Supported silver and copper catalysts for selective oxidation of benzyl alcohols using molecular oxygen as oxidant

Abstract

ABSTRACT This dissertation presents sustainable and efficient processes for the oxidation of benzyl alcohols using molecular oxygen as the oxidant and catalyzed by Ag-Cu bimetallic catalysts supported on polyoxometalates (POM) and on talc. The catalysts were prepared by galvanic displacement and reduction using polyvinyl pyrrolidone and polyethylene glycol. Catalyst characterization was performed using a combination of Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), powder X-ray diffraction analysis (PXRD), X-ray fluorescence analysis (XRF), BET surface analysis, transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), energy dispersive spectroscopy (EDS) and thermogravimetric analysis (TGA). The oxidation reaction was carried out using a Schlenk– line setup under ambient pressure. Reaction products were identified by gas chromatography-mass spectrometry (GC-MS) and quantified by gas chromatography (GC) using internal standard method. The Ag-Cu/POM catalyst afforded 100% benzyl alcohol conversion in 5 h with >99% selectivity to benzaldehyde. When tested on various benzyl alcohol derivatives the Ag-Cu catalysts gave good conversions and nearly 100% selectivity to the corresponding aldehydes. The Ag-Cu bimetallic catalysts supported on the POM are highly stable and don’t show tendency to leach or deactivate. The catalysts are heterogeneous in nature and easy to recover after reactions and could be reused at least 5 times without significant loss in activity and selectivity. The developed protocols have potential for industrial application.