Method for recovering amyl alcohol

Abstract

A method is provided for recovering an amyl alcohol composition containing 1-pentanol, 2-methyl-1-butanol, and 3-methyl-1-butanol from a fusel oil-containing extract from an associated ethanol distillation process, directly and without using decantation to concentrate the fusel alcohol in the fusel oil-containing extract.

Description

Technical Field

[0001] The present invention relates to the treatment of fusel oil from ethanol production by fermentation.

Background Art

[0002] The production of fusel oil is a natural and common phenomenon in the fermentation of sugars by Saccharomyces cerevisiae for ethanol production. However, fusel compounds pose a significant risk to ethanol yield. In this regard, both ethanol and fusel compounds are toxic to yeast growth and fermentation, but fusel compounds are 10 - 15 times more toxic to yeast than ethanol and, if not properly managed, can become part of the process water and risk recycling back to the front end of the plant. There have been several reported instances where fermenters have completely stopped ethanol production due to fusel oil.

[0003] Fusel compounds have conventionally been removed from ethanol plants using a rectifier distillation column, which increases capital, energy, and operating costs. By adjusting the pressure, flow, and operating temperature in the rectification column, fusel compounds are removed from ethanol via extraction positions on the side of the column and a fusel extraction pump.

[0004] This fusel oil-containing extract, and the ethanol fermentation by-product collectively known as "fusel oil" or equivalently "fusel alcohol," primarily contains several 3, 4, and 5-carbon alcohols, but also includes volatile organic acids, aldehydes, ketones, and fatty acids and esters of larger molecular weight. Apart from the need to remove them from the ethanol production process for the integrity of fermentation, fusel alcohols have economic or market value individually and / or collectively for applications in solvents, flavorings and fragrances, lubricants, adhesives and plasticizers, or for producing these; however, further purification and recovery of fusel alcohols from ethanol production has not been economically viable to date.

[0005] In this regard, conventional approaches to recovering fusel alcohol from ethanol distillation processes involve the use of one or more stages of decantation of the fusel oil extract, thereby adding a large amount of water to induce phase separation, resulting in a lower-density upper phase rich in fusel alcohol. The main problem with this approach is that the water-rich phase contains a significant amount of ethanol, which must be returned to the ethanol distillation process for recovery. Furthermore, the large amount of water added creates a significant energy burden on the process at a considerable additional cost, and the formation of an azeotropic mixture of water and some fusel alcohol further complicates any effort to recover fusel alcohol by continuous distillation. Fractional distillation to recover fusel alcohol beyond the azeotropic limit is feasible but costly. [Overview of the project] [Means for solving the problem]

[0006] In one embodiment, the present invention relates to a method for recovering fusel alcohol from an associated ethanol distillation process that produces a fusel oil-containing extract without using decantation, which has associated costs and disadvantages.

[0007] In another embodiment, the present invention relates to a method for recovering fusel alcohol from an associated ethanol distillation process that produces a fusel oil-containing extract without using decantation, thereby concentrating the fusel alcohol from the fusel oil-containing extract, and then further purifying the recovered fusel alcohol to recover a fusel alcohol product that is rich in at least one of the constituent fusel alcohols contained in the fusel oil-containing extract, compared to the fusel alcohol recovered from the fusel alcohol-containing extract and the fusel alcohol-containing extract.

[0008] More specifically, according to this second embodiment, a method is provided for recovering an amyl alcohol composition containing 1-pentanol, 2-methyl-1-butanol, and 3-methyl-1-butanol from a fusel oil-containing extract from an associated ethanol distillation process, wherein at least fusel alcohol is evaporated from the fusel oil-containing extract to produce a fusel alcohol-containing vapor composition, the fusel alcohol-containing vapor composition is then brought into contact with a gas-permeable membrane from which water is removed to form a dehydrated fusel alcohol-containing vapor composition, the dehydrated fusel alcohol-containing vapor composition can be economically distilled to provide a distillation fraction rich in an amyl alcohol composition containing 1-pentanol, 2-methyl-1-butanol, and 3-methyl-1-butanol.

