Polyol treatment of hydrodeoxygenated feedstocks

Abstract

The present invention relates to an improved process for treating lipid feedstocks, such as spent vegetable oils and low value animal fats, to produce biofuels. In particular, the present invention relates to a process for providing an advantageous feedstock for the production of hydrocarbon biofuels by hydrodeoxygenation.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application No. 63 / 350,717, filed on June 9, 2022, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present invention relates to an improved process for processing lipid feedstocks (such as waste vegetable oils and low-value animal fats) to produce biofuels. In particular, the present invention relates to a method for providing an advantageous feedstock for the production of hydrocarbon biofuels by hydrodeoxygenation. Background Art

[0004] Renewable diesel (RD) is an isoparaffinic compression ignition fuel produced by hydrotreating fats and oils. The RD production process includes hydrodeoxygenating (HDO) lipid fatty acids and / or glycerides to paraffin hydrocarbons. In the HDO reaction, the glycerol backbone of the glyceride molecule is converted to propane and the fatty acids are converted to diesel range hydrocarbons. These methods have been disclosed in multiple references, including U.S. Patents 7,846,323, 7,968,757, 8,026,401, 8,558,042 and 10,246,658, the disclosures of which are incorporated herein by reference.

[0005] Commercial production of RD began in 2007 and has grown to about 2 billion gallons per year. To ensure feedstock availability, producers have been exploring the use of lower-quality lipid feedstocks such as used cooking oils, trap grease and palm residue oil.

[0006] These lower quality feeds contain a large amount of pollutants, which adversely affect the RD processing plant. A particularly concerning pollutant class is organochlorine compounds (herein referred to as organochlorine). Traditional pretreatment methods (e.g., citric acid / phosphoric acid degumming and silica or bleaching clay adsorption) are not particularly effective for removing these compounds from lipids. When fatty acids / glycerides react with hydrogen to hydrodeoxygenate hydrocarbons, water and carbon oxides under HDO temperature, pressure and catalyst contact time conditions, organochlorine carries out hydrodechlorination reaction to generate hydrocarbons and hydrogen chloride (HCl). In the presence of water vapor and HCl, any steam condensation (e.g., in HDO effluent cooler or feed-effluent exchanger) will cause hydrochloric acid to form. As is well known, hydrochloric acid is the cause of stress corrosion and cracking in the stainless steel used in the pipelines, containers and other equipment for processing RD and other materials.

[0007] Corrosion pathways caused by hydrogen chloride are not limited to aqueous hydrochloric acid. Since gas phase byproducts of HDO also include hydrogen sulfide (retained to keep the sulfide catalyst active) and ammonia (formed by hydrodenitrogenation of organic nitrogen components), ammonium chloride (NH4Cl) salt deposition or precipitation provides another corrosion source. Corrosion caused by ammonium hydrosulfide (NH4HS) salt deposition or precipitation, a common problem in most hydrotreater systems, is exacerbated by ammonium chloride co-precipitation. Corrosion in HDO reactor systems can cause damage to reactor internals, thermocouples, hot-effluent exchangers, and cold separator condensers. To address the corrosion risk, various system equipment and piping require expensive steel alloy upgrades, which significantly increase the capital cost of RD plants.

[0008] The presence of organochlorines in lipids was somewhat surprising. After all, conventional wisdom holds that organochlorine compounds do not occur naturally in nature.

[0009] Nevertheless, unique organochlorine compounds have been observed and characterized in certain vegetable oils. One class of compounds is the monochloropropanediols (MCPDs), which include 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 MCPDs are observed in palm oil, when bleaching and deodorization conditions are generally more severe (e.g., higher temperatures than used for other vegetable oils). MCPDs are believed to be the product of reactions between chlorine donors and lipids. The chlorine donors themselves can be formed by thermal decomposition of smaller organochlorine molecules. Therefore, the first step in the "chlorine chain" is the formation of these smaller organochlorine molecules.

