ZnBr2-Ph4PI as highly efficient catalyst for cyclic carbonates synthesis from terminal epoxides and carbon dioxide
ZnBr2-Ph4PI as highly efficient catalyst for cyclic carbonates synthesis from terminal epoxides and carbon dioxide
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ZnBr2-Ph4PI作为末端环氧化物和二氧化碳合成环状碳酸酯的高效催化剂
DOI：
10.1016/j.apcata.2008.02.021
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发表时间：
2008-06
影响因子：
5.5
通讯作者：
中科院分区：
文献类型：
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作者：
考察了溴化锌与不同磷盐组成的催化体系在温和条件下由CO2和末端环氧化物无溶剂合成环状碳酸酯的反应。在所考察的催化剂中，ZnBr_2-Ph_4PI的催化效果最好，而ZnBr_2-氧化膦（Bu_3PO或Ph_3PO）的催化效果不明显。显然，鏻盐的卤离子在反应中起着重要作用。ZnBr_2-Ph_4PI催化剂的催化活性随Ph_4PI与ZnBr_2摩尔比的增大而增大，当Ph_4PI与ZnBr_2摩尔比大于6时，催化活性变化不大。我们观察到，随着ZnBr 2与Ph 4PI摩尔比的增加，环氧化物转化率增加，但TOFPO（基于Zn 2+的位点数估计）下降。首次考察了水对反应的影响。我们发现，即使是微量水的存在也会导致反应性显著下降，这一观察结果为为什么迄今为止研究人员的结果重现性差提供了一个有效的解释。考察了反应温度、CO2压力等因素对ZnBr 2-PPh 4 I催化性能的影响。结果表明，该催化剂对反应温度敏感，反应温度升高至130°C有利于环状碳酸酯的生成。实验结果表明，随着CO2初始压力的升高，催化剂的活性增加，在初始CO2压力为2.5MPa时，催化剂的活性达到最大值。此外，一个合理的反应机制已被提出。
The catalyst systems composed of ZnBr2and different phosphonium salts were examined for solvent-free synthesis of cyclic carbonates from CO2and terminal epoxides under mild conditions. Among the catalysts investigated, ZnBr2–Ph4PI was found to be the best while those of ZnBr2–phosphine oxide (Bu3PO or Ph3PO) show no catalytic effect. It is apparent that the halide ions of phosphonium salts have an essential role to play in the reaction. The catalytic activity of ZnBr2–Ph4PI increases with a rise of Ph4PI to ZnBr2molar ratio up to 6, above which there is little change in catalytic activity. We observed that with a rise in ZnBr2to Ph4PI molar ratio, there is increase in epoxide conversion but decline in TOFPO(estimated based on the site number of Zn2+). The effect of water on the reaction was investigated for the first time. We found that the presence of even a trace amount of water would result in a marked decline in reactivity, and the observation provides a valid explanation for why reproducibility of results is poor among researchers so far. The influences of other parameters such as reaction temperature and CO2pressure on the catalytic performance of ZnBr2–PPh4I were also studied. It is shown that the catalyst is sensitive to reaction temperature, and a rise of reaction temperature up to 130°C favors the formation of cyclic carbonates. We observed that activity increases with rise in CO2pressure and reaches a maximum at an initial CO2pressure of 2.5MPa. Moreover, a plausible reaction mechanism has been proposed.
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影响因子：
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