Patent Application
20130180164
The present invention generally relates to novel low sulfur fuel compositions having improved lubricity. More specifically, the present invention relates to novel low sulfur fuel compositions having butanol and demonstrating improved lubricity.
In order to reduce air pollution and the negative environmental impact associated with petroleum-based fuels, petroleum companies and vehicle manufacturers have been pursuing various technologies to reduce harmful emissions, while at the same time maintaining fuel efficiency. Sulfur-containing compounds are a component in petroleum-based fuels that can potentially form harmful compounds in the environment when the fuels are ignited or combusted. In particular, the sulfur-containing compounds can be converted into sulfur dioxide, which can then be converted into sulfur-based acids in the atmosphere. The acids are then mixed with rain to form “acid rain.” In addition, sulfur-containing compounds are known to reduce the effectiveness of catalytic converters, which has the potential to increase harmful emissions.
In this respect, governments have started to regulate the maximum sulfur content allowed in fuels, and petroleum companies and refineries have implemented processes to reduce the sulfur content to comply with these regulations. For instance, in the United States, the Environmental Protection Agency (EPA) enacted the Tier 2 Vehicle & Gasoline Sulfur Program, which limits the average amount of sulfur in gasoline and diesel fuels (see, e.g., Federal Register, Vol. 65, No. 28, published Feb. 10, 2000). Similarly, in Europe, the Euro III and IV standards, effective in 2000 and 2005, respectively, regulated the maximum amount of sulfur allowed in fuels (see, e.g., Directive 98/69/EC of the European Parliament and of the Council). In 2009, Euro V mandated that fuels must have a sulfur content of 10 ppm or less.
It is generally well known in the art that the sulfur content in fuels can be reduced by hydrodesulfurization. For instance, sulfur and sulfur-containing compounds can be reduced in fuels during the refining process by exposing the unfinished fuel to hydrogen while under pressure to form hydrogen-sulfide. Examples of such processes include SCANfining™ and OCTGAINSM desulfurization processes (see, e.g., U.S. Pat. No. 5,985,136; U.S. Pat. No. 6,013,598; and U.S. Pat. No. 6,126,814). However, the hydrodesulfurization process not only reduces the amount of sulfur and sulfur-containing compounds in the fuel, but the process also reduces the amount of other heteroatom-containing compounds, such as nitrogen-containing and oxygen-containing compounds. Yet, the same sulfur-containing and heteroatom-containing compounds that can form air pollutants and acid rain also act as natural lubricants in fuels. As such, when these compounds are removed or reduced, the resulting fuel has less lubricity.
Lubricity is an important characteristic of fuels. In fact, various components in vehicles can be damaged or can malfunction if a fuel does not have an adequate amount of lubricity. For example, vehicle fuel system components, including fuel pumps and injectors can be damaged if a fuel has inadequate lubricity. This, of course, concerns vehicle and engine manufacturers and sellers insomuch that fuels without adequate lubricity can prematurely damage vehicle parts, which would result in incurring additional expenses during any warranty period, not to mention undermines the company's goodwill with customers.
A further problem with hydrodesulfurization is that the octane rating of the fuel can be negatively impacted. This can generally occur by over-hydrogenating olefins within the unfinished fuel during the hydrodesulfurization process. Although the hydrodesulfurization processes can be adjusted to try and prevent over-hydrogenation by varying the catalyst(s) used, and the temperature and pressure at which the process occurs, such selective hydrodesulfurization processes can be costly and difficult to implement. As such, on the one hand, the final fuel can contain more hydrogenated olefins than is desirable, which can negatively impact the octane rating, or alternatively, implementing a selective hydrodesulfurization processes can be costly and difficult.
At the same time, there is a general trend in the marketplace and in the public to reduce the dependency on petroleum-based fuels. In response, renewable oxygenated fuels, including ethanol fuel blends, have entered the market. For example, in the U.S. most, if not all, regulated gasoline now includes at least 10 vol. % of ethanol. Additionally, gasoline blends having up to 85 vol. % of ethanol (E85) can be routinely found. Nevertheless, even though ethanol fuel blends can reduce the amount of petroleum needed to make fuels, ethanol is also known to reduce fuel lubricity (see, e.g., Hansen, Engine Fuel System Durability with Ethanol-Diesel Blends, available at: http://www.uiweb.uidaho.edu/bioenergy/Bioenergy2002conference/pdffiles/papers/082.pdf). Therefore, not only are the natural lubricants in fuel being reduced by hydrodesulfurization to remove sulfur and sulfur-containing compounds to comply with government regulations, but the addition of ethanol to gasoline can further reduce fuel lubricity.
