Continuous synthesis of D,L-alpha-tocopherol catalyzed by a sulfonic acid-functionalized ionic liquid was conducted in supercritical carbon dioxide (SC-CO2). The product was continuously separated from the reaction mixture by SC-CO2 extraction during the course of reaction. Decompression of the supercritical fluid mixture downstream gave the product free of ionic liquid. The yield Of D,L-a-tocopherol was improved with non-polar SC-CO2 and polar propylene carbonate as solvents. The selectivity of D,L-alpha-tocopherol to trimethylhydroquinone (TMHQ) between CO2-rich and ionic liquid-rich phase increased with the increase of pressure, and decreased with the increase of temperature at temperatures from 70 to 115 degrees C and pressures from 15 to 25 MPa. Effect of temperature, pressure and flow rate on the continuous synthesis of D,L-alpha-tocopherol was studied. The conversion of isophytol (IP) and the yield of D,L-alpha-tocopherol increased with decreasing pressure. The extraction rate of D,L-alpha-tocopherol increased with increasing pressure and decreased with increasing temperature. D,L-alpha-Tocopherol yield of 90.4% was obtained at 100 degrees C, 20 IVIPa and a CO2 residence time of 12.6 min. (C) 2008 Elsevier B.V. All rights reserved.