Patent Application
20050232956
The present invention generally relates to a method of processing fatty acids. The present invention particularly relates to a method for separating saturated and unsaturated fatty acids. Separated fractions of fatty acid esters are useful as fuels.
Urea is known to form inclusion complexes with long chain organic compounds. This was first discovered and reported by F. Bengen in a German patent filed in 1940. Later studies from the late forties to the early fifties reported the selectivity of urea in forming complexes with long chain organic molecules. This selectivity was found to be based on; a) Carbon chain length, b) presence of unsaturation in the molecule, and c) degree of unsaturation. The formation of these complexes was found to be a powerful technique for the separation of a mixture of saturated and unsaturated organic compounds, e.g. fractionation of a mixture of free fatty acids. Various techniques for the formation of such complexes were also studied, however with little or no focus on the process parameters. Work done by Hayes et al., on the fractionation of fatty acids studied various process parameters that effect the formation of urea inclusion complexes, the product yields, and the composition of fractions obtained. Patents U.S. Pat. No. 5,106,542, U.S. Pat. No. 5,243,046 describe the art of fractionating fatty acid mixtures via urea inclusion. U.S. Pat. No. 5,679,809 describes the concentration of polyunsaturated fatty acid ethyl esters via urea inclusion.
Fatty acid esters find a variety of uses including in foodstuffs, nutritive compositions, pharmaceuticals, cosmetics, dermatological compositions, and drying oils for coatings and paints.
Biodiesel, according to ASTM D-6751 specification, is defined as a fuel comprised of mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats. The alkyl group is of the type CnH2n+1, preferable methyl (CH3), the oil source is preferable soybean. Biodiesel derived from a soy oil source is referred to as SME (soy methyl esters) or soy biodiesel, EtOH refers to ethanol, and urea. elsewhere in the text.
All of the above references are incorporated herein by reference.
Methods in the art for fractionating SME to improve its cold flow properties are based on thermal crystallization (winterization) followed by filtration (with or without solvent). Both techniques rely on the difference in crystallization temperature of the saturated and unsaturated components of SME. The saturates crystallize at a higher temperature and can be removed via filtration, centrifugation etc. However, due to co-crystallization of the components significant amounts of unsaturates are also removed, resulting in high losses. For a C.P. of −16 C almost 75% of the starting material was removed in work done by Dunn et al. These techniques involve cooling to very low temperatures and process time running into days. It would be advantageous to identify a method for separation of fatty acid methyl esters applicable to industrial scale application.
This invention relates to the fractionation/separation of fatty acid methyl esters, specifically SME into saturated fatty acid-rich and unsaturated fatty acid-rich fractions via the use of urea inclusion/urea complexation. Operation of diesel engines using renewable energy sources including soy bean derived fuels is known, as is the challenge of overcoming negative properties of soy derived fuels, e.g., the gelling of bioderived diesel (biodiesel) at higher temperatures than petroleum derived fuels. The composition of biodiesel (for a typical sample of soy biodiesel) is as given in table (1).
The present invention includes one or more of the following features: A very controlled C.P. depression can be achieved ranging from about 2 to about 26 C°. ‘Cloud point depression’ is the difference in C.P. of the product and the starting material. By controlling three process parameters the process can be optimized for maximum efficiency. Here efficiency of the process is in terms of the highest yield achieved for a given C.P. drop. Low processing cost, short processing time, easily scalable and robust process. A robust process is a process that is reproducible and repeatable with negligible variation in the results. Low energy consumption. Raw materials can be recycled and reused. The process is ecologically friendly with all raw materials, intermediates and final products and wastes being biodegradable. Applicable to the fractionation of SME, specifically soy derived biodiesel. Applicable to the fractionation of any mixture of vegetable oil derived free fatty acid methyl esters. It could be seen as altering the composition of SME for our benefit, than just separating the saturated and unsaturated fractions. It could be seen as altering the composition of any mixture of vegetable oil derived free fatty acid methyl esters to our benefit, rather than just separating the saturated and unsaturated fractions. It could be seen as an efficient method of obtaining an unsaturate rich and a saturate rich fraction from any mixture of vegetable oil derived free fatty acid methyl esters.
