Process for the production of tocotrienol/tocopherol blend concentrates

Disclosed is an improved process for the preparation of tocotrienol/tocopherol blend concentrates from vegetable oil distillates which are enriched in tocotrienols. Tocotrienol/tocopherol blend concentrates are obtained containing 20-80% tocotrienols/tocopherols by weight, with an overall recovery of tocotrienols/tocopherols of 72% to 97%. The process is comprised first of an esterification reaction where the more volatile alcohols are converted to their less volatile fatty acid esters, followed by a series of distillation steps where components boiling higher and lower than the tocotrienols/tocopherols are separated from tocotrienols/tocopherols and other like boiling substances. Advantages of the process are that tocotrienol/tocopherol blend concentrates are produced efficiently and economically in a minimum number of steps without the use of solvents and with a relatively small capital investment.

FIELD OF THE INVENTION 
This invention belongs to the field of organic chemistry. In particular, 
this invention relates to a process for the manufacture of 
tocotrienol/tocopherol concentrates from the by-products of vegetable oil 
refining. 
BACKGROUND OF THE INVENTION 
Alpha, beta, gamma, and delta tocopherol (hereafter referred to as 
tocopherols) can be found in various ratios and concentrations in crude 
vegetable oils such as soy bean, sunflower, canola, rapeseed, cottonseed, 
safflower, corn, palm, palm kernel, and rice bran oil. Palm oil and rice 
bran oil in particular contain high levels of both tocopherols and 
tocotrienols, whereas other vegetable oils contain primarily tocopherols. 
Typical crude palm oils contain 600-700 mg/Kg tocopherols and tocotrienols 
(50% tocotrienols) and crude rice bran oil contains 800-900 mg/Kg 
tocopherols and tocotrienols (57% tocotrienols). (See, for example, Proc. 
Malays. Biochem. Soc. Conf. (1983). pp. 15-17 and Lipids Handbook, 2d Ed., 
(1994) Chapman & Hall, p. 129.) Tocopherols and tocotrienols are a 
valuable constituent of vegetable oil as they help prevent oxidation and 
spoilage. Tocotrienols are of special interest for their 
hypocholesterolemic effects, as they decrease the blood level of the low 
density lipoprotein fraction of cholesterol and the total serum 
cholesterol, while increasing the ratio of the high density lipoprotein 
fraction of cholesterol to the low density lipoprotein fraction. Such 
effects have been shown to be clinically significant in lowering the risk 
of heart disease. (T. Gordon, et al., "High Density Lipoproteins as a 
Protective Factor Against Coronary Heart Disease", The American Journal of 
Medicine, 62, pp. 707-714 (1977)). During the refining of vegetable oils a 
large fraction of the tocopherols are lost to various by-products and 
waste streams. These waste and by-products streams include, but are not 
limited to, deodorizer distillates, steam refining distillates, and 
acidulated soapstocks. The vegetable oil refining by-products typically 
contain from less than 1% to greater than 20% tocopherol by weight. Such 
by-products from the tocotrienol-enriched vegetable oils such as rice bran 
oil and palm oil generally contain about 0.1 to 5% by weight of 
tocotrienols. The oil refining by-products are a valuable source of raw 
material for the production of natural vitamin E and other tocopherol 
antioxidants. However, the by-product streams also contain 20 to 99% by 
weight free fatty acids, less than 1% to 20% by weight sterols, less than 
1% to 20% by weight sterol esters of fatty acid, less than 1% to 40% by 
weight mono, di, and triglycerides, less than 1% to 30% by weight 
hydrocarbons, and several percentage by weight of other compounds, in 
addition to tocopherols and tocotrienols. Thus, in order to obtain a 
tocopherol/tocotrienol concentrate stream useful for production of high 
purity vitamin E, it is necessary to remove these substances. 
Numerous methods have been proposed for the recovery of tocopherols from 
vegetable oil refining by-products. For example, U.S. Pat. No. 2,432,181 
teaches that tocopherols can be recovered from vegetable oils and fats by 
reacting the fatty acid glycerides with an aliphatic monohydric alcohol in 
the presence of an alkaline alcoholysis catalyst, followed by a flash 
distillation of residual alcohol glycerol, and fatty acid esters. 
U.S. Pat. No. 3,153,055 teaches a process for the isolation of sterols and 
tocopherols from deodorizer distillate by esterification of free fatty 
acids and glycerides into lower monohydric alcohol esters under strongly 
acidic conditions. The sterols and tocopherols are fractionally extracted 
from the esterification product with a combination of polar and nonpolar 
solvents. 
