REFINING PROCESSES FOR A RENEWABLE OIL

Abstract

The invention relates generally to methods of refining a renewable oil, such as a biofuel. In some embodiments, the invention relates to methods for the efficient removal of gums and waxes from a renewable oil.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is nonprovisional of, and claims the benefit of U.S. Patent Application No. 61/830,923 filed Jun. 4, 2013, the entire contents of which is incorporated herein by reference for all purposes.

FIELD OF THE INVENTION

[0002] The invention relates generally to methods of refining a renewable oil, such as a biofuel. In some embodiments, the invention relates to methods for the efficient removal of gums and waxes from a renewable oil.

BACKGROUND

[0003] Crude vegetable oils and other biofuels can contain waxes and gums that precipitate as solids under certain operating conditions, giving a cloudy appearance to the oil. While these waxes and gums can result from a variety of impurities in the oil, they are often the result of phosphorus-containing impurities in the oil. Such phosphorus-containing impurities can include phosphatides, such as hydratable phosphatides and non-hydratable phosphatides. These impurities can enter the oil from a variety of sources. These impurities can be present in the oil for a variety of reasons. In some instances, the impurities are present because of certain processing steps used in the initial processing of the oil. For example, such impurities can result from certain processing stops to remove free fatty acids from biodiesel or to remove free fatty acids from corn oil obtained from ethanol plants. The presence of these impurities in the oil can render the oil unusable as a fuel source, or, if usable, can limit its operating range. Therefore, it is desirable to remove such impurities from the renewable oil.

[0004] One can employ various means to remove these waxes and gums from the oil. Such techniques include water degumming, acid degumming, acid refining, dry degumming, enzymatic degumming, degumming by chelating agents, ultra-filtration and cavitation. Many of these process require washing of the oil, either as part of the process itself or to remove chemicals that are added to facilitate the process. Such washing can cause substantial loss of oil, thereby lowering the efficiency of the process and increasing the operating costs. In some cases, such as with enzymatic degumming, the materials are expensive, and add considerable costs to the process. Other processes require expensive equipment, which increase the capital expenditures involved in carrying out the process. Therefore, there is a need to continue to develop refining processes that can be carried out quickly with minimal oil loss, do not involve expensive reagents, and do not require expensive equipment.

SUMMARY OF THE INVENTION

[0005] In at least one aspect, the invention provides methods of reducing the cloud point of a renewable oil, the method comprising: providing a renewable of which comprises waxy impurities; cooling the renewable oil; adding a polymer to the cooled renewable oil; mixing the cooled renewable oil and the polymer to form an oil-polymer mixture, which comprises solidified impurities; and separating at least a portion of the solidified impurities from the oil-polymer mixture to form a refined renewable oil.

[0006] In another aspect, the invention provides methods of reducing the cloud point of a renewable oil, the method comprising: providing a renewable oil, wherein the renewable of comprises phosphorus-containing compounds, free fatty acids, or a combination thereof; cooling the renewable oil; adding a polymer to the cooled renewable oil; binding the polymer to the phosphorus-containing compounds, the free fatty acids, or both the phosphorus-containing compounds and the free fatty acids; and separating at least a portion of the polymer to form a refined renewable oil.

[0007] Other aspects and embodiments of the invention are described in further detail in the following sections.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The application includes the following figures. These figures depicts certain illustrative embodiments of various aspects of the invention. In some instances, the figures do not necessarily provide a proportional illustration of an actual embodiment of the invention, but may emphasize certain features for purposes of illustration. The figures are not intended to limit the scope of the claimed subject matter apart from an express indication to the contrary.

[0009] FIG. 1 depicts a flow diagram for a process for removing a waxy impurity from a renewable oil.

[0010] FIG. 2 depicts a flow diagram for a process hr removing a waxy impurity from a renewable oil

[0011] FIG. 3 depicts a flow diagram for a process of refining biodiesel.

DETAILED DESCRIPTION

[0012] The following description recites various aspects and embodiments of the present invention. No particular embodiment is intended to define the scope of the invention. Rather, the embodiments merely provide non-limiting examples various compositions, apparatuses, and methods that are at least included within the scope of the invention. The description is to be read from the perspective of one of ordinary skill in the art; therefore, information well known to the skilled artisan is not necessarily included.

Definitions

[0013] As used herein, the articles "a," "an," and "the" include plural referents, unless expressly and unequivocally disclaimed.

