U.S. patent application number 11/994123 was filed with the patent office on 2008-09-11 for biodiesel fuel mixture containing polyoxymethylene dialkyl ether.
This patent application is currently assigned to BASF Aktiengesellschaft. Invention is credited to Matthias Eiermann, Andrea Haunert, Jorn Karl, Rolf Pinkos, Heiner Schelling, Eckhard Stroefer, Gerd-Dieter Tebben.
Application Number | 20080216390 11/994123 |
Document ID | / |
Family ID | 36997811 |
Filed Date | 2008-09-11 |
United States Patent
Application |
20080216390 |
Kind Code |
A1 |
Tebben; Gerd-Dieter ; et
al. |
September 11, 2008 |
Biodiesel Fuel Mixture Containing Polyoxymethylene Dialkyl
Ether
Abstract
A biodiesel fuel mixture having a cetane number of >40,
comprising a) from 1 to 100% by weight of biodiesel, b) from 0 to
98.9% by weight of diesel oil of fossil origin, c) from 0.1 to 20%
by weight of polyoxyalkylene dialkyl ether of the formula
RO(CH.sub.2O).sub.nR in which R is an alkyl group having from 1 to
10 carbon atoms and n=from 2 to 10, and d) from 0 to 5% by weight
of further additives.
Inventors: |
Tebben; Gerd-Dieter;
(Mannheim, DE) ; Schelling; Heiner; (Kirchheim,
DE) ; Stroefer; Eckhard; (Mannheim, DE) ;
Pinkos; Rolf; (Bad Durkheim, DE) ; Haunert;
Andrea; (Mannheim, DE) ; Eiermann; Matthias;
(Limburgerhof, DE) ; Karl; Jorn; (Ludwigshafen,
DE) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
BASF Aktiengesellschaft
Ludwigshafen
DE
|
Family ID: |
36997811 |
Appl. No.: |
11/994123 |
Filed: |
June 26, 2006 |
PCT Filed: |
June 26, 2006 |
PCT NO: |
PCT/EP2006/063531 |
371 Date: |
December 28, 2007 |
Current U.S.
Class: |
44/307 |
Current CPC
Class: |
C10L 1/1852 20130101;
C10L 1/19 20130101; C10L 10/02 20130101; Y02E 50/13 20130101; C10L
1/1616 20130101; C10L 1/14 20130101; C10G 2300/1011 20130101; C10G
2300/80 20130101; C10L 1/1985 20130101; C10L 1/026 20130101; C10L
10/12 20130101; C10G 2300/307 20130101; Y02P 30/20 20151101; Y02E
50/10 20130101 |
Class at
Publication: |
44/307 |
International
Class: |
C10L 1/00 20060101
C10L001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 29, 2005 |
DE |
10 2005 030 282.3 |
Claims
1-6. (canceled)
7. A biodiesel fuel mixture comprising: a) 5-90 wt. % biodiesel; b)
0-94 wt. % diesel oil of fossil origin; c) 1-20 wt. %
polyoxymethylene dialkyl ether represented by the following general
formula: RO(CH.sub.2O).sub.nR wherein R is an alkyl group having
from 1 to 10 carbon atoms, and n is from 2 to 10; and d) 0-5 wt. %
further additives, wherein the biodiesel fuel mixture has a cetane
number of >40.
8. The biodiesel fuel mixture according to claim 7, wherein the
polyoxymethylene dialkyl ether of c) comprises 3, 4 or 5
oxymethylene repeat units, or a mixture thereof.
9. The biodiesel fuel mixture according to claim 7, wherein the
polyoxymethylene dialkyl ether of c) is a polyoxymethylene dimethyl
ether.
10. The biodiesel fuel mixture according to claim 7, wherein the
biodiesel fuel mixture has a cetane number of >45.
11. A biodiesel fuel mixture comprising: a) 5-90 wt. % biodiesel;
b) 6-92 wt. % diesel oil of fossil origin; c) 3-11 wt. %
polyoxyalkylene dialkyl ether; and d) 0-1 wt. % cetane number
improver, wherein the biodiesel fuel mixture has a cetane number of
>40.