U.S. Pat. No. 3,335,154 teaches that deodorizer distillate can be 
saponified and acidulated to convert glycerides and sterol esters to free 
fatty acids and free alcohols (glycerol, sterols respectively). The free 
fatty acids are esterified with a monohydric lower alcohol and mineral 
acid catalyst. The sterols are precipitated/crystallized by the addition 
of water to the mixture, and the tocopherols are concentrated by removal 
of the fatty acid esters by molecular distillation. 
All of the above processes suffer from serious drawbacks. They require the 
addition of extraneous monohydric alcohols and result in the production of 
fatty acid esters which are not normally present in the vegetable oil 
by-product feed material. The excess monohydric alcohol must be removed in 
an additional processing step. In order to produce a highly concentrated 
tocopherol product the sterols must either be removed by crystallization 
or by other means. Saponification requires large amounts of caustic and 
acid for acidulation, thereby creating excessive salt wastes. 
U.S. Patent No. 4,454,329 teaches that a tocopherol concentrate can be 
obtained from deodorizer distillates by esterification of the free fatty 
acids with a dihydric or polyhydric alcohol, in the presence or absence of 
an acid catalyst. The esterification is preferably carried out in the 
presence of an aromatic solvent such as benzene, toluene, or xylene. The 
esterified mixture is then subjected to either a solvent extraction or a 
molecular distillation to produce the final tocopherol concentrate. 
Preferably, the solvent extraction is proceeded by a hydrogenation to 
convert the unsaturated triglycerides into saturated triglycerides, 
thereby decreasing the solubility of the triglycerides in the solvent 
phase of the extraction. Distillation of the esterified mixture 
concentrates tocopherols, sterols, hydrocarbons and other components with 
similar boiling points in the distillate. The triglycerides and other 
high-boiling components are left in the distillation residue. 
The above process is unsatisfactory for a number of reasons. Deodorizer 
distillates and the like typically contain a 1/1 to 3/1 ratio of sterols 
to tocopherols, depending on the vegetable oil source. The tocopherols and 
sterols have very similar boiling points and therefore cannot be separated 
by distillation alone. The esterification is not run in such a fashion to 
ensure that the sterols are converted into sterol esters (which have a 
much higher boiling point than tocopherol). The distillate containing the 
tocopherols and sterols produced by the above process must be further 
treated by other separation techniques in order to produce a tocopherol 
concentrate essentially free of sterols. 
In the solvent extraction version of the process, the solvent must be 
removed from the tocopherol extract, adding additional cost and 
complication to the process. The preferred embodiment of the solvent 
extraction, proceeded by the hydrogenation, adds still another step, with 
concomitant cost and complication. In addition, typical copper and nickel 
hydrogenation catalysts are known to be prooxidants, which promote the 
destruction of tocopherol, thereby lowering the yield of tocopherol from 
the process.

SUMMARY OF THE INVENTION 
One object of this invention is to provide an efficient, economical process 
for the isolation of tocopherol/tocotrienol blend concentrates. This 
invention is directed to the isolation of such blend concentrates from 
vegetable oil by-products from sources which have relatively high amounts 
of tocotrienols as well as tocopherols. Such sources include rice bran oil 
and palm oil. Typically such sources will have approximately 0.1 to 5 
weight percent of tocotrienols and 0.1 to 5 weight percent of tocopherols. 
Since the tocopherols and tocotrienols have very similar physical 
properties, they will be isolated in the method of the present invention 
as a blend. The raw material for the process can be deodorizer distillate, 
steam refining distillate, acidulated soapstock, or any other vegetable 
oil by-product from these tocotrienol rich vegetable oils. 
