On Modified Silicas

In the present work, the Jacobsen s catalyst was immobilized inside highly dealuminated zeolites X and Y, containing mesopores completely surrounded by micropores, and in Al-MCM-41 via ion exchange. Moreover, the complex was immobilized on modified silica MCM-41 via the metal center and through the salen ligand, respectively. cis-Ethyl cinnamate, (-)-a-pinene, styrene, and 1,2-dihydronaphtalene were used as test molecules for asymmetric epoxidation with NaOCl, m-CPBA (m-chloroperoxybenzoic acid), and dimethyldioxirane (DMD) generated in situ as the oxygen sources. 

Air (CDDs) Collection of sample onto glass fiber filter/polyurethane foam cartridge addition of internal standard Soxhlet extraction with toluene volume reduction clean-up and fractionation on Florisil , elutiion with toluene/diethylether, evaporation and redissollution in cyclohexane clean-up on modified silica gel using HPLC and hexane/diethyl ether volume reduction HRGC/LRMS (EI/SIM) HRGC/LRMS (NCI/SIM) 0.1-1 pg/m3 0.2-3 pg/inj (0.01-0.1 pg/m3) 80-122 86-102 Oehme et al. 1986... 

The immobilization of phase transfer catalysts on solid substrates allows a clean reaction with no contamination of the products by the catalyst. Insoluble polystyrene matrices have been used as a solid support. The polymer matrix does not affect the velocity of the reaction, apart from steric hindrance with respect to the reagents. In the case of immobilization on modified silica the active centre is linked to the support by an alkyl chain of variable length. This length strictly determines the adsorption capacity of the polar support, which then controls the rate of reaction. A three-phase catalytic system is set up. Two distinct phases, containing reagents, come into close... 

Scheme 71 Preparation of heterogeneous neodymium-based diene polymerization catalysts on modified silica (adopted from [306])...

T. Luts, H. Papp, Novel ways of Mn-salen complex immobilization on modified silica support and their catalytic activity in cyclooctene epoxidation, Kinet. Catal. 48 (2007) 176. 

Modified Silica Surfaces. On modified silica surfaces the monomer and excimer excitation spectra of Py were found to be... 

In summary, considering the environmental issues as well as the process optimization that requires the substitution of toxic catalysts by more friendly solid catalysts, we have shown new catalysts based on modified silica that can efficiently catalyze transesterification. This reaction was carried out by an ecofriendly technology as the production of effluents harmful to the environment is avoided. 

Multiple forms of soybean lipoxygenase-1 HPLC cation exchange chromatography on modified silica gel Aoshima [356]... 

Chapter 3 presents data about enantioselective hydrogenation reactions on metal catalysts supported on chiral carriers. Discussed are palladium supported on modified silica gels, effective chiral colloidal catalysts, template catalytic systems, palladium-silk, palladium-wool, and palladium polypeptide catalysts. 

A number of new acetonation conditions have been examined. Use of acetone in the presence of K 10 clay gave the 2,3-0-isopropylidene derivatives of d-ribofuranose and L-rhamnopyranose and the expected di-O-isopropylidene derivatives of D-xylose, D-glucose, D-galactose and D-mannose in excellent yields. Good to excellent yields of the expected acetonides of methyl a-D-manno-, a-D-gluco-, and a-D-galacto-pyranoside as well as of D-mannose have been obtained with acetone and titanium(IV) chloride supported on modified silica gel. H3PM012O40 was the most active of 18 heteropolyacids examined as catalysts in the acetonation of L-sorbose. ... 

Hydrodehalogenation of p-BT in the presence of IRu2< M -S04)4(H20)jI immobilized on modified silica gels ... 

As is seen in Table 1, catalysts on the basis of Ru tetrasulfote immobilized on modified silica gels catalyze p-BT hydrogenolysis with close rates (0.27-0.31 mole/g-atom Ru-min). Evidently, the activity of the resulting met -complex systems does not depend on the nature of the group that is graft to silica gel. 

A first experimental set up, devised to investigate polymer melts flowing on modified silica surfaces, is schematically presented in figure 2. 

De Luca G,Tocci E and Drioli E (2005), Quantum and molecular mechanics calculations on modified silica nano ring , J. Mol. Struct., 739,163-172. 

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