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Microwave Reactor (microwave + reactor)
Selected AbstractsSynthesis of Zirconia Nanoparticles in a Continuous-Flow Microwave ReactorJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2008Federica Bondioli Monodispersed zirconia colloidal spherical nanoparticles were synthesized from the hydrolysis and condensation of tetra- n -propylzirconate by using a continuous microwave synthesis process. The flow rate was varied from 50 to 100 mL/min in order to establish the optimum conditions required to obtain unagglomerated zirconia nanopowders. The results were compared with those obtained in batch systems. In particular as the flow rate is decreased from 100 to 50 mL/min the particle became spherical with a mean particle size of about 100 nm. [source] Multimode Microwave Reactor for Heterogeneous Gas-Phase CatalysisCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2003H. Will In order to investigate heterogeneously catalyzed gas-phase reactions, e.g. the oxidation of propane, on heterogeneous catalysts in the multimode microwave field, a microwave device was modified to achieve an adequate field homogeneity and a continuous power control. To date, no similar apparatus has been described in the literature. The presented microwave apparatus is suitable for carrying out reproducible catalytic investigations in the multimode microwave field. [source] Rapid solid-phase peptide synthesis using thermal and controlled microwave irradiationJOURNAL OF PEPTIDE SCIENCE, Issue 10 2006Bernadett Bacsa Abstract A rapid and efficient microwave-assisted solid-phase synthesis method is described for the preparation of the nonapeptide WDTVRISFK, using conventional Fmoc/But orthogonal protection strategy. The synthesis protocol is based on the use of cycles of pulsed microwave irradiation with intermittent cooling of the reaction during the removal of the Fmoc protecting group and during the coupling. The desired nonapeptide was obtained in highest yield and purity by employing MicroKan technology. The chemical reactions were carried out in a single-mode microwave reactor, equipped with a fiber-optic probe to monitor the reaction temperature continuously. Copyright © 2006 European Peptide Society and John Wiley & Sons, Ltd. [source] Single-Mode Microwave Ovens as New Reaction Devices: Accelerating the Living Polymerization of 2-Ethyl-2-OxazolineMACROMOLECULAR RAPID COMMUNICATIONS, Issue 22 2004Frank Wiesbrock Abstract Summary: The ring-opening cationic polymerization of 2-ethyl-2-oxazoline was performed in a single-mode microwave reactor as the first example of a microwave-assisted living polymerization. The observed increase in reaction rates by a factor of 350 (6 h,,,1 min) in the range from 80 to 190,°C could be attributed solely to a temperature effect as was clearly shown by control experiments and the determined activation energy. Because of the homogenous microwave irradiation, the polymerization could be performed in bulk or with drastically reduced solvent ratios (green chemistry). Monomer conversion, represented by the ratio ln{[M0]/[Mt]}, plotted against time for six temperatures in the range from 80 to 180,°C, and polymerization reaction vials, showing an increase in yellow color for those reactions performed (well) above and below 140,°C, indicating side reactions. [source] Microwave-Assisted Polymer Synthesis: State-of-the-Art and Future PerspectivesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2004Frank Wiesbrock Abstract Summary: Monomodal microwaves have overcome the safety uncertainties associated with the precedent domestic microwave ovens. After fast acceptance in inorganic and organic syntheses, polymer chemists have also recently discovered this new kind of microwave reactor. An almost exponential increase of the number of publications in this field reflects the steadily growing interest in the use of microwave irradiation for polymerizations. This review introduces the microwave systems and their applications in polymer syntheses, covering step-growth and ring-opening, as well as radical polymerization processes, in order to summarize the hitherto realized polymerizations. Special attention is paid to the differences between microwave-assisted and conventional heating as well as the "microwave effects". Results of search on number of publications on microwave-assisted polymerizations, sorted by year. [source] Microwave-Assisted Heterogeneous Cross-Coupling Reactions Catalyzed by Nickel-in-Charcoal (Ni/C)CHEMISTRY - AN ASIAN JOURNAL, Issue 3 2006Bruce Abstract A study involving the relatively rare combination of heterogeneous catalysis conducted under microwave conditions is presented. Carbon,carbon bond formation, including Negishi and Suzuki couplings, can be quickly effected with aryl chloride partners by using a base metal (nickel) adsorbed in the pores of activated charcoal. Aminations were also studied, along with cross-couplings of vinyl alanes with benzylic chlorides as a means to stereodefined allylated aromatics. Reaction times for all these processes are typically reduced from several hours to minutes in a microwave reactor. [source] | |||||||||||||