US20160053192A1

US20160053192A1 - Bright stock base oil blend

Info

Publication number: US20160053192A1
Application number: US14/465,602
Authority: US
Inventors: Stephen Joseph Miller
Original assignee: Chevron USA Inc
Current assignee: Chevron USA Inc
Priority date: 2014-08-21
Filing date: 2014-08-21
Publication date: 2016-02-25

Abstract

A method is disclosed for making a bright stock base oil blend meeting API Group II specifications. The method comprises blending (a) a major amount of a petroleum-derived bright stock component having kinematic viscosity at 100° C. of from 20 to 50 mm²/s with a sufficient amount of (b) a propylene oligomer component having a viscosity index of from 30 to 60, to provide a bright stock base oil blend having a higher viscosity than the petroleum-derived bright stock component and a higher viscosity index than the propylene oligomer component.

Description

TECHNICAL FIELD

This disclosure is directed to bright stock base oil blends meeting API Group II specifications and methods for preparing the same.

BACKGROUND

High viscosity oils of improved quality are in general demand for a variety of applications including marine oils, mono-grade motor oils, gear oils, railroad engine oils, farm equipment oils, and greases. High viscosity oils generally require some bright stock in their formulation, the amount of which depends on the product. In typical formulations, Group I bright stock is used. One problem with Group I bright stock is that it is not a distillate and, therefore, is typically of low quality, particularly with respect to oxidation stability. Moreover, the supply of Group I bright stock is diminishing, especially as Group I base oil plants are being shut down.
A Group II bright stock would have significant value in the marketplace, especially as a blending component with other Group II base oils. Methods for making such a bright stock are limited, usually requiring hydrocracking and solvent dewaxing of petroleum residual fractions. Residuum streams are generally difficult to process for lubricant base oils.
U.S. Pat. No. 7,776,206 discloses a process for making a Group II bright stock using deep-cut distillation, which employs a distillate fraction to make the bright stock, rejecting the heavy aromatics most difficult to hydrocrack and stabilize, as well as the heavy wax most difficult to isomerize, in the distillation bottoms. The light fraction is hydrocracked to raise the viscosity index (VI) and to reduce the concentration of nitrogen and sulfur, then dewaxed to give a Group II bright stock with low pour and cloud points. In order to get the high viscosity required, a wiped film evaporator (WFE) is used in combination with vacuum distillation. While WFEs are used commercially and are available in the marketplace, their throughput size is limited.
U.S. Pat. No. 8,124,821 discloses a method for making a bright stock by oligomerization of propylene using an ionic liquid catalyst. While bright stock produced from propylene oligomerization has high viscosity, high oxidation stability and low pour and cloud points, the VI is low (e.g., less than 60). Co-oligomerization of propylene with a longer normal alpha-olefin (NAO), such as 1-octene or 1-decene, can produce a higher VI bright stock, but the NAO feed can be expensive and in short supply. It would be advantageous to find another way get the VI up to at least 80, producing a Group II bright stock. Since the propylene oligomer is highly paraffinic, it would be advantageous have some cycloparaffinic and/or aromatic character to provide better additive solubility and seal swell properties.
Improved processes for producing bright stocks meeting API Group II specifications are needed. It has been found that bright stock prepared by propylene oligomerization is particularly advantageous for blending with marginal quality petroleum-derived Group II bright stock to provide a bright stock blend which meets minimum viscosity requirements and has acceptable VI, good additive solubility, and improved low temperature properties.

SUMMARY

In one aspect, there is provided a method for making a bright stock base oil blend meeting API Group II specifications comprising: blending (a) a major amount of a petroleum-derived bright stock component having kinematic viscosity at 100° C. of from 20 to 50 mm²/s with a sufficient amount of (b) a propylene oligomer component having a viscosity index of from 30 to 60, to provide a bright stock base oil blend having a higher viscosity than the petroleum-derived bright stock component and a higher viscosity index than the propylene oligomer component.

