BIMETALLIC CATALYSTS SUPPORTED ON DIFFERENT ACTIVATED CARBON MATERIALS FOR CITRAL HYDROGENATION

摘要

The citral hydrogenation over Pt and PtSn catalysts supported on two types of activated carbon materials, powder ? and feltrn(ACF), was studied. Both supports were purified by successive treatments with different inorganic acids, and then they werernsubmitted to a thermal treatment with HrnH2 in order to eliminate sulphur compounds. Then, a fraction of the purified ACF wasrnfunctionalized with HrnH2O2. The catalysts were prepared by successive impregnation: first with Pt, dried and second with Sn.rnThe Pt content was 5wt% for all the catalysts, while the Sn content ranged between 1 and 3 wt%.rn. Results indicate that the addition of Sn to Pt/C catalyst increases the reaction rate of the citral hydrogenation, while the Snrnaddition to Pt/ACF has a lower influence on the activity. Besides, the Sn addition sharply enhances the selectivity tornunsaturated alcohols (nerol and geraniol) for C- and ACF-based catalysts, reaching about 78% and 72% respectively, for thernhighest Sn content (3 wt%). The catalytic performance of these catalysts in the citral hydrogenation was correlated with therncharacteristics of the metallic phase, determined by XPS and test reactions of the metallic phase (cyclohexanerndehydrogenation and cyclopentane hydrogenolysis). In this sense, an important fraction of ionic Sn (detected by XPS)rnassociated with metallic Pt in the different bimetallic catalysts would enhance the polarization of the carbonyl group of therncitral, thus leading to an increase in the selectivity to unsaturated alcohols.