FIELD

[0001] This invention relates to formation of low mass asphalts, such as asphalts suitable for use in roofing applications, from heavy crude oils.

BACKGROUND

[0002] Asphalt is a material commonly used in paving and roofing applications. The types of asphalt that can be used in paving and roofing applications can be constrained both by commercial requirements as well as national and/or regional regulations. As an example, one specification for asphalt can be a performance grade specification, which provides a specification related to being able to withstand maximum and minimum temperatures that are likely to be encountered.

[0003] Paving and roofing asphalts are typically residues of vacuum distillation of crude oil. One type of roofing asphalt product that is challenging to create is roofing asphalt flux (RAF). Roofing asphalt flux is a desirable asphalt product for making roofing shingles. The target kinematic viscosity at 100°C (KV100) for forming this type of asphalt product is typically between 800 cSt and 1500 cSt, which corresponds to a relatively soft asphalt grade. After forming an asphalt with an appropriate kinematic viscosity, the asphalt is then oxidized at high temperature (greater than 200°C) to form an asphalt shingle coating product. Unfortunately, it is difficult to make roofing asphalt flux from most types of crude oils. Heavier crude oils (e.g., API gravity of 24° or less) can provide an asphalt with a sufficient hardness after oxidation to make high quality shingles. However, an asphalt with a KV100 of 1200 cSt or less that is formed by distillation of a heavier crude oil typically has a volatility that is too high and/or a flash point that is too low to satisfy current industry standards and/or regulations. Using a lighter crude oil (e.g. API gravity greater than 24°) to make an asphalt with a KV100 between 700 cSt and 1200 cSt can reduce or minimize the difficulties with volatility and flash point. However, using such lighter crude oils to produce softer grades of asphalts can present other difficulties, such as a reduction in the quality of roofing shingles that can be formed from the asphalts. For example, forming softer grades of asphalts from lighter crude oil feedstocks can result in asphalt products with high temperature susceptibility to break down.

[0004] U.S. Patent 6,258,255 describes methods for performing a co-vacuum distillation of a vacuum gas oil fraction with a crude oil in order to form asphalt products with reduced volatility and/or increased flash point. While blending the right type of vacuum gas oil with a crude oil can result in production of an improved asphalt fraction, the incorporation of the vacuum gas oil into an asphalt product corresponds to a substantial degradation of the value of the vacuum gas oil, as vacuum gas oil fractions can typically also be used for production of other higher value products. Additionally, this can reduce throughput for the distillation tower, as a portion of the volume of the distillation tower is consumed by the additional vacuum gas oil, as opposed to just distilling crude oil.

[0005] What is needed are systems and methods for producing desirable asphalt products from crude oils while reducing or minimizing the downgrading of higher value fractions during the asphalt production process.

SUMMARY

[0006] In an aspect, a method for forming an asphalt fraction is provided. The method includes separating a plurality of fractions having a T10 distillation point of 430°C or higher from a feedstock having an API gravity of 24.0° or less. The plurality of fractions can include at least a distillate fraction and a bottoms fraction having a first kinematic viscosity at 100°C. The plurality of fractions can have a first weight ratio of the distillate fraction to the bottoms fraction. Additionally, the method can include blending at least a portion of the distillate fraction with at least a portion of the bottoms fraction to form a product asphalt fraction having a product kinematic viscosity at 100°C that is lower than the first kinematic viscosity at 100°C. A weight ratio of the at least a portion of the distillate fraction to the at least a portion of the bottoms fraction can be higher than the first weight ratio.

[0007] In some aspects, the product asphalt fraction can have a product kinematic viscosity at 100°C of 700 cSt to 1200 cSt and/or a kinematic viscosity at 135°C of 135 cSt to 165 cSt. In some aspects, the product kinematic viscosity at 100°C can be lower than the first kinematic viscosity at 100°C by 500 cSt or more. Additionally or alternately, the product asphalt fraction can have a flash point of 270°C or higher, or 302°C or higher. In some aspects, the bottoms fraction can have a first kinematic viscosity of 5000 cSt or higher.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 shows a relationship between kinematic viscosity and flash point for asphalt products formed by distillation of various crude oils.

[0009] FIG. 2 shows kinematic viscosity versus atmospheric equivalent distillation temperature for asphalt fractions formed from crude oils having various API gravity values. [0010] FIG. 3 shows flash point versus kinematic viscosity for asphalt fractions formed from crude oils having various API gravity values.

[0011] FIG. 4 shows an example of a process flow for forming an asphalt fraction. DETAILED DESCRIPTION

[0012] All numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

Overview

[0013] In various aspects, systems and methods are provided for forming soft asphalt compositions with improved properties that are derived from distillation of a crude oil (or mixture of crude oils) having an API gravity of 24° or less. In order to form a target asphalt composition from a feedstock having an API gravity of 24° or less, a distillation is performed where at least two fractions are generated that have a T10 distillation point of 430°C or more. A first fraction can correspond to a distillate fraction having a T10 distillation point of 430°C or more. A second fraction can correspond to a bottoms fraction. Optionally, other fractions with a boiling range between the first fraction and second fraction could also be generated. After generating at least two fractions with a T10 distillation point of 430°C or more, disproportionate blending can be used to combine a portion of the first fraction with a portion of the second fraction. By using disproportionate blending of a distillate fraction and a bottoms fraction, an asphalt product fraction can be formed that has both a flash point of 270°C or more and a KV100 between roughly 700 cSt and 1200 cSt. In some aspects, this asphalt product fraction can correspond to an asphalt having a performance grade of 46-XX, although performance grades such as 40-XX, 52-XX, or even 58-XX could also be produced. In some aspects, using disproportionate blending to form the asphalt product fraction can result in consuming all of the first (distillate) fraction while using only a portion of the second (bottoms) fraction. This remainder portion of the bottoms fraction can be used as a blend stock for formation of other products.