[0010] It is believed that one of the sources of chlorine absorbed by plants is inorganic fertilizer components, such as potassium chloride and ammonium chloride. During plant growth, these chlorine compounds are absorbed by the plant and accumulated in fruits, seeds and other parts of the plant. At the same time, chlorinated municipal water is used for processing. In Asia, where palm oil is abundant, ferric chloride is commonly used as a flocculant in water treatment. Therefore, it seems that the organochlorine molecules are formed endogenously during the maturation of the plant. However, as described in the previous paragraph, it is the higher temperature processing of the oil that forms the chlorine donor and thus transfers it to the lipid structure, such as MCPD fatty acid esters. A similar explanation can be provided for the organochlorine in used cooking oils, where the high temperature frying operation forms the chlorine donor.

[0011] In addition to MCPD esters, organochlorines can also be incorporated into lipids as chlorinated fatty acids (CFAs). CFAs 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, although these are less common.

[0012] Organochlorine contamination may also be present in the form of synthetic adulterants. These may include pesticides (i.e., insecticides, herbicides, fumigants, and fungicides), disinfectants, polymers, polymer additives (plasticizers, flame retardants, stabilizers), and industrial cleaners or degreasers. Analysis of brown grease from commercial sources has shown the presence of ppm levels of ethyl chloride, chloroform, methyl chloride, 1,2-dichloroethylene, tetrachloroethylene, and trichloroethylene (Ward, PML Journal of Food Protection, 2012, 75 (4); 731-737).

[0013] In addition, chlorine can be incorporated into lipids in the form of MCPD or CFA through the reaction of chlorine-containing synthetic dopants with lipids. This has been demonstrated by the elevated organochlorine content in used cooking oil (UCO).

[0014] Regardless of the source, organochlorine is hydrodechlorinated to HCl and subsequent aqueous and solid byproducts that cause corrosion and other process problems during RD production.

[0015] To support the development of the RD industry, multiple renewable feedstocks and hydrocarbon fuel co-productions are sought, including the use of not only low-value and waste lipids, but also sugars. Technologies for converting cellulose and hemicellulose to C5 / C6 sugars are at various stages of development, providing access to abundant biofuel feedstocks. However, these feedstocks have not yet been used in RD production processes.

[0016] Some references disclose the esterification of free fatty acids (FFA) with glycerol to generate glycerides. U.S. Patents 7,087,771 and 8,088,183 describe such a glycerolysis step for reducing the FFA content in the feedstock for base-catalyzed transesterification reactions. However, these and other esterification references do not teach or suggest the feasibility of using the technology for removing organochlorine or general pollutants.

[0017] Chinese patent publication CN1053685580A describes a method for removing organochlorine from waste or used cooking oil. The method includes heating the waste oil in an electric desalter in the presence of water and then adding a dechlorinating agent. The dechlorinating agent is described as an organochlorine conversion agent (nucleophilic reagent, such as sodium methoxide, sodium hydroxide, etc.), an organochlorine transfer agent (ammonium salt, such as quaternary ammonium hydroxide, for transferring chlorine species to the aqueous phase) and a polar solvent. However, when treating low-value and waste lipids characterized by relatively high FFA content, the addition of sodium methoxide and similar strong bases is expected to lead to the formation of soaps (and lead to yield losses).

[0018] Therefore, there is a need for a treatment process to remove organochlorine compounds from the HDO reactor feed. In addition, there remains an unmet need to add sugar-based feedstocks to the HDO process to produce renewable hydrocarbon co-products. Summary of the invention

[0019] The embodiments of the invention described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description of the invention. Instead, these embodiments are selected and described to enable others skilled in the art to appreciate and understand the principles and practices of the invention.

[0020] One aspect of the present invention relates to a method for treating low-value and waste lipids, particularly fats, oils and greases (FOG), by converting them into hydrocarbons through hydrodeoxygenation. The method comprises esterification in the presence of a polyol. It has been surprisingly observed that the esterification can remove organochlorine contaminants from FOG without the addition of catalysts disclosed in the prior art (e.g., sodium methoxide or other strong bases).

