Molecular Assembly Line: Stepwise Hydrogenation of Multifunctional Substrates over Catalyst Mixtures

Abstract

The synthesis of many chemical products requires multiple steps. To simplify the overall synthesis by combining consecutive reaction steps, the concept of a “molecular assembly line” promises to yield high reaction rates and selectivities. In this study, mixtures of carbon nanotube (CNT)‐supported catalysts were used to demonstrate the potential of this concept on hand of the hydrogenation of nitrobenzene via aniline to cyclohexylamine. Mixtures of Pt/CNT, having a high activity in nitrobenzene hydrogenation, and of Ru/CNT, highly selective for the hydrogenation of aniline to cyclohexylamine, provided high activity at constant high selectivity. Varying the Pt:Ru ratio to 5:95 was found to be the best case scenario, for which the rates of the two consecutive reaction steps are balanced. The use of catalyst mixtures rather than bimetallic catalysts avoids complex phenomena such as phase separation or migration of one of the metals to the surface of the bimetallic particles.

Dual metal nanoparticles within multicompartmentalized mesoporous organosilicas for efficient sequential hydrogenation

“…Here, Ru and Pd were selected to demonstrate the construction of a cascade catalyst (Ru/Pd/MCMOS) since Ru NPs are proven to be catalytically active towards hydrogenation of arenes 36 – 39 while Pd NPs are ideal catalysts towards hydrogenation of nitro group 40 – 42 . Integration of these two metal NPs in a single particle is necessary to realize efficient one-pot sequential hydrogenation of nitrobenzene to cyclohexylamine 43 .…”

“…3a ). Dual metal-involved catalysts are necessary to achieve high catalytic efficiency 43 , because they can respectively catalyze one step of the sequential hydrogenation aforementioned.…”

Ultrafine Platinum Nanoparticles Derived from Supramolecular Crystal for Catalytic Hydrogenation of Nitroarenes

“…由于 苯胺类化合物的巨大作用, 开发廉价、高效的苯胺制备 方法依然是有机合成和化工工业中一个重要的研究方 向 [1][2][3][4][5][6][7][8] . 硝基苯直接催化加氢制备苯胺无疑是一种最为 直接、原子经济及环境友好的合成方法 [9][10][11][12][13][14][15][16][17] . 在催化加 氢反应中, 催化剂的催化活性对反应速率和产物质量具 有重要的影响.…”

Ru/g-C3N4 as an efficient catalyst for selective hydrogenation of aromatic diamines to alicyclic diamines

“…Transition metals, such as active components of catalysts, including Ni, 8 Co, 9 Ru, 10 Rh, 11,12 Pd 13 and Pt, 14,15 are oen applied to the hydrogenation of aromatic amines, [16][17][18][19] and it can catalyse the hydrogenation of aromatic-ring group of PPDA with PPDA conversion of 100% and CHDA selectivity of 71.6%, respectively. 3 However, undesired side reactions such as deaminization or condensation usually occur severely during the hydrogenation by using the aforementioned catalysts, which decrease the selectivity of CHDA through formation of deamination by-products or secondary amines.…”