FATTY ACID REDUCTION OF FEEDSTOCK AND NEUTRAL AND ACIDIC ALKYL ESTER

Abstract

Processes and compositions reduce free fatty acid (FFA) in oils and fats and in neutral or acidic alkyl ester. The oils and fats or alkyl ester is heated to temperatures from 90° F. to 150° F., and lower numbered alcohol and dilute caustic are added. The mixture is stirred moderately, and allowed to settle into two phases—a FFA phase and a second low FFA phase, containing either oils and fats or alkyl ester. The two phases are separated. The recovery of both glycerin and lower numbered alcohols is increased. Some compositions for reducing FFA comprise lower numbered alcohol and dilute caustic. The processes and compositions reduce FFA levels to meet fuel standards.

Description

RELATED APPLICATIONS

The present U.S. non-provisional patent application is related to and claims priority benefit to an earlier-filed provisional patent application titled FATTY ACID REDUCTION OF FEEDSTOCK AND NEUTRAL AND ACIDIC ALKYL ESTER, Ser. No. 62/006,017, filed May 30, 2014. The identified earlier-filed application is hereby incorporated by reference into the present application as though fully set forth herein.

FIELD OF THE INVENTION

This disclosure relates to processes for refining biodiesel and to compositions in the refining process. In particular, the disclosure relates to processes and compositions for reducing free fatty acid content in the feedstock, and for reducing free fatty acid content in neutral or acidic alkyl ester mixtures by neutralizing and separating free fatty acid from neutral or acidic alkyl esters. The disclosure also relates to processes and compositions for recovery of glycerin, free fatty acids, and alcohol reagent for reuse. The disclosure further relates to processes and compositions related to a reduced amount of alcohol reagent used in refining.

BACKGROUND

Biodiesel is a renewable biofuel that can be used in existing applications, often in blends with petroleum-based diesel. Production of biodiesel generally occurs via a transesterification process, using feedstock such as oils or fats. The transesterification reaction involves mixed fatty glycerides, predominantly triglycerides, from the feedstock with alkyl alcohols, often using a catalyst, to produce long chain alkyl esters—the crude biodiesel. The crude biodiesel is further refined to remove impurities to obtain a finished biodiesel product. Biodiesel production and refinement processes are normally costly and often involve hazardous materials.

Feedstock normally comprises mixed fatty glycerides and free fatty acid (FFA). FFA is an impurity that must be sufficiently reduced in order to obtain the finished biodiesel product, often with FFA less than 0.25% wt/wt. Unless otherwise indicated, percent values in this disclosure are calculated on a wt/wt basis. The quality of feedstock varies from higher quality food-grade oils having lower FFA levels to lower quality recycled cooking oil and animal fats having higher FFA levels. Although feedstock with lower FFA content is preferred for biodiesel production, it is usually costlier than feedstock with higher FFA content such as animal fats and recycled cooking oil.

Feedstock may be subjected to an esterification process in order to reduce the FFA content. The esterification may be acid-catalyzed and converts the FFA to long chain alkyl esters. The esterification may take place either prior to or simultaneously with the primary transesterification process that produces crude biodiesel. Although esterification may convert some FFA to crude biodiesel, the FFA level of the resultant crude usually remains higher than desired. Further refining is almost always necessary, and current refining methods to reduce the FFA content of crude biodiesel produced from feedstock to acceptable levels have various drawbacks. Current methods are difficult, require significant amount of capital equipment, require a large excess of reagents such as methanol, incur long refining time, fail to maximize recovery of reagents, require expensive resins, generate large amounts of waste water, and/or decrease yield of finished biodiesel. It is desirable to reduce the FFA content of feedstock in a cost-effective manner, including recovering byproducts and reagents, and not requiring a large excess of reagents. It is also desirable to refine crude biodiesel produced in a cost-effective manner, including reducing the FFA level, recovering byproducts and reagents, not requiring a large excess of reagents, and not generating a large amount of waste water. Moreover, it is desirable to produce biodiesel from less expensive feedstock.

The primary crude biodiesel production reaction is the transesterification of the mixed fatty glycerides with alkyl alcohols, and normally results in a mixture that comprises alkyl esters (the crude biodiesel), alcohols, glycerin, and glycerides (predominantly monoglycerides). A substantial amount of glycerin in the production of crude biodiesel is normally removed by gravity separation and may be further processed and sold. After the bulk of glycerin is removed from the crude biodiesel, a residual amount of glycerin nevertheless remains in the crude biodiesel. The conventional practice is to allow the residual glycerin to remain in the crude biodiesel at this stage in refining. This is necessary because many conventional methods to reduce the FFA content of the crude biodiesel are practical only when the FFA and the biodiesel are not emulsified. The residual glycerin serves to keep the two components demulsified. The glycerin later partitions to the soap phase and is removed by centrifugation. However, soaps often prove difficult to separate from the alkyl ester, and thus carry large amount of excess alkyl ester with it. It is desirable to recover a maximum amount of glycerin, while effectively demulsifying the crude biodiesel for further refining and improving the yield of finished biodiesel.

SUMMARY

Unless otherwise specified, the meanings of the following terms used throughout this disclosure are provided in this paragraph. The term “lower alkyl alcohol” refers to alcohols having 1 to 4 carbon atoms and the term “lower alkyl diol” refers to diols having 2 to 4 carbon atoms. The term “lower numbered alcohol” refers to a lower alkyl alcohol or lower alkyl diol. Examples of lower numbered alcohols include methanol and propylene glycol. The term “alkyl ester(s)” refers to “mono-alkyl ester(s) of lower numbered alcohols”. The term “caustic” refers to an alkali metal hydroxide. In some embodiments, the caustic is sodium hydroxide or potassium hydroxide. The terms “glycerin”, “glycerine”, and “glycerol” are synonymous. The terms “alcoholic aqueous soap” and “methylated liquid soap” are synonymous, and both refer to an aqueous phase comprising the lower numbered alcohol or diol, and the soap of fatty acid.