DETAILED DESCRIPTION

The following terms will be used throughout the specification and will have the following meanings unless otherwise indicated.
The term “petroleum-derived” means that the product, fraction, or blending stock originates from or is produced at some stage from a petroleum-based source.
A “bright stock” is a heavy base oil having an initial boiling point of greater than 900° F. (482° C.) and a kinematic viscosity at 100° C. of at least 15 mm²/s (e.g., from 15 to 100 mm²/s).
An “oligomer” refers to compositions having from 2 to 100 monomer units. A “monomer” refers to one of the basic structural units of a polymer or oligomer. In the case of a homo-oligomer, a single repeating structural unit forms the oligomer. In the case of a co-oligomer, two or more structural units are repeated—either in a pattern or randomly—to form the oligomer.
The term “Group I” refers to a base oil having a saturates content of less than 90% and/or a total sulfur content of greater than 0.03% and has a viscosity index of greater than or equal to 80 and less than 120, using the ASTM methods specified in Table E-1 of American Petroleum Institute (API) Publication 1509.
The term “Group II” refers to a base oil having greater than or equal to 90% saturates and less than or equal to 0.03% sulfur and has a viscosity index greater than or equal to 80 and less than 120, using the ASTM methods specified in Table E-1 of American Petroleum Institute (API) Publication 1509.
The term “Group III” refers to a base oil which contains greater than or equal to 90% saturates and less than or equal to 0.03% sulfur and has a viscosity index greater than or equal to 120, using the ASTM methods specified in Table E-1 of API Publication 1509.
The term “base oil” as used herein shall be understood to mean a base stock or blend of base stocks which is a lubricant component that is produced by a single manufacturer to the same specifications (independent of feed source or manufacturer's location); that meets the same manufacturer's specification; and that is identified by a unique formula, product identification number, or both.
“Kinematic viscosity” is a measurement in mm²/s of the resistance to flow of a fluid under gravity, determined by ASTM D445.
“Viscosity index” is an empirical, unit-less number indicating the effect of temperature change on the kinematic viscosity of an oil. The higher the VI of the oil, the lower its tendency to change viscosity with temperature. VI is measured according to ASTM D2270.
“Pour point” is a measurement of the temperature at which a sample will begin to flow under certain carefully controlled conditions, which can be determined as described in ASTM D5950.
“Cloud point” is a measurement of the temperature at which a lube oil sample begins to develop a haze as the oil is cooled under specified conditions, which can be determined as described in ASTM D5773.

Petroleum-Derived Bright Stock Component

Petroleum-derived bright stock constitutes a bottoms fraction which has been highly refined and dewaxed. Typical petroleum-derived bright stocks can be prepared from deasphalted oil, hydrocracked petroleum residuum stream, and heavy coker products.
The petroleum-derived bright stock can be a conventional petroleum-derived bright stock, an unconventional petroleum-derived bright stock, or a mixture thereof. Conventional petroleum-derived bright stock has a viscosity index of less than 120 (e.g., from 80 to less than 120). Unconventional petroleum-derived bright stock, such as bright stock derived from Daqing crude, has a viscosity index of at least 120 (e.g., from 120 to 160, or from 120 to 140).
In one embodiment, the petroleum-derived bright stock is a hydrocracked and dewaxed light distillate fraction having a distillation cut point in the range of 1150° F. to 1300° F. (621° C. to 704° C.), as described in U.S. Pat. No. 7,776,206. The cut point is the temperature at which there are equal amounts of material overlapping from adjacent cuts. When data is not available for one of both adjacent cuts, cut point estimates are the 10 and 90 percent points on the distillation curve.
The petroleum-derived bright stock has a kinematic viscosity at 100° C. (KV₁₀₀) of at least 15 mm²/s (e.g., at least 20 mm²/s, at least 25 mm²/s, at least 30 mm²/s, from 15 to 60 mm²/s, from 15 to 45 mm²/s, from 20 to 60 mm²/s, from 20 to 45 mm²/s, from 25 to 60 mm²/s, from 25 to 45 mm²/s, from 30 to 60 mm²/s, or from 30 to 45 mm²/s).
The petroleum-derived bright stock can have a high viscosity index, such as at least 80 (e.g., from 80 to 145, from 80 to 130, from 80 to less than 120, from 80 to 110, from 80 to 100, from 80 to 90, from 85 to 145, from 85 to 130, from 85 to less than 120, from 85 to 110, from 85 to 100, from 90 to 145, from 90 to 130, from 90 to less than 120, from 90 to 110, from 100 to 145, from 100 to 130, or from 100 to less than 120).
The petroleum-derived bright stock can have low a pour point, such as 0° C. or less (e.g., −5° C. or less, −10° C. or less, −20° C. or less, from 0° C. to −25° C., from −5° C. to −25° C., or −10° C. to −25° C.).
The petroleum-derived bright stock can have a cloud point of 15° C. or less (e.g., 10° C. or less, from 0° C. to 15° C., from 0° C. to 10° C., or from 5° C. to 15° C.).
The petroleum-derived bright stock can be a Group II base oil or a Group III base oil.

