Method of recycling waste lubricating oil

Abstract

To provide a method of recycling a waste lubricating oil.SOLUTION: The method includes the steps of: providing a waste lubricating oil-derived fraction; pretreating the waste lubricating oil-derived fraction; and hydrocracking the pretreated waste lubricating oil-derived fraction. According to the method, waste lubricating oil can be recycled into fuel oil and high-grade lubricating base oil, thereby providing economic benefits.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a method for recycling used lubricating oil. [Background technology]

[0002] Waste lubricating oil undergoes a series of refining processes and is entirely used as fuel oil in Japan, while overseas some is used as fuel oil and another part is used as low-grade recycled base oil.

[0003] On the other hand, generally speaking, a good lubricant base oil has a high viscosity index, excellent stability (oxidation, heat, UV, etc.), and low volatility. The American Petroleum Institute (API) classifies lubricant base oils according to their quality as shown in Table 1 below.

[0004] [Table 1]

[0005] In the above classification, the quality of lubricant base oil is evaluated as being superior from Group I to Group V, and among them, Group III lubricant base oil is generally produced by advanced hydrocracking reaction. Unconverted oil, which is a heavy fraction that is not converted to fuel oil in the fuel oil hydrocracking process, is usually used as a feedstock for producing high-grade lubricant base oil of Group III or higher. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Korean Patent Publication No. 10-2007-0116074 Summary of the Invention [Problem to be solved by the invention]

[0007] The present disclosure aims to provide a method for recycling waste lubricating oil. [Means for solving the problem]

[0008] A method for recycling used lubricants according to one aspect of the present disclosure includes providing a fraction derived from used lubricants, pretreating the fraction derived from used lubricants, and hydrocracking the pretreated fraction derived from used lubricants. According to one embodiment, the fraction derived from used lubricants comprises a kinematic viscosity measured at 40° C. of 20 cst to 60 cst, and a pour point of less than 0° C.

[0009] According to one embodiment, the pre-treating step may comprise a step of solvent extraction of the fraction derived from the used lubricating oil.

[0010] According to one embodiment, the method may further comprise a first blending step of blending the fraction derived from used lube oil with a hydrocarbon feedstock prior to the hydrocracking step to produce a first blend.

[0011] According to one embodiment, the first formulation may include 1 to 10% by total volume of the fraction derived from used lubricating oil.

[0012] According to one embodiment, the method may further comprise recovering a plurality of fractions from the product of the hydrocracking step, the fraction comprising a first fraction and a second fraction.

[0013] According to one embodiment, the first fraction may have a boiling point in the fuel oil boiling range.

[0014] According to one embodiment, the boiling point of the second fraction may be higher than the boiling point of the first fraction.

[0015] According to one embodiment, the method may further comprise a second blending step of blending the second fraction with another fraction derived from used lubricating oil to produce a second blend.

[0016] According to one embodiment, the separate fraction derived from the used lubricant introduced in the second blending step may be 3 to 50% by volume of the second blend.

[0017] According to one embodiment, the method may further comprise catalytically dewaxing the second blend.

[0018] According to one embodiment, the method may further include hydrofinishing the catalytically dewaxed second blend and recovering the product of the hydrofinishing step as lubricant base oil. Effect of the Invention

[0019] According to the present disclosure, the used lubricating oil can be recycled into fuel oil and high-grade lubricating base oil, which has economic advantages, and the used lubricating oil can be used as a feed for producing products for various applications. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The objects, advantages and features of the present disclosure will become more apparent from the following detailed description and preferred embodiments, but the present disclosure is not necessarily limited thereto. In addition, in describing the present disclosure, if it is determined that a specific description of related known techniques may unnecessarily obscure the gist of the present disclosure, the detailed description will be omitted.

[0021] According to a first aspect of the present disclosure, a method for recycling used lubricants is provided, the method comprising the steps of providing a fraction derived from used lubricants, pretreating the fraction derived from the used lubricants, and hydrocracking the pretreated fraction derived from the used lubricants. Here, recycling used lubricants broadly means regenerating the used lubricants as a feedstock for producing reusable fractions, and in the present disclosure means reusing the used lubricants as a feedstock for producing fuel oils and lubricant base oils.

