Isoprene/methyl acrylate Diels-Alder reaction in supercritical carbon dioxide

The Diels-Alder reaction between isoprene and methyl acrylate was carried o ut in supercritical carbon dioxide in the temperature range 110-1.40 degree s C and the pressure range 95.2-176.9 atm in a 300 cm(3) autoclave. The hig h-pressure phase behavior of the reaction mixture in the vicinity of its cr itical region was determined in a mixed vessel with a sight window to ensur e that all the experiments were performed in the supercritical single-phase region. Kinetic data were obtained at different temperatures, pressures, a nd reaction times. It was observed that in the vicinity of the critical poi nt the reaction rate constant decreases with increasing pressure. It was al so determined that the reaction selectivity does not change with operating conditions. Transition-state theory was used to explain the effect of press ure on reaction rate and product selectivity. Additional experiments were c onducted at constant temperature but different phase behaviors (two-phase r egion, liquid phase, supercritical phase) by adjusting the initial composit ion and pressure. It was shown that the highest reaction rate is in the sup ercritical region.