When sonochemistry meets heterogeneous photocatalysis: designing a sonophotoreactor towards sustainable selective oxidation

Abstract

Exploration of the synergistic effect in catalysis upon simultaneous utilization of two sources of power, ultrasound and light, is barely explored and remains a challenging issue. A crucial reason behind this is the difficulty in designing and constructing a well-defined sonophotoreactor capable of taking advantage of the benefits of combining sonochemistry and photochemistry. Herein, we present our successful reactor and a detailed study regarding how the utilization of ultrasonication can act as a process intensification tool for selective and partial photooxidation of a biomass derived model compound, benzyl alcohol. The main outcome was the enhanced selectivity in the case of sonophotocatalysis compared to photocatalysis. This selectivity was ascribed to the effects derived from the cavitation phenomena, leading to phenomena such as hot spot formation and jetting. Our study can act as guidance towards understanding the unique effects of ultrasound irradiation as a hybrid process intensification method (HPIM) towards application in more complex chemical reactions and manipulation of the nanocatalysts’ photoreactivity in catalytic valorization applications.