Hydrogenated Deoxygenation Raw Material Polyol Treatment

Abstract

The present invention relates to an improved process for treating lipid raw materials for biofuel production, such as used vegetable oils and low-value animal fats. In particular, the present invention relates to a method for providing an advantageous raw material for the production of hydrocarbon biofuels via hydrodeoxygenation.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority from U.S. Provisional Patent Application No. 63 / 350,717, filed on June 9, 2022, which is hereby incorporated by reference in its entirety.

[0002] Field of the Invention The present invention relates to an improved process for treating lipid feedstocks, such as used vegetable oils and low - value animal fats, for biofuel production. In particular, the present invention relates to a method for providing a feedstock useful for the production of hydrocarbon biofuels via hydrodeoxygenation.

[0003] Background of the Invention Renewable diesel (RD) is an isoparaffinic compression - ignition fuel produced by the hydroprocessing of fats and oils. The process for RD production involves hydrodeoxygenation (HDO) of lipid fatty acids and / or glycerides to paraffinic hydrocarbons. In the HDO reaction, the glycerol backbone of the glyceride molecule is converted to propane as a fatty acid and then to diesel - range hydrocarbons. These methods are disclosed in several references, including U.S. Patent Nos. 7,846,323, 7,968,757, 8,026,401, 8,558,042, and 10,246,658, the disclosures of which are hereby incorporated by reference.

[0004] The commercial production of RD began in 2007 and has grown to approximately two billion gallons per year since then. To secure the availability of feedstocks, manufacturers have sought to use lower - quality lipid feeds such as used cooking oils, trap grease, and palm sludge oil.

[0005] These low-quality feeds have numerous contaminants that negatively impact the RD process plant. A particularly concerning category of contaminants is organochlorine compounds (referred to herein as organochlorines). Conventional pretreatment methods (e.g., citric acid / phosphoric acid refining and silica or bleaching earth adsorption) are not particularly effective in removing these compounds from lipids.

[0006] Fatty acids / glycerides react with hydrogen at HDO temperature, pressure, and catalyst contact time to be hydrodeoxygenated to hydrocarbons, water, and carbon oxides, and organochlorines undergo hydrodechlorination to hydrocarbons and hydrogen chloride (HCl). In the presence of steam and HCl, hydrochloric acid can result from steam condensation (e.g., in an HDO drain cooler or a feed and drain exchanger). Hydrochloric acid is well-known to cause stress corrosion and cracking in the stainless steel used in pipes, vessels, and other equipment used to process RD and other materials.

[0007] The locations exposed to corrosion caused by hydrogen chloride are not only due to aqueous hydrochloric acid. The gas-phase by-products of HDO also include hydrogen sulfide (maintained to retain sulfide catalyst activity) and ammonia (formed by hydrodenitrogenation of organic nitrogen components), so ammonium chloride (NH4Cl) salt deposits or precipitates pose another corrosion source. Corrosion due to ammonium bisulfide (NH4HS) salt deposits or precipitates is a common problem in most hydrotreating unit systems and is promoted by ammonium chloride co-precipitates. Corrosion in the HDO reactor system can cause damage to the reactor interior, thermocouples, waste heat exchangers, and cold separator condensers. To address the corrosion risk, costly steel alloy upgrades are required for various system equipment and piping, significantly increasing the capital cost of the RD plant.

[0008] The presence of organochlorines in lipids was somewhat unexpected. This is because according to conventional common sense, organochlorines were not considered to occur naturally.

[0009] Nevertheless, specific organochlorines have been observed and characterized in certain vegetable oils. One such class of compounds includes the monochloropropane diols (MCPD) such as 3-monochloropropane-1,2-diol (3-MCPD) and 2-monochloropropane-1,3-diol (2-MCPD), and their corresponding fatty acid esters. The highest levels of MCPD have been observed in palm oil where the bleaching and deodorization conditions are typically more severe (e.g., higher temperatures than those used for other vegetable oils). MCPD is thought to be a product of the reaction between a chlorine donor and lipids. The chlorine donor itself can be formed by the pyrolysis of smaller organochlorine molecules. Thus, the first step in the "chlorine chain" is the formation of these smaller organochlorine molecules.

