The adsorption of nitrobenzene over an alumina-supported palladium catalyst: an infrared spectroscopic study.

As part of an on-going programme of development of an aniline synthesis catalyst suitable for operation at elevated temperatures, the geometry of the adsorption complex for nitrobenzene on a 5 wt% Pd/AlO catalyst is investigated by infrared (IR) spectroscopy. an appreciation of the reduced site symmetry resulting from adsorption, application of the metal surface selection rule, and observation of in-plane modes only, the adsorption complex (Pd-nitrobenzene) at 28 °C is assigned as occurring vertically or tilted with respect to the metal surface, adopting () symmetry. Moreover, adsorption occurs a single Pd-O bond.

Mechanistic Insight Into the Application of Alumina-Supported Pd Catalysts for the Hydrogenation of Nitrobenzene to Aniline.

Two Pd/γ-AlO catalysts are examined for the vapor phase hydrogenation of nitrobenzene over the temperature range of 60-200 °C. A 1 wt % catalyst is selected as a reference material that is diluted with γ-alumina to produce a 0.3 wt % sample, which is representative of a metal loading linked to a candidate industrial specification aniline synthesis catalyst.

Toward High Selectivity Aniline Synthesis Catalysis at Elevated Temperatures.

In connection with an initiative to enhance heat recovery from the large-scale operation of a heterogeneously catalyzed nitrobenzene hydrogenation process to produce aniline, it is necessary to operate the process at elevated temperatures (>100 °C), a condition that can compromise aniline selectivity. Alumina-supported palladium catalysts are selected as candidate materials that can provide sustained aniline yields at elevated temperatures. Two Pd/AlO catalysts are examined that possess comparable mean Pd particle sizes (∼5 nm) for different Pd loading: 5 wt % Pd/AlO and 0.