Transportable bitumen blends having a seperable high-octane low vapor pressure fraction

Abstract

Low vapor pressure hydrocarbon blends are provided, comprising miscible and separable hydrocarbon fractions. A high-octane low-boiling point diluent fraction may be combined with a high-boiling point bitumen fraction. In select embodiments, and the blend may have a viscosity of less than about 350 cSt and a density of less than about 940 kg/m.sup.3 over a temperature range of from 7.5° C. to 18.5° C. After transportation, for example by pipeline, the high-octane low-boiling point diluent fraction may be recovered from the blend, and may for example be used as a high-octane gasoline blendstock.

Claims

1. A method of transporting hydrocarbons, comprising: mixing a high-boiling point bitumen with a miscible high-octane low-boiling point hydrocarbon diluent, to form a low vapor pressure hydrocarbon blend comprising a diluent fraction and a bitumen fraction, wherein the blend has a viscosity of less than about 350 cSt and a density of less than about 940 kg/m.sup.3 over a temperature range of from 7.5° C. to 18.5° C., and a Reid vapor pressure (RVP) of less than 65 kPa; transporting the blend by pipeline; and, separating the diluent fraction from the bitumen fraction, wherein the diluent fraction and the bitumen fraction are thermally separable; wherein, the temperature at which 5% of the bitumen fraction distills (BP-bitumen.sub.5 vol %) is higher than the temperature at which 95% of the diluent fraction distills (BP-diluent.sub.95 vol %); the BP-diluent.sub.95 vol % is less than or equal to 220° C.; the separating comprises heating of the blend and distillation of the diluent fraction; at least 95% of the diluent is separated from the bitumen in the step of separation; and the initial boiling point of the bitumen fraction is higher than the final boiling point of the diluent fraction.

2. The method of claim 1, wherein: the diluent separated from the bitumen is a high-octane gasoline blendstock; the diluent separated from the bitumen has an (R+M)/2 octane rating of at least 80; the blend has a RVP of less than 60 kPa; the diluent comprises at least 25% iso-octane or iso-hexane by volume; the blend comprises less than 1% by weight olefins.

3. A method of making a high-octane gasoline blendstock, comprising: providing a high-octane low-boiling point hydrocarbon diluent; mixing the diluent with a high-boiling point bitumen, wherein the diluent is miscible and compatible with the bitumen to form a low vapor pressure hydrocarbon blend comprising a diluent fraction and a bitumen fraction, wherein the blend has a viscosity of less than 350 cSt and a density of less than 940 kg/m.sup.3 over a temperature range of from 7.5° C. to 18.5° C., and a Reid vapor pressure (RVP) of less than 65 kPa; transporting the blend by pipeline; and separating the diluent fraction from the bitumen fraction, wherein, the temperature at which 5% of the bitumen fraction distills (BP-bitumen.sub.5 vol %) is higher than the temperature at which 95% of the diluent fraction distills (BP-diluent.sub.95 vol %); the BP-diluent.sub.95 vol % is less than or equal to 220° C.; the separating comprises heating of the blend and distillation of the diluent fraction; at least 95% of the diluent is separated from the bitumen; and the initial boiling point of the bitumen fraction is higher than the final boiling point of the diluent fraction.

4. The method of claim 3, wherein: the blend has a RVP of less than 60 kPa; the diluent comprises at least 25% iso-octane or iso-hexane by volume; and the blend comprises less than 1% by weight olefins.

5. The method of claim 3, further comprising removing sulfur-containing compounds from the separated diluent fraction.

6. The method of claim 4, further comprising removing sulfur-containing compounds from the separated diluent fraction.

7. The method of claim 2, wherein: the diluent comprises greater than 85% by volume branched-chain alkanes; the bitumen has a viscosity of at least 700,000 cSt at 15° C.; the bitumen has a density of less than or equal to 1,000 kg/m.sup.3 at 15° C.; and the volume fraction of bitumen in the blend is higher than 60%.

8. The method of claim 4, wherein: the diluent comprises greater than 85% by volume branched-chain alkanes; the bitumen has a viscosity of at least 700,000 cSt at 15° C.; the bitumen has a density of less than or equal to 1,000 kg/m.sup.3 at 15° C.; and the volume fraction of bitumen in the blend is higher than 60%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a line graph illustrating the kinematic viscosity (mm.sup.2/s) of an iso-octane based diluent over a range of temperatures.

(2) FIG. 2 is a line graph illustrating the density (g/cc) of an iso-octane based diluent over a range of temperatures.

(3) FIG. 3 is a line graph illustrating the kinematic viscosity (mm.sup.2/s) of a sample of bitumen from the Athabasca oil sands in Northern Alberta, Canada over a range of temperatures.

