Method of producing reclaimed lubricating base oil from waste lubricating oil, and reclaimed lubricating base oil produced thereby

Abstract

To provide a method of producing reclaimed lubricating base oil from waste lubricating oil, and reclaimed lubricating base oil produced thereby.SOLUTION: There is provided a method of producing reclaimed lubricating base oil from waste lubricating oil according to an embodiment of the present invention, including: a) a step of subjecting waste lubricating oil to a first pretreatment; b) a distillation step for recovering a fraction of a specific boiling point present in the waste lubricating oil having been subjected to the first pretreatment; c) a step of subjecting the fraction recovered by the distillation step to a second pretreatment; and d) a step of subjecting the fraction having been subjected to the second pretreatment to a hydrogenation process in the presence of a catalyst. The reclaimed lubricating base oil produced according to the method described above, has a viscosity index (VI) of 130 or more. The method according to the present disclosure can reduce the cost of the raw material for producing the lubricating base oil by being capable of using waste lubricating oil alone as a feed stock to manufacture high-quality lubricating base oil and can have an advantage of being environmentally friendly.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing reclaimed lubricant base oil from waste lubricant oil, and the reclaimed lubricant base oil produced thereby. [Background technology]

[0002] The American Petroleum Institute (API) classifies grades of mineral-based base oils derived from crude oil according to saturates, sulfur content, and Viscosity Index (VI), as shown in Table 1 below.

[0003] [Table 1]

[0004] Among these, base oils that meet all Group III criteria and have a viscosity index of 130 or higher, even though they are not included in the classification criteria, are classified as Group III+ base oils in order to differentiate them from existing Group III base oils with a viscosity index of 120 or higher, and are generally treated as having superior performance compared to Group III base oils in the global market, and are traded at higher prices. Global environmental regulations and responses to them are calling for improved fuel economy and electricity efficiencies using premium lubricants, and as a result, demand for high-performance Group III+ base oils is expected to continue to increase. Summary of the Invention [Problem to be solved by the invention]

[0005] According to one aspect of the present disclosure, it is an object to provide a method for producing reclaimed lubricant base oils with improved viscosity index performance. [Means for solving the problem]

[0006] According to the present disclosure, there is provided a method for producing reclaimed lubricant base oil from used lubricant oil, the method comprising: a) a first pre-treatment step of the used lubricant oil; b) a distillation step for recovering a fraction of a specific boiling point from the first pre-treated used lubricant oil; c) a second pre-treatment step of the fraction recovered in the distillation step; and d) a hydrotreating step of the second pre-treated fraction in the presence of a catalyst, wherein the reclaimed lubricant base oil has a viscosity index (VI) of 130 or greater.

[0007] According to one embodiment, the used lubricating oil before being introduced into step a) may have a viscosity index of 120 or less, a sulfur content of 10,000 ppm or more, and a nitrogen content of 300 ppm or more.

[0008] According to one embodiment, step a) may comprise flocculant dosing, centrifugation, or a combination thereof.

[0009] According to one embodiment, step b) may comprise atmospheric distillation, vacuum distillation, or a combination thereof.

[0010] According to one embodiment, step c) may comprise solvent extraction.

[0011] According to one embodiment, in step d), the proportion of unsupported catalyst in the catalyst may be 20% to 70% by volume.

[0012] According to one embodiment, the catalyst comprises a metal, which may comprise Ni, W, Mo, Co, or a combination thereof.

[0013] According to the present disclosure, a reclaimed lubricant base oil is provided that includes a sulfur content of 5 ppm or less, a saturates level of 90% or greater, and a viscosity index (VI) of 130 or greater.

[0014] According to one embodiment, the reclaimed lubricant base oil may have a kinematic viscosity of 4-5 cSt at 100° C. and a pour point of −15° C. or less. [Effects of the Invention]

[0015] According to one embodiment of the present disclosure, Group III lubricant base oils with improved viscosity index can be produced in an environmentally friendly manner. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a process flow diagram of a method for producing reclaimed lubricant base oil from used lubricant oil according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present disclosure will now be described in detail with reference to the accompanying drawings, which are merely illustrative and are not intended to limit the present disclosure to the specific embodiments described by way of example.