[0014] More generally, distillation followed by disproportionate blending can be used to form various softer grades of asphalt from heavy feedstocks while unexpectedly providing improved volatility properties, such as a flash point of 270°C or more (or 302°C or more), or a rolling thin film oven weight loss of less than 1.0 wt%. In particular, the method described herein can allow for formation of soft grades of asphalt (between 46-XX and 58-XX) from crude oils having an API gravity of 24° or less while providing unexpectedly high flash point and/or unexpectedly low volatility.

[0015] It is noted that generally, the lower the API of a crude oil, the lower the atmospheric equivalent distillation temperature needs to be in order to form an asphalt of a specified viscosity. As a result, for a given target viscosity range, an asphalt generated from a heavier crude oil typically includes a relatively higher proportion of lighter / lower boiling point oils than a similar performance grade asphalt generated from a lighter crude oil. When attempting to form a softer grade of asphalt (58-XX or less) from a crude oil with an API gravity of 24° or less, the additional lower boiling point compounds included in the asphalt result in a reduced flash point and/or a higher volatility. As a result, even though an asphalt of a desired kinematic viscosity and/or performance grade is achieved, the asphalt may not be able to meet the limits of industry specifications and/or regulatory requirements for a desired roofing or paving application.

[0016] As a demonstration of the problem of satisfying both a flash point specification and a kinematic viscosity specification for an asphalt fraction, FIG. 1 shows data from distillation of feeds (such as crude oils or mixtures of crude oils) having various API gravity values. The data points in FIG. 1 correspond to asphalt product fractions formed by distillation that have KV100 values of either 800 cSt and 1500°C. The flash point of the resulting asphalt product fractions is shown on the vertical axis, while the horizontal axis shows the API gravity of the feed for distillation. The circle data points show asphalt product fractions with a KV100 of 800 cSt. The triangle data points show asphalt product fractions with a KV100 of 1500 cSt. Line 110 corresponds to a flash point of 302°C, which is the flash point requirement according to ASTM D312 for forming a roofing asphalt product. The lines 101 and 102 in FIG. 1 correspond to least squares fit lines of the 800 cSt data (line 101) and the 1500 cSt data (line 102).

[0017] As shown in FIG. 1, there is a large variability the flash point values of a soft asphalt fraction for a given API gravity in the original feed. However, it is clear from FIG. 1 that for API gravity values of 24.0 or less, a substantial portion of the soft asphalt fractions having KV100 values of either 800 cSt or at 1500 cSt have flash points of less than 302°C. For heavier feeds, it is noted that only one feed with an API gravity of less than 24.0 was able to form an asphalt fraction having both a KV100 of 800 cSt and a flash point of 302°C or more. No feed with an API gravity of less than 19 resulted in an asphalt fraction with both a KV100 of 800 cSt and a flash point of 302°C or more. Similarly, only a few feeds with an API gravity of less than 24.0 (and no feeds with an API gravity of 17 or less) were able to produce asphalt fractions having both a KV100 of 1500 cSt and a flash point of 302°C or more.

[0018] The data in FIG. 1 illustrates the difficulty of attempting to form asphalt products (such as roofing asphalt flux) directly from feeds with an API gravity of 24.0° or less, or 22.0° or less, or 19.0° or less, or 17.0° or less (such as down to 0° or possibly still lower). For most feeds, performing a distillation to form an asphalt product with a target KV100 between 800 cSt and 1500 cSt results in an asphalt product fraction is either at the edge of a target flash point specification or below the target flash point specification. Unfortunately, forming roofing asphalt products from such heavier feeds is desirable, as the resulting asphalt derived from such heavier feeds can provide asphalt products with improved performance characteristics.

[0019] It is noted that asphalt specifications and/or regulations can vary on a country-to- country basis. The flash point target value of 302°C represents a U.S. specification. In Canada, the minimum flash point is 270°C. However, FIG. 1 shows that the same types of difficulties are still present. As shown in FIG. 1, various starting feedstocks with an API gravity of 24° or less were not able to directly form asphalt fractions by distillation that had a KV100 between 800 cSt and 1500 cSt while also having a flash point of 270°C or higher. [0020] As shown in FIG. 1, various types of heavy feeds cannot be used to directly form asphalt products by distillation that have both target performance properties (such as KV100 and/or a target PG grade) and target volatility properties (flash point and/or rolling thin film oven mass loss). Conventionally, to achieve such a target combination of properties for a product asphalt fraction when starting with such a crude oil, the initial crude (or mixture of crudes) would be combined with additional vacuum gas oil from a separate source, such as according to the method described in U.S. Patent 6,258,255. The combined crude oil / vacuum gas oil mixture would then be distilled to form the target grade of asphalt. While this can be effective, this requires a substantial downgrade in value for the vacuum gas oil fraction that is added to the combined crude oil, as vacuum gas oils can typically be used to form higher value products than asphalts.