Propylene Oligomer Component

The propylene oligomer disclosed herein can be synthesized by oligomerizing propylene in the presence of an ionic liquid catalyst. The propylene can come from a number of sources, including: as a byproduct from the steam cracking of liquid feedstocks such as propane, butane, gas condensates, naphtha and LPG; from off-gases produced in a FCC unit in a refinery; from propane dehydrogenation using a noble metal catalyst; and by metathesis. Propylene supplies are increasing and there is a demand for upgrading them into higher valued products such as base oils.
Oligomerization conditions include temperatures between the melting point of the ionic liquid catalyst and its decomposition temperature. In one embodiment, the oligomerization conditions include a temperature of from 0° C. to 100° C. and a pressure of from atmospheric pressure to 1000 psig (0.10 to 6.89 MPa). The oligomerization can carried out in continuous, batch or semi-batch mode.
A skilled artisan will recognize that depending on the process utilized to produce the propylene oligomer, the as-produced propylene oligomers can already be substantially saturated. For example, a process which is carried out in the presence of hydrogen can produce an olefin oligomer which may or may not require a separate hydrogenation step to provide a product with the desired properties.
The propylene oligomer can comprise at least 70% propylene monomer units (e.g., at least 75% propylene monomer units, at least 80% propylene monomer units, at least 85% propylene monomer units, at least 90% propylene monomer units, at least 95% propylene monomer units, or at least 99% propylene monomer units). Alternatively, the propylene oligomer can consist essentially of propylene monomer units.
The propylene oligomer can comprise a significant amount of hydrocarbons boiling at 900° F. (482° C.) or higher. The level can be greater than 25 wt. %, greater than 35 wt. %, or from 45 to 70 wt. %. Higher levels of hydrocarbons boiling at 900° F. (482° C.) or higher are desired, as there are increasingly limited amounts of base oils with these properties, especially as Group I base oil plants are being shut down.
In one embodiment which employs a high viscosity petroleum-derived bright stock in the lubricating oil composition disclosed herein, a somewhat lower distillation cut point, such as 800° F. (427° C.), can be taken on the propylene oligomer thereby increasing yield and improving economics because of the cost of propylene.
The propylene oligomer can have a kinematic viscosity at 100° C. of at least 50 mm²/s (e.g., from 50 to 100 mm²/s or from 55 to 95 mm²/s).
The propylene oligomer can have a low viscosity index, such as 60 or less (e.g., from 30 to 60 or from 35 to 55).
The propylene oligomer can have a low pour point, such as −10° C. or less (e.g., from −10° C. to −60° C., from −10° C. to −40° C., or from −10° C. to −25° C.).
The propylene oligomer can have a low cloud point, such as point −25° C. or less (e.g., −40° C. or less, −45° C. or less, −50° C. or less, −55° C., −60° C. or less, from −40° C. to −60° C., from −45° C. to −60° C., from −50° C. to −60° C., or from −55° C. to −60° C.).
In one embodiment, the propylene oligomer is a bright stock.

