Regulating effects of anthraquinone substituents and additives in photo-catalytic oxygenation of p-xylene by molecular oxygen under visible light irradiation

Dabo Jiang, Qiao Zhang, Long Yang, Youer Deng, Bo Yang, Yachun Liu, Chao Zhang and Zaihui Fu

Renewable Energy, 2021, vol. 174, issue C, 928-938

Abstract: This paper reports that the optical properties of anthraquinone (AQ) and its photo-catalytic performance in the visible light-driven p-xylene (PX) oxidation can be fine-tuned and improved through varying its skeleton substituents at the molecular level, and the electron-withdrawing substituent exhibits a better improvement effect than the electron-donating one. The best catalyst 2-carboxyanthraquinone (AQ-COOH) can achieve 70.9% PX conversion and 88.2% p-toluic acid selectivity under visible light illumination and 1 atm O2 pressure. The addition of benzenesulfonic acid in the above photocatalytic system can further increase PX conversion to 86.7%, along with a significant improvement in the selectivity of p-carboxybenzaldehyde and terephthalic acid, which likely originates from the unique recombination behavior of the photo-generated charge carriers of the catalyst and the additive driven by the strong interactions between their aromatic skeletons and acidic substituents. Furthermore, AQ-COOH can achieve almost quantitative yield of acetylacetone in ethylbenzene photooxidation and the regulating effect of toluene's para-position substituents on its reactivity is also reported in the AQ-COOH photocatalysis system. Based on quenching tests and EPR spectral characterizations, the oxygen vacancies (h+), superoxide free radicals (O2•-) and singlet oxygen (1O2) as the photo-generated active species are involved in the proposed photo-catalysis mechanism.

Keywords: Anthraquinones; Substituents; Photo-catalytic oxygenation; Benzenesulfonic acid (search for similar items in EconPapers)
Date: 2021
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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:174:y:2021:i:c:p:928-938

DOI: 10.1016/j.renene.2021.04.100

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