[0021] In various aspects, the difficulties in using low API gravity feedstocks to form asphalt product fractions with desirable combinations of kinematic viscosity and flash point (and/or other volatility-based properties) can be overcome by using distillation followed by disproportionate blending to form the asphalt product fractions. The combination of distillation and disproportionate blending can allow an asphalt fraction with target properties to be formed from a feedstock while reducing, minimizing, or eliminating the need to blend fractions derived from other feeds into the feedstock for distillation. This can allow heavy crude oils (or blends of heavy crude oils), which provide asphalt products with desirable performance properties, to be used to directly form soft asphalt products (i.e., without blending of vacuum gas oil from other sources) while still satisfying volatility specifications. [0022] It is noted that only a limited portion of the bottoms fraction generated during distillation can be blended with the at least one vacuum distillate fraction while still forming a softer grade of asphalt. Thus, in addition to forming the softer grade of asphalt (performance grade 40-XX to 58-XX, or 46-XX to 58-XX), a remaining portion of a harder grade of asphalt (at least 64-XX, or at least 70-XX) is also generated. This remaining portion of the harder grade of asphalt can be used for any convenient or typical use for a vacuum resid fraction / hard asphalt grade fraction.

Performance Grade Characterization

[0023] One way of characterizing an asphalt composition is by using SUPERPAVE™ criteria. SUPERPAVE™ criteria (as described in the June 1996 edition of the AASHTO Provisional Standards Book and 2003 revised version) can be used to define the Maximum and Minimum Pavement service temperature conditions under which the binder must perform. SUPERPAVE™ is a trademark of the Strategic Highway Research Program (SHRP) and is the term used for new binder specifications as per AASHTO MP-1 standard. Maximum Pavement Temperature (or "application" or "service" temperature) is the temperature at which the asphalt binder will resist rutting (also called Rutting Temperature). Minimum Pavement Temperature is the temperature at which the binder will resist cracking. Low temperature properties of asphalt binders were measured by Bending Beam Rheometer (BBR). According to SUPERPAVE™ criteria, the temperature at which a maximum creep stiffness (S) of 300 MPa at 60s loading time is reached, is the Limiting Stiffness Temperature (LST). Minimum Pavement Temperature at which the binder will resist cracking (also called Cracking Temperature) is equal to LST-10°C.

[0024] The SUPERPAVE™ binder specifications for asphalt paving binder performance establishes the high temperature and low temperature stiffness properties of an asphalt. The nomenclature is PG XX- YY which stands for Performance Grade at high temperatures (HT), XX, and at low temperatures (LT), -YY degrees C, wherein -YY means a temperature of minus YY degrees C. Asphalt must resist high summer temperature deformation at temperatures of XX degrees C and low winter temperature cracking at temperatures of -YY degrees C. An example popular grade in Canada is PG 58-28. Each grade of higher or lower temperature differs by 6°C in both HT and LT. This was established because the stiffness of asphalt doubles about every 6°C. One can plot the performance of asphalt on a SUPERPAVE™ matrix grid. The vertical axis represents increasing high PG temperature stiffness and the horizontal axis represents decreasing low temperature stiffness towards the left. Directionally poorer asphalt performance is to the lower right. Target exceptional asphalt or enhanced, modified asphalt performance is to the upper left, most preferably in both the HT and LT performance directions.

[0025] Although asphalt falls within a PG box that allows it to be considered as meeting a given PG grade, the asphalt may not be robust enough in terms of statistical quality control to guarantee the PG quality due to variation in the PG tests. This type of property variation is recognized by the asphalt industry as being as high at approximately +/-3°C. Thus, if an asphalt producer wants to consistently manufacture a given grade of asphalt, such PG 64-28, the asphalt producer must ensure that the PG tests well within the box and not in the right lower comer of the box.

[0026] In this discussion, performance grade, high temperature performance grade, and low temperature performance grade can be determined according to AASHTO R29.

[0027] In this discussion, a high temperature performance grade or a low temperature performance grade may be referred to using the notation “PGNN”, where NN is the high temperature / low temperature performance grade. Alternatively, when specifying a high temperature performance grade, the notation “NN-XX” may be used, where NN is the high temperature performance grade, and XX is a placeholder indicating that a low temperature performance grade is not specified (i.e., can be any convenient value). When referring to a high temperature performance grade using the notation “NN-XX”, the high temperature performance grade may be expressed as a range. For example, the phrases “at least 64-XX” or “64-XX or greater” specify a high temperature performance grade of PG64 or higher (e.g., PG64, PG70, PG76, PG82, PG88), without requiring any specific value for the low temperature performance grade. Similarly, the phrase “58-XX or less” or “PG 58-XX or less” specifies a high temperature performance grade of PG58 or less (e.g., PG 58, PG 52, PG46) without requiring any specific value for the low temperature performance grade.

Definitions and Testing Procedures

[0028] In this discussion, distillation points can be determined according to ASTM D2887. For fractions (such as crude oils or vacuum residues) where ASTM D2887 is not suitable, ASTM D7169 can be used. It is noted that such distillation points refer to atmospheric equivalent distillation points. As understood by those of skill in the art, distillation points of roughly 350°C or higher refer to distillation points that are typically achieved by performing distillation at a pressure lower than 100 kPa-a, so that the oil in a distillation stage is not exposed to temperatures greater than roughly 350°C.

