Effects of porous oxide layer on performance of Pd-based monolithic catalysts for 2-ethylanthraquinone hydrogenation

Pd/oxide/cordieritemonolithic catalysts (oxide = Al2O3, SiO2 and SiO2-Al2O3) were prepared by the impregnation method. The results of ICP, XRD, SEM-EDX, XPS and N-2 adsorption-desorption measurements revealed that the Pd penetration depth increased with increasing the thickness of oxide layer, and the catalysts with Al2O3 layers had the larger pore size than those with SiO2 and SiO2-Al2O3 layers. Catalytic hydrogenation of 2-ethylanthraquinone (eAQ), a key step of the H2O2 production by the anthraquinone process, over the various monolithic catalysts (60 degrees C, atmosphere pressure) showed that themonolithic catalystwith the moderate thickness of Al2O3 layer (about 6 mu m) exhibited the highest conversion of eAQ (99.1%) and hydrogenation efficiency (10.0 g.L-1). This could be ascribed to the suitable Pd penetration depth and the larger pore size, which provides a balance between the distribution of Pd and accessibility of active sites by the reactants. (C) 2016 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.