Hydrogenation - Introduction

In edible oils and fats industry, hydrogenation is used to produce a more oxidative stable product and change liquid oil into a semi solid or solid fat with the desired melting characteristics. Hydrogenation is a chemical reaction in which hydrogen is reacts with the double bonds found in triglycerides to form saturated bond. It usually performed batch wise in a pressurized stirred reactor with nickel as catalyst. In most cases, the oil is not fully hydrogenated as fully hydrogenated oil is too hard for some applications. Hence, partially hydrogenation is applied and this gives high trans fatty acid in the hydrogenated oil. It has been proven that trans fatty acid have negative effect on human health. As a result, future approach of hydrogenation is in the reduction of trans-formation.

First of all, feed oil is pumped into a buffer tank. This buffer tank is a multi function tank where it provide heating, degassing, drying and as a buffer tank. The feed oil is preheated by the out going hydrogenated oil followed by steam to 160 ^oC. After the measuring tank reached the pre-set amount and temperature, the oil will be drained to the hydrogenation reactor. At the same time, nickel catalyst in oil slurries is pumped into the reactor.

After the filling process completed, vacuum is applied to the reactor before the pressurized hydrogen is pumped in. This is to remove moisture and oxygen in the air which may cause hazard when mixed with hydrogen. The hydrogenation reaction proceeds as follow:

R₁CH=CHR₂ + H₂ à R₁CH₂-CH2R₂                                          

IV for the hydrogenated oil is checked from time to time. When the required IV is obtained, the hydrogenated oil is pumped to a drop tank.

This drop tank act as a buffer tank to hold the hydrogenated oil before it is used for heat recovery with the feed. After heat exchange, the hydrogenated oil is sent to another buffer tank to cool down to temperature below 100 ^oC prior sent to filtration process. This is to protect the cloth in the pulse tube filter. The filtered oil is sent to final polishing filter before pumped to storage tank. The schematic representation of hydrogenation process is shown below: