Patent Description:
Internal combustion engines are a type of engine where combustion of a fuel composition occurs in a combustion chamber to transfer chemical energy into mechanical energy. One type of internal combustion engine is a compression ignition engine in which ignition of the fuel composition is caused by elevated temperature of the air by mechanical compression. Fuel compositions used in compression ignition engines can include, but are not limited to, fuel oils, such as diesel fuels, distillate fuel oils, and residual fuel oils.

Ignition and combustion properties of residual fuel oils can be determined by the method specified in IP <NUM>: Determination of Ignition and Combustion Characteristics of Residual Fuels. In this test method, multiple injections of the residual fuel oil are made into a heated and pressurized combustion chamber of constant volume. The combustion chamber pressure is monitored versus time to determine the various characteristics, including the main combustion delay (MCD). The MCD can be used to calculate an estimated cetane number (ECN). The ECN is generally accepted as an indicator of combustion quality for residual fuel oils. In order to determine, whether a fuel composition can burn in an engine, a minimum cetane number is required. For residual fuel oils, however it can be difficult to measure the MCD, because access to instruments for testing can be limited. Since MCD is used in calculation of ECN, this makes measurement of ECN difficult. Accordingly, the calculated carbon aromaticity index (CCAI) has been developed to predict the ignition quality of residual fuel oils, which is the first part of the overall combustion process.

The CCAI is calculated based on measured density and viscosity properties of residual fuel oils. The formula for calculation of CCAI is found in ISO <NUM>, Clause <NUM>. The CCAI thus can be an indicator of ignition quality for residual fuel oils even where measurement of MCD to provide ECN is unavailable. However, CCAI may not accurately reflect combustion quality of residual fuel oils with low sulfur. With the International Maritime Organization implementing a new global sulfur limit of <NUM> wt. % sulfur, effective January <NUM>, <NUM>, this is expected to become a more extensive issue.

Patent application publication <CIT> describes marine fuel oil compositions comprising a distillate fraction having a sulfur content of <NUM> wt% or more and a resid fraction having a sulfur content of <NUM> wt% or less.

Disclosed herein is a method of blending fuel compositions according to claim <NUM>.

These drawings illustrate certain aspects of the present disclosure and should not be used to limit or define the disclosure.

The FIGURE illustrates a chart of estimated cetane number (ECN) versus calculated carbon aromaticity index (CCAI).

Described herein but not claimed are fuel compositions that are low sulfur and have adequate combustion quality. As used herein, a fuel composition is defined as having "adequate combustion quality" where the fuel composition has an estimated cetane number (ECN) of about <NUM> or greater. The technique for determining ECN is described in IP <NUM>/<NUM>: Determination of Ignition and Combustion Characteristics of Residual Fuels.

As described above, the International Maritime Organization is implementing new standards (commonly referred to as "IMO <NUM>") requiring development of new marine fuel compositions that are low sulfur to meet the new sulfur requirements that are being implemented on January <NUM>, <NUM>. In addition to IMO <NUM>, marine fuel compositions classified as residual marine fuels must meet the requirements of ISO <NUM>, Fuel Standard Sixth Edition <NUM>, Table <NUM>, while marine fuel compositions classified as distillate marine fuels must meet the requirements of ISO <NUM>, Fuel Standard Sixth Edition <NUM>, Table <NUM>.

To provide fuel compositions that are low sulfur and have adequate combustion quality, the present method includes blending one or more residual components that are typically higher in sulfur content with one or more petroleum distillate fractions that are typically lower in sulfur content. The additional petroleum distillate fractions may include any number of fractions from a crude refining process. In at least one embodiment, the fuel composition may be classified as a residual marine fuel composition as defined in ISO <NUM>. Suitable fuel compositions include a residual component and one or more petroleum distillate fractions such that the fuel compositions have the properties enumerated herein, including sulfur content, CCAI, density, kinematic viscosity at <NUM> ("KV50"), and ECN.

