Synthesis and catalytic testing of Lewis acidic nano zeolite Beta for epoxide ring opening with alcohols
Synthesis and catalytic testing of Lewis acidic nano zeolite Beta for epoxide ring opening with alcohols
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DOI：
10.1016/j.apcata.2019.03.009
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发表时间：
2019-05
期刊：
影响因子：
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通讯作者：
Aamena Parulkar;Alexander P. Spanos;N. Deshpande;N. Brunelli
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文献类型：
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作者：
Aamena Parulkar;Alexander P. Spanos;N. Deshpande;N. Brunelli
刘易斯酸性沸石是稳健的催化材料，其能够进行一系列用于精细化学品生产的重要化学反应，包括用醇开环环氧化物。晶体结构对大分子施加了扩散限制，通过减小粒度以产生用刘易斯酸性锡（nSnBeta）取代的纳米沸石β来克服所述扩散限制。使用标准方法表征nSnBeta，以证明锡有效地结合到沸石骨架中，具有类似于微米级常规Sn-β（cSnBeta）的开放和封闭位点。虽然nSnBeta对于涉及小底物如表氯醇和甲醇的反应表现出与cSnBeta相当的催化活性，但当使用大底物如1，2-环氧辛烷和乙醇时，观察到nSnBeta相对于cSnBeta的催化性能的改善。nSnBeta和cSnBeta将太大而不能进入孔的环状环氧化物转化到相似的程度，表明改进的性能与外表面上催化位点数量的增加无关。催化剂再利用实验表明，材料上的有机物积累降低了催化活性，通过煅烧可以部分恢复。总的来说，结果表明纳米沸石β可以以小的粒度合成（即，150 nm），以帮助克服用于环氧化物的醇开环的大体积基底的扩散限制。
Lewis acidic zeolites are robust catalytic materials that are capable of a range of important chemistry for fine chemical production, including the epoxide ring opening with alcohols. The crystalline structure imposes diffusion limitations for large molecules that are overcome through reducing the particle size to produce nano zeolite beta substituted with Lewis acidic tin (nSnBeta). nSnBeta is characterized using standard methods to demonstrate that tin is efficiently incorporated into the zeolite framework with open and closed sites similar to the micron-sized conventional Sn-Beta (cSnBeta). While nSnBeta exhibits comparable catalytic activity to cSnBeta for reactions involving small substrates such as epichlorohydrin and methanol, an improvement in catalytic performance is observed for nSnBeta relative to cSnBeta when using large substrates such as 1,2-epoxyoctane and ethanol. nSnBeta and cSnBeta convert a cyclic epoxide too large to enter the pores to similar extents, indicating that the improved performance is not associated with an increased number of catalytic sites on the external surface. Catalyst reuse experiments demonstrate that organic accumulation on the material reduces catalytic activity that can be partially restored through calcination. Overall, the results demonstrate that nano zeolite beta can be synthesized with small particle sizes (i.e., 150 nm) to help overcome diffusion limitations for bulky substrates for the alcohol ring opening of epoxides.