[0021] The method comprises combining the FOG feedstock with a polyol in an esterification reactor, where it is subjected to high temperature and low pressure conditions. In some embodiments, water is introduced before esterification or during the esterification process and is contacted with the feedstock at the esterification temperature. The esterification reactor effluent is optionally washed with water and subjected to liquid-liquid phase separation, wherein the esterified FOG light phase is separated from the heavy phase including the removed organochlorine. The organochlorine concentration of the esterified FOG light phase is lower than that of the FOG feedstock. In some embodiments, the esterified FOG light phase undergoes HDO, wherein the carbon chains of the fatty acids and polyol components of the esters are converted into hydrocarbons with similar chain lengths.

[0022] Through the following detailed description, other features and advantages of the present invention will become apparent to those skilled in the art. However, it should be understood that the detailed description of various embodiments and specific examples, although showing preferred embodiments of the present invention and other embodiments, is only provided in an illustrative and non-limiting manner. Without departing from the spirit of the present invention, many changes and modifications may be made within the scope of the present invention, and the present invention includes all such modifications. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0024] Figure 1 is a flow chart of one embodiment of the present disclosure;

[0025] Figure 2is a reaction diagram showing a chemical reaction relevant to the present disclosure; and

[0026] Figure 3 is a graph providing an overview of the experimental results of Example 1. DETAILED DESCRIPTION

[0027] The apparatus and methods disclosed herein are described in detail herein by way of example and with reference to the accompanying drawings. Unless otherwise specified, the same numbers in the figures represent the same, similar or corresponding elements in the drawings. It should be understood that the disclosed and described examples, arrangements, configurations, components, elements, devices, methods, materials, etc. may be modified and may be modified for specific applications. In the present disclosure, the identification of any specific shape, material, technology, arrangement, etc. is either related to the specific example presented or is merely a general description of such shape, material, technology, arrangement, etc. The identification of specific details or examples is not intended to be, nor should it be interpreted as, mandatory or restrictive unless explicitly stated. Selected examples of the apparatus and methods will be disclosed and described in detail below with reference to the accompanying drawings.

[0028] The present technology treats FOG feedstock having an organochlorine concentration greater than about 10 wppm and a free fatty acid (FFA) content greater than about 5 wt% by esterification reaction with a polyol.

[0029] In some embodiments, the FFA content of the FOG feedstock is greater than about 10 wt%. In embodiments, the FFA content of the FOG feedstock is greater than 12 wt%. Surprisingly, when the FFA content of the FOG feedstock is greater than 12 wt%, the removal of organochlorine contaminants is improved.

[0030] As defined herein, organochlorine concentration is the chlorine concentration present in the FOG sample after the FOG sample is thoroughly cleaned with water.In some embodiments, the FOG raw material organochlorine concentration is greater than 15wppm, greater than 20wppm, greater than 25wppm, greater than 30wppm, greater than 35wppm, greater than 40wppm, greater than 45wppm, greater than 50wppm, greater than 60wppm, greater than 70wppm, greater than 80wppm, greater than 90wppm, greater than 100wppm, or in the range between any two of these values.For example, the organochlorine content of FOG raw material is between 10 to 100wppm.In embodiments, the FFA content of FOG raw material is between 5 weight % and 75 weight %.In embodiments, the FFA content of FOG raw material is between 10 weight % and 75 weight %, between 15 weight % and 75 weight % or between 20 weight % and 75 weight %.

[0031] In addition to organochlorine contaminants, FOG feedstocks also contain a range of other contaminants, such as metals, phosphorus and silicon. Metal contaminants mainly include sodium, potassium, magnesium, calcium, iron and copper. Phosphorus is usually present in natural fats and oils in the form of phospholipid molecules, including non-hydratable phospholipids bound to divalent metal (such as calcium) ions. Silicon is usually present in the form of organosilicon contaminants, such as polysiloxane defoaming additives.