[0010] One source of chlorine taken up by plants is thought to be inorganic fertilizer components such as potassium chloride and ammonium chloride. During plant growth, these chloride compounds are taken up by the plants and accumulate in the fruits, seeds and other parts of the plants. At the same time, chlorinated municipal water is also used in industrial processes. In Asia, where most of the palm oil is produced, it is common to use iron chloride as a coagulant in water treatment. Thus, organochlorine molecules are thought to be formed also during the ripening process inside the plants. However, as described in the previous paragraph, since the chlorine donor is formed by the higher temperature treatment of the oil, the chlorine donor migrates into the lipid structure, for example, in the form of MCPD fatty acid esters. The same explanation also applies to the organochlorine in used cooking oil where the chlorine donor is formed during high temperature oil cooking.

[0011] In addition to MCPD esters, organochlorine can be incorporated into lipids as chlorinated fatty acids (CFA). CFA can be in the form of free fatty acids, monoglycerides, diglycerides, triglycerides, or fatty acid alkyl esters. Chlorinated wax esters and sphingolipids have also been reported in the literature, but these are less common.

[0012] Organic chlorine contaminants can also be in the form of synthetic impurities. These can include pesticides (i.e., insecticides, herbicides, fumigants, and fungicides), bactericides, polymers, polymer additives (plasticizers, flame retardants, stabilizers), and industrial detergents or degreasers. Analysis of brown grease from industrial sources has shown the presence of chloroethane, chloroform, chloromethane, 1,2-dichloroethylene, tetrachloroethylene, and trichloroethylene at the ppm level (Ward, P.M.L., Journal of Food Protection, 2012, 75(4);731 - 737).

[0013] Furthermore, chlorine may be incorporated into lipids as either MCPD or CFA through the reaction of chlorine-containing synthetic impurities with lipids. This is evidenced by the high levels of organic chlorine in used cooking oil (UCO).

[0014] Regardless of the source, organic chlorine is hydrodechlorinated to HCl and consequently to hydrogenated dechlorination in the aqueous and solid phase by-products, which causes problems related to corrosion and other processes during RD production.

[0015] To support the growth of the RD industry, a variety of renewable feedstocks and hydrocarbon fuel co-products are required. These include not only low-value waste lipids but also the use of sugars. Conversion technologies for cellulose and hemicellulose to C5 / C6 sugars are at various stages of development and thus provide a route to abundant biofuel feedstocks. However, these feeds are not yet used in the RD manufacturing process.

[0016] Some references disclose the esterification of free fatty acids (FFA) with glycerol to produce glycerides. U.S. Patent Nos. 7,087,771 and 8,088,183 describe such glycerolysis steps to reduce the FFA content of feeds for base-catalyzed transesterification. However, these and other references regarding esterification do not teach or suggest the technical feasibility of removing organic chlorine or contaminants in general.

[0017] Chinese Patent Publication No. CN1053685580A describes a method for removing organic chlorine from waste or used cooking oil. The method includes heating the waste oil in an electro - desalting device in the presence of water, followed by adding a dechlorinating agent. The dechlorinating agent is described as an organic chlorine converter (a nucleophile such as sodium methylate, sodium hydroxide), an organic chlorine transfer agent (an ammonium salt such as quaternary ammonium hydroxide for transferring chlorine species to the aqueous phase), and a polar solvent. However, as a result of the addition of sodium methylate and similar strong bases, soap formation (and a decrease in yield) is expected during the treatment of low - value waste lipids characterized by a relatively high FFA content.

[0018] Therefore, there is a need for a treatment process to remove organic chlorine compounds from the HDO reactor feed. Furthermore, there still exists an unmet need for the incorporation of sugar - based feeds for the production of renewable hydrocarbon co - products in HDO.

[0019] Brief Summary of the Invention The aspects of the invention described below are not intended to be exhaustive nor to limit the invention to the precise forms disclosed in the following detailed description. Rather, the aspects are selected and described so that those skilled in the art can recognize and understand the principles and practice of the invention.

[0020] One aspect of the invention relates to a method for the treatment of low - value waste lipids - specifically, fats, oils, and greases (FOG) - which is a method for converting them to hydrocarbons via hydrodeoxygenation. The method includes esterification in the presence of a polyol. Surprisingly, as a result of the esterification, it has been observed that organic chlorine contaminants in the FOG are removed without the addition of catalysts (such as sodium methylate or other strong bases) as disclosed in the prior art.

