Hydrogenation of 2-ethylanthraquinone on Pd-La/SiO2/cordierite and Pd-Zn/SiO2/cordierite bimetallic monolithic catalysts

A series of Pd-La/SiO2/cordierite (cordierite = COR) and Pd-Zn/SiO2/COR bimetallic monolithic catalysts were prepared, characterized, and tested for the hydrogenation of 2-ethylanthraquinone (eAQ) as the key step of anthraquinone method for production of H2O2. It was found that the metal particle size is remarkably dependent on the Pd/M (M = La, and Zn) mass ratio of bimetallic monolithic catalysts. By virtue of its small metal particle size and the strong interaction, the 0.8% Pd-0.4% La/SiO2/COR monolithic catalyst presents the highest H2O2 yield (7.7 g L-1) and selectivity toward active quinones (95%), which is attributed to the addition of La leading to the synergistic effect between Pd and La. Moreover, the density functional theory (DFT) calculations for the adsorption of eAQ over the surface of Pd-La/SiO2/COR and Pd-Zn/SiO2/COR bimetallic monolithic catalysts have been conducted to further understand the mechanism of molecule surface interactions between eAQ and the PdM(1 1 1) or Pd(1 1 1) surfaces. Detailed studies showed that the high catalytic activity of Pd-La/SiO2/COR bimetallic monolithic catalyst is attributed to the stronger adsorption between Pd3La1 (1 1 1) and the carbonyl group of eAQ.