Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Method of improving oil compositions
This invention relates to a method of improving the low-temperature properties
of oils
derived from plant or animal materials.
Oils and fats derived from plant or animal materials are increasingly finding
application
as fuels and in particular, as partial or complete replacements for petroleum
derived middle
distillate fuels such as diesel. Commonly, such fuels are known as `biofuels'
or `biodiesel'.
Biofuels may be derived from many sources. Amongst the most common are the
alkyl, often
methyl, esters of fatty acids extracted from plants such as rapeseed,
sunflower etc. These types of
fuel are often referred to as FAME (fatty acid methyl esters).
There is an environmental drive to encourage the use of such fuels as they are
obtained
from a renewable source. There are also indications that biofuels produce less
pollution on
loll than the quiv-aIcnt petroleum-derived t'uei.
Fuel oils derived from plant or animal materials contain components, e.g.,
methyl n-
aikanoates, that at low temperature tend to precipitate as large, plate-like
crystals or spherulites of
wax in such a way as to form a gel structure which causes the fuel to lose its
ability to flow. The
lowest temperature at which the fuel will still flow is known as the pour
point.
As the temperature of the fuel falls and approaches the pour point,
difficulties arise in
transporting the fuel through lines and pumps. Further, the wax crystals tend
to plug fuel lines,
screens, and filters at temperatures above the pour point. These problems are
well- recognised in
the art, and various additives have been proposed, many of which are in
commercial use, for
depressing the pour point of fuel oils; both those derived from petroleum
sources and those
derived from plant or animal materials. Similarly, other additives have been
proposed and are in
commercial use for reducing the size and changing the shape of the wax
crystals that do form.
Smaller size crystals are desirable since they are less likely to clog a
filter. Certain additives
inhibit the tendency of the waxes formed to crystallize as platelets instead
causin them to adopt
an acicular habit. The resulting needles are more likely to pass through a
titter, or Norm a porous
CA 02687711 2009-12-08
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layer of crystals on the filter, than are platelets. The additives may also
have the effect of
retaining the wax crystals in suspension in the fuel, reducing settling and
thus also assisting in
prevention of blockages.
The low temperature properties of the oils derived from plant or animal
materials are
largely determined by the saturated fatty acid content of the oil, and in
particular by the
proportion of C16 - C22 saturated fatty acids which may be present. The methyl
and ethyl esters of
these acids may be particularly problematic. Transportation and handling of
such oils at or below
the temperature at which these species crystallise from a mixture of fatty
acid esters is difficult.
Oils which contain very little saturated fatty acid esters can sometimes
successfully be treated
with conventional additives to improve their low-temperature properties.
However, oils
containing even relatively low amounts of, in particular, esters derived from
palmitic and stearic
acids, have been found to be unresponsive to conventional additives.
Despite the pri)!`õ '11chtcd c. tilt're I,, a CICS1re to utilise Oils
del',v;.':1 tro111 p1a11',
or animal materials containing C16 - C22 saturated fatty acids. This is
because they are obtained
from comparatively inexpensive and plentiful sources. The present invention
provides a solution
to the low-temperature transportation and handling problems associated with
these oils.
In accordance with the present invention there is provided a method of
improving the low
temperature properties of an oil comprising fatty acid alkyl esters derived
from plant or animal
materials, wherein at least 5% by weight of the fatty acid alkyl esters are
derived from C16 - C22
saturated fatty acids, the method comprising reacting at least a portion of
the oil with at least one
compound having 3 or more nitrogen atoms, at least one of which nitrogen atoms
is present in the
form of a primary amine group; wherein the at least one compound having 3 or
more nitrogen
atoms comprises a polyalkylene polyamine or an imidazoline compound carrying
both a poly-
alkylene imine substituent and at least one primary amine group.
In the context of the present invention, an improvement in low temperature
properties
with regard to the oil may constitute r.1n improvement in any one or more of
the pour point, the
cloud point, the cold tiitel piu~gping point (,~:l l'l) or other operability
test. Suitable tests will be
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known to those skilled in the art. Preferably, an improvement in low
temperature properties will
constitute an improvement in pour point and/or an improvement in CFPP.
Without wishing to be bound by any theory, it is thought that the amidation of
a mixture
of the types of fatty acid esters which give rise to poor low temperature
properties provides an
`additive' which is effective to improve the low temperature properties of an
oil where these
esters are present in significant amounts. The `additive' is produced in situ
by reacting the
compound having 3 or more nitrogen atoms directly with the oil containing the
problematic
saturated fatty acid-derived esters. As is known in the art, the reaction of
e.g. a methyl ester with
an amine to form an amide is facile.
Preferably the portion of the oil which is reacted with the compound having 3
or more
nitrogen atoms is between 0.05 - 10% by weight of the oil, more preferably
0.05 - 2% by weight,
for example 0.05 - 1 % by weight.
The oil, once reacted with the compound having 3 or more nitrogen atoms, may
be used
on its own, e.g. as a pure bio-fuel, or be combined in any proportion with a
petroleum-derived oil.
In a preferred embodiment, at least one fatty acid is additionally employed.
