The hydrogenation of nitrobenzene to form aniline is a large-scale industrial process performed using a variety of heterogeneous catalysts. One variant of the process involves the application of alumina-supported Pd catalysts. Although several 0.3 wt% Pd/Al2O3formulations exhibit high aniline selectivity (> 99.5%), different grades of these catalysts favour different impurities. It is observed that impurities arise from different reaction pathways depending on the provenance of the catalyst.In order to investigate whether the origins of impurity formation are connected to catalyst structure, a series of Pd catalysts active for this reaction have been characterised by a variety of techniques: chemisorption measurements, X-Ray Diffraction, Transmission Electron Microscopy, Temperature-Programmed Desorption and Infrared spectroscopy[1]. Figure 1:   CO chemisorbed on Pd/Alumina catalyst spectra recorded using Infrared spectroscopy. After saturation, CO was desorbed at increasing temperature by increments of 50�C. The low metal loading industrial grade catalysts are challenging to characterise and required a degree of analytical refinement. Temperature-programmed infrared measurements of the probe molecule carbon monoxide revealed morphological and energetic information that could be correlated with catalytic performance, as seen on figure 1. This information constitutes part of a valuable feedback loop that enables specifications for the next generation of ultra-selective nitrobenzene hydrogenation catalysts to be determined.Reference [1] Lear et al., J. Chem. Phys., 123  , 2005, 174706.

Correlations between reaction profiles and catalyst structure for nitrobenzene hydrogenation over alumina-supported Pd catalysts

247th National Meeting (2014)

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