Search results for "Inorganic chemist"
showing 10 items of 7340 documents
Die Cooligomerisierung von butadien mit α-hydroxycarbonsäureestern
1977
Abstract Glycolic acid butyl ester as well as lactic acid ethyl ester react with butadiene in the presence of palladium(II) acetylacetonate and triphenylphosphine as catalyst. The main product is the 2-trans, 7-octadienyl ether of the hydroxy acid ester, which is formed in yields from 65 to 80% at room temperature.
Sol-gel entrapped chromium(VI): a new selective, efficient and recyclable oxidizing system
2001
Abstract The sol-gel entrapment of chromium(VI) within a silica matrix, obtained by oxidation with ozone of the corresponding entrapped chromium(III), was found to be an efficient and recyclable oxidizing system (at least up to 16 times) for benzylic alcohols. No leaching of chromium in solution was observed, which prevented any environmental pollution.
Dissociation-constants of metat-ion-complexes with alkaline phosphatase from pig kidney.
1976
Using metal-ion buffers it was possible to remove Zn2+, Mg2+ and Mn2+ ions of pig kidney alkaline phosphatase reversibly. The dissociation constants obtained are KEMg: 4 X 10(-7) M, KEMn: 4 X 10(-8) M and KEZn: 8 X 10(-13) M (22 degrees C, pH: 9.6, mu: 0.07).
Effect of hydrogen on the ethylene polymerization process over Ziegler-Natta catalysts supported on MgCl2(THF)2. I. Studies of the chain-transfer rea…
2000
The effect of hydrogen on the molecular weight of polyethylene obtained over vanadium catalysts (based on VCl4 and VOCl3) supported on MgCl2(THF)2 was studied and the results were compared to those obtained for similar titanium catalysts. It was confirmed that the dependencies of the transfer reaction on the hydrogen concentration are a half-order in all investigated systems. However, the transition metal of the catalytic site affects the ratio of the transfer rate with hydrogen to the propagation rate (ktr,H/kp) and the results showed that hydrogen is a more effective agent of polyethylene molecular weight control in vanadium-based systems as compared to the titanium catalyst. © 2000 John …
Nature of cobalt active species in hydrodesulfurization catalysis: combined support and preparation method effects
2007
Abstract Co/γ-Al2O3, Co/SiO2, Co/MCM-41, Co/ASA and Co/S2 (amorphous aluminosilicate with Al/Si = 0.13 and with Al/Si ≈ 2, respectively) were prepared by the method of wet impregnation and by the method of precipitation in the presence of sodium carbonate. The samples were characterised by XPS, XRD and TPR. The catalytic activity was tested in the hydrodesulfurization of thiophene using a continuous flow reactor. Among the wet impregnated catalysts those supported on the amorphous and ordered mesoporous silica exhibited higher HDS activity as compared to the alumina containing supports. Particularly, the use of the mesoporous, high surface area MCM-41 support, determined the best performing…
Combined effect of noble metals (Pd, Au) and support properties on HDS activity of Co/SiO2 catalysts
2009
Abstract Cobalt-based catalysts supported on different types of SiO 2 are studied in the hydrodesulfurization of thiophene. Amorphous silica and siliceous MCM-41 and HMS, characterized by different texture and surface acidity are used as carriers. The effects due to the modification of the support by impregnation with palladium precursor and to the co-impregnation of cobalt and gold are considered. The catalysts are characterized by N 2 physisorption (BET), XRD, TPR and XPS techniques. The use as supports of the ordered mesoporous silica with higher surface area with respect to amorphous silica, produces a better dispersion of the cobalt oxides particles. Moreover, the addition of palladium…
Deep oxidation of propane using palladium–titania catalysts modified by niobium
2008
Abstract Pd/TiO 2 catalysts modified by niobium have been prepared and tested for the complete oxidation of propane. The catalysts have been characterised by BET, XRD, laser Raman spectroscopy, XPS, DRS and TPR. The incorporation of niobium into Pd/TiO 2 catalysts resulted in a marked increase in the catalytic activity compared to the Nb-free Pd/TiO 2 catalysts, and the activity increased as the niobium and/or palladium loading increased. The addition of Nb significantly modified the nature of the palladium and niobium species. There was a marked increase in the oxygen mobility after niobium addition. This could not only promote the presence of palladium species in a totally oxidized state …
The Effect of Interferences on the Uptake of Heavy Metals by Sodium (iron) Titanates from Waste Water
2007
Sodium hexatitanate, sodium trititanate, sodium nonatitanate, and a new iron doped sodium nonatitanate were synthesized. Common interferences present in waste waters that hinder the removal of heavy metals by these ion exchangers were investigated. The presence of K+, Mg2+ and Ca2+ at 0.001-0.05 M concentration had minor effect on the amount of Pb2+, Cr3+, and Ni2+ uptake. EDTA on the other hand, interferes tremendously with the metal uptake. Both in ternary and in single system, the selectivity series is in the order: Pb2+>Cr3+>Ni2+. This order changed to Cr3+>Pb2+>Ni2+, in the presence of 0.001-0.1 M EDTA at pH 5.
Coordination-Induced Spin-State Switching with Nickel Chlorin and Nickel Isobacteriochlorin
2015
We present the first coordination-induced spin-state switching with nickel chlorin and nickel isobacteriochlorin. The spin-state switching was monitored by UV-vis spectroscopy and NMR titration experiments. The association constants (K1 and K2) and thermodynamic parameters (ΔH and ΔS) of the coordination of pyridine were determined. The first X-ray analyses of a paramagnetic nickel chlorin and a nickel isobacteriochlorin provide further information about the structure of the octahedral complexes. Nickel chlorin and even more pronounced nickel isobacteriochlorin exhibit stronger coordination of axial ligands compared to the corresponding nickel porphyrin and thus provide the basis for more e…
Ni(II) and Pd(II) complexes of camphor-derived diazadiene ligands: steric bulk tuning and ethylene polymerization
1998
Abstract Nickel(II) and palladium(II) centers were coordinated to a series of chiral 1,4-diazadiene ligands. The ligand backbones are camphor derivatives and the imine nitrogens are attached to independently varied 2- and 2,6-substituted aryl groups. Upon activation with methyl-aluminoxane, the dibromo nickel complexes polymerize ethylene and 1-hexene. The polymerization properties are dependent on the steric features of the aryl substituents on the imine nitrogens.