O. L. Eliseev

Conversion of Synthesis Gas into Alcohols on Supported Cobalt- Molybdenum Sulfide Catalysts Promoted with Potassium

The use of transition metal sulfides as catalysts for the synthesis of alcohols can solve the problem of catalyst resistance to sulfur. Catalysts based on molybdenum sulfide of different compositions (promoted with Co and K) were synthesized with the use of various supports (aluminum oxide, aluminum oxide modified with silicon oxide, Sibunit, and titanium silicate) and tested in the reactions of alcohol synthesis and the hydrofining of a mixture of thiophene with n-1-hexene. The dependence of catalyst activity in the synthesis of alcohols on support pore size was demonstrated. It was found that an increase in the potassium content of the active phase of a catalyst increased its activity in the synthesis of alcohols and decreased it in hydrodesulfurization and hydrogenation reactions. Transmission electron microscopy data made it possible to quantitatively evaluate the effect of a potassium additive on the morphology of the active phase; the hypothesis that potassium was intercalated between the layers of molybdenum sulfide was proposed.

Modern concepts on catalysis of hydroprocessing and synthesis of alcohols from syngas by transition metal sulfides

A concept on the dynamic nature of active centers (AC) of the catalysts based on transition metal sulfides is described. The concept formed the basis of a “dynamic” model, according to which AC formed and functioning under the reaction conditions can oscillate between layers of promoted molybdenum sulfide. The model assumes the existence of “rapid” and “slow” AC and the possibility of their intertransformation due to the reversible migration of sulfur and promoter between the crystallite layers in a hydrogen atmosphere. The frequency of these migrations (oscillations) determines the catalyst activity. An assumption is substantiated that the hydrogenation sites are localized at the rims of Co(Ni)MoS2 crystallites and desulfurization (hydrodesulfurization) sites are localized on the edges. The proposed model makes it possible to develop criteria for the evaluation of the efficiency of catalytic performance for hydrodesulfurization of hydrocarbon raw materials of various types and for synthesis of higher alcohols from syngas.

Promotion of cobalt catalysts for the Fischer-Tropsch synthesis with alkali metals

The promotion of supported cobalt catalysts for the synthesis of hydrocarbons from CO and H2 with alkali metals was studied. The catalysts were characterized by X-ray diffraction analysis, oxygen titration, and the temperature-programmed desorption (TPD) of CO. Catalytic tests showed that the introduction of alkaline promoters increases selectivity for higher hydrocarbons, decreases selectivity for methane, and also increases the concentration of olefins in the gasoline fraction of products. The promoting effect depends on the catalyst preparation method. The TPD of CO was used to demonstrate that the greatest amount of CO was adsorbed on the surface of a catalyst promoted with potassium; in this case, the strength of CO binding on this catalyst reached a maximum. The data of the TPD of CO correspond to the highest selectivity of a cobalt-potassium catalyst for the formation of higher hydrocarbons.

Catalytic carbonylation in ionic liquids

Synthesis gas, which is formed upon the gasification of solid fossil fuels, is a source of carbon monoxide—a valuable reagent for chemical industry. In this review, studies performed in the last few years at the Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, on the catalytic carbonylation of olefins, alcohols, and halides in ionic liquids are considered. Catalytic systems containing no phosphine ligands were developed; these systems make it possible to recycle the homogeneous catalyst by the extraction of synthetic products from the reaction mass.

Influence of the porous structure of the support on the properties of cobalt catalysts for hydrocarbon synthesis from CO and H2

The dependence of the properties of supported cobalt catalysts for hydrocarbon synthesis from CO and H2 on the porous structure of the supports (aluminas and aluminosilicates) is reported. A correlation between the mean Co0 crystallite size and the pore diameter of the support is established. The specific CO conversion rate falls sharply as the size of Co0 particles decreases to 6 nm and below. The methane and C5+ hydrocarbon selectivities as a function of the Co0 crystallite size pass through an extremum.

Carbonylation of chloroacetone to methyl acetoacetate

Methyl acetoacetate was prepared by the selective carbonylation of chloroacetone in the presence of a homogeneous palladium catalyst at 100 °C and under a CO pressure of 1.5 MPa.

The Mechanism of Synthesis Gas Conversion to Alcohols Catalyzed by Transition Metal Sulfides

The catalysts based on ZnCu or ZnCr oxides and reduced Co that are used to synthesize alcohols and hydrocarbons from synthesis gas (1, 2) are highly sen� sitive to sulfur impurity (3) and require that the feed be purified down to sulfur contents of several ppb. The use of catalysts based on alkali metalmodified molyb� denum disulfide could solve the problem of catalyst stability against sulfur (4, 5). This manuscript reports a comparative study of the synthesis of alcohols from CO and Н 2 and hydrodesulfurization of oil fractions in the presence of sulfide catalysts. The model of interlayer dynamics of active sites of transition metal sulfide catalysts for hydrodesulfuriza� tion proposed in our earlier works (6, 7) implies the presence of two types of sites differing in the activity towards hydrogenolysis of the C-S bond. The more active (fast) site (8, 9) is a combination of promoted and unpromoted MoS2 located on one (type I) or on neighboring layers of the crystallite (type II) according to (10). The site that is less active in hydrogenolysis (slow) is a single cluster of unpromoted molybdenum sulfide. Apart from hydrogenolysis, this site may cata� lyze hydrogenation reactions. The model (6, 7) describes the oscillations of the sulfur atoms and the promoter between the neighboring layers of the molybdenum disulfide crystallites. During the reac� tion, the fast sites are transformed to slow ones and vice versa. The frequency of these transformations determines the catalyst activity.

Hydrocarbon synthesis from a model gas of underground coal gasification

Underground coal gasification gases contain CO and H2; therefore, they can be used as raw materials in the synthesis of higher hydrocarbons. The possibility of obtaining a wide-cut hydrocarbon fraction on a cobalt catalyst was demonstrated with the use of CO-H2-N2 and CO-CO2-H2-N2 model mixtures as an example. In this case, the selectivity for C5+ hydrocarbons was to 96% at a low yield of methane. The resulting hydrocarbons were characterized by a chain-growth probability to 0.89.

Carboxylation of styrene in the N(C4H9)4Br—heptane system

The carboxylation of styrene into carboxylic acids in the N(C4H9)4Br—heptane system in the presence of phosphine complexes and palladium acetate was studied. In the absence of phosphine, the Pd catalyst seems to be stabilized in solution by forming anionic complexes with NBu4Br; the stabilization depends on the acidity of the reaction medium. The catalytic system can be used repeatedly, its activity being reduced only slightly.

Polymetallic catalysts for the Fischer–Tropsch synthesis and hydrodesulfurization prepared using self-propagating high-temperature synthesis

The synthesis, physicochemical characteristics, and operation of the previously proposed new multifunctional polymetallic catalysts in reduction processes are considered. The complex intermetallides of 3d metals and rare-earth elements, which are obtained by self-propagating high-temperature synthesis (SHS), are catalyst precursors. The catalyst structure includes a framework of lower intermetallic compounds covered with a strongly disordered highly amorphous metal oxide active phase. This phase forms two-level nanostructures (~10–100 nm) with a characteristic shape of flat hexahedrons on the surface. The catalysts possess high activity in the reactions of deep oxidation and reduction (the Fischer–Tropsch synthesis and the hydrodesulfurization of petroleum fractions); moreover, they do not require preliminary activation in the reduction processes.