[0022] The fraction derived from the used lubricating oil refers to the lubricating oil after use. Usually, various additives are added to the lubricating base oil, but the additives contain a large amount of impurities that are not suitable for use as a lubricating base oil, so the fraction derived from the used lubricating oil can also contain a large amount of impurities.For example, the fraction derived from the used lubricating oil can contain 200 to 3000 ppm of sulfur, 200 to 2000 ppm of nitrogen, 20 to 2000 ppm of chlorine, and other metal impurities that can flow into the lubricating action.

[0023] In one embodiment, the fraction derived from the used lubricating oil may have a kinematic viscosity of 20 cst to 60 cst measured at 40° C., and a pour point of less than 0° C. Preferably, the fraction derived from the used lubricating oil may have a kinematic viscosity of 25 to 50 cst measured at 40° C., and a pour point of -5° C. or less, more preferably a kinematic viscosity of 26 to 40 cst measured at 40° C., and a pour point of -21 to -6° C.

[0024] In one embodiment, the fraction derived from the used lubricating oil can be a refined fraction. Here, "refined fraction" refers to the fraction obtained after the used lubricating oil is introduced into centrifugation, atmospheric distillation, vacuum distillation, or a combination thereof, and has a reduced impurity content compared to the used lubricating oil. For example, the refined fraction can have a sulfur content of less than 200 ppm, a nitrogen content of less than 100 ppm, and a chlorine content of less than 2000 ppm.

[0025] The method includes a step of pre-treating the used lube oil derived fraction, by which is meant further processing the used lube oil derived fraction prior to being introduced into the hydrocracking process in order to minimize the effect of impurities contained therein on the process and the catalyst.

[0026] In one embodiment, the pre-treating step may include solvent extracting the used lubricant derived fraction.

[0027] Solvent extraction of fractions derived from waste lubricating oil is a step in which the fraction derived from waste lubricating oil and a solvent are mixed in a mixing tank, and then the mixture is allowed to stand to separate into phases, thereby obtaining a phase mainly composed of the fraction to be obtained, and removing the phase containing a large amount of impurities. The solvent used for the solvent extraction is a solvent that has a higher affinity for impurities than the oil components in the fraction derived from waste lubricating oil, and the main solvents used are NMP (N-Methyl-2-Pyrrolidone), sulfolane, DMSO, furfural, phenol, and acetone. The solvent has a high affinity for impurities and a low affinity for the fraction derived from waste lubricating oil, so it is phase-separated from the fraction derived from waste lubricating oil, and can be used without restrictions as long as there is a difference in volatility for subsequent solvent separation.

[0028] The solvent extraction of the fraction derived from the waste lubricating oil is carried out at a temperature of about 30 to 200°C, preferably about 40 to 150°C, more preferably about 60 to 100°C, and at atmospheric pressure of 20 kg / cm 2 , preferably atmospheric pressure to 15 kg / cm 2 , more preferably atmospheric pressure to 10 kg / cm 2 The reaction can be carried out under pressure.

[0029] In addition, the volume ratio of the solvent used in the solvent extraction step of the fraction derived from the waste lubricating oil to the oil component in the fraction derived from the waste lubricating oil can be 1:1 to 10:1, for example, 2:1 to 8:1, 2:1 to 7:1, 2:1 to 6:1, 2:1 to 5:1, 3:1 to 8:1, 3:1 to 7:1, 3:1 to 6:1, 4:1 to 8:1, 4:1 to 7:1, and 5:1 to 8:1. The volume ratio of the solvent used in the solvent extraction step of the refined fraction to the oil component in the refined fraction can most preferably be 1:1 to 1.5:1. The volume ratio is preferable from the viewpoint of the balance between the level of removal of impurities by solvent extraction and the yield of the product of the hydrocracking step generated from the fraction derived from the pretreated waste lubricating oil thereafter.

[0030] The fraction derived from the used lubricating oil after the solvent extraction step may have a specific gravity of 0.8 to 0.9, a kinematic viscosity at 100°C of 4 to 6 cSt, a viscosity index of 110 to 130, a pour point of -18 to -3°C, a sulfur content of less than 150 ppm, a nitrogen content of less than 100 ppm, and a chlorine content of less than 20 ppm. That is, the fraction derived from the used lubricating oil may have improved properties and reduced impurity content by the solvent extraction, may show a light brown color of about 2 to 4 based on ASTM, and may have a reduced sediment content compared to the refined fraction.

