Confined Ruthenium Nanoclusters in Montmorillonite for Ethylene Hydroformylation to 3-Pentanone

The selective synthesis of 3-pentanone (DEK) from ethylene hydroformylation is an atom-economical route with simplified operation. However, this process is still hampered by the competing formation of aldehydes and a lack of high-performance heterogeneous catalysts. Herein, we report ruthenium nanoclusters (∼1 nm) confined within montmorillonite (Ru/MMT) as a catalyst for the direct hydroformylation of ethylene to 3-pentanone with high selectivity. Under optimized conditions (150 °C, 4 MPa), the Ru/MMT catalyst achieves a 3-pentanone selectivity of 87.3% among oxygenates and a high space−time yield of 64.9 molDEK·molRu−1·h−1, outperforming most previously reported heterogeneous systems. The interlayer structure and abundant surface hydroxyls (Si−OH) of MMT effectively anchor and stabilize Ru nanoclusters, while the confined mesopores and acid sites promote the adsorption and activation of ethylene and CO. Through a combination of in situ DRIFTS and probe experiments, the reaction network is elucidated via a surface propionyl (C2H5CO*;) intermediate, which couples with a co-adsorbed ethyl (C2H5*;) species to form 3-pentanone, bypassing propanal formation.