Selective hydrogenation of citral by noble metals supported on carbon xerogels: Catalytic performance and stability

A series of monometallic Pt, Ir and Ru-catalysts deposited on carbon xerogel microspheres was prepared, exhaustively characterized and used in the selective hydrogenation of citral. A similar metal particle size is obtained in all cases after He-pretreatment, allowing the comparison between metals; the catalytic activity increases in the sense Ir < Ru < Pt. Sintering is favoured when catalysts are pretreated in H-2-flow leading to an important loss of activity, especially for Ru-catalysts. Pt and Ir-catalysts are more selective than Ru-catalysts, reaching selectivity values to unsaturated alcohols of around 80%. Thus, in terms of yields to these valuable products Pt-catalysts seem to be the most appropriate active phase. Nevertheless, reutilization experiments showed that Ir-catalyst maintained a good performance while a severe deactivation is observed for Pt-catalysts. This fact is discussed on the basis of the different nature of the deposits formed during reaction. (C) 2015 Elsevier B.V. All rights reserved.