The Influence of Sonication on the Palladium-Catalyzed Dehydrogenation of Tetrahydronaphthalene

The dehydrogenation of tetrahydronaphthalene to naphthalene using 3% Pd/C in diethylene glycol (digol) under the influence of sonication is reported. The conventional reaction in digol at 200°C reached 55% conversion in 6 h, whereas using sonication at 180°C, complete reaction could be achieved in the same time. Pulsed ultrasound (at 50% cycle) was as effective as continuous sonication. The activity of the catalyst in the absence of sonication fell as the reaction proceeded but could be revitalised by applying ultrasound. Sonication had a much smaller effect on the reaction performed in triethylene glycol dimethyl ether.