Note: Descriptions are shown in the official language in which they were submitted.
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SUPERCRITICAL SEPARATION PROCESS
FOR COMPLEX ORGANIC MIXTURÆS
CB~SX~D 0~ THE n~NTIQN
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1. F~ED OF TEE n~n~TICN
: The present invention relates qenerally to the separation of complex
organlc mixtures~into varlous components and, more particularly, to
:processes of separating low molecular weight fractions from complex organic
: mixtures utilizing supercritical solutions. Specifically, the present
m vention~relates~to~the~supercritical separation:of low molecular weight
components~rom~compl~ex organlc mixtures utllizing supercriticdl carbon
dioxide modified by the presence of an entrainer.
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2. DES~RIPTI~N OF T~ PRI~R A~T
There are a wlde variety of lndustrial biomass processing systems which
produce waste ~treams containing substantial portions of useful
constituents. Examples of such industxial syste~s include those involved
in the manufacturing of pulp and paper such a~ black liquor solutions in
kraft p~oeesses, in the production of cheese and whey, and in other biomass
process mg ~ystems. The annual vol~me of such ~aste processing streams is
very substantial. muS, there have been numerous efforts over ~he years to
separate useful components from such waste streams for the purpose of
recirculation within the processing system, for the separate sale and/or
use of such components, or for environmental purposes to remove
environmentally damaging components from the waste streams. Due to the
volume involved in such indus~xial systsms, economic factors such as the
complexity of the separation process or the energy requirement for such
separatlon processes become extremely impor~ant as compared to the
ef~icie ~ of the separation proce~s as well as the effectiveness in terms
of extraction capability.
For example, the kra~t process of conv~rting w od $nto cellulose pulp
includes treating the lignocellulosic material with sodium
hydr~xide/sulfide solutions. During this process, lignins are di~solved
and hemicelluloses are degrad~d to a complex mixture of orgamc compounds
including various carboxylic acids such as sa~charinic acids~ Low
molecular weight components such as phenolic compounds derived from lignins
are present in streams of the black liquox or in washing operations such as
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preparation of chem1cally pure cellulose by dissolution o pulp m alkaline
solutions.
The separation of large molecular weight components is relatively
straightforward and many prior art techniques have been developed to
separate such high molecular weight components from the complex orgamc
mixtures. Some techniques have also been developed for the separation of
the lo~ molecular weight fractions. These prior art techniques contain
many stages involving ion exchange, adsorption steps, water evaporation,
distillation, and other purification operations. These standard and well
known procedures are very complex and expensive to operate. In order to
increase the efficiency of separation, use of supercritical fluids to
enhance separation has been developed. U.S. Patent No. 3,969,196 is an
example wherein a number of organic compounds are separated utilizing a
wide variety of supercritical fluids including carbon dioxide. While
carbon dioxide is a desirable supercritical fluid due to its relative
availability and inexpensiveness, this particular reference was unable to
separate the more complex polyhydroxy compounds and other complex phenolic
lcw molecular weight compounds utilizing carbon dioxide and, instead, had
to utilize different supercritical fluids having differing solvation
characteristics. m Pse supercritical fluids are more complex to handle and
more expensive than supercritical carbon dioxide.
Other references which disclose the use o~ car~on dioxide in separation
- processes include U.S. Patents No. 2,772,965, No. 4,349,415, No. 4,437,939
and No. 4,474j994. None of these references illustra~e the use o~
superoritical carbon dioxide to extract the more co~plex phenolic low
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molecular weight constituents from complex organic mixtures, nor do they
illustrate the mcdi~ication of the carbon dioxide solvating power by the
addition of entrainers. Thus, these known processes do not address the
effective separation of simple and complex low molecular weight
cons~ituents of complex organic mixtures (phenolic, complex hydroxyacids)
from biomass processing systems utili~ing inexpensive supercritical fluids.
U.S. Patents No. 2,631,966, No. 2,632,030 and No. 2,698,278 all
illustrate the use of li ~id carbon ~ioxide with other co-solvents for
separation purposes. However, these patents ~re limited to petroleum
refining and do not deal with carbon dioxide at supercri~ical conditions,
that is supercritical temperature and pressure conditions. Moreover, the
compounds present in oil stocks for petroleum refining have very little in
common with separation processes of complex organic mixtures derived from
i biomass processing systems as discussed above.
