Process for preparing naphthenic bright stocks from naphthenic feedstocks based on naphthenic deasphalted oils

Abstract

A process for preparing naphthenic bright stocks from naphthenic feedstocks based on naphthenic deasphalted oil (DAO) is disclosed. The method comprises a hydrotreatment step B which is subdivided into three independent steps: B1 low-pressure catalytic hydrotreatment, B2 high-pressure catalytic hydrotreatment and B3 catalytic dewaxing. The naphthenic bright stock exhibits a reduced viscosity and an increased viscosity index as compared to the naphthenic DAO feedstock, and the process allows a wider range of naphthenic DAO feedstocks to be used to make the naphthenic bright stock.

Description

Technical Field

[0001] The present invention relates generally to naphthenic bright stocks and, more particularly, to a process for preparing naphthenic bright stocks from naphthenic deasphalted oil (DAO) based naphthenic feedstocks, the naphthenic bright stocks exhibiting reduced viscosity and increased viscosity index compared to the feedstock, the process allowing a wider range of naphthenic DAO feedstocks to be used in the preparation of bright stocks. Background Art

[0002] Bright stocks are conventionally made from petroleum feedstocks that have been solvent deasphalted and then solvent refined or hydrotreated to provide modified oils with improved cleanliness or quality. Bright stocks are generally classified as either naphthenic or paraffinic. This classification is generally derived from the nature of the feedstocks used. The production of high-quality naphthenic bright stocks that are qualified for conventional bright stock applications requires careful selection of processing steps in order to meet target performance characteristics, particularly an appropriate viscosity range and a sufficiently high viscosity index (VI), as well as production costs.

[0003] CN104449841A teaches that bright oil is a high-viscosity lubricating base oil widely used in the production of marine engine oil, single-grade and advanced multi-grade engine oil, internal combustion engine oil, heavy-duty gear oil, various greases, etc. Bright oil is classified into 90BS, 120BS and 150BS. Among them, the kinematic viscosity of 90BS bright oil at 100°C ranges from 17 to 22 mm 2 / s, the kinematic viscosity of 120BS bright oil at 100°C ranges from 22 to 28 mm 2 / s, and the kinematic viscosity of 150BS bright oil at 100°C ranges from 28 to 34 mm 2 / s. Regarding these three types, the higher the kinematic viscosity, the wider the application range of bright oil. CN104449841A discloses a method for producing a bright oil having a pour point of ≤-18°C and a kinematic viscosity of ≥28 mm at 100°C. 2 This method uses a bright oil with a pour point of ≥0°C and a kinematic viscosity of ≥60 mm at 100°C. 2 / s naphthenic light deasphalted oil. In Table 4, the properties of the obtained bright oil are listed, namely, the kinematic viscosity at 100°C is 33.41 mm 2 / s, and the viscosity index is 92. In Table 1, the characteristics of naphthenic light deasphalted oil are listed, that is, the kinematic viscosity at 100°C is 63.50 mm 2 / s, and the viscosity index is 60. The method disclosed therein comprises the following steps:

[0004] (1) Hydrogenation pre-refining reaction process; (2) Hydrogenation isomerization dewaxing reaction process; (3) Hydrogenation supplementary refining reaction process; and product separation process.

[0005] WO2016 / 044646 also discloses a method for producing naphthenic bright oil. In Table 7 thereof, the properties of the dewaxed / hydrofined bright oil obtained in Example 4 are listed, namely, the kinematic viscosity at 100°C is 43.1 mm 2 / s, and a viscosity index of 81. In Tables 5 and 6, the properties of the DAO feedstock used, and the properties of the resulting dewaxed / hydrofinished bright stock are shown. It can be seen from the tables that the kinematic viscosity and viscosity index of the resulting bright stock at 100°C are similar to those of the DAO feedstock used at 100°C.

[0006] It would be desirable to broaden the range of useful naphthenic DAO feedstocks for making naphthenic bright stocks having reduced viscosity and increased viscosity index compared to the naphthenic feedstocks used.