Standard processes such as acid refining and degumming 164 can be used at the outset of biodiesel production to remove impurities and gums, if necessary, from purchased crude oils and fats—the crude feedstock. Whether such pre-processing is necessary depends on the source and quality of purchased crude. The refining and degumming are known methods for pre-processing the crude feedstock to form prepared feedstock that is substantially free of impurities and gums. The prepared feedstock so obtained from pre-processing includes oils and fats, and are also referred to herein as parent oils or feedstock. Some processes disclosed herein are used to reduce the FFA levels of such feedstock.

Some aspects of the disclosed processes and compositions are directed to separating FFA from parent oils/feedstock for production of biodiesel. Some embodiments of this disclosure are directed to reducing the FFA content of feedstock by neutralizing and reducing the FFA level. In one embodiment, a process for reducing the FFA level in feedstock comprises heating the feedstock to a temperature from 140 degrees Fahrenheit to 150 degrees Fahrenheit to form a heated feedstock; adding the lower numbered alcohol and the dilute caustic to the heated feedstock to form a parent oil mixture; continuously stifling the parent oil mixture for a period from 10 minutes to 20 minutes; and allowing the parent oil mixture to settle at temperature to form a neat liquid with two phases; wherein the feedstock has FFA levels of at least 0.5% wt/wt. In some embodiments, the parent oil mixture is permitted to cool off to room temperature while settling. The neat liquid, two phase separation is an unexpected result, because conventional knowledge predicts this mixture to be a gel, paste or semi-solid.

The types of the feedstock include natural fats and oils, such as but not limited to, distiller's corn oil, castor oil, soybean oil, jatropha oil, algae oil, yellow grease, brown grease, lard, and beef tallow. Embodiments of the lower numbered alcohol include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, propylene glycol, ethylene glycol, and butylene glycol. Embodiments of dilute caustic include aqueous sodium hydroxide and aqueous potassium hydroxide, and may have concentrations from 2% to 15% wt/wt, from 3% to 6% wt/wt, and from 4% to 5% wt/wt. The amount of dilute caustic added may be from stoichiometric to the amount of FFA in the parent oil mixture to 20% excess of stoichiometric. Dilute caustic may be added in other amounts, including from stoichiometric to the amount of FFA in the parent oil mixture to 10% excess of stoichiometric, and from stoichiometric to the amount of FFA in the parent oil mixture to 5% excess of stoichiometric.

The lower numbered alcohol and the dilute caustic may be added simultaneously, or sequentially. When added sequentially, the preferred sequence is to add the lower numbered alcohol first. In some embodiments, the feedstock may be heated to a temperature from 120 degrees Fahrenheit to 150 degrees Fahrenheit, or from 90 degrees Fahrenheit to 150 degrees Fahrenheit. In some embodiments, the parent oil mixture may be continuously stirred for a period from 10 minutes to 1 hour, or from 10 minutes to 2 hours. In some embodiments the first phase of the two phases comprises feedstock and FFA, wherein the feedstock is at least 97% wt/wt, the FFA is at a concentration not more than 0.4% wt/wt, and the second phase comprises alcoholic aqueous soap.

Other aspects of the disclosed processes and compositions are directed to reducing the FFA in alkyl esters in crude biodiesel. In one embodiment, crude biodiesel may be obtained by reacting mixed fatty glycerides of oils or fats with a catalyst, such as acid, enzyme, or heterogeneous solid catalysts. The reaction may be a result of transesterification of mixed fatty glycerides with an alkyl alcohol, such as methanol, ethanol, propanol, isopropanol, butanol, or isobutanol. The bulk of glycerin may be removed from the crude biodiesel by gravity separation. The crude biodiesel mixture so obtained may comprise neutral or acidic alkyl ester and FFA. In one embodiment, the crude biodiesel mixture comprises FFA, alkyl ester, and mixed fatty glycerides, wherein the amount of mixed fatty glycerides is at a concentration not more than 5% wt/wt. In another embodiment of the crude biodiesel mixture comprises FFA and alkyl ester, wherein the amount of FFA is no more than 5% wt/wt, and the amount of alkyl esters is from 75% to 95% wt/wt. In some embodiments, the crude biodiesel mixture may further comprise residual glycerin.

Some disclosed processes are directed to reducing the FFA content of a crude biodiesel mixture by neutralizing and separating the FFA from the alkyl ester. In one embodiment, a crude biodiesel mixture comprising FFA, alkyl ester, and mixed fatty glycerides, wherein the mixed fatty glycerides are at a concentration not more than 5% wt/wt, is heated to a temperature from 90 degrees Fahrenheit to 150 degrees Fahrenheit. Other suitable temperatures to heat the crude biodiesel mixture include from 120 degrees Fahrenheit to 150 degrees Fahrenheit, and from 140 degrees Fahrenheit to 150 degrees Fahrenheit. In some embodiments, residual glycerin in the crude biodiesel mixture is separated before heating the mixture by centrifugation, allowing for a further recovery of glycerin. A lower numbered alcohol and a dilute caustic are added to the heated mixture to form a second mixture. In some embodiments, the alcohol and caustic may be added simultaneously, while in others, one may be added before the other, with a preference for adding the alcohol first. Embodiments of the lower numbered alcohol include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, propylene glycol, ethylene glycol, and butylene glycol. Embodiments of dilute caustic include aqueous sodium hydroxide and aqueous potassium hydroxide, and may have concentrations from 2% to 15% wt/wt, from 3% to 6% wt/wt, and from 4% to 5% wt/wt. The amount of dilute caustic added may be from stoichiometric to the amount of FFA in the crude biodiesel mixture to 20% excess of stoichiometric. Dilute caustic may be added in other amounts, including from stoichiometric to the amount of FFA in the crude biodiesel mixture to 10% excess of stoichiometric, and from stoichiometric to the amount of FFA in the parent oil mixture to 5% excess of stoichiometric.

