E. V. Slivinskii

Hydrogenation of CO2 to formic acid in the presence of the Wilkinson complex

Formic acid was synthesized in a high yield at room temperature in the presence of the Wilkinson complex and an excess of PPh3. The catalytic properties of the rhodium complex depend strongly on the reaction conditions. The mechanism of the rhodium catalyst deactivation was studied by the kinetic method and 31P NMR spectroscopy. The methods for the stabilization of the rhodium catalyst were found.

Construction of the reaction networks for heterogeneous catalytic reactions: Fischer—Tropsch synthesis and related reactions

The key approaches to the generation of reaction networks for the synthesis of products from CO and H2 are considered. The selection rules for the elementary steps on the surface of heterogeneous catalysts are formulated. Data on the surface compounds and steps related to reactions of CO and H2 are analyzed and a set of transforms (models of elementary steps) for generation of the reaction network are selected. Eight variants of generation of reaction networks for the formation of C1 products with different sets of transforms (12 to 31) were tested in computer experiments, and eight reaction networks comprising 34 substances and 132 to 1647 elementary steps were obtained. The pathways to CO2, CH4, and CH3OH and pairs of compounds CH4, CO2 and CH4, HCOOH obtained from the reaction network (220 elementary steps) are compared with the published schemes.

Polymeric rhodium-containing catalysts in olefin hydroformylation

The main results obtained by studying hydroformylation of olefins on polymeric rhodium-containing catalysts are reviewed. Different types of N-containing polymeric ligands capable of hydroformylating under conditions of heterogeneous catalysis are considered. Possibilities of using water-soluble polymers containing quaternary ammonium groups are shown. The data on the influence of a polymeric matrix on the catalytic properties of the rhodium catalyst of olefin hydroformylation are presented.

Modification of rhodium carbonyl catalysts for hydroformylation of 2-butenes by organophosphorus ligands

The influence of the nature of the organophosphorus ligand and the P/Rh molar ratio on the catalytic properties of rhodium carbonyl complexes in hydroformylation of 2-butenes was studied. The difference between phosphine and phosphite ligands during the formation of highly selective catalytic complexes was found. It was supposed that a decrease in the selectivity with respect to 2-methylbutanal is due to the isomerization of olefins under conditions of a decrease in the competitive capability of CO for coordination sites (the high P/Rh ratio, a decrease in the total pressure of the synthesis-gas).

Hydrogenation of CO2 conjugated with dehydrogenation of cyclohexane over an intermetallic catalyst

Transformations of carbon dioxide catalyzed by the hydride form of [TiFe0.95Zr0.03Mo0.02]Hx, by the industrial Pt/Al2O3 catalyst, and by a mixture of the above materials were studied. Study of the thermal desorption of H2 showed the presence of two forms of absorbed hydrogen, namely, the weakly bound hydrogen, which is evolved from the intermetallic structure on heating to 430 °C under Ar, and the strongly bound hydrogen (SBH), which remains in the intermetallic compound at higher temperatures (up to 700 °C). In a carbon dioxide medium, the SBH enters into selective CO2 reduction to give CO at 350—430 °C and 10—12 atm. The selectivity of the formation of CO reaches 80—99% for conversion of CO2 between 50—70%, the SBH being consumed almost entirely for the reduction of CO2. In the presence of the mixed catalyst, conjugate reactions proceed efficiently; dehydrogenation of cyclohexane yields hydrogen, which is consumed for CO2 hydrogenation.

Structure and acid-basic properties of the surface of titanium oxides modified by phosphorus and aluminum and prepared by the alkoxo method. 2. Study of the active surface of titanium oxides

The data of temperature-programmed desorption of ammonia from the surface of oxide systems and IR spectroscopy were used to demonstrate that the strength of the surface acid sites in titanium oxides prepared by the alkoxo method and modified by aluminum decreases with respect to that in nonmodified titanium oxide. Modification of titanium oxide with P3+ ions from ethriol phosphite almost completely suppresses the acid properties. Modified oxides are able to chemisorb water. XANES data suggest that modification of titanium oxide with phosphorus ions increases the electron density on the titanium atoms and, correspondingly, the basicity of the materials.

Structure and acid-basic properties of the surface of titanium oxides modified by phosphorus and aluminum and prepared by the alkoxo method

An alkoxo method for the preparatio of single-phase titanium oxides modified by phosphorus and aluminum is proposed and the mechanism of oxide formation is investigated. Structural studies showed that the sizes of the anatase microcrystallite grains and mesopores in the systems are characterized by a uniform distribution. The nature of the modifying agent and the conditions of synthesis influence the interatomic distances and the dimension ofc, the tetragonal unit cell constant of anatase.

Isobutene hydroformylation in catalytic systems based on rhodium compounds and polyelectrolytes

The catalytic properties of water-soluble systems based on rhodium complexes and polyelectrolytes in isobutene hydroformylation were studied. All of the catalytic systems exhibited an unexpectedly high activity under the conditions where homogeneous hydroformylation virtually did not occur in the presence of conventional rhodium catalysts. A stable catalytic system based on acacRh(CO)2-PEG complex was proposed, allowing isobutene hydroformylation to be performed with a high activity under mild conditions.

Transformation of rhodium carbonyl complexes in hydroformylation of 1-hexene studied fromin situ IR spectroscopic data

Rhodium carbonyl complexes that formed from RhCl3·4H2O and RhCl3·4H2O modified by poly-N,N-dimethyl-N,N-diallylammonium chloride in a methanol—chloroform medium in the hydroformylation of 1-hexene were studied byin situ IR spectroscopy. Along with the rhodium hydrocarbonyl complexes, anionic complexes of the [Rh(CO)2Cl2]− type, whose concentrations and rates of formation in an acidic medium are much higher than those in a basic medium, were shown to be the active centers of hydroformylation. The function of the polycation is the stabilization of the catalytically active mononuclear rhodium complexes.

Effect of composition of the aqueous phase on catalytic properties of RhCl3 modified with a polycation in hydroformylation of 1-hexene

Water-soluble catalytic systems based on RhCl3 and the salts of polycations (poly-N,N-diallyl-N,N-dimethylammonium chloride and poly-N,N-diallyl-N-methylaminodihydrophosphate) have been studied. It has been established that the rate of hydroformylation of 1-hexene increases with increasing pH of the aqueous phase. The replacement of the alkyl group at the nitrogen atom with the hydrogen atom in a polycation makes it possible to form a stable catalytic system at pH ≥5. The addition of low molecular electrolytes (NaCl, Na2SO4, and NaPO4) also affects the catalytic properties of the studied catalytic systems. Stability of a catalytic system is enhanced with increasing charge of an anion of a low molecular electrolyte, which is, apparently, due to formation of intra- and intermolecular bonds in polyelectrolytes.