JP2011512419A - Fuel composition - Google Patents

Abstract

Fuel composition comprising a C ₂ -C ₆ esters of lower alkyl monool and one or more long chain fatty acids. In general, C, H, O atoms constitute 99.99% by weight of the composition. The composition can be essentially free of sulfur and / or nitrogen atoms. The composition can be provided by adjusting the pH of a liquid comprising at least one C ₂ -C ₆ ester of one or more long chain fatty acids to less than 7.0. C ₂ -C ₆ esters can provide by transesterification using the triglyceride-containing _composition, a C 2 -C ₆ mono-ol. The monool can be present in a stoichiometric excess.

Description

  Diesel engines continue to find wide application in trucks, ships, trains and the like. Commercially acceptable diesel fuel must perform in a range of climatic conditions and therefore must be able to be used at temperatures up to 0 ° C, preferably at least -10 ° C.

  Diesel engine exhaust often contains particulates, CO, and various nitrogen oxide (NOx) species. Over the past few years, many attempts to address the environmental problems associated with exhaust emissions from diesel engines have focused on lower alcohols such as methanol and ethanol. A blend of 15% (volume ratio) ethanol and 85% (volume ratio) diesel oil has been found to improve combustion byproducts released in the engine without requiring modification of the diesel engine. This is generally thought to be due to the increased oxygen content of the fuel. In recent years, the amount of ethanol is sometimes increased to 20% (volume ratio). However, lower alcohols are typically not miscible with diesel oil and tend to separate over time. Thus, the components are often stored separately and mixed just prior to use.

  The type of fuel blend described is often referred to as “E-diesel” (or some similar variations). E-diesel typically produces less unacceptable combustion by-products than net diesel oil. However, when burned, it produces less energy and still utilizes diesel oil from at least 80% of its volume of petroleum. Concerns about sustainability and resource capacity for fossil fuels have increased significantly over the past decade. In response, increasing interest in fuels prepared from sources other than petroleum has increased significantly over the past decade or so.

  Much of this interest has focused on so-called biofuels. It is the transesterification product of any of a variety of animal fats and vegetable oils. The main components of oil and fat are fatty acid triglycerides, that is, molecules in which three long-chain fatty acids are ester-bonded to a glycerin group. When an oil or fat is exposed to an alcohol (typically methanol) under appropriate catalytic conditions, the fatty acid dissociates from the glycerin group and reacts with the alcohol to form a fatty acid ester. The transesterification reaction significantly reduces the viscosity of the oil.

  Triglyceride transesterification reactions have been highly studied; for more detailed information on the production and properties of such biofuels, interested readers can refer to, for example, “burning of fat and vegetable oils provided to diesel engines” ( (Combination of Fat and Vetable Oil Delivered Fuels in Diesel Engines) Prog. Energy Combust. Sci. , Vol. See any of the overviews such as pages 24, 125-64 (1998, Elsevier).

  The biofuel can be used as is, but more commonly a small amount is mixed into petroleum-derived diesel oil (hereinafter referred to as “Petrodiesel”). A blend of biofuel and petrodiesel is often referred to as B-diesel, or more commonly indicated by the percentage of petrodiesel replaced by biodiesel following the symbol B (for example, B20 diesel is 80% Of petrodiesel and 20% biodiesel).

  Some have attempted to combine alcohol and biofuel in one composition; see, eg, US Pat. No. 6,129,773, US Patent Application Publication No. 2003/0126790 A1.

  Fuel compositions containing components derived solely from renewable starting materials appear to continue to be of great interest. Ideally, such biofuel compositions can be used in essentially the same climatic conditions as petrodiesel and have better emission characteristics than petrodiesel. Further, such compositions preferably generate approximately the same energy as the same volume of petrodiesel, while having similar or better engine wear characteristics.

In one embodiment, the fuel composition comprising a C ₂ -C ₆ ester of ethanol and one or more long chain fatty acids is provided. The composition generally comprises at least about 2.5% (by volume) of a lower alkyl monool, such as ethanol, typically from about 5 to about 10% (by volume), and one of the complementary amounts Or comprises a plurality of long chain fatty acid esters; all other ingredients are typically present only in trace amounts.

  In some embodiments, at least 99.99% (by weight) or 99.999% (by weight) of the composition is composed solely of C, H, and O atoms; in these and other embodiments, the composition Is essentially free of at least one of sulfur and nitrogen atoms, preferably both.

  The composition typically comprises at least about 0.2% (by volume), generally at least about 0.25% (by volume), and optionally at least about 0.3% (by volume) water. In some embodiments, the fuel composition can include at least about 0.5% (by volume) water. Although water in the fuel composition is typically considered to be avoided as much as possible, the presence within about 1% (volume ratio) is particularly detrimental to the efficiency of the fuel composition of the present invention. It has not been proven that there is.

  In some embodiments, the fuel composition can have an acidic pH, for example 4.5 at the lowest, but more typically from about 6.0 to about 6.8.

The composition typically has a kinematic viscosity of from about 3.5 to about 4.0 mm ² / s (ie cSt), generally about 3.7 ± 0.2 mm ² / s. Even without the flow improver additive, the composition can have a cloud point of at least about −5 ° C. and a pour point of at least about −15 ° C.