12. The biodiesel fuel mixture according to claim 11, wherein the
polyoxyalkylene dialkyl ether of c) is a polyoxymethylene dialkyl
ether represented by the following general formula:
RO(CH.sub.2O).sub.nR wherein R is an alkyl group having from 1 to
10 carbon atoms, and n is from 2 to 10.
13. The biodiesel fuel mixture according to claim 12, wherein the
polyoxymethylene dialkyl ether of c) comprises 3, 4 or 5
oxymethylene repeat units, or a mixture thereof.
14. The biodiesel fuel mixture according to claim 12, wherein the
polyoxymethylene dialkyl ether of c) is a polyoxymethylene dimethyl
ether.
15. The biodiesel fuel mixture according to claim 12, wherein the
biodiesel fuel mixture has a cetane number of >45.
16. An additive for increasing the cetane number in a biodiesel
fuel mixture having at least 1% by weight of biodiesel, wherein the
additive comprises a polyoxymethylene dialkyl ether represented by
the following general formula: RO(CH.sub.2O).sub.nR wherein R is an
alkyl group having from 1 to 10 carbon atoms, and n is from 2 to
10.
17. The additive according to claim 16, wherein the
polyoxymethylene dialkyl ether comprises 3, 4 or 5 oxymethylene
repeat units, or a mixture thereof.
18. The additive according to claim 16, wherein the
polyoxymethylene dialkyl ether is a polyoxymethylene dimethyl
ether.
19. The additive according to claim 16, having a cetane number of
>40.
20. The additive according to claim 16, having a cetane number of
>45.
Description
[0001] The present invention relates to a biodiesel fuel mixture
comprising polyoxymethylene dialkyl ether.
[0002] For many years, industry has been making efforts to identify
alternative energy sources which are not of fossil origin, and also
to make available so-called renewable raw materials. The latter
include vegetable oils, i.e. fatty acid esters, typically
triglycerides, which can generally be classified as biodegradable
and harmless to the environment. Rapeseed oil can be regarded as a
prototype of such vegetable oils. In general, such oils comprise
the glycerides of a number of acids, the acids being variable with
the type and origin of the vegetable oil, and additionally
phosphoglycides if appropriate. Such oils may be obtained by known
processes. The vegetable oils can be transesterified to obtain the
alkyl esters, for example the methyl esters, of the fatty acids
bonded in the glycerides.
[0003] FR-A 2 492 402 describes a fuel composition comprising one
or more fatty acid esters of animal or vegetable origin of the
general formula R.sup.1--COOR.sup.2, in which R.sup.1 is a
substantially linear saturated or unsaturated aliphatic radical
having from 5 to 23 carbon atoms and R.sup.2 is a linear or
branched, saturated or unsaturated aliphatic radical having 1 to 12
carbon atoms. Such fuel compositions are described as being
suitable for use in diesel engines since they have a cetane number
which corresponds approximately to the cetane number of
conventional diesel fuels which are obtained from mineral oils.
[0004] The main advantage of biodiesel as a renewable fuel is the
reduction in the net CO.sub.2 emission. Moreover, the exhaust
emissions of sulfur oxides, particles and carbon monoxide are
reduced. In contrast, the nitrogen oxide emissions can be slightly
increased. Thus, it can be assumed that the amount of CO.sub.2
released when biodiesel is combusted (approx. 2.4 t/t of biodiesel)
can be assimilated again by growing plants from which vegetable
oils for biodiesel are obtained in turn, so that the net CO.sub.2
output is close to 0. Biodiesel is also virtually sulfur-free
(sulfur content between 0 and 0.0024 ppm, compared to up to 350 ppm
of sulfur in conventional fossil diesel fuel). Although the NOx
emissions from pure biodiesel are on average 6% above those from
diesel of fossil origin, the absence of sulfur enables techniques
for NOx reduction which cannot be employed in conjunction with
conventional fossil diesel. The oxygenates present in the biodiesel
improve the combustion and the emission profile, so that about 20%
less carbon monoxide is formed compared to fossil diesel fuel. The
particle emissions from biodiesel are also significantly lower and
are 40% or more below those of conventional fossil diesel. The
biodegradability of biodiesel is greatly increased compared to
fossil diesel.
[0005] The energy content of biodiesel is still 92% of that of
fossil diesel, so that approx. 1.1 l of biodiesel replace 1 l of
fossil diesel fuel.