[0007] It is therefore an object of the present invention to provide a process which allows the use of a wider range of naphthenic DAO feedstocks to obtain naphthenic bright stocks having reduced viscosity and increased viscosity index compared to the naphthenic DAO feedstock used. Summary of the invention

[0008] According to the present invention, the above object has been achieved by a method comprising the following steps: A providing a naphthenic feedstock based on naphthenic DAO; B hydrotreating the naphthenic feedstock based on naphthenic DAO to obtain a hydrotreated product; and C fractionating the hydrotreated product to obtain naphthenic bright oil, wherein the viscosity of the naphthenic feedstock in step A is between 45 and 65 mm at 100°C. 2 / s range, wherein the hydroprocessing step B includes the following three independent steps: B1 low-pressure catalytic hydroprocessing of a cycloparaffinic feedstock based on cycloparaffinic deasphalted oil to obtain a low-pressure catalytic hydroprocessed liquid product, wherein the low-pressure catalytic hydroprocessing step B1 is carried out in the hydrogen partial pressure range of 5.0-7.0 MPa; B2 high-pressure catalytic hydroprocessing of the low-pressure catalytic hydroprocessed liquid product leaving the low-pressure catalytic hydroprocessing step B1 to obtain a high-pressure catalytic hydroprocessed product, wherein the high-pressure catalytic hydroprocessing step B2 is carried out in the hydrogen partial pressure range of 13-15 MPa; and B3 catalytic dewaxing of the high-pressure catalytic hydroprocessed product leaving the high-pressure catalytic hydroprocessing step B2 to obtain a catalytic dewaxing product, which constitutes the hydroprocessing product obtained by step B.

[0009] By the method of the present invention, the kinematic viscosity can be reduced to about 45 mm 2 / s naphthenic DAO feedstock production has a kinematic viscosity of about 30 mm at 100 °C 2 / s, and a cyclohexane bright stock with a viscosity index of 90 or more, preferably 95 or more, such as 95-100. Therefore, the method of the present invention can be used to prepare BS150 bright stock from cyclohexane deasphalted oil feedstock. Higher VI, such as 100 or more, can be obtained by the method of the present invention, but at the expense of lower yield.

[0010] In a preferred embodiment, the hydrotreatment step B further comprises a fourth step B4, wherein the catalytically dewaxed product leaving the catalytic dewaxing step B3 is subjected to catalytic hydrofinishing to obtain a catalytically hydrofinished product, which constitutes the hydrofinished product obtained from step B.

[0011] Other embodiments and advantages of the present invention will become apparent from the following detailed description and appended claims.

[0012] As used herein, the term "naphthenic feedstock based on naphthenic deasphalted oil" is intended to mean a naphthenic feedstock comprising at least 50 wt%, preferably at least 70 wt%, more preferably at least 90 wt% of naphthenic deasphalted oil. The remainder of the naphthenic feedstock may be selected from a 5 wt% boiling point of ≥310°C, preferably ≥370°C and a 5 wt% boiling point of ≥900 kg / m 3 , preferably ≥930kg / m 3 Density of hydrocarbon mixtures and fractions.

[0013] As used herein, the term "catalytic dewaxing" is intended to be synonymous with the term "hydrodewaxing" as used in the art.

[0014] The term "cycloalkane" as used herein in relation to a feedstock refers to a hydrocarbon consisting of at least about 30% C N (cycloparaffin content) and a total of less than about 70% C P (paraffin content) and C A (aromatic content) composition of raw materials.

[0015] The term "naphthenic bright stock" as used herein refers to a bright stock that has been prepared according to the process of the present invention from a naphthenic feedstock as defined above with reference to the Brandes IR method. Typical bright stock applications require a VI of 90 or higher. However, the naphthenic bright stock of the present invention itself may or may not be naphthenic as defined above with reference to the Brandes IR method. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A flow chart showing a preferred embodiment of the process of the present invention is shown, wherein the fractionation step C produces three streams, namely a bottom fraction, a middle fraction and a top fraction constituting bright stock, and wherein a catalytic hydrofinishing step B4 is also included. DETAILED DESCRIPTION

[0017] According to the present invention, the hydrotreatment step B is divided into three independent steps (B1, B2, B3). Due to the division into three independent steps, a feedstock with a lower viscosity can be used in the process of the present invention.

