Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
Process for Making Dibutyl Ethers from Dry Ethanol
FIELD OF THE INVENTION
The present invention relates to a process for making dibutyl ethers
using dry ethanol optionally obtained from a fermentation broth.
BACKGROUND
Dibutyl ethers are useful as diesel fuel cetane enhancers (R. Kotrba,
"Ahead of the Curve", in Ethanol Producer Magazine, November 2005); an
1o example of a diesel fuel formulation comprising dibutyl ether is disclosed
in
WO 2001018154. The production of dibutyl ethers from butanol is known
(see Karas, L. and Piel, W. J. Ethers, in Kirk-Othmer Encyclopedia of
Chemical Technology, Fifth Ed., Vol. 10, Section 5.3, p. 576) and is generally
carried out via the dehydration of n-butyl alcohol by sulfuric acid, or by
catalytic dehydration over ferric chloride, copper sulfate, silica, or silica-
alumina at high temperatures. The dehydration of butanol to dibutyl ethers
results in the formation of water, and thus these reactions have historically
been carried out in the absence of water.
Efforts directed at improving air quality and increasing energy
production from renewable resources have resulted in renewed interest in
alternative fuels, such as ethanol and butanol, that might replace gasoline
and
diesel fuel, or be additives in these fuels as well as others.
It is known that ethanol can be recovered from a number of sources,
including synthetic and fermentation feedstocks. Synthetically, ethanol can be
obtained by direct catalytic hydration of ethylene, indirect hydration of
ethylene, conversion of synthesis gas, homologation of methanol,
carbonylation of methanol and methyl acetate, and synthesis by both
homogeneous and heterogeneous catalysis. Fermentation feedstocks can be
fermentable carbohydrates (e.g., sugar cane, sugar beets, and fruit crops)
3o and starch materials (e.g., grains including corn, cassava, and sorghum).
When fermentation is used, yeasts from the species including Saccharomyces
can be employed, as can bacteria from the species Zymomonas, particularly
Zymomonas mobilis. Ethanol is generally recovered as an azeotrope with
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water", so that it is present at about 95 weight percent with respect to the
weight of water and ethanol combined. See Kosaric, et. al, Ullmann's
Encyclopedia of Industrial Chemistry, Sixth Edition, Volume 12, pages 398-
473, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, and P. L.
Rogers, et al., Adv. Biochem. Eng. 23 (1982) 27-84. The ethanol can be
further dried by methods known in the art (see Kosaric, supra), including
passing the ethanol-water azeotropic mixture over molecular sieves and
azeotropic distillation of the ethanol-water mixture with an entraining agent,
usually benzene.
Methods for producing 1-butanol from ethanol are known. It is known
that 1-butanol can be prepared by condensation from ethanol over basic
catalysts at high temperature using the so-called "Guerbet Reaction." See for
example, J. Logsdon in Kirk-Othmer Encyclopedia of Chemical Technology,
John Wiley and Sons, Inc., New York, 2001.
Some references further describing the production of 1-butanol from
ethanol include: Chinese Pat. No. CN 12168383C; C. Yang and Z. Meng, J.
of Catalysis (1993), 142(1), 37-44; A. S. Ndou, N. Plint, and N. J. Coville,
Applied Catalysis, A: General (2003), 251(2), 337-345; T. Takahashi, Kogyo
Kagaku Zasshi (1946), 49 113-114; T. Takahashi, Kogyo Kagaku Zasshi
(1946), 49 114-115; V. Nagarajan, N. R. Kuloor, Indian Journal of Technology
(1966), 4(2), 46-54; V. Nagarajan, Chemical Processing & Engineering
(Bombay) (1970), 4(11), 29-31, 38; V. Nagarajan, Indian Journal of
Technology (1971), 9(10), 380-386; V. Nagarajan, Chemical Processing &
Engineering (Bombay) (1971), 5(10), 23-27; K. W. Yang, X. Z. Jiang and W.
C. Zhang, Chinese Chemical Letters (2004), 15(112), 1497-1500; K. Yang,
W. Zhang, and X. Jiang, Chinese Patent No. 1528727 (assigned to Zhejiang
Univ.); C. A. Radlowski and G. P. Hagen, U. S. Pat. No. 5,095,156 (assigned
to Amoco Corp.); C. Y. Tsu and K. L. Yang, Huaxue (1958), (No. 1), 39-47; B.