[0006] Future European diesel specifications are aiming
considerably in the direction of higher cetane numbers, while the
content of sulfur and polyaromatic hydrocarbons is to be
reduced.
[0007] It is known that the cetane number of diesel fuels can be
increased by admixing linear ethers. In addition, the cold
properties of the fuel are improved and the dilution reduces the
contents of aromatic hydrocarbons and sulfur. The ethers also have
a positive effect on the emissions. The high cetane number leads to
lower emission of hydrocarbons and carbon monoxide. The high oxygen
content in the ether additionally leads to a reduction of soot
particles in the exhaust gas.
[0008] EP-A 1 070 755 discloses a diesel fuel mixture with a cetane
number >40 composed of a typical diesel oil cut and from 1 to
20% by volume of polyoxymethylene dialkyl ethers. The addition of
the polyoxymethylene dialkyl ethers raises the cetane number from
48 to a value between 63 and 100.
[0009] It is an object of the invention to provide a
biodiesel-based diesel fuel mixture with a high cetane number and
good emission profile.
[0010] The object is achieved by a biodiesel fuel mixture having a
cetane number of >40, comprising [0011] a) from 1 to 100% by
weight of biodiesel, [0012] b) from 0 to 98.9% by weight of diesel
oil of fossil origin, [0013] c) from 0.1 to 20% by weight of
polyoxyalkylene dialkyl ether of the formula
[0013] RO(CH.sub.2O).sub.nR in which R is an alkyl group having
from 1 to 10 carbon atoms and n=from 2 to 10, and [0014] d) from 0
to 5% by weight of further additives.
[0015] As component a), the inventive biodiesel fuel mixture
comprises from 1 to 100% by weight, generally from 5 to 90% by
weight, preferably from 5 to 50% by weight and more preferably from
10 to 50% by weight, of biodiesel. Biodiesel generally has a
viscosity at 40.degree. C. of from 1.9 to 6.5 cSt, preferably from
3.5 to 5.0 cSt, a sulfur content of not more than 0.05% by weight,
preferably 0.01% by weight, a cetane number of at least 40,
preferably at least 49, and an acid number of up to 0.80 mg KOH/g,
preferably of up to 0.50 mg KOH/g. Biodiesel consists generally of
fatty acid esters of the general formula R.sup.1--COOR.sup.2 in
which R.sup.1 is a substantially linear saturated or unsaturated
aliphatic radical having from 5 to 23 carbon atoms and R.sup.2 is a
linear or branched, saturated or unsaturated aliphatic radical
having from 1 to 12 carbon atoms. The fatty acid esters present in
the biodiesel preferably derive from linear, saturated or
unsaturated fatty acids R.sup.1COOH with from 11 to 23 carbon atoms
in the R.sup.1 radical, in particular from saturated fatty acids
such as lauric acid, myristic acid, palmitic acid, stearic acid,
arachic acid, behenic acid and lignoceric acid, monoethylenically
unsaturated fatty acids such as lauroleic acid, myristoleic acid,
palmitoleic acid, oleic acid, gadoleic acid and erucic acid, and
also di- or polyethylenically unsaturated fatty acids such as
linoleic acid and linolenic acid. The fatty acids of the fatty acid
esters present in the biodiesel are obtained from vegetable or
animal fats. Vegetable fats are, for example, rapeseed oil,
sunflower oil, copra oil, corn oil, cottonseed oil, soya oil and
peanut oil. Suitable fats of animal origin are, for example, pork
fat or beef tallow.
[0016] The alcohol component of the ester present in biodiesel is
preferably selected from methanol, ethanol, n-propanol,
isopropanol, n-butanol, isobutanol, 2-ethylhexanol or dodecanol.
The fatty acid esters are preferably obtained from the glycerides
present in the natural fats of vegetable or animal origin by
transesterification with the alcohol R.sup.2OH.
[0017] As component b), the inventive biodiesel fuel mixture
comprises conventional diesel oil of fossil origin. Diesel
represents the high boiler fraction of the middle distillates of
mineral oil. Typical diesel oil cuts have a boiling point in the
range from 150 to 380.degree. C., preferably from 200 to
350.degree. C., and a density of from 0.76 to 0.935 g/ml at
15.degree. C.
