No abstract

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 o C), H 2 /TG ratio (4-50 mol/mol) and residence time (0.2-2.0 s) 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 o C and a residence time of 2.0 s, 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.

No abstract

A fast and reliable method was developed for the analysis of positional and geometrical triacylglycerol isomers in partially hydrogenated vegetable oils. A binary gradient of heptane/acetonitrile was employed in silver ion HPLC with evaporative light scattering detection. Good resolution of native and partially hardened oils was achieved within 22 min for palm oil and within 60 min for rapeseed oil. Initial stability problems were found to be caused by decreasing acetonitrile concentration in the solvent mixture, due to selective evaporation of acetonitrile. By tightening the bottle caps and plugging the usual ventilation inlets, this could be prevented; the system then became very stable. A complementary system (heptane/acetone) was used to confirm the absence of 1,2‐Elaidin‐3‐palmitin in the hydrogenated samples. This system shows better resolution in the more saturated region (up to three double bonds). However, for less saturated species, peak‐split problems occurred (e.g. for triolein), and the elution strength of acetone was not sufficient for the elution of the most polyunsaturated triacylglycerols of rapeseed oil. This would have required a ternary gradient with an additional, stronger solvent, e.g. acetonitrile. Hence, the original heptane/acetonitrile system was retained as the method of choice. It is sufficiently fast and accurate over a wide range of unsaturation to make it suitable for hydrogenation process control, especially of continuous processes with rapidly changing product composition.