The second mixture is low-shear mixed for a period from 10 minutes to 2 hours. The mixing period may also be from 10 minutes to 1 hour, or 10 minutes to 20 minutes. The heat temperature of the second mixture is maintained during the mixing period. In one embodiment, the mixing is stifling moderately at 200 rpm with a magnetic stir bar. After the mixing, in one embodiment, the second mixture is centrifuged. In another embodiment, the second mixture is allowed to settle for 1 to 3 hours while maintaining the heat temperature. After settling, it was surprising to discover that the second mixture demulsifies into neat liquid an upper phase and a lower phase. In one embodiment, the upper phase comprises alkyl ester, and the lower phase comprises alcoholic aqueous soap. The two phases are separated by decantation.

In another aspect, disclosed processes are directed to recovering FFA from the refining process above. Thus, in one embodiment, the lower phase that comprises alcoholic aqueous soap is reacted with acid, such as hydrochloric acid, acetic acid, citric acid, phosphoric acid, sulfuric acid, and methanesulfonic acid. The reaction of the soap with the acid produces FFA, which is recovered and recycled. In a further aspect of this disclosure, processes are directed to recovering the lower numbered alcohol used above. Thus, in one embodiment, the methanol is removed from upper phase of the second mixture, resulting in a stripped alkyl ester mixture.

Other embodiments are directed to further refining the stripped alkyl ester mixture. An embodiment is directed to washing the stripped alkyl ester mixture with soft water, resulting in a mixture having two components, a wet ester component and a soap water component. The disclosed processes are further directed to removing the soap water component from the mixture, and drying the west ester component.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1a is a diagram of some aspects related to reducing free fatty acid in feedstock.

FIG. 1b is a diagram of aspects related to reducing free fatty acid in feedstock.

FIG. 1c is a diagram of some aspects related to reducing free fatty acid in neutral or acidic alkyl ester, and recovering reagents.

FIG. 1d is a diagram of aspects related to reducing free fatty acid in neutral or acidic alkyl ester, and recovering reagents.

FIG. 1e is a diagram of aspects related to recovering reagents in reducing free fatty acid in alkyl ester.

DETAILED DESCRIPTION

Systems, processes, and compositions are disclosed that enable reduction of free fatty acid (FFA) content in the feedstock that can be used in the production of crude biodiesel. Also disclosed are systems, processes, and compositions in the refining of crude biodiesel that enable reduction of FFA content, increasing the recovery of glycerin, FFA and alcohol, decreasing the amount of waste water, and an efficient, effective, and less costly refining of crude biodiesel. The disclosure is broadly directed to the use of a lower numbered alcohol and a dilute caustic in a refining process to reduce the FFA content of the feedstock for producing crude biodiesel and to reduce the FFA of the crude biodiesel produced, while maximizing the recovery of glycerin, alcohol, and FFA, and minimizing waste water generated. The result of some embodiments of the disclosed process, contrary to what conventional knowledge predicts, was an unexpected neat liquid having two-phase demulsified mixture.

A fuel with a high level of FFA causes problems in engines. Feedstock used for producing crude biodiesel normally comprises FFA, oftentimes a high level of FFA. The types of feedstock that may be used with some embodiments in this disclosure include natural fats and oils, such as but not limited, to distiller's corn oil, castor oil, soybean oil, jatropha oil, algae oil, yellow grease, brown grease, lard, and beef tallow. The list of feedstock types is illustrative and not intended to be limiting. The FFA content is usually reduced during refining of crude biodiesel in order for the biodiesel to meet the total acid number (TAN) fuel quality standards set by ASTM International (ASTM). The TAN of a biodiesel fuel is an indicator of FFA content.

Some embodiments of this disclosure are directed to reducing the FFA content of feedstock by neutralizing and separating the FFA, accomplished by mixing the feedstock with lower numbered alcohol and dilute caustic. After the FFA is separated from the feedstock, the resulting refined feedstock in some embodiments comprises less than 0.5% wt/wt FFA. Unless otherwise indicated, percent values in this disclosure are calculated on a wt/wt basis. Such refined feedstock is ideal for producing crude biodiesel via transesterification, which usually involves methanol or ethanol, and may be catalyzed by base (e.g., methanolysis), acid, enzymes, or heterogeneous solid catalysts.

Standard processes such as acid refining and degumming 164 can be used at the outset to remove impurities and gums, if necessary, from purchased crude oils and fats—the crude feedstock. Whether such pre-processing is necessary depends on the source and quality of purchased crude. The refining and degumming are known methods for pre-processing the crude feedstock to form prepared feedstock ready for further processing. The prepared feedstock so obtained from pre-processing includes oils and fats, and are also referred to herein as parent oils or feedstock. Some processes disclosed herein are used to reduce the FFA levels of such feedstock.

In some embodiments, the feedstock 154 may comprise at least 0.5% wt/wt FFA. First, the feedstock 154 is heated to a temperature from 90 degrees F. to 150 degrees F. The feedstock 154 may be heated to other suitable temperatures, including from 120 degrees F. to 150 degrees F., and from 140 degrees F. to 150 degrees F. Dilute caustic 158 is provided in an amount stoichiometric to the FFA content of the feedstock 154. Dilute caustic 158 may also be provided in other amounts, including 20% excess of the stoichiometric amount, 10% excess of the stoichiometric amount, and 5% excess of the stoichiometric amount. In one embodiment, a lower numbered alcohol 156 is provided in an amount of 1% to 20% wt/wt. In other embodiments, the lower numbered alcohol 156 is provided in amounts from 2% to 5% wt/wt, and from 2.5% to 3.5% wt/wt. Embodiments of lower numbered alcohol 156 include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, propylene glycol, ethylene glycol, and butylene glycol. Embodiments of the provided dilute caustic 158 include aqueous sodium hydroxide and aqueous potassium hydroxide, and may have concentrations from 2% to 15% wt/wt, from 3% to 6% wt/wt, and from 4% to 5% wt/wt.

