A meso-scale ultrasonic milli-reactor enables gas–liquid-solid photocatalytic reactions in flow

Zhengya Dong, Stefan D.A. Zondag, Matthias Schmid, Zhenghui Wen, Timothy Noël (Corresponding author)

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32 Citations (Scopus)
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The handling of solid reagents, catalysts and by-products is a daunting challenge in continuous-flow micro- and milli-reactors. Suspensions tend to settle over time leading to irrevocable clogging of the reaction channels. Herein, we describe our efforts to develop an ultrasonic milli-reactor which can handle such challenging solid-containing transformations. The reactor consists of a Langevin-type transducer, a sonotrode and an irradiating cylinder, on which a coiled glass capillary (12.88 mL) was attached. The ultrasonic milli-reactor was combined with an LED illuminating box and its efficacy was showcased in the photocatalytic aerobic oxidation of benzyl alcohol enabled by TiO2 particles exposed to UV-A irradiation. Ultrasound irradiation generates cavitation bubbles and causes a vigorous oscillation of both the cavitation and the Taylor bubbles. This improves the liquid mixing, the gas–liquid mass transfer and ensures resuspension of the settled particles. Moreover, these effects enhance the photon absorption by the semiconductor catalyst, which has an overall positive effect on the photocatalytic transformation.

Original languageEnglish
Article number130968
Number of pages10
JournalChemical Engineering Journal
Publication statusPublished - 15 Jan 2022

Bibliographical note

Funding Information:
T.N. and Z. D. are grateful to receive funding from the European Union for the FETopen project FLIX (Grant No. 862179 ). Z.W. acknowledges support from the China Scholarship Council (CSC) and M.S. received a Leopoldina fellowship (Grant No. LPDS 2019-08 ) to sponsor his postdoctoral stay. Z. D. acknowledges funding from Chemistry and Chemical Engineering Guangdong Laboratory (Grant No. 2011009 ).


  • Clogging
  • Flow chemistry
  • Heterogeneous photocatalysis
  • Solid handling
  • Taylor flow
  • Ultrasound


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