A Kinetic Model for the Epoxidation of Allyl Alcohol with Hydrogen Peroxide on Titanium Silicate TS-1

The kinetic regularities of the oxidation of allyl alcohol into glycidol in the presence of titanium silicate are studied at varied initial concentrations of the reagents, products, and temperature. The probable mechanism is used as the basis to develop a substantial kinetic model, which adequately describes the obtained experimental data.     

Synthesis and electrocatalytic activity of palladium nanoparticles on porous silicon

Palladium was combined with porous silicon into catalytically active functional electrode nanocomposites. Palladium nanoparticles were examined by transmission electron microscopy and atomic force microscopy; their catalytic activity was estimated using cyclic voltammetry.     

Problems of the stereoselectivity in the norbornadiene [2+2]-cyclodimerization reactions catalyzed by hydride nickel(i) complexes. Theoretical aspects

Cyclodimerization of norbornadiene (NBD) yielding pentacyclic products of exo-trans(cis)endo-structure in the presence of the model catalytically active complex Ni(H)(η⁴-NBD) has been studied using the DFT/PBE method. The rate-limiting reaction step is the reductive elimination of the metallacycle, the decomposition of the latter yields the norbornadiene dimer.     

Catalytic activity of bimetallic nanoparticles M@Pd (M = Ni,Cu, Ag,Pt, Au) in deoxygenation of carboxylic acids: a quantum chemical evaluation

Russian Chemical Bulletin - The key intermediates and transition states of the mechanisms of propionic acid decarbonylation and decarboxylation on icosahedral monometallic nanoclusters Pd55 and...     

Distribution of ligands in polynuclear palladium complexes: DFT study of isomerism of Pd4(L)4(RCO2)4 (L = CO,CH2, NO) complexes

Structural isomerism of the Pd₄(L)₄(RCO₂)₄ (L = CO, CH₂, NO; R = CC1₃, CF₃, CH₃) complexes was studied in the framework of the density functional theory (DFT). Among the Pd₄(CO)₄(RCO₂)₄ and Pd₄(CH₂)4(RCO₂)₄ complexes the most stable were the isomers with alternate coordination of pairs of carbonyl and carboxylate ligands on the sides of a planar rectangular metal core. The isomers with the pairwise coordination of NO/RCO₂ on one side of the metal core are the most stable between the Pd₄(NO)₄(RCO₂)₄ complexes. The features of mutual coordination of ligands in polynuclear complexes of palladium are clarified using the obtained results.

     

Quantum-chemical study on the mechanism of catalytic dimerization of norbornadiene in the presence of hydride nickel(I) complex

[2+2]-Cyclodimerization of norbornadiene to pentacyclic products with exo-trans(cis)-exo structure in the presence of model catalytically active η⁴-norbornadiene nickel hydride complex was simulated at the DFT/PBE level of theory. According to the calculations, the rate-determining step in the cyclodimerization process is reductive elimination of the metallacycle whose decomposition yields norbornadiene dimer. The formation of cis-dimer is unfavorable for both kinetic and thermodynamic reasons.     

Catalytic syntheses of poly cyclic compounds based on norbornadiene-2,5 in the presence of nickel complexes: III. Cyclic dimerization of norbornadiene-2,5 in the presence of organophosphorus additives

The cyclodimerization of norbornadiene-2,5 (NBD) catalyzed by the systems formed on the basis of bis(ηy³-allyl)nickel and organophosphorus compounds and the process kinetics are studied. The formation rate of all products follows the overall second-order rate law: first order with respect to the catalyst and NBD. The addition of phosphines and phosphites substantially decreases the reaction rate compared to that in nickel systems containing no organophosphorus additives. The influence of the phosphine ligand structure and temperature on the ratio of the reaction products is studied. The blocking of one coordination site on the nickel atom changes the process kinetics. The loss of two vacancies results in the loss of the catalytic activity of the system. A mechanism explaining the stoichiometry and composition of the reaction products is proposed.     

The influence of the support on activity and selectivity of nickel sulfide catalysts in the decarbonylation of stearic acid to heptadecenes

The influence of the support nature on the performance of nickel sulfide catalyst in the decarbonylation of stearic acid to heptadecenes was investigated. The catalyst supported on silica demonstrated higher activity and selectivity in comparison with the catalyst on γ-Al₂O₃ used as a reference. The reaction schemes over these catalysts are nearly the same; however, the contributions from the side reactions of hydrogenation and oligomerization are reasonably different. Introduction of the products of decarbonylation (CO and water vapor) decreases the stearic acid conversion; and in the case of the catalyst supported on silica, the addition of CO strongly reduces the rate of hydrogenation of heptadecenes. The reasons for the observed differences were discussed. It was suggested that the dispersion of the nickel component as well as the nature of support acidity played a significant role.     

The characteristics of the nanosized η-TiO2 polymorph

The nanosized η-TiO₂ polymorph was prepared by the hydrolysis of titanyl sulfate (TiO)SO₄ · xH₂SO₄ · yH₂O. η-TiO₂ was studied by X-ray diffraction, X-ray photoelectron spectroscopy, IR spectroscopy, and Raman spectroscopy. Characteristic X-ray data and distinguishing Raman spectrum features were found for η-TiO₂,. The surface of η-TiO₂ samples contained adsorbed OH⁻ particles and water molecules or water molecules of crystal hydrates. The free specific surface area of samples with crystallite sizes of L = 50 (4) and 60 (5) ? was S = 10.17 (9) and 15.6 (1) m²/g. The characteristics of samples with η-TiO₂ were favorable for their use as photocatalysts and adsorbents.