In this invention, the vegetable oil by-product is subjected to an 
esterification step, with or without an acid catalyst, in which the 
sterols react with the free fatty acid already present in the mixture to 
form high-boiling sterol esters. Any other alcoholic moieties, 
triterpenoid alcohols, methyl-sterols, and the like, are converted to 
high-boiling fatty acid esters and waxes. Moreover, any mono- and di- 
fatty acid glycerides are largely converted to triglycerides by reaction 
with the free fatty acids. The tocopherols/tocotrienols also react to a 
limited extent; the extent of reaction can be controlled by proper 
selection of reaction time and temperature. The esterified mixture is then 
subjected to a series of distillation steps in which components boiling 
higher and lower than the tocopherols/tocotrienols are separated from 
tocopherols/tocotrienols and other like-boiling substances. The 
distillation steps consist of one or more separate distillation operations 
to remove unreacted free fatty acids overhead, along with any low-boiling 
compounds, from a tocopherol/tocotrienol-rich bottoms product and one 
distillation operation to remove a tocopherol/tocotrienol-rich product 
overhead from sterol esters, fatty acid polyesters of glycerol, waxes, and 
other high-boiling substances. Either the distillation operations to 
remove the fatty acid and low-boilers, or the distillation operation to 
remove the high-boilers may be done first. The resulting product of the 
process is a tocotrienol/tocopherol concentrate comprised primarily of 
tocopherols, tocotrienols, and hydrocarbons with similar boiling points, 
which is essentially free of free fatty acids, sterols, sterol esters, 
fatty acid polyesters of glycerol, waxes, and other high-boiling 
compounds. 
As a further aspect of this invention, the catalyst for the esterification 
step is a monoalkyl tin compound, zinc salt of an organic acid, titanium 
(IV) alkoxides, zinc oxide, phosphoric acid or other mild mineral acids. 
DETAILED DESCRIPTION OF THE INVENTION 
The present invention provides a method for preparing a 
tocotrienol/tocopherol blend concentrate which comprises the steps: 
(a) heating a vegetable oil by-product comprised of tocopherols, 
tocotrienols, fatty acids, hydrocarbons, sterol esters of fatty acids, 
sterols, triterpenoid alcohols, methyl-sterols, and mono-, di-, and 
triglycerides, wherein said tocotrienols are present in a proportion of 
about 0.5:1 to 10:1, by weight, based on the concentration of tocopherols, 
optionally in the presence of an acid catalyst, said by-product optionally 
containing additional C.sub.10 -C.sub.22 fatty acids, to a temperature of 
about 70.degree. C. to 300.degree. C. and a pressure of about 50 torr to 
760 torr, while continuously removing water formed thereby, to provide a 
mixture comprised of sterol esters, high boiling fatty acid esters, waxes, 
and glycerides; and 
(b) followed by subjecting said mixture to a series of distillation 
operations comprising: 
(i) one or more separate distillation operations, wherein said 
distillation(s) is (are) conducted at a temperature of about 200.degree. 
C. to 320.degree. C. and a pressure of about 0.01 torr to 10 torr, in 
series wherein unreacted fatty acids and low-boiling components are 
removed as a vapor effluent and a liquid effluent comprised of tocopherols 
and tocotrienols is removed; and 
(ii) wherein said liquid effluent from step (b)(i) is subjected to one or 
more distillations in series, wherein said distillation(s) is (are) 
conducted at a temperature of about 170.degree. C. to 270.degree. C. and a 
pressure of about 0.005 torr to 2 torr, wherein a tocotrienol/tocopherol 
concentrate is removed as a vapor effluent and wherein a liquid effluent 
comprised of sterol esters, fatty acid esters, glycerides, waxes, and 
other high-boiling substances is removed. 
The description of a preferred aspect of the present invention is made in 
reference to the process diagrams of FIGS. 1 and 2. The tocotrienol-rich 
vegetable oil by-product is fed via line (1) to a stirred tank or batch 
reactor, unit (2), operating at a temperature of about 
70.degree.-300.degree. C., preferably in the range of 
150.degree.-230.degree. C., and at a pressure of about 50 torr to 760 
torr, preferably about 100-200 torr. The residence time in the reactor is 
preferably from about 1 to 24 hours, most preferably 90 minutes to two 
hours in the presence of an acid catalyst, and from two hours to ten hours 
when no catalyst is used. Preferred catalysts include monoalkyl tin 
compounds, zinc salt of an organic acid, titanium (IV) alkoxides, zinc 
oxide, phosphoric acid and other mild mineral acids. 