In another aspect, a method for synthesizing and purifying a fuel composition is provided. The method of the present invention includes providing a liquid comprising at least one C ₂ -C ₆ ester of one or more long chain fatty acids and adjusting the pH of the liquid to less than 7.0. The _C 2 -C _{6 ester,} be provided by transesterification of triglyceride-containing compositions using C 2 -C ₆ mono-ol. In such cases, pH adjustment also results in the separation of salts and glycerin-related byproducts (eg, glycerin) from the liquid phase. This results in an unrefined fuel composition. Thereafter, the unrefined fuel composition removes particulates having an average diameter greater than about 1 μm, and the concentration of Group 1 metal ions is less than about 50 ppm (parts per million), preferably more Processed to ensure that it is 1 from 5 to 10.

Transesterification process is typically carried out in the presence of one or more C ₂ -C ₆ excess of alcohol stoichiometry. The alcohol or alcohols are typically about 25 to about 200% (by volume) excess, preferably about 50 to about 150% excess, more preferably about 70 to about 130% excess, most preferably about 80 to Present in excess of about 120%.

  The unrefined liquid fuel composition and the liquid fuel composition that is ultimately obtained from the refining process are typically at least initially typically from about 4.5 to about 6.8, preferably from about 5.0 to about 6 .75, more preferably from about 5.5 to about 6.7, and most preferably from about 6.0 to about 6.65. Purifying the fuel composition under slightly acidic conditions provides the advantage of storage stability.

  In certain embodiments, pH adjustment is performed by adding a strong acid to the liquid. In some of these embodiments, the acid is a halogenated acid (eg, HCl). The salt removed from the liquid is KX, where X is a halogen atom, for example Cl.

  In some embodiments, processing of the unrefined fuel is performed by passing the unrefined fuel through a series of filters, and optionally the pore sizes of these filters are progressively smaller.

The process can provide a fuel composition having a kinematic viscosity from about 3.5 to about 4.0 mm ² / s, most commonly a kinematic viscosity of about 3.8 mm ² / s or less.

  The process of the present invention can also provide a fuel composition that is fluid even in the absence of fluidity improving additives. Specifically, the composition can have a cloud point of at least −5 ° C. and a pour point of at least −15 ° C. The cetane number of the refined fuel composition is typically greater than about 45 and can be significantly greater (eg, 5-15%).

  Advantageously, all the steps of the process of the invention can be carried out without the use of an external heat source, i. Furthermore, the process of the present invention can be carried out without the addition of significant amounts of water so that wastewater (which is typically very corrosive) need not be collected and treated.

In another aspect, a method for powering a vehicle is provided. The method of the present invention includes introducing a fuel containing the above fuel composition into a diesel engine, allowing the engine to burn the fuel. Advantageously, the aforementioned fuel composition can simultaneously reduce opacity, CO, SO ₂ and NOx in the exhaust as compared to the exhaust of the same engine that burns Petrodiesel. At the same time, the amount of O _{2 in} the same exhaust is increased compared to when Petrodiesel is combusted. In many cases, the aforementioned composition significantly reduces the amount of carbonaceous deposits (often referred to as “coking”) on the metal parts of the engine, and in some cases eliminates it. While scrubbing capacity and lower exhaust temperatures are perhaps exceptions, other characteristics will be more apparent in a two-cycle diesel engine than in a four-cycle diesel engine.

Other aspects of the invention are described in the more detailed description below.
Detailed description

  A method for producing a fuel composition, more specifically a process comprising synthesizing and purifying a fuel composition, is first described.

  Like other biofuel manufacturing steps, the synthetic part of the process involves a transesterification reaction. However, certain aspects of the reaction are different from those known in biofuel production.

  Almost all triglycerides can transesterify with alcohol. For example, as described above, in some cases, filtered waste oil from fast food restaurants is used as an inexpensive reactant. However, highly pure vegetable oils, more preferably food materials such as corn oil, linseed oil, peanut oil and soybean oil are preferably used in the process of the present invention.

（いくつかの材料は分析されない構成物質脂肪酸を含んでいたので、表Ｉｂの中の数はすべての場合において合計１００％にはならない。） For the convenience of the reader, the following table shows the approximate percentages of saturated and unsaturated fatty acid components in various fats and oils. The first is from page 130 of the above-mentioned work of Graboski et al., The second is the performance and durability test of diesel engines using ethyl and methyl ester fuels by Peter Peterson et al. (Performance and Durability Testing of Diesel Engineers Using Ethyl and Methyl Estel Fuels), Nat'l Biodiesel Bd. Report for 1995, from Appendix A received on February 27, 1996. The former provides data on raw materials (that is, those that are not transesterified). The latter, on the other hand, provides data on esterified fatty acids in biofuels made from such materials.

(Some materials contained constituent fatty acids that were not analyzed, so the numbers in Table Ib do not add up to 100% in all cases.)

