Process for recovering pentanol

Abstract

A process is provided for the direct recovery of a pentanol composition comprising 1-pentanol, 2-methyl-1-butanol, and 3-methyl-1-butanol from a fusel-containing oil extract from an associated ethanol distillation apparatus without the use of decantation to concentrate fusel in the fusel-containing oil extract.

Description

Field of the invention

[0001] This invention relates to the processing of fusel oils from which ethanol is produced by fermentation. BACKGROUND

[0002] Fusel oil is produced by brewer's yeast ( Saccharomyces cerevisiae Fermentation is the natural and normal part of sugars used in ethanol production. However, fusel oils pose a significant risk to ethanol yield. In this respect, both ethanol and fusel oils are toxic to yeast growth and fermentation, but fusel oils are 10 to 15 times more toxic to yeast than ethanol, and if not properly managed, fusel oils can become part of the process water and be recycled back to the front end of the plant. Numerous instances have been reported where fermenters have completely ceased ethanol production due to fusel oil.

[0003] Fluidized alcohols are typically removed from ethanol plants using distillation columns, which increases capital, energy, and operating costs. Fluidized alcohols are removed from ethanol via extraction sections on the column side and extraction pumps by adjusting the pressure, flow rate, and operating temperature within the distillation column.

[0004] This fusel oil-containing draw—and the ethanol fermentation byproducts collectively referred to as "fusel oil" or equivalently "fusel alcohols"—primarily contains many tri-, tetra-, and pent-ols, but also includes volatile organic acids, aldehydes, ketones, and higher molecular weight fatty acids and esters. Independent of the need to remove these fusel alcohols from the ethanol production process for the sake of fermentation health, fusel alcohols, individually and / or collectively, have economic or market value for use in or for the production of solvents, flavorings and fragrances, lubricants, adhesives, and plasticizers; however, further refining and recovery from ethanol production has so far been economically infeasible.

[0005] Conventional methods for recovering fusel oils from ethanol distillation trains involve one or more stages of decantation of the fusel oil extract, thereby adding a large amount of water to induce phase separation, in which the upper, lower-density phase is rich in fusel oils. A major problem with this method is that the water-rich phase contains a significant amount of ethanol, which must be returned to the ethanol distillation train for recovery. The large amount of water added also generates a large energy load in the process at a significantly increased cost, and the formation of azeotropes between water and certain fusel oils further complicates any effort to recover fusel oils via continuous distillation. Fractional distillation to recover fusel oils exceeding the azeotropic limit is feasible, but costly. SUMMARY

[0006] In one aspect, the present invention relates to a method for recovering fusel alcohols from a related ethanol distillation apparatus producing a fusel oil-containing extract without the use of decantation with its associated costs and drawbacks.

[0007] In another aspect, the present invention relates to a method for recovering fusel alcohols from a related ethanol distillation apparatus producing a fusel oil-containing extract without the use of decantation to concentrate the fusel alcohols from the fusel oil-containing extract; and for then further refining the recovered fusel alcohols to recover a fusel alcohol product that is enriched in at least one constituent fusel alcohol contained in the fusel oil-containing extract compared to the recovered fusel alcohols from the fusel oil-containing extract.

[0008] More particularly, according to this second aspect, there is provided a method for recovering a pentanol composition comprising 1-pentanol, 2-methyl-1-butanol and 3-methyl-1-butanol from a fusel oil-containing extract from a related ethanol distillation apparatus, wherein at least the fusel alcohols from within the fusel oil-containing extract are vaporized to produce a fusel alcohol-containing vapor composition, which is then contacted with a gas-permeable membrane to remove water from the fusel alcohol-containing vapor composition and form a dehydrated fusel alcohol-containing vapor composition that can be economically distilled to provide a distillate fraction enriched in a pentanol composition comprising 1-pentanol, 2-methyl-1-butanol and 3-methyl-1-butanol.