In an embodiment, the provided lower numbered alcohol 156 and the provided dilute caustic 158 are added to the heated feedstock, resulting in a feedstock mixture, sometimes also referred to as a parent oil mixture 152. In some embodiments, the lower numbered alcohol 156 and the dilute caustic 158 are added simultaneously to the heated feedstock. In other embodiments, the lower numbered alcohol 156 and the dilute caustic 158 are added one after the other, with a preference for adding the lower numbered alcohol 156 first. The parent oil mixture 152 is stirred continuously at temperature for a period from 10 minutes to 90 minutes. After stifling, the parent oil mixture 152 is allowed to settle at temperature for a period from 60 minutes to 180 minutes. In other embodiments where the temperature is not maintained while the parent oil mixture 152 is allowed to settle, the settling period may be from 90 minutes to 4 hours. The result at the end of the settling period is two neat liquid phases. The upper phase 162 may comprise from 91.5% to 99.2% wt/wt parent oil, from 0.15% to 0.45% wt/wt FFA, from 0.05% to 0.2% wt/wt soap, and from 0.15% to 0.30% wt/wt alcohol. The lower phase 166 may comprise from 8% to 20% wt/wt soap content, from 50% to 80% wt/wt water, and from 2% to 5% wt/wt parent oil. The upper phase, now a low FFA feedstock phase, may be used to feed standard processes for producing crude biodiesel, such as acid-, base-, enzyme-, heterogeneous solid-catalyzed transesterification, and enzyme- or acid-catalyzed combined esterification/transesterification 102.

In one example, dried distiller's corn oil (DCO, less than 0.25% moisture) is the parent oil (feedstock). The DCO was obtained from an ethanol production facility. Analysis of this parent oil shows that it comprises 8.2% wt/wt FFA and no detectable level of soap. A 100 g sample of the parent oil was heated to 122° F. Then, 12.3 g of 95% wt/wt methanol (5% wt/wt water) was added to the parent oil followed by 30.5 g of 4% wt/wt dilute aqueous caustic. The mixture was stirred continuously at temperature for 20 minutes, and then allowed to settle at room temperature for two hours. Within two hours, two neat liquid phases resulted: an upper phase—the low FFA parent oil phase—comprising de-acidified corn oil and a lower phase comprising alcoholic aqueous soap. Analysis of the upper phase corn oil layer showed that it comprised 0.25% wt/wt FFA, 0.12% wt/wt soap and 0.22% wt/wt methanol, the remainder, >99% wt/wt, being the DCO parent oil. Thus, this example discloses reducing the 8.2% wt/wt FFA of a parent oil to 0.25% wt/wt under modest conditions, using inexpensive reagents and basic equipment, and in a short amount of time. The resulting upper phase low FFA corn oil layer can now be further processed, for example, as a low FFA feedstock to a standard transesterification process for producing crude biodiesel.

Other embodiments of this disclosure are directed to reducing the FFA content of the crude biodiesel. The FFA content is usually reduced during refining of the crude biodiesel in order to obtain a finished biodiesel that meets ASTM standards. The crude biodiesel 148 may be obtained via known methods, such as enzyme-, acid-, or heterogeneous solid-catalyzed transesterification of feedstock with a lower numbered alcohol such as methanol. The crude biodiesel 148 may be obtained by other known methods such as the enzyme- or acid-catalyzed combined esterification/transesterification reactions 102 with, for example, methanol. FIG. 1. The resulting crude 148 is typically allowed to settle and separated by gravity into crude ester 104 and crude glycerin 106. The crude glycerin is usually collected 108 for further processing to be sold. The crude ester 104 comprises the desired long chain alkyl ester, FFA, glycerin, alkyl alcohol, and mixed fatty glycerides, primarily monoglycerides. In one aspect of the disclosure, the amounts of the crude ester 104 components at this stage in refining are FFA at 4% wt/wt or lower; mixed fatty glycerides, primarily monoglycerides at 5% wt/wt or lower; and glycerin at 0.5% wt/wt or lower.

One aspect of the disclosure relates to removing and recovering glycerin—a major byproduct of producing crude biodiesel. According to current practice, after transesterification produces crude biodiesel, a glycerin-rich component 106 is removed after gravity separation 108. After removing crude glycerin 106, the crude ester component 104 normally retains residual glycerin. In some embodiments, the residual glycerin in the crude ester 104 is less than 1%. Although the residual glycerin can be substantially removed from the crude ester 104, for example by centrifugation, the conventional practice is to continue refining with some glycerin in the crude ester. Thus, some embodiments of this disclosure depart from the conventional practice by substantially removing the residual crude glycerin 112 by centrifugal separation 110, to be collected and further processed 108. The amount of glycerin recovered is thereby increased and preserved from subsequent salt or soap contamination. After the residual glycerin 112 is removed by centrifugal separation 110, the amount of glycerin remaining in the resulting ester 118 is significantly reduced. In some embodiments, the amount of glycerin remaining after centrifugation 110 is from 0.05% to 0.15% wt/wt. In other embodiments, the refining continues with the residual glycerin in the crude ester. That is, the residual glycerin 112 is not removed from the crude ester 104 during the process.

