U.S. patent application number 12/673091 was filed with the patent office on 2011-12-01 for liquid biofuel made of esters and bound glycerides, and also process for production thereof.
Invention is credited to Peter Eisner, Michael Frankl, Andreas Malberg, Michael Menner, Andreas Stabler.
Application Number | 20110289828 12/673091 |
Document ID | / |
Family ID | 40155933 |
Filed Date | 2011-12-01 |
United States Patent
Application |
20110289828 |
Kind Code |
A1 |
Eisner; Peter ; et
al. |
December 1, 2011 |
LIQUID BIOFUEL MADE OF ESTERS AND BOUND GLYCERIDES, AND ALSO
PROCESS FOR PRODUCTION THEREOF
Abstract
The present invention relates to a biofuel and to a process for
production thereof, which biofuel contains at least one fraction of
triglycerides, a fraction of monoglycerides, a fraction of
diglycerides and a fraction of alkylesters of fatty acids. The
biofuel may be obtained by partial transesterification of vegetable
oil or vegetable fat and is distinguished in that the mass fraction
of alkylesters of fatty acids in the biofuel is smaller than the
mass fraction of triglycerides. The fuel is suitable in particular
as additive for conventional fuels, may be produced at high yield
and can also be used at relatively low temperatures below
10.degree. C.
Inventors: |
Eisner; Peter; (Freising,
DE) ; Menner; Michael; (Eichenau, DE) ;
Stabler; Andreas; (Munchen, DE) ; Malberg;
Andreas; (Munchen, DE) ; Frankl; Michael;
(Munchen, DE) |
Family ID: |
40155933 |
Appl. No.: |
12/673091 |
Filed: |
July 31, 2008 |
PCT Filed: |
July 31, 2008 |
PCT NO: |
PCT/DE2008/001268 |
371 Date: |
August 9, 2011 |
Current U.S.
Class: |
44/308 |
Current CPC
Class: |
C10L 1/19 20130101; Y02E
50/13 20130101; C10L 1/191 20130101; C10L 1/02 20130101; C10G
2300/1011 20130101; C10G 2300/1014 20130101; Y02E 50/10 20130101;
Y02P 30/20 20151101; C10L 1/026 20130101; C11C 3/003 20130101; C12P
7/649 20130101 |
Class at
Publication: |
44/308 |
International
Class: |
C10L 1/18 20060101
C10L001/18 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 13, 2007 |
DE |
10 2007 038 232.6 |
Claims
1. Biofuel that contains at least one fraction of triglycerides, a
fraction of monoglycerides, a fraction of diglycerides and a
fraction of alkylesters of fatty acids, characterized in that the
mass fraction of alkylesters of fatty acids in the biofuel is
smaller than the mass fraction of triglycerides.
2. The biofuel according to claim 1, characterized in that the
ratio of mass fractions of diglycerides to monoglycerides is
.gtoreq.2.
3. The biofuel according to either of claim 1 or 2, characterized
in that the mass fraction of alkylesters of fatty acids is not less
than 15% and not more than 35%.
4. The biofuel according to either of claim 1 or 2, characterized
in that the mass fraction of triglycerides is at least 30%.
5. The biofuel according to claim 4, characterized in that the mass
fraction of triglycerides is greater than 40%.
6. The biofuel according to claim 5, characterized in that the mass
fraction of triglycerides is not more than 65%.
7. The biofuel according to either of claim 1 or 2, characterized
in that the mass fraction of monoglycerides is between 0.1% and
10%.
8. The biofuel according to either of claim 1 or 2, characterized
in that the mass fraction of diglycerides is between 4% and
30%.
9. The biofuel according to claim 1, characterized in that the mass
fraction of alkylesters of fatty acids is between 20% and 25%, the
mass fraction of triglycerides is between 50% and 55%, the mass
fraction of diglycerides is 20%, and the mass fraction of
monoglycerides is 5%.
10. The biofuel according to claim 1, characterized in that the
biofuel contains an additive of ethanol having a mass fraction of
up to 2%.
11. The biofuel according to claim 1, which is mixed with fossil
fuel, biodiesel or BTL-fuel.
12. Use of the biofuel according to claim 1 as a fuel for internal
combustion engines.
13. Process for producing the biofuel according to any of claims 1
to 11 by partial transesterification of triglycerides, wherein at
least one fraction each is obtained consisting of triglycerides,
monoglycerides, diglycerides, and alkylesters of fatty acids,
characterized in that the partial transesterification is carried
out in such manner that the mass fraction of alkylesters of fatty
acids in the biofuel is smaller than the mass fraction of
triglycerides.
