Patent Application
20090023959
The present invention relates to a process for making dibutyl ethers using dry 1-butanol obtained from fermentation broth.
Dibutyl ethers are useful as diesel fuel cetane enhancers (R. Kotrba, “Ahead of the Curve”, in Ethanol Producer Magazine, November 2005); an 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.
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. Efforts are currently underway to increase the efficiency of 1-butanol production by fermentative microorganisms utilizing renewable feedstocks, such as corn waste and sugar cane bagasse, as carbon sources. It would be desirable to be able to utilize such 1-butanol streams to produce fuel additives, such as dibutyl ethers.
The present invention relates to a process for making at least one dibutyl ether comprising:
(a) obtaining a fermentation broth comprising 1-butanol;
(b) separating dry 1-butanol from said fermentation broth to form separated dry 1-butanol;
(c) contacting the separated dry 1-butanol 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 reaction product comprising said at least one dibutyl ether; and
(d) recovering said at least one dibutyl ether from said reaction product to obtain at least one recovered dibutyl ether.
The expression “dry 1-butanol” as used in the present specification and claims denotes a material that is predominantly 1-butanol, but may contain small amounts of water (under about 5% by weight relative to the weight of the 1-butanol plus the water), and may contain small amounts of other materials, such as acetone and ethanol, as long as they do not materially affect the catalytic reaction previously described when performed with reagent grade 1-butanol.
The at least one dibutyl ether is useful as a transportation fuel additive.
The Drawing consists of eight figures.
The present invention relates to a process for making at least one dibutyl ether from dry 1-butanol derived from fermentation broth. The at least one dibutyl ether so produced is useful as an additive in transportation fuels, wherein transportation fuels include, but are not limited to, gasoline, diesel fuel and jet fuel.
More specifically, the present invention relates to a process for making at least one dibutyl ether comprising contacting dry 1-butanol with at least one acid catalyst to produce a reaction product comprising at least one dibutyl ether, and recovering said at least one dibutyl ether from said reaction product to obtain at least one recovered dibutyl ether. The “at least 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 dry dibutyl ether reactant for the process of the invention is derived from fermentation broth. One advantage to the microbial (fermentative) production of butanol is the ability to utilize feedstocks derived from renewable sources, such as corn stalks, corn cobs, sugar cane, sugar beets or wheat, for the fermentation process. Efforts are currently underway to engineer (through recombinant means) or select for organisms that produce butanol with greater efficiency than is obtained with current microorganisms. Such efforts are expected to be successful, and the process of the present invention will be applicable to any fermentation process that produces 1-butanol at levels currently seen with wild-type microorganisms, or with genetically modified microorganisms from which enhanced production of 1-butanol is obtained.
The most well-known method for the microbial production of 1-butanol is the acetone-butanol-ethanol (ABE) fermentation carried out by solventogenic clostridia, such as Clostridium beijerinickii or C. acetobutylicum. Substrates useful for clostridial fermentation include glucose, maltodextrin and sugars, which may be obtained from biomass, such as corn waste, sugar cane, sugar beets, wheat, hay or straw. A discussion of anaerobiosis and detailed procedures for the preparation of growth media and the growth and storage of anaerobic bacteria (including the sporeforming clostridial species) can be found in Section II of Methods for General and Molecular Bacteriology (Gerhardt, P. et al. (ed.), (1994) American Society for Microbiology, Washington, D.C.). U.S. Pat. Nos. 6,358,717 (Column 3, line 48 through Column 15, line 21) and 5,192,673 (Columns 2, line 43 through Column 6, line 57) describe in detail the growth of, and production of butanol by, mutant strains of C. beijerinckii and C. acetobutylicum, respectively.
