Ultrasound enhanced reactions involving activated carbons as catalysts: synthesis of alpha,beta-unsaturated nitriles

alpha,beta-Unsaturated nitriles have been synthesized by sonochemical activ ated reactions of carbonylic compounds with malononitrile using two basic c arbons (Na+- and Cs+-Norit) as catalysts. The catalysts were characterized by thermal analysis, X-ray photoelectron spectroscopy and nitrogen adsorpti on isotherms. Under the experimental conditions, unsaturated nitriles can b e prepared with a high activity and selectivity. The role of alkaline promo ters (Na+ and Cs+) in the carbon has been studied. It is evidenced that the greater the basicity and the amount of catalyst, the higher is the convers ion. For comparison, the condensation reaction has also been carried out in a batch reaction system and the influence of the temperature in both (batc h and ultrasonic) systems has been studied. (C) 1999 Elsevier Science Ltd. All rights reserved.