(4) FIG. 4 is a line graph illustrating the density (g/cc) of a sample of bitumen from the Athabasca oil sands over a range of temperatures.

(5) FIG. 5 is a line graph illustrating the kinematic viscosity (mm.sup.2/s) of an iso-octane based diluent bitumen blend at different concentrations of iso-octane and at different temperatures.

(6) FIG. 6 is a line graph illustrating the distillation curve (temperature vs. mass % recovered) of an iso-octane based diluent/bitumen blend. This curve is obtained by a Simulated Distillation Analysis (ASTM D7169-05, Standard Test Method for Boiling Point Distribution of Samples with Residues Such as Crude Oils and Atmospheric and Vacuum Residues by High Temperature Gas Chromatography, American Society for testing and Materials International (ASTM), West Conshohocken, Pa., 2005) and shows the discontinuity represented by the gap between the two distillation curves. This “5-95” gap, used to quantify the degree of overlap in volatility between adjacent hydrocarbon fractions, is the difference, in degrees C., between the 5% ASTM temperature of a heavy fraction, (i.e. the temperature at which 5% of the heavy fraction has distilled), minus the 95% ASTM temperature of the lighter fraction, (i.e. the temperature at which 95% of the lighter fraction has distilled). This discontinuity is what facilitates the separation (fractionation) of the diluent and the bitumen. In FIG. 6, the 5-95 gap is 150° C.

(7) FIG. 7 is a line graph illustrating the fractionation of an iso-octane based diluent I bitumen blend (Rec=recovered). This figure was obtained by simulating the thermal fractionation of the blend using a standard distillation configuration at atmospheric pressure, comprising a feed preheating train, a feed processing furnace heater, a column with tray, an overhead condenser system, and a stripping steam. The simulation model was developed using commercially available software (UniSim Design R430).

(8) FIG. 8 is a line graph illustrating the results of an iso-octane based diluent/bitumen blend compatibility study. Iso-octane based diluent was blended with bitumen from the Athabasca oil sands in Northern Alberta, Canada at different concentrations and then evaluated for the Solubility Blending Number (S.sub.BN) and Insolubility Number (I.sub.N) using the Oil Compatibility Model by Irwin Wiehe method (see Wiehe & Kennedy, Energy & Fuels, 2000, 14. 56-59) to determine the peptization value or P-Value of the blend. The Oil compatibility Model provides an area of incompatible blends where the S.sub.BN of the blend is lower than the crude I.sub.N or a P-Value (S.sub.BN/I.sub.N) les than or equal to 1. Results of the study are shown, indicating that the incompatibility zone of the Iso-Octane based/bitumen blend was observed above an iso-octane concentration of around 73 vol %.

DETAILED DESCRIPTION OF THE INVENTION

(9) An aspect of the present disclosure involves the separation of a high-octane low vapor pressure diluent from bitumen. In some embodiments, the distinct boiling points of the bitumen and diluent fractions (as discussed with respect to FIG. 6) facilitate a separation that substantially recaptures the diluent with its high octane characteristics, segregated from the bitumen. For example, the initial boiling point (IBP) of the bitumen may be approximately 220° C. to 280° C., the final boiling point (FBP) of an iso octane based diluent is approximately 180° C., and the final boiling point of an alkylate based diluent may be approximately 180° C. to 200° C. In embodiments where it exists, this gap between the FBP of the diluent and the IBP of the bitumen (gap or overlap.sub.5/95=ASTM D86.sub.5 vol % Temp of HeavyCut—ASTM D86.sub.95 vol % Temp of Light Cut) facilitates the separation of the two fractions, reduces cross contamination between the two fractions and maintains the chemical integrity of the diluent especially with respect to octane number (as discussed with respect to FIG. 7).

(10) In alternative embodiments, the separation of the bitumen and diluent fractions of a blend, for example in refinery fractionation units, my involve capturing at least some of the light ends of the bitumen in the reconstituted diluent. This may for example be the case where the bitumen or heavy oil fraction is particularly rich in more volatile components. In embodiments of this kind, with reduced or non-existent gaps between the FBP of the diluent and the IBP of the bitumen, conditions may be selected for separation and treatment of the reconstituted diluent that preserve an elevated octane number, for example being at least greater than 60 or 66 in alternative embodiments. In alternative embodiments, the separation of the bitumen and the diluent fractions of a blend may involve processes in combination with or other than distillation, for example, membrane separation,

(11) The gap between boiling points may be determined empirically, for example using ASTM D86, a basic test method for determining the boiling range of a petroleum product by performing a simple atmospheric batch distillation to determine quantitatively the boiling range (ASTM D86-16a, Standard Test Method for Distillation of Petroleum Products and Liquid Fuels at Atmospheric Pressure, ASTM International, West Conshohocken, Pa., 2016). Distillation and fractionation as utilized in the present disclosure have the usual meanings associated with these terms. Distillation refers to separating a mixture by boiling point into its component parts. Fractionation refers to separation of a mixture into its component parts, for example, by distillation.