[0032] Depending on the amount of phosphorus present, the FOG feedstock may undergo a pretreatment step prior to the treatment method of the present technology. In some embodiments, the phosphorus content in the FOG feedstock is reduced to less than 20 wppm using a method such as that disclosed in U.S. Pat. No. 9,404,064. In this pretreatment method, the FOG feedstock is contacted with an aqueous solution of phosphoric acid or citric acid so that the non-hydratable phospholipids become hydratable and transferred to the water / oil interface for removal by centrifugation in a disc centrifuge. In such a pretreatment method, the FOG feedstock may also be contacted with an absorptive filter media (such as diatomaceous earth or cellulose), an adsorptive filter media (such as amorphous silica or bleaching clay), or a combination of both to remove solid contaminants and further remove metals.

[0033] Whether or not a pretreatment step is performed, the FOG feedstock is fed into an esterification reactor system and converted according to the present technology. A polyol is introduced into the esterification reactor together with the FOG feedstock. The polyol reactant is used to convert free fatty acids into fatty acid esters (including polyesters). Examples of fatty acid polyesters include monoesters, diesters, and triester products of reactions between polyols and free fatty acids. Esterification reactions also include transesterification reactions, in which the bound fatty acids of FOG form new esters with the polyol reactants. Without being bound by any particular theory, it is believed that fatty acids present in the form of fatty acid esters of MCPD as part of the FOG feedstock migrate and form new esters with the polyols, thereby releasing MCPD and removing it by water wash phase separation. Contacting FOG with water at esterification temperatures can promote the hydrolysis of MCPD esters, thereby accelerating the desired conversion. Esterification occurs in the absence of a catalyst.

[0034] Polyols are usually purified products with the general formula (CHOH) nH2, wherein n=3, 4, 5 or 6. The preferred polyol is glycerol (n=3). Other polyols used 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 organochlorine content in the FOG feedstock and the type of polyol reactant. For a polyol having n hydroxyl groups, the stoichiometric ratio of FFA to polyol can 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), 6:1 (for sorbitol). In an embodiment, the amount of polyol introduced into the esterification reactor is from about 20% to about 400% of the stoichiometric ratio of FFA to polyol.

[0035] 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 under stirring conditions below ambient pressure. The preferred operating pressure of the esterification reaction according to the present technology is less than 14psia, less than 13psia, less than 11psia, less than 10psia, less than 9psia, less than 8psia, less than 7psia, less than 6psia, less than 5psia, less than 4psia, less than 3psia, less than 2psia, less than 1psia, less than 0.9psia, less than 0.8psia, less than 0.7psia, less than 0.6psia, less than 0.5psia, less than 0.4psia, less than 0.3psia, less than 0.2psia and less than 0.1psia, or in the range of any two between these values. In a preferred embodiment, the esterification is carried out at a pressure between 0.1psia and 7psia. These conditions below ambient pressure are maintained by an esterification reactor vacuum system. The system may include a vacuum pump or an ejector system.

[0036] Under the above temperature and pressure conditions, the by-product water of the esterification reaction is evaporated. Therefore, the reactor system is equipped with a device to remove the water by-product through a vacuum system during the reaction. In addition to water, some organic chlorine substances in the FOG raw material may also be evaporated and removed through the vacuum system.

[0037] The esterification reaction can be carried out in a batch or continuous reactor system. Preferred batch esterification reactors include means for heating, such as a mechanical stirrer and a jacket for circulating a heat transfer fluid or steam condensate. The batch reaction time for completing the esterification is 60 to 600 minutes, preferably 90 to 500 minutes.

[0038] The continuous reactor system for esterification includes a plurality of stirred tank reactors in series. In some embodiments, the continuous reactor system includes two to eight reactors in series. Each reactor in the system includes a heating and stirring device as previously described for the batch reactor embodiment. In addition, each reactor in the system includes a device for quantitatively supplying polyols and removing water vapor. In the continuous reactor embodiment, six reactors are arranged in an order of increasing operating temperature. Regardless of the number of reactors, the residence time by the continuous reactor system is between 90 and 500 minutes, preferably between 180 and 360 minutes.