[0009] In a particular embodiment, a portion of the water previously removed from the fusel oil-containing extract by decantation is removed by a vapor-liquid separation means (e.g., a stripping column or distillation column) also used to form and deliver the fusel alcohol-containing vapor composition, and any additional water is sufficiently removed by the use of a gas-permeable membrane or a series of such membranes to provide a dehydrated fusel alcohol-containing vapor composition, which lies on the less water side of the distillation boundary of the ternary phase diagram of water, ethanol, and amyl alcohol systems (Figure 1), and as a result, a distillation fraction rich in an amyl alcohol composition containing 1-pentanol, 2-methyl-1-butanol, and 3-methyl-1-butanol can be obtained by simple distillation.

[0010] In a particular other embodiment, sufficient water is removed from the fusel alcohol-containing vapor composition by one or more gas-permeable membranes to provide a dehydrated fusel alcohol-containing vapor composition which lies on the less water side of the distillation boundary of the water, ethanol, and amyl alcohol system ternary phase diagram, and this composition is distilled again to provide a distillation fraction rich in an amyl alcohol composition containing 1-pentanol, 2-methyl-1-butanol, and 3-methyl-1-butanol.

[0011] These and other aspects, embodiments, and related advantages will become apparent from the following detailed description. [Brief explanation of the drawing]

[0012] [Figure 1] This is a ternary phase diagram for the distillation of mixtures of water, ethanol, and 3-methyl-1-butanol (3M1B) in various proportions. [Figure 2] This is a schematic diagram of a method for recovering an amyl alcohol composition in an illustrative embodiment. [Modes for carrying out the invention]

[0013] All patent and non-patent literature disclosures referenced herein are incorporated herein by reference in their entirety.

[0014] As used herein, unless otherwise explicitly indicated by the context, the singular forms “a,” “an,” and “the” include multiple referents. The terms “contain” and their derivatives as used herein are similarly intended to be non-restrictive terms that identify the presence of a described feature, element, component, group, integer, and / or process, but do not exclude the presence of other undescribed features, elements, components, groups, integers, and / or processes. This understanding also applies to similarly meaning words such as “contain,” “have,” and their derivatives. The terms “become” and their derivatives as used herein are intended to be restrictive terms that identify the presence of a described feature, element, component, group, integer, and / or process, but exclude the presence of other undescribed features, elements, components, groups, integers, and / or processes. As used herein, the term “essentially derived from” is intended to identify the presence of features, elements, components, groups, integers, and / or processes described, as well as those that do not substantially affect the basic and novel features of the features, elements, components, groups, integers, and / or processes described.

[0015] As used herein, terms of degree such as “substantially,” “about,” and “approximately” mean a reasonable amount of deviation of the modified term (beyond the degree of deviation understood by the precision (significant figures) in which the quantity is expressed) such that the final result is not substantially altered. These terms of degree should be interpreted as including a deviation of at least plus or minus 5 percent from the stated value, provided that the deviation does not negate the meaning of the modified term.

[0016] As used herein, the term “biologically derived” is interchangeable with “bio-based” or “bio-derived,” and “biologically derived,” “bio-based,” and “bio-derived” are all understood to refer to any chemical compound, including monomers and polymers, obtained in whole or in any part from any renewable resource, including but not limited to plant, animal, marine, or forest material. The “bio-based content” of any such compound is understood to be the percentage of carbon content of the compound determined by ASTM method D6866 to be obtained from or derived from such renewable resource. In this context, ASTM method D6866, similar to radiocarbon dating, compares how much decaying carbon isotope remains in the sample to how much would be present in the same sample if it were made whole from recently grown material. The sample is burned in a quartz sample tube, and the gaseous combustion products are transferred to a borosilicate sealed tube. In one method, liquid scintillation is used to count the relative amounts of carbon isotopes in carbon dioxide in the gaseous combustion products. In the second method, accelerator mass spectrometry is used to count (14C) and measure (13C / 12C) the 13C / 12C and 14C / 12C isotope ratios. Zero percent 14C indicates the complete absence of 14C atoms in the material and therefore indicates a fossil (e.g., petroleum-based) carbon source. After correcting for the injection of 14C into the atmosphere by bombs since 1950, 100 percent 14C indicates a modern carbon source. Partly because isotope fractionation resulting from physiological processes, such as carbon dioxide transport in plants during photosynthesis, leads to specific isotope ratios in natural or bio-based compounds, ASTM D6866 effectively distinguishes bio-based materials from petroleum-derived materials. Conversely, the 13C / 12C carbon isotope ratios of petroleum and petroleum-derived products differ from those in natural or bio-based compounds due to different chemical processes and isotope fractionation during petroleum formation. In addition, the radioactive decay of unstable 14C carbon isotopes initially results in different isotopic ratios in bio-based products compared to petroleum-based products.