N. Dolgov and Yu. N. Volnov, Zhurnal Obshchei Khimii (1993), 3 313-318; M.
J. L. Gines and E. Iglesia, J. of Catalysis (1998), 176(1), 155-172; T.
Tsuchida, AK. Atsumi, S. Sakuma, and T. Inui, US Pat. No. 6,323,383
(assigned to Kabushiki Kaisha Sangi); and GB Pat. No. 381,185, assigned to
British Industrial Solvents, Ltd.
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SUMMARY OF THE INVENTION
The present invention relates to a process for making butyl ethers
comprising:
a) contacting dry ethanol with a base catalyst to make a first reaction
product comprising 1-butanol;
b) recovering from the first reaction product a partially-purified first
reaction product consisting essentially of 1-butanol and no more than 5 weight
percent water based on the weight of the 1-butanol and water combined; and
c) contacting the partially-purified first reaction product of step (b),
optionally in the presence of a solvent, with at least one acid catalyst at a
temperature of about 50 degrees C to about 450 degrees C and a pressure
from about 0.1 MPa to about 20.7 MPa to produce a second reaction product
comprising at least one butyl ether, and recovering said at least one butyl
ether from said second reaction product to obtain at least one recovered butyl
ether.
The dry ethanol of step a) above can optionally be obtained from an
ethanol-containing fermentation broth.
The dibutyl ethers produced by the processes described in this
invention find use as additives for fuels, including transportation fuels such
as
gasoline, diesel and jet fuels.
DETAILS
The present invention relates to a process for making dibutyl ethers
from dry ethanol via dry butanol. As used herein, "dry butanol" refers to a
product consisting essentially of 1-butanol and no more than 5 weight percent
water based on the weight of the 1-butanol and water combined. The
expression "consisting essentially of' means herein that the 1-butanol may
include small amounts of other components as long as they do not affect
substantially the performance of combined 1-butanol and water in subsequent
process steps.
The dry ethanol can be obtained from any convenient source, including
fermentation using microbiological processes known to those skilled in the
art.
The fermentative microorganism and the source of the substrate are not
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critical for the purposes of this invention. The result of the fermentation is
a
fermentation broth, which is then refined to produce a stream of aqueous
ethanol. The refining process may comprise at least one distillation column to
produce a first overhead stream that comprises ethanol and water. Once the
ethanol-water azeotrope has been distilled off, one or more drying procedures
can be performed so that "dry ethanol" is formed. While many drying methods
are known, generally the reaction product (in this case, ethanol) is passed
over a dessicant, such as molecular sieves, until the desired amount of water
has been removed.
The dry ethanol (which may be diluted with an inert gas such as
nitrogen and carbon dioxide) is contacted with at least one base (or basic)
catalyst in the vapor or liquid phase at a temperature of about 150 degrees C
to about 500 degrees C and a pressure from about 0.1 MPa to about 20.7
MPa to produce a first reaction product comprising water and butanol.
Typically, the first reaction product will also comprise unreacted ethanol, a
variety of organic products, and water. The organic products include
butanols, predominantly 1-butanol.
The at least one base catalyst can be a homogeneous or
heterogeneous catalyst. Homogeneous catalysis is catalysis in which all
reactants and the catalyst are molecularly dispersed in one phase.
Homogeneous base catalysts include, but are not limited to, alkali metal
hydroxides.
Heterogeneous catalysis refers to catalysis in which the catalyst
constitutes a separate phase from the reactants and products. See, for
example, Hattori, H. (Chem. Rev. (1995) 95:537-550) and Solid Acid and
Base Catalysts (Tanabe, K., in Catalysis: Science and Technology, Anderson,
J. and Boudart, M (eds.) 1981 Springer-Verlag, New York) for a description of
solid catalysts and how to determine whether a particular catalyst is basic.
A suitable base catalyst useful in the current process is either a
substance which has the ability to accept protons as defined by Bronsted, or
as a substance which has an unshared electron pair with which it can form a
covalent bond with an atom, molecule or ion as defined by Lewis.
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Examples of suitable base catalysts may include, but may not be
limited to, metal oxides, hydroxides, carbonates, silicates, phosphates,
aluminates and combinations thereof. Preferred base catalysts may be metal
oxides, carbonates, silicates, and phosphates. Preferred metals of the
aforementioned compounds may be selected from Group 1, Group 2, and rare
earth elements of the Periodic Table. Particularly preferred metals may be
cesium, rubidium, calcium, magnesium, lithium, barium, potassium and
lanthanum.
