Vegetable oils, catalytic hydrogenation

In some applications such as catalytic hydrogenation of vegetable oils, slurry reactors, froth flotation, evaporative crystallisation, and so on, the success and efficiency of the process is directly influenced by the extent of mixing between the three phases. Despite its great industrial importance, this topic has received only limited attention. 

Flash fires and explosions which frequently occurred on discharge of the hot products of catalytic hydrogenation of vegetable oils were attributed to formation of phosphine from the phosphatides present to a considerable extent in, e.g., rape-seed and linseed oils. 

Catalytic hydrogenation of vegetable oils is widely used to form harder fats and to decrease the content of polyunsaturated fatty acyl groups. The products have a greatly increased resistance to rancidity. However, they also contain fats with trans double bonds as well as isomers with double bonds in unusual positions.251 253 Such compounds may interfere with normal fatty acid metabolism and also appear to affect serum lipoprotein levels adversely. Trans fatty acids are present in some foods. One hundred grams of butter contain 4-8 g, but hydrogenated fats often contain much more. It has been estimated that in the United States trans fatty acids account for 6-8% of total dietary fat.253... 

Hydrogenation These catalysts are used to add hydrogen to unsaturates, as in the hydrogenation of vegetable oils to form hardened oils. Most catalytic systems consist of nickel or a noble metal on a support. 

Catalytic Hydrogenation of Vegetable Oils Catalytic hydrogenation, used in the food industry, converts double bonds in the fatty acids of the oil triacylglycerols to —CH2—CH2—. How does this affect the physical properties of the oils ... 

CATALYTIC HYDROGENATION OF VEGETABLE OILS FOR EDIBLE FOOD PRODUCTS... 

A mechanical mixture of milk with beef tallow under pressure was patented in 1869 with the name oleo-margarine as an alternative for butter and pork fats. Its production grew, but it was soon superseded by the introduction of fats made by the catalytic hydrogenation of vegetable oil. Around 120 Mt/a of fats (ie., solids) and oils (ie., liquids) are produced world-wide of which ca. 10 Mt/a is margarine (known as spread in the UK), currently produced in more than 60 countries. 

Catalytic hydrogenation of vegetable oils is widely used to form harder fats and to decrease the content of polyimsaturated fatty acyl groups. The products have a greatly increased resistance to rancidity. However, they also contain fats with trans double bonds as well as isomers with double bonds in unusual positions. ... 

Similarly, catalysis is being used to an ever increasing extent for the production and transformation of individual organic compounds, a development which started with the catalytic hydrogenation of vegetable oils and fats and which led to the acceptance and daily use of cataljrtic methods in the pharmaceutical and related industries. 

A few fatty acids with trans double bonds (trans fatty acids) occur naturally, but the major source of trans fats comes from partial hydrogenation of vegetable oils in, for example, the preparation of margarine. The same catalysts that catalyze the hydrogenation of the double bonds in a triacylglycerol also catalyze their stereoisomerization. The mechanism for conversion of a cis to a trans double bond follows directly from the mechanism of catalytic hydrogenation (see Section 6.1) once one realizes that all of the steps in the mechanism are reversible. 

The most catalytic or noncatalytic processes involving reactions in multiphase systems. Such processes include heat and mass transfer and other diffusion phenomena. The applications of these processes are diverse and its reactors have their own characteristics, which depends on the type of process. For example, the hydrogenation of vegetable oils is conducted in a liquid phase slurry bed reactor, where the catalyst is in suspension, the flow of gaseous hydrogen keeps the particles in suspension. This type of reaction occurs in the gas-liquid-solid interface. 

Three-phase catalytic reactions are solid-catalysed reactions taking place between one reactant in the gas phase and another reactant in the liquid phase. An example of a three-phase catalytic reaction is the hydrogenation of vegetable oil in the presence of a Ni catalyst ... 

Raney nickel A porous solid catalyst made from an activated alloy of nickel and aluminium. The nickel is the catalytic metal with the aluminium as the structural support It was developed by American mechanical engineer Murray Raney (1885-1966) in 1926 for the hydrogenation of vegetable oil and is now used in hydrogenation reactions in various forms of organic synthesis. It is widely used as an industrial catalyst for the conversion of olefins and acetylenes to paraffins, nitriles, and nifro compounds to amines, and benzene to cyclohexane amongst others. 

Metals and alloys, the principal industrial metalhc catalysts, are found in periodic group TII, which are transition elements with almost-completed 3d, 4d, and 5d electronic orbits. According to theory, electrons from adsorbed molecules can fill the vacancies in the incomplete shells and thus make a chemical bond. What happens subsequently depends on the operating conditions. Platinum, palladium, and nickel form both hydrides and oxides they are effective in hydrogenation (vegetable oils) and oxidation (ammonia or sulfur dioxide). Alloys do not always have catalytic properties intermediate between those of the component metals, since the surface condition may be different from the bulk and catalysis is a function of the surface condition. Addition of some rhenium to Pt/AlgO permits the use of lower temperatures and slows the deactivation rate. The mechanism of catalysis by alloys is still controversial in many instances. 

Hydrogenated vegetable oil, in cosmetic molded sticks, 7 840t Hydrogenation(s), 13 769 acetylene, 1 180 10 613-614 alkylanthraquinone, 14 47 asymmetric, 5 210—212 butadiene, 4 370 carbon monoxide, 5 3 carbon dioxide, 26 881 catalytic, 10 504 catalytic aerogels for, l 763t chlorocarbons, 6 235 conditions of, 10 810 cyclopentadiene and dicyclopentadiene, 8 224-225... 

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