Thus, there remains a need for relatively simple processes of
extracting useful low molecular constituents from complex organic mixtures
derived from biomass processing stxeams. For such processes to be
economically effective, they must preferably utilize mild temperature
conditions and intermediate pressure ranges, they must be simple, and they
must utilize relatively inexpensive chemical components as well as
simplified hardware.
S=XP~Y OF DEE nNVEN~IoN
Accordingly the present invention seeks to provide a
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simplified and economic process for separating low molecular weight
fragments or components from complex organic mixtures.
Further the present invention seeks to provide a process for
modifying the solvation characteristics of supercritical carbon dioxide to
increase its effectiveness in extract mg low molecular weight components,
including complex components, from complex organic mixtures derived from
biomass processing systems.
Still further the present invention seeks to provide an economic
supercritical extraction process for the separation of low ~olecular weight
components from lignin-containing organic mixtures derived from various
biomass processing systems such as the kraft wcod pulp process.
Further still the present invention seeks to provide a process for
separating complex polyhydroxy compoun~s, co~plex phenols, lcw ~olecular
weight lignin-containing compounds and hydroxycarboxylic acids from complex
organic mixtures.
Still further the present invention seeks to provide a
process-for separating high-value hydroxy acids and co~plex amino acids
from solution, useful in food processing and pharmaceutical synthesis.
Additional aspects, advantages and novel features of the present
invention shall`be set forth in part in the description that follcws, and
in part will become apparent to those skilled in the art upon examination
of the foregoing or may be learned by the practice of the invention. The
and advantages may be realized and attained by means of the
instrumentalities and in combinations particularly pointed out in the
appended claims.
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To achieve the foregoing and in accordance with the purpose
of the present mvention, as embodied and broadly described herein,
a process is disclosed for separating low molecular weight compcnents from
complexaqueous organic mixtures. The process includes preparing
a separation solution of supercritical carbon dioxide with an effective
amount of an entralner to modify the sulvation power of the supercritical
carbon dioxide and extract preselected low ~olecular weight ComPOnentS.
This separation solution is m2mtained at a temperature of at least about
70 C and at a pressure of at least about 1,500 psi. The separation
solution is contacted with the complex organic mixtures while maintaining
the aforementioned temperature and pressure un~il the mixtures and the
separation solution reach equilibrium to extract the preselected low
molecular weight components from the organic mixtures. Finally, the
entrainer/extracted components portion is isolated from the separation
solution
~RIEF DE~UETICN OF T9E DRAWI~GS
;~ ~ The accompanying drawing which is mcoxporated in and fo~ns a part of
the specification illustrates preferred e~bodiments of the present
invention, and together with the description, serves to explain the
20 ~ principles of the invention. In the drawing:
g. 1 is a graphical illustration showing mvlecular weight fragments
extracted from a black liquor solution utilizing the process of the present
invention.
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The present invention involves a p~ocess for the extraction and
separation of classes of co~ponents from.complex aqueous mixtures of
organic compounds such as those present in liquors fro~ alkaline wccd
5 pulping such as the kra~t process, pulp washing ~n.th alkal~ne solutions for
the manufacture of chemically pure cellulose, cheese manufacturing waste
st~eans and the l~ke. qhe proces utilizes superc~itical car~on dio~de ~n
the presenc~ of entrainers. It was found that supercritical carkon dioxide
in and of itself was i~sufficient to extract the desired low molecular
weight fragments from such complex aqueous organic mixtures, and in
particulax the polyhy~roxy compoun~s and other complex organic material~.
It was found, however, that when effective amounts of entrainers were
incorporated with the supercritical carbon dioxide, such entrainers
modified the solvation power of the supercritical car~on dioxide and
~ tted th~ desired extraction of preselected fragments~
`~ The supercritical solution of ~he invention is maintained at a
temperature of at least 70 C and an operating~condition of at least about
1,500 psi. The pxeferred ranges, as discussed in more detail below,
include a temperatuxe range of 70 - lS0 C and operating pressure~ m the
: ~o range of 1,S00 ~ 4,000 psig.
.
