Search results for "support"

(Co)polymerization behavior of supported metallocene catalysts. I. Ligand and substituent effect

2005

Ethylene polymerization and its copolymerization with 1-hexene with a set of supported metallocene catalysts were studied. As a carrier, the complex of mag- nesium chloride with tetrahydrofuran, which was previously pretreated with a triiso- butylaluminium (TIBA), was used. The investigated metallocene compound differs in the metal type (Zr or Ti), the nature of the alkyl substituent in the cyclopentadienyl ring, and the type of ligand (Cp or Ind). The effect of catalyst composition on the anchored metal content, catalyst activity, comonomer reactivity, and polymer proper- ties was investigated. The results obtained with supported catalysts were compared with those obtained with their homog…

(Co)polymerisation Behaviour of Supported Metallocene Catalysts: Carrier Effect

2006

The polymerisation and copolymerisation of ethylene with 1-hexene over metallocene catalysts L 2 ZrCl 2 / MAO (L = Cp, n-BuCp, t-BuCp, i-PrCp, Me 5 Cp) supported on different types of carriers (MgCl 2 (MeOH) 6 or silica with CH 3 surface groups obtained in the sol-gel process) were studied. It was demonstrated that both the metallocene structure and the type of inorganic support affected catalyst activity and polymer properties such as melting point, molecular weight and molecular weight distribution. The metallocene structure also determined comonomer incorporation, both for homogeneous and supported catalytic systems. When a catalyst is anchored on a support, it becomes less effective at …

ChemInform Abstract: 1,5,7-Triazabicyclo[4.4.0]dec-1-ene (TBD), 7-Methyl-TBD (MTBD) and the Polymer-Supported TBD (P-TBD): Three Efficient Catalysts …

2010

Abstract The 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and its 7-methyl derivative (MTBD) have been proven to be of great synthetic utility as catalysts in the nitroaldol (Henry) reaction and for the addition of dialkyl phosphites to a variety of carbonyl compounds. The catalysts were in many cases superior to the parent tetramethylguanidine (TMG). In general the reaction proceeds in a few minutes at 0°C. The polymer-supported-TBD (P-TBD) was also proven to be an efficient promoter of the above cited nucleophilic additions.

Asymmetric Aldol Reaction with Polystyrene-Supported Proline-Based Catalysts

2009

Asymmetric aldol reaction in water catalyzed by polystyrene-supported proline

2007

Electrochemical behaviour of inorganic redox substances dispersed into Nafion® films

1999

Abstract The voltammetric response of a Nafion ® film deposited on an indium tin oxide (ITO) electrode was studied. It was observed that the response is affected by the thickness of the Nafion ® layer. Also, the voltammograms show differences depending on the concentration and composition of the supporting electrolyte solution. The ITO–Nafion ® system can be stabilised by repetitive cyclic voltammetry, and then the inner hydrogen reduction is not detected by electrochemical impedance spectroscopy. Different substances were dispersed into the Nafion ® matrix in order to study their electrochemical response.

1,5,7-Triazabicyclo[4.4.0]dec-1- ene (TBD), 7-Methyl-TBD (MTBD) and the polymer-supported TBD (P-TBD):Three efficient catalysts for the nitroaldol (H…

2000

Abstract The 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and its 7-methyl derivative (MTBD) have been proven to be of great synthetic utility as catalysts in the nitroaldol (Henry) reaction and for the addition of dialkyl phosphites to a variety of carbonyl compounds. The catalysts were in many cases superior to the parent tetramethylguanidine (TMG). In general the reaction proceeds in a few minutes at 0°C. The polymer-supported-TBD (P-TBD) was also proven to be an efficient promoter of the above cited nucleophilic additions.

New Perspectives in Polymer-Supported Peptide Synthesis

1982

Studien zum Vorgang der Wasserstoffübertragung, 41. Elektroreduktion von Acetophenon unter Mitwirkung optisch aktiver Leitsalze

1977

Die Anderung des Carbinol/Pinakol-Verhaltnisses2) (C/P) und der optischen Induktion bei der Elektroreduktion von Acetophenon mit (1 R, 2S)-N-(3-Cyanpropyl)-N-methylephedriniumbromid (1) und (1 R, 2 S)-N,N-Dimethylephedriniumbromid (2) als Leitsalze wird untersucht in Abhangigkeit: a) vom Potential (Tabelle 1), b) von der Stromdichte (Tabelle 2), c) von Pulsbedingungen (Tabelle 3), d) vom pH (Tabelle 4), e) von der Anwesenheit anderer Kationen (Tabelle 5), f) vom Losungsmittel (Tabelle 6), g) von der Temperatur (Tabelle 7) und h) von der Art des Elektrodenmaterials (Tabelle 8). — Es werden tensammetrische und cyclovoltammetrische Messungen durchgefuhrt. Die in trockenem Dimethylformamid erha…

An approach to polymer-supported triplet benzophenone photocatalysts. Application to sustainable photocatalysis of an α-diazocarbonyl compound

2013

Covalent immobilization of 4-hydroxybenzophenone on Merrifield resins affords new heterogeneous polymeric triplet photocatalysts. Their successful application in the intramolecular triplet-sensitized photolysis of a α-diazo β-keto ester has been achieved under sustainable criteria. Remarkably, the simple recovery and reuse for up to five sequential applications have been performed, although resulting in a slightly decreasing activity.