Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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A process for preparing a fuel additive a.nd the additive.
The present invention relates to a method for manufacturing a fuel additive
and the
additive. The invention particularly relates to a lubricating additive, which
is
especially suitable for use as an additive used with diesel engines.
The continual increase in the prices of fuels, particularly fuels for
combustion
engines, and the tightening of environmental regulations have lead to numerous
proposed and actual improvements in both engines and in fuels.
In automotive engines, engines based on the Diesel cycle are gaining ground
over
petrol engines, due to the greater thermal efficiency of diesel engines. In
addition
to their existing efficiency, based on a high compression ratio, their
operation has
been further improved by using fuel injection into the combustion chamber.
At the same time as environmental demands have led to a great reduction in the
sulphur content of these fuels, polyaromatic and other closed-chain compounds,
which as such have excellent lubricating properties for high-pressure fuel-
injection
equipment, have been removed from the fuel along with the sulphur.
Fatty acids have proven to be good additives for fuel, particularly diesel
fuel.
However, fatty acids have the well-known drawback that they crystallize or
that
substances such as stearic acid and arachid acid crystallize easily out of
them, in
other words, fatty acids as such are not suitable for very cold conditions.
The
esters of these acids also easily crystallize out of, for instance, olive oil.
US patent 6,129,772 discloses a fuel additive, manufactured from saturated
fatty
acids and from oligomeric fatty acids, in which tertiary amines are used to
prevent
crystallization. The patent emphasizes especially that mixtures of different
saturated fatty acids are not used, but gives no reasons for this.
US patent 5,578,090 discloses a fuel and a fuel additive, which is
characterized in
that it is composed of the esters of fatty acids, some of which are glycerine
esters
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and some are triglycerides.
WO 94/17160 discloses a fuel additive, comprising a fatty acid, which is
esterified
using alcohol containing one or several carbons.
EP 826765 discloses a corresponding diesel-fuel additive, which is a fatty
acid and
a partial ester of polyol, for example, glycerine and an ester of
monocarboxylic
acid, 75 - 200 ppm of which is added to middle distillates.
US 3,765,850 discloses an additive obtained by permitting dicarboxylic acid to
react with polyamides.
US patent 6,156,082 discloses that it is preferable if a fuel lubricant is not
esterified, as the lubricity will then suffer. However, this patent describes
partial
esterification with diethylene glycol and an organic acid anhydride, which
results in
excellent lubricity.
US patent 6,194,361 discloses that a usable lubricant can be obtained from the
distilled fatty acids of tall oil by allowing the fatty acid of tall oil to
react with dietha-
nolamine and then allowing the fatty acid to react with aminoethylpiperazidine
after
the previous reaction. This compound is used, among other things, for
lubricating
oil wells, both with oil and as a water emulsion.
US patent 6,197,731 discloses that a suitable lubricant for two-stroke engine
fuel
can be obtained by esterifying polyols with polycarboxylic acids.
JP 08092581 discloses how the -OH group of castor oil can be esterified with a
saturated monovalent fatty acid to obtain a lubricant that will operate at
very low
temperatures.
US patent 6,086,645 discloses how a fuel additive can be advantageously
obtained by manufacturing amides of carboxylic acids for this purpose from
oleic
acid and/or linolenic acid.
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US patent 5,882,364 discloses a corresponding fuel additive comprising the
esters
of an unsaturated fatty acid and a polyvalent alcohol, two grades of which are
mixed together in the same mixture.
US patent 6,203, 584 discloses a fuel additive comprising esters of polybasic
carboxylic acid and polyoxyamine and a mixture of carboxylic acid and an ester
of
polyvalent alcohol, which acts with them.
US patent 5,997,593 discloses a fuel lubricant comprising the reaction product
of
carboxylic acid and an amine, in which the said amine is guanidine, amino gua-
nidine, urea, or thiourea.
US patent 6,051,039 discloses a diesel fuel additive, which is obtained from
an
amine of dicarboxylic acid, which is an amine derivative of succinic acid or
phtalic
acid and their mixture, as well as of an NR3 amine, in which R contains 6 - 24
carbons. The mixture is added to diesel fuel in a concentration of at least
1000
ppm.