The suFercritical fluid extraction solution is then contacted with the
aqueous solution of the complex mixture of organic compounds until
equllibrium is reached. A counter-current mode is preferably utilized to
achieve this, although any desired p~ocess system may be utili2ed. After
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equilibrium is established between the mixtures, the supercritical solventcontains one or m~re lcw molecular weight components o the complex organic
mixture depending on the nature and the concentration of the entrainar
present in the supercritical solution. It should be noted here, and is
discussed in greater below, that it is possibLe to successiYely extract
different classes of compounds by varying the concentration and~or the
nature of the entrainer present in the supercritical carbon dioxide. In
this manner, the process may be tuned to achieve the desired extraction.
The solution of entrainer/ex~racted components i5 then isolated by reducing
the system pressure, by lowering the temperature, or by a combination of
both. In a preferred embodiment, the pressure is lowered to about 800 psi
or higher. Alternatively, the system's temFerature may be low~red in the
amount of 30 - 50 C from its operational temperature. The
entrainer/extracted material suspen~ion resultin~ fxom this procedure can
then be filtered with the entrainer being recovered a~d recycled.
me broadest application o~ the present invention includes a process
for generally se ~ ating low m~l ~ lar weiqht fra~mentc or components from
soluble complex organic mdxtures. In particular, the separation of certain
components from complex organic mlxtures is of concern wherein the organic
mixtures include substitutecl phenols, hydroxycarboxylic acicls, complex
carbohydrates, amino aclds and the like. Of par~icular concern are
biomass processing streams as previously described and in particular the
kraft process for converting wovd into cellulose pulp. This process system
treats the lignwellulosic material wlth sodium hyc~oxide~sulfide solutions
to c~ssolve lignins and degrade hemicelluloses to a complex mixture of
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cax~oxylic acids mcluding saccharinic acids. The black liquox solution
produced in such process mg syskems is of particular importance because of
the amoun~ of chemicals it contains. Thus, a particularly impor~ant
application of the present invention is the separation and extraction of
low molecular weight compounds, such as s~bstituted phenols and other
phenolic compounds derived from lignins from hydroxycarboxylic acids and
other polyhydro~y compounds. Su~h components are present in streams of the
black liquor or in washing operations relating to the overall kraft
process.
More particularly, black liquor from pulp and paper industry processes
is generally concentrated to about 30 - S0~ volume, and carbon dioxide
(80 psi, 80 C) is then typically utiliz~d to precipitate a~out 70 - 80% of
the lignins present in the liquor, primarily the higher molecular weight
lignin components. The residual solu~ion, which is o concern with the
present invention, contains salts, low molecular weight lignins, and
polyh~droxy compounds such as hydroxycarboxylic acids including sacch~rinic
acids as sodium salts. After separation o the solids by filtration or
centrifugation, the resultin~ liquor is then treated ~ith -the supercriti~al
carbon dioxide separatio~ process of the presen~ inv~ntion to selectively
extxact desired components thexeof.
The entrainers useful wlth the present invention ma~ vaxy depending on
the mixture being separated and the desixed extraction fragments.
Preferably, the entrainer is a low boiling point organic solvent and is
present in approNimately 2 - 30 weight percent of the supercritical carbon
dioxide/entrainer solution to be effec~ive. In add1tion; in oxder to
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~xtract polyhydroxy compounds, the entrainer should include active hydroxy
groups in the presence of water. ~lis ls particularly true in the black
liq~or extraction application of the invention. Suita~le compounds
utilized as entrainers include alcohols such as methanol, ethanol and the
like, ke~ones such as acetone, methylethylketone and the like, and ethers
such as tetrahydrofuran (TE~F) and methyl-t-but~l ether. Such entrainers
will extract low molecular weight fragments preferably in the ran~e of
150 - 400 molecular weight.
As previously indicated, the preferxed ef~ective range of entrainer is
2 - 30 weight percent of the separa~ion solution depending on the entrainer
utilized and/or the desired extxactant. When alcohol is utilized as the
entrainer, the greater the alcohol content, the greater the lignin
extracted from lignin-containing complex organic mixtures. More
speciically, a low alcohol content of about 2 - 5% will extract low
molecular weigh~ phenolics. A medlum alcohol concentration of about
10 - 12% of the supercritical carbon dioxide will extract hydroxy acids
such as lactic acid, and a higher alcohol concentration of ahout 20% or
more will extract the more complex hydroxy acids such as polyhydroxy
carbcxylic acids, and amino acids ~in pharmaceutical processes).