[0017] The present invention can be more fully understood by describing several embodiments in further detail. These embodiments should not be considered to limit the scope and breadth of the invention to the extent that they are more specifically defined in the claims set forth below, but they illustrate the principles of the invention and demonstrate various ways and options regarding how those principles can be applied in carrying out the invention.

[0018] Therefore, unless otherwise indicated, any definitions or embodiments described in this or other sections are intended to be applicable to all embodiments and aspects of the subject matter described herein, provided that they are suitable according to the understanding of those skilled in the art.

[0019] Now, looking to Figure 1, a ternary phase diagram is shown relating to the distillation of various combinations of water, ethanol, and 3-methyl-1-butanol, one of the amyl alcohols of interest for the purposes of the present invention. As those skilled in the art will recognize, mixtures with less water on the left side of the illustrated distillation boundary can be distilled more readily and easily to provide a desired distillation fraction rich in amyl alcohols, and therefore, in a preferred embodiment, the method of the present invention attempts to obtain such a mixture from a fusel oil-containing extract by either a) a combination of removing a portion of the water when forming a fusel alcohol-containing vapor composition directly from the fusel oil-containing extract and then passing the fusel alcohol-containing composition through one or more gas-permeable membranes, the gas-permeable membranes removing the remaining water as needed to obtain a further dehydrated composition on the left side of the distillation boundary, or b) forming a fusel alcohol-containing vapor composition and removing all the water as needed by one or more gas-permeable membranes to obtain a composition on the left side of the distillation boundary.

[0020] Turning to the examination in Figure 2, an illustrative embodiment 10 of the method according to the present invention is schematically shown, according to the first of the approaches described above, thereby purifying a fusel oil-containing extract from the distillation section of a production plant for producing ethanol by fermentation of sugars, without requiring the use of any decantation, to provide an amyl alcohol composition comprising 1-pentanol, 2-methyl-1-butanol, and 3-methyl-1-butanol.

[0021] The fusel oil-containing extract 12 enters a single-stage evaporator 14, where a substantial portion of the water contained in the fusel oil-containing extract is separated along with some ethanol, which can be recycled to the distillation section of the associated ethanol production plant to recover the ethanol in the liquid fraction 16. The dewatered fusel alcohol-containing vapor composition 18 is then brought into contact with a gas-permeable membrane or a series of such membranes 20, which removes any additional water in the flow 22 from the dewatered fusel alcohol-containing vapor composition to form a further dewatered fusel alcohol-containing vapor composition 24, in which, preferably, water is less than about 25% by weight of the composition.

[0022] For our purposes, preferred membranes 20 would be zeolite film membranes on porous ceramic supports, particularly zeolite film membranes on porous tubular ceramic supports in modular bundles of tubular membranes in tube-and-shell structures. Representative commercially available examples are currently sold for use in ethanol dehydration by several manufacturers, for example, Mitsubishi Chemical Engineering Corporation, Tokyo, Japan, and Hitachi Zosen Corporation, Osaka, Japan. Particularly preferred are the CHA-, MOR-, and A-type porous alumina-supported tubular zeolite membranes from Hitachi Zosen Corporation. Other non-zeolite membranes, such as hollow fiber polymer membranes sold by Whitefox Technologies, London, UK, may also be useful, to the extent that they are robust enough to handle the vapor phase dehydration of the water-free fusel alcohol-containing vapor composition 18, under conditions required to avoid condensation throughout the process due to heat loss and changes in water content of the composition 18 as it passes across and along the membrane 20 in cross-flow, counter-flow, or parallel flow and is gradually dehydrated. As a result, some degree of superheating of the water-free fusel alcohol-containing vapor composition 18 will be required, and subject to this condition, the process 10 can accommodate a variety of operating pressures and temperatures that match the selection of a particular membrane or combination of membranes 20. In this regard, combinations of the same or different membranes 20 may be used in series, for example, MOR and A-type ceramic-supported zeolite membranes, while operating under the same or different conditions, or combinations of the same or different membranes 20 may be used in parallel modules to facilitate maintenance. The selection of specific configurations, membrane materials, and appropriate operating conditions will be well within the capabilities of those skilled in the art.