[0014] As used herein, the conjunction "or" does not imply a disjunctive set. Thus, the phrase "A or B is present" includes each of the following scenarios: (a) A is present and B is not present; (b) A is not present and B is present; and (c) A and B are both present. Thus, the term "or" does not imply an either/or situation, unless expressly indicated.

[0015] As used herein, the term "comprise," "comprises," or "comprising" implies an open set, such that other elements can be present in addition to those expressly recited.

[0016] Unless otherwise indicated all numbers expressing quantities of ingredients, reaction conditions, and so for used in the specification are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters sot forth in the following specification are approximations that can vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0017] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a stated range of "1 to 10" should be considered to include any and all subranges between (and inclusive of) the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more, e.g. 1 to 6.1 and ending with a maximum value of 10 or less, e.g., 5.5 to 10.

[0018] Other definitions are provided throughout the specification. When any term is not specifically defined, the term shall have the meaning that it would have to persons of ordinary skill in the field to which the inventions disclosed herein are directed.

Refining Processes

[0019] In at least one aspect, the invention provides methods of reducing the cloud point of a renewable oil, the method comprising: providing a renewable oil, which comprises waxy impurities; cooling the renewable oil; adding a polymer to the cooled renewable oil; mixing the cooled renewable oil and the polymer to form an oil-polymer mixture, which comprises solidified impurities; and separating at least a portion of the solidified impurities from the oil-polymer mixture to form a refined renewable oil.

[0020] In another aspect, the invention provides methods of reducing the cloud point of a renewable oil, the method comprising: providing a renewable oil, wherein the renewable oil comprises phosphorus-containing compounds, free fatty acids, or a combination thereof; cooling the renewable oil; adding a polymer to the cooled renewable oil; binding the polymer to the phosphorus-containing compounds, the free fatty acids, or both the phosphorus-containing compounds and the free fatly acids; and separating at least a portion of the polymer to form a refined renewable oil.

[0021] As used herein, the term "renewable oil" refers to any organic liquid having renewable source. Renewable oils can include fatty acid esters, such as those commonly used in biodiesel. Thus, in some embodiments, the renewable oil comprises fatty acid esters, such as methyl, ethyl, isopropyl, and propyl esters of certain fatty acids, such as saturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, and trans-fatty acids. Renewable oils can also include various triglycerides, such as those obtained from various animal or vegetable sources. The invention is not limited to any particular renewable source for the renewable oil, and can at least include one or more of the following: animal fats, including but not limited to tallow, lard, grease, chicken fat, and by-products of fish or shellfish processing; vegetable oils, including but not limited to rapeseed oil, soybean oil, corn oil, palm oil, jatropha oil, mustard oil, jojoba oil, flax oil, coconut oil, peanut oil, hemp oil, castor oil, and sunflower oil; waste vegetable oil; by-products of ethanol production; and sewage sludge. In some embodiments, the renewable oil comprises a vegetable oil, an animal oil, or a mixture thereof. In some embodiments, the renewable oil comprises a vegetable oil, such as corn oil. In some embodiments, the renewable oil comprises a crude renewable oil, such as renewable of that has not yet undergone any refining process. In some other embodiments, the renewable oil comprises a partially refined renewable oil, which has undergone one or more processing steps. In some embodiments, the renewable oil comprises crude corn oil. In some other embodiments, the renewable oil comprises partially refined corn oil. In some embodiments, the renewable oil comprises crude biodiesel. In some other embodiments, the renewable oil comprises a partially refined biodiesel.

[0022] As used herein, "cloud point" refers to the temperature at which solid crystals first appear in the oil when the oil is tested according to the procedure set forth in the ASTM D2500 specification, which is published by the American Society for Testing and Materials, West Conshohocken, Pa., USA. This method of measuring the cloud point if often referred to in the art as the "manual method."

[0023] The methods include providing a renewable oil. As used herein, the term "providing" is broadly defined, and can include the delivery of the renewable oil for the carrying out of the additional steps in the process.

