Fabrication of supported Pd–Ir/Al2O3 bimetallic catalysts for 2‐ethylanthraquinone hydrogenation

A series of χ wt % Pd‐(1‐χ) wt % Ir (χ = 0.75, 0.50, and 0.25) catalysts supported on γ‐Al₂O₃ have been prepared by co‐impregnation and calcination‐reduction, and subsequently employed in the hydrogenation of 2‐ethylanthraquinone—a key step in the manufacture of hydrogen peroxide. Detailed studies showed that the size and structure of the bimetallic Pd–Ir particles vary as a function of Pd/Ir ratio. By virtue of its small metal particle size and the strong interaction between Pd and Ir, the 0.75 wt % Pd–0.25 wt % Ir/Al₂O₃ catalyst afforded the highest yield of H₂O₂, some 25.4% higher than that obtained with the monometallic 1 wt % Pd catalyst. Moreover, the concentration of the undesired byproduct 2‐ethyl‐5,6,7,8‐tetrahydroanthraquinone (H₄eAQ) formed using the Pd–Ir bimetallic catalysts was much lower than that observed with the pure Pd catalyst, which can be assigned to the geometric and electronic effects caused by the introduction of Ir. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3955–3965, 2017