Activated solid-fluid reactions in ultrasound reactors

Reactions of solids with liquid reactants can be accelerated in ultrasound fields. Transient bubbles create liquid microjets and increase the amount of dislocations on metallic surfaces. Dynamic experiments and models for the activation of magnesium turnings in the Grignard reaction of chlorobutane and phenylchloride show a relation between the degree of activation and the local energy distribution in the ultrasound field. The local action of transient bubbles and microjets in cavitating sound fields was measured and calculated. This allows the prediction of reaction rates, optimum process parameters and the behavior of different metals in noncatalytic as well as catalytic solid-fluid reactions. A further optimization of reaction rates and safer production of organometallic compounds was reached by applying mixtures of calcium donated magnesium. These alloys are very brittle and can be cleaved under ultrasound. High reaction rates with a variety of organic chlorides and phenyl fluoride are observed with sonicated magnesium calcium alloys. (C) 1999 Elsevier Science Ltd. All rights reserved.