[0009] In certain embodiments, the portion of water that has heretofore been removed from the fusel oil-containing extract by decantation is removed by a gas-liquid separation device (e.g., a stripping column or distillation column) that is also used to form and deliver the fusel alcohol-containing vapor composition, and sufficient additional water is removed by use of a gas-permeable membrane or series of such membranes to provide a dehydrated fusel alcohol-containing vapor composition that lies on the low water side of the distillation boundary of the ternary phase diagram of the water, ethanol and pentanol system Figure 1 ) and that can thus be subjected to simple distillation to provide a distillate fraction enriched in a pentanol composition comprising 1-pentanol, 2-methyl-1-butanol and 3-methyl-1-butanol.

[0010] In certain other embodiments, 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 that lies on the low water side of the distillation boundary of the ternary phase diagram of the water, ethanol and pentanol system, and this composition is again distilled to provide a distillate fraction enriched in a pentanol composition comprising 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 detailed description below. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a ternary phase diagram of distilling mixtures of water, ethanol, and 3-methyl-1-butanol in different proportions.

[0013] Figure 2 is a schematic of a process for recovering a pentanol composition in an illustrative embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0014] The disclosures of all patent documents and non-patent literature cited herein are hereby incorporated by reference in their entirety.

[0015] As used in this application, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. As used herein, the term "comprising" and its derivatives are intended to be open-ended terms that specify the presence of the stated features, elements, components, groups, integers, and / or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers, and / or steps. The use of the terms "comprising" and "including," as well as other forms such as "comprises," "includes," and "including the therein are not limiting. As used herein, the term "consisting of" and its derivatives are intended to be closed terms that specify the presence of the stated features, elements, components, groups, integers, and / or steps, but exclude the presence of other unstated features, elements, components, groups, integers, and / or steps. As used herein, the term "consisting essentially of" is intended to specify the presence of the stated features, elements, components, groups, integers, and / or steps as well as those that do not materially affect the basic and novel characteristics and properties of the stated features, elements, components, groups, integers, and / or steps.

[0016] As used herein, terms of degree such as "substantially," "about," and "approximately" mean an amount that is reasonable given the precision of the expression being qualified (significant figures), such that the end result is not significantly changed. These terms of degree should be construed as encompassing less than or more than the recited value as long as the end result is not significantly changed.

[0017] As used herein, the terms "biologically-derived" are used interchangeably with "biobased" or "bioderived," and "biologically-derived," "biobased," and "bioderived" are all understood to refer to any compound, including monomers and polymers, obtained in whole or in part from any renewable resource, including but not limited to a plant, animal, marine material, or forestry material. The "biobased content" of any such compound is understood to be the percentage of the carbon content of the compound that is obtained or derived from such renewable resources, as determined by ASTM Method D6866. In this regard, ASTM Method D6866, similar to radiocarbon dating, compares how much decaying carbon isotopes remain in a sample to how many would remain in the same sample if it were made entirely from newly grown material. The sample is combusted in a quartz sample tube and the gaseous combustion products are transferred to a borosilicate break-seal tube. In one method, liquid scintillation is used to calculate the relative amount of carbon isotopes in the carbon dioxide in these gaseous combustion products. In a second method, accelerator mass spectrometry is used to calculate (14C) and measure (13C / 12C) the 13C / 12C and 14C / 12C isotope ratios. Zero percent 14C indicates that there are no 14C atoms in the material, thus indicating a fossil (e.g., petroleum-based) carbon source. One hundred percent 14C indicates a modern carbon source, after correction for the post-1950 atmospheric injection of 14C. ASTM D6866 effectively distinguishes biobased materials from petroleum-derived materials, in part because isotopic fractionation due to physiological processes, such as carbon dioxide transport within plants during photosynthesis, produces specific isotope ratios in natural or biobased compounds. In contrast, the 13C / 12C carbon isotope ratio of petroleum and petroleum-derived products is different from the isotope ratio in natural or biologically-derived compounds, due to different chemical processes and isotopic fractionation during petroleum production. In addition, the radioactive decay of the unstable 14C carbon radioisotope first produces a different isotope ratio in biobased products compared to petroleum products.