It is also possible to successively extract different classes of
compounds or components from the complex organic m1xture by varying not
only the concentration but also the nature of the entrainer present. For
:
example, in order to extract the polyhydroxy components, the entrainer
utilized must have an active hydroxy group. Moreover, by shifting the
entrainer type~from alcohol to, ~for example, acetone or I~, extraction of
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phenolics is grea~ly enhanced or increased as opposed to extraction of
hydroxy acids or amino acids. Thus, by extensively modifying the solvation
power of the supercritical carbon dioxide by the addition of various types
of entrainers, especially wt.en such entrainers include active hydroxy
groups, separation of a vaxiety of complex lcw molecular weight fractions
can be performed, particularly polyhydroxy compounds. In addition, by
tuning ~he amount of the entrainerf such as alcohol, one can selectively
extract desired components such as progresslvely extracting phenolic
compounds, then simpler hydroxyacids, and then more complex
polyhydroxycarboxylic acids from the black liquor solution. For more
particulars, reference should be made to Table III below.
As previously indicated, the preferred temperature range for
maintaining the supercritical separation solution is between 70 - 150 C.
At temperatures generally below the preferred minimum of 70 C, very little
extraction of low molecular weight fragments is obtained. If the
separation solution is operated at temperatures su~stantially greater than
the preferred 150 C maxlmum, components of~the separation solution begin
to decompose thereby defeatinq ehe effectiveness and capability of the
extraction pr~cess. It is also preferred that the supercritical separation
solution is operated at a pressure range of about 1,S00 - 4,000 psi. These
particular pressure range parameters have been experimentally determined as
being the preferred range to operate the separation solution at or above
the supercritical range o car~on dioxide, which is 31 C at 1,0~9 psig.
Once ~he supercritical separation solution and the organic mixtures
have reached equil~ibrlum, the entrainer/water/extracted fragment
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composition i~ then isolated from the separation solution. This is
achieved either by reducing the pressure or by reducmg temperature or
both. In one preferred orm, the pressure is r~luced to approximately 800
psi, although lower pressures down to 200 psi would wor~ and h~ve been used
experimentally. Howevex, 800 psi or higher is preferred in order to
maintain the carbon dioxide solution as a liquld. In this instance,
suspended particulates are formed, and the suspension is then filtered to
recover the entrainer and solidified f~agments. In an alternate
em~x~nt, the ~olatile e~tra~ner/water is stripped off the solution after
pressure reduction, and the ~ragments are then recGvered. Alternatively,
the temperature may ke reduced. me preferred temperature drop is
30 - 50 C although a greater drop may be us~d. However, it should be
noted that the smaller the temperature drop, the easier it is to recycle
the solution in a continuous process system.
~Xa~eLES I - VIII
A series of ~ ~men~s were performed to determine the parameters and
llmitations indicated above. All experiments were carried out in an
Autoclave Engineer SCE Screening System. All the experiments with liquid
samples were carried out in an extraction vessel which was modified to
include an internal tube through which the supercritical fluid was fed and
bubbled into the liquid aqueous phase to improve the mixing between the
phases. A typical experimental procedure is described to provide a
detailed record ~f exFerimRntal sequence of the operations.
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The carbon dioxide/entram er mixture was prepared in a small cylinder
having a volu~e of about 2.7 liters. The cylinder was carefully emptied by
connecting it to vacuum line and then weighed. The desired amount o~
entrain~r was siphoned into the cyli~der. The cylinder was weighed again
and then prescurized wi~h carbon dioxide to the desired weight. It was
necessary to ~ressurize slowly to ~ ze the carbon dioxide content.
~cw boiling solvents such as methanol or acetone or tetrahydrofuran
tT~) dissolved large amounts o~ carbon dioxide, ~o it was possible to fill
the cylinder with about 300 - 350 g of solvent and 1,200 1,400 g of
carbon dioxide. Solvents like ethanol or isopropanol and possibly
acetonitrile and methylethylk~tone do no~ dissol~e very large a~,ounts of
carbon dioxide so ~hat is was better to fill the cylinder with no mvre than
150 - 200 g of such solvents.
