the physicochemical and catalytic properties of the NiO/B2O3-Al2O3 system is studied. The boron oxide content in the support is varied from 2 to 30 wt %, while the nickel concentration is 0.59–3.18 wt %. The catalyst samples are studied via X-ray diffraction analysis, temperature-programmed desorption of ammonia, IR spectroscopy (including that of adsorbed CO), and UV-VIS diffuse reflectance spectroscopy. Tests of the catalysts in ethylene oligomerization are conducted in a fixed-bed flow reactor at a temperature of 200°C, a pressure of 1 MPa, and a space velocity of ethylene of 0.5 h−1. The feedstock is an ethylene-methane gas mixture containing 30 wt % of ethylene. It is suggested that the activity of the NiO/B2O3-Al2O3 system in ethylene oligomerization can be attributed to the formation of octahedral Ni2+ cations environed by borate anions on the surface of the system. The most active catalysts contain 2–3 wt % Ni and 10–20 wt % B2O3 in the supports. The method of preparation (adsorption binding or impregnation) has little effect on the state of nickel in the NiO/B2O3-Al2O3 system samples and their catalytic properties. The prepared catalysts are characterized by the ease of preparation, availability, and a low cost of the initial materials, as compared to known catalysts.

Synthesis and characterization of massive molybdenum carbides and supported carbide-containing catalysts Mo2C/C prepared through mechanical activation

Procedures for the synthesis of massive molybdenum carbide by the mechanical activation of a mixture of MoO3, commercial carbon, and Zn in air and the synthesis of the supported carbide-containing catalyst Mo2C/C by the mechanical activation of commercial carbon impregnated with a 16% aqueous solution of ammonium paramolybdate in an inert atmosphere were developed for the first time. With the use of a set of physicochemical methods, the metal contents, particle sizes, specific surface areas, and phase compositions of the mechanically activated composites were determined. The structure of the carbide-containing supported catalyst was studied by electron microscopy, and its acidic properties were studied by the temperature-programmed desorption of ammonia; catalytic tests in the model reactions of dibenzothiophene (DBT) and alkane aromatization were performed. It was found that the Mo2C/C catalyst exhibited high activity in these reactions: the conversion of DBT at a contact time of 3–6 h was 80–85%. The conversion of n-heptane at a contact time of 2 h was 31.2%, and 100% toluene was the reaction product. An increase in the contact time to 6 h led to a decrease in the conversion of n-heptane to 1.3%, and to 47% C6-C7 cycloalkanes were present in the reaction products. The results of this work are indicative of the high catalytic activity of the Mo2C/C catalyst obtained by mechanical activation.