Note: Descriptions are shown in the official language in which they were submitted.
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COMPOSITION AND PROCESS FOR REDUCING CONTAMINANTS IN
GLYCERIDE OILS
FIELD OF THE INVENTION
The present invention pertains to a composition
and method for treating edible glyceride oils to remove
contaminants, chiefly free-fatty acids (FFA). The
composition and process may be applied either to
rejuvenation of used oils or refining of crude edible
glyceride oils.
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WO 94121765 ! PCT/US94102848
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BACKGROUND OF THE INVENTION
Edible glyceride oils, at various stages of
their production and use, contain variable amounts of
non-glyceride impurities. In refining~crude edible oils,
these impurities must be removed through the refining
process. In used glyceride oils, these impurities build
up as the oil is used, and if removed will increase the
useable life of the oil. In the refining process, these
impurities influence both the way the oil responds in the
various processing steps employed to produce a finished
product, and the yield of finished oil. In the reuse of
used oil, an increase in impurities can degrade the oil,
which can adversely affect its taste and shelf-life and
may increase its ability to be absorbed by foods.
Accordingly, it is desirable to remove these impurities
.at whatever stage of oil production and use they occur,
whenever gossible.
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Table 1
Unsapon-
Phosphate FFA Color ifiable Refin.
Crude Oil % % red Matter (%) Loss %
Soybean 1.1-3.2 1.0 5.0 1.5 5
Cottonseed 0.7-0.9 1.9 7.6 0.9-2.0 9
Peanut 0.3-0.4 2.0 5.0 0.2-0.8 5
Rapeseed 0.1 5.1 0.8-1.5
Corn 1.0-2.0 1.6 1.3-2.0 9
Olive .004-.014 1.8 0.6-1.3
Palm 0.05-0.10 5.0 17.0 0.2-1.0
Table 1 shows some of the impurities contained
in crude glyceride oils, which can be removed by the
refining process. In the refining process, the oils are
treated with caustic soda in the primary steps. The
caustic soda forms a flocculant precipitate of soaps
which settle out as "foots." The addition of an alkali
solution to crude or crude degummed oil results in
chemical reactions and physical changes. The alkali
combines with free-fatty acids in the oil to form soaps.
The phosphatides and gums absorb alkali and are
coagulated through hydration or degradation. Much of the
coloring matter is degraded and absorbed by the gums, or
made water soluble by the alkali. The insoluble matter
is entrained with the other coagulated material. The
soap-oil mixture is then heated to about 160-180°F (75-
82°C) and fed through a centrifuge for separation into
WO 94/21765 ' PCT/US94/02848
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light and heavy density phases. The light phase
comprises chiefly refined oils including traces of
moisture and soap. The heavy phase is.primarily soap,
insoluble matter, free caustic, phosphatides, and 5-9% of
neutral oil.
The refined oil (light phase) is discharged
from the centrifuge, heated to 190°F (88°C) and mixed
with soft water that has been heated to 200°F (93°C).
The water-oil mixture passes through a high-speed shear
mixer to obtain intimate contact between the oil and
water phases for maximum soap transfer from the oil to
the water. The mixture next passes through a second
centrifuge where the phases are separated. The water-
washed oil is discharged as the light phase, and the
soapy water as the heavy phase. The water-washing
process removes about 90% of the soap content of the
refined oil. The remainder of the soap is removed by a
subsequent bleaching process.
Caustic refining will remove phosphatides,
free-fatty acids (FFA), and some pigments. However, the
oil still contains color bodies, odors, metals, high
levels of soaps, and various impurities which need to be
removed before the finished oil will be of acceptable
color and taste to the consumer. A bleaching process
where clay and/or silica hydrogel is added to the oil,
WO 94/21765 ~ ~ PCT/US94I02848
and subsequently removed by filtration, may be used to
further reduce the remaining impurities.
In conjunction with the refining process, many
different adsorbents have been used, including: silica
hydrogel (U. S. Patent 4,629,588); silica hydrogel treated
with an organic acid (U. S. Patent 4,734,226); high
surface area amorphous silica treated with a strong acid
(U. S. Patent 4,781,864); partially dried silica gel (U. S.
