Method for Removing Chlorine from Fats, Oils and Greases

Abstract

An improved method for removing contaminants from low-value waste fats and oils for the purpose of hydrodeoxygenation of diesel boiling range hydrocarbons. The method includes adding water to a contaminated FOG stream, subjecting the mixture to heating, and mixing to promote a reaction between the water and the FOG to remove organically bound contaminants from fats, oils, and greases (FOG). The reacted FOG is then separated from the contaminants. The reacted FOG results in a reduction of organically bound chlorine contaminants.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims priority to U.S. Provisional Application No. 63 / 350,751, filed on June 9, 2022, which is incorporated herein by reference in its entirety.

[0002] This technology relates to biofuels, and more particularly to biomass - based diesel fuels. Specifically, the present invention relates to an improved method for removing contaminants from low - value waste fats and oils for the purpose of hydrodeoxygenation to diesel - boiling - range hydrocarbons.

Background Art

[0003] Renewable hydrocarbons are becoming increasingly important in the world economy as a way to reduce the carbon intensity of hydrocarbon products such as fuels. The most common renewable hydrocarbon product used today is renewable diesel. However, additional renewable hydrocarbons such as renewable naphtha, sustainable aviation fuel, and renewable propane are also extremely important. Hydrodeoxygenation (HDO) of lipids is an important step in the production of renewable hydrocarbons. Commercially interesting lipid feedstocks include by - products of ethanol production, animal rendering, and food processing industries, such as distillers corn oil, inedible animal fats, and used cooking oil, respectively. These feeds are typically characterized by a high free fatty acid (FFA) content exceeding 5 wt.%, as well as relatively high levels of metals and phosphorus (typically exceeding a total of 20 wppm), and an alkalinity value of over 200 mg / kg. Certain lipid feedstocks also typically contain high levels of chlorine exceeding 5 wppm.

[0004] Chlorine can exist in lipids in both water-soluble (WS) and water-insoluble (WIS) forms. WS chlorine generally is in the form of chlorinated glycerols (i.e., monochloropropanediols), chloride salts (e.g., sodium chloride, potassium chloride), sodium hypochlorite (i.e., bleach), hydrochloric acid, and other chlorinated polar molecules. These impurities can be easily removed from lipid feedstocks using conventional lipid pretreatment steps such as water washing, and thus do not pose significant material concerns for the production of renewable fuels. On the other hand, WIS chlorine is not easily removed from lipid feedstocks using conventional pretreatment steps. WIS chlorine is present in lipids mainly in the form of fatty acid esters of monochloropropanediol (MCPD) isomers 2-MCPD and 3-MCPD, or chlorinated fatty acids (CFA). The molecular structures of typical 2-MCPD and CFA compounds are shown in FIGS. 1 and 2, respectively. MCPD may be in the form of chlorinated monoglycerides or chlorinated diglycerides and has been reported as the most common occurrence form in chlorinated vegetable oils. CFA may 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. WIS chlorine may also be present in lipids by the introduction of chlorinated hydrocarbons used as detergents, heat transfer fluids, or other industrial additives. Analysis of commercially available brown greases has shown the presence of chloroethane, chloroform, chloromethane, 1,2-dichloroethylene, tetrachloroethylene, and trichloroethylene at ppm levels (Ward, P.M.L. Journal of Food Protection, 2012, 75(4); 731-737).

[0005] Current methods of lipid pretreatment include degumming / acidity treatment, physical and chemical refining (including modified caustic refining where the oil is treated with a silica adsorbent as described in U.S. Pat. Nos. 5,231,201 and 5,298,639), and bleaching (as described in U.S. Pat. Nos. 7,179,491 and 8,394,975). Reduction of the 3-MCPD content of lipids is cited in U.S. Patent Publication No. 2020 / 0056116. However, the methods include refining and bleaching, followed by deodorization, whereby the yield of the treated oil is reduced by stripping of FFA and lighter oil fractions. Generally, prior art pretreatment methods do not achieve the chlorine reduction levels for optimal HDO reactor performance. Further, existing methods of lipid pretreatment have little effect on WIS chlorine and can only moderately reduce WS chlorine species. Since the HDO process converts WIS chlorine to hydrochloric acid, chlorine poses problems inherent in the production of renewable hydrocarbons, which is a concern for significant corrosion of common structural materials. In particular, austenitic stainless steels (e.g., 300 series 304 and 316) are very susceptible to the effects of chloride stress corrosion cracking due to exposure to chlorides, resulting in cracks in local areas of high stress in the metal, which is a concern for the critical mechanical integrity of high-pressure components. Accordingly, there is a substantial need for a technology that can reduce the concentrations of chlorides and WS chlorides, particularly for the production of renewable hydrocarbons by hydrogenation treatment of lipids.

[0006] There are existing methods for removing common impurities such as phosphorus, iron, sodium, potassium, calcium, and magnesium. These and other common impurities are typically removed by a combination of processes such as water washing, acidification, adsorbent filtration, absorbent filtration, degumming, or any combination of two or more of these steps.

[0007] Existing methods also teach hydrolysis as an effective means of increasing the FFA content of lipid feedstocks. This process, often referred to as lipolysis, has conventionally been used for the purpose of producing purified fatty acid and / or purified glycerol streams. Exemplary methods for hydrolyzing lipid feedstocks include enzymatic hydrolysis, catalytic hydrolysis using catalysts such as zinc oxide, the Twitchell process, and the Colgate-Emery process. The Colgate-Emery process uses a countercurrent liquid-liquid contactor to react clean lipids with water at about 490°F to achieve hydrolysis greater than 90% of the feedstock. This is the most widely used commercial hydrolysis process. Despite being a relatively well-understood process, the prior art does not mention the use and application of hydrolysis for removing chlorine and other impurities from waste lipid feedstocks for the production of renewable hydrocarbons.