The cyl mder was connected to an extrac~ion reaction sys~em, and a cold
trap (ice, w~ter and sodium chloride) was prepared to cool the carbon
dioxide/entrainRr mi~ture before entering a pump. Usually/ the extraction
~eactor was filled with 10 ml of solution to be ex~racted. It was then
connected and slowly a~d carefully pressurized. Once the pressure began to
rise, ~he solution was then hea~ed to the desired temper~ture.
In a typical experiment ~3,000 psi, 100 C and 20% o~ entrainer), the
pressure in the separating vessel was kept at about 300 psi. Approximately
2.1 cubic foot volume was allowed to pass through th~ reactor before each
fraction was collected. Once the final fractlon was recovered from the
separa~ing vessel, the system Wa5 completely vented. Heating was turned
off when the pressure in the system was at about 1,000 psi during discharge
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of the system. me liquid sample was recovered from the bottom of the
autoclave and weighted. U ually there was a solid at the bsttom and on the
walls of the reactor. This solid sample was careully recovered, dried
under vacuum and weighed.
A series of samples of black liquor were tested utilizing the carbon
dioxide/entrainer process of the presen~ invention wherein the type o~
entrainer utilized was varied~ Samples of the black liquor solution were
prepared, for instance, by pulping selected sp~cies such as pine or aspen
to obtain the kræt black liquors. Additional s~mples were obtained from
the Weyerhaeuser Company. In all these experiments, the volume of black
liquor put into the reactor was 10 ml, containing approximately 1 g of
lignin. Kraft black liquor solutions were first treated to r~move the
higher a~lecular weight lignin components, with the remaining solution
treated with ~he extraction proc~ss of the present invention. Table I
belcw provides the results of this series of e~periments which wexe a
series of extractions o~ aspen kraft black liquor æter precipitation of
high-mol~cular-weigh~ l~gnins wlth carbon dioxide.
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~ar~tity o~
Supercritical Entra~ner
~ ~ ~ ~ Rec~ EXtract, g
1 ~ce~one, 21.1 620 135 0.16
2 Acetone, 2000 625 124 0.14
3 Methanol, 22 . 5 613 153 * 1. 44
4 Methanol, 20.5 830 178 * 1.33
S Ethanol, 19 . 3 460 103 0 . 63
6 Ethanol, 17. 9 5~0 117 0 . 40
7 THF 21.5 51~ 89 0.11
8 ~? 21.5 ~00 119 0.16
* q~he e~tract con~rlsed law molecular weight lignin compounds and
hydro~carko~lic adds.
.
15As can ba seen from Table I above, both acetone and THF
entrainers with the supercritical carbon dioxide extracted
low molecular weight lignins. ~his can also be seen in
F$g. 1 wherein the line denoted hy the numeral 10 indicates
the molecular weight distribution ~MWP) of the residue from
20the black liquor after having been extracted with
supercritical carbon dioxide and acetone, while the line 12
indicates the ~WD of the extracted lignin. As can be seen
from Fig. 1, the extracted llgnin ls in a low molecular
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weight range of approximately ~00, with a small amount of
lignin also in the molecular weight :range of approximately
400. Thus, while the acetone and THF e~trac~ed low
molecular weight lignins, as illustxated, the alcohols as
indicated in Table I extracted hydroxycarboxylic acids in
addition to the low molecular weight lignins~ Moreover,
methanol can also extract some sodium bicarbonate, which is
not extracted with acetone or T~F.
~XAMPLE IX
200 ml o~ crude.black liquor solution was treated by
exposing it to carbon dioxide (80 psi at 80 C) for
approximately three hours. High molecular weight lignin
precipitated out and was separated by centr1fugation. 10 ml
: (11 g) of the supernatant fluid were then extracted using
the process of the present invention, the supercritical
carbon dioxid /methanol entrainer being at 100 C, 3,000
p~ig. With 5~ methanol, 16 mg:of acetovanillone were
obtained with about 5 g of methanol. When th~ methanol
content was increased to about 17%, ~00 mg of a mixture of
lactic and other hydroxy acids were obtained with ahout 50 g
: of methanol. The proportions of methanol/carbon dioxide
needed for an industrial process would be smaller than those
employed in these particular experiments. The operating
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vessel volume was 75 ml and the flow rate of carbon
dioxide/methanol was about 300 - 400 ml/hr. Acetovanillone
contents in the liquor were about 1% of lignin, and the
expected con~ent of saccharinic acids was about 10 - 20%.
