Patent ID: 9040754
Filing Date: 2015-05-26
Classification: C07C,C08G

Abstract:
1. A method for recovering a purified polyether polyol comprising the steps of: (a) providing an aqueous solution of a polyether polyol containing an alkali metal catalyst residual formed from a transesterification process utilizing an alkali metal catalyst; (b) contacting the aqueous solution of step (a) with a stoichiometric excess of magnesium sulfate, magnesium sulfite or a combination thereof to form a second aqueous solution, wherein said stoichiometric excess is based on the amount of said alkali metal catalyst residual; (c) removing water from said second aqueous solution of step (b) at a temperature above the melt temperature of said polyether polyol to produce a dehydrated slurry containing a molten polyether polyol phase essentially free of residual alkali metal and a precipitated solid phase comprising sulfate and/or sulfite salts of the alkali metal catalyst, magnesium hydroxide, and excess magnesium sulfate and/or sulfide; (d) passing the dehydrated slurry of step (c) through a filtration system comprising a filter press to separate the molten polyether polyol phase from the precipitated solid phase, wherein the filtration press is treated with a filter aid with a transition metal oxide content of less than 50 ppb; (e) separating the molten polyether polyol phase essentially free of water, residual alkali metal catalyst and transition metal contaminants from the precipitated solid phase; and (f) recovering a polyether polyol from the separated polyether polyol phase, wherein the polyether polyol has a transition metal oxide content of less than 50 ppb; wherein said filter aid is selected from a group consisting of rice hull ash (RHA), acid washed diatomaceous earth (DE) and mixtures thereof.