Reaction Kinetics, Mechanisms and Catalysis

A water-soluble Pd(II)-salan complex Na2[Pd(HSS)] (HSS = sulfonated tetrahydrosalen or sulfosalan) was examined as a hydrolytically stable catalyst for hydrogenation of various aldehydes. Na2[Pd(HSS)] was found to be a highly selective catalyst towards hydrogenation of C=C over C=O bonds in cinnamaldehyde and crotonaldehyde (used as representative α,β-unsaturated aldehydes). Kinetic measurements revealed an important role of protonation/deprotonation of one of the phenolate oxygens of the N2O2 coordination framework in the reaction mechanism. Na2[Pd(HSS)] was also found an efficient catalyst for transfer hydrogenation of aldehydes from isopropanol in the presence of various bases. The results show, for the first time, the usefulness of easily accessible, hydrolytically stable Pd(II)-salan type catalysts in aqueous catalytic organometallic hydrogenations.

In the present work, the novel CaO@walnut husk@ZnO nanoparticles were successfully synthesized by immobilization of Zn (II) on walnut husk extract-coated CaO nanoparticles using a simple and clean procedure. The structure and characterization of CaO@walnut husk@ZnO nanoparticles was properly investigated by Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and thermogravimetric analysis techniques (TGA). Furthermore, some of benzylpyrazolylby coumarin derivatives as an important heterocyclic compounds were synthesized in good to high yields by using the related starting materials in the presence of the prepared CaO@walnut husk@ZnO nanoparticles as a high efficient catalyst. The structure of all synthesized products was well characterized by FT-IR, 1H- and 13C-NMR data. This clean procedure offers some advantages such as the use of a green and cheap biocatalyst (prepared from walnut husk waste and eggshells waste) short reaction times, simple workup and high yield of products.

Nitrogen doped mesoporous carbon (N-MPC)-supported monometallic and bimetallic catalysts were synthesized by using hydrothermal and impregnation method, and the catalytic activity of the catalyst to carbon–carbon bond-forming reactions (Suzuki, Heck and Sonogashira reactions) was studied. The bimetallic catalyst Pd-Ni@N-MPC with high Ni to Pd atomic ratios showed highly activity in the C–C coupling reactions of aryl halide under optimized condition. In contrast to their monometallic counterparts, such Pd-Ni@N-MPC catalyst not only show higher catalytic activity but also show more economic and stable. The catalysts were characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope and transmission electron microscopy, which demonstrated that the Pd–Ni NPs highly dispersed and possessed uniform size.

The reaction of N-cyclohexyl-1,3-propanediamine with tert-butyl acrylate and the catalytic effect of hydroxy groups on the reaction course was investigated by Near Infrared spectroscopy. The reaction was found to be bimolecular and of second order. The dependence of rate constant on catalyst concentration (diols) is linear and the structure of diol used has no effect.

The kinetics of solventless transesterification of methyl methacrylate with ethylene glycol has been studied to establish the optimal conditions for ethylene glycol monomethacrylate synthesis. The kinetic data presented show strong dependence of kinetic parameters on initial reagents ratio.

The interaction between nitrogen oxides (NO and N2O) and carbon monoxide over Cr2O3 has been studied. It has been shown that at low temperatures N2O is the main product of NO reduction by carbon monoxide, while at higher temperatures the main products are N2O and N2. The contributions of the consecutive (via N2O) and parallel routes of molecular nitrogen formation have been determined.

The acidic properties of Pd/ZSM-5 catalysts were characterized by NH3-TPD and FT-IR of d3-acetonitrile adsorption. Effect of Pd loading on the catalytic activity and product distribution was studied in the one-step synthesis of methyl isobutyl ketone from acetone. The results indicated that a proper balance between acidic and metallic sites was necessary to obtain high catalytic performance.

Nanosized Au particles were prepared by various methods on MgO. Beside the formation of hexagonal particles, impregnation deposited gold on the supports as rod- and fork-shaped crystals of the nanometer size. The growth of these unusual formations is probably directed by the cracks in the layers of the support, but it must also be the inherent property of the deposited metal.