[0018] As used herein, the term "reclaimed lubricant base oil" refers to a lubricant base oil produced solely from waste lubricant oil without blending with any other fraction, such as externally supplied unconverted oil (UCO).

[0019] According to the present disclosure, there is provided a method for producing reclaimed lubricant base oil from used lubricating oil, the method comprising: a) a first pre-treatment step of the used lubricating oil; b) a distillation step for recovering a fraction of a specific boiling point from the first pre-treated used lubricating oil; c) a second pre-treatment step of the fraction recovered in the distillation step; and d) a hydrotreating step of the second pre-treated fraction in the presence of a catalyst.

[0020] The step of subjecting the used lubricant to the first pretreatment (step a) is a step for reducing the content of impurities present in the used lubricant. Although the content of impurities can also be reduced in the subsequent process steps of the method for producing recycled lubricant base oil of the present disclosure, by reducing the content of impurities in the used lubricant in advance in the first pretreatment step, the burden on the subsequent process steps can be reduced, and the content of impurities can be further reduced compared to when the first pretreatment is not performed.

[0021] In one embodiment, the used lubricant before being introduced into step a) can have a viscosity index of 120 or less, a sulfur content of 10,000 ppm or more, and a nitrogen content of 300 ppm or more. Thus, used lubricants containing base oils belonging to API Group I can also be used as feed for the reclaimed lubricant base oil production method of the present disclosure. By converting this used lubricant into Group III+ reclaimed base oil through a series of steps, not only can the production cost of high-quality reclaimed base oil be reduced, but also the reclaimed used lubricant, which is no longer reclaimable and must be discarded, can be recycled, which is advantageous from an environmental perspective. Used lubricants with a higher viscosity index and lower sulfur and nitrogen content than the above, i.e., used lubricants containing base oils belonging to API Group II and Group III, can also be used as feed for the reclaimed lubricant base oil production method of the present disclosure.

[0022] In one embodiment, step a) may include coagulant addition, centrifugation, or a combination thereof. Coagulant addition is a method of coagulating sulfur, nitrogen, chlorine, and other impurities present in the used lubricant to form coagulates, which are then separated from the fraction due to density differences. Any coagulant can be used as long as it can coagulate impurities in the used lubricant. For example, the coagulant added may be alum. Centrifugation is used to separate and remove impurities present in the used lubricant through precipitation, and may be performed at a rotation speed of approximately 100 rpm to 3000 rpm. While natural precipitation of impurities is also possible instead of centrifugation, centrifugation is preferred from the perspective of separation speed and performance. Coagulant addition and centrifugation may be performed in combination. Specifically, centrifuging the used lubricant after coagulation can shorten the time required for impurity coagulation formation, and the formed impurity coagulates can be more completely removed by precipitation.

[0023] This method includes a distillation step (step b) for recovering a fraction of a specific boiling point from the first pre-treated used lubricating oil. Step b corresponds to a distillation step for obtaining a fraction having a desired viscosity index and kinematic viscosity from the used lubricating oil. In the distillation step, the fractions from the first pre-treated used lubricating oil are distilled and fractionated in ascending order of boiling point as the distillation temperature increases.

[0024] In one embodiment, step b) can include atmospheric distillation, vacuum distillation, or a combination thereof.

[0025] Atmospheric distillation is carried out at atmospheric pressure at a temperature of about 50°C to 350°C, and as the atmospheric distillation temperature increases, the fractions in the first pre-treated waste lubricating oil are distilled and separated in ascending order of boiling point. Among the fractions separated in the atmospheric distillation step, fractions having a boiling point of about 150°C or higher are collected to produce a refined fraction.

