Sunflower oil hydrogenation on Pd in supercritical solvents: Kinetics and selectivities

The partial hydrogenation of sunflower oil on a few supported Pd catalysts in supercritical (SC) dimethyl ether (DME) as reaction solvent was studied to obtain hydrogenates with low trans C 18:1 and stearic contents.The kinetics was determined on eggshell 0.5% Pd/Al2O3 and uniform 2% Pd/C catalysts using a sequential experimental design in a continuous, radial-flow, internal recycle reactor. The operating variables were temperature (456–513 K), pressure (18–23 MPa) and the space-velocity (WHSV = 41–975 h−1). The rotation frequency and the molar feed concentration (oil:H2:DME) were held constant at 157 rad/s and 1:4:95 mol%, respectively. Kinetic scheme was based on that published before. Some reactor runs were simulated using mixed-flow assumption and the kinetics data for both systems with good results. A comparison was established between the eggshell 0.5% Pd/Al2O3 in DME and the data for 2% Pd/C in propane with respect to trans production and stearic formation. trans seems to be lower using 2% Pd/C in propane, while the undesired stearic formation is less on the eggshell 0.5% Pd/Al2O3 catalyst in DME. An overview is presented on the merits of the catalysts available for the SCF process in terms of linoleic selectivity and trans yield on a few vegetable fats.