Bright Stock Base Oil Blend

In general, the relative amounts of the petroleum-derived bright stock and the propylene oligomer can be tuned to produce a bright stock base oil blend with a desired balance between viscosity, viscosity index and cold temperature flow properties.
The petroleum-derived bright stock is typically present therein in a major amount, i.e., an amount of greater than 50 wt. %, based on the total weight of the blend. In general, the blend will comprise from 90 to 60% (e.g., from 90 to 65 wt. %, from 85 to 60 wt. %, from 85 to 65 wt. %, or from 85 to 70 wt. %) of the petroleum-derived bright stock component and from 10 wt. % to 40 wt. % (e.g., from 10 to 35 wt. %, from 15 to 40 wt. %, from 15 to 35 wt. %, or from 15 to 30 wt. %) of the propylene oligomer component, based on the total weight of the blend. If too small an amount of the propylene oligomer is used, the blend may not have acceptable viscosity index and/or low temperature properties. If too much of the propylene oligomer is used, it may be more costly or the viscosity of the blend may be too high for practical use.
The bright stock base oil blend disclosed herein has a higher viscosity than that of the petroleum-derived bright stock component. When propylene oligomer is present in the base oil blend in amounts of from 10 to 40 wt. %, based on the total weight of the blend, the kinematic viscosity at 100° C. of the resulting base oil blend can be at least 3 mm²/s higher (e.g., at least 5 mm²/s higher, at least 10 mm²/s higher, from 3 to 20 mm²/s higher, from 3 to 15 mm²/s higher, from 3 to 10 mm²/s higher, from 5 to 20 mm²/s higher, from 5 to 15 mm²/s higher, or from 5 to 10 mm²/s higher) than the petroleum-derived bright stock component. The blend can have a kinematic viscosity at 100° C. of at least 28 mm²/s (e.g., at least 30, from 28 to 50 mm²/s, from 28 to 45 mm²/s, from 30 to 50 mm²/s, or from 30 to 45 mm²/s).
The bright stock base oil blend disclosed herein has a higher viscosity index than that of the propylene oligomer component. When propylene oligomer is present in the base oil blend in amounts of from 10 to 40 wt. %, based on the total weight of the blend, the viscosity index of the resulting base oil blend can be at least 20 higher (e.g., at least 25 higher, from 20 to 50 higher, from 20 to 40 higher, from 25 to 50 higher, or from 25 to 40 higher) than the propylene oligomer component. The blend can have a high viscosity index, such as at least 85 (e.g., at least 90, from 85 to 140, from 85 to 130, from 85 to less than 120, from 85 to 110, from 85 to 100, from 90 to 140, from 90 to 130, from 90 to less than 120, or from 90 to 110).
The bright stock base oil blend disclosed herein has improved cold temperature flow properties than that of the petroleum-derived bright stock component. When propylene oligomer is present in the base oil blend in amounts of from 10 to 40 wt. %, based on the total weight of the blend, the pour point of the blend can be at least 1° C. lower (e.g., at least 2° C. lower, at least 3° C. lower, from 1° C. to 10° C. lower, from 1° C. to 5° C. lower, 1° C. to 3° C. lower, from 2° C. to 10° C. lower, or from 2° C. to 5° C. lower) than that of the petroleum-derived bright stock component. The blend can have a low pour point, such as −1° C. or less (e.g., from −1° C. to −25° C., from −5° C. to −25° C., or from −10° C. to −25° C.).
When propylene oligomer is present in the base oil blend in amounts of from 10 to 40 wt. %, based on the total weight of the blend, the cloud point of the blend can be at least 1° C. lower (e.g., at least 2° C. lower, e.g., at least 3° C. lower, from 1° C. to 10° C. lower, from 1° C. to 5° C. lower, 1° C. to 3° C. lower, from 2° C. to 10° C. lower, or from 2° C. to 5° C. lower) than that of the petroleum-derived bright stock component. The blend can have a cloud point of 14° C. or less (e.g., 13° C. or less, 5° C. or less, from 13° C. to −15° C., or from 5° C. to −15° C.).

EXAMPLES

The following illustrative examples are intended to be non-limiting.

Example 1

Oligomerization of propylene was carried out using a supported liquid phase ionic liquid catalyst according to the procedure described in U.S. Pat. No. 8,729,329. The heavy viscous colorless oil was then analyzed for boiling range, viscosity index, kinematic viscosity, pour point and cloud point. The products were analyzed for their boiling range by simulated distillation analysis. The properties of the 900° F.+fraction are set forth are set forth in Table 1.

