Highly dispersed Pd catalyst for anthraquinone hydrogenation supported on alumina derived from a pseudoboehmite precursor

Pseudoboehmite was synthesized using the separate nucleation and aging steps (SNAS) method for the first time. An alumina support (Al2O3(PB)) was then prepared by extrusion method using the synthesized pseudoboehmite as precursor. Compared with spherical alumina (Al2O3(OD)) prepared by the conventional oil-drop method, Al2O3(PB) exhibits higher surface area, more regular pore structure and narrower pore size distribution. Al2O3(PB) and Al2O3(OD) were used as supports to prepare Pd catalysts. The catalytic performance of the two Pd catalysts was investigated in the catalytic hydrogenation of 2-ethylanthraquinone (EAQ) to 2-ethylanthrahydroquinone, a key step in the anthraquinone process for the manufacture of hydrogen peroxide. Compared with Pd/Al2O3(OD) catalyst, Pd/Al2O3(PB) catalyst showed higher Pd dispersion and thinner Pd penetration depth which resulted in more catalytically active site and easier diffusion of the reactants, and consequently Pd/Al2O3(PB) catalyst exhibited higher anthraquinone hydrogenation activity and better selectivity.