[0008] In U.S. Patent No. 10,071,322 B2, Coppola et al. describe a "hydrothermal cleaning" or "HCU" process for the rapid and complete hydrolysis of lipid feedstocks at temperatures higher than those utilized in the Colgate-Emery process, e.g., 300 - 500°C as opposed to 250 - 260°C. Coppola et al. teach that complete hydrolysis of the lipid feedstock results in a clean oil with low levels of inorganic impurities such as phosphorus, potassium, sodium, silicon, iron, magnesium, barium, calcium, copper, magnesium, and zinc. Similar to other prior art, the HCU process promotes complete hydrolysis, which is described as being close to the theoretical maximum of free fatty acid from bound fatty acids, or about 100% complete conversion. Further, despite stating that the HCU process can remove inorganic impurities, Coppola et al. do not mention the effect of the HCU process on the removal of chlorine from chlorine-contaminated lipid feedstocks.

[0009] The prior art cited by Coppola et al. teaches that the removal of contaminants is achieved by substantially complete hydrolysis. However, the complete hydrolysis of fatty acid glycerides is generally not advantageous for the production of renewable fuels via HDO. The removal of bound glycerol from fatty acid glycerides leads to the loss of propane co-products. Furthermore, during the processing of very high FFA feedstocks, certain specific corrosion concerns arise.

[0010] Therefore, the need for a lipid feedstock pretreatment process that can remove chlorine from lipid feedstocks for the production of renewable hydrocarbons remains unmet. Furthermore, a hydrolysis-based pretreatment method for an HDO reactor that achieves high contaminant removal without significant loss of bound glycerol from fatty acid glycerides is needed. SUMMARY OF THE INVENTION

[0011] One aspect of the present invention relates to a method for removing organically bound contaminants from fats, oils, and greases (FOG). The method includes adding water to a contaminated FOG stream, as well as subjecting the mixture to heating and mixing to promote a reaction between the water and the FOG, followed by separating the reacted FOG from the removed contaminants. Thus, the reacted FOG results in a reduction of organically bound chlorine contaminants.

[0012] These and other objects and advantages of the present 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 in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013]

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[0014] Various embodiments will be described below. It should be noted that the specific embodiments are not intended as an exhaustive description or as a limitation to a broader aspect considered herein. One aspect described in connection with a particular embodiment is not necessarily limited to that embodiment and can be implemented in any other embodiment.

[0015] As used herein, "about" means plus or minus 10% of a particular term. The use of the terms "a," "an," and "the" and similar referents in the context of describing an element (especially in the context of the following claims) should be construed to include both the singular and the plural unless otherwise indicated herein or clearly contradicted by the context. The recitation of a range of values herein is merely intended to serve as a shorthand method of referring individually to each separate value within the range, and each separate value is incorporated herein as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or clearly contradicted by the context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein is merely intended to better illuminate embodiments and does not limit the claims unless otherwise specified. No language in this specification should be construed as indicating any non-claimed element as essential.

[0016] Hydroprocessing as used herein describes various types of catalytic reactions that occur in the presence of hydrogen, including but not limited to. Examples of the most common hydroprocessing reactions include hydrogenation, hydrodesulfurization (HDS), hydrodenitrogenation (HDN), hydrotreating (HT), hydrocracking (HC), aromatic saturation or hydrodearomatization (HDA), hydrodeoxygenation (HDO), decarbonylation (DCO), hydroisomerization (HI), hydrodewaxing (HDW), hydrodemetallization (HDM), decarbonylation, methanation, and reforming, but are not limited thereto. Depending on the type of catalyst, reactor configuration, reactor conditions, and composition of the feedstock, multiple reactions can be carried out ranging from purely thermal reactions (i.e., those not requiring a catalyst) to catalytic reactions. When describing the main function of a particular hydroprocessing unit, such as an HDO reaction system, it is understood that the HDO reaction is only one of the main reactions being carried out and other reactions may also occur.

[0017] Hydrotreatment (HT) involves removing elements of Group IIIa, Group Va, Group VIa, and / or Group VIIa of the periodic table from organic compounds. Hydrotreatment may also include hydrodemetallization (HDM) reactions. Thus, hydrotreatment includes removing heteroatoms such as oxygen, nitrogen, sulfur, and any combination of two or more thereof by hydroprocessing. For example, hydrodeoxygenation (HDO) is understood to mean removing oxygen by a catalytic hydroprocessing reaction to produce water as a by-product. Similarly, hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) represent the respective removal of the indicated elements by hydroprocessing. Hydroprocessing is also understood to include removing covalently bonded chlorine to produce hydrochloric acid as a by-product.

[0018] Water-insoluble (WIS) chlorine is defined as chlorine present in the lipid feedstock that is not washed away when contacted with water under ambient conditions (i.e., room temperature). Without being bound by any particular theory, it is assumed that WIS chlorine is covalently bonded to a lipid or hydrocarbon and is most commonly a chlorine moiety as either a chlorinated fatty acid or a chlorinated glyceride.

[0019] Water-soluble (WS) chlorine is defined as chlorine present in the lipid feedstock that is readily washed away when contacted with water under ambient conditions (i.e., room temperature). WS chlorine is assumed to be mainly one of chlorinated glycerols (i.e., monochloropropanediol), chloride salts (e.g., sodium chloride, potassium chloride), sodium hypochlorite (i.e., bleach), hydrochloric acid, or other chlorinated polar molecules. When a composition is described as containing "C 12 -C i -C j hydrocarbons" such as n-paraffins, this is understood to mean that the composition contains one or more paraffins having a carbon number falling within the range of i to j.

