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DOUBLE METAL CYANAIDE (DMC) CATALYSTS WITH LEWIS BASE LIGANDS SYNTHESIZED USING A LIGAND EXCHANGE METHOD

IP.com Disclosure Number: IPCOM000032929D
Publication Date: 2004-Nov-18
Document File: 2 page(s) / 29K

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Abstract

Amine-based double metal cyanide (DMC) catalysts composition comprising a layered crystalline DMC catalysts containing amine ligands, e.g. DMC/pyridine catalysts or other DMC/amine catalysts are disclosed. A process for producing such catalysts comprises a gas phase ligand exchange process in which a DMC/glyme catalyst is converted to a DMC/pyridine catalyst or DMC/amine catalyst by heating a powder of the DMC/glyme catalyst with pyridine or amine followed by purging with helium.

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DOUBLE METAL CYANAIDE (DMC) CATALYSTS WITH LEWIS BASE LIGANDS SYNTHESIZED USING A LIGAND EXCHANGE METHOD

R.J. Gulotty and M.H. McAdon

Dow Global Technologies Inc.

DMC catalysts for the polyaddition of alkylene oxides to starter compounds containing active hydroxyl groups are well known.  See for example U.S. Patents 3,404,109; 3,829,505; 5,158,922; 5,482,908 and 5,639,705.  In comparison with conventional preparation of polyether polyols by means of alkali catalysts, such as alkali hydroxides, the use of DMC catalysts is associated with an increased retention of endgroup functionality, i.e., a reduction in the proportion of monofunctional polyethers, so-called monols.  

The DMC catalysts are usually prepared by reacting an aqueous solution of a metal salt with an aqueous solution of a metal cyanide salt in the presence of an organic complexing agent (ligand).  The complexing agent can be added to one or both of the starting solutions or can be added immediately after mixing the two salt solutions.

To improve the high temperature stability of DMC catalysts, it has now been found that DMC catalysts containing a Lewis base ligand, particularly an aromatic amine, can be prepared by a gas phase ligand exchange process.  This method is particularly applicable to DMC catalysts comprising a layered crystalline structure.  Thus by way of example, DMC/glyme or DMC/t-butanol catalyst is converted to a DMC/aromatic amine catalyst by heating a powder of the DMC/glyme or DMC/t-butanol catalyst with the ligand for exchange at a temperature sufficient to displace the initial ligand, generally at a temperature of 150 to 400°C, preferably from 150 to 250°C, and then purging with an inert gas, such as helium.

This exchange method is particularly applicable to aromatic amine ligands which lack a N-H bond, such as pyridine, isoquinoline, nitriles (acetonitrile, benzonitrile or 4‑pyridinecarbonitrile) and Lewis base ligands that lack acidic protons, such as phosphines; ethers such as tet...