Ultrasound reactors

Pugin B (1987) Qualitative characterization of ultrasound reactors for heterogeneous sono-chemistry. Ultrasonics 25 49-55... 

Chemat et al. have reported several microwave reactors, including systems that can be used in tandem with other techniques such as sonication [68], and ultraviolet radiation [69]. With the microwave-ultrasound reactor, the esterification of acetic acid with n-propanol was studied along with the pyrolysis of urea. Improved results were claimed compared with those from conventional and microwave heating [68]. The efficacy of the microwave-UV reactor was demonstrated through the rearrangement of 2-benzoyloxyacetophenone to l-(2-hydroxyphenyl)-3-phenylpropan-l,3-dione [69]. 

A combination of different techniques can frequently improve yields of final compounds or synthetic conditions, for example a reunion of direct electrochemical synthesis and simultaneous ultrasonic treatment of the reaction system [715]. Reunion of microwave and ultrasonic treatment was an aim to construct an original microwave-ultrasound reactor suitable for organic synthesis (pyrolysis and esterification) (Fig. 3.7) [716], The US system is a cup horn type the emission of ultrasound waves occurs at the bottom of the reactor. The US probe is not in direct contact with the reactive mixture. It is placed a distance from the electromagnetic field in order to avoid interactions and short circuits. The propagation of the US waves into the reactor occurs by means of decalin introduced into the double jacket. This liquid was chosen by the authors of Ref. 716 because of its low viscosity that induces good propagation of ultrasonic waves and inertia towards microwaves. 

Ultrasound reactors are used quite often for the low-intensity treatment of solids in liquids. Examples of industrial-scale ultrasound reactors are the Reverbatory Ultrasonic Mixer with 16 kW total power input and 0.2 m3 min-1 flow rate, the... 

The implementation of in-line ultrasound for sample preparation in flow analysis is analogous to microwave or UV irradiation. The coiled reactor (or a mini-chamber) is immersed in a water bath to which ultrasound is applied. As mechanical waves are involved, the inner walls of the tubing should be thin and flexible to avoid wave damping, which would decrease the efficiency of the ultrasound. Alternatively, an ultrasound probe can be placed near the ultrasound reactor [143]. The use of an... 

One of the tested ultrasound reactors is a high-amplitude-high energy density conical reactor shown in Fig. 8.1.16 [21], The sound field is generated by a stepped... 

Horst C., Kunz U., Rosenplanter A., Hoffmann U. (1999) Activated Solid-Fluid Reactions in Ultrasound Reactors. Chem. Eng. Sci. 54 2849-2858... 

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