Hydrogenation of palm oil in near-critical and supercritical propane

Palm oil was hydrogenated in a single-phase mixture with propane and hydrogen. This was done in a small (0.5 ml), continuous fixed-bed reactor, using a 1% Pd/C catalyst. Temperature (65-135 degreesC), H-2/TG ratio (4-50 mol/mol) and residence time (0.2-2.0s) were varied systematically to assess the iodine value (IV) as a function of these three variables. The substrate concentration was 1 wt-%. The IV was dependent mainly on temperature and residence time. At 120 degreesC and a residence time of 2.0s, full hydrogenation was achieved. The trends observed indicate that this is possible even at lower temperatures, if the residence time is increased further. Unexpectedly, the hydrogen concentration (i.e. the H-2/TG ratio) was of minor importance, which can be a sign of either H-2-saturation of the catalyst or a phase-split of the reaction mixture with resulting mass transport limitations for the hydrogen. Unfortunately, the catalyst showed strong signs of deactivation very early in the experiments, possibly due to impurities in the feedstock and/or to coke formation.