[0021] The method involves combining a FOG feedstock with a polyol in an esterification reactor, where the FOG feedstock is subjected to high temperature and low pressure conditions. In some embodiments, water is introduced and contacts the feedstock at the esterification temperature, either before or during esterification. The esterification reactor effluent is optionally washed with water and subjected to liquid-liquid phase separation, where the esterified FOG light phase is separated from the heavy phase containing removed organic chlorine. The esterified FOG light phase has an organic chlorine concentration lower than that of the FOG feedstock. In some embodiments, the esterified FOG light phase undergoes HDO, and the carbon chains of the fatty acid and polyol components of the ester are converted to hydrocarbons of similar chain length.

[0022] Other features and advantages of the invention will be apparent to those skilled in the art from the following detailed description. However, it should be understood that the detailed descriptions of various embodiments and specific examples, while indicating preferred and other embodiments of the invention, are presented by way of illustration and not limitation. Many changes and modifications may be made within the scope of the invention without departing from its spirit, and the invention encompasses all such modifications.

[0023] These and other objects and advantages of the invention will be more fully understood and appreciated by reference to the following more detailed description of the presently preferred exemplary embodiments of the invention, taken in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

[0025] Detailed Description of the Invention The devices and methods disclosed in this document are described in detail by way of example and with reference to the drawings. Unless otherwise indicated, like numbers in the figures refer to the same, similar, or corresponding elements throughout the drawings. Modifications to the disclosed and described examples, arrangements, configurations, components, elements, devices, methods, materials, etc. may be made for a particular application and it will be recognized that such modifications may be desired for a particular application. In this disclosure, any particulars of specific shapes, materials, techniques, arrangements, etc. are related to the specific examples presented or are merely generalizations of such shapes, materials, techniques, arrangements, etc. The specification of specific details or examples is not intended to and should not be construed as essential or limiting unless so specifically indicated. Alternative examples of devices and methods are disclosed and described in detail below with reference to the drawings.

[0026] This technology treats the raw material of FOG having an organic chlorine concentration greater than about 10 wppm and a free fatty acid (FFA) content greater than about 5 wt% by an esterification reaction with a polyol.

[0027] In some aspects, the FFA content of the raw material of FOG is greater than about 10 wt%. In an aspect, the FFA content of the raw material of FOG is greater than 12 wt%. Surprisingly, it has been found that when the FFA content of the raw material of FOG is greater than 12 wt%, the removal of organic chlorine impurities is improved.

[0028] The organic chlorine concentration defined in this specification is the chlorine concentration in the FOG sample after the FOG sample has been thoroughly washed with water. In some embodiments, the organic chlorine concentration of the FOG feedstock is greater than 15 wppm, greater than 20 wppm, greater than 25 wppm, greater than 30 wppm, greater than 35 wppm, greater than 40 wppm, greater than 45 wppm, greater than 50 wppm, greater than 60 wppm, greater than 70 wppm, greater than 80 wppm, greater than 90 wppm, greater than 100 wppm, or within a range between any two of these values. For example, the organic chlorine content of the FOG feedstock is 10 - 100 wppm. In an embodiment, the FFA content of the FOG feedstock is 5 wt% - 75 wt%. In an embodiment, the FFA content of the FOG feedstock is 10 wt% - 75 wt%, 15 wt% - 75 wt%, or 20 wt% - 75 wt%.

[0029] In addition to organic chlorine contaminants, the FOG feedstock also includes a range of other contaminants such as metals, phosphorus, and silicon. Metal contaminants mainly include sodium, potassium, magnesium, calcium, iron, and copper. Phosphorus is typically present in natural fats and oils as phospholipid molecules that include non-hydrated phosphorus lipids ionically bonded to divalent metals such as calcium. Silicon is typically present as an organosilicon contaminant such as a polysiloxane antifoam additive.

[0030] Depending on the amount of phosphorus present, the FOG feedstock may be subjected to a pretreatment step prior to the treatment method of the present technology. In some embodiments, a method such as the method disclosed in U.S. Patent No. 9,404,064 is used to reduce the phosphorus content of the FOG feedstock to less than 20 wppm. In such a pretreatment method, the FOG feedstock is contacted with aqueous phosphoric acid or citric acid, whereby the non-hydrated phosphorus lipid becomes hydrated and migrates to the water / oil interface for removal via centrifugation in a disk-stack centrifuge. In such a pretreatment method, the FOG feedstock may also be contacted with an absorbent filtration medium (e.g., diatomaceous earth or cellulose), an adsorbent filtration medium (e.g., amorphous silica or bleaching earth), or a combination of the two to remove solid contaminants and further remove metals.