In an attempt to off-set the decreased lubricity in fuels, additives can be added. For example, U.S. Pat. No. 6,361,573 discloses the use of substituted succinic acid amides or succinic acid esters as lubricity fuel additives. Additionally, U.S. Pat. No. 6,270,539 discloses the use of Mannich reaction products to improve the lubricity of fuels. Hydroxy-substituted carboxylic acids are disclosed as lubricity additives in U.S. Pat. No. 7,635,669. Lastly, U.S. Pat. No. 7,935,664 discloses the use of an overbased metal hydrocarbyl-substituted hydroxybenzoate detergent that is synthesized with a friction modifier having a C10-C40 hydrocarbon chain and an amine group, including at least one oxygen atom, or at least one ester group. However, all of the aforementioned additives not only increase the cost of the resulting fuels by requiring expensive compositions and additional processing and blending steps, but also these additives do not address the reduced octane problems associated with hydrodesulfurization.
With respect to increasing the octane rating of fuels, while also increasing fuel lubricity, U.S. Patent Application Publication No. 2011/0041792 discloses that the alkyl alkenoate compositions therein can increase the research octane number (RON) of gasoline, but actually decreases the motor octane number (MON). In particular, ethyl-4-pentenoate is disclosed as increasing the RON and decreasing the MON of a base gasoline, while also improving lubricity. However, as with the other additives discussed supra, the additives in U.S. Patent Application Publication No. 2011/0041792 not only add additional cost and processing and blending steps, but also decrease the MON of the resulting fuel.
Accordingly, there remains a need in the art for a low sulfur gasoline composition having improved lubricity, without requiring the addition of potentially expensive conventional fuel lubricant additives. There also remains a need in the art for a low sulfur gasoline composition having improved lubricity, while still having desirable RON and MON ratings. Furthermore, there remains a need for a low sulfur gasoline resolving the two aforementioned voids in the art, while also reducing the dependency on petroleum-based fuels.
The present invention generally relates to novel low sulfur fuel compositions having butanol and demonstrating improved lubricity. In this regard, an embodiment of the present invention relates to a low sulfur gasoline composition comprising:
(a) butanol; and
(b) a sulfur content less than about 25 ppm by weight;
wherein the low sulfur gasoline has a HFRR value of less than about 800 μm.
Another embodiment of the present invention relates to a process for producing a low sulfur gasoline composition having improved lubricity, the process comprising blending about 10 vol. % to about 30 vol. % of isobutanol with a gasoline blend stock, wherein the low sulfur gasoline composition comprises a sulfur content less than about 25 ppm by weight, and a HFRR value of less than about 800 μm.
In yet another embodiment, the present invention relates to a method of increasing the lubricity of a low sulfur gasoline composition, the method comprising blending about 10 vol. % to about 30 vol. % of isobutanol with a gasoline blend stock, wherein the gasoline blend stock comprises a HFRR value greater than about 800 μm, and wherein the low sulfur gasoline composition comprises:
(a) a sulfur content less than about 25 ppm by weight; and
(b) a HFRR value of less than about 800 μm.
Another embodiment of the present invention relates to a low sulfur gasoline composition comprising:
(a) isobutanol; and
(b) a sulfur content less than about 25 ppm by weight;
wherein the low sulfur gasoline has a HFRR value of less than about 800 μm.
Further, in another embodiment, the present invention relates to a method of increasing the lubricity of a low sulfur gasoline composition, the method comprising blending about 10 vol. % to about 30 vol. % of isobutanol with a gasoline blend stock, wherein the HFRR value of the low sulfur gasoline composition is reduced by at least 5% versus the HFRR value of the gasoline blend stock.
In some embodiments, the low sulfur gasoline composition may be diesel fuel, jet fuel, nonroad fuel, locomotive fuel, marine fuel, reformulated fuel, convention fuel, batch fuel, previously certified gasoline, previously designated diesel fuel, or blend stocks.