[0020] "Middle cut" generally refers to petroleum fractions in the range of about 200°F (93°C) to about 800°F (427°C). This includes kerosene (about 200 - 520°F), diesel and light gas oil (about 400 - 650°F), and heavy gas oil (about 610 - 800°F).

[0021] As used herein, "lipid" refers to fats, oils, and greases. Lipids are composed of saturated and unsaturated fatty acids in the range of C8 - C 24 and can exist in the form of esters of glycerol (i.e., as mono, di, and triglycerides) or as free fatty acids (FFA).

[0022] The term "monochloropropanediol" or "MCPD" is defined as a chlorinated glycerol molecule in which one oxygen moiety is replaced by a chlorine moiety. The chlorine moiety can be present at the 1-, 2-, or 3-position. The term monochloropropanediol or MCPD as used herein can also be understood to refer to both a chlorinated glycerol moiety bound to a fatty acid via an ester bond or a chlorinated glycerol present as a free alcohol.

[0023] The term "bound glycerol" is defined as glycerol that is bound to a fatty acid via an ester bond, as found in mono, di, and triglycerides. When used herein, the term bound glycerol can also be understood to include monochloropropanediol bound to a fatty acid.

[0024] The term "free glycerol" is defined as glycerol that exists as a free alcohol and is not bound to any fatty acid via an ester linkage. As used herein, the term bound glycerol can also be understood to include MCPD. Glyceride or total glyceride is the sum of monoglyceride, diglyceride, and triglyceride. The total glyceride content is a measure of the bound glycerol in the lipid, and glyceride conversion is a measure of the glycerol released by the conversion of glyceride to FFA via hydrolysis.

[0025] It should be understood that the "volume percent" or "vol.%" of a component in a composition, or the volume ratio of different components in a composition, is determined at room temperature (about 23°C) based on the initial volume of each individual component, rather than the final volume of the combined components.

[0026] One aspect of the present invention relates to a method for producing a pretreated lipid feedstock having a total chlorine and WIS chlorine concentration lower than the starting or unadjusted total chlorine and WIS chlorine concentration. Table 1 shows the typical total chlorine and WIS chlorine contents of various unadjusted waste lipid feedstocks.

[0027] In one aspect, a method is provided for producing a preconditioned lipid feedstock having both a WIS chlorine and phosphorus concentration lower than the starting or unadjusted WS chlorine and phosphorus concentration. Table 1 shows the typical WIS chlorine and phosphorus contents of various unadjusted waste lipid feedstocks. [Table 1]

[0028] The method includes first contacting a waste lipid feedstock stream with a water stream, and then subjecting the combined stream to a sufficient temperature, and mixing to produce a chlorine-reduced lipid stream and a chlorine-enriched heavy phase. In some embodiments, an acid catalyst is added to the mixture to facilitate the conversion of WIS chlorine to WS chlorine. In some embodiments, the pretreated lipid feedstock has a higher FFA concentration than the non-pretreated lipid feedstock.

[0029] Exemplary lipid feedstocks include, but are not limited to, animal fats, animal oils, microbial oils, vegetable fats, vegetable oils, plant fats, vegetable oils, greases, or any two or more mixtures thereof. Vegetable and / or plant oils and / or microbial oils include, but are not limited to, corn oil, non-edible corn oil, babassu oil, carinata oil, soybean oil, canola oil, coconut oil, rapeseed oil, tall oil, tall oil fatty acids, palm oil, palm oil fatty acid distillate, jatropha oil, palm kernel oil, sunflower oil, castor oil, camelina oil, archaeal oil, bacterial oil, fungal oil, protozoal oil, algal oil, seaweed oil, oil from halophilic bacteria, and any two or more mixtures thereof. These can be classified as crude, degummed, and RBD (refined, bleached, and deodorized) grades depending on the level of pretreatment and the residual phosphorus and metal content. However, any of these grades may be used in the present technology. Animal fats and / or oils used above include, but are not limited to, non-edible tallow, edible tallow, industrial tallow, floating tallow, lard, poultry fat, poultry oil, fish fat, fish oil, and any two or more mixtures thereof. Greases can include, but are not limited to, yellow grease, brown grease, waste vegetable oil, restaurant grease, trap grease from local governments such as water treatment facilities, and used oil from industrial packaging food operations, and any two or more mixtures thereof.

[0030] Depending on the level of pretreatment, such a bio-renewable lipid feedstock can contain from about 1 wppm to about 800 wppm of phosphorus, and from about 1 wppm to about 400 wppm of total metals (mainly sodium, potassium, magnesium, calcium, iron and copper). The lipid can also contain up to about 40 wt.% free fatty acid %. The FFA content of the lipid can be about 1 wt.%, about 2 wt.%, about 3 wt.%, about 4 wt.%, about 5 wt.%, about 6 wt.%, about 7 wt.%, about 8 wt.%, about 9 wt.%, about 10 wt.%, about 11 wt.%, about 12 wt.%, about 13 wt.%, about 14 wt.%, about 15 wt.%, about 16 wt.%, about 17 wt.%, about 18 wt.%, about 19 wt.%, about 20 wt.%, about 30 wt.%, about 32 wt.%, about 34 wt.%, about 36 wt.%, about 38 wt.%, about 40 wt.%, or any two of these values and / or any range between them.

[0031] The lipid feedstock contains fatty acid-bound glycerol (or simply bound glycerol) in the form of glycerides (the sum of monoglycerides, diglycerides, and triglycerides). The lipid feedstock can contain up to 90 wt.% glycerides. The glyceride content of the lipid feedstock can be between about 20 wt.%, about 30 wt.%, about 40 wt.%, about 50 wt.%, about 60 wt.%, about 70 wt.%, or about 90 wt.%, or between any two values within this range. For example, the lipid feedstock can contain a glyceride content within the range of 20 wt.% to 90 wt.%, or within the range of 30 wt.% to 80 wt.%.