Embodiments directed to reducing the FFA content in refining biodiesel further include refining the ester 118 component. In some embodiments, the ester 118 comprises glycerin from 0.05% to 0.15% wt/wt, FFA from 1.75% to 4.00% wt/wt, glycerin from 0.05% to 0.15% wt/wt, and at least 93% wt/wt alkyl ester. The ester 118 further comprises glycerides, predominantly monoglycerides from 1.75% to 2.75% wt/wt, soap from 75 ppm to 100 ppm, and lower numbered alcohol from 1.2% to 2.2% wt/wt. In one embodiment, the ester 118 is heated to approximately 150 degrees Fahrenheit. The ester 118 may be heated in other embodiments to temperatures from 90 degrees Fahrenheit to 150 degrees Fahrenheit, from 120 degrees Fahrenheit to 150 degrees Fahrenheit, and from 140 degrees Fahrenheit to 150 degrees Fahrenheit. To the heated ester 118, a lower numbered alcohol 114 and dilute caustic 116 are added, resulting in a mixture 128. Dilute caustic 116 is provided in an amount stoichiometric to the FFA content of the ester 118. Dilute caustic 116 may also be provided in other amounts, including 20% excess of the stoichiometric amount, 10% excess of the stoichiometric amount, and 5% excess of the stoichiometric amount. In some embodiments the lower numbered alcohol 114 and the dilute caustic 116 are added simultaneously. In other embodiments, either the lower numbered alcohol 114 or the dilute caustic 116 is added first, with a preference for adding the lower numbered alcohol 114 first. In one embodiment, the lower numbered alcohol 114 is added in an amount of 1% to 20% wt/wt. In other embodiments, the lower numbered alcohol 114 is added in amounts from 2% to 5% wt/wt, and from 2.5% to 3.5% wt/wt. Embodiments of lower numbered alcohol 114 include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, propylene glycol, ethylene glycol, and butylene glycol. Embodiments of the dilute caustic 116 include aqueous sodium hydroxide and aqueous potassium hydroxide. Embodiments of the dilute caustic 116 may have concentrations from 2% to 15% wt/wt, from 3% to 6% wt/wt, and from 4% to 5% wt/wt.

After the lower numbered alcohol 114 and dilute caustic 116 are added, the mixture 128 is subjected to low-shear mixing at temperature, from 10 minutes to 90 minutes. The result was an unexpected two-phase demulsified mixture 120. Because conventional knowledge predicts this mixture 120 to be a gel, paste, or semi-solid, it is completely unexpected that the mixture is a neat liquid. Further, in the embodiments where the glycerin is further reduced to an amount from 0.05% to 0.15% wt/wt by centrifugation, current knowledge predicts that such a mixture 120 of the ester and FFA will be emulsified given such low glycerin content.

In an embodiment, the demulsified mixture 120 is allowed to settle at temperature for a period from 60 minutes to 180 minutes. In some embodiments, the demulsified mixture 120 is centrifuged. After either settling or centrifugation, a first phase upper component 122 is extracted, e.g., by decanting, and a second phase lower component 124 is removed by gravity, for example by draining. The first phase comprises ester having low total acid number (the “low TAN ester”) 122 and the second phase is a byproduct alcoholic aqueous soap phase 124, comprising the soap of the fatty acid and the lower numbered alcohol 114. In an embodiment, the upper component low TAN ester phase 122 comprises soap from about 200 ppm to about 600 ppm; FFA at a concentration not more than 0.25% wt/wt; mixed fatty glycerides, primarily monoglycerides from about 0.60% to about 1.00% wt/wt; alcohol from about 1.3% to about 1.7% wt/wt; at least 97% wt/wt alkyl ester; and, no detectable glycerin. Thus, the disclosed process is an easy, short, and inexpensive process to very effectively reduce FFA. Moreover, the amount of ester in the lower component alcoholic aqueous soap phase 124 is less than 2% wt/wt of the desired ester in some embodiments. Thus, the mixture 128 of ester 118, lower numbered alcohol 114, and dilute caustic 116 quickly and easily demulsifies into a two phase mixture 120, a phase that comprises a low TAN ester 122 and the another phase that comprises alcoholic aqueous soap 124. The low TAN ester 122 phase has very low soap content, and the alcoholic aqueous soap phase 124 has very little ester content.

In the embodiments wherein the residual glycerin 112 is not removed from the crude ester 104 during the process, the residual glycerin 112 becomes irreversibly contaminated with soap and/or salt later in the process. Thus, it is desirable to remove the residual glycerin 112 from the crude ester 104, for example by centrifugal separation 110, before subsequent processing.

In one embodiment of the process, residual lower numbered alcohol in the low TAN ester 122 is removed 130 by a flash vessel under the following conditions: 100 mm Hg absolute pressure and 260 degrees F. In an embodiment, the result is demethylated (“stripped”) ester 132—that is, ester with methanol removed. The stripped ester 132 in another embodiment is treated with soft water 134 to wash residual soap, resulting in a mixture of soap water 136 and wet ester 138. The soap water 136 is separated from the wet ester 138. The wet ester 138 is dried using known methods to remove water resulting in the finished biodiesel 140. Acid 142 is added to the soap water 136 to recover the free fatty acids 126, which are returned for further processing 144. Embodiments of suitable acids include sulfuric acid 142, hydrochloric acid, acetic acid, citric acid, phosphoric acid, sulfuric acid, and methanesulfonic acid. Similarly, acid is also added to the alcoholic aqueous soap 124 according to some embodiments, resulting in free fatty acids 126, which are recycled 144, and waste water 146. The waste water 146 is discarded.

In one example, 2000 g ester 118 was obtained after centrifugation 110 of the crude ester 104 for 9 minutes at 2000 rpm. The ester 118 composition comprised FFA at 2.25% wt/wt, monoglycerides at 2.20% wt/wt, diglycerides at 0.11% wt/wt, free glycerin at 0.091% wt/wt, methanol at 1.656% wt/wt, moisture at 0.0375% (375 ppm), and alkyl ester in remaining balance. The ester 118 was heated to 150 degrees F. 60.0 g of 95% wt/wt methanol (5% wt/wt water) and 4% wt/wt sodium hydroxide were added sequentially while stifling. Temperature was maintained at 150 degrees F. and the mixture was stirred moderately (200 rpm with a magnetic stir bar) and continuously for 35 minutes. The mixture was then allowed to settle for two hours while maintained at 150 degrees F. Within two hours, two neat liquid phases with clear separation had resulted. A lower aqueous soap phase had a total mass of 314.1 g, comprised soap content at 16.9% wt/wt and moisture at 54% wt/wt, and had a saponification value of 13.9 mg KOH/g sample, which is about 7% esters, primarily monoglycerides and the balance methyl esters. An upper ester phase had a total mass of about 1685.8, and comprised FFA at 0.2% wt/wt, soap at 0.0250% wt/wt (250 ppm), moisture at 2000 ppm, monoglycerides at 0.78% wt/wt, diglycerides at 0.02% wt/wt, methanol at 1.52% wt/wt, and no detectable levels of glycerin. Thus, this example discloses reducing the FFA of a crude ester to 0.2% wt/wt under modest conditions, using inexpensive reagents and basic equipment, and in a short amount of time. The resulting upper ester phase—the low TAN ester 122—reduces the FFA content to a level that meets ASTM specifications. The low TAN ester can now be further refined, for example, to remove methanol 130, to wash with soft water 134 to separate the soap water 136, and to dry to produce the finished biodiesel 140.

