Performances of Homogeneous and Heterogenized Methylene Blue on Silica Under Red Light in Batch and Continuous Flow Photochemical Reactors

Maxime Lancel,Zacharias Amara,Marc Port,Catherine Gomez

doi:10.3389/fceng.2021.752364

Maxime Lancel, Zacharias Amara + Show 2 more

Open Access

https://doi.org/10.3389/fceng.2021.752364

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Abstract

Methylene blue was efficiently immobilized on silica micro- and nanoparticles by electrostatic interactions and the performances of the heterogenized photocatalysts were compared against the homogeneous conditions using the photooxidation of citronellol as a model reaction under red light, in a batch and a continuous flow photochemical reactor. In batch, the heterogeneous photocatalyst outperforms the homogeneous one, presumably due to kinetic and stability effects. The two catalytic systems are also compared in a flow reactor displaying improved mass transfer properties. We demonstrate that this results in a dramatic enhancement in photocatalyst stability, reactivity and productivity. This study highlights the importance of photocatalyst stability under homogeneous versus heterogenized conditions and in batch versus flow photochemistry.

Highlights

Visible-light photochemistry is a promising approach in the development of greener synthetic chemistry
Excited state chemistry allows for conventional reactions to occur at close to ambient temperature, a landmark example being the photo-Ullmann reaction (Ziegler et al, 2013; Yoo et al, 2015), and to generate unconventional electronic transitions, leading to completely new reactivity such as for instance [2 + 2] cycloadditions which are impossible via thermal activation (Sarkar et al, 2020)
We report on the development of a new photocatalytic system, displaying high efficiency under redlight, which is based on the immobilization of methylene blue (MB) on silica (SiO2)

Summary

Introduction

Visible-light photochemistry is a promising approach in the development of greener synthetic chemistry. The performances of the homogeneous and heterogeneous PCs (using micro- and nanoparticles) are compared in a batch and in a continuous flow photo-reactor under red light, using the benchmark photo-oxidation of β-citronellol (1), a key step in the industrial synthesis of the commercial fragrance rose oxide (Ravelli et al, 2011).

Results

Conclusion