Study of the catalytic properties of MgNi(Cu)Al LDH in the one-pot cascade oxidation-Knoevenagel condensation reaction

Abstract

In this work, the structural and bifunctional catalytic properties of MgNi(Cu)Al layered double hydroxides (LDH) with different molar ratios between the cations were studied. The LDH materials were prepared by co-precipitation and were characterized using X-ray fluorescence (XRF), X-Ray diffraction (XRD), diffuse reflectance infrared Fourier-transform spectroscopy (DRIFT), diffuse reflectance ultraviolet-visible spectroscopy (DR-UV-VIS), scanning electron microscopy (SEM), nitrogen adsorption-desorption and acidity-basicity measurements. They were tested in a one-pot cascade oxidation-Knoevenagel condensation reaction used to synthesize 2-Benzoyl-3-phenylprop-2-enenitrile also known as 2-Benzoyl-3-phenylacrylonitrile (BPA). This involved the benzyl alcohol (BnOH) oxidation under an oxygen atmosphere followed by the Knoevenagel condensation of benzaldehyde with 3-oxo-3-phenylpropanenitrile also known as benzoyl acetonitrile (BzACN). Three different non-polar solvents, i.e., toluene, benzene and 1,3,5-trimethylbenzene (mesitylene), were used as reaction media. For the LDH catalysts containing both nickel and copper, the alcohol conversion and BPA yield increased with Ni/Cu molar ratio. The acid-base properties of the solids and the nature of the solvent strongly influence the reaction performance.