The base catalyst may be supported on a catalyst support, as is
1o common in the art of catalysis. Suitable catalyst supports may include, but
may not be limited to, alumina, titania, silica, zirconia, zeolites, carbon,
clays,
double-layered hydroxides, hydrotalcites and combinations thereof. Any
method known in the art to prepare the supported catalyst can be used. One
method for preparing supported catalysts is to dissolve a metal carboxylate
salt in water. A support such as silica is wet with the solution, then
calcined.
This process converts the supported metal carboxylate to the metal oxide,
carbonate, hydroxide or combination thereof. The support can be neutral,
acidic or basic, as long as the surface of the catalyst/support combination is
basic. Commonly used techniques for treatment of supports with metal
catalysts can be found in B. C. Gates, Heterogeneous Catalysis, Vol. 2, pp.
1-29, Ed. B. L. Shapiro, Texas A& M University Press, College Station, TX,
1984.
The base catalysts of the present invention may further comprise
catalyst additives and promoters that will enhance the efficiency of the
catalyst. The relative percentage of the catalyst promoter may vary as
desired. Promoters may be selected from the Group 8 metals of the Periodic
Table, as well as copper and chromium.
The base catalysts of the invention can be obtained commercially, or
can be prepared from suitable starting materials using methods known in the
so art. The catalysts employed for the current invention may be used in the
form
of powders, granules, or other particulate forms. Selection of an optimal
average particle size for the catalyst will depend upon such process
parameters as reactor residence time and desired reactor flow rates.
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Examples of methods of using base catalysts to convert ethanol to
butanol are discussed in the following references.
M. N. Dvornikoff and M. W. Farrar, J. of Organic Chemistry (1957), 11,
540-542, disclose the use of MgO-K2CO3-CuCrO2 catalyst system to promote
ethanol condensation to higher alcohols, including 1-butanol. The disclosed
liquid phase reaction using this catalyst showed a 13% conversion of ethanol
and 47% selectivity to 1-butanol.
U.S. Pat. No. 5,300,695, assigned to Amoco Corp., discloses
processes in which an alcohol having X carbon atoms is reacted over an L-
io type zeolite catalyst to produce a higher molecular weight alcohol. In some
embodiments, a first alcohol having X carbon atoms is condensed with a
second alcohol having Y carbon atoms to produce an alcohol having X+Y
carbons. In one specific embodiment, ethanol is used to produce butanol
using a potassium L-type zeolite.
J. I. DiCosimo, et al., in Journal of Catalysis (2000), 190(2), 261-275,
describe the effect of composition and surface properties on alcohol-coupling
reactions using MgYAlOx catalysts for alcohol reactions, including ethanol.
Also condensation reactions on MgyAIOX samples involved the formation of a
carbanion intermediate on Lewis acid-strong Bronsted base pair sites and
yielded products containing a new C-C bond, such as n-C4H8O (or n-C4H9OH)
and iso-C4H80 (or iso-C4H9OH). They also describe, in Journal of Catalysis
(1998), 178(2), 499-510, that the oxidation to acetaidehyde and the aldol
condensation to n-butanol both involve initial surface ethoxide formation on a
Lewis acid-strong base pair.
PCT Publ. No. WO 2006059729 (assigned to Kabushiki Kaisha Sangi)
describes a clean process for efficiently producing, from ethanol as a raw
material, higher molecular weight alcohols having an even number of carbon
atoms, such as 1-butanol, hexanol and the like. The higher molecular weight
alcohols are yielded from ethanol as a starting material with the aid of a
calcium phosphate compound, e.g., hydroxyapatite Calo(PO4)6(OH)2,
tricalcium phosphate Ca3(PO4)2, calcium monohydrogen phosphate
CaHPO4X(0-2)H2O, calcium diphosphate Ca2P2O7, octacalcium phosphate
Ca$HZ(PO4)6X5H2O, tetracalcium phosphate Ca4(PO4)20, or amorphous
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calcium phosphate Ca3(PO4)2xnH2O, preferably hydroxyapatite, as a catalyst,
the contact time being 0.4 second or longer.
The catalytic conversion of the dry ethanol to the first reaction product
comprising 1-butanol and water can be run in either batch or continuous mode
s as described, for example, in H. Scott Fogler, (Elements of Chemical
Reaction
Engineering, 2nd Edition, (1992) Prentice-Hall Inc, CA). Suitable reactors
include fixed-bed, adiabatic, fluid-bed, transport bed, and moving bed. During
the course of the reaction, the catalyst may become fouled, and therefore it
may be necessary to regenerate the catalyst. Preferred methods of catalyst
io regeneration include, contacting the catalyst with a gas such as, but not
limited to, air, steam, hydrogen, nitrogen or combinations thereof, at an
elevated temperature.
