Hydrogenation edible oils

Each common fat or oil has a definite crystal habit that is determined by four factors (1) palmitic fatty acid content, (2) distribution and position of palmitic and stearic fatty acids on the triglyceride molecule, (3) degree of hydrogenation, and (4) the degree of randomization. Table 10 identifies the crystal habit of hydrogenated edible oils (27). 

In the crystallization of hydrogenated edible oil products, the sensible heat of the liquid is removed until the temperature of the product is equal to the melting point. At the melting point, heat must be removed to allow the crystallization of the product. The quantity of heat associated with this phenomenon is called heat of crystallization. Sensible heat (specific heat) of most common hard fat products is equal to about 0.27 cal/g (0.5 Btu/lb) and the heat of crystallization is equal to 27.8 cal/g (50Bm/lb). The amount of heat that must be removed to crystallize hardened oil is 100 times the amount of heat that must be removed to lower the product temperature (39). 

An example of immersion stabilization is nickel catalysts for the hydrogenation of edible oils. ° The nickel catalyst is a powder that is used in batch slurry reactors. Since nickel is pyrophoric, the material must be stabilized for shipment to end user plants. After reduction in a fluid bed furnace, the catalyst is dropped under a N2 atmosphere into melted, fully hydrogenated edible oil. The thick slurry is then pastillated into droplets and solidified at room temperature. The result is small droplet-shaped solids of reduced nickel catalyst embedded in hardened edible oil. When used at the edible oil facility, the fully hydrogenated oil readily... 

With the aim to hydrogenate edible oil, we have prepared highly loaded Ni/SiOs catalysts, by a deposition-precipitation method and showed that the use of FC Celite, a silica support, turned the catalysts more efficient than the ones prepared with other Celite mat rials, either with lower or higher surface area (12). However, with high Ni loading, it is difficult to correlate the variations... 

The composition of an oil and the progress of its hydrogenation is expressed in terms of its iodine value (IV). Edible oils are mixtures of unsaturated compounds with molecular weights in the vicinity of 300. The IV is a measure of this unsaturation. It is found by a standardized procedure. A solution of ICl in a mixture of acetic acid and carbon tetrachloride is mixed in with the oil and allowed to reac t to completion, usually for less than I h. Halogen addition takes place at the double bond, after which the amount of unreacted iodine is determined by analysis. The reaction is... 

For edible oils the temperature is kept at about 180°C (3.56°F). Consumption of hydrogen per unit change of IV is... 

FIG. 23-32 Stirred tank hydrogenator for edible oils, (Votator Division, Chemetron Corporation. )... 

Semibatch hydrogenation of edible oils has a long history and a well-estabhshed body of prac tice by manufacturers and catalyst suppliers. Problems of new oils, new specifications, new catalyst poisons,... 

This recommended practice applies to equipment in refineries, petrochemical facilities, and. chemical facilities in which hydrogen or hydrogen-containing fluids are processed at elevated temperature and pressure. The guidelines in this recommended practice can also be applied to hydrogenation plants such as those that manufacture ammonia, methanol, edible oils, and higher alcohols. 

Hydrogenation of fats and edible oils H2 + unsaturated oil Ni Saturated oil... 

The contactor finds extensive use where high performance phase separation and countercurrent extraction or washing in the one unit are required. Particularly important applications are the removal of acid sludges from hydrocarbons, shown in Figure 13.40, hydrogen peroxide extraction, sulphonate soap and antibiotics extraction, the extraction of rare earths such as uranium and vanadium from leach liquors, and the washing of refined edible oils. 

Hydrogenation Hydroformylation 100-300 edible oils hydrogasification hydrocracking desulfurization catalytic cracking naphtha hydroforming coal liquefaction fatty alcohols 1-6-hexanediol 1-4-butanediol hexamethylenedi amine C4 to Cl5 products... 

In reversible reactions, or when the concentrations of intermediates affect the product distribution (as in edible-oil hydrogenation [9]), mass transfer of the products from the particle to the liquid phase may strongly affect the selectivity. 

The supercritical fluid extraction of oil seeds has been investigated extensively by several authors [34,98]. Possible applications of supercritical fluids in the edible-oil industry include deacidification, deodorization, and fractionation of crude oils and chemical conversion (like hydrogenation, and enzymatic reactions). 

Hydrogenation and dehydrogenation employ catalysts that form unstable surface hydrides. Transition-group and bordering metals such as Ni, Fe, Co, and Pt are suitable, as well as transition group oxides or sulfides. This class of reactions includes the important examples of ammonia and methanol syntheses, the Fischer-Tropsch and oxo and synthol processes and the production of alcohols, aldehydes, ketones, amines, and edible oils. 

EDIBLE OIL. As commonly used, the term refers to any fatty oil obtained from the flesh or seeds of plants that is used primarily in foodstuffs (margarine, salad dressing, shortening, etc.). Among these are olive, safflower, cottonseed, coconut, peanut, soybean, and com oils, some of which may be hydrogenated to solid form. They vary in degree of... 

Hydrogenation has been a useful process to increase the oxidative stability of edible oils, because it changes polyunsaturated FA to monounsaturated and saturated FA (141-143). 

Interesterification of edible oils is an important process for the modification of physical and functional properties, as are hydrogenation and fractionation. 

The reaction mechanism for the selective hydrogenation of edible oils is very complex. Figure 14.1 illustrates a reaction scheme for linoleic acid. In this scheme, (n m) is used to represent an oil with n carbon atoms and m double bonds. There are several parallel, consecutive, and side reactions. Oleic acid (cis 18 1) is the desired product when the reaction starts with linolenic (all-cis 18 3) or linoleic acid (cis, cis 18 2). In the hydrogenation of linolenic and linoleic acid, elaidic acid (trans 18 1) is formed in a cisjtrans isomerization reaction. From the viewpoint of dietics, elaidic acid is an undesirable product however, its presence increases the melting point of the product in a desirable way. Stearic acid (18 0) is formed in a consecutive reaction, but direct formation from linoleic acid is also possible. 

Slurry reactors find many applications in chemical industry. Most of these arc heterogeneous catalytic processes with hydrogenation of edible oils as the most classic example and SASOL s novel continuous Fischer Tropsch slurry synthesis process [1], the latest impressive new development in this area. Doraiswamy and Sharma [2] identified over 50 different slurry reactor applications, and an updated list would no doubt be longer still. 

Mondal, K., and Lalvani, S. 2000. A second-order model for catalytic transfer hydrogenation of edible oils. J. Am. Oil Chem. Soc., 77,1-8. 

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