Boris L. Moroz

Silica-supported zirconocene catalysts: Preparation, characterization and activity in ethylene polymerization

Abstract Supported catalysts for ethylene polymerization have been prepared by interaction of Cp2ZrX2 (Cp=η5-C5H5, X=Cl or CH3) with silica chemically modified by (CH3)3SiCl (TMCS) or trialkylaluminium compounds AlR3 (R=C2H5 (TEA) and i C 4H9 (TIBA)). The interactions between the modificators and the silica surface have been examined by 1 H solid-state MAS NMR spectroscopy, DRIFTS and chemical analysis. The Cp2Zr(CH3)2/SiO2–TMCS catalyst showed a fairly high activity in ethylene polymerization (30–300 kg PE(mol Zr·h·bar)−1) even in the absence of any cocatalysts specially added. The addition of the cocatalyst (MAO or TIBA) led to a further increase in the activity of the supported catalysts. Polyethylene obtained with the Cp2Zr(CH3)2/SiO2–TMCS catalyst without any cocatalyst consisted of uniform polymer particles of a spherical shape replicating that of the silica particles, whereas the shapeless aggregates of finely dispersed polymer particles similar to those usually obtained with homogeneous systems were produced with the same supported catalyst in the presence of the MAO cocatalyst.

Anionic ruthenium cluster K2[Ru4(CO)13] as precursor of catalytically active ruthenium particles and potassium promoter. New efficient ammonia synthesis catalysts based on supported K2[Ru4(CO)13]

Abstract New efficient potassium-promoted catalysts for ammonia synthesis are reported. For preparation of the catalysts, anionic ruthenium cluster K2[Ru4(CO)13] was used as a precursor of both catalytically active metal particles and potassium promoter while magnesium oxide and new original graphite-like active carbon CFC-1 were employed as supports. The catalysts found are capable of catalysing the ammonia synthesis starting from 250°C (1 atm) and exceed markedly in their activity at 300–400°C and atmospheric pressure the industrial ammonia synthesis catalyst (SA-1). Especially effective is the K2[Ru4(CO)13] catalyst on MgO. The replacement of MgO by γ-Al2O3 and SiO2 results in a sharp decrease in activity of the catalyst in ammonia synthesis. This indicates the importance of the basic properties of a support for the achievement of high ammonia synthesis rates.

The effect of Co and Ir on the activity of the K2[Fe2(CO)8]- and K2[Ru4(CO)13]-based systems in ammonia synthesis.: The synergistic acceleration of the ammonia synthesis over the K2[Fe2(CO)8]+K catalysts by iridium

The effect of Co and Ir on the ammonia synthesis over the K2[Fe2(CO)8]+K and K2[Ru4(CO)13]+K catalysts on graphite-like active carbon “Sibunit” has been investigated. The catalysts were prepared by depositing K2[Fe2(CO)8] and K2[Ru4(CO)13] onto the “Sibunit” carbon-supported Co and Ir, followed by thermal decomposition of the deposited cluster and treatment of the resulting sample with metallic potassium. The catalysts containing no potassium metal have been studied as well. It has been found that the presence of Co in the Ru catalysts substantially decreases the ammonia synthesis rate. Similar results have been obtained on testing the Ru–Ir samples. By contrast, the introduction of Ir in the K2[Fe2(CO)8]+K catalysts leads to a synergistic acceleration of the process of the ammonia synthesis. The strongest accelerating effect of Ir is observed at 200°C. A rise in the reaction temperature to 250, 300 and then to 350°C results in a gradual weakening of the Fe–Ir synergism. An important feature of the Fe–Ir catalysts found is their increased activity in the ammonia synthesis at 150°C. The presence of Co in the iron catalysts little affects, in general, the ammonia synthesis rate, although some acceleration of this process by Co at 350 and 400°C for the samples not treated with potassium metal can be noted.

Nanosized Au/C catalyst obtained from a tetraamminegold(III) precursor: Synthesis, characterization, and catalytic activity in low-temperature CO oxidation

A method in which the water-soluble complex [Au(NH3)4](NO3)3 is used as the active-component precursor is suggested for preparing nanosized Au/C catalysts (C = Sibunit, a mesoporous carbon material). The complex is unreadily reducible by the carbon matrix and can be involved in cation exchange with proton-containing groups of the support. This method is referred to as cationic adsorption. It has been demonstrated by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy that the catalyst prepared in this way and treated with H2 at 400°C contains size-uniform gold metal particles with a dominant diameter of <5 nm. The greater part of the gold particles is located on the outer surface of the Sibunit granules; that is, an egg shell type distribution of the active component takes place. The catalyst containing 1.3 wt % Au shows high activity in CO oxidation with excess humid air at 40°C. In this respect, it is far superior to the Au/C catalysts prepared by conventional methods (deposition-precipitation and impregnation), in which the typical gold particle size is several tens of nanometers.

