WO2015183744A1 - Réduction de la teneur en acides gras d'une charge d'alimentation et d'un ester alkylique neutre et acide - Google Patents

Réduction de la teneur en acides gras d'une charge d'alimentation et d'un ester alkylique neutre et acide Download PDF

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Publication number
WO2015183744A1
WO2015183744A1 PCT/US2015/032226 US2015032226W WO2015183744A1 WO 2015183744 A1 WO2015183744 A1 WO 2015183744A1 US 2015032226 W US2015032226 W US 2015032226W WO 2015183744 A1 WO2015183744 A1 WO 2015183744A1
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Prior art keywords
mixture
amount
dilute caustic
alcohol
free fatty
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PCT/US2015/032226
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English (en)
Inventor
Kerry Staller
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Blue Sun Energy, Inc.
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Publication of WO2015183744A1 publication Critical patent/WO2015183744A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L1/00—Liquid carbonaceous fuels
    • C10L1/02—Liquid carbonaceous fuels essentially based on components consisting of carbon, hydrogen, and oxygen only
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L1/00—Liquid carbonaceous fuels
    • C10L1/02—Liquid carbonaceous fuels essentially based on components consisting of carbon, hydrogen, and oxygen only
    • C10L1/026—Liquid carbonaceous fuels essentially based on components consisting of carbon, hydrogen, and oxygen only for compression ignition
    • C—CHEMISTRY; METALLURGY
    • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
    • C11C—FATTY ACIDS FROM FATS, OILS OR WAXES; CANDLES; FATS, OILS OR FATTY ACIDS BY CHEMICAL MODIFICATION OF FATS, OILS, OR FATTY ACIDS OBTAINED THEREFROM
    • C11C1/00—Preparation of fatty acids from fats, fatty oils, or waxes; Refining the fatty acids
    • C11C1/08—Refining
    • C—CHEMISTRY; METALLURGY
    • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
    • C11C—FATTY ACIDS FROM FATS, OILS OR WAXES; CANDLES; FATS, OILS OR FATTY ACIDS BY CHEMICAL MODIFICATION OF FATS, OILS, OR FATTY ACIDS OBTAINED THEREFROM
    • C11C1/00—Preparation of fatty acids from fats, fatty oils, or waxes; Refining the fatty acids
    • C11C1/08—Refining
    • C11C1/10—Refining by distillation
    • C11C1/103—Refining by distillation after or with the addition of chemicals
    • C—CHEMISTRY; METALLURGY
    • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
    • C11C—FATTY ACIDS FROM FATS, OILS OR WAXES; CANDLES; FATS, OILS OR FATTY ACIDS BY CHEMICAL MODIFICATION OF FATS, OILS, OR FATTY ACIDS OBTAINED THEREFROM
    • C11C3/00—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom
    • C11C3/003—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom by esterification of fatty acids with alcohols
    • C—CHEMISTRY; METALLURGY
    • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
    • C11C—FATTY ACIDS FROM FATS, OILS OR WAXES; CANDLES; FATS, OILS OR FATTY ACIDS BY CHEMICAL MODIFICATION OF FATS, OILS, OR FATTY ACIDS OBTAINED THEREFROM
    • C11C3/00—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom
    • C11C3/04—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom by esterification of fats or fatty oils
    • C11C3/10—Ester interchange
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L2200/00—Components of fuel compositions
    • C10L2200/04—Organic compounds
    • C10L2200/0461—Fractions defined by their origin
    • C10L2200/0469—Renewables or materials of biological origin
    • C10L2200/0476—Biodiesel, i.e. defined lower alkyl esters of fatty acids first generation biodiesel
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L2270/00—Specifically adapted fuels
    • C10L2270/02—Specifically adapted fuels for internal combustion engines
    • C10L2270/026—Specifically adapted fuels for internal combustion engines for diesel engines, e.g. automobiles, stationary, marine
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
    • C10L2290/06—Heat exchange, direct or indirect
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
    • C10L2290/08—Drying or removing water
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
    • C10L2290/24—Mixing, stirring of fuel components
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
    • C10L2290/54—Specific separation steps for separating fractions, components or impurities during preparation or upgrading of a fuel
    • C10L2290/544—Extraction for separating fractions, components or impurities during preparation or upgrading of a fuel
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E50/00—Technologies for the production of fuel of non-fossil origin
    • Y02E50/10—Biofuels, e.g. bio-diesel
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/582—Recycling of unreacted starting or intermediate materials