[0032] The lipid feedstock can contain up to about 1000 wppm total chlorine. The total chlorine content of the lipid can be about 1 wppm, 2 wppm, 3 wppm, 4 wppm, 5 wppm, 6 wppm, 7 wppm, 8 wppm, 9 wppm, 10 wppm, 20 wppm, 30 wppm, 40 wppm, 50 wppm, 60 wppm, 70 wppm, 80 wppm, 90 wppm, 100 wppm, 110 wppm, 120 wppm, 130 wppm, 140 wppm, 150 wppm, 160 wppm, 170 wppm, 180 wppm, 190 wppm, 200 wppm, 300 wppm, 400 wppm, 500 wppm, 600 wppm, 700 wppm, 800 wppm, 900 wppm, 1000 wppm, or any two of these values and / or any range therebetween. The lipid feedstock can also contain up to about 200 wppm WIS chlorine. The WIS chlorine content of the lipid can be about 1 wppm, 2 wppm, 3 wppm, 4 wppm, 5 wppm, 6 wppm, 7 wppm, 8 wppm, 9 wppm, 10 wppm, 20 wppm, 30 wppm, 40 wppm, 50 wppm, 60 wppm, 70 wppm, 80 wppm, 90 wppm, 100 wppm, 110 wppm, 120 wppm, 130 wppm, 140 wppm, 150 wppm, 160 wppm, 170 wppm, 180 wppm, 190 wppm, 200 wppm, or any two of these values and / or any range therebetween.

[0033] Accordingly, the lipid feedstock of any embodiment herein can include corn oil, distillers corn oil, non-edible corn oil, babassu oil, karanja oil, soybean oil, canola oil, palm oil, rapeseed oil, tall oil, tall oil fatty acids, palm oil, palm fatty acid distillate, jatropha oil, palm kernel oil, sunflower oil, castor oil, camelina oil, archaeal oil, bacterial oil, fungal oil, protozoal oil, algal oil, seaweed oil, oil from halophilic bacteria, rendered fat, non-edible tallow, edible tallow, industrial tallow, floating tallow, lard, poultry fat, poultry oil, fish fat, fish oil, fryer oil, yellow grease, brown grease, waste vegetable oil, restaurant grease, trap grease from local governments such as water treatment facilities, and used oil from industrial packaging food operations, or any two or more mixtures or combinations thereof.

[0034] Surprisingly, when a chlorine-containing lipid feedstock is reacted with water at a temperature of about 500°F for 15 to 360 minutes, it was observed that the chlorine content of the lipid feedstock was reduced to 99%. Further, surprisingly, it was observed that the reaction conditions can be controlled such that the reaction of the chlorine-containing lipid feedstock with water results in a higher degree of chlorine removal than the removal of bound glycerol. With respect to glyceride conversion, the rate of WIS chlorine removed from the lipid exceeds the rate of glyceride conversion therein, enabling the reaction to be optimized to achieve the desired balance of WIS chlorine removal and bound glycerol content in the product.

[0035] The conversion of glycerides (the sum of mono-, di- and triglycerides representing the bound glycerol compounds in the lipid) is less than 90%. In an embodiment, the glyceride conversion is less than 85%. In an embodiment, the glyceride conversion is less than 80%. For example, the glyceride conversion can be about 75%, about 70%, about 65%, about 60%, about 55%, about 50%, about 45%, or about 40%, or between any two of these values. For example, the glyceride conversion is 40% - 90%, or 45% - 85%.

[0036] The chlorine-reduced product according to the present technology contains at least about 8 wt.% glyceride content (total of mono, di, and triglycerides representing bound glycerol compounds in lipids). In embodiments, the product contains about 10 wt.%, about 12 wt.%, about 14 wt.%, about 16 wt.%, about 18 wt.%, about 20 wt.%, about 22 wt.%, about 24 wt.%, about 26 wt.%, about 28 wt.%, about 30 wt.%, about 32 wt.%, about 34 wt.%, about 36 wt.%, about 38 wt.%, about 40 wt.%, about 42 wt.%, about 44 wt.%, about 46 wt.%, about 48 wt.%, or about 50 wt.% glyceride. In products containing glyceride content between any two values within this range. Thus, the chlorine-reduced product can contain about 10 wt.% - 50 wt.% glyceride, or 20 wt.% - 40 wt.% glyceride.

[0037] Other aspects of the method are more generally described with reference to Figure 3. Figure 3 is a schematic diagram of one embodiment of the present invention in which a lipid feed stream 101 is contacted with a water stream 102 and reacted within a reactor system 100. In some embodiments, the water stream 102 can be liquid water, steam, or any combination thereof. In some embodiments, the lipid feed stream 101 may undergo a pretreatment step before entering the reactor 100. The pretreatment step can include one of water washing, acidification (e.g., phosphoric acid, citric acid, etc.), caustic neutralization (e.g., sodium hydroxide, potassium hydroxide, etc.), adsorbent filtration (e.g., silica hydrogel, bleaching clay, ion exchange resin, etc.), absorbent filtration (e.g., diatomaceous earth, cellulose, etc.), FFA stripping, degumming (e.g., water degumming, acid degumming, etc.), or any combination of two or more of these steps.

[0038] Regardless of the pretreatment method, the feedstock 101 has a WIS chlorine content of 5 wppm - 200 wppm. In some embodiments, the feedstock 101 has a WIS chlorine content of 10 wppm - 100 wppm.