[0023] Next, the further dehydrated fusel alcohol-containing vapor composition 24 is condensed and fed to a first distillation column 26, producing a top stream 28 composed of residual water and more volatile alcohols such as C2-C4 alcohols. In a second distillation column 32, the bottom stream 30 composed of C5 alcohols and heavier, higher-temperature-distilled components of the fusel alcohol-containing vapor composition 24 is further distilled. The second distillation column provides a distillation fraction rich in an amyl alcohol composition 34 containing 1-pentanol, 2-methyl-1-butanol, and 3-methyl-1-butanol. On the other hand, in the bottom stream 36, heavier residual compounds such as fatty acid ethyl esters, phenylethyl alcohol, and ethyl phenylacetate exit the second distillation column 32.

[0024] Next, in certain embodiments, the amyl alcohol composition 34 may be passed through a further process (not shown in FIG. 2) and contacted with a suitable adsorbent, such as activated carbon, to remove any trace impurities that may be present in the composition 34 and that may be harmful or unwanted in the intended use or application of the amyl alcohol composition 34, or those components that one of ordinary skill in the art may further desire to isolate and purify.

[0025] The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are illustrative only in all respects and should be considered non-limiting. Accordingly, the scope of the present invention is indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Explanation of Reference Numerals

[0026] 10 Embodiment 10 Process 12 Fusel Oil-Containing Extract 14 Single-Stage Evaporator 16 Liquid Fraction 18 Fusel Alcohol-Containing Vapor Composition with Water Removed 20 Gas permeable membrane or a series of such membranes 20 membrane 20. Specific membranes or combinations of membranes 20 Combinations of the same or different membranes 22 Flow 24 Dehydrated fusel alcohol-containing vapor composition 26. First distillation column 28 Tower top stream 30 Bottom flow 32 Second distillation column 34 Amyl alcohol composition 36 Bottom flow

Claims

1. A method for recovering fusel alcohol from a fusel oil-containing extract obtained from the distillation of an ethanol fermentation product mixture, To produce a fusel alcohol-containing vapor composition by evaporating at least fusel alcohol from a fusel oil-containing extract, Optionally, during the evaporation process, at least some water may be removed from the fusel oil-containing extract. The process involves contacting a fusel alcohol-containing vapor composition with one or more gas-permeable membranes to remove water from the fusel alcohol-containing vapor composition. Includes, One or more gas-permeable membranes alone, or one or more membranes working in combination with any removal of water in the evaporation process, result in a well-dehydrated fusel alcohol-containing composition where, in the ternary phase diagram for the distillation of various ethanol, water, and amyl alcohol mixtures, the water is on the left side of the distillation boundary. method.

2. The method according to claim 1, wherein a fusel alcohol-containing composition containing less than 25% by weight of water is realized by one or more gas-permeable membranes alone, or in combination with the removal of water in an evaporation step.

3. The method according to claim 2, further comprising distilling a fusel alcohol-containing composition to provide a distillation fraction rich in an amyl alcohol composition containing 1-pentanol, 2-methyl-1-butanol, and 3-methyl-1-butanol.

4. The method according to claim 3, further comprising contacting a distillation fraction rich in an amyl alcohol composition with a carbon adsorbent.

5. A method for recovering amyl alcohol from fusel oil-containing extracts from the distillation of an ethanol fermentation product mixture, To obtain a fusel oil-containing extract, In order to evaporate at least fusel alcohol from the fusel oil-containing extract and produce a fusel alcohol-containing vapor composition, the fusel oil-containing extract is directly supplied to a vapor-liquid separation means, The process involves contacting a fusel alcohol-containing vapor composition with one or more gas-permeable membranes to remove water from the fusel alcohol-containing vapor composition and form a dehydrated fusel alcohol-containing vapor composition. The fractional distillation of the dehydrated fusel alcohol-containing vapor composition provides a distillate rich in an amyl alcohol composition containing 1-pentanol, 2-methyl-1-butanol, and 3-methyl-1-butanol. A method that includes this.

6. The method according to claim 5, further comprising contacting a distillation fraction rich in an amyl alcohol composition with a carbon adsorbent.

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