Preparation of Pd–B/TiO2 amorphous alloy catalysts and their performance on liquid-phase hydrogenation of p-nitrophenol

The Pd–B/TiO2 amorphous alloy catalyst were prepared by the liquid-phase chemical reduction with KBH4 aqueous solution. The catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC) and high reaction transmission electron microscopy (HRTEM). Analysis results show that the active metal clusters Pd–B are homogeneously dispersed on the surface of the TiO2 particles and the size of most metal clusters is below 10 nm. The as-prepared Pd–B/TiO2 catalysts exhibit higher catalytic properties (activity, selectivity, and stability) than the corresponding Pd-based catalysts and Ni-based catalysts during the liquid-phase p-nitrophenol (PNP) hydrogenation to p-aminophenol (PAP), which indicates the promoting effect of the alloying B and TiO2 support. Enriched electron state of Pd active sites and high dispersion of the Pd–B active sites on TiO2 support are mainly attributed to the improvement of catalytic activity of Pd–B/TiO2 amorphous alloy catalyst. The effects of different reaction parameters such as support, pH value, Pd loading and the thermal treatment on the catalytic activity of the Pd–B/TiO2 amorphous alloy catalyst were studied in detail. The maximum preparation condition is achieved by using TiO2 (P25), pH 12 and 0.5% amount of Pd loading.