[0024] The renewable oil can include certain impurities. In some embodiments, these impurities include waxy impurities. As used herein, the term "waxy impurities" refers to various waxes and gums that can be present in the renewable oil. In some instances, these substances can dissolve in the renewable oil, but tend to precipitate as the temperature of the renewable oil is lowered. The presence or quantity of such waxy impurities can be measured indirectly by the determining the cloud point of the renewable oil, as described above. In some embodiments, the waxy impurities include one or more phosphorus-containing compounds. Such compounds can come from a variety of sources. In some embodiments, the phosphorus-containing compounds can include certain phospholipids, or the byproducts thereof, which can occur naturally in most vegetable oils, and can be present to a lesser degree in certain animal fats. In some embodiments, the phosphorus-containing compounds can include residues or remnants of certain materials employed in an earlier processing step in the refining process. In some such embodiments, the phosphorus-containing compounds can result from the use of certain phosphorus-based soaps in the refining process. In some embodiments, the phosphorus-containing compounds include phosphatides, including hydratable phosphatides, non-hydratable phosphatides, or mixtures thereof.

[0025] In some embodiments, the renewable oil comprises one or more free fatty acids as an impurity. As used herein, the term "free fatty acids" refers to fatty acids in the free acid form, e.g., not as part of an ester. Such impurities can occur in biodiesel and in vegetable and animal oils. They can occur for a variety of reasons. For example, in sonic instances, free fatty acids can be generated as a by-product of certain trans-esterification processes. In other instances, the free fatty acids can be present in the oil as the result of degradation, e.g., natural degradation or degradation due to previous use or processing of the oil.

[0026] The methods include adjusting the temperature of the renewable oil. In some embodiments, the adjusting comprises cooling the renewable oil. The invention is not limited to any particular means of cooling the oil. Any suitable means of cooling the oil can be used, as are well known in the industry. The renewable oil is generally cooled to a temperature below standard room temperature, e.g., below 25° C. In some embodiments, the cooling comprises cooling the renewable oil to a temperature within 10° C., or within 7° C., or within 5° C., or within 3° C. of the cloud point of the renewable oil. In some such embodiments, the cooling comprises cooling the renewable oil to a temperature below the cloud point of the oil. In some other such embodiments, the cooling comprises cooling the renewable oil to a temperature above the cloud point of the oil. In some embodiments, the cooling comprises cooling the renewable oil to a temperature below 20° C., or below 15° C., or below 10° C., or below 7° C., or below 5° C., or below 3° C. or below 1° C. or below 0° C., or below -1° C., or below -3° C., or below -5° C. The degree of cooling can depend on various factors, including the composition of the renewable oil, the chemical makeup of any impurities, and the quantity of any impurities.

[0027] The methods include adding a polymer to the cooled renewable oil. The polymer can be added or introduced to the renewable oil by any suitable means. The invention is not limited to any particular polymer. In some embodiments, the polymer is an insoluble polymer, meaning that at least 70%, or at least 80%, or at least 90%, or at least 95%, or at least 97%, or at least 99% of the polymer is insoluble in the renewable oil at the quantities added. In some embodiments, the polymer is an edible organic polymer. In some embodiments, the polymer is polyvinyl polypyrrolidone (PVPP). The invention is not limited to the use of any particular quantity of polymer. The amount of polymer will vary depending on the nature of the renewable oil and the concentration of various impurities in the oil. In some embodiments, the polymer is added to the renewable oil at a concentration of 0.5 to 10 weight percent, based on the total weight of the oil-polymer mixture.

[0028] The method includes various ways of contacting the polymer with the impurities that are sought to be removed from the renewable oil. In some embodiments, the method includes mixing the cooled renewable oil and the polymer to form an oil-polymer mixture, which comprises solidified impurities. The invention is not limited to any particular method of mixing or the use of any particular mixer. For example, any suitable industrial mixer can be used. The oil-polymer mixture includes various solidified impurities, i.e., precipitated impurities, that may precipitate out of the oil, for example, by the cooling of the oil or by the presence of the polymer, or both. In some embodiments, a substantial number of the solidified impurities, for example, at least 60%, or at least 70%, or at least 80%, or at least 90%, bind to the added polymer.

[0029] In such embodiments, the method generally includes separating at least a portion of the solidified impurities from the oil-polymer mixture to form a refined renewable oil. Any suitable amount of the impurities can be removed. In some embodiments, at least 60%, or at least 70%, or at least 80%, or at least 90%, of the solidified impurities are separated from the renewable oil. The separating of these impurities from the renewable oil yields a refined renewable oil, which generally has a lower cloud point than before the performance of the method. In some embodiments, the method reduces the cloud point of the renewable oil by at least 2° C., or by at least 4° C., or by at least 6° C. The separating can be performed by any suitable method, In some embodiments, the separating is performed by centrifugation.

[0030] In some other embodiments, the method includes binding the polymer to certain impurities in the renewable oil. Such impurities can include phosphorus-containing compounds (as described above), the free fatty acids (as described above), or both the phosphorus-containing compounds and the free fatty acids.