In some embodiments, the low sulfur gasoline composition may further comprise detergents, dispersants, deposit control additives, carburetor detergents, intake valve deposit detergents, intake system detergents, combustion chamber deposit control additives, fuel injector detergents, fluidizing agents, carrier oils and polymers, corrosion inhibitors, antioxidants, metal surface deactivators, metal surface passivators, combustion enhancing additives, cold-starting aids, spark promoters, spark improvers, spark plug detergents, surfactants, viscosity improvers, viscosity modifying agents, friction modifiers, fuel injector spray modifiers, fuel injector spray enhancers, fuel droplet size modification agents, volatility agents, oxygenates, water demulsifiers, water-rejection agents, water-separation agents, deicers, or mixtures thereof.
The terms “invention,” “present invention,” “instant invention,” and similar terms as used herein, are non-limiting and are not intended to limit the present subject matter to any single embodiment, but rather encompass all possible embodiments as described.
As used herein, the term “about” means within 10% of the reported numerical value; in another embodiment, the term “about” means within 5% of the reported numerical value.
As used herein, the term “HFRR” means a High Frequency Reciprocating Rig. A “HFRR value” can be determined using any version of ASTM D6079 (“Standard Test Method for Evaluating Lubricity of Diesel Fuels by the High-Frequency Reciprocating Rig”).
As used herein, “ASTM” refers to the American Society for Testing and Materials, also known as ASTM International.
As used herein, the term “butanol” may also refer to the butanol isomers such as 1-butanol (1-BuOH), 2-butanol (2-BuOH), tert-butanol (t-BuOH), and/or isobutanol (iBuOH, also known as 2-methyl-1-propanol), either individually or as mixtures thereof.
As used herein, all volume percentages (vol. %) are based on the total vol. % of the low sulfur fuel composition, unless otherwise specified. Additionally, all composition percentages are based on totals equal to 100 vol. %, unless otherwise specified.
The gasoline compositions herein provide a low sulfur alternative to prior gasoline compositions having a high sulfur content, while at the same time demonstrating improved lubricity. As discussed above, an increase in government restrictions on the sulfur content in fuels has led to a reduction in fuel lubricity due to hydrodesulfurization processing. Additionally, with increased pressure by governments, the consumer, and the marketplace to produce oxygenated fuels to reduce the use of petroleum-based fuels, ethanol fuel blends have emerged. However, the inclusion of ethanol in fuel blends further worsens the lubricity of the resulting fuel. Surprisingly, it has been found that the inclusion of butanol can restore, and can actually increase, the lubricity of low sulfur fuels. Additionally, as opposed to conventional lubricity additives, butanol, while increasing the lubricity, can also restore, and can actually increase, the octane ratings of the low sulfur fuels.
A benefit of the instant invention is that any type of fuel can be used. In this respect, the terms “fuel” and “gasoline” are used interchangeably. In particular, the present invention includes, for example, any gasoline for use in motor vehicles and motor vehicle engines, as well as any fuel used in other vehicles and engines, including boats, airplanes, locomotives, internal combustion engines, and diesel engines. Additionally, the fuels of the instant application can include any type of blend stock, including but not limited to, blend stocks for oxygenate blending (BOB), reformulated blend stocks for oxygenate blending (RBOB), and gasoline treated as blend stocks (GTAB), as well as diesel fuels, jet fuels, nonroad fuels, locomotive fuels, marine fuels, reformulated fuels, convention fuels, batch fuels, previously certified gasolines (PCG), and previously designated diesel fuels (PDD). In this respect, the fuels of the present invention may comprise mixtures of saturated, unsaturated, olefinic, and aromatic hydrocarbons, which can be derived from straight run streams, thermally or catalytically cracked hydrocarbon feedstocks, hydrocracked petroleum fractions, catalytically reformed hydrocarbons, synthetically produced hydrocarbon mixtures, hydrocarbon mixtures derived from biological catalysts or organisms, and mixtures thereof.