[0018] The viscosity of the naphthenic feedstock based on naphthenic DAO is preferably in the range of 50-60 mm at 100°C. 2 / s, such as about 55mm at 100℃ 2 / s.

[0019] The aromatics content of the naphthenic DAO based naphthenic feedstock is less than 40%, preferably in the range of 15-30%.

[0020] The low-pressure catalytic hydroprocessing step B1 is preferably carried out at a temperature in the range of 340-375° C. In the low-pressure catalytic hydroprocessing step B1, the preferred LHSV is in the range of 0.1-0.4 h -1 The preferred hydrogen to oil ratio in step B1 is 300-700 Nm 3 / m 3 In step B1, a commercially available hydroprocessing catalyst or a combination of two or more such catalysts is used. An example of a suitable type of hydroprocessing catalyst is a hydrodemetallization catalyst. The one or more catalysts used in step B1 are preferably used for vacuum gas oil. According to the present invention, the catalyst used in step B1 is preferably a common metal catalyst, such as a catalyst based on Ni, Mo, Co, W or any combination thereof.

[0021] The high pressure catalytic hydroprocessing step B2 is preferably carried out at a temperature in the range of 370-420° C. In the high pressure catalytic hydroprocessing step B2, the preferred LHSV is in the range of 0.7-1.4 h -1 The preferred hydrogen to oil ratio in step B2 is 700-1400 Nm 3 / m 3 , more preferably 1200-1400Nm 3 / m 3 In step B2, a commercially available hydrotreating catalyst or hydrocracking catalyst or a combination of two or more such catalysts is used. The one or more catalysts used in step B2 are preferably used for vacuum gas oil. Suitable catalysts for this step are common metal catalysts, such as catalysts based on Ni, Mo, Co, W or any combination thereof.

[0022] The catalytic dewaxing step B3 is preferably carried out at a temperature in the range of 240-370°C, more preferably 240-290°C. The hydrogen partial pressure in step B3 is preferably in the range of 2.0-15MPa. In some embodiments, for example, where it is desired to carry out step B3 without having to reduce the pressure in the previous step B2, such as in the case where steps B2 and B3 are connected without intermediate storage of the product from step B2, step B3 may be carried out at a pressure in the range of 13-15MPa. In other preferred embodiments, for example, where it is desired to maintain low energy requirements and / or reduce requirements for the equipment used, step B3 may be carried out at a pressure in the range of 2.0-7.5MPa, more preferably 2.0-5.0MPa. In step B3, the preferred LHSV is in the range of 0.5-2.0h -1 , more preferably 1.0-2.0h -1 In step B3, the preferred hydrogen to oil ratio is 200-1400 Nm 3 / m 3 When step B3 is carried out at a pressure in the range of 13-15 MPa, the preferred hydrogen to oil ratio is 700-1400 Nm 3 / m 3 , more preferably 1200-1400Nm 3 / m 3 When step B3 is carried out at a pressure in the range of 2.0-7.5 MPa, the preferred hydrogen-to-oil ratio is 200-500 Nm 3 / m 3 , more preferably 200-400Nm 3 / m 3 In this step, a commercially available dewaxing catalyst is used. Suitable catalysts for this step are common metal catalysts, such as catalysts based on Ni, Mo, W or any combination thereof.

[0023] After step B3, a catalytic hydrofining step B4 may preferably be included in the method of the present invention. The purpose of step B4 is to adjust certain desired properties of the final product. The most important thing is to reduce the content of polycyclic aromatic hydrocarbons, and stabilize unstable compounds, such as olefins, and reaction products involving such unstable compounds, such as mercaptans, to improve color stability and oxidation stability. In the previous steps, especially in step B3, unstable compounds, such as olefins, may be formed. Therefore, in the case where one or more of the above-mentioned desired product characteristics are not met after step B3, step B4 may preferably be included. When catalytic hydrofining step B4 is included, catalytic hydrofining step B4 will generally further reduce the viscosity of the product slightly and further increase the viscosity index of the product slightly, for example due to the saturation of aromatics.

