One-pot synthesis of Pd nanoparticles on ordered mesoporous Al2O3 for catalytic hydrogenation of 2-ethyl-anthraquinone

Abstract

Pd/Al2O3 catalysts were synthesized via one-pot evaporation-induced self-assembly and hydrothermal methodology, and the conventional impregnation method. XRD, N2 adsorption-desorption and TEM showed that the one-pot synthesized catalyst, especially evaporation-induced self-assembly one (EISA-Pd/Al2O3) possesses the large specific surface area, ordered mesopores with the narrow pore size distribution and well-dispersed Pd particles encapsulated inside the mesopores of Al2O3. Catalytic hydrogenation of 2-ethyl-anthraquinone (EAQ) to form anthrahydroquinone at 0.3MPa and 70°C showed that EISA-Pd/Al2O3 exhibits superior performance, with the improvement of 50% in the selectivity and 82% in the activity compared with the impregnated catalyst. The high selectivity is due to the increased electron density of Pd particles and lower amount of acid sites measured by NH3-TPD, which had an inhibitory effect on the formation of the by-product and degradation products. The high activity could be ascribed to the higher proportion of linear carbonyls which has a positive correlation with low-coordinated Pd atoms, characterized by in situ FTIR. DFT calculations revealed that the high activity of the defective Pd surface with low-coordinated Pd atoms is due to the larger adsorption energy and longer length of carbonyl bond of EAQ adsorbed on it than on the perfect Pd surface.