Chemical Engineering Seminar
Abstract
Sonochemistry, enabled by ultrasound irradiation (20 kHz to 1000 kHz), is a promising technology for sustainable chemical synthesis because it uses water as a solvent, electricity as a power source, and avoids waste generation. Ultrasound irradiation creates reactive environments like hot spots, free radicals, shock waves, and defected surfaces, that otherwise do not form under nominally ambient conditions. Despite decades of work, there is significant debate about which aspects of the reactive environment enable selective chemical conversion. Furthermore, reaction mechanisms at the molecular scale remain poorly understood. Such mechanistic understanding is needed to increase selectivity. Using cavitation and first principles models that are paired with experiments, we show that the origin of selective chemical conversion is not pyrolysis reactions in hot spots, but free radical reactions occurring under ambient conditions. Furthermore, we use kinetic theories to construct mechanisms of sonochemical reactions and draw analogies with radical-mediated reactions that occur in atmospheric chemistry contexts. This mechanistic understanding is used to explain how pH dictates the selectivity of aldehyde oxidation reactions, even in catalyst-free environments. Finally, we discuss ongoing efforts related to the application of these findings for the sustainable synthesis of pharmaceutical intermediates.
Bio
Tej has been a tenure-track Assistant Professor at Nanyang Technological University, Singapore since Dec. 2019. He obtained his PhD in chemical engineering from Purdue University in Dec. 2017 (advisor: Prof. Jeffrey Greeley) and thereafter completed his postdoctoral training at Stanford University (advisor: Dr. Frank Abild-Pedersen). His group employs first principles methods and kinetic modelling to understand how catalysts operate at the atomic scale. In addition to managing his research programme, Tej is a Faculty Fellow of the NTU Honors College and the Director of the undergraduate programme in chemical and biomolecular engineering. Tej has received the Outstanding Young Principal Investigator of the AIChE, Singapore Local Section (2022) and the Nanyang Education Award (2022) for excellence in teaching. Tej holds early career advisory board roles in the Journal of Catalysis, ChemSusChem, and Applied Catalysis A: General.