Highly Dispersed Pd Nanoparticles Supported on Zr-Doped MgAl Mixed Metal Oxides for 2-Ethylanthraquinone Hydrogenation

Abstract

In this study, Pd-Mg(Al)-LDH/γ-Al2O3 and Pd-Mg(Al)Zr-LDH/γ-Al2O3 precursors were synthesized by impregnating Na2PdCl4 on Mg(Al)-LDH/γ-Al2O3 and Mg(Al)Zr-LDH/γ-Al2O3, and then the precursors were calcinated and reduced to obtain Pd-Mg(Al)-MMO/γ-Al2O3 and Pd-Mg(Al)Zr-MMO/γ-Al2O3 catalysts. Compared with Pd/γ-Al2O3 catalyst, the hydrogenation efficiency of Pd-Mg(Al)-MMO/γ-Al2O3 and Pd-Mg(Al)Zr-MMO/γ-Al2O3 increased by 15.7% and 24.0%, respectively. Moreover, the stability of Pd-Mg(Al)Zr-MMO/γ-Al2O3 catalyst was also higher than that of Pd/γ-Al2O3. After four runs, the hydrogenation efficiency of Pd/γ-Al2O3 decreased from 12.1 to 10.0 g/L, while that of Pd-Mg(Al)Zr-MMO/γ-Al2O3 decreased from 15.0 to 14.3 g/L. The active aquinones selectivities of all catalysts were almost 99%. The structures of the catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption–desorption, inductively coupled plasma-atomic emission spectrometry (ICP-AES), CO chemisorption analysis, transmission electron microscopy (TEM), temperature-programmed reduction with hydrogen (H2-TPR), and X-ray photoelectron spectroscopy (XPS). The results indicate that the improved catalytic performance is attributed to the stronger interaction between Pd and Mg(Al)Zr-MMO/γ-Al2O3, smaller Pd particle size and higher Pd dispersion. This work develops an effective method to synthesize highly dispersed Pd nanoparticles based on the layered double hydroxides (LDHs) precursor.