Size effects in catalysis by supported metal nanoparticles

This paper is concerned with the study of size effects in reactions of low-temperature CO oxidation on the catalysts Au/γ-Al2O3 and Au/δ-Al2O3 and complete oxidation of methane on the catalysts Pt/γ-Al2O3. For the synthesis of gold catalysts, four techniques have been applied: ionic adsorption, deposition-precipitation, chemical liquid-phase grafting, and decomposition of volatile gold complexes. Platinum catalysts have been prepared by aluminum oxide impregnation with aqueous solutions of H2[Pt(OH)6] that, depending on preparation conditions, contained mono- or oligonuclear hydroxocomplexes of platinum. Series of catalyst samples with a narrow size distribution of particles and a mean size variation from 0.5–1 to 20–25 nm have been prepared. The study of the catalytic properties of the prepared catalysts has shown that a decrease in mean size of supported metal particles leads to a sharp increase in specific catalytic activity in both systems. The activity maximum has been achieved for active component particles of 2–3 nm. A conclusion has been made that the application of nanosize catalysts is promising for the cleaning of air in closed rooms and vehicle exhaust gases from CO, for the utilization of methane, and for the obtaining of energy by the combustion of natural gas.

New Y(La)-M-O Binary Systems (M = Ca, Sr, or Ba): Synthesis, Physicochemical Characterization, and Application As the Supports of Ruthenium Catalysts for Ammonia Synthesis

The effect of the nature of the alkaline-earth metal on the phase composition and specific surface area of new Y(La)-M-O binary oxide compositions (M = Ca, Sr, or Ba) prepared by coprecipitation was studied. These systems were found to contain mixed compounds (M2Y2O5, MY2O4, and MLa2O4), which are different in thermal stability, in addition to individual La2O3 or Y2O3 phases. The Y(La)-M-O compositions calcined at 450°C were characterized by a more developed specific surface area, as compared with that of individual La2O3 or Y2O3. An increase in the calcination temperature to 650°C was accompanied by a decrease in the specific surface area of binary compositions. Catalysts prepared by supporting K2[Ru4(CO)13] onto the Y(La)-M-O systems were active in ammonia synthesis at 250-400°C and atmospheric pressure. The most active of these catalysts, K2[Ru4(CO)13]/Y-Ba-O, provided a higher yield of NH3 at 250-300°C than analogous catalysts prepared with the use of well-known supports (Sibunit, CFC-1, and C/MgO).

Heterogenized catalysts for olefin hydroformylation containing cobalt and palladium-cobalt complexes anchored on phosphinated SiO2:a 13C solid-state NMR study

Abstract 13 C solid-state NMR technique with high-power H decoupling was employed to study heterogenized hydroformylation catalysts containing the anchored complexes of general composition  Si P 2 Co 2 (CO) 6.6 and  Si P 2 PdCo 2 (CO) 7.8 (where  Si P 2 is the diphosphine ligand covalently bonded to a silica surface). The data on the content and state of complexed CO are compared with those obtained earlier by IR. The values of chemical shift anisotropy provide information on the molecular motion of anchored metal carbonyl fragments. Evidence is presented for the fast restricted motion of these fragments which is not typical for the supported metal crystallites. The interaction of CO, H 2 , and ethylene with the anchored Co and PdCo carbonyl complexes were studied to identify the species which might act as intermediates in hydroformylation reaction. During these studies, the resonances attributed tentatively to π-bonded ethylene and surface propionyls were observed. Based on the data obtained, we discuss the mechanism of action of Co and PdCo catalysts, as well as the reasons of the observed PdCo synergism.

Evidence for formation of aggregates of platinum(II) complexes anchored on phosphinated SiO2 by high-resolution electron microscopy

Aggregates of ∼ 8 A size located not on the SiO2 surface but on ‘stems’ and uniformly distributed on the support have been found by electron microscopy in samples containing platinum(II) complexes anchored on phosphinated SiO2.