Patent 4,880,574); bleaching absorbent and phosphoric
ac~.d (U. S. Patent 3,895,042); silicon dioxide, aluminum
oxide or mixtures thereof (U. S. Patent 3,955,004);
activated carbon impregnated with Mg0 (U. S. Patent
4.125;482 and U.S. Patent 4,150,045); bleaching clay and
an alkaline earth metal, lanthanide, or transition metal
exchange zeolite Y (U.S. Patent 4,443,379); silica gel
and silicic acid (U. S. Patent 4,874,629); metal oxide
silica absorbent (U. S. Patent 4,956,126); sodium silicate
solution combined with phosphoric acid (USSR patents
992;564-A, 1,386,642-A, 1,148,861-A, and 806,750-B).
Similar methods and adsorbents have been used for
removing contaminants from used cooking oils as well.
Although many compositions and methods have
been tried, the removal of FFA continues to be a problem.
For instance, silica hydrogel and similar compositions,
while addressing the removal of soap and color bodies,
have not' been shown to reduce FFA, as shown in Table 2.
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Table 2
Rapeseed Oil %FFA Color-Lovibond Soap-Metals
(ppm)
Red Yellow P Ca Ma Fe
Untreated) 1.2 3.5 70+ 194 132 34 1.1
2.0% ABE2 1.1 0.3 0.8 1.1 0.7 0.5 0.14
0.24% SH3/1.3% ABE 1.13 0.2 1.1 1.2 0.9 0.4 0.10
0.35% SH3/1.0% AHE 1.12 0.2 1.2 2.0 1.3 1.6 0.09
1 Crude degummed rapeseed oil
2 Activated Bleaching Earth
3 Silica Hydrogel
Accordingly, it would be desirable to reduce
the levels of FFA in glyceride oils, as well as reducing
color bodies, soaps, and trace metals (Ca, Mg, P, Cu, and
Fe ) .
SUN~1ARY OF THE INVENTION
The present invention provides a composition
and method for treating edible glyceride oils to remove
contaminants therefrom. The composition can be added
directly to crude oil, degummed oil, or used oil to
reduce FFA, color bodies, trace metals, and other
impurities. The composition comprises solid hydrous
alkali metal silicates, particularly sodium metasilicate
pentahydrate and hydrous sodium polysilicate. This
material is added to oil containing contaminants, in an
WO 94121765
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amount approximately equal to the amount of FFA present
in the oil after a small amount of water is added to the
oil. The oil may then be heated and agitated. The oil
is then filtered or centrifuged to remove the solid
hydrous sodium silicate, and vacuum dried, if
appropriate, to remove residual water.
DETAILED DESCRIPTION OF THE INVENTION
The type and levels of contaminants present in
glyceride oils depend on a number of factors, including
whether the oil is crude, whether it has been degummed,
and if used,=what foods were fried in the oil. Some
crude oils, like soybean for example, can have only about
0.7% FFA, while other oils like palm oil, have around
5.0% FFA. Accordingly, in removing FFA, the amount of
treating agent (solid hydrous sodium silicate) used
should depend upon the amount of contaminants in the oil.
It is preferred to use a 1:1 ratio of solid hydrous
sodium silicate to the FFA content of the oil on a weight
basis. Thus for 100 gms, of palm oil with 5.0% FFA, 5
gms, of solid hydrous sodium silicate would be used as a
treating agent.
The oil and solid hydrous sodium silicate
should react at elevated temperature. The oil may be
heated before (or after) the addition of the solid
hydrous'sodium silicate. The temperature to which the
WO 94121765 PCTIUS94102848
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oil should be heated will depend upon the processing that
the oil has previously received. Crude oils tend to
discolor when heated to temperatures over 220°F because
of color reactions and phospholipids. Once color bodies
are removed, higher temperatures may be used without
adversely affecting the oil. For instance, refined oil
must have the ability to be heated to 350° or higher in
order to withstand the temperatures needed to fry foods.