[0039] The esterification reactor effluent is then subjected to a water wash and separation step. The amount of water used is from about 3% to about 30% of the esterification reactor effluent. The water can be contacted with the esterification reactor effluent in a stirred tank, a shear mixer, a static mixer or a similar device for providing good contact between immiscible liquid phases.

[0040] The wash water is then removed from the washed esterification reactor effluent.Any liquid-liquid separator, such as a settler, decanter, drum or centrifuge may be used for this purpose.

[0041] In some embodiments, the water wash and liquid-liquid separator may be part of a subsequent pretreatment process. Thus, the wash water used to contact the esterification reactor effluent may also optionally include a dilute acid (e.g., citric acid or phosphoric acid) and an alkaline solution (e.g., sodium hydroxide).

[0042] The heavy phase from the liquid-liquid separator includes water used to wash the esterification reactor effluent, any unconverted polyols, and removed organochlorine compounds / by-products.

[0043] The washed reactor effluent flows out of the liquid-liquid separator as a light phase. The organochlorine concentration of this esterification reactor light phase is lower than that of the FOG feedstock. In embodiments, the organochlorine 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 organochlorine concentration of the esterification reactor effluent after the washing step is within the range given by any two of these values, for example, between 1 and 10 wppm, or between 1 and 5 wppm.

[0044] Depending on the amount of polyol introduced into the esterification system (e.g., when in stoichiometric excess), the polyol liquid can be separated from the esterification reactor effluent without a water wash step. In some embodiments, the unwashed light phase from the liquid-liquid separation of the polyol esterification product has a reduced organic chlorine concentration as described in the previous paragraph.

[0045] The light phase with reduced organochlorine content is suitable for hydrodeoxygenation (HDO), including for the production of renewable diesel. Since the esters generated in the esterification reactor include the reaction products of polyols and fatty acids, the HDO products include hydrocarbons corresponding to the carbon atom numbers of both fatty acids and polyols. Therefore, HDO feedstocks including esters formed by C3 polyols (i.e., glycerol) and C18 fatty acids (e.g., stearic acid and oleic acid) are hydrodeoxygenated to products containing propane and octadecane. Similarly, HDO feedstocks including esters formed by C6 polyols (i.e., sorbitol) and C16 fatty acids (e.g., palmitic acid) are converted into products containing hexane and hexadecane. Therefore, the esterification of the present technology can not only remove harmful organochlorines from FOG feedstocks, but also produce a wider range of bio-based hydrocarbon products than previously disclosed.

[0046] exist Figure 1 An embodiment of the present technology is provided in the process flow diagram of Figure 1 , FOG feedstock 101 is contacted with water feed 102 in oil / water contactor 10. FOG feedstock 101 has an organochlorine contaminant concentration between 10wppm and 50wppm and an FFA content greater than 5% by weight. In a preferred embodiment, the FFA content of FOG feedstock 101 is greater than 12% by weight. The water is preferably deionized water, and its introduction ratio is between 3% and 10% of FOG 101. Contactor 10 can be a static mixer or a stirred vessel. Contactor 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 range of contactor 10 can be from atmospheric pressure to 1000psig, preferably in the range of 0-100psig. The residence time in contactor 10 is 2 to 60 minutes. Under these conditions, at least some of the organochlorine is converted into water-soluble substances, for example, by hydrolysis of MCPD esters. The water-contacted product 103 , which has a higher FFA content than the FOG feed 101 , leaves the contactor 10 to be mixed with the polyol feed 104 in the polyol mixer 20 .

[0047] The polyol feed 104 includes polyols having the formula (CHOH) n H2, wherein n=3, 4, 5 or 6. In embodiments, the polyol feed 104 includes sugar products, xylitol and sorbitol. The amount of polyol introduced into the esterification reactor is from about 30% to about 200% of the stoichiometric ratio of FFA to polyol.

[0048] The temperature, pressure and residence time of the polyol mixer 20 are the same as those described for the water contactor 10. The mixed stream 105 comprising polyols and FOG is processed through the esterification unit 30.