  A preferred starting material is a food grade vegetable oil selected from the previous list. In particular, purified, bleached and deodorized (RBD) are preferred. Such materials are available from various commercial sources such as, for example, ConAgra, Bungee, ADM and the like. Although the description herein is based on RBD soybean oil, in view of the benefits over other oils found with this material and its compositions, those skilled in the art will be able to provide long chain fatty acids that can provide similar benefits. Other sources can be identified and / or effects in different end use conditions can be identified.

  One or more fatty acid sources can be provided in or to the reaction vessel. Although the prior art teaches that almost any type of container can be used, the preparation of a high quality biodiesel fuel composition is facilitated by the use of containers made from clean, essentially non-reactive materials. Become. Materials such as steel, stainless steel, glass lining metal and the like are preferably used.

The other reactant in the transesterification reaction is an alcohol. Most biofuels use methanol as a reactant. In fact, if the producer wants the product to be certified as a biodiesel fuel, the European Biodiesel Commission orders the use of methanol; see eg EN 14214. However, higher alcohols, especially if one or more C ₂ -C ₆ alcohol is used, was found inherent advantages. Non-limiting examples of these advantages include improved miscibility with Petrodiesel and good low temperature performance as illustrated by cloud point, cold pour point.

The alcohols used are preferably each aliphatic and more preferably have the general formula C _n H _{2n + 1} 0H. In the formula, n is 2 or more and 6 or less (2 ≦ n ≦ 6). As shown by the formula, the use of monools is preferred to avoid the formation of longer chain diesters. Preferred alcohols include ethanol, 1-propanol, 2-propanol and 1-butanol, and particularly preferred is absolute ethanol (eg, ethanol modified with gasoline).

  If the emission characteristics of the resulting fuel are important, the alcohol is preferably free of heteroatoms that can be involved in the formation of inappropriate species; non-limiting examples of such heteroatoms are N, S and P Can be given.

  The reaction between one or more alcohols and one or more triglycerides is catalyzed by both an acid and a base, and a strong base is more commonly used. Typically, no more than about 1% by weight of catalyst is required based on the triglyceride starting material.

  Conveniently, the catalyst may be provided in some or all of one or more alcohols. This can be done by dissolving a strong alkali, such as KOH, in one or more alcohols before feeding the alcohol to the reaction vessel. Conveniently, this can be done in a relatively short time (less than 1 hour) by simply mixing at ambient or slightly elevated temperatures. If desired, the catalyst solution can be added in stages. That is, aliquots can be added sequentially and then mixed or stirred.

Preferably excess alcohol is introduced into the reaction vessel. As described above, the fuel composition includes both one or more C ₂ -C ₆ esters of long chain fatty acids and one or more C ₂ -C ₆ alcohols. Rather than supplying a stoichiometric amount of alcohol to the reaction vessel and then mixing the resulting transesterification product with additional alcohol, one or more alcohol components are introduced during the transesterification step. This may provide processing and performance advantages. In practice, a significant excess of alcohol can be added to the reaction vessel; the amount is typically about 25 to about 200%, preferably about 50 to about 150%, more preferably about 70 to about 130%. Even more preferably from about 80 to about 120%, most preferably at least about 100% excess (all by volume).

  Despite the earlier statement that it is advantageous to use an excess of alcohol during the production and purification steps, at least some benefit can be obtained by addition of alcohol during or after purification.

  To some extent, the stoichiometric excess of alcohol can vary somewhat so that a fuel composition with slightly different properties is produced. In this way, a seasonal blend of fuels can be created. For example, in the cold season, the alcohol excess can be increased to provide a fuel composition having a viscosity less than a similar composition intended for summer use.

  While not to be recognized as a limitation, the process of the present invention has been described as including adding a basic alcohol solution to the oil. However, by introducing the alcohol solution near the bottom of the tank and providing a partition above it, several reaction advantages can be obtained. This is especially the case when the reaction mixture is not stirred and when the transesterification reaction is allowed to proceed at or near ambient temperature. When known stirring techniques (eg circulation pumps) are used, the transesterification reaction typically takes several hours to complete at 20-25 ° C. This is not absolutely necessary, but the transesterification reaction can be promoted by relatively mild heating.

  The second product of the transesterification reaction is glycerin and other glycerin byproducts. Depending on the identity, nature, and purity of the reactants, the glycerin in the reaction vessel is separated by itself, or partially, or only minimally. For example, when high purity reactants are used, after stirring is stopped, glycerin (or a derivative thereof) typically separates from the alkyl ester / ethanol phase in a few hours (eg, 4-12 hours). However, if less purified starting materials are used, additional alcohol addition (eg, up to about 20% additional alcohol) and / or additional time may be required to achieve the desired level of separation. It was. The alcohol added for separation purposes need not be the same as the alcohol used in the reaction. In fact, if desired, methanol can be used for this purpose.

  The glycerin phase is heavier than the alkyl ester / alcohol phase and separates at the bottom of the reaction vessel. If the reaction vessel has an outlet at or near its bottom, the glycerin layer can be drained from the reaction vessel. Typically, the glycerin phase comprises about 10 to about 20% of the triglyceride reactant. Based on the excess of alcohol used during the transesterification reaction, it is estimated that the glycerin layer contains a non-trace amount of alcohol. Processing and / or disposal techniques for glycerin are known.

