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Easy Separation (easy + separation)
Selected AbstractsIn Situ Synthesis, Characterization of SiPMo-X, and Different Catalytic Properties of SiPMo-X and SiPW-XEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2006Chunfeng Shi Abstract SBA-15 frameworks with encapsulated Keggin type heteropolyacids (HPAs) were synthesized in situ under strongly acidic conditions (pH,<,0). During the hydrolysis of tetraethyl orthosilicate (TEOS), a P- and a Mo source were added into the initial sol,gel system to form Keggin type HPAs. The texture of the final products was studied by the N2 adsorption,desorption isotherms and transmission electron microscopy (TEM), and their structure was systematically characterized by X-ray diffraction (XRD), UV/Vis diffuse reflectance- (DRS), infrared- (IR), and 31P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. Characterization results suggest that the samples show very ordered hexagonal mesostructure, and the HPAs that are incorporated into the framework of meso-silica are insoluble during catalysis. Results of catalytic tests indicate that the materials demonstrated catalytic activity comparable with or even surpassing those of the bulk HPAs in catalytic tests implementing chemical reactions of bulky molecules (1,3,5-triisopropylbenzene cracking, esterification of benzoic acid with tert -butyl alcohol, and 2,3,6-trimethylphenol hydroxylation with H2O2). Additionally, some other properties, such as easy separation and stability when recycled, ensure their potential applications in the chemical industries. Here, we report not only the in situ synthesis and characterization of SiPMo-X, but also the difference in the catalytic properties of SiPMo-X and SiPW-X. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Tris(perfluoroalkyl)silyl Entities as Unexpectedly Potent Tags for the Noncovalent Immobilization of Catalysts by Fluorous,Fluorous Interactions: Application to the Synthesis of Several Perfluoro-Tagged LigandsHELVETICA CHIMICA ACTA, Issue 5 2005Vasyl Andrushko Unexpectedly high retention times were obtained in HPLC investigations for compounds equipped with (C8F17CH2CH2)3Si tags on C8F17 -modified silica gel (Fig.,4). Hence, these tags have a high potential for the noncovalent immobilization of catalysts to be applied in organic solvents, allowing for an easy separation and re-use of the catalyst by filtration and reapplication. The tris(perfluoroalkyl)silyl tag could be incorporated in a straightforward manner into ligands as demonstrated by the synthesis of several prominent classes of ligands (Schemes,4,6). [source] Multicomponent Reactions of 1,3-Cyclohexanediones and Formaldehyde in Glycerol: Stabilization of Paraformaldehyde in Glycerol Resulted from using Dimedone as SubstrateADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010Minghao Li Abstract Glycerol has proved to be an effective promoting medium for many multicomponent reactions of 1,3-cyclohexanediones and formaldehyde. Styrenes, amines, 2-naphthol, 4-hydroxy-6-methyl-2-pyrone and 4-hydroxy-1-methyl-2-quinolone could easily react with 1,3-cyclohexanediones and paraformaldehyde in glycerol under catalyst-free conditions to afford a variety of complex skeletons in fair to excellent yields. In these reactions, glycerol not only showed a significant promoting effect on the reaction yields but also endowed the reaction system with many typical properties of green chemistry, such as cheap, renewable, recyclable and biodegradable solvent, good safety and easy separation of product. The promoting effect of glycerol for the three-component reaction of styrene, dimedone and paraformaldehyde could be attributed to a restricted formation of the methylene intermediate in glycerol. During the reaction, a physical shell, which is mainly composed of a by-product generated in the beginning of the reaction, might be formed in the surface of paraformaldehyde and plays a key role in controlling the formation of the intermediate by means of restricting the decomposition of paraformaldehyde. [source] Facile Synthesis of Enantiopure 4-Substituted 2-Hydroxy-4- butyrolactones using a Robust Fusarium LactonaseADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009Bing Chen Abstract A facile chemo-enzymatic process has been developed for producing stereoisomers of 4-substituted 2-hydroxy-4-butyrolactones with good to excellent enantioselectivity. This process involves an easy separation of the diastereoisomers by column chromatography and efficient enzymatic resolution by whole cells of Escherichia coli JM109 expressing Fusarium proliferatum lactonase gene. This biocatalyst shows strong tolerance towards different substrate structures and at least three out four possible isomers could be obtained in excellent enantiomeric purity. Different substrate concentrations (10,mM,200,mM) were examined, giving a substrate to catalyst ratio of up to 26:1. This general and efficient enzymatic process provides access to stereoisomers of 4-substituted 2-hydroxy-4-butyrolactones readily and cost-effectively. The stereochemical assignments were conducted systematically based on NMR, X-ray diffraction and circular dichroism, leading to further understanding of the enzyme's stereoselectivity. [source] COVALENT IMMOBILIZATION OF INVERTASE ON CHEMICALLY ACTIVATED POLY (STYRENE-2-HYDROXYETHYL METHACRYLATE) MICROBEADSJOURNAL OF FOOD BIOCHEMISTRY, Issue 3 2008HAYDAR ALTINOK ABSTRACT A carrier for invertase enzyme was synthesized from styrene (S) and 2- hydroxyethyl methacrylate (HEMA) in the form of microbeads. These poly (styrene-2-hydroxyethyl methacrylate), P(S-HEMA) microbeads were activated by epichlorohydrin (ECH) treatment for covalent immobilization. The free and immobilized invertase were assayed in the hydrolysis of sucrose to glucose, and the obtained results were compared. The optimum pH was 4.5 for free and 5.5 for immobilized invertase. The optimum temperature of invertase shifted from 45C to 55C upon immobilization. For free and immobilized enzymes, kinetic parameters were calculated as 4.1 × 10,3 mol L,1and 9.2 × 10,3 mol L,1for Km, and 6.6 × 10,2 mol L,1 min,1and 4.1 × 10,1 mol L,1 min,1for Vmax, respectively. After 1 month of storage at 4C, free enzyme retained 36% of its initial activity, while for the ECH-activated P(S-HEMA) immobilized enzyme, P(S-HEMA)-E, this value was observed as 67%. In repeated batch use, i.e., 20 times in 3 days, 78% retention of the initial activity was observed for P(S-HEMA)-E system. PRACTICAL APPLICATIONS Immobilization of enzymes are very important for many industrial applications, e.g., food, medicine, pharmacology, etc. Invertase converts sucrose to glucose and fructose, which have wide applications in food industry especially as sweeteners. Glucose,fructose mixture has much lower crystallinity compared to sucrose and therefore used in the production of noncrystallizing jams and creams. They are also used as liquid sweeteners. Immobilization enables repeated use, provides significant reduction in the operation costs, facilitates easy separation and speeds up recovery of enzyme and extends the stability of enzyme by protecting the active material from deactivation. Industrial application of immobilized invertase may decrease the production cost of glucose,fructose mixture because it could be used repeatedly for long periods. Although invertase is not a very expensive enzyme, the technique can also be applied to expensive ones for biotechnological productions. [source] PURIFICATION OF AMYLASE FROM TILAPIA BY MAGNETIC PARTICLEJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 1 2010MING CHANG WU ABSTRACT Recent development in magnetic carrier technology involves the use of nonmagnetic substrates attached to superparamagnetic particles forming functionally modified magnetic support to isolate a particular enzyme in a controllable magnetic field. In this study, the superparamagnetic particles were modified by epichlorohydrin and other agents to cross-link with starch to form the purification support. This affinity support was able to bind the amylase and was used in the purification of amylase from Taiwan tilapia. After ammonium sulfate precipitation of amylase from Taiwan tilapia, the modified superparamagnetic particles were able to purify the crude amylase by 20.78-fold with recovery of activity of 75.6%. The molecular weight of the amylase was estimated to be 66.1 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Both crude and purified amylase reached an optimum at a pH of 8.0 and temperature of 50C, and the enzyme was stable between 20 and 50C. PRACTICAL APPLICATIONS Because of the rapid development of high technology such as carrier supports for enzyme purification, the development, research and application of magnetic carriers are timely needed. The present study demonstrated that the affinity superparamagnetic particles could be used as a carrier support to absorb and purify the amylase and that technology of affinity purification can be widely used in protein purification. Compared with the traditional chromatography used in the purification of proteins, this novel affinity superparamagnetic particle technology is rapid, has low operation cost, requires simple facilities, and involves easy separation and recovery of the enzymes. [source] Preparation of polymer-supported polyethylene glycol and phase-transfer catalytic activity in benzoate synthesisAICHE JOURNAL, Issue 3 2010Baojiao Gao Abstract The crosslinked polymeric microspheres (GMA/MMA) of glycyl methacrylate (GMA) and methyl methacrylate (MMA) were prepared by suspension polymerization. Polyethylene glycol (PEG) was grafted on GMA/MMA microsphers via the ring-opening reaction