WO2018191653A1

WO2018191653A1 - Methods and compositions for biodiesel production

Info

Publication number: WO2018191653A1
Application number: PCT/US2018/027548
Authority: WO
Inventors: Sanjeev Gupta; Gangadhar M. RAO
Original assignee: Aemetis, Inc.
Priority date: 2017-04-13
Filing date: 2018-04-13
Publication date: 2018-10-18

Abstract

Provided are compositions and methods for producing a biodiesel with a specified ester content.

Description

METHODS AND COMPOSITIONS FOR BIODIESEL PRODUCTION CROSS-REFERENCE TO RELATED APPLICATIONS [0001] The application claims the benefit of U.S. Provisional Application No.62/485,348, filed April 13, 2017, which is incorporated herein by reference in its entirety. FIELD [0002] The disclosure relates to the production of biodiesel from feedstock. BACKGROUND [0003] There is a need in the art for methods of production of high ester content biodiesel. Such methods are provided herein. SUMMARY [0004] The present disclosure provides a method of producing a biodiesel having an ester content of at least 95% comprising the steps of: a) adding a feedstock mixture comprising feedstock and 0.3% enzyme into a reactor, wherein the feedstock comprises at least 50% free fatty acids (FFA) and at least 30% triglyceride; b) adding between 5 and 15% methanol to the reactor within 4 hours of adding the feedstock mixture into the reactor, wherein the feedstock mixture, enzyme, and methanol are under constant agitation; c) adding an additional 13 to 16% methanol to the reactor at the rate of 1% per hour, for between 9 and 11 hours; d) testing the feedstock mixture for ester, FFA and triglycerides; e) adding between 9 and 11% NaOH solution to the reactor when the FFA concentration of the feedstock mixture is between 2 and 4% w/v; f) transferring the feedstock mixture to an intermediate tank when the FFA concentration of the feedstock mixture is between 0.2 and 2.5% w/v; g) transferring the feedstock mixture to a bioreactor, wherein the temperature of the bioreactor is between 60 and 70°C and the vacuum of the bioreactor is between 500 and 800 Torr; h) transferring the feedstock mixture to a first settlement tank, wherein a light phase comprising biodiesel, methanol and moisture is separated from a heavy phase consisting of soap, glycerol, and water; i) separating and centrifuging the light phase; and j) reducing the concentration of methanol and moisture in the centrifuged light phase, thereby producing the biodiesel having an ester content of at least 95%. [0005] In one aspect, the method further comprises mixing the crude biodiesel and no greater than 10% ethanol with the feedstock before step a). [0006] In some embodiments, about 11% methanol is added in step b). [0007] In some embodiments about 15% methanol is added for at least 10 hours in step c). [0008] In some embodiments, about 10% NaOH mixture is added when the FFA is about 3% w/v in step e). [0009] In some embodiments, the feedstock mixture is transferred when the FFA is about 0.3% in step f). [0010] In some embodiments, the temperature of the bioreactor is 65°C and the vacuum is 700 Torr in step g). [0011] In certain embodiments, the enzyme catalyzes at least one of transesterification and esterification reactions. In a preferred embodiment, the enzyme catalyzes transesterification and esterification reactions. [0012] In an aspect of the disclosure, the method comprises an additional step of distilling the biodiesel. In some embodiments, the distilled biodiesel has an ester content of at least 99.5%. [0013] In an aspect of the disclosure, the method further comprises transferring the heavy phase produced in step h) to a second settlement tank, then skimming the top phase comprising FFA, and removing the bottom phase comprising crude glycerol. [0014] In some embodiments, the glycerol is at least partially purified and stored. [0015] In some embodiments, hydrochloric acid is added to the second settlement tank. [0016] In some embodiments, glycerol purification produces a byproduct comprising oleins. [0017] In some embodiments, the olein byproduct is saved for use in a further reaction for producing biodiesel. [0018] In an aspect of the disclosure, the method further comprises adding citric acid to the feedstock mixture before centrifugation at step i). [0019] In an aspect of the disclosure, the method further comprises adding the trace amount of methanol and moisture from the centrifuged light phase of step j) to a bioreactor for use in a further reaction for producing biodiesel. [0020] The summary of the disclosure described above is non-limiting and other features and advantages of the disclosed apparatus and methods will be apparent from the following detailed description of the disclosure, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS [0021] FIG. 1 is a flow diagram of the disclosed method of producing a biodiesel. DETAILED DESCRIPTION OF THE DISCLOSURE [0022] The present disclosure is directed to a method of producing a biodiesel. In certain embodiments, the biodiesel has a high ester content. According to certain embodiments, the high ester content is at least 90.0, 91.0, 92.0, 93.0, 94.0, 95.0, 95.5, 96.0, 96.5, 97.0, 97.5, 98.0, 98.5, 99.0, 99.5 or 100%, In certain embodiments, the biodiesel has an ester content of at least 95%. According to other embodiments, the biodiesel has an ester content of greater than 99.5%. [0023] The methods provided herein include providing a feedstock comprising free fatty acids (FFA), tryglyceride and in certain embodiments, other impurities. The impurities can include water. According to certain embodiments, the feedstock is at least 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69 or 70 % FFA. According to these embodiments, the feedstock also includes about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20% impurities. The balance of the feedstock is triglyceride. According to certain embodiments, there is at least 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48 or 49% triglyceride. According to certain embodiments, the feedstock is 60-70% FFA, 25-35% triglyceride with the balance of the feedstock being impurities. According to certain embodiments the feedstock is about 50% FFA, about 30% triglyceride and about 20% impurities. According to certain embodiments the feedstock is 50% FFA, 30% triglyceride and 20% impurities. [0024] According to certain embodiments, the feedstock is combined with biodiesel and ethanol. The biodiesel and ethanol are added to reduce the melting point of the mixture. According to certain embodiments, the melting point of the mixture is reduced to below 35, 36, 37, 38, 39, 40, 41, 42, 43, 44 or 45 °C. According to certain embodiments, the melting point of the mixture is reduced to below about 39 °C. According to certain embodiments, the melting point of the mixture is reduced to below 39 °C. [0025] In order to reduce the melting point of the mixture an amount of ethanol is added so that ethanol is up to 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15% of the mixture w/v.