[0049] The esterification unit 30 has been described previously in this disclosure. In this embodiment, the esterification unit 30 is operated at a temperature of about 150 to about 280° C. (generally the same as the water contactor 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 at a pressure of between 0.1 psia and 7 psia. A water vapor stream 106 is withdrawn from the esterification unit 30.

[0050] The removal of water vapor promotes the desired esterification reaction between the polyol and FFA, while the additional residence time promotes transesterification reactions, which allows the fatty acids to redistribute between MCPD, native glycerol (e.g., from FOG glycerides), and the added polyol, thereby releasing MCPD from the water-insoluble ester form to the water-soluble free MCPD form. A schematic diagram of a potential transesterification reaction is shown in Figure 2 Reference Figure 2 , the palmitate of 3-MCPD (Structure I) and glycerol (Structure II) are transesterified according to Reaction Formula 1 to form water-soluble 3-MCPD (Structure III) and palmitic acid monoglyceride (Structure IV). Similarly, the 3-MCPD diester of oleic acid and palmitic acid (Structure V) can be transesterified with xylitol (Structure VI) according to Reaction Formula 2 to form the same water-soluble 3-MCPD and xylitol fatty acid diester (Structure VII).

[0051] Back to Figure 1 , the esterification product 107 is washed with wash water 108 in mixer 40. Mixer 40 may be another stirred tank reactor or a static mixer, where water is added to facilitate the removal of water-soluble products of the esterification reaction (e.g., free MCPD isomers).

[0052] The washed product 109 is then phase separated in a liquid-liquid separator 50. The liquid-liquid separator 50 can be a settling tank, a three-phase separator, or a disc centrifuge. Regardless of the type of equipment, the liquid-liquid separator 50 provides treated FOG (as a light phase 111) and an aqueous heavy phase 110.

[0053] The heavy aqueous phase 110 includes wash water and water-soluble byproducts of the esterification reaction (including chlorinated species formed during the conversion of organochlorine pollutants). The heavy aqueous phase 110 also includes unreacted polyols.

[0054] The light phase 111 is the treated FOG, in which the organic chlorine concentration and ester substances are reduced. The organic chlorine concentration of the light phase 111 is less than 5wppm, and the FFA content is less than 5% by weight.

[0055] In some embodiments, the light phase 111 may be slurried or contacted with one or more absorptive filter media (e.g., diatomaceous earth, cellulose) or adsorptive filter media (e.g., amorphous silica, bleaching clay, ion exchange resins) and subjected to a filtration step to remove the spent filter media to further reduce the metal and phosphorus content of the light phase 111. In embodiments, the contacting and filtration steps are performed at a temperature between 70° C. and 130° C. and at a pressure between 100 mbar and 2 bar for about 5 minutes to 1 hour.

[0056] The light phase 111 is then hydrodeoxygenated in the HDO reactor system 60, where the light phase 111 is contacted with a hydrogen-rich treat gas 112. The HDO reactor system comprises a fixed bed HDO reactor containing a sulfided NiMo catalyst. The reactor is operated at a temperature range of 290° C. to 370° C. at a pressure of 500-2000 psig. The corresponding liquid hourly space velocity of HDO is in the range of 0.3-5 h -1 , while the ratio of hydrogen to feed (light phase 11) was maintained at a value in the range of 800-1600 NL / L.

[0057] The HDO product is separated from unreacted hydrogen and gas phase byproducts (including CO, CO2, H2S, NH3, propane, and water vapor) in a hot separator (not shown) and separated from condensed water in a cold separator (not shown). Both the hot separator and the cold separator operate at the reactor outlet pressure (minus pipeline losses). The hot separator operates at a temperature between 200°C and 300°C, while the cold separator operates at a temperature between 20°C and 50°C. The heavier hydrocarbons and the reaction products of fatty acid hydrogenation and deoxygenation (mainly C15-C18 normal alkanes) are recovered in the hot separator. In an embodiment, a portion of the 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. Most of these are condensed into light hydrocarbon solutions in the cold separator. For propane, the remaining fraction in the cold separator gas can be recovered by membrane and / or by absorption in hydrocarbon liquids. In an embodiment, the C5 / C6 hydrocarbon fraction is used as an absorption solvent (in a gas absorption tower, not shown, where the propane-containing H2 bleed is countercurrently contacted with the C5 / C6 hydrocarbons to transfer the propane to the C5 / C6 hydrocarbons). This allows the C5 / C6 hydrocarbon stream to carry the propane to the product fractionation system 70.

