Harnessing the selective catalytic action of supported gold in hydrogenation applications

Gold has untapped potential in terms of selectivity in the reduction of targeted chemical functions and substituents. In this chapter, the selective action of supported gold in the hydrogenation of R-NO2, R–CH=O and R–C≡CH is examined, with an analysis of the pertinent literature. Hydrogenation activity requires the formation of gold particles at the nanoscale where the support is critical in determining ultimate catalytic performance. The crucial catalyst structural and surface properties required to achieve enhanced hydrogenation are discussed. The chapter examines in turn the chemoselective hydrogenation of chloronitrobenzene, dinitrobenzene, nitrobenzonitrile, nitrocyclohexane, benzaldehyde, nitrobenzaldehyde, phenylacetylene and furfural. Catalytic gold use in hydrogenolysis is also considered, focusing on hydrodechlorination as a progressive approach to the transformation and recycle of toxic chloro-compounds. The catalytic response is related to possible thermodynamic constraints with an examination of process variables, notably temperature, contact time and H2 partial pressure. Process sustainability is evaluated in terms of mode of operation/productivity, solvent usage, the application of bimetallic catalysts, hydrogen utilisation and the viability of dehydrogenation–hydrogenation coupling. The chapter ends with an assessment of the current state-of-the-art and a consideration of possible future research directions