In some embodiments, the sulfur content in the low sulfur fuel may be less than about 25 ppm by weight, less than about 20 ppm by weight, or less than about 15 ppm by weight. In certain embodiments, the sulfur content can be less than about 10 ppm by weight, while in other embodiments, the sulfur content can be less than about 5 ppm by weight. However, even low sulfur fuels having a relatively higher sulfur content can exhibit improved lubricity when butanol is added. In this respect, in other embodiments, the low sulfur fuel can have a sulfur content up to about 50 ppm by weight, or up to about 30 ppm by weight.
Any process can be used to reduce the sulfur content in the fuel, including, but not limited to, hydrodesulfurization processes such as SCANfining™ and OCTGAINSM processes (see, e.g., U.S. Pat. No. 5,985,136; U.S. Pat. No. 6,013,598; and U.S. Pat. No. 6,126,814), as well as hydrodesulfurization or sulfur species absorption by fluid catalytic cracking (FCC), hydrocracking, isomerization, and reforming or their attendant feed hydrosulfurization processing. Furthermore, the sulfur content can be determined using any version of ASTM D2622 (“Standard Test Method for Sulfur in Petroleum Products by Wavelength Dispersive X-ray Fluorescence Spectrometry”), ASTM D5453 (“Standard Test Method for Determination of Total Sulfur in Light Hydrocarbons, Spark Ignition Engine Fuel, Diesel Engine Fuel, and Engine Oil by Ultraviolet Fluorescence”), ASTM D6920 (“Standard Test Method for Total Sulfur in Naphthas, Distillates, Reformulated Gasolines, Diesels, Biodiesels, and Motor Fuels by Oxidative Combustion and Electrochemical Detection”), ASTM D3120 (“Standard Test Method for Trace Quantities of Sulfur in Light Liquid Petroleum Hydrocarbons by Oxidative Microcoulometry”), and ASTM D7039 (“Standard Test Method for Sulfur in Gasoline and Diesel Fuel by Monochromatic Wavelength Dispersive X-ray Fluorescence Spectometry”).
With respect to the butanol useful for the invention, any isomer of butanol can be used, including, but not limited to, 1-butanol, 2-butanol, isobutanol, tert-butanol, and mixtures thereof. In certain embodiments, the butanol used consists essentially of isobutanol, wherein the amount of butanol isomers other than isobutanol does not materially interfere with improving the lubricity of the low sulfur fuel. In this regard, in an embodiment, the isomers of butanol other than isobutanol can be about 50 vol. % or less of the total butanol vol. % in the fuels. In other embodiments, the butanol isomer content other than isobutanol can be about 25 vol. % or less, about 10 vol. % or less, or about 5 vol. %, or less of the total butanol vol. % in the fuels. In another embodiment, the content of isomers of butanol other than isobutanol can be about 1 vol. % or less of the total butanol vol. % in the fuels.
The butanol can also be derived from petroleum or can be derived from biological sources, such as organic feedstocks, renewable feedstocks, or both. In this respect, the butanol used in the present invention can be biobutanol, as well as mixtures of biobutanol with petroleum-derived butanol. Methods for producing biobutanol are described in, for example, U.S. Pat. No. 7,851,188, and U.S. Patent Application Publication Nos. 2007/0092957; 2007/0259410; 2007/0292927; 2008/0182308; 2008/0274525; 2009/0155870; 2009/0305363; 2009/0305370; 2010/0221802; 2011/0097773; 2011/0312044; 2011/0312043; and PCT International Publication No. WO 2011/159998, the entire contents of each are herein incorporated by reference. Generally, in some embodiments, the low sulfur fuels can have from about 5 vol. % to about 55 vol. % of butanol in the fuels, or the fuels can have from about 10 vol. % to about 30 vol. % of butanol. In one embodiment, the low sulfur gasoline composition can have about 16 vol. % of butanol present. In another embodiment, the low sulfur gasoline composition can have about 24 vol. % of butanol present.
As noted above, it has been found that by adding butanol to low sulfur gasoline, the lubricity of the fuel can be improved. The lubricity of a fuel can be determined using a HFRR test to obtain the HFRR value of the fuel. Generally, the higher the HFRR value is for a given fuel, the worst the lubricity is for the fuel. In the instant invention, in certain embodiments, the lubricity of a low sulfur fuel can be improved by reducing the HFRR value of the fuel by at least 5% after the addition of butanol. In other embodiments, the lubricity of a low sulfur fuel can be improved by reducing the HFRR value by at least 10% after the addition of butanol. Even low sulfur fuels having a relatively high sulfur content can exhibit a reduced HFRR value of at least 5%, or at least 10%, and therefore, improved lubricity, after the addition of butanol.
