Methods for making free fatty acids from soaps using thermal hydrolysis followed by acidification

Abstract

Provided are methods, processes and systems for treating a soapstock. In alternative embodiments, provided are systems and methods for treating a soapstock to generate free fatty acids and/or fatty acid derivatives, e.g. fatty acid alkyl esters. In alternative embodiments, provided are systems and methods for realizing the full fatty acid yield of a soapstock by first converting substantially all of the saponifiable material in a soapstock to salts of fatty acids (soaps) and acidulating the soaps to generate free fatty acids and/or fatty acid derivatives, e.g. fatty acid alkyl esters, wherein the soapstock comprises soaps and saponifiable lipids, e.g. glycerides and/or phospholipids, and the generating of free fatty acids and/or fatty acid is achieved.

1 . A method for generating free fatty acids from a mixed lipid feedstock using a thermal hydrolysis reaction, the method comprising:
 (a) providing an aqueous solution or mixture comprising a mixed lipid feedstock, and
 wherein optionally the mixed lipid feedstock comprises: a soapstock; a triglyceride comprising material; a saponifiable material, optionally a glyceride or a phospholipid; a tall oil, 
 wherein optionally the tall oil comprises a liquid rosin tall oil, a soapstock; a gums product, optionally a chemically or enzymatically derived gums product; a crude biodiesel; a fatty acid, optionally from a distillation bottom; a fat splitter emulsion, optionally purged from fat splitter due to accumulation when recycled; or, any combination thereof, 
 and optionally the mixed lipid feedstock comprises a soapstock, a wash-water comprising soaps or a combination thereof, optionally generated during the chemical refining of a crude natural oil, 
 and optionally the mixed lipid feedstock is derived from a biomass, a crude natural oil, or a plant or an animal source, optionally a tallow; 
 and optionally the mixed lipid feedstock is derived from enzymatic degumming of edible and inedible oils; and 
   (b) heating and pressurizing the aqueous solution or mixture comprising the mixed lipid feedstock in a thermal hydrolysis reaction under conditions comprising sufficient pressure and temperature to generate a first reaction mixture comprising a free fatty acid and/or a soap, optionally a fatty acid salt, and/or a glyceride, optionally a monoacylglycerol (MAG), a diacylglycerol (DAG), or a triacylglycerol (TAG),   wherein the thermal hydrolysis reaction is carried out at a temperature in the range of between about 20° C. to about 600° C., and at a pressure of between about 300 to about 2000 psig (about 20.7 bar to about 137.9 bar), and for between about 1 second (sec) to about 3000 minutes (min), or between about 1 min to about 300 min, or between about 5 min to 200 min,   and optionally the amount of water in the thermal hydrolysis reaction is between about 2:1 water-to-total dissolved solids (TDS) present in the mixed lipid feedstock to about 15:1 TDS, or about 10:1 TDS; or between about 1:1 TDS present in the mixed lipid feedstock to about 100:1 TDS,   and optionally a solvent is added to the thermal hydrolysis reaction in an amount of between about 0.01:1 water-to-total dissolved solids (TDS) present in the mixed lipid feedstock to about 100:1 TDS, or about 10:1 TDS.   
     