This particular appli~ation of ~he proce~ of the invention
would apply to the isolation of acetovanillone and related
compounds and the subsequent isolation o saccharinic acids
from complex mixtures of industrial interes~.
~YAP9PLE X
An experiment similar to Example IX was carried out
using about 17% methanol concentration and the Weyexhaeuser
krat lignin sample described above. From about 2.2 g of
solid material contained in the liquor, 50% wa~ extracted
with 17~ methanol and supercxitical carbon dioxide and 50%
remained in the solid residue. The composition of the
extracted phase and of the solid residue, relative to the
hydroxycarboxylic actds, is lllustrated in Table II below.
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Table II
Compositit)n of Hydro~carbo~lic Acids in Ext:racted Materials and Residue.
(Hydroxymonocar~oxylic Acids ~n g/100 g of mater.ial *)
E;ctract Residue
Lactic 3.17 0 23
Glycolic 1. 22 0 32
2-Hydroxy~utanoic 1. 21 0 . 07
2-Hydro~-2~thylbutanoic0 . 04
2-Hydroxypentenoic 0.19 traces
4-Hydro~butanoic 0.14 ~
2-Methylglyceric 0 . 09 0 02
Glyceric 0 . 03 0 02
3-Deox~rtetronic 0 . 20 0 . 05
3, 4-Dide~ypentonic 1. 71 0 . 27
Arhydroisosaccharinic 0.16 0.05
Xyloisosaccharinic 0 . 44 O .17
3-Dideoxypentonic O . 25 0 09
3, 6-Dideoxyhexonic 0 .11 traces
3, 4-Dideoxyhexonic 0 10 0 02
2 o b~lucoisosaccharinic 3 31 1 30
a~lucoisosacchzr~nic 1.27 0.56
* Li~ residues and salt~ were not analyzed.
The data in Table II illustrate the ability of the high
methanol concentrations to extract simple and cornplex
~hydroxycarboxylic acids. These conditions al50 extract
dicarboxylic acids and glycerol. The ~ are also components
- of the black llquor. The analyses above were carried out
uclng capil lary gas chromatography of fully sylilated
de ~ lvative s ~ :
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EXA}5PLES XI - XXI I
To optimize entrainer concentration and operating
conditions, experiments were perormed with a simple
simulated black liquor solution containin~ acetovanillone
5 (representative of a low-molecular weight lignin derived
compound), lactic acid (a carbohydrate decomposition
product), ~nd gluconic acid (a more complex
hydroxycarboxylic acid, representative of saccharinic
acids) . Table II below summarizes the effects of the
10 various parameters: concentration of ~ntrainer, temperature,
pressure and water content. Analyses were performed using
high perf ormance liquid chromatography on the column Biora
HPX - 8 7H .