[0031] Regardless of whether it is subjected to a pretreatment process, the raw material of FOG is directed towards an esterification reactor system for conversion by the present technology. A polyol is introduced into the esterification reactor together with the raw material of FOG. The polyol reactant is used to convert free fatty acids into fatty acid esters including polyester. Examples of fatty acid polyesters include mono, di and triester products of the reaction between polyol and free fatty acids. The esterification reaction also includes transesterification in which the bound fatty acids of FOG form new esters with the polyol reactant. Without being bound by any particular theory, it is believed that fatty acids, which are part of the raw material of FOG in the form of fatty acid esters of MCPD, migrate to form new esters with the polyol, thus releasing MCPD for removal via water washing phase separation. By contacting FOG with water at the esterification temperature, the desired conversion is accelerated by promoting the hydrolysis of MCPD esters. Esterification occurs in the absence of a catalyst.

[0032] The polyol is typically a purified product having the general molecular formula (CHOH) n H2 (where n = 3, 4, 5, or 6). A preferred polyol is glycerol (n = 3). Other polyols for esterification according to the present technology include erythritol (n = 4), xylitol (n = 5), and sorbitol (n = 6). The amount of polyol introduced into the esterification reactor depends on the FFA and organic chlorine content of the raw material of FOG, as well as the type of polyol reactant. In the case of a polyol having n hydroxyl groups, the stoichiometric ratio of FFA to polyol may be defined as n moles of polyol per mole of FFA (assuming the molecular weight of oleic acid). For example, the stoichiometric ratio of FFA to polyol is 3:1 for glycerol and 6:1 for sorbitol. In an embodiment, the amount of polyol introduced into the esterification reactor is about 20% to about 400% of the stoichiometric FFA to polyol ratio.

[0033] ​The esterification reaction is carried out at a temperature of about 150 °C to about 280 °C, typically about 180 °C to about 250 °C. The reaction is preferably carried out at sub-ambient pressure under stirring conditions. The preferred operating pressure for esterification according to the present technology is less than 14 psia, less than 13 psia, less than 11 psia, less than 10 psia, less than 9 psia, less than 8 psia, less than 7 psia, less than 6 psia, less than 5 psia, less than 4 psia, less than 3 psia, less than 2 psia, less than 1 psia, less than 0.9 psia, less than 0.8 psia, less than 0.7 psia, less than 0.6 psia, less than 0.5 psia, less than 0.4 psia, less than 0.3 psia, less than 0.2 psia, and less than 0.1 psia, or in the range between any two of these values. In a preferred embodiment, the esterification is carried out at a pressure of 0.1 psia to 7 psia. These sub-ambient pressure conditions are maintained throughout the esterification reactor vacuum system. This system may comprise a vacuum pump or an educter system.

[0034] Under the aforementioned conditions of temperature and pressure, the water by-product of the esterification reaction evaporates. Accordingly, the reactor system is equipped with facilities for removing the water by-product through the vacuum system during the course of the reaction. In addition to water, some of the organic chlorine species in the FOG feedstock can also be vaporized and removed by the vacuum system.

[0035] The esterification reaction may be carried out in a batch or continuous reactor system. A preferred batch esterification reactor is equipped with facilities for heating, such as a mechanical stirrer and a jacket for circulation of a heat transfer fluid or condensate. The batch reaction time required for the completion of the esterification is 60 to 600 minutes, preferably 90 to 500 minutes.

[0036] A continuous reactor system for esterification comprises a plurality of stirred tank reactors in series. In some embodiments, the continuous reactor system comprises 2 to 8 reactors in series. Each reactor of the system is equipped with facilities for heating and stirring as already described in the manner of a batch reactor. Further, each reactor of the system is equipped with facilities for introducing a polyol and removing water vapor. In the embodiment of the continuous reactor, 6 reactors are arranged to increase the operating temperature. Regardless of the number of reactors, the residence time through the continuous reactor system is 90 minutes to 500 minutes, preferably 180 to 360 minutes.

[0037] The esterification reactor effluent is then subjected to a water washing and separation process. The amount of water used ranges from about 3% to about 30% of the esterification reactor effluent. The water may be brought into contact with the esterification reactor effluent in a stirred tank, a shear mixer, a static mixer, or similar devices used to provide good contact between immiscible liquid phases.