The fuel compositions described herein include one or more residual components. The residual components typically include a complex mixture of heavy petroleum components also known in the art as resid, residual, or residuum. The residual components are typically residue from refinery operations, such as distillation or cracking units. In a typical refinery, crude oils can be subjected to atmospheric distillation to produce lighter fractions such as gas oils, kerosene, gasolines, straight run naphtha, etc. Petroleum fractions in the gasoline boiling range, such as naphthas, and those fractions which can readily be thermally or catalytically converted to gasoline boiling range products, such as gas oils, are typically the most valuable product streams in the refinery. The residue from the atmospheric distillation step may then be distilled at a pressure below atmospheric pressure. This later distillation step produces a vacuum gas oil distillate and a vacuum residual oil which typically are substantially cheaper than gas oils. The residual components used in the fuel compositions can be the residuals from the atmospheric distillation, vacuum distillation, or other suitable refinery operation.

Examples of suitable residual components may include, but are not limited to, vacuum residuals from fractionating (total/partial) crude oils, atmospheric residuals from fractionating (total/partial) crude oils, visbreaker residuals, FCC bottoms, hydrotreated residual, and deasphalted residuals, among others. Vacuum residuals are the bottoms product from a column under vacuum where the heaviest distilled product is nominally <NUM> °F (<NUM>). Atmospheric residuals are the bottoms product produced in atmospheric distillation where the endpoint of the heaviest distilled product is nominally <NUM> °F (<NUM>). As used herein, the term "nominally" means here that reasonable experts may disagree on the exact cut point for these terms, but probably by no more than +/-<NUM> (<NUM> °F) or at most +/-<NUM> (<NUM> °F). Visbreaker residuals are the residuals from thermal cracking processes for increasing yield from atmospheric and vacuum residuals. FCC bottoms are the bottoms product oil from fluid catalytic cracking, including, but not limited to, slurry oil and clarified slurry oil. Combinations of two or more different residual components may also be suitable for use in certain applications. In at least one embodiment, the residual component may include two or more residual components. For example, the residual component may include a first residual component and a second residual component, such as a vacuum residual and an FCC bottoms. One of ordinary skill in the art, with the benefit of this disclosure, should be able to select an appropriate residual component (or combination of residual components) for a particular application.

In some embodiments, the residual component may have a high sulfur content. For example, the residual component may have a sulfur content in wt. % of greater than about <NUM>, for example about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>. In some embodiments, the residual component may have a KV50 in centistokes ("cSt") of about <NUM> or greater, for example about <NUM> to about <NUM>,<NUM>,<NUM>, about <NUM>,<NUM> to about <NUM>,<NUM>,<NUM>, about <NUM>,<NUM> to about <NUM>,<NUM>,<NUM>, about <NUM>,<NUM> to about <NUM>,<NUM>,<NUM>, about <NUM>,<NUM> to about <NUM>,<NUM>, about <NUM>,<NUM> to about <NUM>,<NUM>, about <NUM>,<NUM> to about <NUM>,<NUM>, about <NUM> to about <NUM>,<NUM>, or about <NUM> to about <NUM>. The standardized test method in ISO <NUM> (<NUM>) is defined as providing the procedure for determining KV50. In at least one embodiment, the fuel composition may include a first residual component having a higher KV50 and a second residual component having a lower KV50. For example, a first residual component may have a KV50 of about <NUM>,<NUM> to about <NUM>,<NUM>,<NUM>, about <NUM>,<NUM> to about <NUM>,<NUM>,<NUM>, about <NUM>,<NUM> to about <NUM>,<NUM>,<NUM>, about <NUM>,<NUM> to about <NUM>,<NUM>, about <NUM>,<NUM> to about <NUM>,<NUM>, or about <NUM>,<NUM> to about <NUM>,<NUM>, while a second residual component may have a KV50 of about <NUM> to about <NUM>,<NUM> or about <NUM> to about <NUM>. By way of further example, the fuel composition may include a vacuum residual having a KV50 of about <NUM>,<NUM> to about <NUM>,<NUM>,<NUM>, about <NUM>,<NUM> to about <NUM>,<NUM>,<NUM>, about <NUM>,<NUM> to about <NUM>,<NUM>,<NUM>, about <NUM>,<NUM> to about <NUM>,<NUM>, about <NUM>,<NUM> to about <NUM>,<NUM>, or about <NUM>,<NUM> to about <NUM>,<NUM>, and a FCC bottoms having a KV50 of about <NUM> to about <NUM>,<NUM> or about <NUM> to about <NUM>. One of ordinary skill in the art, with the benefit of this disclosure, should be able to select a KV50 for the residual component (or combinations thereof) for a particular application.