Assuming that the material used as the basic catalyst contains a Group 1 or Group 2 metal element (eg, KOH or Ca (OH) ₂ ), the majority of Group 1 or Group 2 metal ions enter the glycerin phase. Divided. By recovering the glycerin phase, it is thereby possible to recover most of the Group 1 or Group 2 metal ions that are preferably present in the reaction vessel. The remaining alkyl ester / alcohol phase typically contains such ions on the order of 500 to 1000 ppm, more typically on the order of 600 to 800 ppm.

The alkyl ester / alcohol mixture is further transferred within the reaction vessel, more typically to one or more additional vessels, and processed for further purification. At this point, the mixture typically has a kinematic viscosity of about 6.2 to about 6.8 mm ² / s.

  Organizations such as the National Biodiesel Board (NBB) have repeatedly washed unpurified fuel (which assumes stoichiometric amounts of triglycerides and methanol and is highly corrosive) with water. Suggest a technique. This repeated cleaning uses large amounts of other natural resources (ie water) and results in large amounts of moderate to very corrosive wastewater that must be treated before and / or after disposal.

  Conversely, techniques that do not use water themselves are desirable in the process of the present invention. For example, an unpurified fuel composition is passed through a cationic ion exchange resin or passed through the resin to replace a Group 1 or Group II metal ion with a hydrogen atom. Such resins are widely known and are available from various commercial sources such as Rohm, Haas (Philadelphia, Pennsylvania).

  Alternatively, a relatively small amount of strong acid can be used to neutralize the alkyl ester / alcohol mixture. Halogen containing strong acids (eg concentrated HCl) are preferred over other types of strong acids containing heteroatoms such as sulfuric acid and nitric acid. One skilled in the art can perform the stoichiometric calculation required to determine the amount of a given acid needed to neutralize a given unrefined fuel composition. As a non-limiting example, 1 liter of concentrated hydrochloric acid can process over 500 liters of unrefined fuel composition.

Such purification techniques result in the removal of Group 1 or Group 2 metal ions. When an acid is added to the mixture, the ions are recovered as a salt with the majority of all glycerin-type byproducts that have not previously phase separated. The latter is evidenced by a fairly large reduction in kinematic viscosity. As previously mentioned, unrefined fuel compositions typically have a kinematic viscosity at 40 ° C. of about 6.5 mm ² / s; conversely, in the same composition that has undergone oxidative refining Typically having a kinematic viscosity at 40 ° C. of about 4.0 to about 5.5 mm ² / s. This is believed to be somewhat better than what can be obtained by simple water washing and / or treatment with an ion exchange resin. For example, in Peterson et al., Various ethyl ester biofuels have kinematic viscosities from 4.5 mm ² / s (soybean oil) to 6.2 mm ² / s (rapeseed oil).

  Techniques that claim that the refined fuel is essentially neutral (pH = 7.0) are generally accepted, but the treated fuel composition, regardless of which refinement technique is used (Ie, the purified alkyl ester / alcohol mixture) is preferably made very slightly acidic. At this point in the purification process, the alkyl ester / alcohol mixture can be said to have a pH of at least 4.0 to 4.5, typically between about 4.5 and about 6.9; more generally The pH of the mixture is in one or more of the following ranges: from about 5.0 to about 6.8, from about 5.5 to about 6.75, from about 5.75 to about 6.7, from about 5.9. About 6.7, about 6.0 to about 6.75, about 6.0 to about 6.7, about 6.1 to about 6.6, about 6.1 to about 6.7, and about 6.4 ± 0.2.

  For fuel compositions, particularly biofuels, acid numbers are generally reported. This is a measure of the free acid, ie, unesterified fatty acids, given in mg of KOH needed to neutralize these fatty acids. If a strong protic acid is utilized in refining the fuel composition of the present invention, this acid number is no longer considered meaningful. For at least this reason, conventional pH meters are used to obtain pH measurements, which are used here.

  By providing a fuel composition that is slightly acidic, an effect on storage and handling properties has been seen without detrimental effects on performance. In particular, fuel compositions refined to be essentially neutral at this point showed flocculation or precipitation upon prolonged storage and / or especially when exposed to air. In contrast, the trend was not seen with fuel compositions having a slightly acidic pH.

  At this point in the refining process, the fuel composition contains primarily alcohol and alkyl esters of long chain fatty acids; most other materials are present essentially in trace amounts. However, the fuel composition is generally about 0.2 to about 0.9% (volume ratio), usually about 0.25 to about 0.75% (volume ratio), sometimes about 0.3 to about 0.00. Contains 6% (volume ratio) water. As discussed in more detail below, even when the fuel composition is filtered, the amount of entrained or dispersed water is not significantly reduced; however, the presence of such water is not It is not known to have a significant adverse effect on the combustion of, and may further provide certain advantages (eg, reduced combustion temperature).