During the reaction step, the free fatty acid which is already present in 
the feed mixture reacts with the sterols to form high-boiling sterol 
esters and water. Any other alcoholic moieties, triterpenoid alcohols, 
methyl-sterols, and the like, also react with the free fatty acids to form 
high-boiling fatty acid esters, waxes, and water. Moreover, any mono- and 
di- fatty acid esters of glycerol are largely converted to triglycerides 
by esterification with the free fatty acids. The tocopherols and 
tocotrienols also react to a limited extent with the free fatty acid to 
form tocopherol and tocotrienol esters and water. The relative rates of 
the esterification reactions is 
glycerides&gt;sterols&gt;tocopherols/tocotrienols. Thus, the reaction of 
tocopherols/tocotrienols can be controlled by proper selection of reaction 
temperature and time. Tocopherol/tocotrienol recovery from the reaction 
step is typically 80% to 97%, more typically 85% to 92%. Conversion of 
sterols to fatty acid sterol esters is typically 75% to 100%, more 
typically 85% to 95%. In a preferred embodiment, C.sub.10 -C.sub.22 fatty 
acids are added to the starting material by-product, most preferably in an 
amount of up to about 40% by weight, based on the total weight of the 
by-product starting material. 
The reactor is provided with a means for removal of the water of 
esterification, line (3). The removal of the water of esterification 
drives the reaction equilibrium toward the formation of the fatty acid 
ester products. 
The esterification product (4) is then subjected to a series of 
distillation steps in which components boiling higher and lower than the 
tocopherols and tocotrienols are separated from tocotrienols/tocopherols 
and other like-boiling substrates. The distillation steps are one or more 
separate distillation operations to remove unreacted free fatty acids 
overhead along with any low-boiling compounds from a 
tocotrienol/tocopherol-rich bottoms product, and one distillation 
operation to remove a tocotrienol/tocopherol-rich product overhead away 
from sterol esters, fatty acid polyesters of glycerol, waxes, and other 
high-boiling compounds. Either the distillation operations to remove the 
fatty acid and low-boilers, or the distillation operation to remove the 
high-boilers may be done first. It should be understood that the reaction 
and distillation operations may be accomplished in batch, semi-batch, and 
continuous modes of operation. 
This process produces tocotrienol/tocopherol blend concentrates efficiently 
and economically in a minimum of steps. No extraneous substances are added 
to the raw material oil, except possibly an esterification catalyst and 
added C.sub.10 -C.sub.22 fatty acids. No solvents or excess esterification 
alcohols need to be removed from the reaction product. The achievable 
tocotrienol/tocopherol concentration in the final product is in the range 
of 20-80% tocotrienol/tocopherol by weight, depending on the amount of 
hydrocarbons in the starting material. More typically the product will 
have a tocotrienol/tocopherol concentration of 30-60% by weight of 
tocotrienol/tocopherol. The overall recovery of tocotrienol/tocopherol 
blend from the process is typically 72% to 97%, more typically 75% to 92%, 
most typically 80% to 85%. 
One embodiment of the method of the present invention is illustrated by 
FIG. 1. The product (4) from the esterification step is distilled in unit 
(5) under high vacuum to remove a substantial fraction, typically 50-90%, 
more typically 60-80%, of the unreacted fatty acid along with a 
substantial fraction the low-boilers, stream (6), to leave a 
tocotrienol/tocopherol-rich bottoms product (7). The distillation 
operation is conducted at temperatures and pressures such that the 
tocotrienol/tocopherol are largely left in the bottoms product. The 
temperature and pressure of distillation operation (5) is in the range of 
170.degree. C. to 270.degree. C., 0.05 to 10 torr. The preferred range is 
200.degree. C. to 240.degree. C., 0.5 torr to 4 torr. The distillation 
apparatus (5) (as are all of the distillation equipment used herein) is 
preferably a high-vacuum design including a short path evaporator, a 
wiped-film evaporator, a centrifugal molecular still, or a falling film 
evaporator capable of low pressure operation. 
The bottoms product (7) of the first distillation operation (5) is 
distilled a second time in distillation operation (8) under high vacuum to 
remove any remaining unreacted fatty acids and other low-boiling 
compounds. The temperature of distillation (8) must be higher or the 
pressure lower than distillation (5) in order to ensure essentially 
complete removal of any remaining fatty acids. The temperature and 
pressure of distillation (8) is in the range of 230.degree. C. to 
300.degree. C., 0.01 to 5 torr. The preferred range is 240.degree. C. to 
280.degree. C., 0.1 torr to 2 torr. Under these conditions a portion, 
typically 5-30%, of the tocotrienols/tocopherols will distill overhead 
with the remaining fatty acids into stream (9), leaving an acid-free 
tocotrienol/tocopherol-rich bottoms product (10). The distillate (9) 
containing some tocotrienols/tocopherols and the remaining free fatty acid 
may be discarded or recycled to reactor (2) or the first distillation 
operation (5) in order to improve the overall yield of 
tocotrienols/tocopherols. Since distillation (5) and distillation (8) are 
conducted under different temperature and pressure conditions, they act in 
combination as a multi-equilibrium staged device, lowering 
tocotrienol/tocopherol losses and increasing fatty acid removal. The 
distillation apparatus (8) may be of any high-vacuum design including a 
short path evaporator, wiped-film evaporator, centrifugal molecular still, 
or falling film evaporator. 
