Nano-scale DMC catalyst particles
Nano-scale DMC catalyst complexes are highly active alkylene oxide polymerization catalysts. Thy show a greatly improved ability to catalyze the formation of EO-capping onto secondary hydroxyl-terminated polyethers. The catalysts can be prepared by precipitation in the dispersed adequous phase of a water-in-oil emulsion.
1. A process for making a metal cyanide catalyst comprising
(A) forming an emulsion having a plurality of water droplets dispersed in an immiscible continuous phase, wherein the water droplets contain a transition metal cyanide compound and a metal salt that reacts with the transition metal cyanide compound to form a water-insoluble metal cyanide catalyst, and
(B) subjecting the emulsion to conditions such that the transition metal cyanide compound and the metal salt react in the water droplets to form the water-soluble metal cyanide catalyst; wherein the catalyst is in the form of particles having an average particle size, as determined by transmission electron spectroscopy, of from about 5 to about 500 nanometers.
2. The process of claim 1 , wherein step (A) is conducted by
A1) forming a first emulsion of first water droplets dispersed in an immiscible continuous phase, wherein the first water droplets contain a transition metal cyanide compound;
A2) forming a second emulsion of second water droplets dispersed in an immiscible continuous phase, where the second water droplets contain a dissolved metal salt that reacts with the transition metal cyanide compound to form a water-insoluble metal cyanide catalyst; and
A3) mixing the first and second emulsions under conditions such that said first water droplets contact said second water droplets.
3. The process of claim 1 , wherein the immiscible continuous phase includes a surfactant.
4. The process of claim 1 , wherein the immiscible continuous phase includes a liquid organic compound that is immiscible with water.
5. The process of claim 4 , wherein the immiscible continuous phase includes a hydrocarbon, a C 6 or higher alkanol, or a mixture of at least one hydrocarbon and at least one C 6 or higher alkanol.
6. The process of claim 1 , wherein the catalyst is treated with a ligand.
7. The process of claim 6 , wherein the ligand is present during step b).
8. The process of claim 1 , wherein the metal cyanide compound is a hexacyanocobaltate compound and the metal salt is a zinc salt.