The first reaction product is then subjected to a suitable refining
process to produce a partially-purified first reaction product consisting
15 essentially of 1-butanol and no more than 5 weight percent water, based on
the weight of the 1-butanol and water combined. An example of a suitable
refining process may include azeotropic distillation of the product to give a
condensate consisting of an upper butanol rich phase of butanol and water
and a lower water rich phase of butanol and water. A dry butanol stream may
20 then be recovered from the bottoms of a second distillation unit after
subjecting the upper condensed phase from the first distillation unit to
another
azeotropic distillation.
One skilled in the art will know that conditions, such as temperature,
catalytic metal, support, reactor configuration and time can affect the
reaction
25 kinetics, product yield and product selectivity. Standard experimentation
can
be used to optimize the yield of 1-butanol from the reaction.
The present invention relates to a process for making at least one
dibutyl ether comprising contacting the partially-purified first reaction
product
consisting essentially of 1-butanol and no more than 5 weight percent water
3o based on the weight of the 1-butanol and water combined with at least one
acid catalyst to produce a second reaction product comprising at least one
dibutyl ether, and recovering said at least one dibutyl ether from said second
reaction product to obtain at least one recovered dibutyl ether. The "at least
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one dibutyl ether" comprises primarily di-n-butyl ether, however the dibutyl
ether reaction product may comprise additional dibutyl ethers, wherein one or
both butyl substituents of the ether are selected from the group consisting of
1-butyl, 2-butyl, t-butyl and isobutyl.
The reaction to form at least one dibutyl ether is performed at a
temperature of from about 50 degrees Celsius to about 450 degrees Celsius.
In a more specific embodiment, the temperature is from about 100 degrees
Celsius to about 250 degrees Celsius.
The reaction can be carried out under an inert atmosphere at a
io pressure of from about atmospheric pressure (about 0.1 MPa) to about 20.7
MPa. In a more specific embodiment, the pressure is from about 0.1 MPa to
about 3.45 MPa. Suitable inert gases include nitrogen, argon and helium.
The at least one acid catalyst can be a homogeneous or
heterogeneous catalyst. Homogeneous catalysis is catalysis in which all
reactants and the catalyst are molecularly dispersed in one phase.
Homogeneous acid catalysts include, but are not limited to inorganic acids,
organic sulfonic acids, heteropolyacids, fluoroalkyl sulfonic acids, metal
sulfonates, metal trifluoroacetates, compounds thereof and combinations
thereof. Examples of homogeneous acid catalysts include sulfuric acid,
fluorosulfonic acid, phosphoric acid, p-toluenesulfonic acid, benzenesulfonic
acid, hydrogen fluoride, phosphotungstic acid, phosphomolybdic acid, and
trifluoromethanesulfonic acid.
Heterogeneous catalysis refers to catalysis in which the catalyst
constitutes a separate phase from the reactants and products.
Heterogeneous acid catalysts include, but are not limited to 1) heterogeneous
heteropolyacids (HPAs), 2) natural clay minerals, such as those containing
alumina or silica, 3) cation exchange resins, 4) metal oxides, 5) mixed metal
oxides, 6) metal salts such as metal sulfides, metal sulfates, metal
sulfonates,
metal nitrates, metal phosphates, metal phosphonates, metal molybdates,
metal tungstates, metal borates, and 7) zeolites, 8) combinations of groups 1
- 7. See, for example, Solid Acid and Base Catalysts, pages 231-273
(Tanabe, K., in Catalysis: Science and Technology, Anderson, J. and Boudart,
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M (eds.) 1981 Springer-Verlag, New York) for a description of solid catalysts.
The heterogeneous acid catalyst may also be supported on a catalyst
support. A support is a material on which the acid catalyst is dispersed.
Catalyst supports are well known in the art and are described, for example, in
Satterfield, C. N. (Heterogeneous Catalysis in Industrial Practice, 2"d
Edition,
Chapter 4(1991) McGraw-Hill, New York).
One skilled in the art will know that conditions, such as temperature,
catalytic metal, support, reactor configuration and time can affect the
reaction
kinetics, product yield and product selectivity. Depending on the reaction
conditions, such as the particular catalyst used, products other than dibutyl
ethers may be produced when 1-butanol is contacted with an acid catalyst.