of the epoxy groups on the surfaces of GMA/MMA microspheres, forming a polymer-supported triphase catalyst, PEG-GMA/MMA. The Phase-transfer catalytic activity of PEG-GMA/MMA microspheres was evaluated using the esterification reaction of n -chlorobutane in organic phase and benzoic acid in water phase as a model system. The effects of various factors on the phase transfer catalysis reaction of liquid,solid,liquid were investigated. The experimental results show that the PEG-GMA/MMA microspheres are an effective and stable triphase catalyst for the esterification reaction carried out between oil phase and water phase. The polarity of the organic solvent, the ratio of oil phase volume to water phase volume and the density of the grafted PEG on PEG-GMA/MMA microspheres affect the reaction rate greatly. For this investigated system, the solvent with high polarity is appropriate, an adequate volume ratio of oil phase to water phase is 2:1, and the optimal PEG density on the polymeric microspheres is 15 g/100 g. Triphase catalysts offer many advantages associated with heterogeneous catalysts such as easy separation from the reaction mixture and reusability. The activity of PEG-GMA/MMA microspheres is not nearly decreased after reusing of 10 recycles. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Flocculation, adhesion and biofilm formation in yeastsMOLECULAR MICROBIOLOGY, Issue 1 2006Kevin J. Verstrepen Summary Yeast cells possess a remarkable capacity to adhere to abiotic surfaces, cells and tissues. These adhesion properties are of medical and industrial relevance. Pathogenic yeasts such as Candida albicans and Candida glabrata adhere to medical devices and form drug-resistant biofilms. In contrast, cell,cell adhesion (flocculation) is a desirable property of industrial Saccharomyces cerevisiae strains that allows the easy separation of cells from the fermentation product. Adhesion is conferred by a class of special cell wall proteins, called adhesins. Cells carry several different adhesins, each allowing adhesion to specific substrates. Several signalling cascades including the Ras/cAMP/PKA and MAP kinase (MAPK)-dependent filamentous growth pathways tightly control synthesis of the different adhesins. Together, these pathways trigger adhesion in response to stress, nutrient limitation or small molecules produced by the host, such as auxin in plants or NAD in mammals. In addition, adhesins are subject to subtelomeric epigenetic switching, resulting in stochastic expression patterns. Internal tandem repeats within adhesin genes trigger recombination events and the formation of novel adhesins, thereby offering fungi an endless reservoir of adhesion properties. These aspects of fungal adhesion exemplify the impressive phenotypic plasticity of yeasts, allowing them to adapt quickly to stressful environments and exploit new opportunities. [source] ChemInform Abstract: Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones Using Ce(SO4)2,SiO2 as a Heterogeneous and Recyclable Catalyst.CHEMINFORM, Issue 40 2010Wen Pei Abstract Compared with the classical Biginelli reaction, the presented new method has the advantages of better product yields, short reaction time, easy separation and tolerance towards various functional groups. [source] Supercritical Carbon Dioxide-Induced Phase Changes in (Ionic Liquid, Water and Ethanol Mixture) Solutions: Application to Biphasic Catalysis.CHEMPHYSCHEM, Issue 5 2003Vesna Najdanovic-Visak The best of both worlds: Phase changes in ionic liquid + water systems, induced by addition of ethanol and supercritical carbon dioxide, allow reaction cycles to proceed as depicted, combining the high rates of one-phase conditions with easy separation of products; characteristic of biphasic catalysis. The (usually slow) epoxidation of isophorone by hydrogen peroxide, catalysed by sodium hydroxide, was rapidly carried out in these conditions, with complete recovery of the reaction product by supercritical CO2 decompression. [source] MCM-41 Bound Ruthenium Complex as Heterogeneous Catalyst for Hydrogenation I: Effect of Support, Ligand and Solvent on the Catalyst PerformanceCHINESE JOURNAL OF CHEMISTRY, Issue 7 2006Ying-Min Yu Abstract The functionalized MCM-41 mesoporous bound ruthenium complex was synthesized and characterized using elemental analysis, atomic absorption spectrophotometer, BET, XRD and FTIR. Hydrogenation of carbon dioxide to formic acid was investigated over these catalysts under supercritical CO2 condition. The effect of reactant gas partial pressure, supports, solvents and ligands on the synthesis of formic acid was studied. These factors could influence the catalyst activity, stability and reuse performance greatly and no byproduct was detected. These promising catalysts also offered the industrial advantages such as easy separation. [source] | ||||||||||||||||||||||