The hydrogenation of soybean oil was studied in a rotating packed disk reactor (RPDR). This new three-phase reactor were equipped with the rotating disks filled with $Ni/SiO_2$ catalysts which were half submerged in the oil phase. As the disks rotate, the hydrogen transfers to the catalyst surface through the oil film and the product in the liquid phase goes through spontaneous mixing.
Soybean oil is composed of triglycerides of fatty acids such as palmitic, stearic, oleic, linoleic and linolenic acids. When the double bonds in the fatty acids react with hydrogen, the liquid state oil can be turned into semi-solid fats and the flavor stability of oil is improved when partially hydrogenated. The current process of oil hydrogenation is carried out in a slurry reactor of a batch mode. Thus the reuse is restricted and furthermore the filtration of the used catalyst is quite cumbersome.
The present study aims at investigating the possibility of oil hydrogenation in a RPDR where no filtration is needed. The temperature, the pressure of hydrogen, the catalyst concentration and the speed of the disks were chosen as experimental variables to study the conversion in terms of iodine value and selectivity ratio based on the production rate of the fatty acid with one double bond to that of the fully saturated fatty acid. The typical experimental condition was set as 180℃, hydrogen pressure of 2 atm, 2.5\% Ni catalyst concentration and 60 rpm of the disk speed. The activity and the selectivity ratio increased with the increase of temperature, catalyst concentration and the rotating speed of disks. When the hydrogen pressure was increased, the activity increased but the selectivity ratio decreased a lot. The effect of the rotating speed was more significant at a lower hydrogen pressure (0.4 atm).
The results of this study showed that oil hydrogenation can be successfully carried out even in a continuous mode in view of the present batch experiment and proved partially that RPDR is qualified as a general three-phase catalytic reactor.
