Pd/oxide/cordierite monolithic catalysts(oxide = Al_2O_3, SiO_2 and SiO_2Al_2O_3) 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 Al_2O_3 layers had the larger pore size than those with SiO_2 and SiO_2Al_2O_3 layers. Catalytic hydrogenation of 2-ethylanthraquinone(eA Q), a key step of the H_2O_2 production by the anthraquinone process, over the various monolithic catalysts(60 °C, atmosphere pressure) showed that the monolithic catalyst with the moderate thickness of Al_2O_3 layer(about 6 μm) exhibited the highest conversion of e AQ(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. The results of ICP, XRD, SEM-EDX, XPS and N2-adsorption-desorption measurements revealed the the Pd penetration depth increased with increasing the thickness of oxide layer, and the catalysts with Al 2 O 3 layers had the larger pore size than those with SiO 2 and SiO 2 Al 2 O 3 layers. Catalytic hydrogenation of 2-ethylanthraquinone (eA Q), a key step of the H 2 O 2 production by the anthraquinone process, over the various monolithic catalysts (60 ° C, atmosphere pressure) showed that the monolithic catalyst with the moderate thickness of Al 2 O 3 layer (about 6 μm) exhibited the highest conversion of e AQ (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.