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

• Pt, Ru and Ir-catalysts were developed by impregnation of a microporous carbon xerogels.
• Sintering is favoured after H2 pre-treatments regarding He pre-treatments, mainly for Ru-catalysts.
• Ir-catalysts present a low activity but a high selectivity to unsaturated alcohols.
• Pt-catalysts present the best combination of activity and selectivity, but a deeper deactivation by CO -poisoning.

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 H2-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.

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