[0018] As component c), the inventive biodiesel fuel mixture
comprises from 0.1 to 20% by weight, generally from 1 to 20% by
weight, preferably from 3 to 11% by weight, more preferably from 4
to 11% by weight, of polyoxymethylene dialkyl ether. Among these,
preference is given to the dimethyl ether and diethyl ether.
Preference is further given to polyoxymethylene dialkyl ethers with
n=3, 4 or 5 oxymethylene units, and also mixtures thereof.
Particular preference is given to polyoxymethylene dimethyl ethers
with 3, 4 or 5 oxymethylene units and mixtures thereof.
Particularly preferred are polyoxymethylene dimethyl ethers with
n=3 or 4 oxymethylene units and mixtures thereof; especially
preferred is tetraoxymethylene dimethyl ether (n=4).
[0019] The invention also provides for the use of the
polyoxymethylene dialkyl ethers as additives for biodiesel fuel
mixtures which comprise at least 1% by weight of biodiesel for
increasing the cetane number.
[0020] The polyoxymethylene dialkyl ethers c) may, as described in
EP-A 1 070 755 be prepared by reacting the appropriate alcohol,
preferably methanol, with formaldehyde in the presence of acidic
catalysts.
[0021] A particularly advantageous process for preparing
polyoxymethylene dimethyl ethers which are particularly suitable as
biodiesel fuel additives c), in particular the polyoxymethylene
dimethyl ethers where n=3 and 4 (trimer, tetramer), starts from
methylal (n=1) and trioxane. These are fed into a reactor and
reacted in the presence of an acidic catalyst, the amount of water
introduced into the reaction mixture by methylal, trioxane and/or
the catalyst being <1% by weight based on the reaction
mixture.
[0022] In the reaction of methylal with trioxane to give the
polyoxymethylene dimethyl ethers, no water is formed as a
by-product. The reaction is carried out generally at a temperature
of from 50 to 200.degree. C., preferably from 90 to 150.degree. C.,
and a pressure of from 1 to 20 bar, preferably from 2 to 10 bar.
The molar methylal:trioxane ratio is generally from 0.1 to 10,
preferably from 0.5 to 5.
[0023] The acidic catalyst may be a homogeneous or heterogeneous
acidic catalyst. Suitable acidic catalysts are mineral acids such
as substantially anhydrous sulfuric acid, sulfonic acids such as
trifluoromethanesulfonic acid and para-toluenesulfonic acid,
heteropolyacids, acid ion exchange resins, zeolites,
aluminosilicates, silicon dioxide, aluminum oxide, titanium dioxide
and zirconium dioxide. Oxidic catalysts may, in order to increase
their acid strength, be doped with sulfate or phosphate groups,
generally in amounts of from 0.05 to 10% by weight. The reaction
may be carried out in a stirred tank reactor (CSTR) or a tubular
reactor. When a heterogeneous catalyst is used, preference is given
to a fixed bed reactor. When a fixed catalyst bed is used, the
product mixture can subsequently be contacted with an anion
exchange resin in order to obtain a substantially acid-free product
mixture.
[0024] The amount of water introduced by methylal and trioxane and
by the catalyst is in total <1% by weight, preferably <0.5%
by weight, more preferably <0.2% by weight and in particular
<0.1% by weight, based on the reaction mixture composed of
methylal, trioxane and the catalyst. For this purpose, virtually
anhydrous trioxane and methylal are used, and the amount of water
introduced by the catalyst, if appropriate, is correspondingly
restricted. The hemiacetals (monoethers) or polyoxymethylene
glycols formed by hydrolysis in the presence of water from already
formed polyoxymethylene dimethyl ether have a comparable boiling
point to the polyoxymethylene dimethyl ethers, which complicates
removal of the polyoxymethylene dimethyl ethers from these
by-products.
[0025] In order to obtain polyoxymethylene dimethyl ethers where
n=3 and n=4 (trimer, tetramer) in a controlled manner, a fraction
comprising the trimer and tetramer is removed from the product
mixture of the reaction of methylal with trioxane, and unconverted
methylal, trioxane and polyoxymethylene dimethyl ether where n<3
are recycled into the acid-catalyzed reaction. In a further
embodiment of the process according to the invention, the
polyoxymethylene dimethyl ethers where n>4 are additionally also
recycled into the reaction. As a result of the recycling, a
particularly large amount of trimer and tetramer is obtained.