14. The process according to claim 13, characterized in that the
partial transesterification is carried out in such manner that the
ratio of mass fractions of diglycerides to monoglycerides is
.gtoreq.2.
15. The process according to either of claim 13 or 14,
characterized in that carrier-bound sn-1,3 regiospecific lipases
are used as the catalyst for partial transesterification.
16. The process according to claim 15, characterized in that the
partial transesterification is completed with gradual addition of
enzymes over the course of several discontinuous production
cycles.
17. The process according to either of claim 13 or 14,
characterized in that alcohol is added in sub-stoichiometric
quantity for the transesterification.
18. The process according to claim 17, characterized in that
alcohol is added continuously or in several steps during the
transesterification.
19. The process according to claim 18, characterized in that when
alcohol is added in several steps, an alcohol concentration of 3%
by mass is not exceeded.
20. The process according to either of claim 13 or 14,
characterized in that for transesterification, alcohol is first
dissolved in a reaction mixture that is largely free from lipases
and contains the triglycerides, and that the reaction mixture is
not brought into contact with the lipases as the catalyst until the
alcohol has been completely dissolved.
21. The process according to claim 20, characterized in that an
alcohol concentration of .ltoreq.5% by mass is adjusted in the
reaction mixture before it is brought into contact with the
lipases.
22. The process according to either of claim 13 or 14,
characterized in that the partial transesterification takes place
with vegetable oil or vegetable fat as the triglycerides.
Description
TECHNICAL FIELD
[0001] The present invention relates to a liquid biofuel having a
basis of triglycerides, mono- and diglycerides, and alkylesters of
fatty acids, and a process for production thereof. The fuel is
particularly suitable as a substitute for conventional fuels, for
example diesel. It is also possible to use it directly as a fuel in
combustion engines.
STATE OF THE ART
[0002] Biofuels and biofuel mixtures based on vegetable oil and
animal fat are described for example in Patent Nos. DE 4116905 C1,
WO 95/25152 A1, EP 855436 A2, or U.S. Pat. No. 5,713,965A. These
documents particularly disclose mixtures of rapeseed oils with
petrol or diesel, to which an additional substance is added. In
German Patent No. DE 4116905 C1, this additional component is an
alcohol, in WO 95/25152 A1, it is an alkylester of a short-chain
fatty acid having a maximum chain length of 6 C atoms, and in EP
855436 A2 it is an acetal.
[0003] Patent specifications U.S. Pat. No. 5,713,965 A, U.S. Pat.
No. 5,480,787 A and EP 1705238 A1 (=WO 2005075615 A1) describe
processes for the production of alkylesters of fatty acids by
lipase-catalysed transesterification of oils and fats. In these
processes, the fatty acid alkylesters of bound and free glycerol
are separated by known methods and accordingly are not used as a
fuel fraction. Since the glycerol is separated, the yield relative
to the feedstock oil or fat is only about 90%.
[0004] Patent specification EP 1126011 A2 describes a process for
homoegenously catalysed transesterification of fats and oils under
conditions in which at least one of the reactants is present in a
critical state. As with the specifications cited in the preceding,
U.S. Pat. No. 5,713,965 A, U.S. Pat. No. 5,480,787 A, and EP
1705238 A1, in this case too the glycerol produced is separated
from the fatty acid alkylesters and is not used as a fuel
fraction.
[0005] Patent specification U.S. Pat. No. 55,788,090 A describes a
biofuel consisting of fatty acid alkylesters and bound glycerol.
Unlike the fuel described in the present document, the bound
glycerides are not present in the form of mono-, di-, and
trialkylglycerol esters, but as mono-, di-, and trialkylglycerol
ethers. These ethers are produced in a reaction that differs from
transesterification, as intermediate products of the
transesterification reaction.
[0006] Patent specification U.S. Pat. No. 5,316,927 A describes a
process for producing monoglycerides and fatty acid alkylesters via
lipase-catalysed transesterification of fats and oils. When the
reaction is complete, the two products are separated from one
another and fed to different applications.
[0007] Diesel fuel is a refined petroleum product that represents a
considerable portion of the international fuel market. Finite
resources, dramatic price increases, and the ongoing debate
regarding climate have led to renewed efforts to at least partially
replace fossil diesel with fuels from renewable raw materials.
[0008] At the moment, the most of such raw materials are drawn from
vegetable oil and biodiesel (alkylesters of fatty acids). Vegetable
oils largely consist of triglycerides, that is to say esters of
glycerol, and three fatty acids, and in smaller quantities, free
fatty acids.