The residual component may be included in the fuel compositions in any suitable concentration, to provide the fuel composition with desirable properties. For example, the residual component may be included in an amount in vol. % of at least <NUM>, for example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>. In some embodiments, the residual component may include a first residual component in an amount in vol. % of at least <NUM> and a second residual component in an amount in vol. % of at least <NUM>. One of ordinary skill in the art with the benefit of this disclosure should be able to select an appropriate amount of the residual component to include in the fuel compositions for a particular application.

As previously described, the residual components is blended with one or more petroleum distillate fractions. The petroleum distillate fractions may include, for example, any of a variety of petroleum fractions obtained from refinery operations. The combustion quality of the distillate component may be defined by the cetane index, as defined by Procedure A in ASTM D4737 (<NUM>) - Standardized Method for Calculated Cetane Index by Four Variable Equation. A distillate component with low combustion quality will have a cetane index of about <NUM> or less. A distillate component with average combustion quality will have a cetane index of <NUM> to <NUM>. A distillate component with excellent combustion quality will have a cetane index of about <NUM> or greater. The fuel composition includes a first petroleum distillate fraction of average combustion quality. In at least one embodiment, the fuel composition may include a second petroleum distillate fraction of excellent combustion quality.

The fuel composition includes a first petroleum distillate fraction. The first petroleum distillate fraction has a cetane index of <NUM> to <NUM>, for example, a cetane index of <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. Thus, the first petroleum distillate fraction may be considered to have average combustion quality. Additional properties that can characterize the first petroleum distillate fraction can include, but are not limited to, density, KV50, and CCAI. The first petroleum distillate fraction has a density in kg/m<NUM> of <NUM> or less. In some embodiments, the first petroleum distillate fraction may have a KV50 in cSt of about <NUM> to about <NUM>, for example about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>. In some embodiments, the first petroleum distillate fraction may have a CCAI of <NUM> to about <NUM>,<NUM>, for example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>,<NUM>. Examples of first petroleum distillate fractions may include any of a variety of petroleum fractions from refinery operations, whether an intermediate or final product, including, but not limited to, light cycle oil, light coker gas oil, heavy cycle oil, heavy coker gas oil, and steam cracked gas oil.

In some embodiments, the first petroleum distillate fraction may have a low sulfur content, such that when blended with the residual component, the fuel composition may be considered IMO <NUM> compliant. For example, the first petroleum distillate fraction may have a sulfur content in wt. % of less than about <NUM>, for example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>.

The first petroleum distillate fraction may be included in the fuel composition in an amount in vol. % of at least about <NUM> or greater as desired for a particular application. For example, the first petroleum distillate fraction may be included in the fuel composition in an amount sufficient to provide a lower sulfur content, provide improved combustion quality, or provide both lower sulfur content and improved combustion quality. In some embodiments, the first petroleum distillate fraction may be included in the fuel composition in an amount in vol. % of <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. In at least one embodiment, the first petroleum distillate fraction may be included in the fuel composition in an amount in vol. % of at least about <NUM> or greater, or at least about <NUM> or greater. One of ordinary skill in the art with the benefit of this disclosure should be able to select an appropriate amount of the first petroleum distillate fraction to include in the fuel compositions for a particular application.