Preferably, a
mixture of fatty acids is employed for example. a mixture of fatty acids
obtained from plant or
animal materials. The at least one fatty acid is co-reacted with the oil and
the at least one
compound having 3 or more nitrogen atoms, or is added to the oil. The at least
one fatty acid and
the at least one compound having 3 or more nitrogen atoms may be added to the
oil in any order.
By employing at least one fatty acid, the low-temperature properties of an oil
derived
from plant or animal materials comprising at least 5% by weight of fatty acid
alkyl esters derived
from C16 - C22 saturated fatty acids can be further improved.
It is expected that one (or more if present) of the primary amine groups of
the compound
having 3 or more nitrogen atoms will react with the fatty acid alkvl esters to
form an amide. As
mentioned above, this reaction is favourable and can be t acilitated h) gentle
heat. Other nitrogen
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atoms of the compound may be for example, secondary or tertiary amines. Amide
formation from
such amine groups is much less favourable and thus it is expected that they
will remain unreacted
in the presence of the fatty acid alkyl esters. It is presently thought that
the addition of a fatty acid
may promote the formation of a salt with one or more of the other nitrogen
atoms.
The various features of the invention will now be described in more detail.
Mixture of fatty acid alkyl esters.
At least 5% by weight of the mixture of fatty acid alkyl esters is derived
from C16 - C22
saturated fatty acids. Preferably, at least 10%, more preferably at least 20%,
even more preferably
at least 30% of the mixture of fatty acid alkyl esters is derived from C16 -
C22 saturated fatty acids.
Preferred are methyl or ethyl esters, especially methyl esters.
ii; ~nt the Bitty acid alkyl esters derived from uratcJ ratty
acids comprise methyl palmitate, methyl stearate or a mixture thereof.
Preferably, die amount of the mixture of fatty acid alkyl esters derived front
C1o - C22
saturated fatty acids will not exceed 60% by weight. The majority of the
remainder of the mixture
of fatty acid esters preferably comprises those derived from unsaturated fatty
acids.
Non-limiting examples of suitable materials include palm oil methyl ester
(PME), soy oil
methyl ester (SMIE) and rape-seed oil methyl ester (RME). Also suitable are
mixtures of materials
obtained from different sources for example, a mixture of PME and rape-seed
methyl ester
(RME) or other similar mixtures.
Compound having 3 or more nitrogen atoms
The compound to be reacted with the oil has at least 3 nitrogen atoms. At
least one of
these nitrogen acorns is in the form of "I primary amine.
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In one embodiment, the compound having 3 or more nitrogen atoms is (i) a
polyalkylene
polyamine.
Suitable are those species comprising amino nitrogens linked by alkylene
bridges, which
amino nitrogens may be primary, secondary and/or tertiary in nature, provided
that at least one
amino nitrogen is a primary amine group. The polyamines may be straight chain,
wherein all the
amino groups will be primary or secondary groups, or may contain cyclic or
branched regions or
both, in which case tertiary amino groups may also be present, again provided
that at least one
amino nitrogen is a primary amine group. The alkylene groups may be identical
or they may be
different within a single molecule. Ethylene or propylene groups are
preferred, with ethylene
being most preferred.
Non-limiting examples of suitable polyalkylene polyamines include di(ethylene)
triamine
(DETA), tri(ethylene)tetramine (TETA), tetra(ethylene)pentamine (TEPA),
penta(ethylene)
tic 'amine (PEIIA) and sniiiLlr holnolkws. Ii I- -1!!1!11'_-S ll; l or mor e
nitrogen
atoms are generally preferred over those with 4 or fewer nitrogen atoms.
Mixtures of polyalkylene polyamines are ako -unable. As is known in the art,
these
materials are readily available and comprise polyalkylene polyamines of
various sizes. They are
commonly referred to as PAM. They may be defined by the average number of
nitrogen atoms
per molecule of the component, which may preferably be in the range of 5 to
8.5, more
preferably 6.8 to 8, for example 6.8 to 7.5 nitrogens per molecule. Heavier
materials, so-called
HPAM, are also suitable such as amine mixtures comprising polyamines having on
average
seven and eight, and optionally nine, nitrogen atoms per molecule.
In another embodiment, the compound having 3 or more nitrogen atoms is:
(ii) an imidazoline compound carrying both a poly-alkylene imine substituent
and at least one
primary amine group. Such compounds may for example be made by reacting a
fatty acid or the
methyl ester of a fatty acid (e.g. stearic or palmitic) with a polyalkylene
polyamine such a TETA,
I EPA. PEI 1A, PAM and the like.
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Fatty acid
Preferred fatty acids are unsaturated fatty acids having between 16 and 20
carbon atoms.
Particularly preferred are CIA unsaturated acids such as oleic acid, linoleic
acid and linolenic acid.