[0058] In an embodiment, the hot separator and cold separator hydrocarbon liquids (the cold separator liquid includes propane and C5 / C6 hydrocarbons) from the HDO reactor system 60 are combined to provide mixed hydrocarbons 113. The mixed hydrocarbons 113 are processed through the fractionation system 70, where they are separated into three hydrocarbon product fractions: a propane fraction 114, a C5 / C6 fraction 115, and a heavy hydrocarbon fraction 116.

[0059] In embodiments, propane fraction 116 is used as a direct replacement or supplement for fossil fuel propane for heating, cooking and transportation. C5 / C6 fraction 115 is isomerized into motor gasoline using commercial petroleum refining technology known to those skilled in the art. C5 / C6 isomerization technology includes UOP PENEX and Axens ATIS-2L processes. It is reported that the octane number of isomerized C5 / C6 fraction is as high as 92, which can be used as a direct replacement or supplement for petroleum gasoline.

[0060] In some embodiments where the only polyol added for esterification is sorbitol, a pure n-hexane fraction is recovered instead of a mixed C5 / C6. In such embodiments, n-hexane can be used in a variety of solvent applications, such as oilseed extraction. Examples of such oilseeds include, but are not limited to, rapeseed, canola, sunflower, and soybean.

[0061] The heavy hydrocarbon fraction 116 contains the aforementioned C15-C18 normal alkanes. This fraction is completely in the diesel boiling range and can be used as a compression ignition fuel blending stock. The heavy hydrocarbon fraction 116 can also be hydrocracking / isomerized according to the methods disclosed in the prior art (e.g., U.S. Patents 7,846,323, 7,968,757 and 8,558,042) to provide direct replacement renewable diesel (drop-in RD) or provide sustainable aviation fuel. Example Example 1.

[0062] The continuous esterification system is operated according to the conditions described in the specification of this article. The esterification reaction process using six CSTRs in series increases in temperature within the range of about 175-250°C and pressure is about 345-375 mbar. The FOG feedstock containing a raw material blend including used cooking oil and distiller corn oil and an FFA content of about 20% by weight is preheated and fed to the first reactor. Industrial glycerol is added together with the FOG feedstock in an amount of about 15% by weight (based on the FOG feedstock). The total residence time in the six reactors is about four hours.

[0063] Samples were collected at sampling locations before and after the esterification system to measure the organochlorine content of the FOG feedstock and the esterification reactor effluent. Six samples were collected from each sampling location approximately every eight hours over a period of about two days, for a total of 12 samples. Each sample was then analyzed for organochlorine content on an XOSClora using monochromatic wavelength dispersive X-ray fluorescence according to ASTM D4929. The results are summarized in Figure 3 On average, the FOG feedstock had an organochlorine content of about 10 ppm, while the average organochlorine content of the esterification reactor effluent was about 3 ppm, achieving a reduction of about 70%. Example 2.

[0064] The FOG feedstock was subjected to a continuous esterification process in the same or similar manner as disclosed in Example 1. The FOG feedstock was a blend of feedstocks including distiller corn oil, used cooking oil, and brown grease, with an average FFA content of about 21% by weight. The FOG feedstock had an organochlorine content of about 17 ppm, which was reduced to 10 ppm after the esterification reaction, achieving a reduction of about 40%. Example 3.