[0031] In such embodiments, the method generally includes separating at least a portion of the polymer to form a refined renewable oil. Any suitable amount of the polymer can be removed. In some embodiments, at least 70%, or at least 80%, or at least 90%, or at least 95%, or at least 97%, or at least 99% of the polymer is separated from the renewable oil. The separating of the polymer from the renewable oil yields a refined renewable oil, as the polymer binds to certain impurities in the renewable oil. Once the method if performed, the resulting refined renewable oil generally has a lower cloud point than before the performance of the method. In some embodiments, the method reduces the cloud point of the renewable oil by at least 2° C. or by at least 4° C., or by at least 6° C. The separating can be performed by any suitable method. In some embodiments, the separating is performed by centrifugation. In some other embodiments, the separating is performed by filtering. In some further embodiments, the separating is performed by settling.

[0032] The practice of the above methods can impart other benefits in addition to those described. For example, the methods also have the effect of removing unwanted soaps from the renewable oil. Further, the methods can remove certain colors (or discoloration) from the renewable oil. In some embodiments, bleaching clay is added to the renewable oil to remove certain colors from the oil. The bleaching clay is then subsequently separated from the renewable oil according to any of the separating techniques described above or known in the art.

[0033] In another aspect, the invention provides methods of reducing the cloud point of a renewable oil, the method consisting essentially of: providing a renewable oil, which comprises waxy impurities; cooling the renewable oil; adding a polymer to the cooled renewable oil; mixing the cooled renewable oil and the polymer to form an oil-polymer mixture, which comprises solidified impurities; and separating at least a portion of the solidified impurities from the oil-polymer mixture to form a refined renewable oil. The various embodiments of these features are described above, and are incorporated herein by reference.

[0034] In another aspect, the invention provides methods of reducing the cloud point of a renewable oil, the method consisting essentially of: providing a renewable oil, wherein the renewable oil comprises phosphorus-containing compounds, free fatty acids, or a combination thereof; cooling the renewable oil; adding a polymer to the cooled renewable oil; binding the polymer to the phosphorus-containing compounds, the free fatty acids, or both the phosphorus-containing compounds and the free fatty acids; and separating at least a portion of the polymer to form a refined renewable oil. The various embodiments of these features are described above, and are incorporated herein by reference.

[0035] FIG. 1 depicts a flow chart of one method of reducing the cloud point of a renewable oil 100, the method includes: providing a renewable oil, which comprises waxy impurities 101; cooling the renewable oil 102; adding a polymer to the cooled renewable oil 103; mixing the cooled renewable oil and the polymer to form an oil-polymer mixture, which comprises solidified impurities 104; and separating at least a portion of the solidified impurities from the oil-polymer mixture to form a refined renewable oil 105.

[0036] FIG. 2 depicts a flow chart of one method of reducing the cloud point of a renewable oil 200, the method includes: providing a renewable oil, wherein the renewable oil comprises phosphorus-containing compounds, free fatty acids, or a combination thereof 201; cooling the renewable oil 202; adding a polymer to the cooled renewable oil 203; binding the polymer to the phosphorus-containing compounds, the free fatty acids, or both the phosphorus-containing compounds and the free fatty acids 204; and separating at least a portion of the polymer to form a refined renewable oil 205.

[0037] In some embodiments, the above methods can be incorporated into a larger refining process, such as the refining of biodiesel. FIG. 3 shows a flow chart for a biodiesel refinery process 300, which includes: drying and filtering the raw oil 301; adding acid to effect high free fatty acid esterification 302; performing trans-esterification to yield biodiesel 303; removing methanol or other alcohols from the trans-esterification 304; washing the product with water or another aqueous medium 305; dry the product 306; performing wax removal according to any of the above-described embodiments 307; removal of color 308 to achieve a finished biodiesel 309.

EXAMPLE

[0038] A crude corn oil sample (100 kg) is obtained, which contains about 14 weight percent free fatty acids and also contains certain phosphorus-containing compounds, such as phospholipids or their derivatives. The oil is cooled in a refrigerated tank to about -6° C. An amount of PVPP (1-2 kg) is added, and mixed into the renewable oil using an industrial mixer. The polymer is mixed into the oil for about 5 minutes, while maintaining the oil at a temperature of about -6° C. The resulting oil-polymer mixture is centrifuged, so as to separate precipitated particles from the renewable oil. The refined oil is then collected. About 95% of the original oil is recovered in the process. The cloud point is reduced by 4° C.

