METHOD FOR PRODUCING RECYCLED LUBRICATING BASE OIL FROM WASTE LUBRICATING OIL AND RECYCLED LUBRICATING BASE OIL PRODUCED THEREBY

Abstract

According to an embodiment, a method for producing a recycled lubricating base oil from waste lubricating oil is proposed, the method including a) first pretreating the waste lubricating oil, b) performing distillation to recover a fraction having a specific boiling point from the first pretreated waste lubricating oil, c) second pretreating the fraction recovered in the distillation operation, and d) hydroprocessing the second pretreated fraction in the presence of a catalyst. The recycled lubricating base oil produced by the above method has a viscosity index (VI) equal to or greater than 130. The proposed method makes it possible to produce a high-grade lubricating base oil using only waste lubricating oil as a feed, thereby reducing the cost of raw materials for production of lubricating base oil, and having the advantage of being environmentally friendly.

Claims

1. A method for producing a recycled lubricating base oil from waste lubricating oil, the method comprising: a first pretreating operation performed on the waste lubricating oil to form a first pretreated waste lubricating oil; subjecting the first pretreated waste lubricating oil to a distillation operation to recover a fraction of the first pretreated waste lubricating oil having a specific boiling point; a second pretreating operation performed on the recovered fraction of the first pretreated waste lubricating oil recovered in the distillation operation to form a second pretreated fraction of the waste lubricating oil; and a hydroprocessing operation performed on the second pretreated fraction of the waste lubricating oil in the presence of a catalyst to produce a recycled lubricating base oil having a viscosity index (VI) equal to or greater than 130.

2. The method of claim 1, wherein the waste lubricating oil prior to the first pretreating operation has a viscosity index of equal to or less than 120, a sulfur content of equal to or greater than 10,000 ppm, and a nitrogen content equal to or greater than 300 ppm.

3. The method of claim 1, wherein the first pretreating operation comprises a coagulant addition process, a centrifugal separation process, or a combination thereof.

4. The method of claim 1, wherein the distillation operation comprises an atmospheric distillation, a vacuum distillation, or a combination thereof.

5. The method of claim 1, wherein the second pretreating operation comprises solvent extraction.

6. The method of claim 1, wherein in the hydroprocessing operation, a proportion of an unsupported catalyst in the catalyst is 20% to 70% by volume based on the total volume of the catalyst.

7. The method of claim 1, wherein the catalyst comprises a metal including Ni, W, Mo, Co, or a combination thereof.

8. A recycled lubricating base oil having a sulfur content equal to or less than 5 ppm, a saturation equal to or greater than 90%, and a viscosity index (VI) equal to or greater than 130.

9. The recycled lubricating base oil of claim 8, wherein the recycled lubricating base oil has a kinematic viscosity of 4 to 5 cSt at 100 C. and a pour point equal to or less than 15 C.

10. A recycled lubricating base oil obtained by the method of claim 1, wherein the recycled lubricating oil has a sulfur content equal to or less than 5 ppm, and a saturation equal to or greater than 90%.

11. The recycled lubricating base oil of claim 10 further having a viscosity index (VI) equal to or greater than 130.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and other objectives, features, and other advantages of the embodiments of the present disclosure will be more clearly understood from the following detailed description when taken in conjunction with the accompanying drawings, in which:

[0024] FIG. 1 is a simplified process flow schematic illustrating a method for producing a recycled lubricating base oil from waste lubricating oil according to an embodiment of the present disclosure.

[0025] FIG. 2 is a flowchart with the key operations of the method according to an embodiment.

DETAILED DESCRIPTION

[0026] Hereinbelow, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, disclosed herein are specific embodiments that illustrate the principles of the present disclosure, and it should be emphasized that the present disclosure is not limited to the specific embodiments illustrated.

[0027] As used herein, the term recycled lubricating oil refers to a lubricating base oil produced using only waste lubricating oil as a feed without mixing with a separate fraction such as unconverted oil(UCO) supplied from an external source.

