AlCl3 modified Pd/Al2O3 catalyst for enhanced anthraquinone hydrogenation

Anthraquinone hydrogenation to produce H2O2 is an economically interesting reaction with great industrial importance. Here, we report a series of Pd/xAl catalysts with different AlCl3 contents by a conventional stepwise impregnation method. The optimal Pd/1.0Al catalyst exhibits a higher performance toward anthraquinone hydrogenation with 8.3 g·L−1 hydrogenation efficiency, 99.5% selectivity and good stability, obviously superior to that of Pd/Al2O3 catalyst (5.2 g·L−1 and 97.2%). Detailed characterization demonstrates that AlCl3 can be grafted on the γ-Al2O3 support to obtain a modified support with abundant surface weak acid and Lewis acid, which can adsorb and activate anthraquinone. Meanwhile, its steric hindrance could isolate and disperse active metals to form more active sites. The synergies between metal sites and acid sites promotes the anthraquinone hydrogenation. Furthermore, the good stability after grafting AlCl3 could attribute to the enhanced metal-support interaction inhibiting metal particles agglomeration and leaching.