Edible oils, hardening

DELOXAN AP II supported platinum catalysts in sc CO2 are less active than DELOXAN AP II supported palladium catalysts, but they show an improved linoleate selectivity and a significantly lower cis-trans isomerization rate. The overall yield of undesirable trans fatty acids is 7.5 GC area-% in the edible oil hardening with a DELOXAN AP II supported 2 wt. % platinum catalyst. In a batch hydrogenation using the commercial powdered nickel on kieselguhr catalysts the undesirable trans fatty acid content was determinded to 40 percent. 

Thus an active nickel catalyst may be prepared simply by heating the formate in oil at around 240°C for about 1 h this method has been employed in the oil-hardening industry for the preparation of a wet-reduced catalyst,42 although the decomposition temperature is too high for normal oil-hardening and the catalyst may not be prepared directly in a hydrogenation tank, particularly for edible purposes. Nickel formate is prepared by the reaction between nickel sulfate and sodium formate,43 or the direct reaction of basic nickel carbonate44 or nickel hydroxide with formic acid.31... 

To overcome the existing problems with the state-of-the-art technology in edible oil and free fatty acid hardening, we decided to have a look on hydrogenation reactions in sc CO2 using precious metal fixed bed catalysts on acid resistant supports. 

Edible oils and fatty acid esters were selectively hardened in sc CO2 at temperatures between 60°C and 90°C and at a total pressure of 10.0 MPa. In order to get different degrees of hardening, we investigated activated carbon and different DELOXAN supported precious metal fixed bed catalysts at space velocities (LHSV) between 5 and 60 h1. 

Selective hardening of edible oils in discontinuous stirred tank reactors (STR), continuous trickle bed reactors and in continuous flow reactors operating with supercritical CO2... 

The only useful commercial catalyst now used is nickel, available at a 17-25% level on a support and suspended in hardened edible oil or tallow. This preserves the activity of the nickel in a form in which it can be safely and easily handled. Catalyst can be recovered and reused but will be less active. Reaction is usually effected at temperatures between 180°C and 200°C and at a pressure of about 0.3 MPa (3 bar). The catalyst is quickly poisoned by fatty acids, soaps, phospholipids, oxidized acids, sulfur compounds, halogen compounds, carbon monoxide, oxygen, and water. As a consequence, both the oil and the hydrogen should be as pure as possible. 

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... 

The lengths of the pores in the catalyst particles can severely affect the selectivity of catalytic reactions. For a fairly rapid reaction leading to a product that is liable to further reaction to undesirable products, equally rapid removal of the desired initial reaction product from the pore system of a catalyst particle is necessary. Extensive research (Unilever) has been performed on the properties of nickel catalysts for the hardening (partial hydrogenation) of edible oils [7]. Catalyst pres-... 

The hardening of oils and fats by hydrogenation is an important industrial process - with worldwide production of hardened oils in excess of four million tons. Product applications include edible oils, margarine, mayonnaise, frying fats, confectionary, cosmetics, tyres, plastics and many more. The application of this reaction is growing at a significant rate. 

In the production of edible oils from oil seeds and oil-rich fruits it is necessary to process the crude oil to separate pure oil (olein) from the crystalline solids (stearin), the amount of each depending on the temperature of the process. The growing importance of pahn oil processing meant that the traditional rotary vacuum filter was not sufficiently effective in this separation, and the Florentine filter was developed to enable higher processing rates in a continnons flow. This dry fractionation step is used in the treatment of a wide range of oils and fats, from 2°C (hardened soybean oil) up to 45°C (tallow). 

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