Effects of Promoters on Properties of Cu-Zn-Al Catalyst for Selective Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol

Cu-Zn-Al catalyst was modified by the additives such as Ni and Mn, and the prepared catalyst was employed in the selective catalytic hydrogenation of cinnamaldehyde. The results showed that the addition of Ni could improve catalytic activity significantly, moreover, the improving effect was highest when Zn was replaced by Ni, simultaneously leading to excessive hydrogenation. The Cu-(5%)Mn-Zn-Al catalyst exhibited a higher selectivity of 93.6% for C = O bond to cinnamyl alcohol and hydrogenation activity of 33.0% conversion at 130°C under 1.0 MPa of H2 pressure with the reaction time of 1 h. TPR and XRD characterization showed that Mn promoter was favorable for the growth of Cu0 fine grains on the surface of catalyst, which not only led to steric effect which improved the selectivity for cinnamyl alcohol, but also reduced the numbers of active centers, consequently decreased the reaction rate.