Process microwave

C. Shibata and H. Tamai, Proceedings of the International Conference on High Frequeny j Microwave Processing and Heating, Tokyo, Japan, 1989, pp. 5.2.1-5.2.5. 

W. H. Sutton and co-workers, eds.. Microwave Processing of Materials Materials Research S ociety Proceedings, Vol. 124, Pittsburgh, Pa., 1988. 

Plastics Southern Africa 28,No.5,Nov.l998,p.l8/22 BACKGROUND TO MICROWAVE PROCESS FOR RECOVERY OF PMMA WASTE... 

The microwave technique is widely applied to process polymer materials, e.g. in microwave cure [429], Microwave processing is a developing technology. 

A particularly difficult problem in microwave processing is the correct measurement of the reaction temperature during the irradiation phase. Classical temperature sensors (thermometers, thermocouples) will fail since they will couple with the electromagnetic field. Temperature measurement can be achieved either by means of an immersed temperature probe (fiber-optic or gas-balloon thermometer) or on the outer surface of the reaction vessels by means of a remote IR sensor. Due to the volumetric character of microwave heating, the surface temperature of the reaction vessel will not always reflect the actual temperature inside the vessel [7]. 

Scheme 4.30 Hydrodechlorination of chlorobenzene using active flow cells in a continuous-flow microwave process.

An even simpler protocol for performing nucleophilic substitutions (aminations) and Suzuki reactions in one pot was reported by the Organ group for the generation of a 42-member library of styrene-based nicotinic acetylcholine receptor (nAChR) antagonists (Scheme 6.21) [49]. After considerable experimentation, the authors found that simultaneous nucleophilic displacement and Suzuki coupling could be carried out very effectively by charging the microwave process vessel with the palladium catalyst (0.5 mol% palladium-on-charcoal), the boronic acid [R1B(OH)2], the... 

Most importantly, microwave processing frequently leads to dramatically reduced reaction times, higher yields, and cleaner reaction profiles. In many cases, the observed rate enhancements may be simply a consequence of the high reaction temperatures that can rapidly be obtained using this non-classical heating method, or may result from the involvement of so-called specific or non-thermal microwave effects (see Section 2.5). 

High power microwaves are generated by vacuum tubes. The magnetron and klystron are the most commonly used tubes for the generation of continuous waves power for microwave processing. Power is normally launched from the microwave tube into a transmission line or waveguide, where it travels to a load or termination such an antenna or a microwave heating applicator. 

J. Wei,V. Adegbite, Mater. Res. Soc. Symp. Proc. 1994, 347 (Microwave Processing of Materials IV), 669, and references cited therein. 

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