PHASE-BEHAVIOR OF THE REACTANTS, PRODUCTS AND CATALYSTS INVOLVED IN THE ALLYLIC EPOXIDATION OF TRANS-2-HEXEN-1-OL TO (2R,3R)-(-3-PROPYLOXIRANEMETHANOL IN HIGH-PRESSURE CARBON-DIOXIDE())

The possible phase behavior of a reaction mixture is an important cons ideration when evaluating CO2 as an alternative solvent to replace tra ditional organic compounds. To address this issue we present phase equ ilibrium measurements and modeling of primarily binary mixtures with C O2 of the reactants, products and catalysts present in the allylic epo xidation of trans-2-hexen-1-ol to (2R,3R)-(+)-3-propyloxiranemethanol. This reaction occurs with very high enantiomeric selectivity in liqui d CO2, yields a high value product, and would normally be carried out in an organic solvent like benzene. Thus, it is a promising candidate for CO2 solvent replacement. The systems studied are trans-2-hexen-1-o l-CO2, tert-butyl hydroperoxide (in decane)-CO2, (2R,3R)-(+)-3-propylo xiranemethanol-CO2, tert-butyl alcohol-CO2, diisopropyl L-tartrate-CO2 , vanadium(V)tri-i-propoxy oxide-CO2 and titanium(IV) isopropoxide-CO2 . The compositions of the liquid phases were determined as a function of pressure, at temperatures between 303.15 and 323.15 K and pressures between 31.5 and 110.2 bar. Liquid/liquid immiscibility regions were found for the trans-2-hexen-1-ol-CO2 and (2R,3R)-(+)-3-propyloxiraneme thanol-CO2 binaries. This region is located between 310.9 K (the lower critical end point) and 315.3 K (a type-k point) and the correspondin g pressures of 79.5 and 86.7 bar for trans-2-hexen-1-ol-CO2. The (2R,3 R)-(+)-3-propyloxiranemethanol-CO2 liquid/liquid immiscibility region ranges from 315.1 K (a type-k point) to below 293.7 K, at the correspo nding pressures of 86.1 to 55.8 bar. All of the other binaries exhibit ed simple vapor/liquid equilibrium (VLE). Modeling with the Peng-Robin son equation of state (PREOS) gave reasonably good results for the two phase regions for all of the systems, using just one temperature-inde pendent parameter for each binary system. The PREOS did predict LLV th ree phase regions for the trans-2-hexen-1-ol-CO2 and (2R,3R)-(+)-3-pro pyloxiranemethanol-CO2 binaries, but generally at conditions different from those observed experimentally. Finally, we present some prelimin ary predictions of the multicomponent phase equilibria based on the bi nary measurements and models. (C) 1998 Elsevier Science B.V.