Product recovery process in the filtration of polyether polyols

Abstract

An improved method for recovering a purified polyether polyol comprising the steps of providing an aqueous solution of a polyether polyol containing an alkali metal catalyst residual formed from a transesterification process, contacting the aqueous solution with a stoichiometric excess of magnesium sulfate to form a second aqueous solution, removing water from said second aqueous solution 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, passing the dehydrated slurry of through a filtration system comprising a filtration press to separate the molten polyether polyol phase from the precipitated solid phase, wherein the filtration press is treated with a filter aid that is essentially free of transition metal oxide content, separating the molten polyether polyol phase substantially free of water, residual alkali metal catalyst and transition metal contaminants from the precipitated solid phase and recovering polyether polyol from the separated polyether polyol phase.