US patent 5,556,972 discloses how fats can be fractionated by crystallizing a
stearin ester fraction from an oleic acid traction in two stages and removing
the
said stearin fat fraction by filtration. This reduces the cloud point of the
fat. The
process is carried out by countercurrent crystallization, which thus reduces,
for
example, the congealing point of margarine.
US patent 5,952,518 discloses a method, by means of which fatty acids with a
high melting point can be removed from other fatty acids. In this case, the
assistance of an emulsifier is used, the mixture is cooled, and the saturated
fatty
acids are removed from the mixture by crystallization. Esters of a polyvalent
alcohol and a fatty acid are used as the emulsifier. The fatty acids are
hydrolyzed
rapeseed or soya oils.
The fatty acids of tall oil, as stated in many patents, act well as fuel
lubricants in
combustion engines, as do their alcohol esters with alcohols, and the amines
of
fatty acids. However, the fatty acids as such would be the best lubricants.
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Saturated fatty acids and their derivatives are stated to act particularly
well as
lubricants.
Particularly stearic acids and their salts have been used throughout history
as
good lubricants.
The present invention is intended to create a lubricant based on fatty acids
and a
method for manufacturing it for use as a fuel additive to improve lubrication.
This is
achieved in the manner stated to be characteristic in the accompanying Claims.
According to this invention, the question is how to very advantageously
eliminate
the said problems and drawbacks, when using compositions of tall oil and other
fatty acids as an internal lubricant in fuel at low temperatures.
According to the invention, the fatty-acid composition is given a cold-
treatment,
preferably using such a heat exchanger, in which the fatty-acid composition is
circulated, until a sufficient share of the amount of the fatty acids has
crystallized
on the heat-transfer surfaces of the heat exchanger being used and essentially
only unsaturated fatty acids flow out of the composition.
Typically, saturated fatty acids crystallize out of a tall oil fatty-acid
composition
already at a temperature of 10° C, most of the stearic acid
crystallizing already at a
temperature of 5° C. The rest will also crystallize at the temperature
range 5 - 0°
C. Normally, the crystallization process is slow and can take many days when
the
said fatty-acid mixtures stand in a vessel. This is due to the low diffusion
coefficient and the high viscosity in cold conditions. When the composition is
pumped through a heat-transfer surface, the low diffusivity is compensated by
the
mass transfer caused by the flow as such.
Now that the saturated fatty acids have been made to solidify on a heat-
transfer
surface, they can be removed from the surtace by separately heating it. Thus a
new fatty-acid composition is obtained, which has a substantially greater
amount
than before of saturated fatty acids, typically palmitinic acid, stearic acid,
and
arachinic acid. Typically these total, for example, 2 - 4 % by weight of a
tall oil
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fatty-acid composition. The melting point of unsaturated fatty acids is riiuch
lower
than that of saturated fatty acids, but the lubricating properties of
saturated fatty
acids are, in turn, better, which is a generally known fact.
5 The separated saturated fatty acids can be preferably esterified, aminated,
and
permitted to react with enhancing cyclic compounds, such as lactams,
oxazolidines, and similar. It is generally known that the melting point,
solidifying
point, or the pour point known in technology of each mixture occurs at a lower
temperature, the more the mixture contains related but not identical
compounds.
Further, it is possible to envisage and claim that the more a mixture contains
such
compounds (in this case fatty-acid compounds), which form steric inhibitions
to
crystallization, branchings, branches, pendant groups, etc., then the lower
will be
the temperature at which the mixture will solidify, or at which crystals or a
separate
phase of some compound will precipitate from it.
According to the present invention, at least most of the saturated fatty acids
are
separated from a fatty-acid composition by crystallization at a low
temperature,
and are made to react with an alcohol mixture, preferably with waste, i.e.
fusel oil,
obtained from the manufacture of alcohol, which contains many alcohols with a
high boiling point, so that a mixture of many esters will be obtained
directly. Some
of the saturated fatty acids are, in turn, made to react with amines,
particularly with
N,N-dimethyl or N,N-diethyl amines, when an excellent solvent and a low
melting
point for the said solvent will be obtained.