An alternative method for the production of 1-butanol by fermentation is a continuous, two-stage process as described in U.S. Pat. No. 5,753,474 (Column 2, line 55 through Column 10, line 67) in which 1-butanol is the major product. In the first stage of the process, a clostridial species, such as C. tyrobutyricum or C. thermobutyricum, is used to convert a carbohydrate substrate predominantly to butyric acid. In a minor, parallel process, a second clostridial species, such as C. acetobutylicum or C. beijerinkii, is grown on a carbohydrate substrate under conditions that promote acidogenesis. The butyric acid produced in the first stage is transferred to a second fermentor, along with the second clostridial species, and in the second, solventogenesis stage of the process, the butyric acid is converted by the second clostridial species to 1-butanol.
1-Butanol can also be fermentatively produced by recombinant microorganisms as described in copending and commonly owned U.S. patent application Ser. No. 60/721677, page 3, line 22 through page 48, line 23, including the sequence listing. The biosynthetic pathway enables recombinant organisms to produce a fermentation product comprising 1-butanol from a substrate such as glucose; in addition to 1-butanol, ethanol is formed. The biosynthetic pathway enables recombinant organisms to produce 1-butanol from a substrate such as glucose. The biosynthetic pathway to 1-butanol comprises the following substrate to product conversions:
a) acetyl-CoA to acetoacetyl-CoA, as catalyzed for example by acetyl-CoA acetyltransferase encoded by the genes given as SEQ ID NO:1 or 3;
The biological production of butanol by microorganisms is believed to be limited by butanol toxicity to the host organism. Copending and commonly owned application docket number CL-3423, page 5, line 1 through page 36, Table 5 , and including the sequence listing (filed 4 May 2006) enables a method for selecting for microorganisms having enhanced tolerance to butanol, wherein “butanol” refers to 1-butanol, 2-butanol, isobutanol or combinations thereof. A method is provided for the isolation of a butanol tolerant microorganism comprising:
Fermentation methodology is well known in the art, and can be carried out in a batch-wise, continuous or semi-continuous manner. As is well known to those skilled in the art, the concentration of 1-butanol in the fermentation broth produced by any process will depend on the microbial strain and the conditions, such as temperature, growth medium, mixing and substrate, under which the microorganism is grown.
Following fermentation, the fermentation broth from the fermentor is subjected to a refining process to recover a stream comprising dry 1-butanol. By “refining process” is meant a process comprising one unit operation or a series of unit operations that allows for the purification of an impure aqueous stream comprising 1-butanol to yield a stream comprising dry 1-butanol.
Typically, refining processes will utilize one or more distillation steps as a means for producing a dry 1-butanol stream. It is well known, however, that fermentative processes typically produce 1-butanol at very low concentrations. This can lead to large capital and energy expenditures to recover the 1-butanol by distillation alone. As such, other techniques can be used in combination with distillation as a means of recovering the 1-butanol. In such processes where separation techniques are integrated with the fermentation step, cells are often removed from the stream to be refined by centrifugation or membrane separation techniques, yielding a clarified fermentation broth. The removed cells are then returned to the fermentor to improve the productivity of the 1-butanol fermentation process. The clarified fermentation broth is then subjected to such techniques as pervaporation, gas stripping, liquid-liquid extraction, perstraction, adsorption, distillation or combinations thereof. The streams generated by these methods can then be treated further by distillation to yield a dry 1-butanol stream.
In the ABE fermentation, acetone and ethanol are produced in addition to 1-butanol. The recovery of a butanol stream from an ABE fermentation is well known, and is described, for example, by D. T. Jones (in Clostridia, John Wiley & Sons, New York, 2001, page 125) or by Lenz, T. G. and Moreira, A. R. (Ind. Eng. Chem. Prod. Res. Dev. (1980) 19:478-483). Fermentation broth is first fed to a beer still. A vapor stream comprising a mixture of 1-butanol, acetone, ethanol and water is recovered from the top of the column, while a mixture comprising water and cell biomass is removed from the bottom of the column. The vapor stream is subjected to one distillation step or a series of distillation steps, by which acetone and ethanol are separated, and a stream comprising dry 1-butanol is obtained. This dry 1-butanol stream can then be used as the reactant for the process of the present invention.