The temperature to which the oil is heated also
depends on what treating agent is used. Sodium
metasilicate pentahydrate has a melting point around
162°F (although experiments indicate it is stable in oil
at temperatures as high as 220°F). Therefore oils
treated with sodium metasilicate pentahydrate should be
heated to a lower temperature than oils treated with
hydrous sodium polysilicate, which has a much higher
melting point.
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Table 3
Temp %FFA % Soap
Treatment Agent % nt F Untr. Reduc. (p~,nm>
Age Treated
Polysilicate l 150 1.07 0.75 29.9 182
Polys/A1* 1 150 i.p5 0.77 26.7 202
Polysilicate 1 200 1.0? 0.77 28.1 184
Polys/A1* 1 200 1.11 0.79 29 162
Polysilicate 1 250 1.05 0.64 40 161
Polysilicate 1 270 1.11 0.46 59 116
Polysilicate 1 295 1.11 0.24 79 76
Na Meta. Penta 1 200 1.05 0.14 87 21
*70% hydrous sodium polysilicate / 30% alumina
Table 3 shows the effect of varying the
temperature of the oil on FFA removal when using hydrous
sodium polysilicate and sodium metasilicate pentahydrate.
As may be seen from the table, hydrous sodium
polysilicate is not as effective at removing FFA at law
temperatures as sodium metasilicate pentahydrate.
However, hydrous sodium polysilicate is useful and
effeetive for removing FFA at temperatures well above the
melting point of sodium metasilicate pentahydrate.
Therefore, sodium metasilicate pentahydrate is
recommended for refining where the oil begins cold and
must be heated, since sodium metasilicate pentahydrate
allows processing at lower temperature, thereby effecting
WO 94!21765 ' PCTlUS94/02848
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a cost savings in heating the ,oil. Hydrous sodium
polysilicate is useful in removing contaminants from used
oils, since they are usually at an elevated temperature
at which sodium metasilicate pentahydrate would melt.
The hydrous sodium polysilicate does not require cooling
the used oil and possibly reheating the oil for use after
cleaning.
Sodium silicates in general are combinations of
sodium oxide (Na20) and silicon dioxide (Si02). They may
or may not have water chemically bound within them.
Sodium polysilicate, for instance, has the formula
(Na20)x(Si02)y zH20 where the weight ratio y:x is greater
than 2.0 but less than 2.40. The material is generally
about 17.5% water on a weight basis when it is hydrous.
Specifically tested was a sodium polysilicate sold under
the name BRITESILm C20 (HRITESIL is a registered
tradeanark and HRITESIL products are available through the
PQ Corporation, P.O. Box 840, Valley Forge, Pennsylvania
19482). BRITESILm C20 has a Si02:Na20 ratio of 2.00.
BRITESILm C20 sodium polysilicate is amorphous, has a
bulk density of 50 lb/ft3 (.80 g/cm3), and is 17.5% H20
by weight.
The sodium metasilicate evaluated for
performance in removal of contaminants from edible
glyceride oils had the general formula
(Si02)y(Na20)x~zH20 where the y:x ratio was less than or
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equal to 1, and z equaled 5. Preferably ,the ratio of
x:y is between 1 and 2.4, and z is selected to produce a
water content of between 17.5% and 42% by weight. This
particular sodium metasilicate tested was METSO
PENTABEAD~ 20 available from the PQ Corporation (METSO
PENTABEAD 20). The molar ratio of Na20:Si0z was 1:1,
making the composition 29.3% Na20, 28.4% Si02, and 41.6%
H20. METSO PENTABEAD 20 has an approximate bulk density
of 49 lb/ft3 (0.78 g/cm3) .