Part of the saturated fatty-acids separated from the composition can be
advantageously made to react at an increased temperature and in the presence
of
an acid catalyst with lactams, preferably with capric lactam. This reaction
must not
include a large number of unsaturated fatty acids, because polymerization
takes
place easily and a solid phase with a high melting point will be obtained
(+50°C) .
Before the reaction with amines, preferably N,N- dimethyl or diethyl amines, a
small amount of an oleic acid - linoleic acid mixture can be added to the
mixture,
thus providing an advantageous solvent for other reactions.
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Thus, according to the present invention, saturated fatty acids are separated
from
a fatty-acid mixture by crystallizing them, preferably on cold heat-transfer
surfaces,
the mixture of essentially saturated fatty acid being separated by heating the
said
heat-transfer surface and given an esterifying treatment in the presence of an
acid
catalyst, preferably using an alcohol mixture containing many different
alcohols
and/or a part of the said mixture of saturated fatty acids being allowed to
react with
amines, preferably with N,N-diammine and/or a part being permitted to react
with
lactams, preferably with capric lactam, at an increased temperature, and at
least
one of these reaction mixtures being re-mixed with the original mixture made
from
essentially unsaturated fatty acids.
The aforementioned method has advantages, including the fact that only part of
the fatty acids, generally 2 - 5 %, must be treated and the best fatty acids,
even
though modified, can be used for lubrication. If the separate and modified
fraction
is multi-modified, the solidification point of this fraction will be at a
lower
temperature than if it had been esterified or aminated using only a single
reagent.
The reaction product of capric lactam and fatty acids is like vaseline,
provided the
reaction of the product is stopped at a suitably early stage, for example, 30
min
/150° C. If the product is kept hot, for example, for 2 hours, a
relatively solid
product will result, which will not longer optimally suit the purpose referred
to here.
The catalyst used is an acid catalyst, para-toluenesulphonic acid, Lewis acid,
or
concentrated cation exchange resin or sulphuric acid, which must, however, be
washed out. Normal Lewis acids, such as AIC13 are very suitable for this
purpose.
When aminating fatty acids, there is reason to use advantageously N,N-dimethyl
or ethyl fatty-acid amines, as they do not form hydrogen bridges with each
other
and thus remain liquid at room temperature.
When esterifying fatty acids, one of the cheapest raw materials is an alcohol
mixture, which in the alcohol industry goes by the name of fusel oil. It this
is used
in esterifying, many esters of fatty acids and acids will be obtained at one
time,
while a low solidification point for the reaction mixture will also be
obtained.
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The product thus obtained is typically mixed with diesel fuel to form a 0.01 -
0.04
mixture.
Example 1
A tall oil-fatty acid mixture, which according to analysis contained
palmitinic acid
0.4 % , sfiearic acid 1.1 %, and arachid acid 0.4%, was cooled to and kept
cooled
at a temperature of + 5.5° C, until no further sediment was deposited
from it. In
this case, the solution was filtered, the filtration producing about 50 ml of
mixture
from a litre of the original composition. The solidification point of the
sediment was
35° C. The composition of this mixture contained 8.3 % of stearic acid
(1.1 % in
the original mixture). It is obvious that filtration in a laboratory will not
produce such
good results as crystallization on cold heat-transfer surfaces, because a
large
amount of the other acids present in the mixture will remain between the
crystals
of the sedimented stearic acid.
Example 2
29 g of the stearic-acid concentrate obtained in Example 1 and 10 g of capric
lactam were allowed to react with each other with a small amount of AIC13
acting
as a catalyst while being mixed for 2.5 hours, during which time the melting
point
of 40° C had dropped to a value of 35° C. The result was a
viscous golden-brown
liquid, which was like vaseline at room temperature. Later, a part of it
precipitated,
which solidified when the mixture was kept for 2 days at a temperature of
60° C, in
other words, it had continued to polymerize.
Example 3
Fusel oil traditionally contains salts that can be removed prior to use in
esterification, for example, by distillation. However, in this case the salts
were
removed in another way; i.e. the fusel oil was cooled to a temperature of -
18°C,
when about one-fifth of the water precipitated as a salt phase, which was
removed
together with the salts, the remainder being used as follows.
