Preparation of Well-Defined Double-Metal Cyanide Catalysts for Propylene Oxide Polymerization and CO₂ Copolymerization

Abstract

Reevaluating the composition of the double metal cyanide catalyst (DMC) as a salt of (NC) 6 Co 3− anions with 1:1 Zn 2+ /(X)Zn + cations (X = Cl, RO, AcO), we prepared a series of well-defined DMCs, [was precisely determined at the atomic level through Rietveld refinement of the synchrotron X-ray powder diffraction data. By evaluating the catalyst's performance in both propylene oxide (PO) polymerization and PO/CO 2 copolymerization, a correlation between structure and performance was established on various aspects including activity, dispersity, unsaturation level, and carbonate fraction in the resulting polyols. Ultimately, our study identified highly efficient catalysts that outperformed the state-of-the-art benchmark DMC not only in PO polymerization [DMC-(OAc/ OtBu/Cl)(0.59/0.38/0.15)] but also in PO/CO 2 copolymerization [DMC-(OAc/OtBu)(0.95/0.08)]. ■ RESULTS AND DISCUSSION Preparation of DMC-Cl Catalysts Using H 3 Co(CN) 6 . DMC catalysts are traditionally prepared by mixing K 3 Co-