In some embodiments, the HFRR value of the low sulfur fuel after the addition of butanol can be less than about 780 μm, or less than about 750 μm. In certain other embodiments, the HFRR value of the low sulfur fuel after the addition of butanol can be less than about 730 μm, and can even be less than about 700 μm. In this respect, the fuel used prior to the addition of butanol, which includes any type of fuel or gasoline, including any type of blend stock, can have a HFRR value greater than about 800 μm.
As an added benefit, not only can the butanol increase the lubricity of the low sulfur fuel, but the octane rating of the fuel can also be restored to levels prior to hydrodesulfurization, or increased to levels higher than prior to hydrodesulfurization. In this respect, in some embodiments, after being treated with butanol, the low sulfur fuels can have a RON of at least about 80, at least about 84, or at least about 89. Additionally, in some embodiments, after being treated with butanol, the low sulfur fuels can have a MON of at least about 75, at least about 79, or at least about 81. The RON can be determined using any version of ASTM D2699 (“Standard Test Method for Research Octane Number of Spark Ignition Engine Fuel”), while the MON can be determined using any version of ASTM D2700 (“Standard Test Method for Motor Octane Number of Spark Ignition Engine Fuel”).
Also notable, the addition of butanol to low sulfur fuels can prevent the corrosion of steel and aluminum surfaces in vehicle components. In this respect, the butanol can act as a corrosion inhibitor. This is especially true with respect to low sulfur fuels having ethanol, which can corrode aluminum and steel. As such, by adding butanol to a low sulfur fuel having ethanol, the butanol can prevent the ethanol from corroding aluminum and steel surfaces.
The low sulfur gasoline compositions herein can also have at least about 0.5 vol. % of C3-C10 olefins present, up to about 25 vol. %. The olefins can be mono-olefins, including alpha-olefins, which can be selected from pentene isomers, hexene isomers, heptene isomers, octene isomers, nonene isomers, decene isomers, and mixtures thereof. Moreover, the low sulfur gasoline compositions of the present invention can have an aromatic content up to about 50 vol. %, or up to about 40 vol. %. Furthermore, the low sulfur fuels herein can have a Reid Vapor Pressure (RVP) of at least about 5 psi, or at least about 6 psi. The RVP can be determined using ASTM D4953 (“Standard Test Method for Vapor Pressure of Gasoline and Gasoline Oxygenate Blends, Dry Method”), ASTM D5190 (“Standard Test Method for Vapor Pressure of Petroleum Products, Automatic Method”), ASTM D5191 (“Standard Test Method for Vapor Pressure of Petroleum Products, Mini Method”), and ASTM D5482 (“Standard Test Method for Vapor Pressure of Petroleum Products, Mini Method—Atmospheric”).
The low sulfur fuels of the present application can also have various additives that are known in the art, such as, but not limited to, detergents, dispersants, deposit control additives, carburetor detergents, intake valve deposit detergents, intake system detergents, combustion chamber deposit control additives, fuel injector detergents, fluidizing agents, carrier oils and polymers, corrosion inhibitors, antioxidants, metal surface deactivators, metal surface passivators, combustion enhancing additives, cold-starting aids, spark promoters, spark improvers, spark plug detergents, surfactants, viscosity improvers, viscosity modifying agents, friction modifiers, fuel injector spray modifiers, fuel injector spray enhancers, fuel droplet size modification agents, volatility agents, oxygenates, water demulsifiers, water-rejection agents, water-separation agents, deicers, and mixtures thereof.
The low sulfur gasoline compositions having improved lubricity disclosed herein can be made by blending the requisite amount of butanol or butanol isomer with a low sulfur fuel. In some embodiments, the butanol can be blended with a low sulfur blend stock. The blending process can be carried out by known processes, and can occur at the refinery or mixing terminals, such as truck terminals, railway terminals, and marine terminals.
The following examples are illustrative of preferred low sulfur fuels having improved lubricity, and are not intended to be limitations thereon.