In at least one embodiment, the fuel composition may further include a second petroleum distillate fraction. The second petroleum distillate fraction may be defined as having a cetane index of about <NUM> or greater, for example, a cetane index of about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>. Thus, the second petroleum distillate fraction may be considered to have excellent combustion quality. Additional properties that can characterize the second petroleum distillate fraction can include, but are not limited to, density, KV50, and CCAI. In some embodiments, the second petroleum distillate fraction may have a density in kg/m<NUM> of about <NUM> to about <NUM>,<NUM>, for example about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>,<NUM>, or about <NUM> to about <NUM>,<NUM>. In some embodiments, the second petroleum distillate fraction may have a KV50 in cSt of about <NUM> to about <NUM>, for example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>. In some embodiments, the second petroleum distillate fraction may have a CCAI of about <NUM> to about <NUM>, for example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>. Examples of second petroleum distillate fractions may include any of a variety of petroleum fractions from refinery operations, whether an intermediate or final product, including, but not limited to, hydrotreated straight run distillate, hydrocracker distillate, hydrotreated gas oil, heavy vacuum gas oil, light vacuum gas oil, and heavy atmospheric gas oil.

In some embodiments, the second petroleum distillate fraction may have a low sulfur content, such that when blended with the residual component, the fuel composition may be considered IMO <NUM> compliant. For example, the second petroleum distillate fraction may have a sulfur content in wt. % of less than about <NUM>, for example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>.

Where used, the second petroleum distillate fraction may be included in the fuel composition in any suitable amount as desired for a particular application. For example, the second petroleum distillate fraction may be included in the fuel composition in an amount sufficient to provide a lower sulfur content, provide improved combustion quality, or provide both lower sulfur content and improved combustion quality. In some embodiments, the second petroleum distillate fraction may be included in the fuel composition in an amount in vol. % of about <NUM> to about <NUM>, for example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>. In at least one embodiment, the second petroleum distillate fraction may be included in the fuel composition in an amount in vol. % of at least about <NUM> or greater, at least about <NUM> or greater, or at least about <NUM> or greater. One of ordinary skill in the art with the benefit of this disclosure should be able to select an appropriate amount of the second petroleum distillate fraction to include in the fuel compositions for a particular application.

An example fuel composition may include a residual component in an amount of <NUM> vol. % and a first petroleum distillate fraction in an amount of <NUM> vol. The residual component may include any suitable residual component described herein. In at least one embodiment, the residual component may include a vacuum residual. The first petroleum distillate fraction has a cetane index of about <NUM> to about <NUM>.

Another example fuel composition may include a first residual component in an amount of about <NUM> vol. % to about <NUM> vol. %, a second residual component in an amount of about <NUM> vol. % to about <NUM> vol. %, and a first petroleum distillate fraction in an amount of about <NUM> vol. % to about <NUM> vol. The first residual component may include any suitable residual component described herein. In at least one embodiment, the first residual component may include a vacuum residual. The second residual component may include any suitable residual component described herein. In at least one embodiment, the second residual component may include FCC bottoms. The first petroleum distillate fraction has a cetane index of about <NUM> to about <NUM>.

Another example fuel composition may include a first residual component in an amount of about <NUM> vol. % to about <NUM> vol. %, a second residual component in an amount of about <NUM> vol. % to about <NUM> vol. %, and a second petroleum distillate fraction in an amount of about <NUM> vol. % to about <NUM> vol. The first residual component may include any suitable residual component described herein. In at least one embodiment, the first residual component may include a vacuum residual. The second residual component may include any suitable residual component described herein. In at least one embodiment, the second residual component may include FCC bottoms. The second petroleum distillate fraction may have a cetane index of about <NUM> or greater.

Another example fuel composition may include a first residual component in an amount of about <NUM> vol. % to about <NUM> vol. %, a second residual component in an amount of about <NUM> vol. % to about <NUM> vol. %, a first petroleum distillate fraction in an amount of about <NUM> vol. % to about <NUM> vol. %, and a second petroleum distillate fraction in an amount of about <NUM> vol. % to about <NUM> vol. The first residual component may include any suitable residual component described herein. In at least one embodiment, the first residual component may include a vacuum residual. The second residual component may include any suitable residual component described herein. In at least one embodiment, the second residual component may include FCC bottoms. The first petroleum distillate fraction has a cetane index from about <NUM> to about <NUM>. The second petroleum distillate fraction may have a cetane index of about <NUM> or greater.