  Further, at this stage of the purification process, the amount of Group 1 and Group 2 metal ions is typically about 50 ppm or less, preferably about 25 ppm or less, more preferably about 10 ppm or less, even more preferably about 5 ppm or less, Most preferably, it is reduced to about 4 ppm or less.

The fuel composition can include an alcohol within about 50% (volume ratio) of the total volume. Fuel compositions generally contain from about 2 to about 40% (by volume) alcohol, more typically from about 3 to about 30% (by volume), and most typically from about 4 to 20% (by volume) alcohol. Can be included. When high purity reactants are used as described above, the refined fuel composition produced by the process of the present invention is typically about 5 to about 15% (volume ratio), generally about 5 From about 5 to about 10% (by volume), most commonly from about 6 to about 8% (by volume) alcohol; preferably the alcohol is one or more C ₂ such as ethanol and / or 1-butanol. -C is a ₄ mono-ol.

  In this respect, several options are available. For example, the purified mixture can be used as is, or can be used after the addition and thorough mixing of one or more conditioners, stabilizers or other additives (eg, kerosene). However, further refined fuel compositions, optionally including additives of the type described above, can obtain certain additional advantages.

  An additional purification technique that has been found to be advantageous in certain situations is filtration. Specifically, the fuel composition can remove suspended impurities with one or more filters, optionally with a plurality of filters that are successively reduced in hole diameter. Commercial filtration devices are available from various suppliers such as Donaldson (Minneapolis, Minnesota), Central Illinois Manufacturing (Bement, Illinois), Harvard (Evansville, Wisconsin), Wix Filtration. Available from Products (Gastonia, North Carolina). By using a pump to pressurize the system from about 130 to about 140 kPa, a processing rate on the order of about 550 to 700 mL / s can be provided.

It has not been known to perform such filtration on unrefined fuel compositions, at least in a consistent manner, providing significant advantages. However, when the filtration is performed for the above fuel composition which has already been treated by oxidation techniques, kinematic viscosity of about 4.2 mm ² / s or less in order at 40 ° C., a kinematic than about 4.1 mm ² / s Viscosity, kinematic viscosity of about 4.0 mm ² / s or less, kinematic viscosity of about 3.9 mm ² / s or less, kinematic viscosity of about 3.8 mm ² / s or less, further kinematic viscosity of about 3.7 mm ² / s or less Viscosity can be obtained. This technology can provide soybean oil ethyl ester / ethanol fuel compositions at 40 ° C. on the order of about 3.6 mm ² / s, on the order of about 3.5 mm ² / s, or lower kinematic viscosities. It is believed that. These viscosity values are in contrast to those reported for ethyl ester biofuels in the prior art; for example, the previously mentioned Peterson et al. Data and Graboski et al. Data (from 4.4 5.9 mm ² / s). Furthermore, the presence of free alcohol in the fuel composition can account for approximately half or less of the viscosity reduction found in the fuel composition of the present invention. The other half of this reduction is not fully understood, but the acidification step produces one or unwanted by-products that are not affected by being removed by further purification steps such as filtration steps. It is thought.

Thus, an acidified and filtered fuel composition can have a kinematic viscosity that is on the order of about 40% less than the unrefined fuel before it is refined. Since petrodiesel is generally expected to have a kinematic viscosity of 4.1 mm ² / s or less when measured at 40 ° C. according to ASTM D975, providing a biofuel with similar properties is It can be advantageous both in terms of commercial acceptability and performance in use. One of ordinary skill in the art will appreciate the desirability of a biofuel composition having storage and performance characteristics that are as similar as possible to petrol diesel everywhere. For example, published reports, including the aforementioned Peterson et al. Report, show that fuel injector coking is directly related to fuel viscosity. Caulking was further speculated to be due to impurities in the biofuel; see, for example, Peterson et al. These two theories may be related: purification that results in fewer impurities may result in a reduction in viscosity as well.

  The above purification process is believed to provide significant advantages over processes commonly used in the production of biodiesel fuel. For example, the process of the present invention does not require the use of much water to wash out Group 1 ions from an unrefined fuel composition; this reduces the amount of water that must be used and treated prior to disposal. cut back. Furthermore, because excess alcohol in the refined fuel composition is desirable, the process of the present invention does not require the use of time and energy intensive distillation techniques. Thus, in addition to using essentially only natural starting materials, the process of the present invention requires very little energy input to make and refine the fuel composition.

  Once fully purified, the fuel composition can be stored without the need for significant processing or vigilance. As noted above, better storage and handling performance can be achieved by refining a slightly acidic fuel composition. However, once purification is complete, it has not been determined whether the fuel composition must be maintained in acidic form. In other words, once the refining process is complete, the refined fuel composition is such that the fuel composition has an essentially neutral pH prior to use without adversely affecting the viscosity and storage stability of the fuel composition. It may be possible to adjust the pH of the object upward.