Additional products comprise butenes and isooctenes. Standard
experimentation, performed as described in the Examples herein, can be
used to optimize the yield of dibutyl ether from the reaction.
Following the reaction, if necessary, the catalyst can be separated from
the reaction product by any suitable technique known to those skilled in the
art, such as decantation, filtration, extraction or membrane separation (see
Perry, R.H. and Green, D.W. (eds), Perry's Chemical Engineer's Handbook,
2o 7th Edition, Section 13, 1997, McGraw-Hill, New York, Sections 18 and 22).
The at least one dibutyl ether can be recovered from the reaction
product by distillation as described in Seader, J.D., et al (Distillation, in
Perry,
R.H. and Green, D.W. (eds), Perry's Chemical Engineer's Handbook, 7 th
Edition, Section 13, 1997, McGraw-Hill, New York). Alternatively, the at least
one dibutyl ether can be recovered by phase separation, or extraction with a
suitable solvent, such as trimethylpentane or octane, as is well known in the
art. Unreacted 1-butanol can be recovered following separation of the at least
one dibutyl ether and used in subsequent reactions. The at least one
recovered dibutyl ether can be added to a transportation fuel as a fuel
3o additive.
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EXAMPLES
GENERAL METHODS AND MATERIALS
In the following examples, "C" is degrees Celsius, "mg" is milligram;
"ml" is milliliter; "temp" is temperature; "MPa" is mega Pascal; "GC/MS" is
gas
chromatography/mass spectrometry.
Amberlyst (manufactured by Rohm and Haas, Philadelphia, PA),
tungstic acid, 1-butanol and H2SO4 were obtained from Alfa Aesar (Ward Hill,
MA); CBV-3020E was obtained from PQ Corporation (Berwyn, PA); Sulfated
Zirconia was obtained from Engelhard Corporation (Iselin, NJ); 13%
1o Nafion /Si02 can be obtained from Engelhard; and H-Mordenite can be
obtained from Zeolyst Intl. (Valley Forge, PA).
General Procedure for the Conversion of 1-Butanol to Dibutyl Ethers
A mixture of 1-butanol and catalyst was contained in a 2 ml vial
equipped with a magnetic stir bar. The vial was sealed with a serum cap
perforated with a needle to facilitate gas exchange. The vial was placed in a
block heater enclosed in a pressure vessel. The vessel was purged with
nitrogen and the pressure was set at 6.9 MPa. The block was brought to the
indicated temperature and controlled at that temperature for the time
indicated. After cooling and venting, the contents of the vial were analyzed
by GC/MS using a capillary column (either (a) CP-Wax 58 [Varian; Palo Alto,
CA], 25 m X 0.25 mm, 45 C/6 min, 10 C/min up to 200 C, 200 C /10 min, or
(b) DB-1701 [J&W (available through Agilent; Palo Alto, CA)], 30 m X 0.2
5mm, 50 C /10 min, 10 C /min up to 250 C, 250 C /2 min).
The examples below were performed according to this procedure
under the conditions indicated for each example.
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EXAMPLES 1-13
Reaction of dry 1-butanol (1-BuOH) with an acid catalyst to produce dibutyl
ethers
The reactions were carried out for 2 hours at 6.9 MPa of N2.
Example Catalyst (50 mg) Temp 1-BuOH Dibutyl Ethers
Number (C) % Conversion % Selectivity
1 H2SO4 200 93.6 75.6
2 Amberlyst 15 200 65.8 81.0
13%
3 200 39.2 96.9
Nafion /Si02
4 CBV-3020E 200 86.8 90.2
5 H-Mordenite 200 69.5 74.6
6 Tungstic Acid 200 9.3 61.1
7 H2SO4 120 6.9 65.1
8 Amberlyst 15 120 1.0 53.0
13%
9 120 0.4 30.0
Nafion /Si02
CBV-3020E 120 1.2 39.1
11 H-Mordenite 120 1.4 20.0
12 Tungstic Acid 120 1.2 26.1
Sulfated
13 120 0.9 6.6
Zirconia
As those skilled in the art of catalysis know, when working with any
catalyst, the reaction conditions need to be optimized. Examples 1 to 13
show that the indicated catalysts were capable under the indicated conditions
io of producing the product dibutyl ethers. Some of the catalysts shown in
Examples 1 to 13 were ineffective when utilized at suboptimal conditions (data
not shown).
11