[0029] In this discussion, API gravity can be determined according to ASTM D1298. Penetration at 25°C is determined according to ASTM D5. Density at 15°C is determined according to ASTM D70. Softening point (stir or no stir) is determined according to ASTM D36. The content of n-heptane insolubles (NHI) is determined according to ASTM D3279. [0030] In this discussion, flash point is determined according to AASHTO T48. Mass loss during a rolling thin-film oven (RTFO) test is determined according to AASHTO T240. Kinematic viscosities (various temperatures) are determined according to ASTM D2170. AASHTO T315 is used for the various rheological parameters that are determined using a Dynamic Shear Rheometer.

[0031] In this discussion, a Txx distillation point refers to the portion “xx” of a fraction can be distilled off at the corresponding temperature. Thus, a T10 distillation point of 370°C means that 10 wt% of a sample can be distilled off at 370°C.

[0032] In this discussion, some fractional weight distillation values are provided as open- ended ranges. For example, some fractions may be referred to as fractions with a T90 distillation point of 525°C or higher, or 538°C or higher, or 566°C or higher. In such aspects, if an upper end of a range is required for an open-ended fractional distillation point range (such as a T90 distillation point), the upper end corresponds to the maximum boiling point value that can be determined, or alternatively can be specified as 750°C. (In other words, if an upper end of a range is required for the exemplary T90 distillation points mentioned here, the T90 distillation point can be treated as having a range of 525°C to 750°C, or 538°C to 750°C, or 566°C to 750°C). As another example, some fractions may be specified as having a “Txx” fractional distillation point that is less than a temperature, such as having a T50 value of 460°C or less. In such aspects, if a lower end of a range is required for a Txx point that is specified as an open-ended range, the value 0°C can be used as a lower end for the range, such as having a T50 value of 0°C to 460°C. It is noted that this paragraph does not apply to fractional distillation point ranges where both a top and a bottom of a range are specified. Distillation of Feedstock to Form a Plurality of High Boiling Fractions

[0033] The feed for distillation to form the asphalt product can correspond to a feed derived from one or more whole crudes, partial crudes, and/or fractions that include 566°C+ components (e.g., vacuum bottoms) that have an initial API gravity of 24.0° or less, or 22.0° or less, or 19.0° or less, or 17.0° or less, such as down to 0° or possibly still lower. In aspects where a plurality of whole crudes, partial crudes, and/or other fractions are included in the feed, the feed can alternatively be referred to as a feed blend. In some aspects, the feed for distillation can have a T10 distillation point of 460°C or less, or 440°C or less, such as down to any convenient T10 distillation point. (As a practical matter, the T10 distillation point can be at least 25°C.) In some aspects, the feed can have an initial boiling point of 302°C or less, or 270°C or less, such as down to 25°C.

[0034] In some aspects where the feed represents a feed blend derived from a plurality of sources, the API gravities of the individual components in the feed blend are not critical, so long as the feed blend has an API gravity of 24.0° or less. Preferably, the blend components in the feed blend can substantially correspond to blend components that include vacuum resid (566°C+) boiling range portions. In some aspects, 6.0 wt% or less (such as down to 0%) of the blend components in the feed blend can have an n-heptane insolubles content of less than 0.1 wt% (i.e., substantially no n-heptane insolubles content). It is noted that conventional distillate fractions typically have less than 0.1 wt% of n-heptane insolubles. Additionally or alternately, in some aspects 6.0 wt% or less (such as down to 0%) of the blend components in the feed blend can have a T50 distillation point of 460°C or less, or 475°C or less, or 490°C or less. Further additionally or alternately, in some aspects, 6.0 wt% or less (such as down to 0%) of the blend components in the feed blend can correspond to blend components that have a T90 distillation point of 538°C or less.

[0035] A vacuum distillation can then be performed on the feed to form at least two fractions that have a T10 distillation point of 430°C or higher. A first fraction can correspond to a vacuum distillate fraction. The vacuum distillate fraction can have a T10 distillation point of 430°C or higher (such as up to 500°C) and a T90 distillation point of 595°C or less, or 565°C or less, or 550°C or less, or 530°C or less, or 510°C or less (such as down to 460°C). A second fraction can correspond to a bottoms fraction. The bottoms fraction can have any convenient T10 distillation point, so long as the T10 distillation point is higher than the T10 distillation point of the distillate fraction. In some aspects, the bottoms fraction can have a kinematic viscosity at 100°C (KV100) of 1200 cSt or higher, or 2500 cSt or higher, or 5000 cSt or higher, such as up to 100,000 cSt or possibly still higher. Additionally or alternately, the bottoms fraction can have a performance grade of 58-XX or higher, or 64-XX or higher, or 70-XX or higher, such as up to 88-XX or possibly still higher.

[0036] It is noted that the vacuum distillation is described herein as being performed in a single vacuum distillation tower system. If desired, a plurality of towers could be used to form the distillate fraction and the bottoms fraction. For example, a first vacuum distillation tower could be used to form a single (bottoms) fraction with a T10 distillation point of 430°C or higher. This single fraction can then be distilled in a second distillation tower to form the distillate fraction and the bottoms fraction that are used for the disproportionate blending. Disproportionate Blending to Form Product Asphalt Fraction [0037] After using distillation to form at least two fractions with a T10 distillation point of 430°C or higher, disproportionate blending can be used to form a product asphalt fraction having a target combination of properties. In various aspects, the target combination of properties can include two or more of a target flash point, a target kinematic viscosity at 100°C (KV100), a target performance grade, and a target rolling thin film oven (RTFO) mass loss.

