Modeling and design of an environmentally benign reaction process

High-pressure carbon dioxide is attractive as an environmentally-benign replacement for organic solvents, such as benzene, in the synthesis of compounds of high chiral purity. Of particular interest here is the allylic epoxidation of trans-2-hexen-1-ol to (2R,3R)-(+)-3-propyloxiranemethanol. In the modeling and design of this reaction system, difficulties were encountered when standard tools were used to model the phase behavior of the compounds present. These difficulties are demonstrated by modeling the high-pressure phase behavior of carbon dioxide with trans-2-hexen-1-ol and with tert-butyl alcohol. Several examples are used to illustrate the problems encountered. The major problems occurred near the three-phase boundary and in the region with retrograde behavior. By using a technique based on interval mathematics, these difficulties were eliminated and correct results obtained. Final results of the phase behavior modeling lead to an improved design that employs a much lower pressure than originally proposed.