  Advantageously, the process of the present invention has a cloud point of at least −2 ° C., −3 ° C., −4 ° C., −5 ° C., −6 ° C., −7 ° C., or even lower when measured according to ASTM D2500, and A fuel composition is provided having a pour point of at least -10 ° C, -12.5 ° C, -15 ° C, -17.5 ° C, -20 ° C or even lower when measured according to ASTM D97. For example, a fuel composition made from ethanol and RBD soybean oil by the process described above and treated with a small amount of diesel conditioner would be in a useful state even after standing overnight at ambient temperatures down to at least −20 ° C. Profitable biodiesel fuel is not expected to achieve this type of low temperature performance with the addition of significant amounts of conditioners and other additives. For example, Peterson et al. Report that the fatty acid ethyl ester has a pour point from −10 ° C. (ripe rapeseed oil ethyl ester) to 12 ° C. (beef tallow ethyl ester). For a more direct comparison, the same report shows that the ethyl ester of soybean oil has a pour point of −3 ° C .; therefore, the process of the present invention is more than that of a standard ethyl ester biofuel. It would be possible to provide a fuel composition having a pour point that is at least 5 ° C. to 20 ° C. lower.

  The fully refined fuel composition can be used as is or diluted with an appropriate amount of petrodiesel depending on the end use. For example, in some fueling locations, a 50:50 biofuel and petrodiesel mixture can be made and then used as a masterbatch for further dilution. To date, no significant miscibility issues have been reported even for so-called masterbatch blends.

As noted above, the fuel composition of the present invention generally comprises a lower alkyl monool (eg, ethanol) and one or more long chain fatty acid C ₂ -C ₆ esters. The composition is generally from about 5 to about 10% of one or more C ₂ -C ₄ alcohols, preferably ethanol, and the remaining one or more long chain fatty acid ester in the amount; all other Ingredients are typically present below the trace amount. In some embodiments, at least 99.99% or 99.999% by weight of the composition can be comprised of C, H, and O atoms; in these and other embodiments, the composition has at least sulfur and nitrogen atoms. One, preferably both can be substantially free.

  Compositions generally contain water, typically in an amount of about 0.2 to about 0.5% (volume ratio), but may contain up to 0.8% (volume ratio) or more. In some situations, it is possible.

For reasons already discussed, the fuel composition preferably has a slightly acidic pH (at least during refining) and a kinematic viscosity at 40 ° C. of about 3.7 ± 0.2 mm ² / s. Even in the absence of flow improvers, the compositions of the present invention can have a cloud point of at least about −5 ° C. and a pour point of at least −15 ° C. Each of these properties is achieved in embodiments in one or several combinations.

  This type of biofuel composition can be used undiluted and under some circumstances can provide a significant effect on emissions against undiluted petrodiesel or blends of petrodiesel and biofuel.

For example, a fuel composition comprising ethanol and ethyl ester transesterification product of RBD soybean oil is a two-cycle, V-16, root blown, short rail line using an engine without a turbocharger. Tested on a locomotive (EMD model 16-645BC). Each cylinder had a displacement of about 10.5 liters (645 cubic inches), for a total displacement of approximately 170 liters. Prior to testing, the locomotive was supplied with about 280 liters (75 gallons) of pure biofuel composition and warmed up, thereby draining all residual petrodiesel from the engine.
Thereafter, approximately 190 liters (50 gallons) of each of the following fuels were tested sequentially:
Pure biofuel, 50:50 mixture of biofuel composition and railway off-road # 2 Petrodiesel, and pure Petrodiesel. The exhaust test was performed on an engine under steady state load created by connecting a DC generator operated on a locomotive diesel engine to a loading grid designed to convert power to heat.

  Percent smoke opacity was measured using a Wager® 7500 (Robert H. Wager Company; Rural Hall, North Carolina) clamped on a 5 cm (2 inch) sampling elbow tube placed inside the locomotive exhaust. Nina) measured continuously using a smoke meter.

Emissions were measured using a testo® 350XL portable gas analyzer (Test Corp .; Flanders NJ). Instrument was set to measure exhaust gas oxygen, CO, SO _2, total hydrocarbons, NO, the NO ₂ and combined NOx levels. (Total hydrocarbon data was not collected due to sampling issues.) The analyzer was equipped with a Model 450 control unit and an attached sampling probe. The gas analyzer probe was maintained at a fixed sampling position by a bracket that held the probe approximately 2 inches (5 cm) in the center of the exhaust pipe.

  Data collection began after a stable opacity reading was obtained after each test fuel introduction. After this initial recording, readings were continuously charted at 1-2 minute intervals.

The test results summarized below in Table 2 below are the average of five of these values.

The data from Table 2 shows a number of interesting properties. For example, although the results are superior to those reported previously (eg, Peterson report article), the fuel composition of the present invention was synthesized and purified in a manner that avoided the introduction of sulfur atoms, so # A 100% reduction over 2 diesel oil (Petrodiesel) could be explained. Furthermore, since the fuel composition of the present invention results in a lower exhaust temperature, the reduction of NOx emissions could be easily explained (because NOx formation is known to increase at higher combustion temperatures. is there). Furthermore, the higher oxygen content of the fuel composition of the present invention simultaneously increased the O ₂ content, greatly reducing the CO concentration in the exhaust (ie, 75% or more).