The tocotrienol/tocopherol-rich bottoms product (10) of the second 
distillation (8) is then subjected to a third high-vacuum distillation 
(11). The tocotrienol/tocopherol and other similarly boiling compounds are 
collected as a final tocotrienol/tocopherol-rich distillate product (12). 
The triglycerides, sterol esters, other high-boiling fatty acid esters, 
and other high-boiling compounds are removed in the largely 
tocotrienol/tocopherol-free bottoms (13) of the distillation. 
Tocotrienol/tocopherol recovery to stream (12) is typically 95% to 100%, 
more typically 96% to 99.9%. The catalyst, if any were used, exits in the 
residue. The temperature and pressure of distillation operation (11) is in 
the range of 170.degree. C. to 270.degree. C., 0.005 to 2 torr. The 
preferred range is 200.degree. C. to 250.degree. C., 0.01 torr to 0.05 
torr. The distillation apparatus (11) may be of any high-vacuum design 
including a short path evaporator, wiped-film evaporator, centrifugal 
molecular still, or falling film evaporator. 
Thus, as a further aspect of the present invention, there is provided a 
method for preparing a tocotrienol/tocopherol blend concentrate which 
comprises the steps: 
(a) heating a vegetable oil by-product comprised of tocopherols, 
tocotrienols, fatty acids, sterols, sterol esters of fatty acids, and 
mono-, di-, and triglycerides, wherein said tocotrienols are present in a 
proportion of about 0.5:1 to 10:1 based on the concentration of 
tocopherols, 
said by-product optionally containing added C.sub.10 -C.sub.22 fatty acids, 
optionally in the presence of an acid catalyst, at a temperature of about 
70.degree. to 300.degree. C. and a pressure of about 50 torr to 760 torr, 
while continuously removing water formed thereby, to form a mixture 
comprised of sterol esters, high boiling fatty acid esters, waxes, and 
glycerides; 
(b) followed by subjecting said mixture to distillation at a temperature of 
about 170.degree. C. to 270.degree. C. and a pressure of about 0.05 to 10 
torr, while removing unreacted fatty acids and low-boiling components as a 
vapor effluent and a liquid effluent comprised of tocopherols and 
tocotrienols; 
(c) followed by subjecting the liquid effluent from step (b) to 
distillation at a temperature of about 230.degree. C. to 300.degree. C. 
and a pressure of about 0.01 to 5 torr, while removing remaining fatty 
acids and approximately 5 to 30 percent of total tocopherols as a vapor 
effluent and a liquid effluent which is a tocotrienol/tocopherol-enriched 
product; and 
(d) followed by subjecting the liquid effluent from step (c) to 
distillation at a temperature of about 170.degree. C. to 270.degree. C. 
and a pressure of about 0.005 to 2 torr, and collection and isolation of a 
tocotrienol/tocopherol blend concentrate as a vapor effluent. 
As noted above, preferred apparatus for the distillation steps include any 
high-vacuum design including a short path evaporator, wiped-film 
evaporator, centrifugal molecular still, or falling film evaporator. 