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Thus, stearic acid was esterified using an alcohol mixture, of so-called fusel
oil,
which was obtained from the waste of the distillation of ethanol. The
composition
of the fusel oil was: propanol 3 w-%, isobutanol 24 w-%, 2-methyl-1-butanol 12
w-
%, 3-methyl-1-butanol 37 w-%, ethanol 8 w-%, water 14 w-% ja solids in the
form
of salts 0.5 g/litre, which were removed according to the above procedure.
g stearic acid (sp 67 - 69° C) was mixed with 80 ml of the fusel oil
described
above and a small amount (2 drops) of sulphuric acid was added. The mixture
was
first heated, while being mixed, at a temperature of 94.2° C for 2
hours, after which
10 the surplus alcohols were distilled out, when the remainder of the alcohols
also
began to leave at a temperature of 145° C. The mixture was washed with
water to
remove the acid residues. The remaining ester mixture was still entirely fluid
and
clear at a temperature of +14.5° C. It will be obvious to one versed in
the art that if
the said esterification has been carried out using the stearic-acid
concentrate
referred to previously, a clearly smaller amount of processing could have been
achieved, as the relative amount of saturated fatty acids would have been
greater.
Example 4
30 g of the fatty-acid mixture of Example 1, concentrated in relation to
stearic acid,
was allowed to react with 13.6 g of di-N-butyl amine, using a drop of
sulphuric acid
as a catalyst, at a temperature of 120° C for 4 hours while mixing, a
pale orange
liquid being obtained, which was highly fluid at a temperature of + 7°
C. A clear
increase in the viscosity of the liquid began only at a temperature of
+2° C while it
began to form a solid phase only at a temperature of -1 ° C.
Example 5
The solution remaining in Example 2, which was a light brown liquid, with a
viscosity clearly greater than that of fatty acids, was mixed with the
filtrate of
Example 1, in which there was thus a large amount of unsaturated fatty acids,
together with the amine esters of stearic acid manufactured in Example 4, in
which
case the amount corresponded to the amount of the 'stearic-acid fraction'
removed
by crystallization. The fatty-acid mixture thus created was allowed to stand
for
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several days at a temperature of +2° C, during which time no sediment
appeared
in it, even though the same original product (Example 1 , +5° C)
continued to
crystallize significantly in the same conditions.
Example 6
The same amount that had been removed of both the alcohol-esterified stearic
acid and the mixture of saturated fatty acids esterified using di-N-butyl
amine (the
sediment that had been filtered from the original solution at a temperature of
+2°
C), were added to the fatty-acid mixture of Example 1, from which the
saturated
fatty acids that had crystallized at a low temperature had been filtered out.
This solution was kept at a temperature of -1 ° C for 7 days. No
sediment was
deposited from it, nor did it become cloudy. At the same time, further
sediment
began to settle, at the same temperature, from the alkali solution from which
sediment had been removed at a temperature of +2° C.
ExamJ~le 7
28 g of the sediment of saturated fatty acids separated according to Example 1
was melted and 10 g of capric lactam and 2 drops of AIC13 solution were added
to
it and the reaction was allowed to proceed while mixing at a temperature of
150° C
for 60 minutes. The result was a vaseline-like product, with a solidification
point of
35° C, the solidification point of the original liquid being 40°
C. An amount of this
product corresponding to the stearic acid and arachid acid together with the
fusel-
oil esters was mixed with the filtrate according to Example 1, so that there
was as
much of each reaction product calculated as stearic acid, as had been removed
from it. After being allowed to stand for 3 days at a temperature of -1
°C, an
amount of needle-like crystals, which were only just visible to the naked eye,
was
deposited from the product. When the crystals were melted and the product was
allowed to stand for 4 days at a temperature of +5° C, no further
sediment or
crystals were formed.
When a mixture of esters of di-N-butyl amine stearic acid, arachid acid, and
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palmitinic acid of 0.5 ml per 100 ml was added to this mixture, a fatty-acid
solution
was created, from which nothing further was deposited at -1 ° C. The
product was
also noted to have an easily emulsifying effect on water.