[0031] The method includes a step of hydrocracking the fraction derived from the pretreated used lubricating oil. Hydrocracking corresponds to a process of decomposing long-chain hydrocarbons contained in the fraction derived from the pretreated used lubricating oil into shorter-chain hydrocarbons to lighten the fraction by a hydrogenation reaction using a catalyst. Exemplarily, in the hydrocracking step, the C30+ hydrocarbon chains contained in the fraction derived from the pretreated used lubricating oil can be cut into chains having fewer carbon numbers. For this purpose, the hydrocracking step can be carried out under a reaction pressure of about 25 to 320 atm (specifically, about 80 to 250 atm) and a reaction temperature of about 200 to 500°C (specifically, about 250 to 400°C). Furthermore, the hydrocracking step can be carried out for, for example, about 0.1 to 8 hr. -1 Specifically, about 0.5 to 5 hours -1 The reaction can be carried out at a range of low space velocity (LHSV).

[0032] In one embodiment, the method may further comprise a first blending step, prior to the hydrocracking step, of blending the fraction derived from the used lubricating oil with a hydrocarbon feedstock to produce a first blend. The first blending step may be performed prior to the pretreatment step or between the pretreatment step and the hydrocracking step, preferably prior to the pretreatment step. Here, the term "hydrocarbon feedstock" refers to any material that is an input for a refining, conversion or other industrial process in which hydrocarbons are the major constituent. The hydrocarbon feedstock may be provided at a temperature above the pour point and in a liquid state, and may contain non-hydrocarbon components such as heteroatom-containing (e.g., S, N, O, P, metal) organic and inorganic materials. Crude oil, refinery streams, chemical plant streams (e.g., steam cracked tar), and recycle plant streams (e.g., pyrolysis oil from tires or municipal solid waste) are non-limiting examples of hydrocarbon feedstocks. The hydrocarbon feedstock may be a feedstock that is preferably fed to a hydrocracking step for the production of a fraction having a boiling point in the fuel oil boiling range. The above-mentioned hydrocarbon feedstock may be blended with a fraction derived from used lubricants in a first blending step, and then introduced into a hydrocracking step after a pretreatment step, or may be blended with a fraction derived from pretreated used lubricants after a waste lubricant pretreatment step and then introduced into a hydrocracking step. When the first blend is introduced into the hydrocracking step, fractions with various carbon numbers and various degrees of saturation can be obtained compared to the case where only a fraction derived from pretreated used lubricants is introduced into the hydrocracking step.

[0033] In one embodiment, the first blend may contain 1-10% of the fraction derived from used lubricating oil relative to the total volume. When the amount of the fraction derived from used lubricating oil blended with the hydrocarbon feedstock in the first blending step is less than 1% relative to the total volume of the first blend, the fraction derived from used lubricating oil with a high carbon number in the blend is relatively low, so that the hydrocracking of the fraction derived from used lubricating oil with a high carbon number may not be performed smoothly. When the amount of the fraction derived from used lubricating oil blended with the hydrocarbon feedstock in the first blending step exceeds 10% relative to the total volume of the first blend, the feed introduced to the hydrocracking step contains a high proportion of heavy fractions containing a large amount of impurities that induce catalyst deactivation, which may result in an increase in hydrocracking temperature and pressure conditions, thereby placing a strain on the hydrocracking catalyst. The first blend may contain preferably 2-9%, more preferably 4-8% of the fraction derived from used lubricating oil relative to the total volume. The first blend may contain the hydrocarbon feedstock as the remainder other than the fraction derived from used lubricating oil.

[0034] In one embodiment, the method may further include a step of recovering a plurality of fractions including a first fraction and a second fraction from the product of the hydrocracking step. The fraction derived from the hydrocracked waste lubricant or the blend of the hydrocracked first blending step is separated into components according to their boiling points by fractional distillation. Specifically, the product of the hydrocracking step is separated by fractional distillation in the order of a fraction with a low boiling point to a fraction with a high boiling point, and the plurality of fractions thus separated include at least a first fraction and a second fraction with different boiling points, which are recovered and used for an appropriate application.

[0035] In one embodiment, the first fraction may have a boiling point in the fuel oil boiling range. For example, fuel oil includes liquefied petroleum gas (LPG), gasoline, kerosene, light oil, heavy oil, etc., in order of decreasing boiling point. The first fraction may correspond to a fraction having a boiling point in the fuel oil boiling range as described above, and may be further separated into a fraction containing a specific fraction in the fuel oil, as necessary. In one embodiment, the first fraction may have a boiling point of less than 400°C.