[0038] The wash water is then removed from the washed esterification reactor effluent. Any liquid-liquid separator such as a settler, a decanter, a drum, or a centrifuge can be used for this purpose.

[0039] In some embodiments, the water washing and the liquid-liquid separator can be part of a subsequent pretreatment process. Thus, the wash water used for contact with the esterification reactor effluent can also optionally include dilute acids (e.g., citric acid or phosphoric acid), and caustic solutions (e.g., sodium hydroxide).

[0040] The heavy phase from the liquid-liquid separator includes the water used to wash the esterification reactor effluent, unreacted polyol, and removed organochlorine compounds / by-products.

[0041] The washed reactor effluent exits the liquid-liquid separator as the light phase. The light phase of this esterification reactor has an organic chlorine concentration that is less than the feedstock of the FOG. In embodiments, the organic chlorine concentration is less than 10 wppm, less than 9 wppm, less than 8 wppm, less than 7 wppm, less than 6 wppm, less than 5 wppm, less than 4 wppm, less than 3 wppm, less than 2 wppm, or less than 1 wppm. In some embodiments, the organic chlorine concentration of the esterification reactor effluent after the washing step is in the range given by any two of these values, for example, 1-10 wppm, or 1-5 wppm.

[0042] Depending on the amount of polyol introduced into the esterification system (e.g., in the case of a stoichiometric excess), the polyol liquid can be separated from the esterification reactor effluent without a water washing step. In some embodiments, the unwashed light phase from the liquid-liquid separation of the polyol-derived esterification product has the reduced organic chlorine concentration identified in the previous paragraph.

[0043] The light phase with reduced organic chlorine content is suitable for hydrodeoxygenation (HDO) including the production of renewable diesel. Since the esters produced in the esterification reactor include the reaction products of polyol and fatty acid, the HDO products include hydrocarbons corresponding to the carbon numbers of both fatty acid and polyol. Therefore, the HDO feedstock including esters formed by C3 polyol (i.e., glycerol) and C18 fatty acids (e.g., stearic acid and oleic acid) is hydrodeoxygenated to a product containing propane and octadecane. Similarly, the HDO feedstock including esters formed by C6 polyol (i.e., sorbitol) and C16 fatty acids (e.g., palmitic acid) is converted to a product containing hexane and hexadecane. Therefore, the esterification of the present technology not only removes harmful organic chlorine from the FOG feedstock, but also provides the ability to produce a wider range of bio-based hydrocarbon products than previously disclosed.

[0044] One aspect of the present technology is provided in the process flow block diagram of FIG. 1. Referring to FIG. 1, the FOG feedstock 101 contacts the water feed 102 in the oil / water contact device 10. The FOG feedstock 101 has an organic chlorine impurity concentration of 10 wppm to 50 wppm and an FFA content greater than 5 wt%. In a preferred embodiment, the FFA content of the FOG feedstock 101 is greater than 12 wt%. The water is preferably demineralized water introduced at a rate of 3% to 10% of the FOG 101. The contact device 10 may be a static mixer or a stirred vessel. The contact device 10 is preferably operated at a temperature of about 150°C to about 280°C, typically about 180°C to about 250°C. The pressure of the contact device 10 may range from atmospheric pressure to 1000 psig, preferably in the range of 0 to 100 psig. The residence time in the contact device 10 ranges from 2 to 60 minutes. Under these conditions, at least a portion of the organic chlorine is converted to water-soluble species, for example, by hydrolysis of MCPD esters. The water-contacted product 103 having an FFA content higher than that of the FOG feed 101 leaves the contact device 10 and is mixed with the polyol feed 104 in the polyol mixer 20.

[0045] The polyol feed 104 includes polyols having the formula (CHOH) n H2 (where n = 3, 4, 5, or 6). In an embodiment, the polyol feed 104 includes xylitol and sorbitol, which are sugar products. The amount of polyol introduced into the esterification reactor is at a stoichiometric FFA to polyol ratio of about 30 percent to about 200 percent.

[0046] The temperature, pressure, and residence time for the polyol mixer 20 are the same as those specified for the water contact device 10. The mixed stream 105 containing polyol and FOG is processed through the esterification unit 30.