[0039] The reactor 100 is operated at a temperature of 450 - 500°F for 15 - 360 minutes. The reactor system 100 may be operated in batch mode or continuous mode. In some embodiments, the reactor 100 can be a continuous stirred tank reactor (CSTR), a stirred batch reactor, a co-current liquid-liquid contactor, a counter-current liquid-liquid contactor, a static mixer, a high-shear in-line mixer, or other liquid reactors known to those skilled in the art. Embodiments of batch reactors include facilities for heating and agitation. Heating can be provided by the circulation of steam or a heat transfer fluid (hot oil) through a reactor jacket or heating coil, while agitation is provided by a mechanical agitation device, steam sparging, and / or a pump around the circulation. Continuous reactors include a single CSTR or multiple CSTRs in series such that the tank volume provides a residence time of 15 - 360 minutes required for the conversion. Other embodiments of continuous reactors include a counter-current water contact column (with facilities for steam injection), or a tubular reactor with a steam-jacketed pipe network where the lipid / water turbulence is maintained in the desired temperature range for at least 15 minutes. In embodiments, the reactor system includes one or more of these reactors. Regardless of the type of reactor, the system is maintained at a pressure high enough to ensure that water remains in the liquid phase. Typical pressures for the reactor system 100 range from 500 - 1200 psig.

[0040] Under these conditions, 40 to 90% of the glycerides in feedstock 101 are converted. Following reactor 100, the mixed effluent 105 is led to separator 110 to separate a phase with a density lower than water (i.e., the light phase) 111 and a phase with a density higher than water (i.e., the heavy phase) 112. In an embodiment, the light phase 111 is a lipid stream mainly containing glycerides and fatty acids, and the heavy phase 112 is an aqueous stream mainly containing water, glycerol, metal ions and salts. In an embodiment, the light phase 111 has a chlorine content that is 50 wt.%, 55 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, 85 wt.%, 90 wt.%, 95 wt.%, or 99 wt.% lower than the starting chlorine content of stream 101, or has any range between and / or including any two of these values. In some embodiments, the light phase 111 has a WIS chlorine content that is 50 wt.%, 55 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, 85 wt.%, 90 wt.%, 95 wt.%, or 99 wt.% lower than the starting WIS chlorine content of stream 101, or has any range between and / or including any two of these values.

[0041] Depending on the WIS chlorine content of feedstock 101, the light phase 111 has a WIS chlorine content of 0.2 to 10 wppm. In a preferred embodiment, the WIS chlorine content is less than 5 wppm.

[0042] Although not bound by theory, reduction of the WIS chlorine content of lipids can be achieved by two main routes. The first is to directly hydrolyze the chlorine moiety from the glycerol backbone of the fatty acid esters of MCPD to produce WS hydrochloric acid and fatty acid glyceride esters, as shown in FIGS. 4A and 4B. FIGS. 4A and 4B show the hydrolysis of the water-insoluble fatty acid esters of monochloropropanediol (MCPD) to produce water-soluble hydrochloric acid and fatty acid esters of glycerol. Either reaction 4A or reaction 4B may be carried out. The position of the chlorine moiety may vary such that chlorine may also be located at the terminal carbon rather than the internal carbon, as shown. The second is the hydrolysis of the WIS fatty acid moieties of the fatty acid mono- and diesters of MCPD to produce free fatty acids (FFAs) and MCPD, as shown in FIGS. 5A and 5B. FIGS. 5A and 5B show the stepwise reactions for the hydrolysis of the water-insoluble fatty acid esters of monochloropropanediol (MCPD) to produce free fatty acids (FFAs) and water-soluble MCPD. The reactions may also be carried out in a different order such that fatty acid R2 is removed in step 5A and fatty acid R3 is removed in step 5B. The position of the chlorine moiety may vary such that chlorine may also be located at the internal carbon rather than the external carbon, as shown. The hydrolysis of fatty acid glyceride esters to produce FFAs and glycerol according to the reaction schemes shown in FIGS. 6A, 6B, and 6C is a competing series of reactions that can occur simultaneously with the reaction schemes shown in FIGS. 4A and 4B and FIGS. 5A and 5B. As shown in FIGS. 4A and 4B, reactions 4A and 4B are the preferred routes for reducing the WIS chlorine content of lipids because these reactions produce neither FFAs nor free glycerol nor MCPD. The reactions shown in FIGS. 6A, 6B, and 6C may be carried out in a different order such that fatty acid (Rx) may be removed in any order in steps 6A, 6B, and 6C.

[0043] FFA is not desirable as a feedstock for the production of renewable hydrocarbons for a variety of reasons, including metallurgical effects, catalyst attrition, and reduced yields of renewable propane from the hydrotreating of glycerol. Similarly, free glycerol and MCPD have low solubility in hydrocarbons and are thus not desirable as feedstocks for HDO reactors that generally rely on hydrocarbon dilution for effective operation. Given these limitations, effective conversion of glycerol to propane in a renewable hydrocarbon conversion unit reactor requires that the glycerol remain bound to fatty acids as glycerides.

[0044] Surprisingly, it has been observed that the reaction within reactor 100 can be controlled to assist the dechlorination reaction such that the decrease in the total moles of bound glycerin (in the form of mono, di, and triglycerides) is less than the decrease in the total moles of chlorine in the light phase 111.

[0045] In embodiments, an acid or acidic solution is introduced into reactor 100 to reduce the pH of the contents of reactor 100 to less than 6, less than 5, less than 4, less than 3, less than 2, less than 1, or any range including and / or between any two of these values.

[0046] In embodiments, separator 110 may be a decanter, a stacked disk centrifuge, a horizontal centrifuge, a settling tank, a three-phase separator, or other liquid-liquid separation means known to those skilled in the art. In embodiments, reactor 100 and separator 110 may be in the same processing unit.

[0047] In embodiments, a heat exchanger or other temperature reducing means known to those skilled in the art is disposed between reactor 100 and separator 110 to reduce the temperature of stream 105 and assist in the separation of streams 111 and 112.