Accordingly, as a further aspect of the present invention, there is 
provided a method for preparing a tocotrienol/tocopherol blend concentrate 
which comprises the steps: 
(a) heating a vegetable oil by-product comprised of tocopherols, 
tocotrienols, fatty acids, hydrocarbons, sterol esters of fatty acids, 
sterols, triterpenoid alcohols, methyl-sterols, and mono-, di-, and 
triglycerides, wherein said tocotrienols are present in a proportion of 
about 0.5 to 10, by weight, based on the concentration of tocopherols, 
optionally in the presence of an acid catalyst, said by-product optionally 
containing additional C.sub.10 -C.sub.22 fatty acids, at a temperature of 
about 70.degree. C. to 300.degree. C. and a pressure of about 50 torr to 
760 torr, while continuously removing water formed thereby, to provide a 
mixture comprised of sterol esters, high boiling fatty acid esters, waxes, 
and glycerides; 
(b) followed by feeding said mixture to a first distillation zone 
comprising: 
a first distillation apparatus selected from the group consisting of a 
short path evaporator, a wiped film evaporator, a centrifugal molecular 
still, and a falling film evaporator, operated at a temperature of about 
170.degree. C. to 270.degree. C. and a pressure of about 0.05 to 10 torr, 
wherein a vapor effluent comprised of a substantial fraction of the 
unreacted free fatty acids, and low-boiling materials is removed, 
wherein a liquid effluent which is comprised of a 
tocotrienol/tocopherol-enriched mixture is removed; 
(c) followed by feeding the liquid effluent from step (b) to a second 
distillation zone comprising: 
a second distillation apparatus selected from the group consisting of a 
short path evaporator, a wiped film evaporator, a centrifugal molecular 
still, and a falling film evaporator, operated at a about 240.degree. C. 
to 280.degree. C. and a pressure of 0.01 to 2 torr, 
wherein a vapor effluent comprised of remaining fatty acids and 
approximately 5 to 30 percent of total tocotrienols/tocopherols is 
removed, wherein a liquid effluent comprised of a 
tocotrienol/tocopherol-enriched mixture is removed; and 
(d) followed by feeding the liquid effluent from step (c) to a third 
distillation zone comprising: 
a third distillation apparatus selected from the group consisting of a 
short path evaporator, a wiped film evaporator, a centrifugal molecular 
still, and a falling film evaporator, operated at a temperature of about 
170.degree. C. to 270.degree. C. and a pressure of 0.005 to 2 torr, 
wherein a vapor effluent which is a tocopherol concentrate is removed and 
isolated. 
It should be appreciated that the order of the fatty acid removal and 
high-boilers distillation may be reversed, i.e., steps (b) and (d) of the 
above aspects of the invention would be reversed. In this embodiment, the 
product of the esterification reactor (4) is fed first to distillation 
operation (11). The free fatty acids, low-boilers and 
tocotrienols/tocopherols are distilled overhead first from the sterol 
esters, fatty acid polyesters of glycerol, waxes, and other high-boiling 
compounds. The tocotrienol/tocopherol-rich distillate is then fed to 
distillation operation (5) to remove a substantial fraction of the fatty 
acids and low-boilers and then to distillation operation (8) to remove the 
remaining fatty acids and low-boilers. The final 
tocotrienol/tocopherol-rich concentrate is the bottoms product of 
distillation operation (8). The distillate of unit (8) may be recycled to 
the reactor (2), the first distillation (11), or the second distillation 
(5) in order to increase the overall tocotrienol/tocopherol recovery. 
A more highly preferred embodiment of present invention is illustrated by 
FIG. 2. The vegetable oil by-product (1) is esterified in a batch or 
continuous reactor (2), with or without catalyst. The water of 
esterification is removed continuously via line (3) during the reaction. 
The product of the esterification step (4) is distilled under high vacuum 
to remove essentially all of the unreacted fatty acid, typically 90% to 
99.9%, more typically 97% to 99.9%, along with a substantial fraction of 
other low-boilers via stream (8) to leave a tocotrienol/tocopherol-rich 
bottoms product (10). The temperature and pressure of the distillation is 
in the range of 220.degree. C. to 320.degree. C., 0.1 to 8 torr. The 
preferred range is 260.degree. C. to 290.degree. C., 0.5 torr to 4 torr. 
In the preferred embodiment of the invention, the distillation apparatus 
for the fatty acid removal step is a multistage, refluxed fractionating 
column. The column must contain at least one, preferably two to four, 
equilibrium stages of rectification (5), as well as an optional stripping 
section (6). The column must also have the capability of providing reflux 
via line (7) to the rectification section (5). The fractionating 
capability of the device greatly decreases the tocotrienol/tocopherol loss 
to the distillate to typically less than 5%, more typically 0.2% to 2.0%, 
and increases the removal of the free fatty acid from the bottoms product. 