[0026] The fraction collected in the atmospheric distillation step is introduced into the subsequent vacuum distillation. This is for more detailed fractionation of the fraction obtained in the atmospheric distillation step. Since increasing the distillation temperature for detailed fractionation at atmospheric pressure can result in cracking of the fraction, it is carried out under reduced pressure and moderate temperature conditions. The vacuum distillation can be carried out at a pressure of 10 torr or less and at a temperature of 150 to 600°C. During the vacuum distillation step, a fraction having a boiling point of 300 to 550°C is collected and is called the refined fraction. The refined fraction can have 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 to 0°C. Furthermore, the refined fraction has a sulfur content of about 200-2000 ppm, a nitrogen content of about 100-1000 ppm, and a chlorine content of about 30-2000 ppm, and thus can have a reduced impurity content compared to the waste lubricating oil that has undergone the first pretreatment. The refined fraction exhibits a color close to brown, with an ASTM color of about 5-6. Due to the centrifugation and two-step distillation, the refined fraction can have a sediment and moisture content that is significantly reduced compared to the sediment and moisture content present in the waste lubricating oil before the first pretreatment and distillation steps.

[0027] The method further comprises a step (step c) of subjecting the fraction recovered in the distillation step to a second pretreatment to remove impurities, the second pretreatment being a step of further treating the fraction recovered in the distillation step (refined fraction) to minimize its influence on the process and catalyst prior to introducing the fraction into hydroprocessing.

[0028] In one embodiment, step c) can include solvent extraction. Solvent extraction involves mixing a purified fraction with a solvent in a mixing vessel, allowing the mixture to stand for phase separation, resulting in a phase containing the fraction to be obtained as a main component, and removing a phase containing a large amount of impurities. The solvent used in the solvent extraction is a solvent that has a higher affinity for impurities than for the oil components in the purified fraction. Common solvents include N-Methyl-2-Pyrrolidone (NMP), sulfolane, DMSO, furfural, phenol, and acetone. The solvent can be used without limitation as long as it has a high affinity for impurities but a low affinity for the oil components in the purified fraction, allowing for phase separation from the oil components, and has a volatility difference that allows for subsequent solvent separation. In one embodiment, solvent extraction can be performed in a batch or continuous process configuration, at a temperature of about 60-80°C, a solvent-to-oil ratio of about 1.5:1-2.5:1 by volume, and an agitation speed of about 400-700 rpm. To reduce the impurity content in the purified fraction to a desired level, the solution can be allowed to stand, followed by separating and removing the lower layer containing a large amount of impurities, and then adding additional solvent to repeat the solvent extraction. After the impurity content in the purified fraction has been reduced to a desired level, water is added to the purified fraction layer to cause phase separation and remove the polar solvent.

[0029] The method further includes a step (d) of hydrotreating the second pretreated fraction in the presence of a catalyst. Hydrotreating involves hydrogenating the second pretreated fraction at high temperature and pressure in the presence of a catalyst to remove sulfur, nitrogen, and other metal impurities contained in the fraction derived from used lubricating oil and to saturate unsaturated hydrocarbons present in the fraction derived from used lubricating oil, thereby improving the viscosity index. The hydrotreating step yields a reclaimed lubricant base oil, which exhibits a viscosity index of 130 or greater, a viscosity index that is significantly improved compared to existing Group III lubricant base oils.

[0030] In one embodiment, in step d), the proportion of the unsupported catalyst in the catalyst may be 20% to 70% by volume. Unlike existing hydrocracking catalysts, the unsupported catalyst, which does not have a separate support, has structural characteristics and configuration that suppress its cracking function and maximize its hydrogenation function of saturating unsaturated hydrocarbons. This provides particular advantages in removing impurities in the solvent-extracted fraction and improving the viscosity index by increasing the paraffin content. If 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 of 130 or higher. If the proportion of the unsupported catalyst in the catalyst is more than 70%, the metal content in the catalyst may be high, which may be disadvantageous in terms of cost. The cracking performance of the catalyst may be poor, preventing smooth impurity removal in the fraction. In one embodiment, the proportion of the unsupported catalyst in the catalyst may be specifically 30% to 60%, more specifically 40% to 50%.