According to certain embodiments, an amount of ethanol is added so that ethanol is up to 10% of the mixture w/v. [0026] The feedstock, either subject to treatment with biodiesel and/or ethanol or not, is added to a reactor. In certain embodiments, enzyme is also added to the reactor. In certain embodiments enzyme is added so that it makes up about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.0% of the total mixture in the reactor. In certain embodiments enzyme is added so that it makes up about 0.3% of the total mixture in the reactor. In certain embodiments, the enzyme catalyzes at least one of transesterification and esterification reactions. In a preferred embodiment, the enzyme catalyzes transesterification and esterification reactions. In certain embodiments, the mixture is agitated while in the reactor. [0027] Methanol is then gradually added to the mixture in the reactor. The methanol is added over a period of at least 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 hours up to 15-20 hours. In certain embodiments, the methanol is added over a period of at least 4 hours up to 15-20 hours. In certain embodiments, the methanol is added over a period of about 4 hours. In certain embodiments, the methanol is added over the period at a volume that is at least 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15% of the mixture. According to certain embodiments, the methanol is added over the period at a volume that is at least 11% of the mixture up to 15-20% of the mixture. According to certain embodiments, the methanol is added over the period at a volume that is about 11% of the mixture. [0028] In certain embodiments, additional methanol is then added to the mixture. This additional amount of methanol can be about 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20% of the volume of the mixture. In certain embodiments, the additional amount of methanol can be about 15% of the volume of the mixture. This additional amount of methanol is added over a period of time. This period of time can be at least 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 hours up to 25 hours. In certain embodiments, the additional amount of methanol is added over a period of 10-15 hours. [0029] According to certain embodiments, during the period when the additional methanol is added to the reactor, the mixture in the reactor is tested for the concentration of one or more of ester, FFA and triglycerides. According to certain embodiments, when the concentration of FFAs is reduced to at most 1, 2, 3, 4, 5, 6, 7 or 8% of the total mixture w/v then a basic solution is added to the mixture. In certain embodiments, when the

concentration of FFAs is reduced to at most 3% of the total mixture w/v then a basic solution is added to the mixture. In certain embodiments, when the concentration of FFAs is reduced to about 3% of the total mixture w/v then a basic solution is added to the mixture. According to certain embodiments, the basic solution is NaOH. According to certain embodiments, the NaOH solution is about a 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15% solution of NaOH.