[0018] The present application can be more completely understood in consideration of the following detailed description in connection with the accompanying drawings, in which certain embodiments of the application are illustrated. These embodiments are not intended to limit the scope of the application, but rather are meant to illustrate the principles of the application and to provide options for how the principles of the application can be applied in practice.

[0019] Accordingly, unless otherwise indicated, any definition or embodiment described in this section or other sections is intended to be applicable to all embodiments and aspects of the subject matter described herein as would be understood by one of ordinary skill in the art.

[0020] Turning now to Figure 1 , a ternary phase diagram is shown for the distillation of various combinations of water, ethanol, and 3-methyl-1-butanol, one of the pentanols of interest for the purposes of the present invention. As will be understood by those skilled in the art, mixtures located on the left side of the distillation boundary, on the low water side, can be distilled more rapidly and easily to provide the desired distillate fraction enriched in pentanols, and thus in preferred embodiments the process of the present invention seeks to obtain such mixtures from the fusel oil extract, essentially by a) a combination of the following steps: removing a portion of the water forming part of the fusel-containing vapor composition directly from the fusel oil extract, and then contacting the fusel-containing composition with one or more gas-permeable membranes that remove the remaining portion of the water required to obtain the further dehydrated composition located on the left side of the distillation boundary; or b) forming the fusel-containing vapor composition and removing all of the water required to obtain the composition located on the left side of the distillation boundary through one or more gas-permeable membranes.

[0021] Turning now to consideration Figure 2 , an exemplary embodiment 10 of the process according to the present invention according to the first of the foregoing processes is schematically shown, in which a fusel oil extract from a distillation section of a production plant for the production of ethanol by fermentation of a sugar is refined to provide a pentanol composition comprising 1-pentanol, 2-methyl-1-butanol, and 3-methyl-1-butanol, without the need to use any decantation.

[0022] The fusel oil extract 12 enters a single-stage evaporator 14 to separate a major portion of the water contained in the fusel oil extract, together with some ethanol, into a liquid fraction 16 that can be recycled to the distillation section of the relevant ethanol production plant to recover the ethanol therein from a water-depleted fusel-containing vapor composition 18, which is contacted with a gas-permeable membrane or series of such membranes 20 that removes (or remove) additional water in a stream 22 from the water-depleted fusel-containing vapor composition to form a further dehydrated fusel-containing vapor composition 24, in which the water is preferably less than about 25% by weight of the composition.

[0023] For our purposes, the preferred membrane 20 will be a zeolite membrane on a porous ceramic support, particularly a porous tubular ceramic support in a modular bundle of such tubular membranes in a tube-and-shell configuration. Commercial samples are currently sold by a number of manufacturers for ethanol dehydration, such as by Mitsubishi Chemical Engineering Corporation, Tokyo, Japan and Hitachi Zosen Corporation, Osaka, Japan. Particularly preferred are the CHA-type, MOR-type and A-type porous alumina-supported tubular zeolite membranes from Hitachi Zosen. Other non-zeolite membranes, such as the hollow fiber polymeric membranes sold by Whitefox Technologies, London, England, can also be useful, provided that these membranes are sufficiently robust to accommodate the vapor phase dehydration of the water-lean, fusel vapor-containing composition 18 under conditions required to avoid complete condensation due to heat loss and water content changes of the composition 18 as it passes through and along the membrane 20 in cross-flow, counter-flow or co-current flow and is progressively dehydrated. Thus, some degree of superheat will be required for the water-lean, fusel vapor-containing composition 18, but subject to this limitation, the process 10 is suitable for a range of operating pressures and operating temperatures consistent with the selection of a particular membrane or combination of membranes 20. In this regard, combinations of the same or different membranes 20 can be used in series, operating under the same or different conditions— e.g., MOR-type and A-type ceramic-supported zeolite membranes in series— or combinations of the same or different membranes 20 can be used in parallel modules for ease of maintenance. The selection of a particular configuration, membrane material and appropriate operating conditions will be well within the capabilities of one skilled in the art.