[0031] In one embodiment, the catalyst includes a metal, and the metal may include Ni, W, Mo, Co, or a combination thereof. In the catalyst, the metal serves as an active site to promote the hydrogenation reaction of the feed. More specifically, the metal included in the catalyst may be in the form of a metal oxide, or may be an oxide of Ni, W, Mo, or Co, which has excellent hydrogenation function among metal oxides. The metals may be included in the catalyst in combination, for example, Ni / W / Mo or Co / W / Mo.

[0032] In one embodiment, the method may further include a dewaxing step and a hydrofinishing step. The main reaction in the dewaxing step is an isomerization reaction, which converts N-paraffins to iso-paraffins to improve the low-temperature properties of the recycled lubricant base oil. For this reason, the dewaxing step is sometimes referred to as isodewaxing (IDW). The dewaxing step may be carried out in the presence of a zeolite-based precious metal catalyst.

[0033] The hydrofinishing step is a process step in which hydrogen gas and recycled lubricant base oil are passed through a catalyst bed to remove trace amounts of impurities, such as sulfur and nitrogen, present in the final recycled lubricant base oil. The catalyst bed may contain an alumina-based precious metal catalyst, and the hydrofinishing step is carried out at a temperature of about 200-250°C for 0.5-2.0 hours. -1 This can be done under LHSV (Liquid Hourly Space Velocity).

[0034] Exemplary properties of the feed after each process step of the method for producing reclaimed lubricant base oil from waste lubricant oil described above are shown in Table 2 below.

[0035] [Table 2] By the above-described manufacturing method, reclaimed lubricant base oils with a viscosity index (VI) of 130 or higher can be produced using only waste lubricant oil as the feedstock.

[0036] According to the present disclosure, there is provided a reclaimed lubricant base oil having a sulfur content of 5 ppm or less, a saturates level of 90% or greater, and a viscosity index (VI) of 130 or greater. The reclaimed lubricant base oil may be produced by the aforementioned method for producing reclaimed base oil using only waste lubricant as a raw material. The reclaimed base oil satisfies the requirements of API Group III in sulfur content and saturates, and has a viscosity index significantly higher than the Group III standard, thereby falling under the aforementioned Group III+ lubricant base oil.

[0037] In one embodiment, the recycled lubricant base oil may have a kinematic viscosity of 4 to 5 cSt at 100° C. and a pour point of −15° C. or lower. The recycled lubricant base oil has a kinematic viscosity that can belong to Group III and Group III+ as described above, and a low pour point that allows it to maintain fluidity even at low temperatures, allowing it to exhibit excellent performance as a lubricant base oil.

[0038] The present invention will be further described below with reference to specific experimental examples. The examples and comparative examples included in the experimental examples are merely illustrative of the present invention and do not limit the scope of the appended claims. It is obvious to those skilled in the art that various changes and modifications to the examples can be made within the scope and technical spirit of the present invention, and it is natural that such changes and modifications also fall within the scope of the appended claims.