In a second example, another 2000 g batch of ester 118 was obtained after centrifugation 110 of the crude ester 104 for 9 minutes at 2000 rpm. The ester 118 composition comprised FFA at 1.9% wt/wt, monoglycerides at 1.449% wt/wt, methanol at 0.635% wt/wt. 100 g of the ester was heated to 120 degrees F. 4.0 g of 95% wt/wt methanol (balance water) was added, followed by 10.4 g of 4% wt/wt aqueous potassium hydroxide. The mixture was allowed to stir moderately (200 rpm with a magnetic stir bar) and continuously for 20 minutes. The mixture was then allowed to separate for four hours at room temperature. Within those four hours, two neat liquid phases formed. The resulting upper ester phase—the low TAN ester 122—comprised FFA at 0.2% wt/wt, soap at 550 ppm, monoglycerides at 0.71% wt/wt, and methanol at 0.81% wt/wt. This example discloses reducing FFA of a crude ester to a level that meets ASTM specifications.

In a third example, 100 g of a crude ester 104 was centrifuged for 9 minutes at 2000 rpm. The resulting ester 118 comprised FFA at 1.9% wt/wt, monoglycerides at 1.449% wt/wt, methanol at 0.635% wt/wt, and was heated to 120 degrees F. 5.0 g of 70% propylene glycol (balance water) was added, followed by 7.45 g of 4% wt/wt aqueous sodium hydroxide. The mixture was allowed to stir moderately (200 rpm with a magnetic stir bar) and continuously for 20 minutes. The mixture was then allowed to separate for four hours at room temperature. Within those four hours, two neat liquid phases formed. The resulting upper ester phase—the low TAN ester 122—comprised FFA at 0.15% wt/wt, soap at 500 ppm, monoglycerides at 0.49% wt/wt, and methanol at 0.04% wt/wt. This example discloses reducing FFA of a crude ester to a level that meets ASTM specifications.

When introducing elements of aspects of the invention or the embodiments thereof, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

As various changes could be made in the above processes and products without departing from the scope of aspects of this disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims

1. A process for refining, the process comprising:

providing a first mixture comprising free fatty acid, alkyl ester, and mixed fatty glycerides, wherein the amount of mixed fatty glycerides is no more than 5% wt/wt;

providing lower numbered alcohol;

providing dilute caustic; and,

adding the lower numbered alcohol and the dilute caustic to the first mixture resulting in a second mixture.

2. The process of claim 1, wherein the first mixture further comprises glycerin, the process further comprising separating glycerin from the first mixture.

3. The process of claim 2 further comprising centrifuging the first mixture prior to separating glycerin from the first mixture.

4. The process of claim 1 further comprising heating the first mixture to a temperature from 90 degrees F. to 150 degrees F.

5. The process of claim 1 further comprising heating the first mixture to a temperature from 120 degrees F. to 150 degrees F.

6. The process of claim 1 further comprising heating the first mixture to a temperature from 140 degrees F. to 150 degrees F.

7. The process of claim 4 wherein the first mixture is heated to temperature before the lower numbered alcohol and the dilute caustic are added to the first mixture.

8. The process of claim 7 further comprising agitation of the second mixture.

9. The process of claim 8 wherein the agitation is a low-shear mixing.

10. The process of claim 9 further comprising allowing the second mixture to settle into a first phase upper component and a second phase lower component.

11. The process of claim 10 wherein the settling occurs at temperature.

12. The process of claim 10 wherein the settling occurs at room temperature.

13. The process of claim 9 wherein the second mixture settles into a first phase upper component and a second phase lower component.

14. The process of claim 11 wherein the first phase comprises alkyl ester, and the second phase comprises alcoholic aqueous soap.

15. The process of claim 11 further comprising separating the first phase from the second phase.

16. The process of claim 1 wherein the first mixture is neutral.

17. The process of claim 1 wherein the first mixture is acidic.

18. The process of claim 1 wherein the lower numbered alcohol is selected from a group comprising: methanol, ethanol, propanol, isopropanol, butanol, isobutanol, propylene glycol, ethylene glycol, and butylene glycol.

19. The process of claim 1 wherein the dilute caustic is selected from a group comprising: NaOH and KOH.

20. The process of claim 1 wherein the lower numbered alcohol and the dilute caustic are added simultaneously.

21. The process of claim 1 wherein the lower numbered alcohol and the dilute caustic are added sequentially.

22. The process of claim 21 wherein the lower numbered alcohol is added before adding the dilute caustic.

23. The process of claim 15 wherein:

the amount of dilute caustic provided is from stoichiometric to the amount of free fatty acid in the first mixture to 20% excess of the stoichiometric amount;

the concentration of the dilute caustic provided is from 2% to 15% wt/wt; and,

the amount of lower numbered alcohol provided is from 1% to 20% wt/wt.

24. The process of claim 15 wherein:

the amount of dilute caustic provided is from stoichiometric to the amount of free fatty acid in the first mixture to 10% excess of the stoichiometric amount;

the concentration of the dilute caustic provided is from 3% to 6% wt/wt; and,

the amount of lower numbered alcohol provided is from 2% to 5% wt/wt.

25. The process of claim 15 wherein:

the amount of dilute caustic provided is from stoichiometric to the amount of free fatty acid in the first mixture to 5% excess of the stoichiometric amount;

the concentration of the dilute caustic provided is from 4% to 5% wt/wt; and,

the amount of lower numbered alcohol provided is from 2.5% to 3.5% wt/wt.