[0028] According to the embodiments of the present disclosure, there is provided a method for producing a recycled lubricating base oil from waste lubricating oil. As shown in FIG. 2, the method including: [0029] a first pretreating operation (210) performed on the waste lubricating oil to form a first pretreated waste lubricating oil; [0030] subjecting the first pretreated waste lubricating oil to a distillation operation (220) to recover a fraction of the first pretreated waste lubricating oil having a specific boiling point; [0031] a second pretreating operation (230) performed on the recovered fraction of the first pretreated waste lubricating oil recovered in the distillation operation to form a second pretreated fraction of the waste lubricating oil; and [0032] a hydroprocessing operation (240) performed on the second pretreated fraction of the waste lubricating oil in the presence of a catalyst to produce a recycled lubricating base oil having a viscosity index (VI) of equal to or greater than 130.

[0033] The first pretreating of the waste lubricating oil includes reducing the content of impurities present in the waste lubricating oil. The content of impurities may be reduced in subsequent operations of the method for producing the recycled lubricating base oil according to the present disclosure. However, by reducing the content of impurities in the waste lubricating oil in advance in the pretreatment operation, the burden on the subsequent operations may be reduced, and the content of impurities may be further reduced compared to when the first pretreatment is not performed.

[0034] According to an embodiment, the waste lubricating oil prior to the first pretreating operation may have a viscosity index of equal to or less than 120, a sulfur content of equal to or greater than 10,000 ppm, and a nitrogen content of equal to or greater than 300 ppm. As described above, waste lubricating oil including base oil belonging to Group I in the above API classification may also be used as a feed for the method for producing the recycled lubricating base oil according to the present disclosure, and may be converted into a Group III+recycled base oil through a series of operations. This not only reduces the manufacturing cost of high-grade recycled base oils, but also has an advantage in terms of environmental friendliness by recycling waste lubricating oil that can no longer be recycled and needs to be discarded. Waste lubricating oil having a viscosity index greater than the above viscosity index and lower sulfur and nitrogen contents, i.e., waste lubricating oil including base oils belonging to Group II and Group III in the API classification, may also be used as a feed for the method for producing the recycled lubricating base oil according to the present disclosure.

[0035] According to an embodiment, the first pretreating operation may include a coagulant addition, a centrifugal separation, or a combination thereof. The coagulant addition may include coagulating sulfur, nitrogen, chlorine, and other impurities present in the waste lubricating oil to form aggregates and separating them from fractions by density differences. Any coagulant that is suitable for coagulating impurities in the waste lubricating oil may be used without limitation. For example, the coagulant may include Alum. Alum is a well-known coagulant and refers to a group of compounds including, for example, aluminum sulfate (Al.sub.2(SO.sub.4).sub.3). The centrifugal separation includes separating and removing impurities present in the waste lubricating oil through precipitation, and may be performed at a rotation speed of about 100 to 3,000 rpm. Instead of the centrifugal separation, precipitation of impurities by natural sedimentation is also possible, but the centrifugal separation is more preferable from the perspective of separation speed and performance. The coagulant addition and the centrifugal separation may be performed in combination. Specifically, when the centrifugal separation is performed on the waste lubricating oil after the coagulant addition, the time required for formation of impurity aggregates may be shortened, and the formed impurity aggregates may be more completely removed by precipitation.

[0036] The method includes performing distillation to recover a fraction having a specific boiling point from the first pretreated waste lubricating oil. The distillation operation includes obtaining a fraction having a desired viscosity index and kinematic viscosity from the waste lubricating oil. In the distillation operation, fractions in the first pretreated waste lubricating oil are distilled and fractionated according to their boiling points with the ones with the lower boiling points being fractionated first as the atmospheric distillation temperature increases.

[0037] According to an embodiment, the distillation operation may include atmospheric distillation, vacuum distillation, or a combination thereof.

[0038] The atmospheric distillation may be performed at a temperature of about 50 C. to 350 C. under atmospheric pressure. As the atmospheric distillation temperature increases, fractions in the waste lubricating oil are distilled and fractionated according to their boiling points with the ones with the lower boiling points being fractionated first. Among the fractions fractionated through the atmospheric distillation operation, a fraction having a boiling point of about equal to or greater than 150 C. is collected to produce a refined oil fraction.