     
         2 . The method of  claim 2 , further comprising:
 (a) an acidification reaction that takes place after or during or simultaneous with the thermal hydrolysis step, comprising:   (1) providing an acid or an acid solution or a gas capable of forming an acid when mixed with water, optionally a carbon dioxide (CO 2 ) or a stack gas; and   (2) combining or mixing the first reaction mixture with the acid or acid solution or the gas, optionally CO 2 , or mixing the first reaction mixture with the acid or acid solution or the gas, optionally CO 2 , to have an acidulation reaction and to generate a second reaction mixture, wherein the first reaction mixture is combined or mixed with the acid or acid solution or the gas, optionally CO 2 , for a sufficient amount of time to acidulate, optionally partially, or substantially all of, the soap in the first reaction mixture to generate free fatty acids from the acidulated soaps,   and optionally the pH of the acidulation reaction mixture is less than about pH 5, or is between about pH 1 to pH 6, or is about pH 1, 2, 3, 4, 5 or 6,   and optionally the amount of the gas is sufficient to increase the pressure of the reaction mixture, optionally in a reaction vessel, in which the acidulation reaction is being carried out to between about 0 and about 2000 psig.   (b) the method of (a), further comprising mixing the second reaction mixture with an alcohol to form a third reaction mixture comprising fatty acid alkyl esters,
 wherein optionally the mixing is done under conditions comprising between about 240° C. to about 350° C., or 200° C. to 400° C., and a pressure of between about 1400 psi to about 3000 psi, 
 and optionally substantially all of the free fatty acids are esterified to generate fatty acid alkyl esters, optionally, fatty acid methyl esters, 
 and optionally the alcohol comprises methanol, ethanol or a mixture thereof; 
   (c) the method of (a) or (b), further comprising separating, isolating, and/or purifying the free fatty acids and/or the fatty acid alkyl esters into separate fractions; or   (d) a pre-treatment acidification reaction step for treating the mixed lipid feedstock before the thermal hydrolysis reaction, wherein the pre-treatment acidification reaction step comprises:   (1) (i) providing an acid or an acid solution or a gas capable of forming an acid when mixed with water, optionally a carbon dioxide (CO 2 ) or a stack gas; and   (ii) combining or mixing the mixed lipid feedstock with the acid or acid solution or the gas, optionally CO 2 , or mixing the mixed lipid feedstock with the acid or acid solution or the gas, optionally CO 2 , to have an acidulation reaction and to generate a pre-treated mixed lipid feedstock, wherein the mixed lipid feedstock is combined or mixed with the acid or acid solution or the gas, optionally CO 2 , for a sufficient amount of time to acidulate, optionally partially, or substantially all of, the soap in the mixed lipid feedstock; or   (2) electrolysis, optionally using a hydrogen evolving cathode (HEC) electrolysis unit, of the mixed lipid feedstock for a sufficient amount of time to acidulate, optionally partially, or substantially all of, the soap in the mixed lipid feedstock,   and optionally the pH of the pre-treatment acidulation reaction mixture is less than about pH 5, or is between about pH 1 to pH 6, or is about pH 1, 2, 3, 4, 5 or 6,   and optionally the amount of the gas is sufficient to increase the pressure of the pre-treatment reaction mixture, optionally in a reaction vessel, in which the pre-treatment acidulation reaction is being carried out to between about 0 and about 2000 psig.   
     
     
         3 . The method of  claim 1 , wherein the natural oil or crude natural oil comprises a vegetable oil, wherein optionally the vegetable oil comprises a soybean oil, a canola oil, a rapeseed oil, a corn oil, a rice oil, a sunflower oil, a peanut oil, a sesame oil, a palm oil, an algae oil, a jatropha oil, a castor oil, a safflower oil, a grape seed oil or any combination thereof,
 and optionally the natural oil or crude natural oil comprises castor oil, and optionally a free fatty acid generated is ricinoleic acid (12-hydroxy-9-cis-octadecenoic acid).   
     
     
         4 . The method of  claim 1 , wherein the mixed lipid feedstock further comprises additional water, a phospholipid and/or an unsaponifiable material. 
     
     
         5 . The method of  claim 2 , wherein the acid or acid solution comprises carbonic acid, and optionally the carbonic acid is generated by adding carbon dioxide (CO 2 ) to the first reaction mixture, thereby causing the carbon dioxide to react with water in the first reaction mixture to form carbonic acid,
 and optionally a source of the carbon dioxide (CO 2 ) comprises a stack gas or a flue gas, or a gaseous CO 2  emitted from an industrial process or an oven, a furnace, a boiler, a steam generator, a coal fired power plant, an ethanol plant, a brewery, or an industrial process wherein a gaseous waste stream comprising CO 2  is emitted,   and optionally the carbon dioxide is added to the first reaction mixture, optionally as a liquid, a carbon dioxide gas, or as a gaseous flow of carbon dioxide into the reaction vessel.   
     
     
         6 . The method of  claim 1 , wherein the heating and pressurizing of the mixed lipid feedstock is done in a single vessel, or sequential, different, reaction vessels; and optionally the pre-treatment and the thermal hydrolysis are done in a single reaction vessel, and optionally the pre-treatment, the thermal hydrolysis and the post-thermal hydrolysis acidulation are done in the same reaction vessel. 
     
     
         7 . The method of  claim 1 , wherein:
 (a) the soapstock is obtained from the alkaline neutralization of a crude natural oil;   (b) the gums product comprises phospholipids, and optionally the gums product is generated during the degumming of a natural oil; or   (c) the mixed lipid feedstock comprises, or further comprises, one or more compounds produced as a byproduct from the water washing of crude biodiesel, wherein optionally the compounds comprise soapstock, monoglycerides, diglycerides, triglycerides and/or fatty acid alkyl esters or any combination thereof.   
     
