What is hydrogenation of fats and oils?

Under the action of a metal catalyst, hydrogen is added to the double bonds of the unsaturated fatty acids of triglycerides, and this chemical reaction is called the hydrogenation of fats and oils, or hydrogenation of fats and oils for short. After the hydrogenation reaction of fats and oils, the iodine value decreases, the melting point rises, and the number of solid fats increases, which is called hydrogenated oil or hardened oil.

Based on the different degree of hydrogenation reaction, there are light hydrogenation (selective hydrogenation) and deep (extreme) hydrogenation. Selective hydrogenation refers to the strict control of the sequence and speed of hydrogenation of highly unsaturated glycerol, respectively, to obtain different characteristics of the product; deep hydrogenation, on the other hand, refers to almost all of the unsaturated double bond hydrogenation reaction to produce highly saturated oil and grease products.

The main factors affecting the hydrogenation reaction:

(1) temperature

General high temperature, molecular kinetic energy, mass transfer rate, reaction speed are faster; but the temperature is too high, the solubility of hydrogen in the oil is small, the amount of hydrogen adsorbed on the catalyst is reduced, the reaction is blocked. Commonly used temperature is 100 ~ 180 ℃, fatty acid deep hydrogenation temperature up to 200 ~ 220 ℃. Selective hydrogenation is often controlled temperature of 130 ~ 150 ℃.

(2) Pressure

The higher the pressure, the higher the concentration, the greater the concentration of hydrogen adsorbed on the catalyst. Selective hydrogenation pressure is generally 0.02 to 0.5 MPa. For the production of very low iodine value fatty acids and industrial oils, the working pressure can be as high as 1.0 to 2.5 MPa in order to shorten the reaction time.

(3) stirring speed

Hydrogenation reaction, the catalyst is suspended, gas, liquid, solid three-phase must be an effective exchange of material, energy, requiring the reaction process needs strong stirring. Too high a stirring speed will increase the number of isomeric acids and power consumption, and an appropriate stirring speed should be selected.

(4) reaction time

Reaction time depends on the temperature, catalyst addition and activity, working pressure and other factors, one or more of which rises, the reaction rate will be accelerated, and the time required to get the same iodine value product is also accelerated. Selective hydrogenation reaction time is often 2 to 4 hours.

(5) raw material treatment is to remove all kinds of impurities that can lead to the reduction of catalyst activity and poisoning in the raw material oil before hydrogenation.

(6) Different products require the selection of catalysts with different characteristics.