[0024] The further dehydrated fusel vapor-containing composition 24 is then condensed and supplied to a first distillation column 26, producing an overhead stream 28 comprising any residual water and higher volatility alcohols such as C2-C4alcohols, and a bottoms stream 30 comprising C5alcohols and the heavier, higher boiling distillation components of the fusel vapor-containing composition 24, which is further distilled in a second distillation column 32. The second distillation column provides a distillate fraction enriched in a pentanol composition 34 comprising 1-pentanol, 2-methyl-l-butanol and 3-methyl-l-butanol, while residual heavier compounds such as fatty acid ethyl esters, phenethyl alcohol and phenethyl acetate exit the second distillation column 32 in a bottoms stream 36.

[0025] In certain embodiments, the pentanol composition 34 can then be subjected to additional steps to recover the 1-pentanol, 2-methyl-l-butanol and 3-methyl-l-butanol in a purified form. For example, the pentanol composition 34 can be subjected to a separation step to separate the 1-pentanol, 2-methyl-l-butanol and 3-methyl-l-butanol from the other components of the pentanol composition 34. The separation step can be a distillation step, a liquid-liquid extraction step, a crystallization step, a chromatography step, a membrane separation step, or a combination of two or more of these steps. Figure 2The pentanol composition 34 or any component thereof can be further separated and purified if desired by those skilled in the art, as can be necessary or desirable for the intended application or use of the pentanol composition 34 or any component thereof, by contacting the composition 34 (not shown) with a suitable adsorbent, such as activated carbon, to remove any trace impurities that can be present in the composition 34 and that would be deleterious or undesirable in the intended application or use of the pentanol composition 34 or any component thereof.

[0026] The application can take other specific forms without departing from the spirit or essential characteristics thereof. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the application is, therefore, 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.

Claims

1. A method for recovering fusel alcohols from a fusel oil extract from distillation of an ethanol fermentation product mixture, comprising: evaporating at least fusel alcohols from within the fusel oil extract to produce a fusel alcohol-containing vapor composition; optionally, simultaneously removing at least some water from the fusel oil extract in the evaporating step; and contacting the fusel alcohol-containing vapor composition with one or more gas-permeable membranes to remove water from the fusel alcohol-containing vapor composition, thereby, by the one or more gas-permeable membranes alone or by the one or more membranes in combination with the optional removal of water in the evaporating step, producing a substantially dehydrated fusel alcohol-containing composition that lies on the left, low water side of a distillation boundary of a ternary phase diagram for distillation of a mixture of ethanol, water, and amyl alcohol.

2. The method of claim 1, wherein the fusel alcohol-containing composition comprising less than about 25% water by weight is obtained by the one or more gas-permeable membranes alone or by the one or more gas-permeable membranes in combination with the removal of water in the evaporating step.

3. The method of claim 2, further comprising distilling the fusel alcohol-containing composition to provide a distillate fraction enriched in an amyl alcohol composition comprising 1-pentanol, 2-methyl-l-butanol, and 3-methyl-l-butanol.

4. The method of claim 3, further comprising contacting the distillate fraction enriched in the amyl alcohol composition with a carbon adsorbent.

5. A method for recovering amyl alcohols from a fusel oil extract from distillation of an ethanol fermentation product mixture, comprising: obtaining the fusel oil extract; supplying the fusel oil extract directly to a gas-liquid separation device for evaporating at least fusel alcohols from within the fusel oil extract and producing a fusel alcohol-containing vapor composition; contacting the fusel alcohol-containing vapor composition with one or more gas-permeable membranes to remove water from the fusel alcohol-containing vapor composition to form a dehydrated fusel alcohol-containing vapor composition; and fractionating the dehydrated fusel alcohol-containing vapor composition to provide a distillate fraction enriched in an amyl alcohol composition comprising 1-pentanol, 2-methyl-l-butanol, and 3-methyl-l-butanol.

6. The method of claim 5, further comprising contacting the distillate fraction enriched in the amyl alcohol composition with a carbon adsorbent. ​

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