	TABLE 1

	KV₁₀₀, mm²/s	96.3
	VI	58
	Pour point, ° C.	−15
	Cloud point, ° C.	−60

Example 2

A 300 cc autoclave was charged with 20 g of ionic liquid catalyst (1-butyl-pyridinium chloroaluminate ionic liquid catalyst), 0.1-1 g of HCl and 20 g of n-hexane (as diluent) under nitrogen in a glove box. The autoclave was sealed and removed from the glove box and cooled in a dry ice bath and affixed to a propylene tank (>99% commercial grade) via an inlet that allows the flow of propylene into the reactor where 100 g of propylene was transferred to the reactor (autoclave). The reactor was affixed to an overhead stirrer. The reaction temperature was controlled by a thermocouple connected to a temperature control apparatus. Once everything was in place, the reaction began by slowly stirring the charge in the reactor at 0° C. in a batch-style operation. The reaction was exothermic and the rise in temperature was quick and sudden. The rise in temperature was controlled by immersing the autoclave in an ice bath. The reaction temperature was kept at around 50° C. The pressure of the reaction began very high and decreased as the propylene was oligomerized. The reaction was allowed to proceed for 15-30 minutes. The reaction, then, was stopped and the reactor was allowed to cool to room temperature. The reaction was worked up by simply decanting off the organic layer (the products). The remaining ionic liquid phase was washed with hexane to remove all residual organics from the ionic liquid phase, and the wash was added to the original decant. The organic layer was then washed thoroughly with water and dried over anhydrous MgSO₄and then filtered. The filtrate was concentrated on a rotary evaporator to remove hexane (used as solvent to extract oligomers from the catalyst). The heavy viscous colorless oil was then analyzed for boiling range, viscosity index, kinematic viscosity, pour point and cloud point. The products were analyzed for their boiling range by simulated distillation analysis. The properties of the 900° F.+fraction are set forth are set forth in Table 2.

	TABLE 2

	KV₁₀₀, mm²/s	56
	VI	43
	Pour point, ° C.	4
	Cloud point, ° C.	<−56

Example 3

A low viscosity bright stock was prepared from Daqing crude by hydroisomerization for use as a bright stock blending component. The properties of the Daqing bright stock are set forth in Table 3.

	TABLE 3

	KV₁₀₀, mm²/s	21.5
	VI	137
	Pour point, ° C.	−21
	Cloud point, ° C.	15
	Simulated Distillation, ° F., wt. %
	0.5/5	897/960
	10/30	989/1055
	50	1108
	70/90	1167/1253
	95/99.5	1291/1338

Example 4

A bright stock blend was prepared which comprised 26 wt. % of the propylene oligomer of Example 1 and 74 wt. % of the petroleum-derived bright stock of Example 3. The properties of the petroleum-derived bright stock, the propylene oligomer, and the bright stock blend are summarized in Table 4.

TABLE 4

Petroleum-
Derived	Propylene
Bright Stock	Oligomer	Blend A

KV₁₀₀, mm²/s	21.5	96.3	26.6
VI	137	58	125
Pour point, ° C.	−21	−15	−24
Cloud point, ° C.	15	−60	13

This Example illustrates that the propylene oligomer effectively lowered the pour point and cloud point and raised the viscosity by 5 mm²/s. Conducting the same experiment using more propylene oligomer would be expected to produce a bright stock base oil blend having further improved low temperature properties while keeping the VI above 90.

Example 5

Three bright stock blends were prepared from the propylene oligomer of Example 1 and another low viscosity, petroleum-derived bright stock. The properties of the petroleum-derived bright stock, the propylene oligomer, and the bright stock blends are summarized in Table 5.

TABLE 5

Petroleum-
Derived	Propylene
Bright Stock	Oligomer	Blend B	Blend C	Blend D

Wt. % Bright			85	80	67
Stock
Wt. % Propylene			15	20	33
Oligomer
KV₁₀₀, mm²/s	23.6	96.3	28	30	35
VI	89	58	84	82	78
Pour point, ° C.	0	−15	−1	−3	−4
Cloud point, ° C.	7	−60	4	2	1

Example 6

A bright stock blend was prepared which comprised 27 wt. % of the propylene oligomer of Example 1 and 73 wt. % of a petroleum-derived bright stock. The properties of the petroleum-derived bright stock, the propylene oligomer, and the bright stock blend are summarized in Table 6.