Various desirable properties for embodiments of the fuel compositions may be specified. Fuel compositions prepared by the present method are enumerated by the following properties: (i) a sulfur content of about <NUM> wt. % or less; (ii) a CCAI value of about <NUM> or less; (iii) a density at <NUM>° C of about <NUM>/m<NUM> to about <NUM>/m<NUM>; (iv) a kinematic viscosity at <NUM>° C ("KV50") of about <NUM> cSt to about <NUM> cSt; and (v) an estimated cetane number of about <NUM> or greater. Fuel compositions with these enumerated properties should have adequate combustion quality while being low sulfur. Even though CCAI alone may not be a predictor of combustion quality, by providing a fuel composition with the preceding enumerated properties, adequate combustion may be provided. In an at least one embodiment, the example fuel compositions may further be enumerated by at least one of the following properties: i) a minimum concentration of <NUM> vol. % of the first petroleum distillate having a cetane index of about <NUM> to about <NUM>; or (ii) a minimum concentration of <NUM> vol. % of the second petroleum distillate having a cetane index of about <NUM> or greater.

One property that can be used for selection and/or modification of embodiments of the fuel compositions is sulfur content. By way of example, the marine fuel compositions may be considered IMO <NUM> compliant in that the fuel oil compositions have a sulfur content of about <NUM> wt. Examples of suitable marine fuel compositions may have a sulfur content in wt. % of <NUM> to <NUM>, for example, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM> or <NUM> to <NUM>. One of ordinary skill in the art, with the benefit of this disclosure, should be able to select an appropriate sulfur content for embodiments of the fuel compositions, as desired for a particular application.

Another property that can be used for selection and/or modification of embodiments of the fuel compositions is CCAI. As previously described, CCAI is calculated based on measured density and viscosity properties of a fuel composition. The formula for calculation of CCAI is found in ISO <NUM>, Clause <NUM>. The fuel composition prepared by the present method have a CCAI of about <NUM> or less. For example, the fuel compositions may have a CCAI of <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. One of ordinary skill in the art, with the benefit of this disclosure, should be able to select an appropriate CCAI for embodiments of the fuel compositions, as desired for a particular application.

Another property that can be used for selection and/or modification of embodiments of the marine fuel compositions is density. The standardized test method in ISO <NUM> (June <NUM>, <NUM>) is defined as providing the procedure for determination of density. The fuel compositions prepared by the present method have a density at <NUM>° C in kg/m<NUM> of <NUM> to <NUM>,<NUM>, <NUM> to <NUM>, <NUM> to <NUM>,<NUM>, or <NUM>,<NUM> to <NUM>,<NUM>. One of ordinary skill in the art, with the benefit of this disclosure, should be able to select an appropriate density for embodiments of the fuel compositions, as desired for a particular application.

Yet another property that can be used for selection and/or modification of embodiments of the marine fuel compositions is KV50. The standardized test method in ISO <NUM> (<NUM>) is defined as providing the procedure for determining KV50. Fuel compositions prepared by the present method have a KV50 in cSt of <NUM> to <NUM>, for example, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, 100t to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. In some embodiments, the fuel composition may have a KV50 in cSt of <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less. One of ordinary skill in the art, with the benefit of this disclosure, should be able to select an appropriate KV50 for embodiments of the fuel compositions, as desired for a particular application.

Yet another property that can be used for selection and/or modification of embodiments of the fuel compositions is ECN. As previously described, a fuel composition is defined as having "adequate combustion quality" where the fuel composition has an ECN of <NUM> or greater. The technique for determining ECN is described in IP <NUM>: Determination of Ignition and Combustion Characteristics of Residual Fuels. In some embodiments, a fuel composition may have an ECN of <NUM> to <NUM>. For example, the fuel composition may have an ECN of <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. Specific examples of suitable marine fuel compositions may have an ECN of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. One of ordinary skill in the art, with the benefit of this disclosure, should be able to select an appropriate ECN for embodiments of the fuel compositions, as desired for a particular application.