  The previous results show that off-road # 2 Petrodiesel (one that meets the current EPA regulations and the other meets the more stringent California regulations) and B20 diesel, that is, Petrodiesel and methyl ester derivatives of soybean oil, 80 : Symmetrical with published results for comparison with 20 mixtures. S. May 2004 G. See Fritz et al., “Evaluation of Biodiesel Fuel in an EMD GP38-2 Locomotive, National Renewable Energy Laboratory Subconductor Report” by the US Department of Commerce. Available).

The study was conducted on a load-switcher locomotive equipped with an EMD 16-645-E diesel engine characterized in Table 3 below.

The results of this combustion exhaust experiment are shown in Tables 4a and 4b below. Where EPA-1 through EPA-3 are three tests performed on diesel fuels that meet US Environmental Protection Agency standards for locomotive exhaust (see 40CFR §92.113); Cal -1 to Cal3 are three tests performed on a 50:50 mixture of two commercially available fuels that meet California Air Resources Board standards; B20-1 to B20-3 are G- Three tests performed on a 20:80 mixture of 3000® biofuel (Griffin Industry, Cold Spring, KY) and the fuel used in EPA-1 through EPA-3; C20 -1 to C20-3 are 20: 8 of G-3000® biofuel and the fuel used in Cal-1 to Cal-3 There three tests were performed on mixtures; CBSFC the Association of American Railroads - a correction brake specific fuel consumption; c. o. v. Is the coefficient of variation of the three tests.

  These data show that the B20 diesel mixture shows increased emissions of NOx in both the line-haul duty cycle and the switch duty cycle, and further in the line-hole duty cycle. Indicates increased exhaust opacity (indicated by particulate emissions). (In terms of particulate matter, a 2004 study concluded that the type of fuel used had little effect on the amount of particulates, because such emissions in a two-cycle diesel engine were a lubricant component. The tests summarized in Table 2 appear to show that this is not necessarily true for the fuel composition of the present invention.

Each of the exhaust characteristics of the fuel composition of the present invention is highly desirable, both individually and in combination.
This is particularly true considering the fact that the locomotive exhaust is from a survey of environmental engines such as EPA. Two-cycle diesel engines make up the majority of engines used in North American railways, and off-road # 2 Petro Diesel is a relatively polluted fuel (ie, its combustion is a large amount of particulate, SO _2, since generally considered NOx species is such a generated), it is highly desirable to be able to utilize alternative fuel that can assist in these engines to meet more stringent emission standards.

  The fuel composition of the present invention has been found to have a significant effect on emissions when used in a two-cycle diesel engine, but is more commonly used such as long-haul trucks 4 It has not yet been proven in a cycle diesel engine; more precisely, the initial schematic study shows that the improvement is as dramatic as that seen in a two-cycle diesel engine can not see. The difference in pressure and temperature in each combustion chamber is believed to be due to one or more of a variety of factors, including more efficient cooling of the combustion chamber in a four cycle engine.

各燃料についてのエンジン効率は、式ηｅ＝１／（ＢＦＳＣ×ＬＨＶ）を使用して計算された。ηｅは与えられた時間インターバルにおいてのエンジン効率であり、ＢＦＳＣはその時間インターバルにおける正味燃料消費率である。また、ＬＨＶは燃料の低位発熱量である。エンジンが各燃料タイプで１５分間、エンジンを運転する前に７１℃（１６０度Ｆ）にできるだけ接近して暖められた後、冷却液温度上昇が決定された。 However, the above general study has shown other advantages in the use of the fuel composition of the present invention. For example, a 4-cycle Cummins® Turbo, Intercooled Diesel Engine (set to drive at 2200 rpm, which is almost equivalent to a freight truck traveling at a constant speed of 24.6 m / s (ie 55 mph) # 2 Petrodiesel (A), commercially available, and three alternative fuels—B20 biofuel (B), ie Petrodiesel and soybean oil An 80:20 mixture of the methyl ester derivatives of, a filtered waste vegetable oil (C), and a fuel composition (D) according to the present invention were tested. The engine efficiency data listed in Table 5 below was obtained:

The engine efficiency for each fuel was calculated using the formula ηe = 1 / (BFSC × LHV). ηe is the engine efficiency for a given time interval and BFSC is the net fuel consumption rate for that time interval. LHV is the lower heating value of the fuel. The coolant temperature rise was determined after the engine was warmed as close as possible to 71 ° C. (160 ° F.) for 15 minutes before running the engine with each fuel type.

Based on the data in Table 3, the fuel composition of the present invention appears to result in a calculated engine efficiency that is much better than waste vegetable oil and better than commercial B20 diesel blends.
Furthermore, the use of the fuel composition according to the present invention resulted in a lower coolant temperature increase compared to all other fuels tested, including two commercial fuels. With respect to fuel efficiency, the fuel composition of the present invention showed 10% better value than fuel made from waste vegetable oil. Further, when linearly extrapolating the decrease in efficiency with increasing percentage of biofuel in the blended product, the same fuel composition is approximately less than the biofuel currently considered acceptable, i.e., soy oil methyl ester derivative. It appears to give 5% better results. This is contrary to reports on the results of the good power and consumption of methyl esters over equivalent amounts of ethyl esters; see, for example, Peterson et al. And the literature cited therein (all of which are “pure” biofuels Compare biofuels that do not contain significant amounts of free alcohol).

