Controllable Synthesis, Structure, and Catalytic Activity of Highly Dispersed Pd Catalyst Supported on Whisker-Modified Spherical Alumina

A new route was introduced to synthesize novel mesoporous spherical alumina supports by in situ growth of alumina whiskers on the surface, and in the pores, of conventional spherical alumina using urea as an OH- donor and a surfactant as a structure-directing agent. BET results indicate that the modified spherical alumina exhibited much higher surface area and more regular mesoporous structure than the unmodified alumina. The whisker-modified spherical aluminas with a flowerlike arrangement of whiskers and higher surface area were then used as support to prepare highly dispersed Pd catalysts. Catalytic performances of the catalysts were studied in the catalytic hydrogenation/oxidation of 2-ethylanthraquinone (EAQ). Compared with a conventional Pd/alumina catalyst, novel Pd/whisker-modified alumina catalysts exhibited much higher Pd dispersion which resulted in more catalytically active sites and therefore significantly higher hydrogenation efficiency. Moreover, shorter diffusion distance reduced the deep hydrogenation of EAQ and consequently achieved higher selectivity and structural stability.