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

Pd/Al2O3 catalysts were synthesized via one-pot evaporation-induced self-assembly and hydrothermal methodology, and the conventional impregnation method. XRD, N-2 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 0.3 MPa and 70 degrees 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. (C) 2016 Elsevier B.V. All rights reserved.