Sulfuric Acid → Isosorbide

Participants

Reaction Conditions

Reaction Steps

A stream of 45% by weight sorbitol (balance water) is introduced via inlet (1) at a rate of 8490 lb/hr. It contains 21 lb-moles of sorbitol and about 259 lb-moles of water. Aqueous sulfuric acid, 10% by weight, is injected via line (20) at a rate of 200 lb/hr in sufficient quantity to maintain sulfuric acid concentration at 0.5-0.6 wt % of the sorbitol feed (water-free basis). Heat input to stage heaters (51), (52), and (53) is adjusted to maintain the temperatures at 125, 135, and 145° C., respectively. Pressure in the head space above the third stage is maintained at about 18 to 20 mm Hg. The dehydration reaction through all the stages forms about 16.8 lb-moles of isosorbide (80% yield). 4.2 lb-moles of starting sorbitol go to byproducts comprising monoanhydro sorbitol derivatives, dimers, oligomeric and polymeric materials, and decomposition products. The total amount of water vapor produced from feed stream evaporation and the dehydration of sorbitol is about 312 lb-moles. Under the reaction conditions, about 80% of the isosorbide formed volatilizes in 98% purity into the water vapor. The bottoms are removed via line (12) at a rate of about 1110 lb/hr. Under these conditions, the hold up time is about 3 hours. The vapor stream, after contacting with about 10% internal reflux, is greater than 99% pure isosorbide (water-free basis) and leaves the reaction vessel via line (2) at 16 mm Hg pressure. It comprises 312 lb-moles/hr or 5616 lb/hr water vapor and 13.44 lb-moles/hr or 1962 lb/hr isosorbide. Upon condensation, it produces the nominal 15 to 16 million lb/year of isosorbide as about 25.9% aqueous solution. This may be concentrated or purified further depending on the intended use of the product.

Provenance & Evidence