The formation of carbonaceous layer from ethylene over various transition metal catalysts – an FT-IR study

The ethylene-derived carbonaceous overlayers were studied over silica-supported Pt, Pd, Rh and Cu catalysts by FT-IR spectroscopy under desorption conditions. As a general feature it was observed over all catalysts that upon increasing the desorption temperature the overlayer gradually became poor in hydrogen. The structure of the overlayers was similar over the silica-supported Pt, Pd and Rh. On increasing the reaction temperature the σ-adsorbed half-hydrogenated species are transformed to adsorbed ethylidyne. On the Cu catalyst prepared with ion exchange a similar picture emerged, while on those prepared with precipitation ethylidyne soon became the predominant species. Hydrogen swept off the carbonaceous species from the transition metals, however, copper retained large portions of it

Onium salts as catalysts in the liquid-phase oxidation of cyclohexene or tetraline by N2O

The liquid-phase oxidation of cyclohexene or tetraline with N2O was studied in various solvents in the presence of onium salts or without them. The onium salts exerted significant promoting effect on the reactions. The activation of the oxidant was studied by IR spectroscopy. It was found that the interactions of the ions in the onium salts and the polarised N–O bond further enhanced polarisation leading to an activation of the oxidant, thus, increasing the rate of oxidation

Nagyszelektivitású katalizátorrendszerek kifejlesztése = Towards 100% selectivity - development of highly selective catalytic systems

Kezdetben Cu-Tyr és Cu-His komplexek kovalens immobilizálására került sor, ahol C- illetve N-védett aminosavakat használtunk. A hordozók klórpropilezett szilikagél és Merrifield gyanta voltak. A komplexek kialakítására a védőcsoport eltávolítása után került sor. A későbbiekben Cu-, Co-, Fe- és Ni-aminosav komplexeket készítettünk a fenti hordozókon úgy, hogy a C- vagy N-védett aminosavakat (hisztidin, tirozin, cisztein, cisztin) a hordozóra kovalensen rögzítettük, majd kialakítottuk ki a fémkomplexeket. Az anyagokat szerkezetileg jellemeztük, és teszteltük SOD aktivitásukat. A védőcsoportot tartalmazó felületi komplexek aktívabbak, mint a védőcsoport nélküliek, a ligandumszegény környezetben szintetizáltak aktívabbak, mint a ligandumban gazdag környezetben készítettek, a fehérjevázhoz hasonlónak gondolt gyanta nem növelte a katalitikus aktivitást, és a Cu(II) ion geometriája a felületi komplexben torzult tetraéderes. A továbbiakban felületre kovalensen kötött vegyes ligandumú komplexeket készítettünk. Kidolgoztunk háromféle szintézismódszert, amely nagyszámú katalizátort eredményezett. A központi ionok Cu(II), Co(II), Fe(III) és Ni(II), a ligandumpárok C- vagy N-védett hisztidin és tirozin, vagy hisztidin és cisztein, vagy hisztidin és cisztin vagy cisztein és cisztin voltak az eddigi hordozókon. Sokféle koordinációs módot láttunk, és azt tapasztaltuk, hogy a felületi komplexek szerkezete a készítésmódtól is erősen függ. Sok esetben jelentős SOD aktivitást mértünk. | We started with the synthesis of covalently grafted Cu-Tyr and Cu-His complexes using C- or N-protected amino acids. Chloropropylated silica gel or Merrifield's resin was the support. The complexes were made after deprotecting the amino acid ligands. Later, surface-anchored Cu-, Co-, Fe- és Ni-amino acid complexes were prepared on the same supports using C- or N-protected histidine, tyrosine, cysteine and cystine and covalent bonding. The substances were structurally characterised and their SOD activities were tested. Surface complexes with protected amino acid ligands were more active than with deprotected ligands, those made under ligand poor conditions were more active than those made under ligand-excess conditions, the resin, thought to be similar to the proteomic skeleton, did not increase activity, and the geometry of the Cu(II) ion is distorted tetrahedron. In further work surface-anchored mixed amino acid complexes were prepared. Three synthesis methods were elaborated giving a large number of catalysts. The central ions were Cu(II), Co(II), Fe(III) and Ni(II), the ligands were C- or N-protected histidine and tyrosine, or histidine and cysteine, or histidine and cystine or cysteine and cystine and the supports were the same as before. Many coordination modes were observed and it was found that the catalytic activities of the substances largely depended on the method of preparation as well. In many cases substantial SOD activity could be measured

Covalently immobilized, silica gel or resin-supported C-protected cysteine or cystine Fe and Ni complexes - synthesis and structural characterization with FT-IR spectroscopy

In this work the syntheses of covalently grafted C-protected Fe(III)− or Ni(II)−L-cysteine and Fe(III)− or Ni(II)−L-cystine complexes onto a surface-modified silica gel or Merrifield’s resin are described. Conditions of the syntheses were varied and the obtained structures were studied by classical analytical (titration) as well as spectroscopic (infrared, atomic absorption) methods. It was found that the sulphur atoms in the molecules acted as primary coordination sites, while the other coordinating groups varied depending on whether the complexes were formed under ligand-poor or ligand-excess conditions

Diurnal and seasonal changes in stem radius increment and sap flow density indicate different responses of two co-existing oak species to environmental stress

Using continuous monitoring of stem radius combined with sap flow measurements we assessed the effects of environmental conditions on tree radial growth and water status of two co- existing oak species ( Quercus petraea and Quercus cerris ) at high resolution time in growing seasons of 2008 and 2009. The forest (95–100 yr) is situated in a xeric site in the transition zone between forested and forest-steppe regions in north -eastern Hungary, Bükk mountains (47 o 90’N, 20 o 46’E, elevation 320–340 m a.s.l.). Weather conditio ns in the growing season of 2008 (total rainfall 354 mm, mean daily temperature 17.0 o C) was less extreme than in 2009 (total rainfall 299 mm, temperature 17.9 o C). Rainfall strongly determined the course of radi al growth increment in trees. Radial growth of trees was limited in 200 9 due to the drought in spring. The maximum radial increment of both species was achieved three weeks earlier (4 th week of June) than in 2008 (4 th week of July). We used dendrometer monitoring data for estimation of stem (tree) water deficit ( ∆ W) by measuring water-related changes in stem radiu s (Zweifel et al. 2005). The magnitude of tree water deficit variation ( ∆ W) was always smaller in Q. cerris than in Q. petraea. In contrast, Quercus cerris always exhibited larger daytime averages and maxima of sap flow density. In August of 2009 when drought became seve re there were larger increases in tree water deficit ( ∆ W) (50–55 %) in both species compared to July as it could be expected from the extent of decreases in sap flow density (24–28%). Our data suggested that due to the low SWC the transpiration was supported mainly from the inner w ater storage of trees during prolonged drought which resulted in high stem water deficit ( ∆ W)

Metallic Nanoparticles in Heterogeneous Catalysis

Heterogeneous catalysis is a chemical process achieved at solid–gas or solid–liquid interfaces. Many factors including the particle size, shape and metal-support interfaces can have significant influences on the catalytic properties of metal catalysts. The recent progress in the synthesis techniques and advanced characterization tools allow to understand the catalytic mechanisms at molecular level. In this Review, the size and shape dependent catalytic chemistry of metal nanoparticles and their electronic properties will be discussed. Then the unique catalytic chemistry at the metal-support interfaces will be discussed in details. Furthermore, the challenges of bimetallic nanoparticle catalytic chemistry will be discussed