Adsorbent for treatment of oils and/or fats

Details Adsorbent for treatment of oils and/or fats Adsorbent for treatment of oils and/or fats

1997-08-15

1999-06-29

Geist, Gary

Organic compounds -- part of the class 532-570 series

Organic compounds

Fatty compounds having an acid moiety which contains the...

554191, 502 63, 502 81, 502238, 502407, 423112, C11B 310

Patent

active

059170697

DESCRIPTION:

BRIEF SUMMARY
CROSS-REFERENCES TO RELATED APPLICATIONS NOT APPLICABLE



BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention concerns an adsorbent that is particularly suited for treatment of mineral, vegetable and/or animal oils and/or fats, especially for removal of coloring matter.
Adsorbents with exchangeable cations are already known for this purpose and belong to three groups in particular:
2. Description of the Related Art
So-called fuller's earths have been used since the mid-19th century for purification of vegetable oils, animal fats and mineral oils. These include bentonites (especially Ca bentonites) of preferably acid origin, but also natural mixtures of palygorskite and smectite also preferably of acid origin. These naturally active clays are generally only dried and ground. Relative to their bleaching activity in vegetable and mineral oils there is therefore considerable dependence on natural properties. These clays are modified if necessary with limited amounts of acid so that the adsorption effect can be optimized within limits (EP-A-0 398 636).
Acid-activated bentonites that proved to be superior in action to natural fuller's earths have been on the market since about 1908 (O. Eckart, Die Bieicherde, page 9 (1929), Verlag Serger & Hepel, Braunschweig). Acid-activated bentonites (bleaching clays) are produced by therefore treating bentonite suspensions with hot mineral acids (for example H.sub.2 SO.sub.4, HCl).
The main mineral montmorillonite of the bentonite raw material is a natural, swellable layered silicate constructed of silicate lamellae stacked one on the other. Each lamella consists of two (SiO.sub.4) tetrahedral layers, between which an (Al(OH).sub.4 O.sub.2) octahedral layered is situated. Montmorillonite is a so-called dioctahedral layer silicate, i.e., only two of the three possible octahedral gaps is occupied by aluminum ions. The Al ions in the octahedral gaps can be isomorphically replaced by divalent cations, like Mg ions. Replacement of the trivalent Al ion with the divalent Mg ion leads to a negative excess charge in the crystal. This negative excess charge is equalized between the silicate lamellae by cations, like Na.sup.+, Mg.sup.2+, Ca.sup.2+, so that electrical neutrality overall exists. The cations situated between the layers are exchangeable by other cations, for which reason bentonites are cation exchangers.
During acid activation acid attack occurs in the octahedral layer of the silicate lamella. The cations situated in the octahedral layer, like Al.sup.3+, Mg.sup.2+ and Fe.sup.3+, are dissolved The exchangeable cations after acid activation essentially consist of Al.sup.3+ ions (20 to 50% of the ion exchange capacity (IEC)), Mg.sup.2+ and Ca.sup.2+ ion (about 30%) and Fe.sup.3+ ions (about 10%). Between 10 and 20% of the exchangeable cations are present as H.sub.3 O.sup.+, which was inserted by acid treatment. According to the type of acid treatment the ratio of exchangeable cations can be varied somewhat, but it is not possible to raise the amount of exchangeable Al.sup.3+ (expressed in % of the total IEC) significantly above 50%.
After acid activation a core that still exhibits the montmorillonite structure remains, which is enclosed by a layer of amorphous silicic acid (formerly the tetrahedral layer of the montmorillonite structure) (cf. Ullmann's Encyclopadie dertechnishen Chemie, Vol. 23, page 322 (1983)).
By acid attack the cation exchange capacity of bentonite is reduced, depending on its origin, from 50 to 120 meq/100 g of bentonite as a function of the intensity of acid attack to about 20 to 80, especially 30 to 50 meq/100 g, for which the remaining montmorillonite core is responsible. Ca.sup.2+, Mg.sup.2+, Al.sup.3+ and Fe.sup.3+ ions are preferably situated between the layers as exchangeable cations. Each employed crude clay exhibits an optimum with respect to bleaching activity in vegetable oil relative to the remaining cation exchange capacity after acid treatment. The specific surface area, depending on the crude clay, initially rises with in

REFERENCES:
patent: 3725528 (1973-04-01), Banin
patent: 3755183 (1973-08-01), Fahn et al.
patent: 3902886 (1975-09-01), Banin
patent: 4812436 (1989-03-01), Staal et al.
patent: 5079208 (1992-01-01), Lammers et al.
patent: 5369069 (1994-11-01), Suzuki et al.
patent: 5486499 (1996-01-01), Davies et al.
Ullmans Encyclopedia of Technical Chemistry Verlag Chemie, Weinheim, 4.Aufl., Bd. 23, 1977.

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