ECN and CCAI both may be used as a predictor of combustion quality. In some examples, ECN and CCAI for a fuel composition may follow a linear trend. However, in some examples, the ECN and CCAI may not follow a linear trend. By way of example, it has been found that CCAI can either under predict the measured ECN or over predict the measured ECN. In these instances, CCAI may not be a good predictor of combustion quality. For example, CCAI may under predict the measured ECN for a fuel composition where the residual component includes a hydrotreated residual material. By way of further example, CCAI may over predict combustion quality for a fuel composition where the residual component has a T50 of about <NUM> or greater and a first petroleum distillate fraction with a density of about <NUM>/m<NUM> or less. T50 is the temperature at which <NUM> vol% of the sample being distilled has been recovered as condensate, as measured using ASTM D2287. When CCAI over predicts combustion quality, combustion quality of the fuel composition may be controlled, for example, by including average and/or excellent combustion quality distillate fractions in the fuel composition.

Yet another property that can be used for selection and/or modification of embodiments of the fuel compositions is concentration of the first petroleum distillate fraction. The first petroleum distillate fraction has a cetane index of from <NUM> to <NUM>, thus being considered to have average combustion quality. By including a sufficient amount of the first petroleum distillate fraction in examples of the fuel compositions, embodiments may provide a fuel composition with adequate combustion quality even where the residual component does not have an adequate combustion quality by itself. The first petroleum distillate fraction is included in the fuel composition in an amount in vol. % of at least <NUM> or greater, at least <NUM> or greater, or at least <NUM> or greater. One of ordinary skill in the art with the benefit of this disclosure should be able to select an appropriate amount of the first petroleum distillate fraction to include in the fuel compositions for a particular application.

Yet another property that can be used for selection and/or modification of embodiments of the fuel compositions is concentration of the second petroleum distillate fraction. The second petroleum distillate fraction may be defined as having a cetane index of about <NUM> or greater, thus being considered to have excellent combustion quality. By including a sufficient amount of the second petroleum distillate fraction in examples of the fuel compositions, embodiments may provide a fuel composition with adequate combustion quality even where the residual component does not have an adequate combustion quality by itself. In some embodiments, the second petroleum distillate fraction may be included in the fuel composition in an amount in vol. % of at least about <NUM> or greater, at least about <NUM> or greater, or at least about <NUM> or greater. One of ordinary skill in the art with the benefit of this disclosure should be able to select an appropriate amount of the second petroleum distillate fraction to include in the fuel compositions for a particular application.

Accordingly, the preceding description describes examples of fuel compositions that are low sulfur and have adequate combustion quality. The compositions and methods disclosed herein may include any of the various features disclosed herein, including one or more of the following embodiments.

To facilitate a better understanding of the present disclosure, the following examples of certain aspects of some embodiments are given.

In this example, the properties of forty-two different sample fuel composition are provided. Of these sample fuel compositions, thirty-six fuel compositions were prepared and measured to obtain the properties, and six fuel compositions are modeled blends with the properties predicted based on the measured properties of the components. The fuel compositions that were prepared are listed as Sample Compositions <NUM>-<NUM>. The modeled blends are listed as Sample Compositions MB-<NUM> to MB-<NUM>. The components were obtained from six different refineries, identified as Refiners A-E. Sample Compositions MB-<NUM>, MB-<NUM>, and MB-<NUM> are according to the invention, the other Sample Compositions are comparative examples.

Table <NUM> below shows the composition of the sample fuel compositions.

The <NUM> vol% of the <NUM>nd Distillate Blend B contains <NUM> vol % FLUX <NUM>, <NUM> vol% FLUX <NUM> bottoms, <NUM> vol % FLUX <NUM> bottoms, <NUM> vol% FLUX <NUM>, and <NUM> vol % FLUX <NUM>.

The <NUM> vol% of the <NUM>nd Distillate Blend C contains <NUM> vol % FLUX <NUM>, <NUM> vol% FLUX <NUM> bottoms, <NUM> vol % FLUX <NUM> bottoms, <NUM> vol% FLUX <NUM>, and <NUM> vol % FLUX <NUM>.

