Method to increase the resistance of double metal cyanide catalysts to deactivation
This invention relates to a semi-batch process for the production of polyoxyalkylene polyether polyols. These polyoxyalkylene polyether polyols have hydroxyl (OH) numbers of from 112 to 400. This process comprises establishing oxyalkylation condition in a reactor in the presence of a DMC catalyst, continuously introducing alkylene oxide and a suitable starter into the reactor, and recovering an oxyalkyated polyether polyol. The oxyalkylation initially occurs at a temperature that is sufficiently high enough to avoid or prevent deactivation of the DMC catalyst, or for from 2% to 50% of the total oxide feed amount, and the oxyalkylation is then continued at a lower temperature.
1. A semi-batch process for the production of a polyoxyalkylene polyether polyol having an OH number of from 112 to 400, comprising:
(1) establishing oxyalkylation conditions in an oxyalkylation reactor in the presence of a double metal cyanide catalyst;
(2) continuously introducing alkylene oxide and a low molecular weight starter into said reactor, said starter consists essentially of ethylene glycol, propylene glycol, glycerine, 1,3-butanediol, 1,4-butanediol, dipropylene glycol, trimethylolpropane, pentaerythritol, sorbitol, ethanol, propanol, butanol, or combinations thereof; and
(3) recovering an oxyalkylated polyether polyol from the reactor;
wherein said oxyalkylation initially occurs at and is maintained at a temperature of from greater than about 1351 to about 1501 for up to a bout 60 minutes and for between 10% and 50% of the total oxide feed amount, and then continuing the oxyalkylation at a temperature in the range of from 120° C. to 130° C.
2. The process of claim 1 , wherein said oxyalkylation at higher temperature occurs for between 10% and 40% of the total oxide feed amount.
3. The process of claim 1 , wherein said polyoxyalkylene polyether polyol has a hydroxyl number in the range of from 125 to 350.
4. The process of claim 1 , wherein said oxyalkylation at the lower temperature continues at least until the CAOS feed is substantially complete.
5. The process of claim 1 , wherein the low molecular weight starter consists essentially of glycerin.
6. The process of claim 1 , wherein the said low molecular weight starter consists essentially of glycerin containing from 500 to 2500 ppm water.
7. The process of claim 1 , wherein the double metal cyanide catalyst concentration in the final product is between 0.002 and 0.02 wt. %, based on the amount of polyoxyalkylene polyether product.
8. The process of claim 1 , wherein said polyoxyalkylene polyether polyol has a hydroxyl number in the range of from 150 to 350.
9. The process of claim 1 , wherein the temperature at which said oxyalkylation initially occurs at and is maintained at is reduced by at least 10° C. during the course of the low molecular weight starter feed.