Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
PROCESS FOR PURIFYING AQUEOUS SOLUTION
OF NON-ELECTROLYTIC ORGANIC SUBSTANCE TO
HIGH PURITY
Back~round of_the Invention
The present invention relates to a process for
purifying an ag~leous solution of a non-electrolytic
organic substance to a high purity.
An aqueous solution of a non-electrolytic
organic substance such as glucose, isomerized sugar, malt
syrup, sorbitol, xylose, inositol, maltose, cane sugar,
honey, glyoxal, glycerin or gelatin contains pigments,
salts, organic acids and the like as impurities. Not
only adsorbents such as bone black and active carbon but
also ion exchange resins are vigorously used for purifying
a~ueous solutions of this type. As the conventional ion
exchange process widely used for purifying these aqueous
solutions, there can be mentioned a process in which an
a~ueous solution is first treated in a column packed
solely with a hydrogen type strongly acidic cation exchange
resin, is then treated in a column packed solely with a
free base type weakly basic anion exchange resin and is
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finally treated in a column packed with a mixture of a
hydrogen type strongly acidic cation exchange resin and a
hydroxyl group type strongly basic anion exchange resin,
whereby the aqueous solution is decolori~ed and purified.
However, this resin, whereby the aqueous solution is
decolorized and purified. However, this process is
defective in that the pH value of the liquid which has
been passed through the ion exchan~e resin is reduced
with the lapse of time or the liquid is gradually colored
by concen-tration under heating. Accordingly, it of-ten
happens that the quality of the product is degraded or
the productivity is reduced.
It is an object of the present invention to
provide a process in which an aqueous solution of a
non-electrolytic organic substance is purified to a high
purity by using ion exchange resins and a treated product
having a high quality is prepared.
Summary of the Invention
In accordance with the present invention, there
is provided a process for purifying an aqueous solution
of non-electrolytic organic substance to a high purity,
whcih comprises subjecting an aqueous solution of a
non-electrolytic organic substance to a cation-removing
treatment with a hydrogen type strongly acidic cation
exchange resin, and passing the agueous solution through
a column having a free base type weakly basic anion
exchange resin packed in the upper layer portion and a
hydroxyl group type strongly basic anion exchange resin
packed in the lower layer portion, the amolmt of the
hydroxyl group type strongly basic anion exchange resin
being 5 to 50 percent by volume based on the ~ree base
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type weakly basic anion exchange resin and said hydroxyl
group type strongly basic anion exchange resin having a
porous resin matrix structure containing a dimethylhydroxy-
ethylbenzyl ammonium group as the exchange group.
Brief Description of the Drawi~
Figs. 1 and 2 show graphs of the pH values and
electric conductivities of effluen-ts obtained in the
examples of the present invention.
Detailed Descr ption of the Invention
It has now been found that if an agueous solution
of a non-electrolytic organic substance which has been
subjected to a cation-removing treatment with a hydrogen
type strongly acidic cation exchange resin is passed
through a column of a free base type weakly basic anion
exchange resin to which a hydroxyl group type strongly
basic anion exchange resin having a dimethylhydroxyethyl
benzyl ammonium group as an ion exchange group and a
porous resin matri~ structure is add~d in the form of a
layer in an amount of 5 to 50 percent by volume, a very
excellent salt-removing effect can be attained. It is
preferred that the free base type weakly basic anion
exchange resin and the hydroxyl group strongly basic
anion exchange resin be packed in the upper and lower
layer portions of the column, respectively, by utilizing
the difference of the specific gravity be-tween the two
resins. According to the process of the present invention,
impurities in the agueous solution of the non-electrolytic
organic substance, that cannot easily be removed by the
conventional weakly basic anion exchange resins, can be
effectively removed by the ion exchange. Therefore,
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ideal desalting and purification can be accomplished
without occurrence of the above-mentioned troubles
encountered in the conventional techni~ue.
In the process of the present invention, the
hydroxyl group type strongly basic anion exchange resin
is added preferably in an amount of 5 to 20 percent by
volume based on the free base type weakly basic anion
exchange resin.
As the free base type weakly basic anion exchange
resin that can be effectively used in the present invention,
there can be mentioned, for example, styrene type anion
exchange resins such as DOWEX 66 (the trademark of The
Dow Chemical Company), Amberlite IRA-93 (the trademark of
Rhom & Haas Co., USA) and Dia-Ion WA-30 (the trademark of
Mitsubishi Kasei Kogyo Kabushiki KAISHA). As the porous
hydroxyl group type strongly basic anion exchange resin
having a dimethylhydroxyethylbenzyl ammonium group as the
exchange group, there can be mentioned anion exchange
resins such as DOWEX MSA-2 and Amberlite IR-910. As the
hydrogen type strongly acidic ca-tion exchange resin,
there can be mentioned, for example, DOWEX 88 and Amberlite
IR-200.
The present invention will now be described in
detail with reference to the following exampl~s that by
no means limit the scope of the invention.
Example 1
An aqueous solution of beet sugar which had
been subjected to a cation-removing treatment with a
hydrogen type strongly acidic cation exchange resin is
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subjected to an anion-removing treatment in a column
having 2 ml of DOWEX 66 of the free base type (porous
styrene type anion exchange resin manufactured by The Dow
Chemical Company) packed in the upper layer portion and
0.2 ml of DOWEX MSA-2 of the hydroxyl type (porous styrene
type anion exchange resin manufac-tured by The Dow Chemical
Company) according to the process of the present invention,
and the obtained results are compared with ~he results of
the conventional process.
More specifically, an aqueous solution of beet
sugar (BX = 15.1, pH - 2.1, electric conductivity = 2200
~V), which had been subjected to the cation-removing
treatment, is introduced into the resin column at a space
velocity of 6, and the pH value and electric conductivity
of the effluent are continuously measured to obtain a
graph of a solid line shown in Fig. 1. In the drawings,
the pH value and electric conductivity are plotted on the
ordinate, and the time and flow amount are plotted on the
abscissa.
The treatment is carried out under the same
conditions as described above by using a resin column in
which DOWE~ 66 alone is packed, and the p~ value and
elec~ric conductivity of the effluent are measured to
obtain a graph of a broken line shown in Fig. 1.
As is apparent from these graphs, according to
the process of the present invention, a much higher
salt-removing effect than the effect attainable by the
conventional process can be attained, and the amount
treated of the aqueous solution is increased.
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Example 2
The aqueous solution of isomerized sugar (BX =
37.2, pH = 2.0, electric conductivi-ty = 1000 ~V), which
had been subjected to a cation-removiny treatment with a
hydrogen ~type strongly acidic cation exchange resin, is
introduced into a column having the same structure as
that of the column used in Example 1, and the ph value
and electric conductivity of the effluent are continuously
measured to obtain a graph of a solid line shown in
Fig. 2.
The treatment of the conventional process is
carried out in the same manner as described in Example 1,
and the pH value and electric conductivity of the ef~luent
are measured to obtain a graph of a broken line shown in
Fig. 2.
From these graphs, it will readily be under-
stood that accordin~ to the process of the present
invention, a much higher salt~removing effect than the
effect attainable by the conventional process can be
attained and the amount treated of the aqueous solution
is increased.
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