The traditional refining process for edible
glyceride oils generally begins with a preheating step
to heat the oil to treatment temperature. Once hot, the
oil is treated with H3P04 and centrifuged. This treatment
turns non-hydratable (unreactive with alkali)
phospholipids to hydratable, so they can be removed by
the refining process. This treatment is referred to as
degumming. As previously described, once the oil has
been degummed, diluted caustic (NaOH) is added to
neutralize or remove FFA from the oil. The FFA react
with the sodium hydroxide to form soaps. The sodium
hydroxide is a solution in water, and soaps are
contained in the aqueous phase. One problem with this,
however, is that it requires several steps to remove the
residual alkaline materials. Once the caustic is added,
the oil is heated to allow the caustic to react. The oil
and water mixture is then centrifuged and the oil is
separated from the water and soap phase. The oil is then
washed with water again to remove residual caustic and
soaps in the oil phase. After washing with water, the
WO 94/21765 PCTIUS94/02848
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oil must once again be centrifuged and separated. Of
course, since soap is an emulsifier, the amount of oil
lost in this traditional method can be high. Once the
oil is separated, it is vacuum dried to remove any
residual water. The oil may then be bleached to help
neutralize or remove color bodies.
By using the hydrous solid alkali metal
silicate of the present invention, the caustic step in
the refining process may be eliminated. After the
degumtning with phosphoric acid, water is added to the oil
in an amount based upon the FFA level. Generally water
should be added in an amount of between 1.7 and 2.1 times
the weight of FFA present in the oil. A ratio of
water:FFA of 1.9 is preferred. If too much water is
used, the soaps which form will be thin, and will
therefore absorb more oil, leading to higher oil losses.
Conversely, if too little water is added, the soaps
formed will be too thick, making separation difficult.
Solid alkaline hydrous sodium silicate is then
added to the oil. To enhance the removal of FFA, the oil
may be heated and agitated. The oil may then be
centrifuged or filtered, depending upon the amount of
sodium silicate added to the oil. When greater amounts
of sodium silicate are added, filtering becomes
increasingly slow. Therefore if large amounts of sodium
silicate are to be added, centrifugation is the preferred
z~360I~
WO 94121765 - PCT/US94102848
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method of separation. The oil may then be washed with
water a second time, separated, and vacuum dried to
remove residual water.
Some oils like olive and almond oils have a low
phosphorus content. In those oils, the step of adding
phosphoric acid in order to remove phospholipids from the
oil can be eliminated since the sodium silicates will
remove some phospholipids. However, the remainder of the
refining process is the same, and this process is
improved by using solid alkaline hydrous sodium silicate
instead of a solution of caustic in that the amount of
water added to the oil is reduced.
In rejuvenating used cooking oils, a treating
agent is generally added directly to the used cooking oil
in the fryer or a separate treatment vessel. The oil is
then filtered to remove the treating agent and returned
to the fryer to be used. Generally this operation is
perfornied whale the oil is hot. The hydrous alkali metal
silicate described and claimed herein is useful as such a
treatment agent for used cooking oils, either alone or in
combination with other rejuvenating compounds.
As a used cooking oil rejuvenator, hydrous
sodium polysilicate is generally more useful than sodium
metasilicate pentahydrate. As previously explained, the
sodium metasilicate pentahydrate used in the tests
WO 94/21765 PCT/US94/02848
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~,1
conducted for this invention has a melting point of about
162°F (72.2°C), although this sodium metasilicate did not
melt in oil until the temperature rose to about 240°F.
Nevertheless, oil in fryers is generally at a temperature
of around 3~0°F. This temperature is too high for sodium
metasilicate pentahydrate to be useful, since is would
melt upon contact with the oil. Therefore, hydrous
sodium polysilicate with a higher melting point is more
useful for used cooking oil rejuvenation. The sodium
metasilicate pentahydrate, while effective in removing
contaminants, would require the cooling of the oil prior
to treatment. This is generally undesirable in that it
involves an additional processing step.
EXP~tIMENTAL RESULTS
Both METSO PENTABEAD 20 (sodium metasilicate
pentahydrate) and HRITESIL C20 (hydrated sodium
polysilicate) were tested with various batches of crude
edible glyceride oils to determine the conditions under
which the oil should be processed to most efficiently
remove FFA from the oil while minimizing undesirable
soaps. The results of this test are shown in Table 4.