The novel method described herein selectively removes saturate fatty acid-rich fractions from SME. The amount of saturates removed and hence the C.P. of the resulting product can be easily controlled. We have achieved C.P. of about −10 C° at a yield of 78.38% and −26 C° at a yield of 66.39% by weight of the starting material. The novel process requires only moderate temperature variations (20-75 C°). The raw materials used may be recovered and reused making the process compatible with the environment. The processing time is short and runs into several minutes. This makes the process ideal for industrial scale processing of SME for improving its cold flow properties. In another embodiment our invention provides a very efficient and effective means of separation of unsaturated-rich and saturated-rich fractions from any mixture of vegetable oil derived free fatty acid methyl esters. In yet another embodiment our invention provides an efficient and effective means of altering the composition of any mixture of vegetable oil derived free fatty acid methyl esters. Specifically altering the ratio of saturates to unsaturates in a mixture. The present invention helps address: Controlled Cloud point depression of SME; controlled cloud point depression of any mixture of vegetable oil derived free fatty acid methyl esters; Efficient separation of unsaturated and saturated fractions from any mixture of vegetable oil derived free fatty acid methyl esters; altering the composition of any mixture of vegetable oil derived free fatty acid methyl esters; specifically altering the ratio of saturates to unsaturates in a mixture.
While the invention is susceptible to various modifications and alternative forms, a specific embodiment thereof has been shown by way of example and will herein be described in detail. It should be understood, however, that there is no intent to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
SME has proven to be an extender/additive/replacement for diesel fuel, heating oil and studies are on for its development as an aviation turbine fuel extender. A challenge to the utilization of biodiesel is its poor cold flow properties. The total saturate content of about 14-16% (wt/wt) causes the C.P. (cloud point) to be about 0 C° and pour point to be around −2 to −4 C°. This limits the use of SME at low temperatures. Various efforts have been made to reduce or depress the C.P. of SME by: 1) removal of saturated components, 2) use of cold flow additives, 3) use of branched chain alcohol esters, 4) combinations thereof.
The popular method for removal of saturate components is winterizing or cold filtering. Various studies have been conducted, however these methods have very low yields for any significant change in the C.P. Cold flow additives have been successful in lowering the P.P (Pour Point), however have little or no effect on the C.P. of SME. Usage of branched chain alcohol esters have poor yields during the esterification reaction, higher raw material cost with only a small depression in C.P.
We have developed a method for a controlled fractionation/separation of the saturated and unsaturated fractions of SME, using urea inclusion/urea complexation. By controlling three process parameters we achieve a C.P. depression ranging from −2 C° to −26 C°, by a controlled removal of the saturated fatty acid-rich fraction, with unsaturated fatty acid-rich fraction yields ranging from 98%-65% of the starting material, respectively. The three process parameters being 1) urea/SME/Alcohol (weight/weight/volume ratio), 2) cooling temperature, and 3) rate of cooling.
Depending upon the desired C.P. drop, we can choose a combination of urea/SME/Alcohol ratio, cooling temperature and rate of cooling. Various such combinations arc possible for the same C.P. drop. Those three parameters are selected to achieve an optimal fractionation of SME resulting in the highest yield for a given C.P. drop. The urea/SME ratio may range from 0 to 1 wt/wt. The alcohol/SME ratio may range from 4 to 8 vol/wt. Useful alcohols have from 1 to 5 carbon atoms, and blends thereof. Denatured ethanol is demonstrated to be effective.
The urea/SME/alcohol mixture is heated with constant stirring to about 65-75 C°, until a homogenous mixture is reached. The rate of heating of the mixture does not have an effect on the efficiency of the process. Here efficiency of the process is in terms of the yield of the product and the C.P. achieved.
The resulting mixture is then cooled at a preselected rate of cooling, with constant stirring, to a preselected temperature. The rate of cooling may vary from 1 to 15 C°/min. The final temperature to which the mixture is cooled may vary from 10 to 50 C°.
A solid phase comprised of urea inclusion compounds. This phase is rich in saturates. This maybe referred to as Solid phase; urea inclusion compound or raffinate elsewhere in the text.
A liquid phase comprised of mostly unsaturates, alcohol and some dissolved urea. The urea inclusion compounds formed are then removed from the liquid phase via filtration/centrifugation.
50-70% of the starting volume of alcohol is then recovered from the filtrate via evaporation at a temperature between 30-50 C° (under vacuum). The evaporation of ethanol is stopped just before the solubility limit of urea is reached. This prevents the urea coming out of solution and forming further complexes with the dissolved saturate rich fraction of SME. The remaining filtrate is then washed with warm acidic water (60-70 C°, pH 3-4) to remove all the urea and remaining alcohol. This can be done in steps, washing the filtrate with an equal volume of warm, acidified water in each step, or in a continuously manner using water 3-4 four times the volume of filtrate. Unsaturate rich SME fraction with the desired C.P. is then achieved. The saturate rich fraction can also be obtained from the raffinate by dissolving and washing with warn acidified water (60-70 C°, pH 3-4). This fraction can be used as additives to heating oil and other heavy oils where C.P. is not a critical property. Urea can be recovered by evaporating the water.
