Stability and recycling of polymer-supported Mo(VI) alkene epoxidation catalysts
Stability and recycling of polymer-supported Mo(VI) alkene epoxidation catalysts
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DOI：
10.1016/j.reactfunctpolym.2007.07.024
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发表时间：
2007-12-01
影响因子：
5.1
通讯作者：
Sherrington, David C.
中科院分区：
文献类型：
--
作者：
Mbeleck, Rene;Ambroziak, Krzysztof;Sherrington, David C.
作为反应精馏塔（RDC）使用t-丁基过氧化氢和异相聚合物负载Mo（VI）催化剂连续环氧化环己烯的前驱，对三种候选聚合物负载Mo催化剂的长期稳定性进行了评估。聚合物催化剂是聚苯并咪唑负载的PBI。Mo和两种聚（苯乙烯-二乙烯基苯）树脂为基础的物种，Ps.AMP。Mo1和mo2是用2-氨基甲基吡啶将含乙烯基氯苄树脂胺化制备的，然后装载Mo。通过在小批量反应中循环10次样品来评估每种聚合物催化剂的稳定性，这些条件将构成连续过程的基础。同时，通过从反应上清溶液中分离任何残留物，在去除非均相聚合物催化剂后，然后将残留物用作环氧化反应的潜在催化剂，研究了每种载体的Mo损失。这是一种强大的技术，用于从载体中明确识别催化活性Mo的损失，并且不依赖于Mo分析程序。所有三种聚合物催化剂在10个连续反应中都具有高活性和选择性，但上清溶液也含有催化活性Mo残基。以PBI为例。Mo和Ps.AMP。经过10个循环老化后，从载体上损失的均相Mo对催化的贡献几乎全部消除，但在Ps.AMP的情况下。即使经过类似的老化，浸出的Mo物种的贡献仍然显著。决定这种差异行为的主要因素似乎是聚合物结合配体与钼的摩尔比，它必须显著高于单位，以提供钼的长期保留。(c) 2007 Elsevier Ltd.。版权所有。
As a prelude to commissioning a reactive distillation column (RDC) for the continuous epoxidation of cyclohexene using t-buty1hydroperoxide and a heterogeneous polymer-supported Mo(VI) catalyst, the long-term stability of three candidate polymer-supported Mo catalysts has been evaluated. The polymer catalysts are a polybenzimidazole-supported species, PBI.Mo, and two poly(styrene-divinylbenzene) resin-based species, Ps.AMP.Mo1 and 2, prepared in-house by amination of vinyl benzyl chloride-containing resins using 2-aminomethyl pyridine, followed by loading with Mo. The stability of each polymer catalyst was assessed by recycling a sample 10 times in small batch reactions using conditions that will form the basis of the continuous process. At the same time the loss of Mo from each support has been investigated by isolating any residue from reaction supernatant solutions, following removal of the heterogeneous polymer catalyst, and then using the residues as potential catalysts in epoxidation reactions. This is a powerful technique for identifying unambiguously loss of catalytically active Mo from the support and is not dependent on Mo analytical procedures. All three polymer catalysts are highly active and selective in 10 consecutive reactions but the supernatant solutions also contain catalytically active Mo residues. In the case of PBI.Mo and Ps.AMP.Mo2 the contribution to catalysis from homogeneous Mo species lost from the supports is all but eliminated after aging through 10 cycles, but in the case of Ps.AMP.Mo1 the contribution from leached Mo species remains significant even after similar aging. The major factor determining this differential behaviour seems to be the mole ratio of polymer-bound ligand to Mo which must be significantly above unity to provide long-term retention of Mo. (c) 2007 Elsevier Ltd. All rights reserved.