超声处理对非晶态Co-B催化性能的促进作用

以超细Co-B非晶态合金催化肉桂醛（CMA）液相选择性加氢制备肉桂醇（CMO）为目标反应，考察超声波预处理对其催化性能的影响并根据催化剂系统表征，如XRD，TEM，SEM，XPS，DSC，BET等，对超声波预处理的影响机理进行了初步讨论。研究发现，控制以应时间为1.5h，则不管是新鲜的Co-B还是经过不同时间超声波预处理后的Co-B非晶态合金，其对肉桂醇的选择性均可达到100％，但超声波预处理对催化活性有显著影响。以28kHz的超声波处理Co-B非晶态合金时，随着超声时间的增加，CMA加氢反应中的吸氢速率、CMA的转化率和CMO的得率均显著增加，主要归因于超声波的分散作用导致催化剂比表面积增加；但超声时间过长（＜20min），却又可导致对催化活性的抑制作用，归因于超声波空化产生的局部高温以及微射流的冲击使催化剂颗粒团聚，导致比表面积下降。

Promoting Effects of Presonication on the Performance of the Co-B Amorphous Catalyst during Selective Hydrogenation of Cinnamaldehyde

The effect of the presonication on the catalytic performance of the ultrafine Co-B amorphous alloy was investigated in liquid phase selective hydrogenation of cinnamaldehyde(CMA) to cinnamyl alcohol (CMO) which showed perfect selectivity to CMO(100%) regardless of the ultrasonic treatment. No significant change in the selectivity at the catalyst, while remarkable change in the activity was observed. When the Co-B amorphous alloy was treated with 28 kHz ultrasounds, both the hydrogen uptake rate and the conversion of CMA as well as the yield of CMO increased with the increase of presonication time, showing the promoting effect of the ultrasonic treatment on the catalytic performance of the Co-B amorphous alloy. While, overtreatment for presonication resulted in the decrease in the activity of the Co-B amorphous catalyst. Various characterizations, such as XRD, DSC, TEM, XPS etc. , demonstrated that the presonication had no significant effect on the nature of the active sites, which could account for the facts that both the activity per m2 of the BET surface area and the selectivity to CMO remained almost unchanged during the presonication. The increase in the activity of the Co-B amorphous catalyst was mainly attributed to the increase of its BET surface area owing to the dispersing effect of ultrasounds. Very long presonication was harmful for the activity since the BET surface area decreased due to the sintering of the Co-B alloy particles caused by the local high temperature and the collision resulted from the "bubble effect" and the "microwave jet" of the ultrasounds.