Definitions

  • This disclosure relates to processes for refining biodiesel and to compositions in the refining process.
  • 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.
  • 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 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
  • 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.
  • 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.
  • 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).
  • alkyl esters the crude biodiesel
  • alcohols alcohols
  • glycerin glycerides
  • glycerides randominantly 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.
  • 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.
  • lower numbered alcohol refers to a lower alkyl alcohol or lower alkyl diol. Examples of lower numbered alcohols include methanol and propylene glycol.
  • alkyl ester(s) refers to "mono-alkyl ester(s) of lower numbered alcohols”.
  • austic refers to an alkali metal hydroxide.
  • 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.
  • 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 stirring 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.
  • 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.
  • 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.
  • the parent oil mixture may be continuously stirred for a period from 10 minutes to 1 hour, or from 10 minutes to 2 hours.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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 stirring moderately at 200 rpm with a magnetic stir bar. After the mixing, in one embodiment, the second mixture is centrifuged.
  • 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.
  • the upper phase comprises alkyl ester
  • the lower phase comprises alcoholic aqueous soap.
  • the two phases are separated by decantation.
  • disclosed processes are directed to recovering FFA from the refining process above.
  • 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.
  • acid such as hydrochloric acid, acetic acid, citric acid, phosphoric acid, sulfuric acid, and methanesulfonic acid.
  • processes are directed to recovering the lower numbered alcohol used above.
  • 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.
  • FIG. la is a diagram of some aspects related to reducing free fatty acid in feedstock.
  • FIG. lb is a diagram of aspects related to reducing free fatty acid in feedstock.
  • FIG. lc is a diagram of some aspects related to reducing free fatty acid in neutral or acidic alkyl ester, and recovering reagents.
  • FIG. Id is a diagram of aspects related to reducing free fatty acid in neutral or acidic alkyl ester, and recovering reagents.
  • FIG. le is a diagram of aspects related to recovering reagents in reducing free fatty acid in alkyl ester.
  • 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.
  • FFA free fatty acid
  • 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 preprocessing 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.
  • the feedstock 154 may comprise at least 0.5% wt/wt
  • 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.
  • a lower numbered alcohol 156 is provided in an amount of 1% to 20% wt/wt.
  • 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.
  • 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.
  • the lower numbered alcohol 156 and the dilute caustic 158 are added simultaneously to the heated feedstock.
  • 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 stirring, the parent oil mixture 152 is allowed to settle at temperature for a period from 60 minutes to 180 minutes.
  • 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.
  • standard processes for producing crude biodiesel such as acid-, base-, enzyme-, heterogeneous solid-catalyzed transesterification, and enzyme- or acid-catalyzed combined esterification / transesterification 102.
  • 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 lOOg sample of the parent oil was heated to 122°F. Then, 12.3g of 95% wt/wt methanol (5% wt/wt water) was added to the parent oil followed by 30.5g 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.
  • 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.
  • 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.
  • 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.
  • the residual glycerin in the crude ester 104 is less than 1%.
  • the conventional practice is to continue refining with some glycerin in the crude ester.
  • 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.
  • the residual glycerin 112 is removed by centrifugal separation 110, the amount of glycerin remaining in the resulting ester 118 is significantly reduced.
  • the amount of glycerin remaining after centrifugation 110 is from 0.05% to 0.15% wt/wt.
  • 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.
  • 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.
  • 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.
  • 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.
  • the lower numbered alcohol 114 and the dilute caustic 116 are added simultaneously.
  • 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.
  • the lower numbered alcohol 114 is added in an amount of 1% to 20% wt/wt.
  • 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.
  • 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.
  • the demulsified mixture 120 is allowed to settle at temperature for a period from 60 minutes to 180 minutes.
  • 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.
  • 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.
  • the disclosed process is an easy, short, and inexpensive process to very effectively reduce FFA.
  • 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.
  • 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
  • the alcoholic aqueous soap phase 124 has very little ester content.
  • the residual glycerin 112 becomes irreversibly contaminated with soap and / or salt later in 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.
  • 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.
  • suitable acids include sulfuric acid 142, hydrochloric acid, acetic acid, citric acid, phosphoric acid, sulfuric acid, and methanesulfonic acid.
  • 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.
  • 2000g 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.
  • a lower aqueous soap phase had a total mass of 314.1g, comprised soap content at 16.9% wt/wt and moisture at 54% wt/wt, and had a saponification value of 13.9mg 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 2000ppm, monoglycerides at 0.78% wt/wt, diglycerides at 0.02% wt/wt, methanol at 1.52% wt/wt, and no detectable levels of glycerin.
  • 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.
  • Another 2000g 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.
  • 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. 5.0g of 70% propylene glycol (balance water) was added, followed by 7.45g 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.

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Abstract

L'invention concerne des procédés et des compositions qui réduisent la teneur en acide gras libres (AGL) dans des huiles et des graisses, et dans un ester alkylique neutre ou acide. Les huiles et les graisses ou l'ester alkylique sont chauffés à des températures comprises entre 90 °F et 150 °F, et un alcool inférieur et de la soude caustique diluée sont ajoutés. Le mélange est agité modérément, et laissé à décanter en deux phases − une phase d'AGL et une seconde phase à faible teneur en AGL contenant des huiles et des graisses, ou un ester d'alkyle. Les deux phases sont séparées. La récupération de la glycérine et des alcools inférieurs est augmentée. Certaines compositions permettant de réduire la teneur en AGL comprennent un alcool inférieur et de la soude caustique diluée. Les procédés et les compositions réduisent les teneurs en AGL pour respecter les normes sur les carburants.
PCT/US2015/032226 2014-05-30 2015-05-22 Réduction de la teneur en acides gras d'une charge d'alimentation et d'un ester alkylique neutre et acide WO2015183744A1 (fr)

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BRPI0415072B1 (pt) * 2003-10-09 2020-11-03 The Dallas Group Of America, Inc método de purificação de um combustível biodiesel com materiais adsorventes
ATE435919T1 (de) * 2004-11-09 2009-07-15 Cognis Ip Man Gmbh Herstellung von biodiesel aus seifenausgangsmaterial

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Publication number Priority date Publication date Assignee Title
EP3404082A1 (fr) 2017-05-19 2018-11-21 GEA Mechanical Equipment GmbH Procédé de réduction de la teneur en monoglycérides (mg), notamment en monoglycérides saturés (gmg) dans un biodiesel brut
WO2018210573A1 (fr) 2017-05-19 2018-11-22 Gea Mechanical Equipment Gmbh Procédé pour la diminution de la teneur en monoglycérides saturés dans un biodiesel brut
US10982159B2 (en) 2017-05-19 2021-04-20 Gea Mechanical Equipment Gmbh Method for reducing the content of saturated monoglycerides in a raw biodiesel

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