Promotion Effect of Zn on Amorphous Co-B alloy and Their Catalytic Performance for Selective Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol

Amorphous Co-B and Co-Zn-B alloy catalysts were prepared by the method of chemical reduction with KBH4 in aqueous solution. Zn promotion effect to Co-B catalyst and the performance of the Co-Zn-B catalysts were investigated by the selectivity hydrogenation of cinnamaldehyde (CMA) to cinnamyl alcohol(CMO). It was indicated from XRD and DSC that the presence of Zn could hardly change the amorphous structure of Co-B catalyst, and the peak of crystalization heat of 1% Co-Zn-B catalyst was 15 K higher than Co-B catalyst which revealed that sui-table Zn-content was favorable to increase the thermal stability of Co-B catalyst. On the profile of H2-TPD, a new H2-desorption peak was observed at 655 K which showed that a new H2-absorption site was formed. The results of XPS showed that the Zn composition elements of Co-Zn-B amorphous catalyst were all existed at both states of reduction and oxidation. This chemical shift of binding energy caused a deficient potential formed that was equilib-rium on the whole, but the electron distributing was unbalanced on part. The effect of the coupled absorption of this dificent site to the side-bond of C=O group and the polarization effect of the oxide metal of Co-Zn-B catalyst to carbonyl increased the selective hydrogenation of C=O group of the catalyst. The reaction conditions and stability were also investigated. The optimum reaction conditions was determined as T (temperature)=413 K, PH2(H2 pressure)=2.5 MPa, and t(reaction time)=3.0 h, and the highest yield of CMO reached 84.0%. The stability of the catalyst is excellent.