[0036] In one embodiment, the boiling point of the second fraction may be higher than that of the first fraction. For example, the second fraction may have a boiling point of 450° C. or higher. The product of the hydrocracking step includes not only fuel oil, which is a fraction cracked in the hydrocracking step, but also a fraction that has not been cracked. "Unconverted oil (UCO)" refers to a heavy fraction that is not converted to fuel oil in the hydrocracking step as described above, and has a higher boiling point than fuel oil. The unconverted oil can be separated from the first fraction having a boiling point in the fuel oil boiling range during fractional distillation and recovered. That is, the second fraction may be a fraction containing unconverted oil and may have a higher boiling point than the first fraction described above. The second fraction containing unconverted oil as described above can be recovered and introduced into the following process steps for producing lubricating base oil. In one embodiment, the second fraction may exhibit a high pour point of 30° C. to 45° C. due to the high wax content of the unconverted oil, but may contain low impurities such as sulfur and nitrogen, less than 10 ppm.

[0037] In one embodiment, the method may further include a second blending step of blending the second fraction with a fraction derived from a separate used lubricating oil to produce a second blend. As described above, the fraction derived from a separate used lubricating oil to be blended with the second fraction containing unconverted oil may undergo the above-mentioned pretreatment step to remove impurities, but is not introduced into the hydrocracking step. Preferably, the fraction derived from the used lubricating oil may be a fraction derived from a pretreated used lubricating oil. The second blending step may include a stirring step for blending a fraction derived from a separate used lubricating oil from the second fraction, but the blending method is not limited thereto. The second blend produced in the second blending step may be regenerated into a lubricating base oil through additional processing thereafter. In this way, by producing a lubricating base oil from a blended raw material of the unconverted oil after the hydrocracking step of the fraction derived from the waste lubricating oil and the fraction derived from the separate used lubricating oil, the lubricating base oil production cost can be reduced, and by recycling the waste lubricating oil instead of disposing of it, it is also advantageous in terms of being environmentally friendly.

[0038] In one embodiment, the fraction derived from the separate used lubricating oil introduced in the second blending step may be 3 to 50% of the volume of the second blend. For example, the fraction derived from the separate used lubricating oil introduced in the second blending step may be about 5 to 45%, about 5 to 40%, about 5 to 35%, about 5 to 30%, about 5 to 25%, about 5 to 20%, about 5 to 15%, about 5 to 10%, about 7 to 40%, about 7 to 35%, about 7 to 25%, about 7 to 20% of the volume of the second blend. It may be preferably about 7 to 15%, more preferably about 7 to 10%. The fraction derived from the pretreated separate used lubricating oil contains almost no wax components, and therefore has a low pour point of -18°C to -3°C as described above. When blended with the second fraction containing unconverted oil having a high pour point of about 42°C, the fluidity of the blended raw material increases and it is easy to transport at low temperatures. However, when the blending amount of the fraction derived from the separate used lubricating oil is less than 3% by volume, the fluidity increase effect is not large, and it is not easy to transport at each step of the process. When the blending amount of the fraction derived from the separate used lubricating oil exceeds 50% by volume, the impurities contained in the fraction derived from the pretreated waste lubricating oil and the low viscosity index may make the blended raw material unsuitable for use as a raw material for producing lubricating base oil.

[0039] In one embodiment, the method may further include catalytically dewaxing the second blend, which selectively isomerizes the wax components contained in the second blend to improve low temperature properties (ensuring a low pour point) and maintain a high viscosity index (VI). The present disclosure seeks to achieve improved efficiency and yields by improving the catalyst used in the catalytic dewaxing step.

[0040] In general, the main reaction of catalytic dewaxing is to convert N-paraffins to iso-paraffins by isomerization to improve low-temperature properties, and it has been reported that the catalysts used here are mainly bifunctional catalysts. Bifunctional catalysts are composed of two active components: a metal active component (Metal Site) for hydrogenation / dehydrogenation reactions and a support (Acid Site) having an acid site for skeletal isomerization via carbenium ions, while zeolite-structured catalysts are generally composed of an aluminosilicate support and at least one metal selected from Group 8 and Group 6 metals.

[0041] The dewaxing catalyst usable in the present disclosure comprises a support having an acid site selected from molecular sieves, alumina and silica-alumina, and at least one metal having a hydrogenation function selected from elements of Groups 2, 6, 9 and 10 of the periodic table, with Co, Ni, Pt and Pd being preferred among the Groups 9 and 10 (i.e., Group VIII) metals, and Mo and W being preferred among the Group 6 (i.e., Group VIB) metals.