     
         8 . The method of  claim 1 , wherein the method is a batch or a continuous process. 
     
     
         9 . The method of  claim 1 , wherein the heating and pressurizing the mixed lipid feedstock takes place in conditions comprising: temperature in a range of between about 100° C. to 500° C., or 200° C. to 400° C., or 240° C. to 300° C., or at about 260° C.; and/or a pressure of between about 650 and 750 psig, between about 750 and 850 psig, between about 850 and 1000 psig, between about 1000 and 1500 psig, or between about 1500 psig and 1800 psig; and/or for between about 20 and 30 minutes, or between about 160 and 180 minutes, or between about 300 minutes and 500 minutes. 
     
     
         10 . The method of  claim 2 , wherein the amount of gas is sufficient to increase the pressure of the reaction mixture, optionally in a reaction vessel, in which the acidulation reaction is being carried out to between about 10 and 1000 psig, about 20 to about 600 psig, about 30 to about 500 psig, about 40 to about 400 psig, about 50 to about 300 psig, about 60 to about 200 psig, about 60 to about 150 psig, about 70 to about 140 psig, about 80 to about 120 psig, about 90 to about 110 psig, or about 100 psig. 
     
     
         11 . The method of  claim 2 , wherein the acidulation reaction is carried out at a temperature in the range of between about 5° C. to about 400° C., e.g. about 10° C. to about 90° C., about 15° C. to about 70° C., about 20° C. to about 60° C., or about 25° C. to about 40° C. 
     
     
         12 . The method of  claim 2 , wherein:
 (a) the acid or acid solution comprises an organic and/or an inorganic acid or a mineral acid, a hydrochloric acid, a sulfuric acid, a formic acid or sodium bisulfate, and optionally when a stack gas comprising N 2 O, NO x , optionally NO 2 , SON x , optionally SO 2 , or H 2 S is used the N 2 O, NO x , SO x , or H 2 S reacts with water in the acidulation reaction mixture to form equivalent aqueous acid species;   (b) after a reaction vessel has reached a desired temperature and pressure to carry out the acidulation step, the resulting reaction mixture is agitated, or otherwise mixed in order to maximize the contacting of the soaps with the acid, optionally carbonic acid, and optionally the mixture can be agitated using a spinning blade mixer, and optionally the mixture is agitated for between about 10 minutes to about 200 minutes, e.g. between about 25 minutes to about 150 minutes, or between about 20 minutes to about 60 minutes, or about 30 minutes;   (c) after the acidulation reaction, and optionally following an agitation step, the contents of the acidulation reaction, optionally in a reaction vessel, are allowed to settle or partition allowing for the formation or separation of a lipid layer, a lipid phase or a lipid component, and an aqueous layer, an aqueous phase or an aqueous component, wherein the lipid layer or lipid phase floats on the top of the aqueous layer,   and optionally the lipid layer or lipid phase comprises free fatty acids and any non-acidulated soaps, and the aqueous layer comprises water, glycerol, phosphate salts, sodium bicarbonate, sodium carbonate or other equivalent salts, unsaponifiable material, optionally waxes and sterols, and dissolved carbonic acid;   (d) the method of (c), wherein before or after the reaction products of the acidulation reaction, optionally in a reaction vessel, are allowed to settle or partition, the reaction products of the acidulation step are transferred to a separation vessel, optionally a decanter, a settler or an equivalent, or a centrifuge where the lipid layer or lipid phase or component separates or partitions out from an aqueous phase or component; or   the acidulation product mixture is not transferred to a separate vessel in order to separate lipids in the lipid layer or lipid phase from reaction products in an aqueous phase or component, and after the lipid layer or lipid phase or component separates or partitions out from the aqueous phase or component the aqueous layer is drained from the bottom of the reaction vessel and the lipid layer or the lipid phase or component is recovered as the reaction product;   (e) further comprising multiple acidulation reactions, optionally between about 1 and 20 additional acidulation reactions, or about 1, 2, 3, 4, 5, 6, 7 or 8 or more additional acidulation reactions; or   (f) after the acidulation reaction the reaction vessel is depressurized, allowing for dissolved carbonic acid or other gaseous acid to separate out of the solution as gaseous CO 2 , or equivalents, and optionally captured CO 2  is recycled for use in the further acidulation reactions.   
     
