Patent ID: 6818781
Filing Date: 2004-11-16
Classification: C07D

Abstract:
A continuous process for the manufacture of dianhydro sugar alcohols comprising:(a) continuously feeding an aqueous solution comprising one or more sugar alcohols or monoanhydro sugar alcohols to a first stage of a multistage reaction vessel; (b) continuously heating the aqueous solution in the first stage in the presence of a dehydration catalyst to form a partially dehydrated reaction mass and water vapor; (c) simultaneously transporting the partially dehydrated reaction mass from the first stage upwards to one or more additional stages of the multistage reactor with water vapor from step (b) while further dehydrating the sugar alcohols to form dianhydro sugar alcohols and simultaneously removing from the reaction mass most of the dianhydro sugar alcohols formed; (d) continuously removing a vapor stream comprising water and dianhydro sugar alcohol product from the reaction vessel and recovering the dianhydrosugar alcohols; and (e) continuously removing high boiling by-products from the reaction vessel as a liquid stream from the final stage of the reaction vessel at a rate coordinated with the feed rate of the aqueous solution so as to maintain a nearly constant quantity of reaction mass in the multistage reaction vessel.