(12) In the present disclosure, the term “based”, when used to characterize a composition, refers to a mixture of compounds. For example, iso-octane based diluent refers to a diluent including iso-octane and one or more other compounds. For example, the iso-octane based diluent may include more than one C.sub.8H.sub.18 isomer, or may include one or more iso-octane isomer(s) and other compounds. The other compounds may be, for example, byproducts of the synthesis of iso-octane.

(13) In alternative embodiments, a wide variety of processes may be used to produce high-octane low vapor pressure diluents, for example, but not limited to iso-octane or iso-hexane, for example with starting materials that include butane, isobutane, butene and/or iso-butylene. If butane is the feed, it may for example be transformed into iso-butane through an isomerization process, and the isobutane may be transformed to iso-butylene through a dehydrogenation process, with two moles of iso-butylene combined to make iso-octene, and finally the iso-octene may be hydrogenated to make iso-octane. Dimerization of propane as the feed may be utilized, for example, as a route to making iso-hexane.

(14) Alkylation is a chemical reaction between an iso-paraffin and an olefin to make a paraffin of higher molecular weight. Alkylate can for example be manufactured starting from butane, isobutane, propane, propylene and/or amylene.

(15) In an alternative embodiment, a bitumen blend comprising a high-octane low vapor pressure diluent fraction may be prepared from natural gas condensate, or from any of a wide variety of liquefied petroleum gas (or liquid petroleum gas, LPG) or other feedstocks, for example comprising C3 to C7 hydrocarbons. Such feedstocks may include aromatic compounds. Natural gas condensate may be separated by fractionation, for example into a variety of light fractions and heavy fractions. Heavy fractions separated from the diluent may for example be used for treating emulsions, such as emulsions produced from a reservoir. for example to enhance the separation between bitumen and water.

(16) Light fractions separated from a diluent derived from a natural gas condensate may be characterized, for example, as having an IBP of up to about 80° C., including 95% of the C5-C6 hydrocarbons present in the diluent. Light fractions of this kind may for example be utilized as a feedstock for an isomerization process to convert the linear C5-C6 hydrocarbons into isomers (for example, iso-octane) having a higher octane rating and a lower vapor pressure than the light fraction, and, when blended with bitumen, the isomeric product may reduce diluent requirements for the transportation of bitumen.

(17) In some embodiments, alternative high-octane diluents may be produced via natural gas or solid gasification processes. These alternatives could for example produce a gasoline type diluent with higher octane rating than condensate, but lower than alkylate or isooctane.

(18) The low vapor pressure diluent/bitumen blend may be transported by a variety of methods, including by pipeline, by rail, or by motor vehicle such as a truck or a ship. Depending on market considerations, one form of transportation may be more or less expensive at any given time. Product quality considerations differ between transportation methods. In general, less high-octane low vapor pressure diluent may be blended with bitumen for rail transportation compared to the amount required for pipeline transportation. A diluent-bitumen blend formulated for rail transportation may be referred to as railbit. Dilbit may for example have a diluent:bitumen ratio of about 30:70 to about 40:60. Railbit may for example have a diluent:bitumen ratio of about 12:88 to about 40:60. If the low vapour pressure diluent/bitumen blend is transported by ship across a body of water, the ship may utilize heat to maintain a certain viscosity of the blend during transportation. For the blend to be pumped at a destination (e.g., a marine terminal), the blend viscosity may be, for example, about less than 800 cSt.

(19) Although various embodiments of the invention are disclosed herein, many adaptations and modifications may be made within the scope of the invention in accordance with the common general knowledge of those skilled in this art. Such modifications include the substitution of known equivalents for any aspect of the invention in order to achieve the same result in substantially the same way. Numeric ranges are inclusive of the numbers defining the range. The word “comprising” is used herein as an open-ended term, substantially equivalent to the phrase “including, but not limited to”, and the word “comprises” has a corresponding meaning. As used herein, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a thing” includes more than one such thing. Citation of references herein is not an admission that such references are prior art to the present invention. Any priority document(s) and all publications, including but not limited to patents and patent applications, cited in this specification are incorporated herein by reference as if each individual publication were specifically and individually indicated to be incorporated by reference herein and as though fully set forth herein. The invention includes all embodiments and variations substantially as hereinbefore described and with reference to the examples and drawings.