     
         13 . The method of  claim 1 , wherein the solvent added to the thermal hydrolysis reaction is a polar, optionally a methanol, or a non-polar, optionally a hexane, solvent. 
     
     
         14 . The method of  claim 2 , wherein the thermal hydrolysis reaction and the acidulation reaction take place sequentially; or, the thermal hydrolysis reaction and the acidulation reaction can take place simultaneously as a “one pot” reaction in one reaction vessel. 
     
     
         15 . The method of  claim 12 , wherein the lipid layer or lipid phase or component, optionally comprising unreacted soaps, is transferred to an electrolysis unit, optionally a hydrogen evolving cathode (HEC) electrolysis unit, wherein the lipid layer or lipid phase or component is reacted with an anolyte such that the unreacted soaps generate free fatty acids, and optionally the electrolysis step converts substantially all, or about 90%, 95%, 98% or more of the unreacted soaps to free fatty acids,
 wherein optionally the anode comprises a mixed metal oxide (MMO) layer coated onto a stable metal substrate, optionally a titanium,   and optionally the anolyte comprises a sodium or potassium sulfate, a sodium or potassium nitrate, or a sodium or potassium chloride.   
     
     
         16 . The method of  claim 12 , wherein the lipid layer or lipid phase or component is transferred to an electrolysis unit, optionally a hydrogen evolving cathode (HEC) electrolysis unit, comprising a vessel or suitable container comprising an anode, optionally an anode vessel, and a vessel or other suitable container comprising a cathode, optionally an cathode vessel, separated by a selective filtration membrane, optionally a polytetrafluoroethylene (PTFE) membrane,
 wherein optionally the anode comprises a mixed metal oxide (MMO) layer coated onto a stable metal substrate, optionally a titanium,   and optionally the cathode comprises a titanium or a Monel alloy, or any substrate that is stable in a reducing environment.   
     
     
         17 . The method of  claim 12 , wherein the aqueous phase or component, or multiple aqueous phases if collected from multiple acidulation reactions, is treated to remove water, wherein optionally the treatment of the aqueous phase or component to remove water is by a drying method, optionally evaporation via falling film, forced recirculation flashing or equivalent, thereby generating a product comprising sodium bicarbonate, and optionally the product is dried further to generate a sodium bicarbonate product that is substantially free of any water, optionally less than about 20% water or less than about 10% water, and optionally the drying is done using a fluidized bed dryer, a lyophilizer, a spray dryer, or a rotary drum dryer. 
     
     
         18 . The method of  claim 12 , wherein the aqueous phase or component, or multiple aqueous phases if collected from multiple acidulation reactions, is treated using a filtration, optionally a membrane filtration system, a nano- or microfiltration system or a size-exclusion filtration system, and optionally the filtration is operationally in-line operating continuously with the acidulation step such that aqueous phase generated in the acidulation reaction, or each acidulation reaction if more than one acidulation reaction, is treated immediately after or during the point at which the aqueous phase is separated from the lipid phase, and optionally the aqueous phase is collected and treated in a single batch,
 and optionally soaps and/or other saponifiable material rejected by the filtration, optionally soaps and/or other saponifiable material that do not pass through a membrane of a filter system, are returned to the lipid layer or lipid phase or component for subsequent acidulation reactions, thereby increasing the overall fatty acid yield.   
     
     
         19 . The method of  claim 12 , wherein the aqueous phase or component, or multiple aqueous phases if collected from multiple acidulation reactions, is treated with calcium hydroxide, optionally a slaked lime, to form a calcium precipitate, optionally a calcium phosphate (Ca x (PO 4 ) x ) precipitate, and optionally the lime-treated aqueous phase or component, or multiple aqueous phases if collected from multiple acidulation reactions, is subjected to an oxidation step, optionally a Fenton oxidation wherein hydrogen peroxide and Fe 2+  ions are used to catalyze OH radical formation. 
     
     
         20 . The method of  claim 12 , wherein the aqueous phase or component, or multiple aqueous phases if collected from multiple acidulation reactions, is subjected to electrolysis to recover monovalent ions as a base for a value added product, wherein electrical current is passed through a cathode, the water is reduced, thereby generating hydroxide ions;
 and as monovalent ions, optionally sodium or potassium, are pushed across a membrane separating an anode vessel from a cathode vessel into the cathode vessel, they react with the generated hydroxide ions to generate a corresponding hydroxide base, optionally a sodium hydroxide or a potassium hydroxide, and optionally the hydroxide base separated out, recovered and/or isolated.