Palladium Nanoparticles Incorporated Fumed Silica as an Efficient Catalyst for Nitroarenes Reduction via Thermal and Microwave Heating

Abstract

The reduction of nitroarenes to arylamines is a synthetically important transformation both in the laboratory and in industry. Herein, Palladium (Pd) nanoparticles were synthesized via incorporation with mesoporous fumed silica material by doping technique. Water was used as a solvent and the as-synthetized material was reduced by using NaBH4 to ensure the total transformation of PdO into Pd nanoparticles. The synthesized sample was characterized by using inductively coupled plasma (ICP) elemental analysis, X-ray powder diffraction (XRD), N2 sorption measurement, scanning electron microscope (SEM), energy-dispersive spectroscopy (EDX), and transmission electron microscopy (TEM). Data showed that the Pd nanoparticles were successfully synthesized and supported on the mesoporous silica with an average size in the ranges of 10–20 nm, with an irregular shape. The purity of the synthesized sample was confirmed by EDX analysis which exhibits the presence of Si, O, and Pd. The catalytic activity of the prepared sample was evaluated in the heterogeneous reduction of nitroarenes to aromatic amines. Reduction reaction was monitored by Shimadzu GC-17A gas chromatography (GC, Japan) equipped with flam ionization detector and RTX-5 column, 30 m × 0.25 mm, 1-μm film thickness. Helium was used as carrier gas at flow rate 0.6 mL/min. Interestingly, the green hydrogenation of nitroarenes to primary amine compounds was achieved in an aqueous solution with high efficiency and in a short time; moreover, the reusability of heterogeneous Pd-SiO2 was performed for four repeated cycles with more than 88% of efficiency at the fourth run. Finally, the heterogeneity of catalysis with high reliability and eco-friendly processes is a super new trend of nitroarenes reduction in the industry and economic scales.