Claims

1. A method of reducing the cloud point of a renewable oil, the method comprising: providing a renewable oil, which comprises waxy impurities; cooling the renewable oil; adding a polymer to the cooled renewable oil: mixing the cooled renewable oil and the polymer to form an oil-polymer mixture, which comprises solidified impurities; and separating at least a portion of the solidified impurities from the oil-polymer mixture to form a refined renewable oil.

2. The method of claim 1, wherein the renewable oil comprises a vegetable oil, an animal oil, or a mixture thereof.

3. The method of claim 1, wherein the renewable oil comprises corn oil.

4. The method of claim 1, wherein the renewable oil is a crude renewable oil.

5. The method of claim 1, wherein the renewable oil is a renewable oil that is at least partially refined.

6. The method of claim 1, wherein the waxy impurities comprise one or more phosphorus-containing compounds.

7. The method of claim 6, wherein the one or more phosphorus-containing compounds comprise hydratable phosphatides, non-hydratable phosphatides, or a mixture thereof.

8. The method of claim 1, wherein the cooling comprises cooling the renewable oil to a temperature below 5.degree. C.

9. The method of claim 1, wherein the cooling comprises cooling the renewable oil to a temperature below 3.degree. C.

10. The method of claim 1, wherein the cooling comprises cooling the renewable oil to a temperature below 1.degree. C.

11. The method of claim 1, wherein the polymer is an edible organic polymer.

12. The method of claim 1, wherein the polymer is a polyvinyl polypyrrolidone polymer.

13. The method of claim 1, wherein the separating comprises centrifuging the oil-polymer Mixture.

14. The method of claim 1, wherein the cloud point of the refined renewable oil is at least 2.degree. C. lower than the cloud point of the renewable oil.

15. The method of claim 1, wherein the cloud point of the refined renewable oil is at least 4.degree. C. lower than the cloud point of the renewable oil.

16. The method of claim 1, wherein the cloud point of the refined renewable oil is at least 6.degree. C. lower than the cloud point of the renewable oil.

17. A method of reducing the cloud point of a renewable oil, the method comprising: providing a renewable oil, wherein the renewable oil comprises phosphorus-containing compounds, free fatty acids, or a combination thereof; cooling the renewable oil; adding a polymer to the cooled renewable oil; binding the polymer to the phosphorus-containing compounds, the free fatty acids, or both the phosphorus-containing compounds and the free fatty acids; and separating at least a portion of the polymer to form a refined renewable oil.

18. The method of claim 18, wherein the renewable oil comprises a vegetable oil, an animal oil, or a mixture thereof.

19. The method of claim 18, wherein the renewable oil comprises corn oil.

20. The method of claim 18, wherein the renewable oil is a crude renewable oil.

21. The method of claim 18, wherein the renewable of is a renewable oil that is at least partially refined.

22. The method of claim 18, wherein the renewable oil comprises phosphorus-containing compounds, and the binding step comprises binding the polymer to the phosphorus-containing compounds.

23. The method of claim 23, wherein the one or more phosphorus-containing compounds comprise hydratable phosphatides, non-hydratable phosphatides, or a mixture thereof.

24. The method of claim 18, wherein the renewable of comprises free fatty acids, and the binding step comprises binding the polymer to the free fatty acids.

25. The method of claim 18 where the binding step comprises mixing the cooled renewable oil and the polymer to form an oil-polymer mixture.

26. The method of claim 18, wherein the cooling comprises cooling the renewable oil to a temperature below 40.degree. C.

27. The method of claim 18, wherein the cooling comprises cooling the renewable oil to a temperature below 36.degree. C.

28. The method of claim 18, wherein the cooling comprises cooling the renewable oil to a temperature below 33.degree. C.

29. The method of claim 18, wherein the polymer is an edible organic polymer.

30. The method of claim 18, wherein the polymer is a polyvinyl polypyrrolidone polymer.

31. The method of claim 18, wherein the separating comprises centrifuging.

32. The method of claim 18, wherein the cloud point of the refined renewable oil is at least 2.degree. C. lower than the cloud point of the renewable oil.

33. The method of claim 18, wherein the cloud point of the refined renewable oil is at least 4.degree. C. lower than the cloud point of the renewable oil.

34. The method of claim 18, wherein the cloud point of the refined renewable oil is at least 6.degree. C. lower than the cloud point of the renewable oil.

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