Tuning of the Activity and Induction Period of the Polymerization of Propylene Oxide Catalyzed by Double Metal Cyanide Complexes Bearing β-Alkoxy Alcohols as Complexing Agents

Abstract

For the development of commercially viable catalyst systems for the polymerization of propylene oxide (PO), a series of double metal cyanide (DMC) complexes have been developed by reacting aqueous zinc(II) chloride with aqueous potassium hexacyanocobaltate(III) in the presence of various complexing agents (CAs) such as 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol, 2-butoxyethanol (BE), 1-methoxypropan-2-ol, 1-ethoxypropan-2-ol, 1-propoxypropan-2-ol, and 1-butoxypropan-2-ol (BP) with different polarities and tert-butyl alcohol ( t BuOH). The catalyst composition was estimated by combining elemental analysis with thermogravimertic analysis. The coordination of the CA can be identified by employing X-ray photoelectron spectroscopy, X-ray diffraction patterns, and infrared spectroscopy of the catalysts. Pursuing a catalyst system showing favorable polymerization behavior for commercial aspects of both catalytic activity and reaction control, the kinetics of PO polymerizations were investigated by using 4 and 8 L reactors equipped with pilot programmable logic controller systems. While a DMC catalyst bearing t BuOH as a CA showed a long induction period, it gave a very high overall rate of polymerization once activated, resulting in severe exothermic reactions that are hard to control. This problem could be successfully overcome by using the DMC catalysts bearing BE or BP as a CA. All polyether polyols were analyzed by measuring their unsaturation level, molecular weight, and distribution. All of the polyols produced featured a low level of unsaturation (0.014−0.024 mequiv g−1), moderate number-average molecular weights (900−3400), and very narrow polydispersities (1.04−1.19).

Selective synthesis of oligo(carbonate-ether) diols from copolymerization of CO2 and propylene oxide under zinc-cobalt double metal cyanide complex

“…The excess ZnCl 2 and the complexing agents are indispensable for high activity, since the crystallinity of DMC is reduced [38]. The formed DMC catalyst is highly active for ring opening homopolymerization of epoxides and copolymerization of epoxides with CO 2 or cyclic anhydrides [29][30][31][39][40][41] 4 ] (M0Ni, Pd, Pt) with two-dimensional structure for compolymerization of CO 2 /PO with a rapid initial reaction, and there was no cyclic propylene carbonate produced [42]. Unfortunately, the DMC catalyst is heterogeneous, the catalytic mechanism is still not clear, although Darensbourg prepared a series of homogeneous DMC catalyst for cyclohexene oxide/CO 2 copolymerization [43,44].…”

“…However, most of the catalyst systems are sensitive to moisture and would be deactivated in the presence of active-hydrogen containing compound. Double metal cyanide complex (DMC) catalyst is a highly active catalyst for homopolymerization of PO, and it is more tolerant for active-hydrogen containing compounds, and oligoether diols with narrow molecular weight distribution can be produced in the presence of hydroxylic agent [29][30][31]. Thus, copolymerization of CO 2 and PO by DMC catalyst with suitable hydroxylic compound may be an effective method to prepare oligocarbonate diols.…”

Zn–Cr double metal cyanide catalysts synthesized by ball milling for the copolymerization of CO2/propylene oxide, phthalic anhydride/propylene oxide, and CO2/propylene oxide/phthalic anhydride

“…When comparing the properties of the obtained polymers it can also be concluded that Zn-Cr DMC played a significant role in the subsequent copolymerizations and terpolymerization. It is worth noting that the Zn-Cr DMC catalysts prepared in this work by employing ball mill is competitive with that synthesized in the traditional way as reported in recent literatures, with regard to catalytic activity, selectivity and product properties in the polymerizations of CO 2 /PO, PA /PO, CO 2 / PO/PA [6,7,9]. Mn and narrower PDI are a good indication of the merit of ball milling for DMC synthesis [11].…”

“…Among all the catalytic systems, double metal cyanide (DMC) catalyst as a typical heterogeneous catalyst showed high activity. A number of copolymers were synthesized successfully employing various DMC catalysts through conventional methods [6][7][8][9]. However, tedious procedures of DMC preparation in conventional solvent-based methods are a waste of time, energy and materials.…”

Effect of polymerization conditions on the polymer properties of CO2-cyclohexene oxide copolymer prepared by double metal cyanide catalyst

“…These polymer properties are very significant to commercialize those copolymers in the adequate application areas. Lee et al has also reported the kinetic behaviors of DMC catalysts with different complexing agents (CA), and concluded that the kinds of CA affected significantly on the induction time and kinetic behaviors [20].…”