Ultrasound and Radiation-Induced Catalytic Oxidation of 1-Phenylethanol to Acetophenone with Iron-Containing Particulate Catalysts.

Mohamed M A Soliman,Armando J L Pombeiro,Maximilian N Kopylovich,Luís M M Correia,Marta S Saraiva,Ana P C Ribeiro,Ana M Botelho Do Rego,Elisabete C B A Alegria,Ana M Ferraria

doi:10.3390/molecules25030740

Abstract

Iron-containing particulate catalysts of 0.1–1 µm size were prepared by wet and ball-milling procedures from common salts and characterized by FTIR, TGA, UV-Vis, PXRD, FEG-SEM, and XPS analyses. It was found that when the wet method was used, semi-spherical magnetic nanoparticles were formed, whereas the mechanochemical method resulted in the formation of nonmagnetic microscale needles and rectangles. Catalytic activity of the prepared materials in the oxidation of 1-phenylethanol to acetophenone was assessed under conventional heating, microwave (MW) irradiation, ultrasound (US), and oscillating magnetic field of high frequency (induction heating). In general, the catalysts obtained by wet methods exhibit lower activities, whereas the materials prepared by ball milling afford better acetophenone yields (up to 83%). A significant increase in yield (up to 4 times) was observed under the induction heating if compared to conventional heating. The study demonstrated that MW, US irradiations, and induction heating may have great potential as alternative ways to activate the catalytic system for alcohol oxidation. The possibility of the synthesized material to be magnetically recoverable has been also verified.

Highlights

Alcohols and related compounds, e.g., diols or benzoins, are among the most abundant and used starting synthetic materials, and their partial oxidation can provide a significant added value to a number of chemical processes, since many aldehydes, ketones, and carboxylic acids are important by themselves and can be used for further processing [1,2,3]
Apart from the recognized catalytic activity in many oxidation processes, magnetic properties of the iron-containing particles can lead to beneficial features, such as the possibility to activate a catalyst with an oscillating magnetic field of high frequency or to recuperate it with a permanent one [9,12]
Moieties for 1 and 2, while peaks at 500–600 cm−1 can be attributed to the stretching vibration of the Fe-O bond [16]

Summary

Introduction

E.g., diols or benzoins, are among the most abundant and used starting synthetic materials, and their partial oxidation can provide a significant added value to a number of chemical processes, since many aldehydes, ketones, and carboxylic acids are important by themselves and can be used for further processing [1,2,3]. Many transition-based catalysts are currently used for the mild partial alcohol oxidation [7], and non-toxic iron is one of the most attractive components owing to several reasons [8,9,10,11]. Apart from the recognized catalytic activity in many oxidation processes, magnetic properties of the iron-containing particles can lead to beneficial features, such as the possibility to activate a catalyst with an oscillating magnetic field of high frequency (so-named induction heating) or to recuperate it with a permanent one [9,12]. It would be attractive to find ways for the straightforward synthesis of particulate iron-containing materials and to study their catalytic behavior under various energy inputs, such as microwave, ultrasound, and oscillating magnetic irradiations

Methods

Results

Conclusion