Liquid purification or separation – Processes – Chromatography
Patent
1996-10-18
1998-03-24
Therkorn, Ernest G.
Liquid purification or separation
Processes
Chromatography
127 462, 162 16, 162 36, 2101982, B01D 1508
Patent
active
057308772
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for fractionating a solution into two or more fractions enriched with different components. In particular, the invention relates to a method for fractionating a solution by a chromatographic simulated moving bed method in which the liquid flow is effected in a system comprising at least two chromatographic sectional packing material beds in different ionic forms, in which the dissolved substances present in the solution are separated from each other, and if the solution to be treated comprises substantial amounts of ions, the system also comprises a unit where the ion equilibrium of the solution is changed.
Fractionation of a solution comprising many dissolved substances into fractions enriched with different components is often necessary to recover the desired components as pure as necessary. The method of the invention can be employed to carry out such fractionation. A sulphite cooking liquor, for instance, can be fractionated by the method so as to give a fraction rich in monosaccharides and/or a fraction rich in lignosulphonates; furthermore, molasses or vinasse can be fractionated in this way to obtain fractions rich in a sugar, such an sucrose, and/or betaine.
The method of the invention is particularly well suitable for recovering monosaccharides from a sulphite cooking liquor, particularly for recovering xylose from a hardwood sulphite cooking liquor, in a continuously operated process by which also a fraction enriched with lignosulphonates can be recovered, if desired.
Sulphite cooking liquor in this context denotes liquor employed in sulphite cellulose cooking, liquor obtained after such cooking, or a part thereof.
It is known per se to use ion exchange resins of different ionic forms in chromatographic separation methods. Finnish Patent 59 388 describes chromatographic separation of polyols, employing columns packed with a cation exchange resin in different ionic forms (resin with a polystyrene skeleton cross-linked with divinylbenzene and activated with sulphonic acid groups). Finnish Patent 69 296 discloses a chromatographic method for the fractionation of polyols, in particular to obtain pure xylitol. Also this method employs a resin with a polystyrene skeleton cross-linked with divinylbenzene and activated with sulphonic acid groups, packed in parallel columns; in some columns, the resin is in earth alkaline form and in the other columns in Al.sup.3+ or Fe.sup.3+ form.
U.S. Pat. No. 4,631,129 discloses the separation of sugars and lignosulphonates from a sulphite spent liquor by a process comprising two chromatographic treatments with ion exchange resins in different ionic forms. In the first treatment, the sulphite spent liquor is introduced into a chromatographic column comprising a strong acid resin used as column packing material in metal salt form; the metal ion is preferably a metal ion of the spent liquor, usually calcium or sodium. A substantially sugarless fraction rich in lignosulphonates and a fraction rich in sugars are obtained from this column by elution. The latter fraction is subjected to a softening treatment, and its pH is adjusted to be in the range 5.5 to 6.5, whereafter it is introduced into the second chromatographic column containing resin in monovalent form, and a second fraction rich in sugars and a second fraction rich in lignosulphonates and salts are obtained therefrom by elution. It is stated in this patent that the process is capable of recovering sugars, e.g. xylose contained in hardwood sulphite spent liquor, in a very high purity and high yields. However, a drawback of the method is that the dry solids profile which has been formed in the first chromatographic treatment and in which the components are already partly separated is destroyed in the softening treatment and pH adjustment and thus cannot be utilized in the second chromatographic treatment. The method is also complicated by the steps of concentration and additional pumping to which the solution is subjected. All of these factors add to investment costs. Furt
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Heikkila Heikki
Kuisma Jarmo
Paananen Hannu
Therkorn Ernest G.
Xyrofin Oy
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