Preparation of ultrafine Pd/γ-Al2O3 catalyst by KBH4 reduction and its application to anthraquinone hydrogenation

The ultrafine Pd/gamma-Al2O3 catalyst was prepared by impregnation of alumina support with PdCl2 solution followed by KBH4 reduction. The microstructure of Pd/gamma-Al2O3 was investigated by X-ray diffraction, high resolution electron microscopy, energy dispersive spectroscopy and electron energy loss spectroscopy. The results show that the Pd species exists as Pd nanocrystals in the as-prepared catalyst, and no Pd-B amorphous alloy was found. Compared with the PdO/gamma-Al2O3 catalyst prepared by impregnation and calcination, the ultrafine Pd/gamma-Al2O3 exhibits higher activity in the hydrogenation of 2-ethylanthraquinone. This can be attributed to the unique properties of the ultrafine Pd/gamma-Al2O3, such as smaller Pd crystals and the higher dispersion of Pd on the support.