[0038] Theoretically, after forming the at least two fractions (the distillate fraction and the bottoms fraction), one option for blending the fractions would be to blend all of the distillate fraction with all of the bottoms fraction. For example, if the distillation results in formation of a distillate fraction and a bottoms fraction with a weight ratio of 1 : 2, blending the entire distillate fraction with the entire bottoms fraction would result in blending the distillate fraction and bottoms fraction in the same 1 : 2 weight ratio. Thus the weight ratio of the distillate fraction to the bottoms fraction formed by the distillation is substantially the same as the weight ratio of distillate to bottoms in the asphalt product. This type of complete blending of the distillate fraction and the bottoms fraction would re-create the type of asphalt product that would be formed if a single, wider cut bottoms fraction were formed.

[0039] By contrast, using disproportionate blending can allow blends of distillate and bottoms to be formed that are different than the weight ratio of the distillate fraction to the bottoms fraction. In particular, if the distillate fraction and bottoms fraction are present in a first weight ratio, disproportionate blending can be used to form an asphalt product having a second, higher weight ratio of distillate to bottoms. By using a higher proportion of the distillate fraction, a softer grade / lower viscosity asphalt product can be formed relative to the product that would be formed by complete or proportionate blending. In some aspects, the entirety of the distillate fraction can be used in the disproportionate blending. In other aspects, disproportionate blending can be used even though only a portion of the distillate is included in the asphalt product. In either event, the ratio of distillate to bottoms in the asphalt product can be higher than the weight ratio of the distillate fraction to the bottoms fraction. [0040] It is noted that if more than two products are formed that have a T10 distillation point of 430°C or higher, then the disproportionate blending can be performed using two or more distillate fractions. In such an aspect, disproportionate blending is performed so long as the weight ratio of at least one distillate fraction versus the bottoms fraction in the resulting asphalt product is higher than the weight ratio of the at least one distillate fraction versus the bottoms fraction as formed after the distillation. [0041] The disproportionate blending can be used to form an asphalt product with a reduced viscosity and/or a lower performance grade. In some aspects, the asphalt product can have a KV100 that is lower than the KV100 of the bottoms fraction by 100 cSt or more, or 500 cSt or more, or 1000 cSt or more, or 2500 cSt or more, such as up to 60,000 cSt or possibly still higher.

[0042] In some aspects, the asphalt product can have a KV100 of 700 cSt to 1200 cSt, or 700 cSt to 1000 cSt, or 800 cSt to 1200 cSt, or 800 cSt to 1000 cSt. Additionally or alternately, the asphalt product can have a kinematic viscosity at 135°C of 135 cSt to 165 cSt. Further additionally or alternately, the asphalt product can have a performance grade between 46-XX and 64-XX, or between 46-XX and 58-XX, or between 46-XX and 52-XX. As examples, an asphalt product can correspond to an asphalt fraction having a performance grade of 46-22, 46-28, 46-34, 52-22, 52-28, 52-34, 58-22, 58-28, and/or 58-34. Still further additionally or alternately, the asphalt product can have a flash point of 270°C or more, or 285°C or more, or 302°C or more, such as up to 500°C or possibly still higher. Yet further additionally or alternately, the asphalt product can have an RTFO mass loss (ASTM D2872) of 1.0 wt% or less, or 0.7 wt% or less, or 0.4 wt% or less, such as down to 0.01 wt% or possibly still lower. In some aspects, a product asphalt fraction can have a penetration at 25°C of 300 dmm to 750 dmm. In some aspects, a product asphalt fraction can have a softening point of 20°C to 40°C.

[0043] In some aspects, the asphalt product can correspond to an asphalt product for use in roofing material applications, such as use as a roofing asphalt flux. In other aspects, the asphalt product can correspond to an asphalt product for use in paving material applications. [0044] Due to the disproportionate blending, at least a portion of the bottoms product is left over as a remaining portion of the bottoms product after formation of the asphalt product. In various aspects, 90 wt% or less of the bottoms product can be incorporated into the asphalt product, or 80 wt% or less, or 65 wt% or less, or 50 wt% or less, or 35 wt% or less, such as down to 10 wt% or possibly still lower. As a result, the remaining portion of the bottoms product can correspond to 10 wt% or more of the bottoms product, or 20 wt% or more, or 35 wt% or more, or 50 wt% or more, or 65 wt% or more, such as up to 90 wt% or possibly still higher.

[0045] FIG. 4 provides a graphical illustration of using vacuum distillation to form at least a vacuum distillate product and a bottoms fraction, and then subsequently using disproportionate blending to form a product asphalt. In FIG. 4, the total volume of the vacuum distillate plus asphalt is represented by box 410. In the example shown in FIG. 4, if all of box 410 was distilled as a single product (i.e., if all of box 410 corresponded to the bottoms product), the resulting single product would have a performance grade of PG64 or higher. Instead of forming a single bottoms product, vacuum distillation 415 is used to form one or more distillate portions 420 and at least one bottoms product 430. In the example shown in FIG. 4, the bottoms product 430 can have a performance grade of PG70 or higher. The bottoms product 430 can then be divided into a first bottoms portion 432 that will be used for the disproportionate blending with distillate portion(s) 420 and a remaining portion 434 that can be used in another convenient manner. In the example shown in FIG. 4, the first bottoms portion 432 can then be blended with distillate portion(s) 420 to form a product asphalt (or asphalts) 440 that have a performance grade of PG46 to PG58.

