PtSn/SiO2 CATALYSTS PREPARED BY SCR IN THE CITRAL HYDROGENATION

VILELLA J., PEREZLINDO M., BORBATH I., MARGITFALVI, J., DE MIGUEL, S., SCELZA, O.

Rio de Janeiro (Brasil)

Congreso; 2do. Congreso de Ingeniería Química del Mercosur-EMPROMER 2005; 2005

The catalytic behaviour of bimetallic PtSn/SiO2 catalysts prepared by surface controlled reaction was studied in citral hydrogenation. Citral molecule has three sites able to be hydrogenated: a carbonyl group, a double C=C bond conjugated with the carbonyl group, an isolated C=C double bond and it also exists as cis and trans isomers. Results of citral hydrogenation show that the different reaction routes strongly depend on the metallic loadings of both Pt and Sn, thus giving either a high selectivity to citronellal (in the case of the monometallic ones) or to unsaturated alcohols nerol+geraniol, for bimetallic catalysts. The citronellal cyclization (giving isopulegol) was found to be practically absent in our case even for monometallic catalysts, this indicating that the acidic sites of the support were not present. Independently on the Sn content, the higher the Pt loading, the higher the selectivity to unsaturated alcohols and the faster the reaction. Undesirable side reactions such as the acetal formation were not present. Test reaction results show modifications of the metallic phase due to the tin addition.