26. The process of claim 15 wherein the second mixture settling into a first phase upper component and a second phase lower component is achieved by centrifuging the second mixture.

27. The process of claim 15 wherein the separating comprises removing the lower component from second mixture.

28. The process of claim 15 wherein the separating comprises decanting the upper component from the second mixture.

29. The process of claim 27 wherein the lower component comprises alcoholic aqueous soap.

30. The process of claim 29 further comprising reacting acid with the alcoholic aqueous soap.

31. The process of claim 30 wherein the acid is selected from a group comprising:

hydrochloric acid, acetic acid, citric acid, phosphoric acid, sulfuric acid, and methanesulfonic acid.

32. The process of claim 30 further comprising recovering free fatty acids formed by the reaction.

33. The process of claim 30 further comprising removing alcoholic water.

34. The process of claim 15 wherein the separating comprises removing the upper component from the second mixture and wherein the removed upper component comprises a third mixture.

35. The process of claim 34 wherein the third mixture comprises alkyl ester having total acid number less than or equal to 0.5.

36. The process of claim 35 further comprising:

washing the third mixture with soft water to form a resultant mixture, wherein the resultant mixture comprises soap water and wet ester; and,

removing the soap water from the resultant mixture.

37. The process of claim 35 further comprising removing residual lower numbered alcohol from the third mixture to form a fourth mixture.

38. The process of claim 37 wherein the fourth mixture comprises a purified alkyl ester, and trace amounts of monoglycerides, soap, residual lower numbered alcohol.

39. The process of claim 38 further comprising washing the fourth mixture with soft water resulting in a fifth mixture, wherein the fifth mixture comprises two components.

40. The process of claim 39 wherein the fifth mixture comprises a wet ester component and a soap water component.

41. The process of claim 40 further comprising removing the soap water component from the fifth mixture.

42. The process of claim 41 further comprising:

removing the wet ester component from the fifth mixture; and,

drying the wet ester component.

43. The process of claim 41 further comprising adding acid to the removed soap water component to form a sixth mixture.

44. The process of claim 43 wherein the acid is selected from a group comprising hydrochloric acid, acetic acid, citric acid, phosphoric acid, sulfuric acid, and methanesulfonic acid.

45. The process of claim 43 wherein the sixth mixture comprises re-formed fatty acids and waste water, the process further comprising recovering the free fatty acids.

46. The process of claim 45 further comprising removing the waste water from the sixth mixture.

47. A composition for refining, the composition comprising:

a lower numbered alcohol, wherein the lower numbered alcohol is selected from a group comprising: methanol, ethanol, propanol, isopropanol, butanol, isobutanol, propylene glycol, ethylene glycol, and butylene glycol;

a dilute caustic, wherein the dilute caustic is selected from a group comprising NaOH and KOH; and

a crude biodiesel product, wherein the crude biodiesel product comprises: free fatty acid at a concentration of not more than 10% wt/wt; monoglycerides at a concentration of not more than 5% wt/wt; glycerin at a concentration of not more than 1% wt/wt; alcohol at a concentration of not more than 10% wt/wt; and alkyl ester at a concentration of not more than 95% wt/wt.

48. The composition of claim 47 wherein the crude biodiesel product comprises products of transesterification of triglycerides.

49. The composition of claim 47 wherein the crude biodiesel product comprises products of combined esterification/transesterification reactions.

50. The composition of claim 47 wherein:

the amount of the dilute caustic is from stoichiometric to the amount of free fatty acid in the crude product to 20% excess of the stoichiometric amount;

the concentration of the dilute caustic is from 2% to 15% wt/wt; and

the amount of lower numbered alcohol is from 1% to 20% wt/wt.

51. The composition of claim 47 wherein:

the amount of the dilute caustic is from stoichiometric amount to the amount of free fatty acid in the crude product to 10% excess of the stoichiometric amount;

the concentration of the dilute caustic is from 3% to 6% wt/wt; and

the amount of lower numbered alcohol is from 2% to 5% wt/wt.

52. The composition of claim 47 wherein:

the amount of the dilute caustic is from stoichiometric to the amount of free fatty acid in the crude product to 5% excess of the stoichiometric amount;

the concentration of the dilute caustic is from 4% to 5% wt/wt; and

the amount of lower numbered alcohol is from 2.5% to 3.5% wt/wt.

53. A composition for reducing free fatty acid, the composition comprising:

a lower numbered alcohol,

a dilute caustic; and,

wherein: the lower numbered alcohol is selected from a group comprising: methanol, ethanol, propanol, isopropanol, butanol, isobutanol, propylene glycol, ethylene glycol, and butylene glycol; the dilute caustic is selected from a group comprising: NaOH and KOH.

54. The composition of claim 53 further comprising at least one feedstock, wherein the feedstock is selected from a group comprising: distiller's corn oil, castor oil, soybean oil, jatropha oil, algae oil, yellow grease, brown grease, lard, and beef tallow.

55. The composition of claim 53 further comprising a crude product of combined esterification/transesterification of triglycerides, wherein the crude product comprises:

free fatty acid at a concentration not more than 10% wt/wt;

monoglycerides at a concentration not more than 5% wt/wt;

alcohol at a concentration not more than 10% wt/wt; and

alkyl ester at a concentration not more than 95% wt/wt.

56. The composition of claim 53 wherein the crude product further comprises glycerin at a concentration not more than 1% wt/wt.

57. The composition of claim 55 wherein:

the amount of the dilute caustic is from stoichiometric to the amount of free fatty acid in the crude product to 20% excess of the stoichiometric amount;

the concentration of the dilute caustic is from 2% to 15% wt/wt; and

the amount of lower numbered alcohol is from 1% to 20% wt/wt.

58. The composition of claim 55 wherein:

the amount of the dilute caustic is from stoichiometric to the amount of free fatty acid in the crude product to 10% excess of the stoichiometric amount;

the concentration of the dilute caustic is from 3% to 6% wt/wt; and

the amount of lower numbered alcohol is from 2% to 5% wt/wt.