[0047] The esterification unit 30 has already been described in the present disclosure. In this embodiment, the esterification unit 30 is operated at a temperature of about 150°C to about 280°C (generally the same as the water contact device 10 and the polyol mixer 30), typically about 180°C to about 250°C. The esterification unit 30 has two or more continuous stirred tank reactors (CSTRs) in series under a pressure of 0.1 psia to 7 psia. A steam stream 106 is withdrawn from the esterification unit 30.

[0048] The removal of water vapor promotes the desired esterification reaction between the polyol and FFA, while the additional residence time promotes the transesterification reaction, whereby MCPD, unreacted glycerol (e.g., from FOG glycerides), and fatty acids are redistributed in the added polyol, thus releasing MCPD from the water-insoluble ester to form a water-soluble free MCPD form. An overview of the possible transesterification reactions is shown in FIG. 2. Referring to FIG. 2, the palmitic acid ester (Structure I) and glycerol (Structure II) of 3-MCPD undergo a transesterification reaction according to Equation 1 to form water-soluble 3-MCPD (Structure III) and monopalmitin (Structure IV). Similarly, the 3-MCPD diester of oleic acid and palmitic acid (Structure V) undergoes a transesterification reaction with xylitol (Structure VI) according to Equation 2 to form the same water-soluble 3-MCPD and the fatty acid diester of xylitol (Structure VII).

[0049] Returning to FIG. 1, the esterification product 107 is washed with wash water 108 in the mixer 40. The mixer 40 may be another stirred tank reactor or a static mixer, where water is added to facilitate the removal of the water-soluble products of the esterification reaction, such as free MCPD isomers.

[0050] The washed product 109 is subsequently phase-separated in a liquid-liquid separator 50. The liquid-liquid separator 50 may be a settling tank, a three-phase separator, or a disk-stack centrifuge. Regardless of the type of device, the liquid-liquid separator 50 provides treated FOG as the light phase 111 and an aqueous heavy phase 110.

[0051] The aqueous heavy phase 110 includes wash water and water-soluble by-products of the esterification reaction that include chlorinated species formed during the conversion of organic chlorine contaminants. The aqueous heavy phase 110 also includes unreacted polyol.

[0052] The light phase 111 is treated FOG and ester species with a reduced organic chlorine concentration. The light phase 111 has an organic chlorine concentration of less than 5 wppm and an FFA content of less than 5 wt%.

[0053] In some embodiments, the light phase 111 can be slurried or contacted with one or more absorbent filtration media (e.g., diatomaceous earth, cellulose) or adsorbent filtration media (e.g., amorphous silica, bleaching earth, ion exchange resin) and subjected to a filtration step to remove the used filtration media, thereby further reducing the metal and phosphorus content in the light phase 111. In embodiments, the contacting and filtration steps are carried out at a temperature of 70 °C to 130 °C and a pressure of 100 mbar to 2 bar for about 5 minutes to 1 hour.

[0054] The light phase 111 is subsequently hydrodeoxygenated in an HDO reactor system 60 where it contacts a hydrogen-rich process gas 112. The HDO reactor system includes a fixed-bed HDO reactor containing a sulfided NiMo catalyst. The reactor is operated in a temperature range of 290 °C to 370 °C under a pressure of 500 to 2000 psig. The corresponding liquid hourly space velocity for HDO is 0.3 to 5 h -1 -1, while the hydrogen-to-feed (light phase 11) ratio is maintained at a value in the range of 800 to 1600 NL / L.

[0055] The HDO product is separated from unreacted hydrogen gas and gaseous by-products (including CO, CO2, H2S, NH3, propane, and water vapor in a thermal separator (not shown) and condensed water in a cold separator (not shown)). Both the thermal separator and the cold separator are operated at the reactor outlet pressure (minus line losses). The thermal separator is operated at a temperature of 200 °C to 300 °C, while the cold separator is operated at 20 °C to 50 °C. Heavier hydrocarbons, as well as the reaction products of fatty acid hydrogenation and deoxygenation, mainly C15 - C18 n-paraffins, are recovered in the thermal separator. In some embodiments, a portion of this stream is recycled to the HDO reactor as a reaction solvent or diluent. Propane and C5 / C6 hydrocarbons correspond to the polyol portion of the ester. Specifically, propane corresponds to glycerol, and C5 / C6 corresponds to xylitol / sorbitol. These are almost completely condensed as hydrocarbon solutions in the cold separator. In the case of propane, the fraction remaining in the cold separation gas can be recovered in the hydrocarbon liquid through a membrane and / or by absorption. In some embodiments, the C5 / C6 hydrocarbon cut is used as an absorption solvent (in a gas absorption column, not shown, where the propane-containing H2 bleed gas contacts the C5 / C6 hydrocarbons countercurrently and the propane moves to the C5 / C6 hydrocarbon gas absorption column). This enables the C5 / C6 hydrocarbon stream to carry propane to the product fractionation system 70.

