Continuous process for the manufacture of anhydro sugar alcohols and reactor useful therefor

A process for the preparation of a dianhydro sugar alcohol comprising the steps of:

• a) introducing to the first stage of a multistage reactor a process stream comprising at least one sugar alcohol or monoanhydro sugar alcohol and, optionally, water;
• b) intimately contacting said process stream with a counter current flow of an inert gas at elevated temperature to remove the bulk of any water present to yield a dewatered process stream;
• c) intimately contacting said dewatered process stream with a dehydration catalyst in the presence of a counter current flow of an inert gas at elevated temperatures to remove water of reaction as formed;
• and
• d) removing the reaction product from the bottom of the reactor.