[0026] In a particularly preferred embodiment, a first fraction
comprising methylal, a second fraction comprising the dimer (n=2)
and trioxane, a third fraction comprising the trimer and tetramer
(n=3, 4) and a fourth fraction comprising the pentamer and higher
homologs (n>4) are obtained from the product mixture of the
acid-catalyzed reaction of methylal with trioxane. It is especially
preferred in this context to carry out the removal of the product
mixture of the acid-catalyzed reaction of methylal with trioxane in
three distillation columns connected in series, the first fraction
being removed from the product mixture of the reaction in one
distillation column, the second fraction being removed from the
remaining mixture in a second distillation column, and the
remaining mixture being separated into the third and the fourth
fraction in a third distillation column. In this separation, the
first distillation column may be operated, for example, at a
pressure of from 0.5 to 1.5 bar, the second distillation column,
for example, at a pressure of from 0.05 to 1 bar and the third
distillation column, for example, at a pressure of from 0.001 to
0.5 bar. Preference is given to recycling the first and the second
fraction, more preferably additionally also the fourth fraction,
into the reaction.
[0027] When a homogeneous catalyst, for example a mineral acid or a
sulfonic acid, is used, it remains in the fourth fraction and is
recycled with it into the acid-catalyzed reaction.
[0028] It is common knowledge that acetals, which also include the
polyoxymethylene dialkyl ethers used in the present context, are
cleaved under acidic conditions. Biodiesel has an acid number of
generally at least 0.1 mg KOH/g and up to 0.8 mg KOH/g (according
to US standard) or of up to 0.5 mg KOH/g (according to DIN 51606).
As a result of an increase in the water content during storage or
during consumption, the acid number can rise further as a result of
the shift in the chemical equilibrium from fatty acid esters to
fatty acids. The acidic properties of the biodiesel lead to the
expectation that the polyoxymethylene dialkyl ethers will not be
stable in biodiesel and will be cleaved to formaldehyde and
methanol. However, it has been found that, surprisingly, this is
not the case and polyoxymethylene dimethyl ethers are entirely
stable in biodiesel and biodiesel/diesel mixtures in spite of the
acidic properties of biodiesel.
[0029] As component d), the inventive biodiesel fuel mixtures may
comprise from 0 to 5% by weight, preferably from 0 to 1% by weight,
of further additives. Typical further additives are cetane number
improvers which may be present in amounts of typically up to 1% by
weight.
[0030] The inventive biodiesel fuel mixture has a cetane number of
>40, generally of >45, preferably of >50, more preferably
of >52.
[0031] A preferred inventive biodiesel mixture comprises [0032] a)
from 5 to 90% by weight of biodiesel [0033] b) from 6 to 92% by
weight of diesel oil of fossil origin [0034] c) from 3 to 11% by
weight of polyoxyalkylene dialkyl ether [0035] d) from 0 to 1% by
weight of cetane number improver.
[0036] The invention is illustrated in detail by the example which
follows.
EXAMPLES
Example 1
[0037] 150 g of biodiesel (Connediesel.RTM. CD 99, acid number=0.12
mg KOH/g) and 20 g of tetraoxymethylene dimethyl ether
H.sub.3CO(CH.sub.2O).sub.4CH.sub.3 were stirred at 25.degree. C.
The content of H.sub.3CO(CH.sub.2O).sub.4CH.sub.3 was determined by
gas chromatography at regular intervals. Over the entire
experimental duration of 12 days, no decrease in the
H.sub.3CO(CH.sub.2O).sub.4CH.sub.3 content was detected.
Example 2
[0038] 150 g of diesel and 20 g of tetraoxymethylene dimethyl ether
H.sub.3CO(CH.sub.2O).sub.4CH.sub.3 were stirred at 25.degree. C.
The content of H.sub.3CO(CH.sub.2O).sub.4CH.sub.3 was determined by
gas chromatography at regular intervals. Over the entire
experimental duration of 12 days, no decrease in the
H.sub.3CO(CH.sub.2O).sub.4CH.sub.3 content was detected.
* * * * *