Catalytically sustainable, palladium-decorated graphene oxide monoliths for synthesis in flow
Catalytically sustainable, palladium-decorated graphene oxide monoliths for synthesis in flow
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DOI：
10.1016/j.cej.2019.122598
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发表时间：
2020-02
影响因子：
15.1
通讯作者：
S. Ghobadi;Michael B. Burkholder;S. Smith;B. Gupton;C. Castano
中科院分区：
文献类型：
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作者：
S. Ghobadi;Michael B. Burkholder;S. Smith;B. Gupton;C. Castano
连续流动合成是精细化工和医药产品高通量生产的重要途径。所提及的化学反应通常通过固体负载型催化剂经由填充床催化，其特征在于多个问题，例如高压降、通过床的微通道化和金属催化剂浸出到产物流中。这些问题降低了整体工艺效率。具有高孔隙率和机械坚固性的三维（3D）结构（称为整料）提供了用于金属催化剂颗粒的宏观载体的理想性质。在此，钯（Pd）修饰的、共价键合的氧化石墨烯（GO）层的厘米级整体式催化剂已经通过完全水性的一锅体系制备。这些整体式复合结构被设计用于流动中的Suzuki交叉偶联反应。作为高度工程化的材料，通过微波辐射和乙醇蒸气还原处理来调节整料的性质，例如氧含量和Pd催化剂离子物种。优化的整体式催化剂在流动中显示出超过5 h的操作寿命，这比常规的Pd/GO催化剂填充床高300%。作为概念的证明，整体式催化剂被成功地用作在厘米尺度上进行无损X射线CT扫描元素和孔隙率映射的模型结构。
Continuous flow synthesis is an essential route towards high throughput manufacturing of fine chemical and pharmaceutical products. The mentioned chemistries are often catalyzed by solid-supported catalysts via packed beds which are characterized by multiple issues such as high pressure-drops, micro channeling through the bed, and leaching of the metallic catalyst into the product stream. These issues lower the overall process efficiency. Three dimensional (3D) structures, known as monoliths, with high porosity and mechanical robustness, offer the ideal properties to be used macroscopic supports for metallic catalyst particles. This approach has shown to alleviate several known issues with catalyst packed beds effectively.Herein centimeter-scale monolithic catalysts of palladium (Pd)-decorated, covalently-bonded graphene oxide (GO) layers have been prepared via a completely aqueous, one-pot system. These monolithic composite structures were designed for Suzuki cross-coupling reactions in flow. As highly engineered materials, monoliths’ properties such as oxygen content and Pd catalyst ionic species were tuned via microwave irradiation and ethanol vapor reduction treatments. The optimal monolithic catalysts showed over 5 h of operational longevity in flow, which was 300% higher than the conventional Pd on GO catalyst packed beds. As a proof of concept, the monolithic catalyst was successfully used as a model structure for nondestructive X-ray CT-scan elemental and porosity mapping in the centimeter scale.