According to certain embodiments, the NaOH solution is about a 10% solution of NaOH. According to certain embodiments, the reaction is stopped when the concentration of FFA in the mixture is at most 0.1, 0.2, 0.3, 0.40.5, 0.6, 0.7, 0.8, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4% or 2.5% w/v. In certain embodiments, the mixture is then transferred to an intermediate tank. [0030] In certain embodiments, the mixture is added to a flash drying chamber. The flash drying chamber is capable of applying increased heat and reduced pressure to the mixture. In certain embodiments, the elevated temperature is about 60, 61, 62, 63, 64, 65, 66, 67, 68, 69 or 70 °C. In certain embodiments, the elevated temperature is about 65 °C. In certain embodiments, the reduced pressure is about 650, 660, 670, 680, 670, 700, 710, 720 or 730 Torr. In certain embodiments, the reduced pressure is about 700 Torr. In certain

embodiments, the flash dying chamber is an A4 reactor used in a biodiesel plant. [0031] While the mixture is in the flash drying chamber, excess methanol is removed from the mixture. According to certain embodiments, the excess methanol is about 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20% of the mixture w/v. In certain embodiments, the excess methanol is about 15% of the mixture w/v. [0032] According to certain embodiments, the mixture is then allowed to settle. In certain embodiments, this settling step is done in a settlement tank. According to certain embodiments, the settlement tank is an S1 tank. The settlement of the mixture results in a light and heavy phase. According to certain embodiments, the light phase comprises most of the biodiesel and some quantity of methanol and water. In certain embodiments, the light phase contains at least 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 or 100% of the biodiesel from the total mixture. According to certain embodiments, the heavy phase comprises most of the soap, glycerol and water in the mixture. In certain embodiments, the heavy phase contains at least 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 or 100% of the soap, glycerol and water from the total mixture. [0033] According to certain embodiments, the light and heavy phases are separated. In certain embodiments, the light phase undergoes centrifugation to separate residual methanol and water from the biodiesel. In certain embodiments, after centrifugation and separation of methanol and water from the biodiesel, the light phase contains at least 90.0, 91.0, 92.0, 93.0, 94.0, 95.0, 95.5, 96.0, 96.5, 97.0, 97.5, 98.0, 98.5, 99.0% biodiesel. In certain embodiments, the light phase is at least 96.5% biodiesel. Optionally, the light phase can undergo additional distillation. As a result of the optional distillation, the light phase can contain at least 93.0, 94.0, 95.0, 95.5, 96.0, 96.5, 97.0, 97.5, 98.0, 98.5, 99.0, 99.5 or 100% biodiesel. In certain embodiments, the distilled light phase is at least 99.5% biodiesel. [0034] In certain embodiments, the heavy phase is subject to a process which separates FFA from their salts. In certain embodiments, this process includes acid treatment. According to certain embodiments, the acid is hydrochloric acid. According to certain embodiments, the FFA are skimmed away from the remainder of the heavy phase. According to certain embodiments, the glycerol is isolated and concentrated. [0035] It is to be understood that the methods described in this disclosure are not limited to particular methods and experimental conditions disclosed herein; as such methods and conditions may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. [0036] Unless otherwise defined herein, scientific and technical terms used herein have the meanings that are commonly understood by those of ordinary skill in the art. In the event of any latent ambiguity, definitions provided herein take precedent over any dictionary or extrinsic definition. Unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular. The use of“or” means“and/or” unless stated otherwise. The use of the term“including”, as well as other forms, such as“includes” and“included”, is not limiting. As used herein, unless otherwise stated, the singular forms “a,”“an,” and“the” include plural reference. Thus, for example, a reference to“a protein” includes a plurality of protein molecules. [0037] The methods and techniques provided herein are generally performed according to conventional methods well known in the art and as described in various general and more specific references that are cited and discussed throughout the present specification unless otherwise indicated. Enzymatic reactions and purification techniques are performed according to manufacturer’s specifications, as commonly accomplished in the art or as described herein. The nomenclatures used in connection with, and the laboratory procedures and techniques of, analytical chemistry, synthetic organic chemistry, and medicinal and pharmaceutical chemistry described herein are those well-known and commonly used in the art. Standard techniques are used for chemical