[0048] In some embodiments, the degree of chlorine removal can be controlled using an increase in the residence time within reactor 100. This can be achieved by controlling the level in a CSTR, the cycle time in a batch reactor, or the flow rate through a liquid-liquid contactor reactor.

[0049] In some embodiments, the light phase 111 has monoglycerides, diglycerides, triglycerides, and free fatty acids. In some embodiments, the glyceride content of the light phase 111 is greater than 20 wt% and the WIS chlorine content is less than 5 wppm.

[0050] The technology thus generally described is provided by way of example and will be more readily understood by reference to the following examples which are not intended to limit the technology.

[0051] Example Example 1. Reduction of WIS Chlorine and Impurities in Used Cooking Oil Using a Non-Catalytic Hydrolysis Reaction Used cooking oil samples obtained from various commercial restaurants in the United States were combined and subjected to a pretreatment process before the hydrolysis reaction. The UCO pretreatment process consisted of the following steps: acidification, shear mixing, neutralization, centrifugation, filtration, and drying. The UCO was placed in a beaker and stirred on a hot plate maintained at 80 °C, and was continuously metered at 44 mL / min from the beaker using a gear pump (Cole-Parmer 75211-10 micropump). This oil was then combined with an aqueous citric acid solution (9.89% wt in deionized water) metered at 1.38 mL / min using a piston pump (Eldex Optos 2HM). The UCO and the aqueous citric acid solution were mixed in a beaker placed on a hot plate, maintaining the liquid temperature at 60 °C. The mixing was performed by a high-shear mixer (Silverson L5M-A) operating at 1800 RPM. The liquid level in the beaker was set to achieve an average residence time of approximately 22 minutes. A second gear pump was used to meter the flow rate from the beaker and maintain a constant level. The UCO aqueous citric acid solution mixture was contacted with an aqueous sodium hydroxide solution (0.98% wt in deionized water) metered at 1.24 mL / min using a peristaltic pump (Ismatec 78017-07) to produce a neutralized composition. The neutralized UCO was pumped to a continuous centrifuge (CINC V-02) operating at 5700 RPM and maintained at a temperature of 60 °C. The heavy-phase weir was adjusted to minimize the light-phase water. The light phase from the centrifuge was then batch-filtered in a 1 L filter assembly (Millipore YT30 142HW) pressurized at a flow rate of 50 mL / min using a syringe pump (Teledyne 260D). The filtered oil was drawn from a flask on a stirred hot plate while maintaining the liquid temperature at 60 °C. The filter consisted, from bottom to top, of the following layers: a screen support and a metal screen, filter paper (Whatman cellulose Grade 5), diatomaceous earth, and silica hydrogel (W.R.Grace Trisyl 300). When the differential pressure reached 80 PSI, the pump was stopped and the filtered oil was purged using nitrogen.As a final processing step, the filtered oil was dried using a vacuum flask on a stirring hot plate while maintaining the liquid at approximately 95 °C, and a pressure of approximately 25 inches Hg was maintained using a vacuum pump. The removed moisture was collected in a cold trap. The characteristics of the pretreated UCO are shown in Table 2.

[0052] Next, the batch hydrolysis reaction was carried out in a 1 L 316 stainless steel stirred reactor (Autoclave Engineers EZE-Seal reactor system) using 405.36 g of deionized water and 376.84 g of the treated used cooking oil. Water was first placed in the reactor, which was then sealed and pressurized with nitrogen to approximately 800 PSIG. This pressure was chosen to well exceed the minimum pressure required to maintain water as a liquid at the reaction temperature of 260 °C. A magnetic drive mixer was set to approximately 1300 RPM, and a 1200 W electric heater was set to maintain an internal liquid temperature of 260 °C. Once the water was heated to the desired reaction temperature (260 °C), the pressure built up by heating was vented to return the reactor pressure to approximately 800 PSIG. The pretreated UCO was poured into a separate isolated 316 stainless steel supply cylinder (500 mL) maintained at approximately 60 °C by an electric heat tape. The supply cylinder was pressurized with nitrogen to a pressure higher than that of the 1 L reactor (approximately 1000 PSIG), and it was introduced into the reactor by opening a valve connected to a dip tube that terminated inside the reactor towards the mixer element. After the feed was introduced into the reactor, the pressure of the reactor was approximately 1000 PSIG, and a timer was started to indicate the start of the reaction. The reaction temperature instantaneously dropped to approximately 248 °C (indicating that the feedstock was successfully introduced into the reactor), but it was quickly heated back to the set point temperature. A needle valve connected to a dip tube extending into the reactor was opened, and liquid samples were periodically taken from the reactor by initiating the outflow from the reactor by the pressure difference from the reactor conditions to atmospheric pressure. The sample tube flowed through the inner tube of a double-tube heat exchanger, and in the larger diameter outer tube, domestic water flowing in countercurrent flowed through it. Since the internal pressure in the reactor decreased due to the sample collection procedure, the nitrogen supply valve was periodically opened to ensure that the flow to the reactor could maintain approximately 1000 PSIG.

[0053] After the pretreated UCO was charged into the reactor, reactor samples were collected after 3, 7, 11, 16, 30, 45, and 360 minutes. Thereafter, all the samples drawn from the reactor were washed with deionized water (about 5 mL of deionized water added to a 20 mL sample) and separated using a laboratory centrifuge (Ample Scientific, Champion F-33D) operating at 2800 RPM for 3 minutes. The light phase of the centrifuge was removed with a pipette and regarded as the water-insoluble (WIS) reaction product. This product was subjected to further analysis according to the method shown in Table 3 for the following sampling times (in minutes): 3, 7, 11, 16, 30, 45, and 360. The 360-minute sample represented the final reaction product after the experiment was completed.