[0039] The fraction collected in the atmospheric distillation is then subjected to the vacuum distillation. The vacuum distillation is performed for further fractionation of the fraction obtained in the atmospheric distillation. When the distillation temperature is increased for the fractionation of the fraction under atmospheric pressure, oil fraction cracking may occur. For this reason, this operation is performed in reduced pressure and mild temperature conditions. The vacuum distillation may be performed at a pressure of equal to or less than 10 torr and a temperature of 150 C. to 600 C. During the vacuum distillation, a fraction having a boiling point of 300 C. to 550 C. is collected and is referred to as a refined oil fraction. The refined oil fraction has a kinematic viscosity of about 4 to 6 cSt at a temperature of 100 C., a viscosity index (VI) of about 90 to 123, and a pour point of about 20 C. to 0 C. Additionally, the refined oil fraction may have a sulfur content of about 200 to 2,000 ppm, a nitrogen content of about 100 to 1,000 ppm, and a chlorine content of about 30 to 2,000 ppm. That is, the refined oil fraction may have a reduced impurity content compared to the first pretreated waste lubricating oil. The refined oil fraction shows a brown color of about 5 to 6 according to ASTM standards. By the centrifugal separation and the two-step distillation (also referred to as a two-part or two-operation distillation), the refined oil fraction may have a sediment and moisture content that is significantly reduced compared to the waste lubricating oil prior to the pretreatment and distillation operations.

[0040] The method includes a second pretreating operation of the fraction recovered in the distillation operation to remove impurities. The second pretreating operation includes additionally treating the fraction (refined oil fraction)recovered in the distillation operation to minimize the influence of the refined oil fraction on the process and the catalyst before the refined oil fraction is subjected to hydroprocessing.

[0041] According to an embodiment, the second pretreating operation may include solvent extraction. The solvent extraction may include blending the refined oil fraction and a solvent in a blending tank, allowing the mixture to settle to reach phase separation, thereby obtaining a phase in which oil is a main component, and removing a phase containing a large amount of impurities. The solvent used for the solvent extraction should have a higher affinity to impurities than the oil component in the refined oil fraction. Examples of suitable solvents include N-methyl-2-pyrrolidone (NMP), sulfolane, dimethyl sulfoxide (DMSO), furfural, phenol, and acetone. Since the solvent has a high affinity to impurities and a low affinity to the oil component in the refined oil fraction, the solvent is phase-separated from the oil component in the refined oil fraction. Any solvent may be used without limitation as long as it has a different volatility for the subsequent solvent separation operation. According to an embodiment, the solvent extraction may be performed in a batch or continuous process configuration, and may be performed at a temperature of about 60 C. to 80 C., a solvent-oil ratio of about 1.5:1 to 2.5:1 by volume, and a stirring speed of about 400 to 700 rpm. Additionally, for reducing the impurity content in the refined oil fraction to a desired level, the layer containing a large amount of impurities located at the bottom after settling and phase separation may be removed, and the solvent extraction may be performed repeatedly by additionally adding a solvent. After the impurity content in the refined oil fraction is reduced to the desired level, water is added to the refined oil layer to phase-separate and remove a polar solvent.

[0042] The method includes hydroprocessing the second pretreated fraction in the presence of the catalyst. The hydroprocessing may include hydrogenating the second pretreated fraction at high temperature and high pressure in the presence of the catalyst to remove sulfur, nitrogen, and other metallic impurities contained in the fraction derived from the waste lubricating oil, and saturating unsaturated hydrocarbons present in the fraction derived from the waste lubricating oil. Through the hydroprocessing operation, a recycled lubricating base oil is obtained. The obtained recycled lubricating base oil has an improved viscosity index compared to existing Group III lubricating oils, and exhibits a viscosity index equal to or greater than 130.

[0043] According to an embodiment, in the hydroprocessing operation, the proportion of an unsupported catalyst in the catalyst may be 20% to 70% by volume based on the total volume of the catalyst. Unlike conventional hydrocracking catalysts, unsupported catalysts without a separate support have a structural feature and configuration that suppress the cracking function and maximize the hydrogenation function that saturates unsaturated hydrocarbons, thereby having particular advantages in improving the viscosity index by removing impurities in the second pretreated fraction and increasing the paraffin content. When the proportion of the unsupported catalyst in the catalyst is less than 20%, the hydrogenation function of the catalyst may not be sufficient to achieve a viscosity index equal to or greater than 130. When the proportion of the unsupported catalyst in the catalyst exceeds 70%, the metal content in the catalyst is inevitably high, which may be disadvantageous in terms of cost, and the cracking performance of the catalyst may low, so impurities in the fraction may not be removed efficiently. According to an embodiment, the proportion of the unsupported catalyst in the catalyst may be specifically 30% to 60%, more specifically 40% to 50% by volume.