[0056] In some embodiments, the hydrocarbon liquids from the thermal separator and the cold separator from the HDO reactor system 60 are combined to provide a mixed hydrocarbon 113. The mixed hydrocarbon 113 is processed in the fractionation system 70, where it is separated into three hydrocarbon product fractions: a propane fraction 114, a C5 / C6 fraction 115, and a heavy hydrocarbon fraction 116.

[0057] In one embodiment, the propane fraction 116 is used as a direct replacement for or supplement to fossil fuel propane for heating, cooking, and transportation. The C5 / C6 fraction 115 is isomerized to automotive gasoline using commercial petroleum refining techniques known to those skilled in the art. C5 / C6 isomerization techniques include the UOP PENEX and Axens ATIS-2L processes. Since the reported octane number is as high as 92, the isomerized C5 / C6 fraction can be used as a direct replacement for or supplement to petroleum gasoline.

[0058] In some embodiments where the only polyol added for esterification is sorbitol, a pure n-hexane fraction is recovered instead of the mixed C5 / C6. In such embodiments, n-hexane can be used in a number of solvent applications such as oilseed extraction. Examples of such oilseeds include, but are not limited to, rapeseed, canola, sunflower, and soybean.

[0059] The heavy hydrocarbon fraction 116 contains the aforementioned C15 - C18 n-paraffins. This fraction fully falls within the diesel boiling range and can be used as a compression ignition fuel blendstock. The heavy hydrocarbon fraction 116 can also be hydrocracked / isomerized according to methods disclosed in the prior art (e.g., U.S. Patent Nos. 7,846,323, 7,968,757, and 8,558,042) to provide drop-in RD or sustainable aviation fuel.

[0060] Example (Example 1) A continuous esterification system was operated according to the conditions described herein. An esterification reaction process using six CSTRs in series was operated at an increasing temperature in the range of about 175 - 250 °C and a pressure of about 345 - 375 mbar. A blend of raw materials including used cooking oil and Distillers Corn Oil, and a raw material of FOG having an FFA content of about 20 wt% was preheated and fed to the first reactor. Technical glycerol was added at about 15 wt% (based on the raw material of FOG) together with the raw material of FOG. The total residence time of the six reactors was approximately 4 hours.

[0061] Samples were taken from the sampling positions before and after the esterification system to measure the organic chlorine content of the raw material of FOG and the esterification reactor effluent, respectively. A total of 12 samples were taken from each sampling position at approximately 8 - hour intervals over about 2 days. Subsequently, each sample was analyzed for its organic chlorine content by monochromatic wavelength - dispersive X - ray fluorescence analysis with XOS Clora according to ASTM D4929. The results of this analysis are summarized in Figure 3. On average, the raw material of FOG had an organic chlorine content of about 10 ppm, while the esterification reactor effluent had an average organic chlorine content of about 3 ppm, and the reduction was approximately 70%.

[0062] (Example 2) The raw material of FOG was subjected to a continuous esterification process in the same or similar manner as disclosed in Example 1. The raw material of FOG was a blend of raw materials including Distillers Corn Oil, used cooking oil, and brown grease, and had an average FFA content of about 21 wt%. The organic chlorine content of the raw material of FOG was about 17 ppm, and it decreased to 10 ppm after the esterification reaction, and the reduction was approximately 40%.

[0063] (Example 3) The batch esterification reaction was carried out using a 1 L stirred round-bottom flask heated to approximately 235°C. The raw material of FOG was fed into the reaction vessel and heated to the reaction temperature at a pressure of approximately 20 mbar. When water and air were completely removed from the raw material of FOG, technical glycerin was added to the reaction vessel at an input rate of approximately 12% by weight based on the raw material. The reactor contents were mixed at approximately 300 rpm using a magnetic stir bar. The reaction proceeded isothermally for approximately 5 hours, during which all vapors and gases were directed through the upper port of the reaction vessel to a condenser operated at approximately 60°C. All water vapor and any other condensable materials were collected from the condenser into the round-bottom flask, and the non-condensable gases were exhausted to the fume hood.