For fermentation processes in which 1-butanol is the predominant alcohol of the fermentation broth (see U.S. Pat. No. 5,753,474 as described above), dry 1-butanol can be recovered by azeotropic distillation, as described generally in Ramey, D. and Yang, S.-T. (Production of butyric acid and butanol from biomass, Final Report of work performed under U. S. Department of Energy DE-F-G02-00ER86106, pages 57-58) for the production of 1-butanol. The aqueous butanol stream from the fermentation broth is fed to a distillation column, from which the butanol-water azeotrope is removed as a vapor phase. The vapor phase from the distillation column (comprising at least about 42% water (by weight relative to the weight of the water plus 1-butanol)) can then be fed to a condenser. Upon cooling, a butanol-rich phase (comprising at least about 18% water (by weight relative to the weight of the water plus 1-butanol)) will separate from a water-rich phase in the condenser. One skilled in the art will know that solubility is a function of temperature, and that the actual concentration of water in the aqueous 1-butanol stream will vary with temperature. The butanol-rich phase can be decanted and sent to a distillation column whereby butanol is separated from water. The dry 1-butanol stream obtained from this column can then be used as the reactant for the process of the present invention.
For fermentation processes in which an aqueous stream comprising 1-butanol and ethanol are produced, without significant quantities of acetone, the aqueous 1-butanol/ethanol stream is fed to a distillation column, from which a ternary 1-butanol/ethanol/water azeotrope is removed. The azeotrope of 1-butanol, ethanol and water is fed to a second distillation column from which an ethanol/water azeotrope is removed as an overhead stream. A stream comprising 1-butanol, water and some ethanol is then cooled and fed to a decanter to form a butanol-rich phase and a water-rich phase. The butanol-rich phase is fed to a third distillation column to separate a 1-butanol stream from an ethanol/water stream. The dry 1-butanol stream obtained from this column can then be used as the reactant for the process of the present invention
Generally, there are two steps involved in the removal of volatile components by pervaporation. One is the sorption of the volatile component into a membrane, and the other is the diffusion of the volatile component through the membrane due to a concentration gradient. The concentration gradient is created either by a vacuum applied to the opposite side of the membrane or through the use of a sweep gas, such as air or carbon dioxide, also applied along the backside of the membrane. Pervaporation for the separation of 1-butanol from a fermentation broth has been described by Meagher, M. M., et al in U.S. Pat. No. 5,755,967 (Column 5, line 20 through Column 20, line 59) and by Liu, F., et al (Separation and Purification Technology (2005) 42:273-282). According to U.S. Pat. No. 5,755,967, acetone and/or 1-butanol were selectively removed from an ABE fermentation broth using a pervaporation membrane comprising silicalite particles embedded in a polymer matrix. Examples of polymers include polydimethylsiloxane and cellulose acetate, and vacuum was used as the means to create the concentration gradient. A stream comprising 1-butanol and water will be recovered from this process, and this stream can be further treated by distillation to produce a dry 1-butanol stream that can be used as the reactant of the present invention.
In general, gas stripping refers to the removal of volatile compounds, such as butanol, from fermentation broth by passing a flow of stripping gas, such as carbon dioxide, helium, hydrogen, nitrogen, or mixtures thereof, through the fermentor culture or through an external stripping column to form an enriched stripping gas. Gas stripping to remove 1-butanol from an ABE fermentation has been exemplified by Ezeji, T., et al (U.S. Patent Application No. 2005/0089979, paragraphs 16 through 84). According to U.S. 2005/0089979, a stripping gas (carbon dioxide and hydrogen) was fed into a fermentor via a sparger. The flow rate of the stripping gas through the fermentor was controlled to give the desired level of solvent removal. The flow rate of the stripping gas is dependent on such factors as configuration of the system, cell concentration and solvent concentration in the fermentor. An enriched stripping gas comprising 1-butanol and water will be recovered from this process, and this stream can be further treated by distillation to produce a dry 1-butanol stream that can be used as the reactant of the present invention.