The optional stripping section further increases the removal of the free 
fatty acids from the bottoms product. The extent of tocotrienol/tocopherol 
loss is highly dependent on the reflux ratio, defined as the ratio of the 
mass flow rate of stream (7) to the mass flow rate of stream (8). In the 
preferred embodiment of the invention the reflux ratio is in the range of 
0.3 to 5.0, more preferably from 0.5 to 2.0. The staging in the 
rectification and optional stripping sections may be provided by any 
vapor-liquid contacting device, including bubble cap trays, sieve trays, 
random packing, and structured packing. In the preferred embodiment of the 
invention, the equilibrium staging is provided by high efficiency, low 
pressure drop structured packing, in order to lower residence time and 
reduce the temperature required for distillation. The reboiler of the 
distillation apparatus may be of any high-vacuum, low residence design 
including a short path evaporator, wiped-film evaporator, centrifugal 
molecular still, or falling film evaporator. 
The tocotrienol/tocopherol-rich bottoms product (10) of the first 
distillation is then subjected to a second high-vacuum distillation (11). 
The tocotrienols/tocopherols and other similarly boiling compounds are 
collected as a tocotrienol/tocopherol-rich distillate product (12). The 
triglycerides, sterol esters, other high-boiling fatty acid esters, and 
other high-boiling compounds are removed in the largely 
tocotrienol/tocopherol-free bottoms, stream (13), of the distillation. 
Tocotrienol/tocopherol blend recovery to stream (12) is typically 95% to 
100%, more typically 96% to 99.9%. The catalyst, if any were used, exits 
in the residue. The temperature and pressure of the second distillation is 
in the range of 170.degree. C. to 300.degree. C., 0.005 to 2 torr. The 
preferred range is 200.degree. C. to 250.degree. C., 0.01 torr to 0.05 
torr. The distillation apparatus (11) may be of any high-vacuum design 
including a short path evaporator, wiped-film evaporator, centrifugal 
molecular still, or falling film evaporator. 
Thus, as a further aspect of the present invention, there is provided a 
method for preparing a tocotrienol/tocopherol blend concentrate which 
comprises the steps: 
(a) heating a vegetable oil by-product comprised of tocopherols, 
tocotrienols, fatty acids, hydrocarbons, sterol esters of fatty acids, 
sterols, triterpenoid alcohols, methyl-sterols, and mono-, di-, and 
triglycerides, wherein said tocotrienols are present in a proportion of 
about 0.5:1 to 10:1, by weight, based on the concentration of tocopherols, 
optionally in the presence of an acid catalyst, said by-product optionally 
containing additional C.sub.10 -C.sub.22 fatty acids, to a temperature of 
about 70.degree. C. to 300.degree. C. and a pressure of about 50 torr to 
760 torr, while continuously removing water formed thereby, to provide a 
mixture comprised of sterol esters, high boiling fatty acid esters, waxes, 
and glycerides; 
(b) followed by feeding the mixture from step (a) to a first distillation 
zone comprising: 
a first distillation apparatus comprised of a multistage, refluxed 
fractionating column and a reboiler, said column having a rectification 
section having at least one equilibrium stage of rectification and means 
for providing reflux to said rectification section, and optionally a 
stripping section, said apparatus operated at a temperature of about 
220.degree. C. to 320.degree. C., and a pressure of about 0.1 to 8 torr, 
wherein a vapor effluent which is comprised of free fatty acids and 
low-boiling materials is removed; and 
wherein a liquid effluent which is comprised of a 
tocotrienol/tocopherol-enriched mixture is removed; 
(c) followed by feeding the liquid effluent from step (b) to a second 
distillation zone comprising: 
one or more separate distillation apparatus in series selected from the 
group consisting of a short path evaporator, a wiped film evaporator, a 
centrifugal molecular still, and a falling film evaporator, operated at a 
temperature of about 200.degree. C. to 320.degree. C. and a pressure of 
about 0.01 torr to 10 torr, 
wherein a liquid effluent comprised of sterol esters, fatty acid esters, 
glycerides, waxes, and other high-boiling materials is removed; 
wherein a vapor effluent which is a tocotrienol/tocopherol blend 
concentrate is removed and isolated. 
It should also be understood that the order of the fatty acid removal and 
high-boilers distillation may be reversed in this embodiment. In this 
embodiment, the product of the esterification reactor (4) is fed first to 
distillation operation (11). The free fatty acids, low-boilers, 
tocotrienols, and tocopherols are distilled overhead first from the sterol 
esters, fatty acid polyesters of glycerol, waxes, and other high-boiling 
compounds. The tocotrienol/tocopherol-rich distillate is then fed to a 
multi-staged fractionating distillation operation to remove essentially 
all of the fatty acids and a substantial fraction of the low-boilers. The 
distillation operation consists of a refluxed rectifying section (5), a 
reboiler (9), and an optional stripping section (6). The final 
tocotrienol/tocopherol-rich concentrate is the bottoms product of the 
second multi-staged distillation operation. 