59. The composition of claim 55 wherein:

the amount of the dilute caustic is from stoichiometric to the amount of free fatty acid in the crude product to 5% excess of the stoichiometric amount;

the concentration of the dilute caustic is from 4% to 5% wt/wt; and

the amount of lower numbered alcohol is from 2.5% to 3.5% wt/wt.

60. A composition for refining, the composition comprising alkyl ester and alcoholic aqueous soap.

61. The composition of claim 60 further comprising two non-emulsified phases, wherein the first phase comprises the alkyl ester, and the second phase comprises the soap.

62. The composition of claim 61 wherein the first phase further comprises soap, free fatty acid, glycerin, alcohol, monoglycerides, wherein the amount of:

free fatty acid is from 0.1% to 0.3% wt/wt;

glycerin is not detectable;

alcohol is from 1% to 2% wt/wt;

monoglycerides is no more than 1.5% wt/wt; and,

alkyl ester is at least 94% wt/wt.

63. The composition of claim 61 wherein the second phase further comprises alkyl ester, glycerin, wherein the amount of alkyl ester is no more than 10% wt/wt, and the amount of glycerin is no more than 2% wt/wt.

64. A composition for refining, the composition comprising alkyl ester, soap, free fatty acid, glycerin, and alcohol, wherein the amount of:

free fatty acid is from 1.75% to 2.75% wt/wt;

glycerin is from 0.05% to 0.15% wt/wt;

alcohol is from 1% to 2% wt/wt; and,

alkyl ester is at least 93% wt/wt.

65. The composition of claim 64 wherein the amount of the alkyl ester is from 85% to 97% wt/wt.

66. The composition of claim 64 wherein the concentration of:

free fatty acid is not more than 4% wt/wt;

glycerin is not more than 0.5% wt/wt;

alcohol is not more than 3% wt/wt; and,

alkyl ester is at least 85% wt/wt.

67. A process for reducing free fatty acid in a parent oil, the process comprising:

providing a parent oil, wherein the parent oil comprises free fatty acid, wherein the concentration of the free fatty acid is at least 0.5% wt/wt;

providing lowered numbered alcohol;

providing dilute caustic; and,

adding the lower numbered alcohol and the dilute caustic to the parent oil to form a parent oil mixture.

68. The process of claim 67 wherein the lower numbered alcohol is selected from a group comprising: methanol, ethanol, propanol, isopropanol, butanol, isobutanol, propylene glycol, ethylene glycol, and butylene glycol.

69. The process of claim 67 wherein the parent oil is selected from a group comprising distiller's corn oil, castor oil, soybean oil, jatropha oil, algae oil, yellow grease, brown grease, lard, and beef tallow.

70. The process of claim 69 further comprising

heating the feedstock to form a heated feedstock from 90 degrees Fahrenheit to 150 degrees Fahrenheit;

continuously stirring the parent oil mixture for a period from 10 minutes to 2 hours; and,

allowing the parent oil mixture to settle to form a neat liquid with two phases, wherein: the first phase comprises feedstock and free fatty acid, wherein the free fatty acid is at a concentration not more than 0.4% wt/wt; the second phase comprises alcoholic aqueous soap; and the lower numbered alcohol and the dilute caustic are added to the heated feedstock to form the parent oil mixture.

71. The process of claim 70 wherein the lower numbered alcohol and the dilute caustic are added simultaneously.

72. The process of claim 70 wherein the lower numbered alcohol and the dilute caustic are added sequentially.

73. The process of claim 72 wherein the lower numbered alcohol is added before adding the dilute caustic.

74. The process of claim 70 wherein the stifling is a low-shear mixing.

75. The process of claim 70 wherein:

the feedstock is heated to a temperature from 120 degrees Fahrenheit to 150 degrees Fahrenheit;

the stifling period is from 10 minutes to 1 hour;

the amount of dilute caustic provided is from stoichiometric to the amount of free fatty acid in the feedstock to 20% excess of the stoichiometric amount;

the concentration of the dilute caustic provided is from 2% to 15% wt/wt;

the amount of lower numbered alcohol provided is from 1% to 20% wt/wt.

76. The process of claim 70 wherein the dilute caustic is selected from a group comprising: NaOH and KOH.

77. The process of claim 70 wherein:

the feedstock is heated to a temperature from 140 degrees Fahrenheit to 150 degrees Fahrenheit;

the stifling period is from 10 minutes to 30 minutes;

the amount of dilute caustic provided is from stoichiometric to the amount of free fatty acid in the feedstock to 10% excess of the stoichiometric amount;

the concentration of the dilute caustic provided is from 3% to 6% wt/wt;

the amount of lower numbered alcohol provided is from 2% to 5% wt/wt.

78. The process of claim 77 wherein:

the amount of dilute caustic provided is from stoichiometric to the amount of free fatty acid in the feedstock to 5% excess of the stoichiometric amount;

the concentration of the dilute caustic provided is from 4% to 5% wt/wt;

the amount of lower numbered alcohol provided is from 2.5% to 3.5% wt/wt.

79. The process of claim 70 wherein the parent oil mixture is allowed to settle at room temperature.

80. The process of claim 70 wherein the parent oil mixture is allowed to settle at temperature.

81. The process of claim 70 wherein the parent oil mixture is allowed to settle for a period of 60 minutes to 4 hours.

82. The process of claim 70 wherein the parent oil mixture separates into a first upper phase and a second lower phase.

83. The process of claim 82 wherein the first upper phase comprises:

parent oil from 91.5% to 99.2% wt/wt;

free fatty acid from 0.15% to 0.45% wt/wt;

soap from 0.05% to 0.2% wt/wt; and,

lower numbered alcohol from 0.15% to 0.30% wt/wt.

84. The process of claim 82 wherein the second lower phase comprises:

soap from 8% to 20% wt/wt;

water from 50% to 80% wt/wt; and,

parent oil from 2% to 5% wt/wt.

85. The process of claim 82 further comprising extracting the first upper phase by decanting.

86. The process of claim 70 further comprising providing more than 1 parent oil.