Ultrasound-assisted pseudohomogeneous tungstate catalyst for selective oxidation of alcohols to aldehydes

Aram Rezaei,Yasaman Mohammadi,Huajun Zheng,Ali Ramazani

doi:10.1038/s41598-022-06874-5

Aram Rezaei, Yasaman Mohammadi + Show 2 more

Open Access

https://doi.org/10.1038/s41598-022-06874-5

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Abstract

The idea of applying ultrasound (US) as a green activation method in chemical transformations, especially in catalytic alcohol oxidations, technically and ecologically appeals to chemists. In the present work, as an attempt to fulfill the idea of designing an eco-friendly system to oxidize alcoholic substrates into corresponding aldehydes, we developed multifunctional tungstate-decorated CQD base catalyst, A-CQDs/W, and examined its sonooxidation performance in presence of H2O2 as a green oxidant in aqua media. By comparing the catalyst performance in oxidize benzyl alcohol as a testing model to benzaldehyde (BeOH) prior and after US irradiation—trace vs 93%- the key role of ultrasonic irradiation in achieving high yield is completely appreciated. Exceptional thermal and compression condition that is created as a result of acoustic waves is in charge of unparalleled yield results in this type of activation method. The immense degree of reagent interaction in this method, ensures the maximum yield in notably low time, which in turn leads to decrease in the number of unreacted reagents and by-products. Meanwhile, the need for using toxic organic solvents and hazardous oxidants, auxiliaries and phase transfer catalyst (PTC) is completely obviated.

Highlights

The idea of applying ultrasound (US) as a green activation method in chemical transformations, especially in catalytic alcohol oxidations, technically and ecologically appeals to chemists
The A-Carbon quantum dots (CQDs)/W was synthesized through one pot hydrothermal process in 200 °C via combining certain amount of citric acid (CA) as carbon source, [APMIm][Cl] and 1,2-Bis(3-aminopropylamino) ethane as ion stabilizer and hydrophilic functional group and, Stearic Acid, as a hydrophobic group
In the second step, during the ion exchange process, via adding a certain amount of Na2WO4 to the water solution containing as prepared A-CQDs, chloride ions were exchanged with (WO4 =) ones to give final, A-CQDs/W catalyst (Fig. 1)

Summary

Introduction

The idea of applying ultrasound (US) as a green activation method in chemical transformations, especially in catalytic alcohol oxidations, technically and ecologically appeals to chemists. In another work Chevallier et al studied the benzyl alcohol transformation into BeOH in presence of a whole range of metal oxide, metal nanoparticles and metal salts as catalyst species in aqua media by using H 2O2 as oxidant[13].

Results

Conclusion