[0042] The types of carriers having acid sites include molecular sieves, alumina, silica-alumina, etc., among which molecular sieves refer to crystalline aluminosilicates (zeolites), SAPO, ALPO, etc., and medium pore molecular sieves having 10-membered oxygen rings, such as SAPO-11, SAPO-41, ZSM-11, ZSM-22, ZSM-23, ZSM-35, ZSM-48, etc., and large pore molecular sieves having 12-membered oxygen rings can be used.

[0043] In particular, in the present disclosure, it is preferable to use EU-2 zeolite with a controlled degree of phase transition as the carrier. If the synthesis conditions are changed after the pure zeolite is produced, or if the synthesis is continued for a certain period of time even if the hydrothermal synthesis conditions are the same, the synthesized zeolite crystals may gradually undergo a transition to a more stable phase. This phenomenon is called zeolite phase transformation, and it has been confirmed that the isomerization selectivity is improved according to the degree of the phase transformation of the zeolite, and that the catalyst dewaxing reaction using the zeolite can also exhibit excellent performance.

[0044] In one embodiment, the method may further include hydrofinishing the catalytically dewaxed second blend and recovering the product of the hydrofinishing step as lubricant base oil. Hydrofinishing corresponds to a step of improving the oxidation and UV stability of the second blend by removing aromatic compounds, olefins and solvents from the blend feed. The catalytically dewaxed second blend is hydrofinished in the presence of a hydrofinishing catalyst, which has the function of saturating unsaturated hydrocarbons contained in the catalytically dewaxed second blend to improve color and storage stability. In one embodiment, the hydrofinishing catalyst may be the same as the dewaxing catalyst described above. The product of the hydrofinishing step can be separated by viscosity, and lubricant base oil having desired properties can be recovered therefrom.

[0045] Specifically, the lubricant base oil produced by the method can be a high-grade lubricant base oil having a grade of Group III or higher in the API classification described above. More specifically, the lubricant base oil can have a viscosity index of 120 or more, preferably 120-140, 120-135, 120-130, 120-125, 125-140, 125-135, 125-130, 130-140, and 130-135, and a degree of saturation of 90% or more, preferably 91% or more, 92% or more, 93% or more, 94% or more, 95% or more, 96% or more, 97% or more, 98% or more, and 99% or more.

[0046] Furthermore, the lubricating base oil may contain almost no impurities, such as sulfur, nitrogen, and chlorine, each of which is 1 ppm or less.

[0047] The lubricant base oil may have a Saybolt Color of 27 or more as measured by ASTM D156. If the Saybolt Color value is 27 or more, the lubricant base oil is treated as having the stability of Water White grade. Water White grade lubricant base oil has sulfur and nitrogen contents of less than 1 ppm, a saturation level of 99% or more, and an aromatic content of less than 1%, and corresponds to a lubricant base oil that is more stable than conventional API Group III lubricant base oils.

[0048] The lubricating base oil can show a UV260-350nm absorbance of 2.5 or less and a UV325nm absorbance of 0.7 or less, measured according to ASTM D2008. Here, the absorbance at wavelengths of 260-350nm indicates that the lubricating base oil contains components having 3 or more aromatic rings, and the absorbance at wavelengths of 325nm indicates that the lubricating base oil contains components having 3-7 aromatic rings. However, since the lubricating base oil has low absorbance at these wavelengths, it has a low aromatic content and therefore has high stability.

[0049] Preferred examples are presented below to aid in understanding the present disclosure. However, the following examples are provided merely to facilitate understanding of the present disclosure, and the present disclosure is not limited thereto.

[0050] Working Example Measurement of properties and characteristics of fuel oils and lubricant base oils produced according to an embodiment of the present disclosure Waste lubricating oil having a sulfur content of about 2000 ppm, a nitrogen content of about 1500 ppm, and a chlorine content of about 1500 ppm was centrifuged at a speed of about 300 rpm, and then distilled under atmospheric pressure and reduced pressure to obtain a refined fraction. The refined fraction was hydrotreated and hydrocracked.

[0051] The hydrocracked refinery fraction was then subjected to fractional distillation to obtain a fuel oil and an unconverted oil having different boiling points.