EXAMPLES

Iso-Octane Based Diluent

(20) This Example includes data that characterizes the performance of an iso-octane based diluent used as a bitumen diluent. The blend of iso-octane based diluent and bitumen was obtained by mixing between 30% vol and 45% vol of iso-octane based diluent with 55% vol to 70% vol of a sample of bitumen from the Athabasca oil sands in Northern Alberta, Canada, targeting a pipeline viscosity specification of 350 mm.sup.2/s at 11.9° C. FIG. 1 and FIG. 2 illustrate the kinematic viscosity (mm.sup.2/s) and density (g/cc) of the iso-octane based diluent over a range of temperatures.

(21) Table 1 shows typical properties of the iso-octane based diluent, including a relatively high octane number (RON 100.5 and MON 99.5).

(22) FIG. 3 and FIG. 4 show the kinematic viscosity and density behaviour, respectively, of the raw Athabasca Bitumen at different temperatures.

(23) FIG. 5 shows the kinematic viscosity of the iso-octane based diluent/bitumen blend at different concentrations (˜27-42% vol) of diluent and at different temperatures.

(24) Table 2 shows typical properties of the iso-octane based diluent/bitumen blend with a kinematic viscosity of 351 mm.sup.2/s at 11.9° C.

(25) TABLE-US-00001 TABLE 1 Typical properties of iso-octane based diluent Analysis Method Results Units API Gravity at 15° C. ASTM D4052 70.2 API RON ASTM D2699 100.5 — MON ASTM D2700 99.5 — Sulfur Content ASTM D5453, 4.4 mg/kg Reid Vapor Pressure ASTM5191 13.3 kPa

(26) TABLE-US-00002 TABLE 2 Typical iso-optene based diluent/bitumen blend Analysis Method Results Units API Gravity at 15.6° C. ASTM D5002 26.4 API (°) Kinematic Viscosity ASTM 02170 351 mm.sup.2/s Acid Number ASTM D664 1.79 mg KOH/g Total Sulfur ASTM D4294 3.4 wt % Micro Carbon Residue ASTM 04530 10.45 wt % Reid Vapor Pressure ASTM 323 <50 kPa

(27) FIG. 6 represents the simulated distillation curve for an iso-octane based diluent/bitumen blend obtained in the lab. This figure shows the discontinuity or gap (gap or overlap.sub.5/95=ASTM D86.sub.5 vol % Temp of HeavyCut—ASTM D86.sub.95 vol % Temp of Light Cut) between the FBP of the diluent and the IBP of the bitumen. This discontinuity in boiling points facilitates the substantially complete separation (˜95-98% recovery) of the two fractions and reduces the cross contamination of the two fractions, maintaining the chemical integrity of the diluent, particularly with respect to octane number.

(28) FIG. 7 illustrates the fractionation of an iso-octane based diluent/bitumen blend. This figure was obtained by simulating the thermal fractionation of the blend using a standard distillation configuration: feed preheat train. feed process furnace heater, a column with tray, overhead condenser system, stripping steam, and at atmospheric pressure. The simulation model was developed using commercially available software (UniSim Design R430). This figure shows the comparison (distillation curves) of the original blend materials (iso-octane based diluent and bitumen) with the corresponding materials obtained (recovered) by distillation and shows that the distillation curve for each material prior to blending is similar to the distillation curve for each material after separation from the blend.

(29) In an embodiment of the present disclosure, removal of sulfur-containing compounds (e.g., H.sub.2S, mercaptans) from a high-octane low vapor pressure blendstock may be a step in the process of recovering a high-octane low vapor pressure diluent (blendstock) from the high-octane low vapor pressure diluent/bitumen blend. For instance, during at least one of mixing and transporting the high-octane low vapor pressure diluent/bitumen blend, a portion of a sulfur content of the bitumen may transfer to the high-octane low vapor pressure diluent and the transferred portion may then be removed from the diluent after the diluent and bitumen are thermally separated.

(30) FIG. 8 is line graph illustrating the results of an iso-octane based diluent/bitumen blend compatibility study, measuring incompatibility tendency (via P-value) of a iso-octane based diluent/bitumen blend as a function of the concentration (% volume) of iso-octane based diluent, indicating that the incompatibility zone of the iso-octane based diluent/bitumen blend was observed above an iso-octane concentration of around 73 vol % and that the blend is stable/compatible (asphaltenes precipitation is not expected) at a diluent concentration below about 73 vol %. In the context of the present disclosure, stability of a single compound or blend (mixture) of compounds and compatibility of a blend (mixture) of compounds refers to a lack of asphaltenes precipitation, that is, S.sub.BN/I.sub.N>1, For example, a stable high-octane low-boiling point diluent fraction may be combined with an unstable high-boiling point bitumen fraction to form a compatible low vapor pressure blend.