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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向桂醇(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,控制反应时间为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128kHz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。
The effect of ultrasonic pretreatment on the catalytic performance was investigated by selective liquid-phase selective cinnamic aldehyde (CMA) hydrogenation of ultrafine Co-B amorphous alloy to cinnamyl aldehyde (CMO). According to the catalyst system characterization, XRD, TEM, SEM, XPS, DSC, BET and so on, and discussed the influence mechanism of ultrasonic pretreatment. The results showed that when the reaction time was controlled to 1.5h, the selectivity to cinnamyl alcohol could reach 100%, no matter the fresh Co-B or the Co-B amorphous alloy after ultrasonic pretreatment at different time. However, ultrasonic Pretreatment has a significant effect on the catalytic activity. With the increase of ultrasonic time, the hydrogen absorption rate, the conversion rate of CMA and the yield of CMO in the CMA hydrogenation reaction are all significantly increased when the Co-B amorphous alloy is treated with ultrasonic wave at 128 kHz, which is mainly due to the increase of ultrasonic Dispersion results in an increase in the specific surface area of the catalyst; however, ultrasonication for a long time (> 20 min) can lead to an inhibitory effect on the catalytic activity due to the local high temperature generated by ultrasonic cavitation and agglomeration of the catalyst particles due to the impact of the microjets, Specific surface area decreased.