WO 94121765 ~ PCT/US94/02848
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WO 94121765 , ~ ~ ~ b 0 ~' PC'Y'/US94/02848
- 17 -
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WO 94121 ~~ ~~ PCTIUS94I02848
L
- 1a -
The oils with which the compounds were tested
can be seen at the top of the table labeled Crude 1,
Crude 2 , Crude 3 , Crude 4 , Crude 5 , Crude 6 , Crude O1 ive ,
and Crude Walnut. These represent six batches of crude
soybean oils, and one sample each of crude olive oil and
crude walnut oil. Only soybean sample 5 was degummed
(treated to remove phosphates) prior to treatment with
the sodium silicates.
As may be seen from Table 4, the METSO
P~NTABEAD 20 (sodium metasilicate pentahydrate) performed
better with higher contact times, higher temperatures,
and larger doses. This was expected, as each factor
allows greater contact between oil and treatment agent.
The exception to this general observation was sample 9
where METSO PENTABEAD 20 appeared to perform slightly
worse with an increase in temperature from 200 to 220°F.
Only one sample was tried at this higher temperature.
The METSO PENTABEAD 20 even performed well where the
initial FFA content was in excess of S% (see samples ?S,
??, 8?, and 88).
Sodium metasilicate pentahydrate of differing
particle sizes was also tested and found to perform quite
well. METSO (Fine), METSO (Medium), METSO (Granular),
and METSO (Oversized) are all sodium metasilicate
pentahydrate in fine, medium, granular, and oversize
particle sizes. As may be seen from samples 50-?4 in
WO 94/21765 PCT/US94102848
19 -
table 4, these sizes of sodium metasilicate pentahydrate
were effective in removing FFA from the oils.
Table 4 also shows that HRITESIL C20 was
effective in removing FFA from the oils. This may be
seen from samples 47-53, 76, and 78. It does not appear
from these experiments that filtering or centrifuging the
oil made any difference in the performance of the
treatment agents. In real life, the time required to
filter large amounts of oil may increase the contact time
between the oil and treatment agent, thereby increasing
the performance of the treatment agent.
An experiment was conducted to show the effect
of solid hydrous sodium metasilicate and sodium
polysilicate as compared with other treatment agents, in
reducing FFA from edible glyceride oils. In this
experiment, a single edible oil was used, with a starting
FFA content of 1.65%. Several compounds were tested
according to the method of the present invention, and the
results show that the hydrated sodium polysilicate and
sodium metasilieate pentahydrate clearly outperformed the
other treatment agents tested. The results of this test
can be seen from Table 5.
WO 94/Z1765 ~ PCTIUS94/02848
~~,~:~~~~~ 3
- 20 -
Table 5
Temp. Water oFFA
Treatine~ Agent F Content Reduction
Hydrous sodium
silicate 300 Hydrous 94.4
Hydrous sodium
silicare Hydrous 76
Hydrous sodium
metasilicate Hydrous 96
Anhydrous sodium
orthosilicate 300 Anhydrous 9.3
Anhydrous sodium
metasilicate 300 Anhydrous 6.3
Anhydrous sodium
silicate 300 Anhydrous 5.9
Sodium alumino- .
silicate (Zeol.) 300 Low 5.3
Calcium silicate 300 Low 23.3
Alumina-mated
silica gel 300 Anhydrous .84
Alumina-coated
silica gel 300 Hydrous 4.2
Alkaline-set
silica hydrogel 300 Hydrous .33
'.25 70% silica hydrogel/
30% alumina 300 Hydrous 5.1
Both sodium metasilicate pentahydrate and
hydrous sodium polysilicate were tested in olive oil.
Olive oil is more viscous than soybean oil, and therefore
a ~ Sa .
.\': '
..uae,.2. .u... . .c._..~_.ri,awuxtsY7:.lrct.KRIV'onC6't':~~..V'~a:~ .t~~e _
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WO 94121765 ~ PCT/US94/02848
- 2Z -
agitation should be an important factor in FFA reduction.
The results of this testing are shown in Table 6.