[0064] The raw material of FOG used in this experiment was mainly used cooking oil. The FFA content before the esterification reaction was approximately 12% by weight, and the organochlorine content was approximately 22 ppm. After the reaction, the esterification reaction product had an FFA of less than 0.1% by weight, an organochloride content of approximately 16 ppm, and an organochloride reduction of approximately 26%.

[0065] Therefore, according to the present invention, it can be seen that a highly advantageous method for the removal of organochlorine derived from fats, oils, and greases has been provided. Although the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, the present invention is not limited to the embodiments of this disclosure, and many modifications and equivalent arrangements may be made within the scope of the present invention, the scope of which will, as will be understood by those skilled in the art, coincide with the broadest interpretation of the appended claims and will include all equivalent structures and products.

[0066] The inventors hereby state their intention to determine and evaluate, based on the doctrine of equivalents, the reasonably fair scope of the present invention in relation to any apparatus, system, method, or article that is outside the exact scope of the present invention as set forth in the following claims but does not substantially depart therefrom.

Claims

1. A method for treating a feedstock of FOG for hydrodeoxygenation, comprising the following steps: (a) mixing the feedstock of FOG and a polyol in an esterification reactor to supply an esterification product; (b) washing the esterification product with water to supply a water-washed product; and (c) separating a treated FOG light phase from the water-washed product, provided that the feedstock of FOG has an organic chlorine content of 10 wppm to 50 wppm, and the treated FOG light phase has an organic chlorine content of less than 5 wppm.

2. The method according to claim 1, wherein the feedstock of FOG has an FFA content greater than 5 wt%.

3. The method according to claim 1, wherein the feedstock of FOG has an FFA content greater than 10 wt%.

4. The method according to claim 1, wherein the feedstock of FOG has an FFA content greater than 12 wt%.

5. The method according to claim 1, wherein the esterification reactor is operated at a temperature of 150°C to 280°C.

6. The method according to claim 1, wherein the esterification reactor is operated at a pressure of 0.1 psia to 7 psia.

7. The method according to claim 1, wherein the feedstock of FOG is mixed with a polyol after being contacted with water.

8. The method according to claim 1, wherein the polyol is glycerol.

9. The method according to claim 1, wherein the polyol is xylitol and / or sorbitol.

10. The method according to claim 1, further comprising subjecting the treated FOG light phase to a hydrodeoxygenation process by contacting the treated FOG light phase with a hydrogen-rich treatment gas to produce a mixed hydrocarbon.

11. The method according to claim 10, wherein the mixed hydrocarbon comprises C5 / C6 hydrocarbons for motor gasoline.

12. The method according to claim 10, wherein the mixed hydrocarbon comprises n-hexane.

13. A treated FOG composition for hydrodeoxygenation, comprising: (a) fatty acid esters of sorbitol or xylitol or erythritol; (b) fatty acid esters of glycerol; (c) organic chlorine at a concentration of 1 wppm to 5 wppm; and (d) free fatty acids at a concentration of less than 5 wt%.

14. The composition according to claim 13, produced by esterification of a feedstock of FOG with a polyol comprising xylitol or sorbitol.

15. The composition according to claim 14, wherein the esterification is carried out at a temperature of 150°C to 280°C.

16. The composition according to claim 14, wherein the esterification is carried out at a pressure of 0.1 to 7 psia.

17. The composition according to claim 13, wherein the FOG feedstock has an organic chlorine content of 10 wppm to 50 wppm.

18. A method for producing a mixed hydrocarbon from a FOG feedstock, comprising the following steps: (a) mixing the FOG feedstock and a polyol in an esterification reactor to supply an esterification product; (b) washing the esterification product with water to supply a water-washed product; (c) separating a treated FOG light phase from the water-washed product, provided that the FOG feedstock has an organic chlorine content of 10 wppm to 50 wppm and the treated FOG light phase has an organic chlorine content of less than 5 wppm; and (d) subjecting the treated FOG light phase to a hydrodeoxygenation process by contacting it with a hydrogen-rich treatment gas to produce a mixed hydrocarbon.

19. The method according to claim 18, further comprising separating the mixed hydrocarbon into a propane fraction, a C5 / C6 fraction, and a heavy hydrocarbon fraction.

20. The method according to claim 18, wherein hydrocarbons are produced in either the diesel boiling range or the gasoline boiling range by a hydrodeoxygenation process.

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