The lubricity performance of the low sulfur fuel compositions of the present invention were measured according to the HFRR test, which consists of a loaded upper ball 6 mm in diameter that oscillates against a static lower plate. Both friction and contact resistance are monitored throughout the test. The HFRR tests were conducted largely according to the standard procedure published as ASTM D6079-04 (“Standard Test Method for Evaluating Lubricity of Diesel Fuels by the High-Frequency Reciprocating Rig”) in which a load of 2N (200 g) was applied, the stroke length was 1 mm, the reciprocating frequency was 50 Hz, and sample temperature of 25° C. The ambient temperature and humidity were controlled within the specified limits. The specimen ball was a grade 28 (American National Standards Institute, ANSI B3.12), AISI (American Iron and Steel Institute) E-52100 steel with a Rockwell hardness “C” scale (HRC) number of 58-66 (International Organization for Standardization, ISO 6508), and a surface finish of less than 0.05 μm Ra, and the lower plate was AISI E-52000 steel machined from an annealed rod, with a Vickers hardness “HV30” scale number of 190-210-(ISO 6507/1). It is turned, lapped, and polished to a surface finish of less than 0.02 μm Ra. The lower specimen was contained in a reservoir for gasoline sample testing that had a surface area of approximately 15 cm2. The top of the reservoir was covered with a Teflon® cap having a central hole and a Teflon® disc with a hole to accommodate the upper ball holder shaft, thus forming a sliding arrangement to contain the sample vapors and allow oscillation of the upper ball. Approximately 4 ml of sample was used.
Low Sulfur Fuels without Isobutanol
To a low sulfur alkylate fuel having 6 ppm of sulfur, heavy reformate (HUF), light reformate (LUF), and light catalytically cracked naphtha (LS DAN) were added in the amounts indicated in Tables 2 and 3. The aromatic (ARO) and olefin (OLE) content were calculated in both weight percent (wt. %) and vol. %. The sulfur (S) content was calculated in ppm by weight. The HFRR major values, minor values, and average values as determined were reported in microns (μm) in Table 4.
To the same low sulfur alkylate fuel used in Comparative Examples 1 and 2, 15.8 vol. % and 16.3 vol. % of isobutanol was added, respectively. Heavy reformate (HUF), light reformate (LUF), and light catalytically cracked naphtha (LS DAN) were also added in the amounts indicated in Tables 2 and 3. The aromatic (ARO) and olefin (OLE) content were calculated in weight percent (wt. %) and vol. %. The sulfur (S) content was calculated in ppm by weight. The HFRR major values, minor values, and average values as determined were reported in microns (μm) in Table 4.
When comparing Example 1 having isobutanol to Comparative Example 1 without isobutanol, which have similar aromatic and olefin vol. %, the average HFRR value decreased from 849 μm to 761 μm. Additionally, when Example 2 having isobutanol is compared with Comparative Example 2 without isobutanol, which also have similar aromatic and olefin vol. %, the average HFRR value decreased from 841 μm to 728 μm.
To a low sulfur reformulated blend stock for oxygenate blending (RBOB) formulated for 10% of ethanol (E10), ethanol was added in approximately 10 vol. % and 15 vol. %, respectively. The HFRR major values, minor values, and average values as determined were reported in microns (μm) in Table 5. The characteristics of the RBOB are reported in Table 6.
To the same low sulfur reformulated blend stock for oxygenate blending (RBOB) used in Comparative Examples 3 and 4, approximately 16 vol. % and 24 vol. % of isobutanol was added, respectively. The HFRR major values, minor values, and average values as determined were reported in microns (μm) in Table 5.
When comparing Example 3 having isobutanol to Comparative Example 3 having ethanol, the average HFRR value decreased from 794 μm to 736 μm by using butanol instead of ethanol. Additionally, when Example 4 having isobutanol is compared with Comparative Example 4, the average HFRR value decreased from 744 μm to 676 μm.
The present subject matter being thus described, it will be apparent that the same may be modified or varied in many ways. Such modifications and variations are not to be regarded as a departure from the spirit and scope of the present subject matter, and all such modifications and variations are intended to be included within the scope of the following claims:
This application claims the benefit of U.S. Provisional Application No. 61/512,859, filed on Jul. 28, 2011; the entire contents of which are herein incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61512859 | Jul 2011 | US |