[0009] The use of pure vegetable oil as diesel fuel is not without
certain difficulties. Because of its high viscosity and low cetane
number, the triglycerides are only partially combusted, which
results in deposits on valves and fuel injectors, and high emission
values. Mixing vegetable oil with fossil diesel also presents
problems, because such mixtures are unstable, particularly at low
temperatures, and consequently there is a danger that they will
separate in the fuel tank.
[0010] These problems can be largely avoided by transesterification
of triglycerides with a monovalent alcohol. The fatty acid
alkylesters produced have a viscosity and cetane number similar to
those of diesel, and are thus able to be used as a diesel
substitute relatively easily.
[0011] Besides alkylesters of fatty acids (biodiesel),
transesterifying vegetable or animal oils or fats also produces
about 10% free glycerol. Free glycerol is insoluble in biodiesel
and therefore cannot be used as a fuel fraction. The separated free
glycerol lowers the fuel yield of the process, and since it needs
to undergo downstream processing and the revenue situation
therefrom is unfavourable, it represents a not insignificant cost
factor.
[0012] A fuel that is produced by partial transesterification of
triglycerides is described in PCT/DE2005/002156. In this case, the
fuel yield is 100%, because the glycerol contained in the fats and
oils is not liberated, but is kept in solution in the form of
mono-, di-, and triglycerides. This mixture of bound glycerol and
fatty acid alkylesters is stable at room temperature. At lower
temperatures however, below 10.degree. C., crystallisation
processes are triggered and individual components are precipitated,
particularly with the compositions described as especially
advantageous in PCT/DE2005/002156. Consequently, the fuel described
in PCT/DE2005/002156 is only suitable for use at room temperature
or higher temperatures. The fuel described is therefore not
suitable precisely in regions where low temperatures prevail.
[0013] The object of the present invention consists in providing a
biofuel, and a process for production thereof, which may be
produced with a high yield and is also usable at lower
temperatures.
DESCRIPTION OF THE INVENTION
[0014] The object is solved with the biofuel according to claim 1
and the process according to claim 13. Advantageous compositions of
the biofuel and configurations of the processes for production
thereof are described in the subordinate claims or will be evident
from the following description and embodiments.
[0015] The biofuel according to the invention contains at least one
fraction of triglycerides, particularly vegetable oil or vegetable
fat, and at least one fraction of monoglycerides and at least one
fraction of diglycerides, and further contains at least one
fraction of alkylesters of fatty acids.
[0016] Surprisingly, it was found that there is a defined range of
compositions with the fractions cited, for which, despite a lower
viscosity and higher cetane number, it is possible, by partial
transesterification, to keep all of the glycerol contained in the
oil in solution in the form of mono-, di- and triglycerides, and to
store the product even at temperatures below 10.degree. C., without
demixing or crystallisation. Such demixing does not occur even
after the biofuel according to the invention is mixed with diesel
fuel, although mixing with diesel does cause the polarity of the
mixture to change. Mixtures of the biofuel according to the
invention with diesel thus remain clear and monophasic even in
wintry conditions.
[0017] It was found that in order to achieve optimum solubility of
glycerides in fatty acid alkylesters (FAAEs) even at lower
temperatures, it is critically important that the fraction of FAAEs
in the fuel is smaller than the fraction of triglycerides. The
triglycerides dissolve particularly readily even at temperatures
below 10.degree. C. if the mass fraction of the triglyceride
content is selected to be greater than 29%, advantageously greater
than 40%, and the mass fraction of the FAAE is adjusted to greater
than 14% and less than 36%.
[0018] A further factor for increasing the solubility of glycerides
in FAAE-containing fuels is the ratio of monoglycerides to
diglycerides.
[0019] If the ratio of diglycerides to monoglycerides is below a
value of 2, particles are precipitated particularly rapidly.
[0020] The following composition contains a mixture of mono-, di-,
and triglycerides with FAAE that is particularly advantageous for
cold storage:
TABLE-US-00001 Minimum mass Maximum mass Component % value % value
FAAE 15 35 Monoglycerides 0.1 10 Diglycerides 4 30 Triglycerides 30
65
[0021] A mixture having a composition of 20-25% by mass FAAE,
50-55% by mass triglycerides, 20% by mass diglycerides, and 5% by
mass monoglycerides proved to be particularly stable at low
temperatures. A further improvement in terms of low-temperature
stability may be achieved by adding up to 2% by mass of
ethanol.
