Direct Propylene Epoxidation with Molecular Oxygen over Cobalt-Containing Zeolites
Direct Propylene Epoxidation with Molecular Oxygen over Cobalt-Containing Zeolites
复制标题
含钴沸石上分子氧直接丙烯环氧化
DOI：
10.1021/jacs.2c00792
复制
发表时间：
2022
影响因子：
15
通讯作者：
Li W
中科院分区：
文献类型：
--
作者：
Li W
用分子氧直接环氧化丙烯是一个100%原子经济的理想反应，但由于环氧化物产物的过度氧化和异构化，好氧环氧化是具有挑战性的。在此，我们报道了均匀钴离子的结构限制在faujasite沸石，即Co@Y，在丙烯的好氧环氧化反应中表现出前所未有的催化性能。在773 K条件下，环氧丙烷选择性为57%，丙烯转化率为24.6%，最先进的环氧丙烷生产速率为4.7 mmol/gcat/h。Co@Y的催化性能非常稳定，在超过200小时内没有观察到活性损失。光谱分析揭示了分离钴离子的分子氧活化的细节，然后与丙烯相互作用产生环氧化物，其中涉及Co2+ -Coδ + -Co2 +(2 < δ < 3)氧化还原循环。通过密度泛函理论计算，研究了环氧丙烷和丙烯醛生成副产物的反应途径，并解释了Co@Y独特的催化性能。这项工作提出了一个明确的例子，构建特定的过渡金属离子在沸石基质对选择性催化氧化。
Direct propylene epoxidation with molecular oxygen is a dream reaction with 100% atom economy, but aerobic epoxidation is challenging because of the undesired over-oxidation and isomerization of epoxide products. Herein, we report the construction of uniform cobalt ions confined in faujasite zeolite, namely, Co@Y, which exhibits unprecedented catalytic performance in the aerobic epoxidation of propylene. Propylene conversion of 24.6% is achieved at propylene oxide selectivity of 57% at 773 K, giving a state-of-the-art propylene oxide production rate of 4.7 mmol/gcat/h. The catalytic performance of Co@Y is very stable, and no activity loss can be observed for over 200 h. Spectroscopic analyses reveal the details of molecular oxygen activation on isolated cobalt ions, followed by interaction with propylene to produce epoxide, in which the Co2+–Coδ+–Co2+(2 < δ < 3) redox cycle is involved. The reaction pathway of propylene oxide and byproduct acrolein formation from propylene epoxidation is investigated by density functional theory calculations, and the unique catalytic performance of Co@Y is interpreted. This work presents an explicit example of constructing specific transition-metal ions within the zeolite matrix toward selective catalytic oxidations.