Computational Exploration of the Mechanism of the Hydrogenation Step of the Anthraquinone Process for Hydrogen Peroxide Production

Hydrogen peroxide is produced commercially by the sequential hydrogenation and oxidation of anthraquinone (AQ) and tetrahydroanthraquinone (THAQ). The hydrogenation of AQ and THAQ on the Pd(111) surface is investigated with periodic density functional theory (DFT) calculations in this work. Dihydrogen is preferentially adsorbed on the top of a Pd atom, and the produced hydrogen atoms are on two neighboring 3-fold hollow fcc positions. The three benzene rings of AQ are located at bridge sites on the Pd(111) surface. The two carbonyl oxygen atoms of AQ and THAQ successively abstract the surface hydrogen atoms to produce anthrahydroquinone (AHQ) and tetrahydroanthrahydroquinone (THAHQ), respectively. The formation of unwanted byproducts, anthrone (AN), tetrahydroanthrone (THAN), oxanthrone (OAN), and tetrahydro-oxanthrone (THOAN), in the hydrogenation step of the AQ process is also studied to consider the suppression of these byproducts.