A Sustainable-by-Design Process for the Selective Photooxidation of Ethylbenzene in a Scalable Agitated Baffle Reactor

This study presents a sustainable-by-design approach
for the selective photooxidation of ethylbenzene under continuous
flow conditions using sodium anthraquinone-2-sulfonate (SAS) as a
water-soluble photocatalyst. The reaction was conducted in a scalable
agitated baffle reactor (SABRe) under ultraviolet (UV)-A irradiation
(365 nm), enabling enhanced mixing, illumination, and gas−liquid
contact. To systematically optimize the process, a four-factor central
composite design based on response surface methodology (RSM) was
employed, evaluating the influence of catalyst loading, liquid and gas
flow rates, and light intensity. The study revealed that oxygen mass
transfer from air is a key limiting factor, which was successfully
addressed by implementing counter-current gas−liquid flow and
increased agitation speeds. These modifications led to a significant
improvement in ethylbenzene conversion and selectivity toward acetophenone. The SABRe reactor achieved a space−time yield
(STY) of 14.8 g L−1 h−1, representing a three fold improvement over the conventional microchannel reactor configuration. Under
optimized conditions, an extended 8 h continuous operation processed 1.44 L of feed solution, delivering an 87% isolated yield with
≥98% product purity. The modular and scalable nature of the SABRe platform, combined with efficient process intensification
strategies, underscores its potential for sustainable chemical manufacturing and future scale-up via a numbering-up approach for
photocatalytic C−H functionalization using our intensified continuous flow technology.