TABLE 6
Italian Olive Oil
Treating Amount Temp. is FFA
AQerit it Aaent Oil Dea. F Unt. Treated Reduction Soap
(G)
METSO PB 20 1.5 1000 +A 200 0.48 0.26 46 ~r 15
ME~SO IaB 20 1.5 1000 +A 220 0.48 0.06 88 it 11
METSO PB 20 1.5 1000 +A 220 0.48 0.06 88 is 10
METSO PB 20 1.5 1000 220 0.48 0.26 46 ~ 49
I~'sTSO PB 20 6 1000 220 4 0.12 9? 3r <1
IS BRITF$II. 1.5 500 150 0.62 0.32 48 it 4?
BRIT/All 1.5 500 150 0.62 0.32 48 lr 52
BRITESIh 6 1000 220 4t 0.22 94.5 ~ 6
BRITESIh 1.5 500 230 0.52 0.25 50 it 32
BRIT/A.11 1.5 500 230 0.52 0.24 54 iC 40
- 4~r FFA addad the
to olive
oil
in
the
fozm
of
oleic
acid.
+A - Theae samples
were given more
agitation than
the others.
l - 50/50 mix of BRITES IL C20 and alumina
In all cases, the oil was filtered after
treatment. The sodium metasilicate pentahydrate did not
perform well without
high agitation
where the FFA eontent
was low. Howeve r, sodium
metasilicate
pentahydrate
did
perform well whe re the FFA content was high, even without
high agitation. It is reasoned that this performance is
WO 94/Z1765 PCT/US94/02848
c~~j~~~~ _ 22 _
due to the larger filtration bed developed where more
treatment agent (four times the lower level) is used.
Trials were also conducted to deteztnine the
effect of treatment temperature'on the effectiveness of
sodium metasilicate pentahydrate and hydrous sodium
polysilicate in removing FFA from glyceride oil. The oil
used for the test was soybean oil, in an amount of 500 g.
In several cases, oleic acid was added to the soybean oil
to increase the FFA content, before treatment with the
treatment agent. The results of these tests are shown in
Table 7.
WO 94121?65 ~ ~ ~ ~ ~ ~ ~ PCTlUS94102848
- 23 -
TABLE 7
Temperature Effect on Sodium Metasilicate Pentahydrate
and Hydrous Sodium Polysilicate Oil Treatment
(500g Soybean Oil)
~C Temp. s FFA
T 'n A A R
BRITESIL C20 1 150 1.0? 0.75 29.9 182
BRITESIL C20 2 150 2.11 0.42 80.09 2631
~10 HRITESIL C20 3 150 3.14 0.16 94.9 692
BRIT/R14 1 150 1.05 0.77 26.7 202
BRIT/A14 2 150 2.09 0.24 88.5 4353
BRIT/A14 3 150 3.16 0.34 89.2 21563
BRITESII~ C20 1 200 1.07 0.77 28.1 184
BRITESIL C20 2 200 2.09 0.81 61.2 210
BRI'I'ESIL C20 3 200 3.14 0.79 75 290
HRIT/A14 1 200 l.ll 0.79 29 162
HRIT/A14 2 200 2.14 0.98 55 344
BRIT/1114 3 200 3.18 0.86 73 270
2 0 BRITESIL C20 1 250 1.05 0.64 40 161
HRI'1'$STL C20 1 270 l.ll 0.46 59 116
BRIZ'RSIL C20 1 295 1.11 0.24 79 76
BRITSSIL C20 2 295 2.09 0.1 96 0
BRIT~SIL~C20 3 295 3.12 0.04 98.7 0
BRIT & C4005 1 295 1.11 0.22 80,2 0
BRIT & C4005 2 295 2.09 0.08 96,17 0
BRIT & C4005 3 295 3.12 0.02 99.4 0
I~TSO PENTABEAD 1 200 1.05 0.14 8? 21
20
1~TS0 P$NTABSAD 3 220 4.43 0.58 87 <1
20
1~'SO PFNTABFAD 3 220 3.52 0.28 92 30
20
1~TS0 pENTABFAD 3 200 2.11 0.02 99 cl
20
BRITFSIL C20 4 285 4 0.02 99 <1
BRITESIL C20 3 200 2.11 1.37 35
iFiltration time was 15 minutes.
>
2Filtration time was 45 minutes.
