Effect of the acid–base properties of the support on the performance of Pt catalysts in the partial hydrogenation of citral

• Acid or basic nature of catalyst induces selectivity in citral hydrogenation.
• Acidity tendency was: Pt/SiO2–ZrO2 > Pt/SiO2–TiO2 > Pt/SiO2 > Pt/MgAl-c.
• Nerol–geraniol products were promoted in acid materials Pt/SiO2–(TiO2 and ZrO2)
• In basic catalyst Pt/(MgAl-c and MgAl-r) citronellal was the main product.
• High catalytic activity was verified over small Pt particles (2 nm) in Pt/MgAl-c.

In this work, the effect that mesoporous solid materials, with different acid–base properties (Pt-1 wt%/acid or base) have over the product distribution during the partial hydrogenation of citral was evaluated. It was found that basic materials were the most active catalysts reaching a 100% citral conversion after 1 h of reaction. Regarding selectivity, in basic materials (Pt/MgAl-c and Pt/MgAl-r) citronellal was the main product, while nerol and geraniol were produced in acid solids (Pt/SiO2; Pt/SiO2–TiO2 and Pt/SiO2–ZrO2). The formation of unsaturated alcohols is related to the strength and density of the acid sites of the catalyst and in this sense the Pt/SiO2–ZrO2 gave a yield of 80%. The acidity trend is: Pt/SiO2–ZrO2 > Pt/SiO2–TiO2 > Pt/SiO2 > Pt/MgAl-c.

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