Table 2-1

Table 2-2

Table 3

[0054] As shown in Table 3, the WIS chlorine reduction for the pretreated UCO (Table 2) was 46% reduction (12.27 PPM) within 7 minutes and 98.9% reduction (0.24 PPM) by the end of the reaction.

[0055] Further analysis of the data shown in Table 3 surprisingly revealed that the reduction of bound glycerol occurred at a much slower rate than the reduction of WIS chlorine. The moles of chlorine were calculated from the concentration data shown in Table 3 by multiplying the concentration by the total mass of the sample and then dividing by the molar mass of chlorine, 35.45 g / mol. Similarly, the moles of bound glycerol were calculated by multiplying the mass of the sample by the respective concentrations of monoglyceride, diglyceride, and triglyceride shown in Table 3 and then dividing by the molar masses of monoolein (356.54 g / mol), diolein (620.99 g / mol), and triolein (885.43 g / mol), respectively. Each mole of mono, di, and triglyceride represents 1 mole of bound glycerol.

[0056] Figure 7 shows the total moles of chlorine (y-axis) versus the total moles of bound glycerol (x-axis) as the reaction progresses. The solid straight line represents the virtual change in WIS chlorine if it were hydrolyzed proportionally to that of bound glycerol, and the dashed curve represents the actual change in chlorine for that of bound glycerol measured in this experiment. Without being bound by theory, if the reduction of chlorine followed the reaction network shown in Figures 5A and 5B, the actual results should be located either on or above the solid line, indicating that WIS chlorine, along with free glycerol, is removed as MCPD by complete hydrolysis of glyceride esters. However, since the dashed curve representing the actual experimental results is below the solid theoretical line, the data surprisingly suggests that the direct hydrolysis of chlorine from MCPD is the dominant reaction, as shown in Figures 4A and 4B. Therefore, complete (i.e., nearly theoretical) hydrolysis is not necessary to achieve significant dechlorination of lipids. For example, an 88% reduction in the moles of WIS chlorine was achieved, but only 33% of the bound glycerol was removed.

[0057] Another measure of the relative selectivity for chlorine removal with respect to glycerol liberation is the conversion of total glycerides. Starting from a total glyceride content of 70% (the sum of mono, di and triglycerides in Table 2), the results of this example summarized in Table 3 show that at a WIS chlorine level of 2.71 ppm (88% reduction of WIS chlorine), the conversion of glycerides is only 56% (see the results for the 30-minute reaction time in Table 3).

[0058] Example 2. Reduction of WIS chlorine in used cooking oil using a non-catalytic hydrolysis reaction In this example, the same pre-treated UCO as in Example 1 was subjected to the same conditions as in Example 1, but the sampling frequency was changed to obtain the results shown in Table 4.

Table 4

[0059] As shown in Table 4, the results were similar to those shown in Table 3 of Example 1. In this example, WIS chlorine was reduced by 39.4% after 15 minutes (13.66 PPM), and chlorine was reduced by 98.6% after 300 minutes (0.33 PPM).

[0060] Example 3. Reduction of WIS chlorine in used cooking oil using an acid-catalyzed hydrolysis reaction The batch hydrolysis reaction was carried out in a 1 L 316 stainless steel stirred reactor (Parr Instrument Company, 4525 benchtop reactor system) using 316.75 g of deionized water, 268.6 g of the pretreated UCO described in Example 1 and Table 1, and 10.93 g of sulfuric acid (95% wt in water). Water, the pretreated UCO, and sulfuric acid were added to the reactor, which was then sealed. A 1 / 8 hp magnetic drive mixer was turned on to about 25%, and a 1000 W electric heater, which is part of the Parr 4525 reactor system, was set to maintain an internal temperature of 204 °C. The internal temperature was maintained at the set point of 204 °C by an external temperature control unit (Parr Instrument Company, 4848 reactor controller). No cooling water was used for temperature control. The reaction pressure is the equilibrium pressure of the reactor contents at 204 °C, which is expected to be about 230 - 235 PSIG. It took about 1 hour for the reaction mixture to reach the desired reaction temperature of 204 °C, at which point the first sample was obtained. A 1 / 2 inch OD sample tube (316 stainless steel) with a volume of about 20 mL was assembled using needle valves at both ends. The bottom needle valve was opened to the atmosphere, and the top needle valve was connected to the dip tube of the reactor with a 1 / 4 inch tube. The dip tube terminates near the bottom of the reactor. The sample tube was placed in a thermally insulated open-top container filled with domestic water and cooled before handling the sample. When the top needle valve was opened, the reactor material flowed into the sample tube due to the pressure difference between the reactor and the sample tube (atmospheric pressure). After a time allowing for cooling, the sample tube was removed from the water bath, the bottom needle valve was slowly opened to depressurize the sample tube, and the sample was recovered. The recovered sample was then washed with deionized water (about 5 mL of deionized water added to the 20 mL sample) and separated in a laboratory centrifuge (Ample Scientific, Champion F-33D) operating at 2800 RPM for 3 minutes. The light phase oil after the centrifugation step was removed with a pipette and considered the water-insoluble (WIS) reaction product. This product was subjected to further analysis according to the method shown in Table 5 for the following sampling times (in hours): 1, 2, 3, 4, 5, 6. The 6-hour sample represented the end of the reaction.

Table 5

[0061] As shown in Table 5, the final WIS chlorine value is 3.76 PPM, which is an 83.5% reduction from the initial value (22.85 PPM shown in Table 2).

