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| The reusability of supported Ni0-nanoparticles was tested undersimilar reaction condition. The catalyst was separated by filtration,washed, dried and reused for Hantzsch condensation for a fresh reac-tion mixture up to run no. 4. The results in Fig. 5 showed that there is a decrease in product yield in subsequent reuse i.e. 95% in run no. 1 de-creased to 81% in run no. 4. The stability of the used catalyst recovered after run no. 1 was investigated by HRTEM [Fig. 4] and there is no signif-icant change in size or shape of the Ni0-nanoparticles. The nanoparticles were well dispersed on the support and sized in the range of 3–10 nm. The effect of nickel loading of 1.0, 3.0 and 4.85 wt.% of the catalyst, on the condensation reaction of benzaldehyde, dimedone, ethylacetoace-tate, and ammonium acetate was investigated and the corresponding yields of 41.3%, 69% and 95% were found. This clearly indicates that4.85 wt.% of Ni nanoparticles showed the best efficacy. A comparison of the efficiency of catalytic activity of the modified Montmorillonite supported Ni0-nanoparticles with several previous methods is presented in Table 3. The results show that the present method is better compared to some of the earlier reports in terms of yield and reaction time. |
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笔墨轻点: 金币+25, 翻译EPI+1 2014-09-25 20:17:20
笔墨轻点: 金币+25, 翻译EPI+1 2014-09-25 20:17:20
| 被支撑的Ni0纳米粒的重复利用性在相似的条件下进行了测试。过虑分离后的催化剂，经清洗、干燥重新用于新反应混合物的Hantzsch缩合反应，这样的过程可以重复4次。图5表明，之后（催化剂）重新利用时，生成物的产量会降低，例如从第一次的95%下降到第4次的81%。HRTEM研究了第一次催化后重新恢复利用的（催化剂）的稳定性（图4），Ni0纳米粒的尺寸和形状都没有很大的变化，充分地分布于支撑物中，尺寸从3nm到10nm不等。研究了含1%、3%，4.85% 镍的催化剂催化苯甲醛、双甲酮、乙酰乙酸乙酯、乙酸铵缩合反应时的效果，它们的生成物产量分别是41.3%, 69% 和 95%。这清楚说明，含4.85% 镍的纳米粒催化效率最高。表3对比了改性Montmorillonite支撑的Ni0纳米粒与之前几种方法的催化效率。结果显示，对比于早期的研究成果，本文提出的方法在生成物产量和反应时间方面更优越。 |
2楼2014-09-25 18:57:18