[0039] Example - Confirmation of change in viscosity index of recycled lubricant base oil by catalyst Experimental Example According to the process flow diagram shown in Figure 1, alum was added as a coagulant to waste lubricating oil (WLU) with a specific gravity of 0.8, a kinematic viscosity at 100°C of 4 cSt, a viscosity index of 100, a sulfur content of 2500 ppm, a nitrogen content of 1800 ppm, and a chlorine content of 1500 ppm. The oil was then allowed to settle for 30 minutes, allowing the sulfur, nitrogen, chlorine, and other impurities in the WLU to be removed by settling. The pretreated WLU was then distilled (ADU) at atmospheric pressure and temperatures of 50°C to 350°C, and the fraction with a boiling point above 150°C was collected. The collected fraction was then introduced into a vacuum distillation (VDU) at a pressure of 5 torr and temperatures of 150°C to 600°C. Here, the fraction with a boiling point between 300°C and 550°C was collected. The fraction collected in the distillation step was introduced into solvent extraction using NMP (N-Methyl-2-Pyrrolidone) as the solvent. Solvent extraction was carried out at atmospheric pressure and a temperature of ~70°C, with a solvent-to-fraction volume ratio (SOR) of 1.5. The fraction with reduced impurity content by solvent extraction was introduced into hydroprocessing in a reactor loaded with 70% by volume of unsupported catalyst and 30% by volume of supported catalyst. Hydroprocessing was carried out at a pressure of 160 kg / cm. 2 The hydrotreated fraction was then isodewaxed (IDW) and hydrofinished (HDF) to obtain recycled lubricant base oil. The properties of the recycled lubricant base oil of the experimental example obtained before isodewaxing (semi-finished product) are shown in Table 3 below, and the properties of the sample product after isodewaxing and hydrofinishing are shown in Table 4 below.

[0040] [Table 3]

[0041] [Table 4]

[0042] Comparative experiment example Another reclaimed lubricant base oil was obtained using the same feed and process conditions as the previous example, except that the proportion of supported catalyst in the hydrotreating step was 100% by volume and the unsupported catalyst was omitted. The properties of the reclaimed lubricant base oil (sample) of the comparative example are shown in Table 5 below.

[0043] [Table 5]

[0044] Although the samples of the Experimental Example and Comparative Example were similar in other properties, a large difference was observed in the viscosity index, with the sample of the Experimental Example exceeding 130 and the sample of the Comparative Example only having a viscosity index of 113. This is thought to be due to the difference in the proportion of unsupported catalyst in the catalyst used in the hydrotreatment step.

[0045] The foregoing is merely illustrative of the application of the principles of the present disclosure, and other arrangements may be included without departing from the scope of the present invention.

Claims

1. A method for producing reclaimed lubricant base oil from waste lubricant oil, comprising: a) subjecting used lubricating oil to a first pre-treatment; b) a distillation step for recovering a specific boiling point fraction from the first pre-treated used lubricating oil; c) a second pretreatment step of the fraction recovered in the distillation step; d) hydrotreating the second pretreated fraction in the presence of a catalyst, The method for producing a reclaimed lubricant base oil from waste lubricant oil, wherein the reclaimed lubricant base oil has a viscosity index (VI) of 130 or more.

2. 2. The method for producing reclaimed lubricant base oil from used lubricating oil according to claim 1, wherein the used lubricating oil before being introduced into step a) has a viscosity index of 120 or less, a sulfur content of 10,000 ppm or more, and a nitrogen content of 300 ppm or more.

3. 10. The method for producing reclaimed lubricant base oil from waste lubricant oil of claim 1, wherein step a) comprises flocculating, centrifuging, or a combination thereof.

4. 10. The method for producing reclaimed lubricant base oil from used lubricant oil of claim 1, wherein step b) comprises atmospheric distillation, vacuum distillation, or a combination thereof.

5. 10. The method for producing reclaimed lubricant base oil from waste lubricant oil of claim 1, wherein step c) comprises solvent extraction.

6. 2. The method for producing reclaimed lubricant base oil from waste lubricant oil according to claim 1, wherein in step d), the proportion of unsupported catalyst in the catalyst is 20% or more and 70% or less by volume.

7. 2. The method for producing reclaimed lubricant base oil from used lubricant oil according to claim 1, wherein the catalyst comprises a metal, and the metal comprises Ni, W, Mo, Co, or a combination thereof.

8. A reclaimed lubricating base oil comprising a sulfur content of 5 ppm or less, a saturates level of 90% or greater, and a viscosity index (VI) of 130 or greater.

9. 9. The reclaimed lubricant base oil of claim 8, wherein the reclaimed lubricant base oil comprises a kinematic viscosity of 4 to 5 cSt at 100°C and a pour point of -15°C or less.

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