Further Processing of Asphalt Fraction

[0046] In addition to properties of the asphalt fraction, properties of the product asphalt fraction after being exposed to an oxidation process can be characterized. Prior to use in applications such as use as a roofing asphalt or roofing asphalt flux, an asphalt fraction can be exposed to oxidation conditions, such as air blowing conditions. Air blowing of an asphalt composition can be performed in any convenient manner. Optionally, a catalyst can be added to the asphalt composition to facilitate oxidation. More generally, any convenient method of oxidation can be used, such as oxidation with an oxidizing agent different from oxygen. When air blowing is used, the air blowing can be performed by bubbling air (or another gas flow containing oxygen) through the asphalt composition at a temperature of 150°C to 280°C for a sufficient time to achieve a target softening point. This can correspond to a time between 10 minutes and 10 hours, or between 10 minutes and 6 hours.

[0047] After exposure to such oxidation conditions, an oxidized product asphalt fraction can have a penetration at 25°C of between 5 dmm and 20 dmm while also having a softening point between 90°C and 110°C. Additionally or alternately, after exposure to oxidation conditions, an oxidized product asphalt fraction can have an increased weather resistance, as determined by the oxidized product asphalt fraction lasting for an increased number of cycles when exposed to cyclic conditions in accordance with ASTM D4798.

Disposition of Remaining Portion of Products Derived from Baseline Asphalt [0048] In various aspects, after performing the separation and subsequent disproportionate blending steps to form the asphalt product, one or more remaining portions of the bottoms fraction can be left over. The remaining portion(s) of the bottoms can be used as blend components for blending with streams derived from other sources to make additional products. [0049] As an example, one option for blending the remaining bottoms portion with other streams can be implemented in situations where a refinery has two or more vacuum distillation towers. In this example, the available crude oil feedstock has an API gravity of less than 24.0°.

[0050] In this example, a first portion of the feedstock is sent to the first vacuum distillation tower and a second portion is sent to the second vacuum distillation tower. The first distillation tower can be operated to form a plurality of products with a T10 distillation point of 430°C or higher, so that at least a distillate product and a bottoms product is formed. The second distillation tower can be operated to form only a single (bottoms) product. This single bottoms product can have any convenient cut point for forming an asphalt / bottoms product. In some aspects, the single bottoms product can have a T10 distillation point of 375°C or more, or 400°C or more, or 430°C or more, such as up to 538°C or possibly still higher.

[0051] After distillation, the products from the first distillation tower can undergo disproportionate blending to form (for example) a 46-XX asphalt product and a remaining bottoms product with (for example) a performance grade of PG70 or higher. Continuing with the example, for the second tower, because only a single bottoms product that includes the 430°C+ material, the bottoms from the second tower can correspond to a softer asphalt, such as a PG 52-XX asphalt or a PG 58-XX asphalt. The remaining bottoms product from the first tower can then be blended with at least a portion of the bottoms from the second tower to form an additional asphalt product. The performance grade of this additional asphalt product may be harder relative to PG 52-XX or PG 58-XX, due to the inclusion of the PG70 material. In some aspects, the remaining bottoms from the first tower can be blended with the entire bottoms from the second tower, in order to dilute the PG70 material as much as possible. In other aspects, only a portion of the PG 52-XX or PG 58-XX material may be blended with the remaining bottoms portion from the first tower, in order to preserve as much of the PG 52-XX or PG 58-XX material as possible while still forming an additional asphalt product that has commercial value. The exact blending options for using the remaining bottoms product from the first tower and/or for forming the additional asphalt product can vary depending on the nature of the initial crude.

[0052] As a further extension of this example, in some aspects, one or more products generated by blending in the remaining bottoms product with the single bottoms product from the second tower can be used as paving asphalts. Paving asphalts can generally have lower flash point requirements, such as a flash point of 230°C or higher. This can be met performing a conventional distillation to make a single bottoms product that includes the 430°C+ material. The remaining bottoms portion from the first tower can then be blended into the single bottoms product from the second tower in appropriate proportions to form asphalt products that satisfy one or more requirements for use as a paving asphalt.

[0053] In still another example, when multiple distillation towers are available, the second tower can be used to distill a feedstock that is different from the feedstock that is used for forming the asphalt product. The use of a different feedstock in the second tower can potentially change the type of blends that would be formed using the remaining portion of the bottoms from the first tower, but the overall strategy is similar. In still other aspects, if more than two distillation towers are available, any convenient number of towers can be used for forming an asphalt product via disproportionate blending, while any convenient number of additional towers can be used for performing other distillations, so that the remaining bottoms portions from the towers used for disproportionate blending can be blended into any convenient number of products from the other distillation towers.

Example 1 - Formation of PG46 Asphalt from Oil Sands Bitumen

[0054] An oil sands bitumen was used as a crude oil for forming a PG46 asphalt fraction. The oil sands bitumen had an API gravity of roughlyl0.6°. A PG 46-XX asphalt fraction can be beneficial for forming roofing asphalt flux if the flash point, mass loss, and roofing material properties are also suitable.

[0055] In this example, a PG 46 asphalt was formed from the oil sands bitumen using three different processes. In a first process, a distillation was performed on the crude oil to directly make a PG46 asphalt. Creating a PG 46 asphalt directly from the crude oil corresponded to using a roughly 385°C cut point for forming the asphalt.

