Liquid phase selective hydrogenation of cinnamaldehyde (CAL) was investigated over ZnO-supported Pd and PdZn catalysts different in the Pd loading. The former monometallic catalyst was less selective to the formation of cinnamyl alcohol (COL) irrespective of the Pd loading (5 and 30 wt.-% Pd). When the Pd loading was small (5 wt.-%), PdZn catalyst (PdZn-5) indicated similar catalytic actions. However, PdZn catalyst containing Pd in a larger content of 30 wt.-% (PdZn-30) showed different results: the COL selectivity was about 20% at low conversion but it increased with CAL conversion, reaching to >50% at a conversion of 60%. The COL selectivity was likely to change depending on the concentration of a product of hydrocinnamaldehyde (HCAL). The coadsorption of HCAL should control the orientation of CAL molecules adsorbed on the PdZn-30 catalyst. This may assist the adsorption of CAL via its aldehyde group on the surface of catalyst, resulting in an increase in the COL selectivity. Unique catalysis of PdZn-30 may result from structural features of the surface of its large PdZn particles, which are different from those of PdZn-5 having smaller PdZn particles.

在负载不同的ZnO负载的Pd和PdZn催化剂上研究了肉桂醛（CAL）的液相选择性加氢。前者的单金属催化剂对肉桂醇（COL）的选择性较低，而与Pd的负载量（5和30 wt .-％Pd）无关。当Pd负载量小（5重量％）时，PdZn催化剂（PdZn-5）显示出相似的催化作用。但是，含Pd含量大于30 wt .-％（PdZn-30）的PdZn催化剂显示出不同的结果：低转化率下的COL选择性约为20％，但随着CAL转化率增加，在转化率下达到> 50％ 60％。根据氢化肉桂醛（HCAL）产物的浓度，COL选择性可能会发生变化。HCAL的共吸附应控制吸附在PdZn-30催化剂上的CAL分子的方向。这可以帮助CAL通过其醛基吸附在催化剂表面上，从而提高COL选择性。PdZn-30的独特催化作用可能来自其大PdZn颗粒表面的结构特征，这与具有较小PdZn颗粒的PdZn-5的结构特征不同。