Hybrid sol–gel double metal cyanide catalysts for the copolymerisation of styrene oxide and CO2.

Hybrid sol–gel catalysts of zinc hexacyanocobaltate and SiO₂ were prepared by co-precipitation of the double metal cyanide with silica. Hybrid catalysts prepared at moderately acidic conditions showed the best performance with respect to activity, selectivity and stability. The hybrid sol–gel materials displayed high catalytic activity for the copolymerisation of styrene oxide and carbon dioxide (up to 650 mol_SO (mol_Zn h)⁻¹) and high productivity (575 g_Polymer g_Catalyst⁻¹). They also displayed good selectivity to the polymeric product (80–87%), while only little cyclic styrene carbonate was formed as side product. A detailed electron microscopy study of the hybrid sol–gel materials showed that the active phase consisted of thin platelets containing the metals in a molar ratio n_Zn/n_Co = 2.1, whereby the double metal cyanide was closely associated with silica. [ABSTRACT FROM AUTHOR]