Selective hydrogenation of cinnamaldehyde over salt-promoted Pd-based catalysts

Abstract EN

The effect of salt additives (AlCl3, SnCl2, FeCl3) on the catalytic behavior of Pd3 % / Al2O3 catalyst in the selective liquid-phase hydrogenation of cinnamaldehyde in I propanol was investigated at 25 ºC and 4 bar H2 for salt concentrations in the range 4.5×10 -5-, 0.5 ×10 -3-M.

The effect of added metal salts on the catalytic behavior of Pd / Al2O3 is rather complex.

In the case of AlCl3, a significant enhancement of the C = O bond hydrogenation could be achieved, accompanied by a strong suppression of the C = C bond hydrogenation.

The selectivity towards cinnamyl alcohol formation could be raised from 26 % to 70 % by introducing small concentrations of AlCl3 (~2.0 × 10-3 M) into the reaction mixture.

Selectivity improvement was also observed upon the addition of SnCl2 (up to 67 %) and FeCl3 (up to 70 %), however, at the expense of activity which is believed to be due to poisoning of the Pd surface by metallic Fe and Sn.

The mechanisms of the additives effects on the catalytic behavior of Pd / Al2O3 are discussed.