Hydrogenation of unsaturated fats

Hydrogenation of unsaturated fats and fatty oils is one of the oldest heterogeneous catalytic processes of industrial significance, and is carried out exclusively by gas-liquid-particle operation, the vaporization of the fats being impracticable. Stirred-slurry operation is the normal mode of operation, the suspended catalyst being finely divided by Raney nickel (B2). 

The selectivity in a system of parallel reactions does not depend much on the catalyst size if effective diffusivities of reactants, intermediates, and products are similar. The same applies to consecutive reactions with the product desired being the final product in the series. In contrast with this, for consecutive reactions in which the intermediate is the desired product, the selectivity much depends on the catalyst size. This was proven by Edvinsson and Cybulski (1994, 1995) for. selective hydrogenations and also by Colen et al. (1988) for the hydrogenation of unsaturated fats. Diffusion limitations can also affect catalyst deactivation. Poisoning by deposition of impurities in the feed is usually slower for larger particles. However, if carbonaceous depositions are formed on the catalyst internal surface, ageing might not depend very much on the catalyst size. 

Frankel et al. (40) have used dicobalt octacarbonyl as a catalyst for the hydrogenation of unsaturated fats and found it to be active at lower temperatures than iron carbonyl. 

Dihydrogen has industrial applications, the most important being in the Haber process (see Sections 15.5 and 27.8), the hydrogenation of unsaturated fats (to produce, for example, margarine), and the production of organic compounds such as methanol (equation 10.11). 

The oil hardening process used in margarine manufacturing involves hydrogenation of unsaturated fatly acids at a pressure of 2-10 atmospheres, temperature of 160-220 °C, and the presence of 0.05-0.1% nickel catalysts. Depending on the number of double bonds, different (partially) saturated triglycerides form in this process. Cis-trans isomerization and double bond movement are also possible under these conditions, which may give rise to 5-40% of trans-fatty acids. 

Hydrogenation of unsaturated fats using Raney nickel catalysts... 

The use of NIR reflectance has gained considerable interest for process analysis in the food, pharmaceutical, petrochemical, and other chemical industries. This method requires little or no sample preparation and involves measurement of the reflectance of a liquid or solid sample relative to that of a standard in the same wavelength series. As illustrated in Table 3, process NIR has gained considerable use for moisture determination in coal, cosmetics, and detergent powders, as well as for protein contents of cereal and grain, and hydrogenation of unsaturated fats and oils. 

Degussa A.G., WO 95/22591, Hydrogenation of Unsaturated Fats, Fatty Acids or Fatty Acid Esters, 1995. 

Various aspects of three-phase fluidization have been the subject of numerous investigations due to its high potential for industrial applications in areas such as catalytic processes, hydrocracking and desulphurization of petroleum products, coal liquefaction, hydrogenation of unsaturated fats, and production of calcium bisulfite liquor. Extensive studies have been published concerning the hydrodynamics of three-phase fluidized beds, such as expansion [l-S], pressure drop [ 9 J, gas and liquid hold up [10-14], minimum fluidization velocity [izj and axial mixing [8, 10, 14-17]. 

In commercial hydrogenation, nickel is used to catalyze the hydrogenation of unsaturated fats in vegetable oils to produce solid products containing saturated fats. 

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