[0044] According to an embodiment, the catalyst may include a metal. Suitable metals may include, for example, Ni, W, Mo, Co, or a combination thereof. In the catalyst, the metal acts as an active site and promotes a hydrogenation reaction of a feed. More specifically, the metal included in the catalyst may be in the form of a metal oxide, and may be an oxide of Ni, W, Mo, and Co, which exhibit excellent hydrogenation function among metal oxides. The metal may be included in the catalyst in combination, for example, in a combination of Ni/W/Mo or Co/W/Mo.

[0045] According to an embodiment, the method may further include performing dewaxing and performing hydrofinishing. The main reaction in the dewaxing operation is isomerization, which converts N-paraffin to iso-paraffin to improve the low-temperature properties of the recycled lubricating base oil. For this reason, the dewaxing operation may also be referred to as isodewaxing (IDW). The dewaxing may be performed in the presence of a zeolite-based precious metal catalyst.

[0046] The hydrofinishing may include allowing hydrogen gas and the recycled lubricating base oil to pass through a catalyst layer to remove trace amounts of impurities such as sulfur and nitrogen present in the recycled lubricating base oil as the final product. The catalyst layer may include an alumina-based precious metal catalyst. The hydrofinishing operation may be performed at a temperature of about 200 C. to 250 C. and a liquid hourly space velocity (LHSV) of 0.5 to 2.0 h.sup.1.

[0047] Various properties of a feed after each operation of the method for producing the recycled lubricating base oil from the waste lubricating oil are as illustrated in Table 2 below.

TABLE-US-00002 TABLE 2 Waste Refined Lubricating lubricating oil Solvent base oil fraction extraction Hydrogenation oil Specific gravity 0.8 to 0.9 0.8 to 0.9 0.8 to 0.9 0.8 to 0.9 0.8 to 0.9 Kinematic 2 to 20 4 to 6 4 to 6 4 to 5 4 to 5 viscosity (@ 100 C.), cSt Viscosity index 60 to 150 100 to 120 110 to 130 130 to 140 >130 Pour point ( C.) 18 to 12 18 to 3 18 to 3 18 to 3 Equal to or less than 15 Sulfur, ppm 1000 to 3000 200 to 1000 70 to 150 0 to 5 Equal to or less than 1 Nitrogen, ppm 500 to 2000 200 to 400 40 to 100 0 to 1 Equal to or less than 1 Chlorine, ppm 100 to 2000 30 to 2000 5 to 20 0 to 1 Equal to or less than 1 Aromatic Equal to 0 to 10 0 to 5 0 to 1 Equal to or compound, or greater less than 1 wt % than 10%

[0048] By the above method, a recycled lubricating base oil having a viscosity index (VI) of equal to or greater than 130 may be produced using only waste lubricating oil as a feed.

[0049] According to the embodiments of the present disclosure, there is provided a recycled lubricating base oil having a sulfur content of equal to or less than 5 ppm, a saturation of equal to or greater than 90%, and a viscosity index (VI) of equal to or greater than 130. The recycled lubricating base oil may be produced using only waste lubricating oil as a feed, according to the above method for producing the recycled lubricating base oil. The recycled lubricating base oil satisfies the conditions required for Group III in the API classification in terms of sulfur content and saturation, and its viscosity index is significantly greater than the Group III criteria, so it corresponds to the Group III+ lubricating base oil described above.

[0050] According to an embodiment, the recycled lubricating base oil may have a kinematic viscosity of 4 to 5 cSt at 100 C. and a pour point of equal to or less than 15 C. The recycled lubricating base oil has a viscosity required for Group III and Group III+ as described above, and has a low pour point to maintain fluidity even at low temperature, thereby exhibiting excellent performance as a lubricating base oil.