[0056] In the second process, the oil sands bitumen was distilled to form a 452°C to 475°C distillate fraction and a bottoms fraction. Relative to the combined weight of the distillate fraction and the bottoms fraction (i.e., a combined weight of the 452°C+ fractions), the distillate fraction corresponded to 4 wt% of the combined weight while the bottoms corresponded to the remaining 96 wt%. The bottoms fraction corresponded to a PG70 asphalt. The 4 wt% of distillate (relative to the combined weight of the 452°C+ fractions) was then blended in a 30 / 70 weight ratio with a portion of the PG70 asphalt to form the product PG46 asphalt. Based on this blending, the final product slate corresponded to 15 wt% of the PG46 asphalt and 85 wt% of the PG70 asphalt (relative to the combined weight of the 452°C+ fractions). [0057] In the third process, the oil sands bitumen was distilled to form a 452°C to 528°C distillate fraction and a bottoms fraction. Relative to the combined weight of the distillate fraction and the bottoms (i.e., a combined weight of the 452°C+ fractions), the distillate fraction corresponded to 25 wt% of the combined weight while the bottoms corresponded to 75 wt% of the combined weight. The bottoms corresponded to a PG88 asphalt. The 25 wt% of distillate (relative to the weight of the 452°C+ fractions)) was then blended in a 43 / 57 weight ratio (or alternatively 3 / 4) with a portion of the PG88 asphalt to form the product PG46 asphalt. Based on this blending, the final product slate derived from the baseline asphalt corresponded to 61 wt% of the PG46 asphalt and 39 wt% of the PG88 asphalt (relative to the combined weight of the 452°C+ fractions).

[0058] Table 1 shows results from characterization of the PG46 asphalts made by the three processes.

Table 1 - Properties of PG46 Asphalts

[0059] As shown in Table 1, forming a PG46 asphalt directly from the oil sand bitumen resulted in formation of a PG 46-28 asphalt. However, the flash point of this asphalt was only 256°C, and therefore less than the 270°C flash point that is a regulatory standard for some applications. Additionally, the mass loss from this asphalt in an RTFO test was -2.231 wt%, which is substantially greater than the 1.0 wt% that is a regulatory standard for some applications.

[0060] By contrast, both of the PG46 asphalts formed using disproportionate blending resulted in asphalts with higher flash points and low mass loss. Process 2 resulted in an asphalt with a flash point of 293°C and a mass loss of 0.17 wt% in the RTFO test. This represents a desirable asphalt for use as a roofing asphalt flux for forming roofing materials. Process 3 resulted in an asphalt with a flash point of 288°C and a mass loss of 0.29 wt% in the RTFO test. This also represents a desirable asphalt for forming roofing materials. It is noted that the asphalt from Process 2 corresponded to a PG 46-28 asphalt, while the asphalt from Process 3 is simply reported as PG 46-XX.

[0061] Although Process 2 resulted in a PG46 asphalt with improved properties (higher flash point, lower mass loss), the yield of PG46 asphalt from Process 2 was also rather low, corresponding to only 15 wt% of the combined weight of 452°C+ distillate and bottoms. Process 3 provided a substantially higher yield of PG46 asphalt, corresponding to 59 wt% of the baseline asphalt. However, the remaining asphalt portion generated by Process 3 corresponded to a PG88 asphalt. This is a relatively hard grade of asphalt that can be somewhat more difficult to incorporate into a product. By contrast, the remaining asphalt from Process 2 corresponded to a PG70 asphalt, which can more easily be incorporated into various applications.

Example 2 - Example of Operation with Two Distillation Towers

[0062] Two vacuum distillation towers were used for distillation of an oil sands bitumen. The first distillation tower was operated to generate two products: a 445°C - 543°C distillate fraction and a 543 °C+ resid. The 543 °C+ resid corresponded to an asphalt with a performance grade of PG70 or higher. The second tower was operated to generate a 405°C+ resid fraction, which corresponded to a PG 52-34 asphalt.

[0063] After distillation, the distillate and bottoms from the first tower were disproportionately blended in a 40 : 60 weight ratio to form a PG 46-34 asphalt. This product satisfied specifications for making a roofing asphalt flux, including having a flash point of 285°C (greater than 270°C) and an RTFO mass loss of 0.2 wt% (less than 1.0 wt%).

[0064] Forming the PG 46-34 asphalt resulted in a remaining portion of the first tower bottoms being left over. The remaining portion of the first tower bottoms was blended with the PG 52-34 asphalt from the second tower to make two different products: a PG 58-28 asphalt product and a PG 64-22 asphalt product. The PG 58-28 product was formed by blending the remaining portion of the first tower bottoms and second tower bottoms in a roughly 12 : 88 weight ratio. The PG 64-22 product was formed by blending the remaining portion of the first tower bottoms and second tower bottoms in a roughly 28 : 72 weight ratio. This allowed all of the remaining portion of the first tower bottoms to be incorporated into asphalt products.

Example 3 - Relationship Between API Gravity and Distillation Point

[0065] FIG. 2 shows a plot of kinematic viscosity (logarithmic scale) versus atmospheric equivalent distillation temperature for a variety of crude oils having different API gravity values. The kinematic viscosity of an asphalt fraction roughly correlates with the performance grade for the asphalt, so FIG. 2 can be understood to show the relationship between performance grade and distillation temperature, based on the API gravity of a crude oil. In FIG. 2, Crude 1 has an API gravity of roughly 22°. Crude 2 corresponds to a blend of crude oils, including 60 wt% of Crude 1. The combined API gravity of Crude 2 is roughly 25. Crude 3 had an API gravity of roughly 27°. Crudes 4 and 5 had API gravity values of roughly 33. Crude 6 had an API gravity value of roughly 39.