The invention/technique is illustrated by the following examples:
The starting SME had the composition and properties according to Table 2: Table 2:
24.057 g of soy methyl esters and 10.077 g of urea were added to 160 mL of EtOH and the mixture was heated to 67 C°, with constant stirring. A homogenos mixture was obtained with all the urea dissolving at this temperature. The mixture was then cooled at a rate of 1.19 C°/min to a final temperature of 20 C°. The urea inclusions compounds formed were then separated by filtration. The filtrate was then heated to 30 C° and 70% of the starting volume of EtOH was recovered via evaporation under vacuum. The remaining filtrate was then washed with equal volume of water (60 C°, pH 3). This step was repeated twice. 18.83 g of fractionated SME (78.38% by wt of the starting SME) was recovered with the composition and properties according to Table 3. Recovered EtOH is available for re-use in the process.
The starting SME had the composition and properties according to Table 2:
24.053 g of SME and 18.045 g of urea were added to 160 mL of EtOH and the mixture was heated to 73 C°, with constant stirring. A homogenous mixture was obtained with all the urea dissolving at this temperature. The mixture was then cooled at a rate of 1.19 C°/min to a final temperature of 20 C°. The urea inclusions compounds formed were then separated by filtration. The filtrate was then heated to 30 C° and 52% of the starting volume of EtOH was recovered via evaporation under vacuum. The filtrate was then washed with equal volume of water (60 C°, pH 3). This step was repeated twice. 15.97 g of fractionated SME (66.39% by wt of the starting SME) was recovered with the composition and properties according to Table 4.
The starting SME had the composition and properties according to Table 2:
24.056 g of SME and 16.041 g of urea were added to 160 mL of EtOH and the mixture was heated to 72 C°, with constant stirring. A homogenous mixture was obtained with all the urea dissolving at this temperature. The mixture was then cooled at a rate of 1.32 C°/min to a final temperature of 30 C°. The urea inclusions compounds formed were then separated by filtration. The filtrate was then heated to 30 C° and 63% of the starting volume of EtOH was recovered via evaporation under vacuum. The filtrate was then washed with equal volume of water (60 C°, pH 3). This step was repeated twice. 18.25 g of fractionated SME (75.86% by wt of the starting SME) was recovered with the composition and properties according to Table 5.
The starting SME had the composition and properties in Table 2:
24.089 g of SME and 16.044 g of urea were added to 160 ml of EtOH and the mixture was heated to 72 C°, with constant stirring. A homogenous mixture was obtained with all the urea dissolving at this temperature. The mixture was the cooled at a rate of 10.71 C°/min to a final temperature of 20 C°. The urea inclusions compounds formed were then separated by filtration. The filtrate was then heated to 30 C° and 63% of the starting volume of EtOH was recovered via evaporation under vacuum. The filtrate was then washed with equal volume of water (60 C°, pH 3). This step was repeated twice. 15.64 g of fractionated SME (64.92% by wt of the starting SME) was recovered with the composition and properties in Table 6.
Fuel for turbine engines is specified by ASTM standard D-1655. Plant sourced oils have limited penetration in to the market for turbine fuel.
A commercially sourced soybean oil derived fatty acid methyl ester the properties of which are described in Table 2 was fractionated as described herein. The as obtained fraction analysis and the fraction analysis after processing appears in Table 8. The fractionated SME of Examples 5-7 was then blended with the Commercial Jet A fuel to yield the properties according to Table 7.
The fractionated soy methyl ester was blended with Jet A fuel in the ratios indicated in Table 7 yielded the properties noted. The blended fuel has demonstrates that the requirements of ASTM D-1655 are attainable with blends including SME.
Combustion studies of SME blends with commercial Jet A show non-critical deviation from the combustion of commercial Jet A fuel. An Allison stationary 250 turbine having a relatively low compression ration of 6.2:1 was used for the combustion study.
Controlled emissions for Jet A and SME blends are shown in
While the invention has been illustrated and described in detail in the foregoing ion, such illustration and description is to be considered as exemplary and not restrictive ter, it being understood that only the preferred embodiments have been shown and d and that all changes and modifications that come within the spirit of the invention are to be protected.
| Number | Date | Country | |
|---|---|---|---|
| 60547992 | Feb 2004 | US |