>
3Filtration time was 2 hours.
>
4Simultaneous treatment with BRITESIL C20 and Alumina
SSequential treatment a mixture
with HRITESIL C20,
then
of 70~ Silica and 30~ Alumina
hydrogel
WO 94/21765 PCT/US94/OZ848
- 24 -
In these samples, the addition of alumina, or
silica gel and alumina, appeared to have little or no
effect on the FFA reduction achieved by the hydrous
sodium polysilicate. Generally, the hydrous sodium
polysilicate performed better at higher temperatures,
although at a treatment agent level of 3% the hydrous
sodium polyailicate was quite effective at removing FFA
even at temperatures as low as 150°F. The increase in
temperature from 200 to 220°F did not appear to result in
large changes in the performance of sodium metasilicate
pentahydrate, in this aeries of tests.
podium metasilicate pentahydrate and hydrous
sodium polysilicate were tested to gauge performance as
compared,to treatment with a solution of 10% sodium
hydroxide, traditionally used to treat oil to remove FFA.
The sodium hydroxide was added in an amount of .3% of the
weight of the oil to be treated. The results of these
tests are shown in Table 8.
WO 94121765 ~ ~ PCT/I~S94102$48
- 25 -
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WO 94121765 PCTIUS94/02848
~z~..~60~~ _
26 -
As may be seen from Table 8, both the sodium
metasilicate pentahydrate and hydrous sodium polysilicate
performed comparably to the sodium hydroxide in both
crude and degummed oil, whether or not the oil was
bleached. Thus the use of these:ltreatment agents does
not sacrifice the quality of the oil produced.
Furthermore, an advantage of these treatment agents is
that, compared to caustic refining, less soap remains in
the oil and less neutral oil is lost in the soap stock.
For example, a caustic treated oil was found to contain
319 ppm residual soap and yielded a soap stock that
weighed 5.0% of the untreated oil weight. The same oil
treated by sodium metasilicate pentahydrate gave 228 ppm
and 2.1%.
Palm oil refined with METSO PENTABEAD 20 was
also compared to oil refined in the traditional manner
described previously. The results of this comparison are
shown in Table 9. As may be seen, refining with METSO
PENTABEAD 2o is comparable to refining in the traditional
manner.
WO 94/21765 PCT/US94/0284$
~~36018
- 27 -
TAB,~E
METSO PENTABEAD 20 STUDY
PALM OIL
FFA % SOAP COLOR
TREATMENT DOSE (%) Reduc. jnnm) PCI 520nm.
Untreated 2.52 -- <1 59.37 2.215
Refined Oil unkn. 0.04 98.4 <1 27.44** 2.024**
METSO 1* 0.02 99.2 <1 45.47 2.304
PENTABEAD 20
* Dosage is 1:1 ratio of METSO PENTABEAD 20:FFA on a
weight basis.
** These color measurements reflect further removal of
color bodies in this completely refined oil through
bleaching and deodorization.
METSO PENTABEAD 20 sodium metasilicate
pentahydrate was also tested to determine the amount of
oil absorbed by the treatment agent. The results of this
test are shown in Table 10.
WO 94/21765 PCT/US94/02848
- 28 -
Table 10
Oil Absorption Of METSO PENTI-BEAD 20
Average
T~r_pe 0 Oil % Oil Absorbed
Olive Oil 30.36%
Soybean Oil 38.53%
Cottonseed Oil 34.69%
These tests were conducted with used oils. Oil
absorbed is a weight percentage based on the weight of
treatment agent used. Thus the sodium metasilicate
pentahydrate absorbed only 3~0 to 40% of its weight of
oil, indicating low losses of oil in this type of
treatment.
Tt is understood that various other
modifications will be apparent to and can readily be made
by those skilled in the art without departing from the
scope and spirit of this invention. Accordingly, it is
not intended that the scope of the claims appended hereto
be limited to the description set forth herein, but
rather that the claims can be construed as encompassing
all of the features of patentable novelty that reside in
the present inventian, including all features that would
be treated as equivalents thereof by those skilled in the
art to which this invention pertains.