Using adsorption, organic compounds of interest are removed from dilute aqueous solutions by selective sorption of the organic compound by a sorbant, such as a resin. Feldman, J. in U.S. Pat. No. 4,450,294 (Column 3, line 45 through Column 9, line 40 (Example 6)) describes the recovery of an oxygenated organic compound from a dilute aqueous solution with a cross-linked polyvinylpyridine resin or nuclear substituted derivative thereof. Suitable oxygenated organic compounds included ethanol, acetone, acetic acid, butyric acid, n-propanol and n-butanol. The adsorbed compound was desorbed using a hot inert gas such as carbon dioxide. An aqueous stream comprising desorbed 1-butanol can be recovered from this process, and this stream can be further treated by distillation to produce a dry 1-butanol stream that can be used as the reactant of the present invention.
Liquid-liquid extraction is a mass transfer operation in which a liquid solution (the feed) is contacted with an immiscible or nearly immiscible liquid (solvent) that exhibits preferential affinity or selectivity towards one or more of the components in the feed, allowing selective separation of said one or more components from the feed. The solvent comprising the one or more feed components can then be separated, if necessary, from the components by standard techniques, such as distillation or evaporation. One example of the use of liquid-liquid extraction for the separation of butyric acid and butanol from microbial fermentation broth has been described by Cenedella, R. J. in U.S. Pat. No. 4,628,116 (Column 2, line 28 through Column 8, line 57). According to U.S. Pat. No. 4,628,116, fermentation broth containing butyric acid and/or butanol was acidified to a pH from about 4 to about 3.5, and the acidified fermentation broth was then introduced into the bottom of a series of extraction columns containing vinyl bromide as the solvent. The aqueous fermentation broth, being less dense than the vinyl bromide, floated to the top of the column and was drawn off. Any butyric acid and/or butanol present in the fermentation broth was extracted into the vinyl bromide in the column. The column was then drawn down, the vinyl bromide was evaporated, resulting in purified butyric acid and/or butanol.
Other solvent systems for liquid-liquid extraction, such as decanol, have been described by Roffler, S. R., et al. (Bioprocess Eng. (1987) 1:1-12) and Taya, M., et al (J. Ferment. Technol. (1985) 63:181). In these systems, two phases were formed after the extraction: an upper less dense phase comprising decanol, 1-butanol and water, and a more dense phase comprising mainly decanol and water. Aqueous 1-butanol was recovered from the less dense phase by distillation.
These processes are believed to produce aqueous 1-butanol that can be further treated by distillation to produce a dry 1-butanol stream that can be used as the reactant of the present invention.
The dry 1-butanol stream as obtained by any of the above methods can be the reactant for the process of the present invention. The reaction to form at least one dibutyl ether is performed at a temperature of from about 50 degrees Centigrade to about 450 degrees Centigrade. In a more specific embodiment, the temperature is from about 100 degrees Centigrade to about 250 degrees Centigrade.
The reaction can be carried out under an inert atmosphere at a 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 reaction can be carried out in liquid or vapor phase and can be run in either batch or continuous mode as described, for example, in H. Scott Fogler, (Elements of Chemical Reaction Engineering, 2nd Edition, (1992) Prentice-Hall Inc, CA).
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, 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, 2nd 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, 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, 7th 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 additive.
The present process and certain embodiments for accomplishing it are shown in greater detail in the Drawing figures.
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In the following examples, “C” is degrees Centigrade, “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, Mass.); CBV-3020E was obtained from PQ Corporation (Berwyn, Pa.); Sulfated Zirconia was obtained from Engelhard Corporation (Iselin, N.J.); 13% Nafion®/SiO2 can be obtained from Engelhard; and H-Mordenite can be obtained from Zeolyst Intl. (Valley Forge, Pa.).
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, Calif.], 25 m×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, Calif.)], 30 m×0.2 5 mm, 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.
The reactions were carried out for 2 hours at 6.9 MPa of N2.
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 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).
This application claims priority under 35 U.S.C. §119 from U.S. Provisional Application Ser. No. 60/814,141 (filed Jun. 16, 2006), the disclosure of which is incorporated by reference herein for all purposes as if fully set forth.
| Number | Date | Country | |
|---|---|---|---|
| 60814141 | Jun 2006 | US |
