锌对非晶态Co-B合金的改性及催化肉桂醛加氢为肉桂醇的研究

采用KBH4还原法制备了非晶态Co-B和Co-Zn-B催化剂,以肉桂醛选择加氢制肉桂醇为探针反应,研究了Zn对Co-B非晶态催化剂的修饰改性作用,并采用XRD、DSC、XPS、和H2-TPD对催化剂进行了表征.研究表明,少量的Zn没有改变Co-B催化剂的非晶结构,但提高了催化剂主体的热稳定性,其中1%的Zn可使Co-B非晶态催化剂主体结晶放热峰提高12K,并在665K出现新的H2脱附峰,说明催化剂因掺入锌形成了新的氢吸附中心,锌在催化剂中以金属态和氧化态两种形式存在.催化剂的整体均衡而局部电子分布不均衡的缺陷势结构增强了对肉桂醛分子C=O双键O原子的侧链偶合吸附与金属氧化物的金属离子对羰基的极化作用协同活化了肉桂醛的C=O双键,提高了催化剂对C=O双键的加氢选择性.加氢反应工艺条件及催化剂寿命研究表明,适宜的反应温度为413K,氢压为2.5MPa,反应时间为3.0h,肉桂醇的最高产率可达84.0%,并具有较好的催化稳定性.

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.