[0066] As shown in FIG. 2, at API gravity values greater than 30°, the correlation between API gravity and the distillation point for achieving a target viscosity for an asphalt fraction is not strong. However, as the API gravity value is reduced, the lower the API gravity value, the lower the temperature that is required to form an asphalt fraction with a target viscosity. This is particularly true for Crude 1, which has a substantially lower kinematic viscosity than the other crude oils in FIG. 2.

[0067] Based on the data shown in FIG. 2, when a crude oil is distilled to form a target kinematic viscosity and/or performance grade, the target kinematic viscosity / performance grade can be achieved for a heavier crude oil (i.e., lower API gravity) at a lower distillation temperature. As a result, an asphalt formed from a heavier crude oil can have a higher percentage of lower boiling components than a comparable asphalt formed from a lighter crude oil. One way of illustrating this increased content of lower boiling components can be based on the flash point of the resulting asphalts.

[0068] FIG. 3 shows a plot of flash point versus kinematic viscosity (logarithmic scale) for the crude oils shown in FIG. 2. Similar to FIG. 2, the correlation between flash point, API gravity, and kinematic viscosity is not as strong for the higher API gravity crude oils. But the asphalts formed from the heaviest crude oil (Crude 1) have substantially lower flash points than the asphalts formed from the other crude oils.

Additional Embodiments

[0069] Embodiment 1. A method for forming an asphalt fraction, comprising: separating a plurality of fractions having a T10 distillation point of 430°C or higher from a feedstock having an API gravity of 24.0° or less, the plurality of fractions comprising at least a distillate fraction and a bottoms fraction having a first kinematic viscosity at 100°C, the plurality of fractions comprising a first weight ratio of the distillate fraction to the bottoms fraction; and blending at least a portion of the distillate fraction with at least a portion of the bottoms fraction to form a product asphalt fraction having a product kinematic viscosity at 100°C that is lower than the first kinematic viscosity at 100°C, a weight ratio of the at least a portion of the distillate fraction to the at least a portion of the bottoms fraction being higher than the first weight ratio.

[0070] Embodiment 2. The method of Embodiment 1, wherein the product asphalt fraction comprises a product kinematic viscosity at 100°C of 700 cSt to 1200 cSt, or wherein the product asphalt fraction comprises a kinematic viscosity at 135°C of 135 cSt to 165 cSt, or a combination thereof.

[0071] Embodiment 3. The method of any of the above embodiments, wherein the product kinematic viscosity at 100°C is lower than the first kinematic viscosity at 100°C by 500 cSt or more, or wherein the bottoms fraction comprises a first kinematic viscosity of 5000 cSt or higher, or a combination thereof.

[0072] Embodiment 4. The method of any of the above embodiments, wherein the product asphalt fraction comprises a flash point of 270°C or higher, a mass loss during a rolling thin film oven test of 1.0 wt% or less, or a combination thereof.

[0073] Embodiment 5. The method of any of the above embodiments, wherein the product asphalt fraction comprises a flash point of 302°C or higher.

[0074] Embodiment 6. The method of any of the above embodiments, wherein the product asphalt fraction comprises 10 wt% to 90 wt% of a combined weight of the distillate fraction and the bottoms fraction.

[0075] Embodiment 7. The method of any of the above embodiments, wherein the feedstock comprises an API gravity of 19.0° or less.

[0076] Embodiment 8. The method of any of the above embodiments, wherein the distillate fraction comprises a T90 distillation point of 550°C or less.

[0077] Embodiment 9. The method of any of the above embodiments, wherein the product asphalt fraction comprises a performance grade of 40-XX to 52-XX, or wherein the product asphalt fraction comprises a performance grade of 46-XX.

[0078] Embodiment 10. The method of any of the above embodiments, wherein the product asphalt fraction comprises a penetration at 25°C of 300 dmm to 750 dmm, a softening point of 20°C to 40°C, or a combination thereof.

[0079] Embodiment 11. The method of any of the above embodiments, wherein the bottoms fraction comprises a performance grade of PG70 or higher.

[0080] Embodiment 12. The method of any of the above embodiments, wherein the product asphalt fraction comprises substantially all of the distillate fraction.

[0081] Embodiment 13. The method of any of the above embodiments, further comprising separating the bottoms fraction to form the at least a portion of the bottoms fraction and a remaining portion of the bottoms fraction, the remaining portion of the bottoms fraction comprising 40 wt% or more of a weight of the bottoms fraction. [0082] Embodiment 14. The method of Embodiment 13, further comprising blending at least a portion of the remaining portion of the bottoms fraction with a second bottoms fraction formed by distillation of a second feedstock.

[0083] Embodiment 15. An asphalt product formed according to the method of any of Embodiments 1 - 14.

[0084] Additional Embodiment A. The method of any of Embodiments 1 - 3 or 6 - 15, wherein the product asphalt fraction comprises a flash point of 280°C or higher, a mass loss during a rolling thin film oven test of 0.5 wt% or less, or a combination thereof.

[0085] Additional Embodiment B. The method of Embodiment 11, wherein the bottoms fraction comprises a performance grade of PG76 or higher.

[0086] While the present invention has been described and illustrated by reference to particular embodiments, those of ordinary skill in the art will appreciate that the invention lends itself to variations not necessarily illustrated herein. For this reason, then, reference should be made solely to the appended claims for purposes of determining the true scope of the present invention.