The <NUM> vol% of the <NUM>nd Distillate Blend D contains <NUM> vol % FLUX <NUM>, <NUM> vol% FLUX <NUM> bottoms, <NUM> vol % FLUX <NUM> bottoms, <NUM> vol% FLUX <NUM>, and <NUM> vol % FLUX <NUM>.

The Figure is a plot of measured or predicted ECN versus calculated CCAI for the sample compositions of Tables <NUM> and <NUM>. While, the sample compositions of Table <NUM> meet most of the ISO <NUM> specifications, including CCAI, the FIGURE illustrates that the ECN values reveal a range of ECN values for similar CCAI values, thus indicating the CCAI alone may not guarantee adequate combustion quality of a residual fuel composition.

Typically, ECN and CCAI follow a linear trend. We have found examples where the trend is not linear. Either CCAI under predicts the measured ECN (Class B) or the CCAI over predicts the measured ECN (Class C). The latter class is potentially problematic because the CCAI may falsely indicate that the fuel oil has acceptable combustion quality. Class B is defined as a fuel oil containing hydrotreated residual material (e.g., see VR9). Class C is defined as a fuel oil containing a residual material with a T50 of <NUM> or greater and a first petroleum distillate fraction with a density of <NUM>/m<NUM> or less. When the fuel oil blend meets the characteristics of Class C, the combustion should be measured by ECN. In the absence of measuring ECN, the combustion quality of the blend can be controlled by including either a larger amount of the first petroleum distillate fraction or a larger amount of the second petroleum distillate fraction as compared to the initial blend recipe.

Table <NUM> below shows the measured properties of the vacuum residuals used in the sample compositions provided in Table <NUM> above. Eleven different vacuum residuals were used in the sample compositions indicated as VR1 to VR <NUM>. The properties indicated in Table <NUM> below for VR10 and VR11 are for a mixture of <NUM> vol. % of a vacuum residual and <NUM> vol. % of HCO-<NUM>. The boiling point ranges in the table below (and following tables) were measured in accordance with ASTM D2287 for a simulated distillation. The resid T90 for certain Vacuum Residuals are not reported in Table <NUM> below as the samples were above the upper temperature limit of the test method (i.e., "adl").

Table <NUM> below shows the measured properties of the FCC bottoms components used in the sample compositions provided in Table <NUM> above. Four different FCC bottoms components were used in the sample compositions indicated as FCCB1, FCCB2, FCCB3, and FCCB4.

Table <NUM> below shows the measured properties of the first petroleum distillate fraction used in the sample compositions provided in Table <NUM> above. As indicated, a number of different petroleum distillate fractions were used, including: light cycle oil (LCO); heavy cycle oil (HCO); a mixture of light cycle oil and heavy cycle oil (LCO + HCO); heavy cracked gas oil (HCGO); gas oil (GO), heavy heating oil (HHO); and steam cracked gas oil (SCGO).

Table <NUM> below shows the measured properties of the second petroleum distillate component used in the sample compositions provided in Table <NUM> above. As indicated, the following petroleum distillate fractions were used: hydrofined gas oil (GOHF2); vacuum gas oil (VGO); heavy vacuum gas oil (HVGO); hydrocracker bottoms (HC Btms); light vacuum gas oil (LVGO); heavy atmospheric gas oil (HAGO); marine gas oil (MGO); and flux.

Claim 1:
A method of blending fuel compositions, comprising: blending one or more residual components having a T50 of <NUM> or greater and at least <NUM> vol.% of one or more petroleum distillate fractions having a cetane index of <NUM> to <NUM> and a density of <NUM>/m<NUM> or less as determined according to ISO <NUM>, wherein the one or more residual components have a higher sulfur content than the one or more petroleum distillate fractions, to prepare a fuel composition, wherein the fuel composition has the following enumerated properties: a sulfur content of <NUM>% or less by weight of the fuel composition; a calculated carbon aromaticity index of <NUM> or less; a density at <NUM> of <NUM>/m<NUM> to <NUM>,<NUM>/m<NUM> as determined according to ISO <NUM>; a kinematic viscosity at <NUM> of <NUM> centistokes to <NUM> centistokes; and an estimated cetane number of <NUM> or greater.