TABLE 6

Petroleum-
Derived	Propylene
Bright Stock	Oligomer	Blend E

KV₁₀₀, mm²/s	32.5	96.3	41.3
VI	96	58	87
Pour point, ° C.	−9	−15	−12
Cloud point, ° C.	—	−60	−12

This Example illustrates that the propylene oligomer effectively improved the low temperature properties and raised the viscosity by 7.8 mm²/s. Conducting the same experiment using less propylene oligomer would be expected to produce a bright stock base oil blend having a VI above 90 with improved low temperature properties.

Example 7

A bright stock blend was prepared which comprised 21 wt. % of the propylene oligomer of Example 2 and 79 wt. % of the petroleum-derived bright stock employed in Example 6. The properties of the petroleum-derived bright stock, the propylene oligomer, and the bright stock blend are summarized in Table 7.

TABLE 7

Petroleum-
Derived	Propylene
Bright Stock	Oligomer	Blend F

KV₁₀₀, mm²/s	32.5	56	36
VI	96	43	88
Pour point, ° C.	−9	4	−12

This Example illustrates that the propylene oligomer effectively lowered the pour point and raised the viscosity by 3.5 mm²/s. Conducting the same experiment using less propylene oligomer would be expected to produce a bright stock base oil blend having a VI above 90 with improved low temperature properties.
For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term “about.” Furthermore, all ranges disclosed herein are inclusive of the endpoints and are independently combinable. Whenever a numerical range with a lower limit and an upper limit are disclosed, any number falling within the range is also specifically disclosed.
As used herein, the term “comprising” means including elements or steps that are identified following that term, but any such elements or steps are not exhaustive, and an embodiment can include other elements or steps.
Unless otherwise specified, the recitation of a genus of elements, materials or other components, from which an individual component or mixture of components can be selected, is intended to include all possible sub-generic combinations of the listed components and mixtures thereof.
Any term, abbreviation or shorthand not defined is understood to have the ordinary meaning used by a skilled artisan at the time the application is filed. The singular forms “a,” “an,” and “the,” include plural references unless expressly and unequivocally limited to one instance.
All of the publications, patents and patent applications cited in this application are herein incorporated by reference in their entirety to the same extent as if the disclosure of each individual publication, patent application or patent was specifically and individually indicated to be incorporated by reference in its entirety.

Claims

1. A method for making a bright stock base oil blend meeting API Group II specifications comprising: blending (a) a major amount of a petroleum-derived bright stock component having kinematic viscosity at 100° C. of from 20 to 50 mm²/s with a sufficient amount of (b) a propylene oligomer component having a viscosity index of from 30 to 60, to provide a bright stock base oil blend having a higher viscosity than the petroleum-derived bright stock component and a higher viscosity index than the propylene oligomer component.

2. The method of claim 1, wherein the blend comprises from 60 to 90% of the petroleum-derived bright stock component and from 40 wt. % to 10 wt. % of the propylene oligomer component, based on the total weight of the blend.

3. The method of claim 1, wherein the blend comprises from 70 to 85% of the petroleum-derived bright stock component and from 30 wt. % to 15 wt. % of the propylene oligomer component, based on the total weight of the blend.

4. The method of claim 1, wherein the blend has a kinematic viscosity at 100° C. that is at least 3 mm²/s higher than that of the petroleum-derived bright stock component.

5. The method of claim 1, wherein the blend has a viscosity index that is at least 20 higher than that of the propylene oligomer component.

6. The method of claim 1, wherein the blend has a pour point that is at least 1° C. lower than that of the petroleum-derived bright stock component.

7. The method of claim 1, wherein the blend has a cloud point that is at least 1° C. lower than that of the petroleum-derived bright stock component.

8. The method of claim 1, wherein the petroleum-derived bright stock component has a viscosity index of from 80 to less than 120.

9. The method of claim 1, wherein the petroleum-derived bright stock component has a viscosity index of from 120 to 145.

10. The method of claim 1, wherein the petroleum-derived bright stock component has a pour point of 0° C. or less.

11. The method of claim 1, wherein the petroleum-derived bright stock component has a cloud point of 15° C. or less.

12. The method of claim 1, wherein the propylene oligomer component has a kinematic viscosity at 100° C. of from 50 to 100 mm²/s.

13. The method of claim 1, wherein the propylene oligomer component has a pour point of −10° C. or less.

14. The method of claim 1, wherein the propylene oligomer component has a cloud point of −25° C. or less.