syntheses, chemical analyses, pharmaceutical preparation, formulation, and delivery, and treatment of patients. [0038] That the disclosure may be more readily understood, select terms are defined below. [0039] As used herein, the term“biodiesel” refers to a vegetable oil or animal fat-based diesel fuel consisting of long-chain alkyl esters. [0040] As used herein, the term“feedstock” refers to the starting material from which the biodiesel is produced. In some embodiments, the feedstock comprises 65% free fatty acids (FFA) and 30% glycerol. [0041] As used herein, the term“olein” refers to residual fatty acids. In some embodiments, glycerol purification produces a byproduct comprising oleins. [0042] As used herein, the term“bioreactor” or“flash drying chamber” refers to a vessel that carries out a reaction. In certain embodiments that bioreactor or flash drying chamber is capable of applying increased heat and reduced pressure to the mixture. [0043] It will be readily apparent to those skilled in the art that other suitable modifications and adaptations of the methods described herein may be made using suitable equivalents without departing from the scope of the embodiments disclosed herein. Having now described certain embodiments in detail, the same will be more clearly understood by reference to the following examples, which are included for purposes of illustration only and are not intended to be limiting. Example 1: Enzymatic Conversion of Biodiesel [0044] Feedstock which is 65% free fatty acids (FFA) and 30% triglyceride (the balance is made up of unsaps/impurities) is mixed with biodiesel and maximum 10% ethanol to reduce melting point down to 39^oC. If the melting point of feedstock is in any case 39^oC or less, the feedstock does not need any pretreatment. [0045] The feedstock with 0.3% enzyme is fed into the reactor. The reaction requires 11% methanol dosing which is pumped into the reactor 4 hours from the start of the reaction. The reactants inside the reactor are under constant agitation. An additional 15% methanol is then added to the reactor at the rate of 1% per hour. After 10 hours of reaction, the homogenous solution inside the reactor is tested for ester, FFA, and triglycerides. Once the FFA is down to 3%, NaOH solution (10% concentration) is added to the reactor. Once the FFA is down to 0.3%, the reaction is stopped and the entire feedstock is transferred to an intermediate tank. [0046] From the intermediate tank, the feedstock is fed into the A4 reactor in the biodiesel plant. A4 is a flash drying chamber which recovers the excess 15% methanol. The temperature is 65^oC and the vacuum is 700. From the A4 tank the reaction is then sent to the S1 tank which is a settlement tank where the light phase consisting of all the biodiesel and some small quantity of methanol and moisture is separated from the heavy phase consisting of soap, glycerol, and water is separated. The lighter phase goes to the centrifuge for clean- up and the heavy phase goes to S2 for splitting soap to FFA and salts. FFA floats to the top and is skimmed. The bottom phase is crude glycerol which is then refined. The cleaned from the centrifuge is then either stored as biodiesel, or sent to the distillation column for distillation. The biodiesel thus produced has an ester content of 96.5%. In the case that the customer requires 99.5% ester, the biodiesel is then distilled. * * * * * [0047] The contents of the articles, patents, and patent applications, and all other documents and electronically available information mentioned or cited herein, are hereby incorporated by reference in their entirety to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference. Applicants reserve the right to physically incorporate into this application any and all materials and information from any such articles, patents, patent applications, or other physical and electronic documents. [0048] The methods illustratively described herein may suitably be practiced in the absence of any element or elements, limitation or limitations, not specifically disclosed herein. Thus, for example, the terms“comprising”,“including,” containing”, etc. shall be read expansively and without limitation. Additionally, the terms and expressions employed herein have been used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof. It is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the invention embodied therein herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention. [0049] The invention has been described broadly and generically herein. Each of the narrower species and subgeneric groupings falling within the generic disclosure also form part of the methods. This includes the generic description of the methods with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein. [0050] Other embodiments are within the following claims. In addition, where features or aspects of the methods are described in terms of Markush groups, those skilled in the art will recognize that the invention is also thereby described in terms of any individual member or subgroup of members of the Markush group.

