Hydrogenation of citral on Pt and PtSn supported on activated carbon felts (ACF).

In this paper a study about the effect of the Sn addition to Pt supported on activated carbon felts (ACF) on the catalytic behaviour in citral hydrogenation is reported. Catalysts with different Sn contents were prepared by successive impregnation of ACF previously purified by a treatment with HCl, HNO3 and HF and a subsequent thermal treatment with H-2. PtSn/ACF catalysts with tin contents between 1 and 3 wt% were tested in the citral hydrogenation and characterized by using test reactions of the metallic phase (cyclohexane dehydrogenation and cyclopentane hydrogenolysis), H-2 chemisorption and XPS techniques. Results of the citral hydrogenation show that the modification of the Sn content leads to an important change in the selectivity in citral hydrogenation. Thus, the Pt/ACF catalyst has an important selectivity to isopulegol, citronellal and acetals. When Sn is added to Pt/ACF, the nerol and geraniol formation is clearly enhanced. Taking into account both the catalytic results and those of the characterization techniques, a probable structure of the catalytic surface is proposed.