Search results for "Microwave assisted"
showing 10 items of 34 documents
TREATMENT OF WEEE - WASTE OF ELECTRIC AND ELECTRONIC EQUIPMENTS - BY MICROWAVE - INDUCED PYROLYSIS
Economic and Technical Feasibility of Betanin and Pectin Extraction from Opuntia ficus-indica Peel via Microwave-Assisted Hydrodiffusion
2019
Investigating the feasibility of betanin and pectin extraction from Opuntia ficus-indica peel via microwave-assisted hydrodiffusion and gravity, this study identifies selected important economic and technical aspects associated with this innovative production route starting from prickly pear fruit discards. Which benefits would be derived from this process? Would production be limited to Opuntia-growing countries or, likewise to what happens with dried lemon peel chiefly imported from Argentina, would production take place abroad also? Can distributed manufacturing based on clean extraction technology compete with centralized production using conventional chemical processes?
Design of experiment approach for the optimization of polybrominated diphenyl ethers determination in fine airborne particulate matter by microwave-a…
2015
Abstract A sensitive and selective procedure for the determination of 12 polybrominated diphenyl ethers (BDE-28, BDE-49, BDE-47, BDE-66, BDE-100, BDE-119, BDE-99, BDE-155, BDE-154, BDE-153, BDE-139 and BDE-183) in airbone particulate matter (PM2.5) at trace level has been developed. The proposed method includes extraction PM2.5-bound PBDEs by microwave-assisted extraction (MAE) followed by gel permeation chromatography (GPC) clean-up and determination by GC-MS/MS using a programmed temperature vaporizer (PTV) in large volume injection (LVI) mode to introduce the sample to the chromatographic system. A design of experiment (DoE) approach was used for the optimization of large volume injectio…
Efficiency of the microwave-assisted extraction of hydrocarbons and pesticides from sediments
1997
Abstract A mixture of toluene and water is proposed for the microwave-assisted extraction of organic pollutants, hydrocarbons and pesticides, from marine sediments. The effect of experimental conditions, such as microwave power and irradiation time, on the extraction of linear, unresolved and polycyclic aromatic hydrocarbons as well as PCBs and DDTs has been evaluated using real marine sediment samples. Values found by Soxhlet and ultrasonic extraction were employed to evaluate the efficiency of the microwave-assisted extraction. Analytical determinations were carried out by gas chromatography using FID, ECD and MS detectors. For 2 g of a dry sediment, an extraction time of 6 min with 10 ml…
A novel radiation exposure control apparatus for microwave assisted chemical reactions
2004
AbstractA radiation exposure control apparatus is used for microwave (2.45 GHz) treatment of chemical reactions in controlled and reproducible conditions. A spectrophotometer has been interfaced with the microwave set-up in order to monitor the reaction evolution in situ. Both numerical and experimental dosimetries are carried out in order to evaluate the field distribution within the sample. Finally, particular working conditions are suggested.
Current and New Insights in the Sustainable and Green Recovery of Nutritionally Valuable Compounds from Stevia rebaudiana Bertoni.
2015
International audience; The South American plant Stevia rebaudiana Bertoni is a great source of noncaloric sweeteners (steviol glycosides), mainly concentrated in its leaves, but also has important antioxidant compounds (vitamin C, polyphenols, chlorophylls, and carotenoids) and other important macro- and micronutrients such as folic acid and all of the essential amino acids except tryptophan. Traditionally, conventional methods have been used to recover nutritionally valuable compounds from plant food matrices. However, nowadays, the need for obtaining greener, sustainable, and viable processes has led both food industries and food scientists to develop new processes in full correspondence…
Microwave-assisted tandem cross metathesis intramolecular Aza-Michael reaction: an easy entry to cyclic beta-amino carbonyl derivatives.
2007
Hoveyda−Grubbs catalyst in combination with BF3·OEt2 efficiently promotes tandem cross metathesis intramolecular aza-Michael reaction between enones and unsaturated carbamates resulting in the creation of β-amino carbonyl units. The use of microwave irradiation dramatically accelerates the process, enhancing the synthetic utility of this methodology for the preparation of these types of derivatives. When enantiomerically enriched α-branched amines were used as starting materials, the process was also very efficient, although with modest selectivity in the newly created stereocenter. The use of microwave irradiation led to an interesting effect, inverting the selectivity in the addition proc…
A novel synthetic approach to pyran-2,4-dione scaffold production: Microwave-assisted dimerization, cyclization, and expeditious regioselective conve…
2020
Abstract Here, we report a novel, green, simple, low-cost, and rapid methodology for the high-yield production of pyran-2,4-dione scaffolds under microwave irradiation. Regio- and stereoselective conversions of β-diketone systems into β-enaminones were achieved using 18 primary amines and four amino acid esters. Microwave-assisted further cyclization of 3-(β-substitutedvinyl)-6-phenyl-pyran-2,4-dione into 3-benzoyl-4,7-diphenyl-2H,5H-pyrano[4,3-b]pyran-2,5-dione via reaction with ethyl benzoyl acetate.
Microwave-assisted synthesis of novel cyclodextrin–cucurbituril complexes
2011
Microwave irradiation was successfully used in order to obtain stable supramolecular aggregates between cyclodextrins and cucurbiturils, without the participation of any long-chain common ‘molecular thread’ guest. These aggregates were characterised by means of various different techniques, namely NMR, thermogravimetry, polarimetry and ESI-MS. Cross-analysis of experimental data allowed us to obtain insights on the stoichiometries of the composites and their thermal stabilities. The possible structures of the composites are briefly discussed, as well as the actual nature of their intrinsic stability.