These may be used as pure components, but it preferable to use mixtures of
fatty acids obtained
from plant or animal materials. Examples are fatty acid mixture obtained from
rapeseed oil, tall
oil, coriander oil, soyabean oil, cottonseed oil, sunflower oil, castor oil,
olive oil, peanut oil,
maize oil, almond oil, palm kernel oil, coconut oil, mustard seed oil,
jatropha oil, beef tallow and
fish oils. Further examples include oils derived from corn, jute, sesame, shea
nut, ground nut and
linseed oil and may be derived therefrom by methods known in the art. Oils
having a high
proportion of CIA unsaturated fatty acids, that is in excess of 50% by weight
of C18 unsaturated
fatty acids, preferably in excess of 70% or 85% by weight are suitable. Fatty
acids obtained from
tall oil and rapeseed oil are particularly suitable.
One or more co-additives may be used in the present invention. Suitable co-
additives are
those known in the art as effective to improve the low-temperature properties
of fuel oils as well
as additives to improve other properties of the oils such as lubricity
additives, antioxidants,
dispersants, detergents and similar.
In a preferred embodiment, an ethylene polymer may be employed as a co-
additive.
Examples of these are given below.
Ethylene Polymers
Each polymer may be a homopolymer or a copolymer of ethylene with another
unsaturated monomer.
Preferred co-monomers are unsaturated esters or ether monomers, with ester
monomers
heinL, more preferred. Preferred ethylene unsaturated ester copolymers have,
in addition to units
ucrl: cu Irt)III CUI~ ICIIC, IlillIs of UlC formula:
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-CR3R4-CHR5-
wherein R3 represents hydrogen or methyl, R4 represents COOR6, wherein R6
represents an alkyl
group having from 1-12, preferably 1-9 carbon atoms, which is straight chain,
or, if it contains 3
or more carbon atoms, branched, or R4 represents OOCR', wherein R7 represents
R6 or H, and R5
represents H or COOR6.
These may comprise a copolymer of ethylene with an ethylenically unsaturated
ester, or
derivatives thereof. An example is a copolymer of ethylene with an ester of a
saturated alcohol
and an unsaturated carboxylic acid, but preferably the ester is one of an
unsaturated alcohol with
a saturated carboxylic acid. An ethylene-vinyl ester copolymer is
advantageous; an ethylene-
vinyl acetate, ethylene-vinyl propionate, ethylene-vinyl hexanoate, ethylene-
vinyl 2-
ethylhexanoate, ethylene-vinyl octanoate or ethylene-vinyl versatate copolymer
is preferred.
Preferably, the copolymer cant<iui, t,ronl , iii d csicr, m~~rc prcl~r,ihly
front 10
to 35 wt% vinyl ester. A mixture of two copolymers, for example, as described
in US Patent No.
3,961,916, may be used. The Mn of the copolymer is advantageously 1,000 to
10,000. If desired,
the copolymer may contain units derived from additional comonomcrs. e.g. a
terpolymer,
tetrapolymer or a higher polymer, e.g. where the additional comonomer is
isobutylene or
diisobutylene or a further unsaturated ester.
Other suitable co-monomers include hydrocarbon monomers such as propylene, n-
and
iso- butylenes, 1-hexene, 1-octene, methyl-l-pentene vinyl-cyclohexane and the
various alpha-
olefins known in the art, such as 1-decene, 1-dodecene, 1-tetradecene, 1-
hexadecane and 1-
octadecene and mixtures thereof.
The invention will now be described by way of example only.
Example I
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Rape-seed oil methyl ester (RME) having a C16 - C22 saturate content of 6.2%
by weight
was reacted with tetraethylene pentamine (TEPA) in an amount of 0.125% by
weight. The
reaction was carried out at 140 C for four hours under a blanket of nitrogen
gas. The pour point
of the untreated RME was -12 C. After reaction with TEPA, the pour point was
reduced to -42 C.
Example 2
1-2 moles of diethylene triamine (DETA) was reacted with 1 mole of stearic
acid by
refluxing in xylene at 160 C. After completion, excess amine was removed
together with the
solvent by vacuum distillation. 1-aminoethyl-2-heptadecyl-imidazoline was
obtained as the
product. Soya-oil methyl ester (SME) having a C16 - C22 saturate content of
14.6% by weight was
reacted with the imidazoline in an amount of 0. 5% by weight. The reaction was
carried out at
150 C for four hours under a blanket of nitrogen gas. An ethylene vinyl
acetate (EVA) copolymer
in an amount of 0.6% by weight was added to the SME and the pour point was
measured to be -
õn P.11 i"! . pour point of the unreacted SME including, wh
copolymer was measured at -6 C.
Ex ample 3
Triethylene tetramine (TETA) was reacted with stearic acid in the same
proportions and
under the same reaction conditions as described in Example 2. 1-(N-aminoethyl-
aminoethyl)-2-
heptadecyl-imidazoline was obtained as the product. Soya-oil methyl ester
(SME) having a C16 -
C22 saturate content of 14.6% by weight was reacted with the imidazoline in an
amount of 0. 5%
by weight. The reaction was carried out at 150 C for four hours under a
blanket of nitrogen gas.
An ethylene vinyl acetate (EVA) copolymer in an amount of 0.6% by weight was
added to the
SME and the pour point was measured to be -51 C. By comparison, the pour point
of the
unreacted SME including the 0.6% of the EVA copolymer was measured at -6 C.