[0062] Example 4. Reduction of WIS Chlorine in Used Cooking Oil Using Non-Catalytic Hydrolysis Reaction Using 330.55 g of deionized water and 278.43 g of the pretreated UCO described in Example 1, a batch hydrolysis reaction was carried out in a 1 L 316 stainless steel stirred reactor described in Example 3. The water and pretreated UCO were added to the reactor, which was then sealed. A 1 / 8 hp magnetic drive mixer was turned on to about 25%, and a 1000 W electric heater, which is part of the Parr 4525 reactor system, was set to 260 °C (based on internal temperature measurement). The internal temperature was maintained at the set point of 260 °C by an external temperature control unit (Parr Instrument Company, 4848 reactor controller). No cooling water was used for temperature control. The reaction pressure is the equilibrium pressure of the reactor contents at 260 °C, which is expected to be about 650 PSIG. The reaction mixture took slightly longer to reach the set point compared to Example 3, but a first sample was obtained after a 1-hour reaction at which time the temperature was about 235 °C. The sample collection and water washing procedures for the samples in this example were the same as those described in Example 3. Samples from this example were subjected to further analysis according to the method shown in Table 6 for the following sample collection times (in hours): 1, 2, 3, 6, and 7.

Table 6

[0063] Compared with Table 5 of Example 3 where the hydrolysis reaction was catalyzed with sulfuric acid and carried out at a lower temperature of 204 °C, Table 6 shows improved WIS chlorine reduction. After 1 hour, the WIS chlorine was reduced by 57.9% (9.63 PPM), and after 3 hours it was reduced by 99.6% (0.10 PPM).

[0064] Accordingly, it can be seen that the present invention provides a very advantageous method for removing contaminants from fats, oils, and greases. The present invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, but the invention is not limited to the disclosed embodiments, and many modifications and equivalent arrangements within the scope of the present invention can be made, and it will be apparent to those skilled in the art that the scope should be given the broadest interpretation of the appended claims so as to encompass all equivalent structures and products.

Claims

1. A method for reducing the chlorine content of lipid supply raw materials, A step of supplying a lipid feedstock having a chlorine content higher than 5 wppm and a free fatty acid content of approximately 5 to 40 wt.% to a hydrolysis reactor. The steps include bringing the lipid supply material into contact with a water flow and an acid catalyst, The steps include: mixing the lipid supply material and the water flow with an acid catalyst to produce a mixed effluent; and The step of separating the mixed effluent into a chlorine-reduced light phase and a chlorine-enriched heavy phase. Includes, A method wherein the chlorine-reducing light phase has a molar reduction of bound glycerol that is less than 50% of the molar reduction of chlorine.

2. The method according to claim 1, wherein the lipid supply material and the water flow are mixed at a temperature of approximately 450 to 550°F.

3. The method according to claim 1, wherein the acid catalyst is sulfuric acid.

4. The method according to claim 1, wherein the chlorine content of the lipid supply raw material is higher than 15 wppm.

5. The method according to claim 1, wherein the chlorine content of the lipid supply raw material is higher than 20 wppm.

6. The method according to claim 1, wherein the chlorine-reduced light phase has a chlorine content of less than 60% of the chlorine content of the lipid supply raw material.

7. The method according to claim 1, wherein the chlorine-reduced light phase has a chlorine content of less than 50% of the chlorine content of the lipid supply raw material.

8. The method according to claim 1, wherein the chlorine-reduced light phase has a chlorine content of less than 20% of the chlorine content of the lipid supply raw material.

9. The method according to claim 1, wherein the chlorine content is water-insoluble chlorine.

10. The method according to claim 1, further comprising subjecting the chlorine-reduced light phase to a hydrogenation process to produce a regenerative hydrocarbon.

11. The method according to claim 1, wherein the total glyceride content (sum of mono, di, and triglycerides) of the chlorine-reduced light phase is at least 18 wt.%.

12. A method for removing water-insoluble (WIS) chlorine from lipid supply material, A step of supplying a lipid feedstock containing approximately 5-40 wt.% free fatty acids to the reactor. A step of generating a mixed effluent by contacting the lipid supply material with a water flow and an acid catalyst at a temperature of 450 to 550°F, and The step of separating the mixed effluent into a chlorine-reduced light phase and a chlorine-enriched heavy phase. A method comprising the lipid supply material having a total glyceride content of less than 90 wt.% and a WIS chlorine content of more than 10 wppm, the reactor being operated to convert less than 70% of the glycerides, and the chlorine reduction light phase having a WIS chlorine content of less than 5 wppm.

13. The method according to claim 12, wherein the chlorine-reduced light phase has a glyceride content higher than 18 wt.%.

14. A method for reducing the chlorine content of lipid supply raw materials, A step of supplying a lipid feedstock having a chlorine content higher than 5 wppm and a free fatty acid content of approximately 5 to 40 wt.% to a hydrolysis reactor. A step of bringing the lipid supply material into contact with a water flow, A step that mixes the lipid supply raw material, the water flow, and the acid catalyst to produce a mixed effluent, The steps of separating the mixed effluent into a chlorine-reduced light phase and a chlorine-enriched heavy phase, The step of subjecting the chlorine-reduced light phase to a hydrogenation process to produce regenerative hydrocarbons. Includes, A method wherein the chlorine-reducing light phase has a molar reduction of bound glycerol that is less than 50% of the molar reduction of chlorine.

15. The method according to claim 14, wherein the lipid supply material has a total glyceride content of less than 90 wt.% and a WIS chlorine content of more than 10 wppm, the reactor is operated to convert less than 70% of the glycerides, and the chlorine reduction light phase has a WIS chlorine content of less than 5 wppm.

16. The method according to claim 14, wherein the chlorine content of the lipid supply raw material is higher than 10 wppm.

17. The method according to claim 14, wherein the chlorine content of the lipid supply raw material is higher than 15 wppm.

18. The method according to claim 14, wherein the chlorine-reduced light phase has a chlorine content of less than 60% of the chlorine content of the lipid supply raw material.

19. The method according to claim 14, wherein the chlorine-reduced light phase has a chlorine content of less than 50% of the chlorine content of the lipid supply raw material.

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