  At least the previous efficiency results are surprising considering the fact that the fuel composition of the present invention contains an alcohol such as ethanol, albeit not in large quantities. The presence of such alcohols in petroleum based fuels will typically be expected to give reduced fuel efficiency values. However, the previous results appear to show that the fuel composition of the present invention provides better fuel efficiency than the “pure” biodiesel product.

  The use of the fuel composition of the present invention does not appear to require the use of any special equipment or modification of existing engine equipment. In particular, certain literature and manufacturer warranty information appears to indicate that special seals and gaskets are required when pure biofuel is used in the engine. However, none of the tests have shown to date that this is necessary with the fuel composition of the present invention.

  Conversely, the use of the fuel composition of the present invention has been shown to have at least one positive effect on the equipment in which it is used. In particular, the combustion of the fuel composition appears to provide a cleaning effect for metal engine parts. Use of the fuel composition of the present invention in a two-cycle railroad diesel engine, contrary to other studies (see, for example, Peterson et al.) That show no effect on coking, or even some deterioration. Gave much cleaner metal parts (eg fuel injectors and cylinders) than they were prior to the use of the fuel compositions of the present invention.

  At present, this effect is not fully understood. In particular, the fuel composition actually provides a detergency effect that assists in removing deposits that were previously present, or the fuel composition is simply deposited in the normal operation of the engine (eg due to vibration). It is not known whether to reduce the amount of new deposits to a level that makes it possible to remove. However, what can be said with some degree of certainty is that engine parts covered with less deposits are expected to be easier to cool and operate more efficiently.

  The terms and phrases used in this description are believed to aid in understanding the compositions and processes of the present invention. However, no limitations are imposed based on the brief description of the exemplary embodiments provided.

Claims (20)

a) at least about 2.5% (at least one _C 2 -C ₆ alcohols, and b) at least one of the one or more _C 2 -C ₆ esters of long chain fatty acids by volume): A fuel composition comprising There,
At least one of (1) the fuel composition exhibits a pH of less than about 6.8, and (2) the fuel composition has a kinematic viscosity of less than about 4.0 centistokes. Fuel composition. The fuel composition of claim 1, wherein the composition exhibits a pH of less than about 6.8 and has a kinematic viscosity of less than about 4.2 centistokes. The fuel composition according to claim 1, wherein the composition has a pH of about 5.5 to about 6.7. The fuel composition of claim 3, wherein the composition has a kinematic viscosity of less than about 4.2 centistokes. The fuel composition of claim 1, wherein the composition comprises at least about 0.2% (by volume) water. The fuel composition of claim 1, wherein the composition has a low cloud point of at least −5 ° C. when measured in accordance with ASTM D2500. A fuel composition comprising a) about 5 to about 10% (by volume) of at least one C ₂ -C ₆ alcohol, and b) at least one C ₂ -C ₆ ester of one or more long chain fatty acids. A fuel composition having a kinematic viscosity of about 3.5 to about 4.0 centistokes. The fuel composition of claim 7, wherein the composition has a pH of about 6.0 to about 6.7. The fuel composition of claim 7, wherein the composition is essentially free of at least one of sulfur and nitrogen atoms. The fuel composition of claim 7, wherein the composition comprises at least about 0.2% (by volume) water. The fuel composition of claim 7, wherein the composition has a low cloud point of at least −5 ° C. as measured according to ASTM D2500. a) providing a liquid comprising at least one C ₂ -C ₆ ester of one or more long chain fatty acids;
b) adjusting the pH of the liquid to less than 7.0 to provide an unrefined fuel composition, and c) optionally removing fines having an average diameter greater than about 1 μm. Treating the unrefined fuel composition of to provide a refined fuel composition;
A method for providing a fuel composition, comprising: Use C ₂ -C ₆ mono-ol, by transesterification of triglycerides containing composition, at least one C ₂ -C ₆ ester is provided, providing method of claim 12 fuel composition according. The C ₂ -C ₆ mono-ol comprises ethanol, the ethanol is present in excess over any stoichiometry, provides method of claim 13 fuel composition according. 13. The method of providing a fuel composition according to claim 12, wherein the fuel composition comprises at least about 0.2% (by volume) water. 13. The method of providing a fuel composition according to claim 12, wherein the fuel composition comprises less than about 5 ppm Group 1 metal ions. A method for powering a vehicle comprising:
a) a vehicle engine having a kinematic viscosity of at least about 2.5% ethanol and at least one C ₂ -C ₆ ester of one or more long chain fatty acids of less than about 4.0 centistokes; And b) a method of burning the fuel into the engine and thereby powering the vehicle. 18. The method of claim 17, wherein the engine exhaust comprises the less NOx species as compared to the exhaust when burning petrodiesel. 19. The method of claim 18, wherein the engine exhaust comprises the lower concentration of CO as compared to exhaust when burning petrodiesel. The method of claim 17, wherein the engine is a two-cycle diesel engine.