Chemoselective Pt-catalysts supported on carbon-TiO2 composites for the direct hydrogenation of citral to unsaturated alcohols

- Carbon xerogels-TiO2 composites were developed and used as Pt-supports.
- H2 pretreatment and carbon phase induce the formation of oxygen vacancies on TiO2.
- The combination of oxygen vacancies-Pt is the active and selective sites for citral hydrogenation.
- Citral is adsorbed and hydrogenated by CO bonds using composites as Pt-support.
- Selective catalysts for citral hydrogenation to unsaturated alcohols are obtained.

A series of carbon xerogels-TiO2 composites with different TiO2 contents were prepared, exhaustively characterized and used as a Pt-support to develop selective hydrogenation catalysts. The carbon phase in the composite hinders the TiO2 crystal growth and the transformation to rutile during thermal treatments. Textural, chemical and catalytic properties are determined by the TiO2 content, with an optimum around 40 wt.% of TiO2 content. The mesoporosity of the supports, the Pt-dispersion and Pt-support interactions are favoured in this sense. During the H2-pretreatment, the Pt and TiO2 phases were simultaneously reduced and the formation of oxygen vacancies leads to the mobility of Pt-species inside the TiO2 structure, avoiding sintering in surface and strongly improving both catalytic activity and selectivity. The catalytic performance was discussed on the basis of the sample characteristics. Unsaturated alcohols were obtained as main reaction products in all cases, being the only product in the case of the optimized catalyst.

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