[0052] Similarly to the refined fraction, a fraction derived from a separate used lubricating oil that had been through atmospheric distillation and reduced pressure distillation steps was hydrotreated, and then blended with the unconverted oil in a volume ratio of 25 (fraction derived from a separate used lubricating oil):75 (unconverted oil), and subjected to vacuum distillation, catalytic dewaxing and hydrofinishing to obtain a lubricating base oil. Here, the atmospheric distillation was carried out at a temperature of 50°C to 350°C and under atmospheric pressure. The process conditions for the reduced pressure distillation are shown in Table 2 below.

[0053] [Table 2] The process conditions for the hydrotreatment are shown in Table 3 below.

[0054] [Table 3]

[0055] The catalytic dewaxing is carried out at a temperature of 300°C and a pressure of 150 kg / cm 2 The hydrogenation was carried out under a pressure of 0.84, in the presence of a hydrogenation catalyst supported by EU-2 zeolite. The lubricant base oil produced by the above-mentioned process was measured for its properties and various characteristics. As a result of the measurements, the lubricant base oil had a specific gravity of 0.84, a kinematic viscosity at 100°C of 7.3 cSt, a viscosity index (VI) of 129, and a kinematic viscosity at -33°C, and contained sulfur, nitrogen, and chlorine contents each less than 1 ppm, and contained almost no impurities except for unavoidable trace amounts. In addition to the above, the properties measured for the lubricant base oil are as shown in Table 4 below.

[0056] [Table 4]

[0057] The lubricant base oil was found to have a viscosity index of at least 120 and a saturates of at least 95%, thereby meeting the criteria for Group III lubricant base oil in Table 1. The lubricant base oil had a bright and clean color when evaluated by the naked eye and exhibited a Saybolt Color of at least 27 as measured in accordance with ASTM D156. That is, the lubricant base oil is a water-white grade lubricant base oil and has high thermal stability at high temperatures.

[0058] In addition, the lubricating base oil exhibits a low absorbance of up to 3.0 (up to 1.0 for a wavelength of 325 nm) measured in accordance with ASTM D2008 for UV having a wavelength of 260 to 350 nm, particularly for UV having a wavelength of 325 nm, and therefore high stability against UV can be confirmed.

[0059] Thus, when fractions derived from waste lubricating oils are blended with unconverted oils and used as feedstock for the production of lubricating base oils, the stability and yield of the final lubricating base oil can be increased.

Claims

1. A method for recycling waste lubricating oil, comprising the steps of: Providing a fraction derived from used lubricating oil; A step of pretreating the fraction derived from the used lubricating oil; and hydrocracking a fraction derived from the pretreated used lubricating oil.

2. 2. The method for recycling used lubricating oil according to claim 1, wherein the fraction derived from the used lubricating oil has a kinematic viscosity measured at 40°C of 20 cst to 60 cst and a pour point of less than 0°C.

3. 2. The method for recycling used lubricating oil according to claim 1, wherein the pre-treating step comprises a step of solvent extraction of a fraction derived from the used lubricating oil.

4. 2. The method for recycling used lubricants according to claim 1, further comprising a first blending step of blending the fraction derived from the used lubricants with a hydrocarbon feedstock to produce a first blend prior to the hydrocracking step.

5. 5. The method for recycling used lubricating oil according to claim 4, wherein the first blend contains 1 to 10% by volume of the fraction derived from used lubricating oil.

6. 2. The method for recycling used lubricating oil according to claim 1, wherein the method further comprises recovering a plurality of fractions from the product of the hydrocracking step, the fractions including a first fraction and a second fraction.

7. 7. The method of recycling used lubricating oil according to claim 6, wherein the first fraction has a boiling point in the fuel oil boiling range.

8. 7. The method for recycling used lubricating oil according to claim 6, wherein the boiling point of the second fraction is higher than the boiling point of the first fraction.

9. 7. The method for recycling used lubricants according to claim 6, further comprising a second blending step of blending the second fraction with another fraction derived from used lubricants to produce a second blend.

10. The method for recycling used lubricating oil according to claim 9, wherein the fraction derived from the separate used lubricating oil introduced into the second blending step is 3 to 50% by volume of the second blend.

11. 10. The method of recycling used lubricating oil according to claim 9, wherein the method further comprises catalytically dewaxing the second formulation.

12. The method includes the steps of hydrofinishing the catalytically dewaxed second blend; 12. The method of recycling used lubricants according to claim 11, further comprising the step of recovering the product of the hydrofinishing step as lubricant base oil.

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