Patent ID: 6864378
Filing Date: 2005-03-08
Classification: C07D

Abstract:
1. An integrated process for continuous production of high purity, polymer grade dianhydro sugar alcohol, comprising the steps of: a) continuously feeding an aqueous solution of a sugar alcohol to a reaction vessel maintained at an elevated reaction temperature and a reduced pressure; b) contacting the sugar alcohol with a dehydration catalyst; c) evaporating most of the water from the aqueous solution; d) continuously dehydrating the sugar alcohol, with the evolution of water vapor, to form a reaction mass comprising dianhydro sugar alcohol, monoanhydro sugar alcohols, dimers and polymers; e) separating from the reaction mass most of the dianhydro sugar alcohol formed, by volatilizing It with the water vapor evolved to form a vapor stream and a byproduct stream; comprising monoanhydro sugar alcohol isomers, dimers, polymers, and the dianhydro sugar alcohols not volatilized from the reaction mass; f) withdrawing the vapor stream comprising dianhydro sugar alcohol and water from the reaction vessel, and partially condensing the stream under controlled temperature and pressure to recover most of the dianhydro sugar alcohol as a slurry of dianhydro sugar alcohol crystals in a mother liquor; g) separating the dianhydro sugar alcohol crystals from the mother liquor; h) withdrawing from the reaction vessel the byproduct stream, comprising monoanhydro sugar alcohol isomers, dimers, polymers, and the dianhydro sugar alcohols not volatilized from the reaction mass in (e); i) diluting the byproduct stream with water and allowing most of the polymers to precipitate; j) separating the precipitated polymers to form a solution of soluble sugar alcohol species; and k) recycling the solution of soluble species to the reaction vessel; while maintaining the flows in and out of steps (a)-(k) at substantially steady rates and substantially steady-state processing conditions.