[0051] Hereinbelow, the embodiments of the present disclosure will be further described with reference to specific experimental examples. Examples and comparative examples included in the experimental examples are only illustrative of the present disclosure and are not intended to limit the scope of the appended claims. It will be apparent to those skilled in the art that various changes and modifications to the examples are possible within the scope and spirit of the present disclosure, and that such changes and modifications fall within the scope of the appended claims.

ExampleConfirmation of Change in Viscosity Index of Recycled Lubricating Base Oil According to Catalyst

Experimental Example

[0052] According to the simplified process flow schematic illustrated in FIG. 1, Alum 10 was added as a coagulant to waste lubricating oil having a specific gravity of 0.8, a kinematic viscosity of 4 cSt at 100 C., a viscosity index of 100, a sulfur content of 2,500 ppm, a nitrogen content of 1,800 ppm, and a chlorine content of 1,500 ppm, and the mixture was allowed to be pretreated (settled) for 30 minutes in a settling tank 50, thereby precipitating and removing aggregates of sulfur, nitrogen, chlorine, and other impurities in the waste lubricating oil. Thereafter, the pretreated waste lubricating oil was distilled in an ADU (Atmospheric Distillation Unit) 100 at a temperature of 50 C. to 350 C. under atmospheric pressure to collect a fraction having a boiling point equal to or greater than 150 C. The collected fraction was subjected to vacuum distillation in a vacuum distillation Unit (VDU) 200 at a pressure of 5 torr and a temperature of 150 C. to 600 C. In this operation, a fraction having a boiling point of 300 C. to 550 C. was collected. The fraction refined oil collected from the VDU 200 was subjected to solvent extraction using N-methyl-2-pyrrolidone (NMP) as a solvent in a solvent extraction unit 300. The solvent extraction was performed at atmospheric pressure and a temperature of 70 C., with a solvent-oil ratio (SOR) of 1.5. The fraction with reduced impurity content by the solvent extraction (also referred to as the solvent extracted oil) was subjected to hydroprocessing in a hydroprocessing reactor 400 loaded with 70% by volume of an unsupported catalyst and 30% by volume of a supported catalyst with a support. The hydroprocessing was performed at a pressure of 160 kg/cm.sup.2 and a temperature of 380 C. The hydroprocessed fraction was then subjected to isodewaxing (IDW) 500 and hydrofinishing (HDF) 600 to obtain a recycled lubricating base oil 700. For the thus obtained recycled lubricating base oil 700 of the Experimental Example, the properties before isodewaxing (semi-product) are as illustrated in Table 3 below, and the properties after isodewaxing and hydrofinishing (prototype product) are as illustrated in Table 4 below.

TABLE-US-00003 TABLE 3 100D KV 100 C., cSt 4,069 VI/PP ( C.) 133/6

TABLE-US-00004 TABLE 4 4 cSt prototype product (CDW reaction preparation) KV 100 C., cSt 4.15 VI 132 PP, ( C.) 18

Comparative Experimental Example

[0053] Another recycled lubricating base oil was obtained under the same feed and process conditions as in Experimental Example, except that the proportion of the supported catalyst was 100% by volume and the unsupported catalyst was excluded in the hydroprocessing operation. The properties of the thus obtained recycled lubricating base oil (prototype product) of Comparative Experimental Example are as illustrated in Table 5 below.

TABLE-US-00005 TABLE 5 Properties of prototype product Kinematic Viscosity @ 20.56 40 C., cSt Kinematic Viscosity @ 4.266 100 C., cSt Viscosity Index 113 Pour Point, C. 18 S/N/Cl, ppm 1/1/2 Metal, ppm Trace

[0054] The prototype products of the Experimental Example and the Comparative Experimental Example were similar in other properties, but the viscosity index of the prototype product of Experimental Example exceeded 130, while that of the prototype product of Comparative Experimental Example was only 113, showing a large difference caused by the proportion of the unsupported catalyst in the catalyst used in the hydroprocessing operation.

[0055] The above description is merely illustrative of the applications of the embodiments of the present disclosure, and other variants and modifications of the embodiments will be apparent to those skilled in the art. Furthermore, the embodiments may be combined to form additional embodiments.