[0022] The biofuel may be mixed in any ratio with fossil fuel,
biodiesel or BTL-fuel, and in this context it may be diluted and
used as fuel for internal combustion engines. It is also possible
to dilute the fuel according to the invention by adding diesel fuel
or biodiesel before the partial esterification of the
triglycerides.
[0023] It is also expedient to use mono- and diglycerides
originating from another reaction in the biofuel, such as those
that are formed when vegetable oil is transesterified into fatty
acid alkylesters. However, it is also possible, and under certain
circumstances may be advantageous, to use mono-, di-, and
triglycerides that originate from another source, if applicable
from an animal source, or are possibly of synthetic origin. For
example, it is possible to use mono- and diglycerides in the
biofuel that contain fatty acids with fewer than 10 carbon
atoms.
[0024] One possible production process for the suggested biofuel is
based on partial esterification of triglycerides. For this,
triglycerides are mixed with an alcohol and a reaction is provoked
by adding a catalyst or placing them in contact with a catalyst.
The triglycerides used may be a raw material of vegetable, animal
or synthetic origin, or mixtures of triglycerides from different
sources.
[0025] The alcohol used is preferably a monovalent alcohol with any
chain length. Either organic or inorganic compounds, or enzymes or
microorganisms may be used as the catalyst. The reaction may be
triggered by homogeneous or heterogeneous catalysis. In a
financially particularly advantageous form, used cooking fats serve
as the raw material source.
[0026] The composition of the biofuel, particularly the ratio of
the mass fractions of fatty acid alkylesters and triglycerides
and/or the mass fractions of diglycerides relative to the
monoglycerides, may be adjusted via the residence time, the type
and quantity of catalytic material, and the quantity of alcohol
used. In this context, residence time is considered to be the
period for which the catalyst and the added alcohol are in contact
with the triglycerides.
[0027] Use of carrier-bound sn-1,3 regiospecific lipases as the
catalyst is particularly advantageous. In this context, adding
enzymes incrementally over the course of several discontinuous
production cycles has proven to produce a particularly good yield.
In each production cycle, the enzyme from the previous cycle is
used, a small additional quantity of fresh enzyme being added in
each cycle to obtain a particularly good yield.
[0028] It was also discovered that the gradual addition of the
alcohol in sub-stoichiometric quantities in several steps or
continuous addition of alcohol is particularly advantageous. The
gradual or continuous addition of alcohol is to be set up as far as
possible so that the concentration of alcohol does not exceed 4% by
mass. A maximum alcohol concentration of 3% by mass has proven
particularly advantageous for high stability and thus also a long
service life of the enzyme.
[0029] It has also proven advantageous to the same purpose if the
alcohol is dissolved in a reaction mixture that is largely free
from lipases, and is not brought into contact with the lipases
again until the alcohol is completely dissolved. In this context,
lipase-free product is removed from the reaction vessel several
times during the production cycle for use in dissolving the alcohol
that is needed for the reaction. In this way, it is possible to
avoid bringing high alcohol concentrations into contact with the
enzyme. In this context it was found that the alcohol concentration
in the reaction mixture described should not exceed 5% before it is
remixed with the lipase.
[0030] The process temperature is determined by the catalyst
employed, and on the triglyceride used, in particular by the
melting point thereof. The residence time is determined by the
catalyst employed, the quantity of the catalyst, the alcohol used,
and the triglyceride used.
Embodiment
[0031] 2.0 g ethanol are fully dissolved in 100 g rapeseed oil. The
transesterification reaction is started by adding 1.0 g of an
immobilised s.sub.n-1,3 regiospecific lipase. The mixture is mixed
thoroughly for 3 hours at the temperature of highest lipase
activity.
[0032] After 3 hours, 50 mL of lipase-free intermediate product is
removed from the reaction vessel. 2.0 g of ethanol are completely
dissolved in the reaction medium that has been removed. Then, the
product-ethanol solution is returned to the reaction vessel. This
step is then repeated after a further 3 hours' residence time.
[0033] After a total of 10 hours, the lipase is separated from the
reaction product, and a clear, monophasic liquid is obtained,
consisting of 30% by mass fatty acid ethyl ester, 24% by mass
diglycerides, 9% by mass monoglycerides, and 36% by mass
triglycerides, and about 1% by mass ethanol.
[0034] The separated enzyme may be reused in a second production
cycle. This is performed in identical manner to the cycle described
in the preceding. At the start of the reaction, 0.1 g fresh enzyme
is added to the enzyme that was used in the first production
cycle.
* * * * *