[0065] The esterification reaction was carried out in batches using a 1L stirred round-bottom flask heated to about 235°C. The FOG raw material was fed into a reaction vessel and heated to the reaction temperature at a pressure of about 20 mbar. Once water and air were completely removed from the FOG raw material, industrial glycerol was added to the reaction vessel at a dosage rate of about 12 wt % (based on the raw material). A magnetic stirring bar was used to mix the reactor contents at a speed of about 300 rpm. The reaction was isothermally carried out for about five hours, during which all vapors and gases were discharged through the top port of the reaction vessel and through a condenser operating at about 60°C. All water vapor and any other condensable materials were collected from the condenser into a round-bottom flask, and any incondensable gases were discharged into a fume hood.

[0066] The FOG raw material used in this experiment was mainly used cooking oil. Before the esterification reaction, the FFA content was about 12% by weight and the organic chlorine content was about 22 ppm. After the reaction, the FFA content of the esterification product was less than 0.1% by weight, and the organic chlorine content was about 16 ppm, and the organic chlorine content was reduced by about 26%.

[0067] It can thus be seen that the present invention provides a highly advantageous method for removing organic chlorine from fats, oils and greases. While the present invention has been described in connection with what are presently considered to be the most feasible and preferred embodiments, it will be apparent to one skilled in the art that the present invention is not limited to the disclosed embodiments and that numerous modifications and equivalent arrangements may be made thereto within the scope of the invention, which scope should be accorded the broadest interpretation of the claims to encompass all equivalent structures and products.

[0068] The inventors hereby declare that it is their intention to determine and evaluate the fair and equitable scope of their invention through the doctrine of equivalents as it relates to any device, system, method, or article that does not materially depart from the present invention but is outside the literal scope of the present invention as set forth in the following claims.

Claims

1. A method for treating a FOG feedstock for hydrodeoxygenation, comprising the steps of: (a) mixing the FOG raw material and the polyol in an esterification reactor to provide an esterification product; (b) washing the esterification product with water to provide a water-washed product; as well as (c) separating the treated FOG light phase from the water-washed product, The organic chlorine content of the FOG raw material is between 10wppm and 50wppm, and the organic chlorine content of the treated FOG light phase is less than 5wppm.

2. The method according to claim 1, wherein the FFA content of the FOG raw material is greater than 5 wt%.

3. The method according to claim 1, wherein the FFA content of the FOG raw material is greater than 10 wt%.

4. The method of claim 1, wherein the FFA content of the FOG raw material is greater than 12 wt%.

5. The process of claim 1, wherein the esterification reactor is operated at a temperature between 150°C and 280°C.

6. The process of claim 1, wherein the esterification reactor is operated at a pressure between 0.1 psia and 7 psia.

7. The method of claim 1, wherein the FOG feedstock is contacted with water prior to mixing with the polyol.

8. The method of 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 of 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 treat gas to produce mixed hydrocarbons.

11. The method of claim 10, wherein the mixed hydrocarbons include C5 / C6 hydrocarbons for motor gasoline.

12. The method of claim 10, wherein the mixed hydrocarbons include n-hexane.

13. A treated FOG composition for hydrodeoxygenation comprising: (a) fatty acid esters of sorbitol, xylitol or erythritol; (b) fatty acid esters of glycerol; (c) an organochlorine concentration between 1 wppm and 5 wppm; and (d) A free fatty acid concentration of less than 5% by weight.

14. The composition of claim 13, wherein the composition is produced by esterifying a FOG feedstock with a polyol comprising xylitol or sorbitol.

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

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

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

18. A method for producing mixed hydrocarbons from a FOG feedstock, the method comprising the steps of: (a) mixing the FOG raw material and the polyol in an esterification reactor to provide an esterification product; (b) washing the esterification product with water to provide a water-washed product; (c) separating a treated FOG light phase from the water-washed product, wherein the organic chlorine content of the FOG raw material is between 10 wppm and 50 wppm, and the organic chlorine content of the treated FOG light phase is less than 5 wppm; and (d) subjecting the treated FOG light phase to a hydrodeoxygenation process by contacting the treated FOG light phase with a hydrogen-rich treat gas to produce mixed hydrocarbons.

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

20. The method of claim 18, wherein the hydrodeoxygenation process produces hydrocarbons in one of a diesel boiling range and a gasoline boiling range.

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