Claims

CLAIMS What is claimed is:

1. A method of producing a biodiesel having an ester content of at least 95% comprising the steps of: a) adding a feedstock mixture comprising feedstock and 0.3% enzyme into a reactor, wherein the feedstock comprises at least 65% free fatty acids (FFA) and at least 30% triglyceride; b) adding between 5 and 15% methanol to the reactor within 4 hours of adding the feedstock mixture into the reactor, wherein the feedstock mixture, enzyme, and methanol are under constant agitation; c) adding an additional 13 to 16% methanol to the reactor at the rate of 1% per hour, for between 9 and 11 hours; d) testing the feedstock mixture for ester, FFA and triglycerides; e) adding between 9 and 11% NaOH solution to the reactor when the FFA concentration of the feedstock mixture is between 2 and 4% w/v; f) transferring the feedstock mixture to an intermediate tank when the FFA concentration of the feedstock mixture is between 0.2 and 2.5% w/v; g) transferring the feedstock mixture to a bioreactor, wherein the temperature of the bioreactor is between 60 and 70°C and the vacuum of the bioreactor is between 500 and 800 Torr; h) transferring the feedstock mixture to a first settlement tank, wherein a light phase comprising biodiesel, methanol and moisture is separated from a heavy phase consisting of soap, glycerol, and water; i) separating and centrifuging the light phase; and j) reducing the concentration of methanol and moisture in the centrifuged light phase, thereby producing the biodiesel having an ester content of at least 95%.

2. The method of claim 1, further comprising mixing the crude biodiesel and no greater than 10% ethanol with the feedstock before step a).

3. The method of claim 1 or 2, wherein in step b) about 11% methanol is added.

4. The method of claim 3, wherein in step c) about 15% methanol is added for at least 10 hours.

5. The method of claim 4, wherein in step e) about 10% NaOH solution is added when the concentration of FFA in the feedstock mixture is about 3% w/v.

6. The method of claim 5, wherein in step f) the feedstock mixture is transferred when the FFA concentration in the feedstock mixture is about 0.3% w/v.

7. The method of claim 6, wherein in step g), the temperature of the bioreactor is 65°C and the vacuum is 700 Torr.

8. The method of any one of the preceding claims, wherein the enzyme catalyzes at least one of transesterification and esterification reactions.

9. The method of claim 8, the enzyme catalyzes transesterification and esterification reactions.

10. The method of any one of the preceding claims, comprising an additional step of distilling the biodiesel.

11. The method of claim 10, wherein the distilled biodiesel has an ester content of at least 99.5%.

12. The method of any one of the preceding claims, further comprising transferring the heavy phase produced in step h) to a second settlement tank, then skimming the top phase comprising FFA, and removing the bottom phase comprising crude glycerol.

13. The method of claim 12, further comprising at least partially purifying and storing the glycerol.

14. The method of claim 13, wherein hydrochloric acid is added to the second settlement tank.

15. The method of claim 14, wherein glycerol purification produces a byproduct comprising oleins.

16. The method of claim 15, further comprising saving the olein byproduct for use in a further reaction for producing biodiesel.

17. The method of any one of the preceding claims, further comprising adding citric acid to the feedstock mixture before centrifugation at step i).

18. The method of any one of the preceding claims, further comprising adding the trace amount of methanol and moisture from the centrifuged light phase of step j) to a bioreactor for use in a further reaction for producing biodiesel.