Cobalt Carbonyls Stabilized by N,P-Ligands: Synthesis, Structure, and Catalytic Property for Ethylene Oxide Hydroalkoxycarbonylation

Chemical kinetics and promoted Co-immobilization for efficient catalytic carbonylation of ethylene oxide into methyl 3-hydroxypropionate

The carbonylative transformation of ethylene oxide (EO) into methyl 3-hydroxypropionate (3-HPM) is a key process for the production of 1,3-propanediol (1,3-PDO), which is currently viewed as one of the most promising monomers and intermediates in polyester and pharmaceuticals industry. In this work, a homogeneous reaction system using commercial Co₂(CO)₈ was first studied for the carbonylation of EO to 3-HPM. The catalytic behavior was related to the electronic environment of N on aromatic rings of ligands, where N with rich electron density induced a stronger coordination with Co center and higher EO transformation. A reaction order of 2.1 with respect to EO and 0.3 with respect to CO was unraveled based on the kinetics study. The 3-HPM yield reached 91.2% at only 40°C by Co₂(CO)₈ coordinated with 3-hydroxypyridine. However, Co-containing colloid was formed during the reaction, causing the tough separation and impossible recycling of samples. Concerning the sustainable utilization, Co particles immobilized on pre-treated carbon nanotubes (Co/CNT-C) were designed via an in situ reduced colloid method. It is remarkable that unlike conventional Co/CNT, Co/CNT-C was highly selective toward the transformation of EO to 3-HPM with a specific rate of 52.2 mmol·gCo-1·h-1, displaying a similar atomic efficiency to that of coordinated Co₂(CO)₈. After reaction, the supported Co/CNT-C catalyst could be easily separated from the liquid reaction mixture, leading to a convenient cyclic utilization.