Accordingly, as a further aspect of the present invention, there is 
provided a method for preparing a tocotrienol/tocopherol blend concentrate 
which comprises the steps: 
(a) heating a vegetable oil by-product comprised of tocopherols, 
tocotrienols, fatty acids, hydrocarbons, sterol esters of fatty acids, 
sterols, triterpenoid alcohols, methyl-sterols, and mono-, di-, and 
triglycerides, wherein said tocotrienols are present in a proportion of 
about 0.5:1 to 10:1, by weight, based on the concentration of tocopherols, 
optionally in the presence of an acid catalyst, said by-product optionally 
containing additional C.sub.10 -C.sub.22 fatty acids, to a temperature of 
about 70.degree. C. to 300.degree. C. and a pressure of about 50 torr to 
760 torr, while continuously removing water formed thereby, to provide a 
mixture comprised of sterol esters, high boiling fatty acid esters, waxes, 
and glycerides; 
(b) followed by feeding the mixture from step (a) to a first distillation 
zone comprising: 
one or more separate distillation apparati in series selected from the 
group consisting of a short path evaporator, a wiped film evaporator, a 
centrifugal molecular still, and a falling film evaporator, said apparati 
operated at a temperature of about 200.degree. C. to 320.degree. C. and a 
pressure of about 0.01 torr to 10 torr, 
wherein a liquid effluent comprised of sterol esters, fatty acid esters, 
glycerides, waxes, and other high-boiling materials is removed; and 
wherein a vapor effluent comprised of tocotrienols, tocopherols, free fatty 
acids and low-boilers is removed; 
(c) followed by feeding the vapor effluent from step (b) to a second 
distillation zone comprising: 
a distillation apparatus comprised of a multistage, refluxed fractionating 
column and a reboiler, said column having a rectification section having 
at least one equilibrium stage of rectification and means for providing 
reflux to said rectification section, and optionally a stripping section, 
said apparatus operated at a temperature of about 220.degree. C. to 
320.degree. C., and a pressure of about 0.1 to 8 torr, 
wherein a vapor effluent which is comprised of free fatty acids, and 
low-boiling materials is removed; 
wherein a liquid effluent which is a tocotrienol/tocopherol blend 
concentrate is removed and isolated. 
EXPERIMENTAL SECTION 
Example 1 
A one liter 3-neck flask equipped with a mechanical stirrer, heating 
mantle, Dean-Stark trap, reflux condenser, nitrogen inlet, and thermowell 
was charged with 500 g of rice bran oil distillate comprised of tocols (2% 
tocotrienol and 1% tocopherol), sterols (1%), sterol esters (9%), free 
fatty acids (35%), hydrocarbons, and glycerides. The resulting mixture was 
stirred and heated for 7 hours at 200.degree. C. A nitrogen flow of 100 
mL/min was bubbled through the mixture during heating. The mixture was 
sampled and analyzed for tocols, sterols, sterol esters, fatty acids, and 
glycerides. The product mixture was distilled as described in Example 13 
of U.S. Ser. No. 08/334,901. The distillate was composed mainly of fatty 
acids and squalene. The residue from the distillation was fed to a wiped 
film distillation apparatus as described in Example 14 of U.S. Ser. No. 
08/334,901. The results of the distillations are listed in Table 1. 
Details of the utilization of other vegetable oil by-products can be found 
in our copending application, U.S. Ser. No. 08/334,901, incorporated 
herein by reference. 
TABLE 1 
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Two-Step Distillation of Esterified Rice Bran Oil Distillate 
Free 
Sterol 
Fatty 
Tocopherol 
Tocopherol 
Sterol 
Ester 
Acid 
Reference Mass 
Content 
Content 
Content 
Content 
Content 
No. Stream 
(g) (%) (%) (%) (%) (%) 
__________________________________________________________________________ 
A feed 464 1.0 2.0 0.2 22.9 
B distillate #1 
89 0.0 0.0 0.0 0.0 98.9 
residue #1 
374 0.7 0.8 0.2 25.5 
2.1 
C distillate #2 
55 6.8 11.3 0.7 1.0 3.6 
residue #2 
305 0.1 0.0 0.1 32.8 
5.6 
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