Fundamental Insights into Deactivation by Leaching during Rhenium-Catalyzed Deoxydehydration
Fundamental Insights into Deactivation by Leaching during Rhenium-Catalyzed Deoxydehydration
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铼催化脱氧脱水过程中浸出失活的基本见解
DOI：
10.1021/acscatal.9b02806
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发表时间：
2019
期刊：
影响因子：
12.9
通讯作者：
Jentoft, Friederike C.
中科院分区：
文献类型：
--
作者：
Sharkey, Bryan E.;Jentoft, Friederike C.
脱氧脱水是一种选择性地在一个催化步骤中将二醇转化为烯烃的转化，它具有很大的生物质升级潜力，因为它可以去除氧，所得到的双键对进一步的功能化很有用。最近对已知的可溶性氧化铼催化剂的多相化版本的研究已经产生了不同的结果，稳定性是一个反复出现的问题。在本工作中，通过比较一系列由载体区分的材料，系统地研究了催化剂失活的原因。催化剂的制备方法是将过酸铵初始湿浸渍在1、2或4 wt %铼的tio2和zro2上，然后在4 wt %铼的SiO2、Fe2O3和al2o3上，然后煅烧。在温度为150℃，以甲苯为溶剂，以三苯基膦为还原剂的条件下，所有催化剂对1,2-癸二醇转化为1-癸烯均有活性。TiO2和sio2负载型催化剂的铼归一化1-癸烯生成率与均相甲基三氧铈催化剂相当，选择性在80 - 90%之间，而其他催化剂的活性明显较低。高活性与快速失活相关。发现铼浸出是失活的主要原因，是通过催化剂与二醇结合产生可溶性乙醇酸络合物而引起的。均相催化作用显著。除了选择合适的载体（即可还原性或刘易斯酸）外，还可以通过适当的低铼负载（取决于载体），选择对底物不太理想的溶剂，并将反应驱动到100%底物转化，从而导致铼的再沉积，从而最大限度地减少浸出。
Deoxydehydration, a transformation that selectively converts diols into olefins in a single catalytic step, has great potential for biomass upgrading because it removes oxygen, and the obtained double bond is useful for further functionalization. Recent efforts to produce heterogenized versions of known soluble oxido-rhenium catalysts have produced mixed results, with stability being a recurring issue. In the present work, the reasons for catalyst deactivation were systematically investigated by comparisons within a series of materials distinguished by the support. Catalysts were prepared by incipient wetness impregnation of ammonium perrhenate onto TiO2and ZrO2at 1, 2, or 4 wt % rhenium and SiO2, Fe2O3, and Al2O3at 4 wt % rhenium, with subsequent calcination. All catalysts were active in the conversion of 1,2-decanediol to 1-decene at a temperature of 150 °C, in toluene as the solvent at autogenous pressure and with triphenylphosphine as the reductant. The rhenium-normalized 1-decene formation rates for TiO2- and SiO2-supported catalysts were comparable with that of a homogeneous methyltrioxorhenium catalyst with selectivities between 80 and 90%, whereas the other catalysts were significantly less active. High activity was correlated with rapid deactivation. It was found that rhenium leaching is the primary cause of deactivation and is induced via association of the catalyst with the diol to give a soluble glycolate complex. Homogeneous catalysis contributions were significant. In addition to choosing a suitable (i.e., reducible or Lewis acidic) support, leaching can be minimized through an appropriately low rhenium loading that depends on the support, selecting a solvent that is less than ideal for the substrate, and by driving the reaction to 100% substrate conversion, which results in redeposition of rhenium.
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