* Trade Mark
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TAB~
~llone
~t P Tenp E~rain~r Gluccnic ~iel~l ~) Ia~ic (Y~eld 9~) (Yiel~ ~) Glua~nic
# (E~i) (C) Sol~ (~) Xtd. SR LP~ Xtd S~ L~ xed. 5~ LR 100
5 Variation of methan~l a~t
48 30~ lOQ M~ 20.~ 67.1 2.1 15.2 93.7 0.0 0.0 ga.4 0.0 Q.0 a2.7
S~ 30~0 lOûMeCH 13.427.8 20.6 3.5 ~8.3 0.0 1.8 ~0.3 0.0 0.0 75.9
3000 100ME~ 8.4 2.6 70.7 4.5 ~ 6.1 60.5 ~3.7 4.0 9.0 24.9
. 56 3~0û100 Me~5.7 0.2 3.3 88.4 4.5 2.1 100.1 76.6 1.7 25.1 ~.3
2500 100~aH 20.354.5 35.7 5.6 100.3 0.0 0.9 102.5 0.0 0.0 57.7
61 2000 100~l 20.333.4 51.0 ~.0 1~9.4 0.0 3.4 g~.l 0.0 3.6 ~5.1
Variation of t~rature ar~l al~ol tyEe
48 3000 100 ~ 20.667.1 2.115.2 93.7 0.0 0.0 9~.~ 0.0 0.0 a~.7
53 3000 100E~ 19.3~5.5 51.4 0.5 85.5 0.0 0.6 94.7 0~0 0.0 ~8.1
58 30~70 ~3CH 19.7Sg.6 ~8.7 1.0 10~.9 0.0 0.7 96.1 0.0 0.0 80.3
62 3000 120~H 18.52~.6 25.7 0.5 100.5 0.0 0.5 96.7 0.~ 0.0 73.8
67 3000 100Me~ 20.6 0.0 }~2.7 0.4 0.8 ~0.9 4.4 2~q.7 ~2.1 17.4 -3.1
69 3000 100~# 20.661.1 7.1 17.2 g8.7 0.00.5 97.0 0.0 0.0 75.6
0 3000 100~CE*17.673.2 0.9 10.2 95.3 0.0~.3 g4.8 0.0 0.1 89.0
2 0 * E~ctr~ti~n f~:m solid æ~ a sysl~
X~ cted fractisn
25 g~R hLq~id ~ .
~ratial of glu0nic acid best ~a~ 1~ di~f~ 5R-LR) sir(x upc~ cooling
part oP the a~:id E~cipitated frcm the ~th3nolic solut~an
.
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From the results of Table III, it is clear that one can
extract lignill like compounds at very low entrainer (e.g.
methanoll ethanol) concentration in l:he 2,000 - 4,000 psi
range at the inves~iqa~ed ~emperature range. In order to
extract the carhoxylic acids, it iS impera~ive to increase
the concentration o~ entrainer (me~hanol or ethanol). It
should also bQ noted that the entrainer from these
particular experlments has to have an active hydroxy group
or other polar group to allow extraction of polyhydroxylated
10 carboxylic acids. If the chief interest is in
acetovanillone production, methanol, ethanol, acetone,
tetrahydrofuxan and the like can be used as entrainers. If
the compounds of interest are the acids as well, methanol
and ethanol are the preferred entrainers~
~XAMPL~S X~ XXIV
Other examples of ~ubstances that can be extracted with
supercritical carbon dioxide with methanol entrainer were
also tested. In one example, 0.27 g of Ascorbic acid was
disso}ved in 10 ml of water. The Ascorbic acid was
20 completely extracted at 95 C and at 3000 psi carbon dioxide
containing 17~ methanol with roughly 30 g of methanol or
0.5 h cQntinuous extrac~ion. Another example utilized the
same procedure as just described~ However, L-Alanine (an
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o~
amino acid) was su~stituted or the ascorbic acid, and
complete extxaction also occurred in this example.
These examples XXIII and XXIV clearly illustrated that
the use o methanol and water wi~h supercritical carbon
dioxide allows the extraction of polar compounds having
active -COOH, -OH and -NH2 groups.
As can be seen from the above, a novel process for
extracting or separat~ng low molecular weight components of
complex organic mixtures is provided. The process is simple
and econo~ic since it is a modification of supercritical
carbon dioxide separation, carbon dioxide being a very
inexpensive and readily available extractant material. As
can be seen, the present invention has particular
applicability to selec~i~ely extract reusable components
~ 15 from black liquor waste streams in the kraft pulping process
: as well as other biomass processing systems having waste
streams. It can also be applicable to the extraction of
hlgh value complex compounds from various processin~ ~treams
(biological or chemical processes). By merely modifying the
type and concentration of entrainer associated with the
supercritical carbon dioxide, one can select the material
being extracted from the complex organic mixture. Thus, the
process is very adaptable to numerous industrial systems, is
slmple and economic, and is easLly adapted and modified in
accordance with the desired, preseIected low molecular
2-
,
~ 3 ^~
weight extracted material.
While the foregoing description and illustration of the
present invention has ~een particularly shown in detail with
reference to preferred embodiments and modifica~ions
thereof, it should be understood by those skilled in the art
that the foregoing and other modifications are exemplary
only, and that equivalent changes in composition and detail
may be employed ~herein withou~ departing from the spirit
and scope of the invention as claimed ex~ept as precluded by
the prior art.
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