A Pd-Cu Nanosized Catalyst Supported on γ-Al2O3 for Liquid-Phase Nitrobenzene Hydrogenation

Abstract

Copper nanocatalysts doped with palladium deposited on γ-Al₂O₃ were prepared and used for the hydrogenation of nitrobenzene. The catalysts were obtained by the formation of intermediate metal-complex compounds on the surface of the γ-Al₂O₃ carrier with their subsequent hydrogenolysis and reduction of the active phases of the catalyst, calcination, and additional treatment with hydrogen. The structure of the catalysts was investigated using the following. low-temperature nitrogen sorption, SEM with EDX, TEM, X-ray fluorescence analysis, XRD, and DRIFTS. DRIFT studies indicate the presence of active phases of catalysts in the form of reduced and divalent palladium and copper. According to DRIFTS-CO data, copper is present in the Cu²⁺ state in the calcined catalysts Cu/γ-Al₂O₃_1 and Cu-Pd/γ-Al₂O₃_1, but it is reduced to Cu⁺ when the reducing agent, CO, is adsorbed. Palladium in the calcined sample of Cu-Pd/γ-Al₂O₃_1 is present in two states - Pd²⁺ and Pd⁰ (due to the method of preparation of this sample). In the Cu-Pd/γ-Al₂O₃_2 catalyst, the state of palladium is Pd⁺. It was found that the metal content on the surface of the particles increases after reduction in hydrogen. The catalyst based on Cu/γ-Al₂O₃ had low activity, the addition of palladium led to an increase in the activity. Thus, in the presence of the PdCu/γ-Al₂O₃ catalyst, a 85% nitrobenzene conversion was achieved with a 100% aniline selectivity.

Graphical Abstract