[0024] When the catalytic hydrofining step B4 is included, the catalytic hydrofining step B4 is preferably carried out at a temperature in the range of 240-370°C, more preferably 240-290°C. The hydrogen partial pressure in step B4 is preferably in the range of 2.0-7.5 MPa, more preferably 2.0-5.0 MPa. In step B4, the hydrogen-to-oil ratio is preferably in the range of 200-500 Nm 3 / m 3 , more preferably 200-400Nm 3 / m 3 In step B4, the preferred LHSV is in the range of 3-20h- 1 , more preferably 5-20h -1 , even more preferably 10-17h -1 In this step, a commercially available hydroprocessing catalyst or a combination of two or more such catalysts is used. Suitable catalysts for this step are common metal catalysts, such as catalysts based on Ni, Mo, Co, W or any combination thereof.

[0025] In a preferred embodiment wherein a catalytic hydrofinishing step B4 is included, the catalytic hydrofinishing step B4 is carried out in the same reactor as the catalytic dewaxing step B3.

[0026] In the method taught in CN104449841A, the catalytic dewaxing step is included in the hydroisomerization dewaxing reaction process, wherein the hydropre-refined oil is contacted with an isomerization dewaxing catalyst. The catalyst used in the method taught in CN104449841A, i.e., an isomerization dewaxing catalyst and an auxiliary refining catalyst, contains a Group VIII noble metal. The noble metal is Pt and / or Pd and / or Ir, and the amount thereof is 0.3wt.% to 0.6wt.%. In the embodiment, only Pt is used.

[0027] However, the hydroisomerization catalyst used in the process of CN104449841A is generally easily deactivated by nitrogen and sulfur (mainly nitrogen), and therefore requires a feed with very low sulfur and nitrogen content. To this end, a catalyst for removing H 2 S and NH 3 The stripping step is as shown in Figure 4 of CN104449841A.

[0028] On the other hand, the method of the present invention preferably utilizes common metal catalysts. In the method of the present invention, the low-pressure catalytic hydroprocessing step B1 and the high-pressure catalytic hydroprocessing step B2, which together correspond to the hydrogenation pre-refining reaction process taught in CN104449841A, are carried out as separate steps. Therefore, the method of the present invention can allow the transformation of existing medium and low pressure units so that the units can be used for the intended purpose, thereby reducing investment costs compared to building greenfield units. The present invention does not require the use of precious metal catalysts. In a preferred embodiment of the method of the present invention, precious metal catalysts are not used.

[0029] In addition, when common metal catalysts are used in steps B1 and B2, a stripping step for removing nitrogen and sulfur is not required in the process of the present invention.

[0030] In fact, rather than removing the sulfur, it may be beneficial to retain the sulfur in the product because in some bright stock applications the sulfur acts as a natural oxidation inhibitor.

[0031] Preferably, a common metal catalyst is used in each of steps B1, B2 and B3, and when step B4 is included, a common metal catalyst is also used in step B4.

[0032] The hydroisomerization step described in CN104449841A occurs at a much higher pressure than required for the catalytic dewaxing step of the present invention.

[0033] The fractionation step C is carried out in order to separate the bottom fraction containing bright oil from the product obtained in the hydroprocessing step B. Therefore, in the fractionation step, based on the boiling point characteristics, the product obtained from the hydroprocessing step B is divided into two or more streams, wherein the naphthenic bright oil will be obtained as the bottom fraction. The fractionation step C can be carried out using methods known to those skilled in the art, such as distillation under atmospheric pressure or reduced pressure. It is preferred to distill under reduced pressure, such as vacuum distillation. Preferably, in the fractionation step C, the product obtained from the hydroprocessing step B is divided into at least three streams, i.e., the bottom fraction (bright oil), the middle fraction and the top fraction. The cut point is selected so that the resulting product stream has the desired characteristics, such as flash point and viscosity. Distillation under atmospheric pressure and reduced pressure, respectively, is well known to those skilled in the art and will not be further described herein. If desired, fractionation can be carried out to produce more than three streams, such as 4, 5 or 6 streams, wherein the bright oil is obtained as the bottom fraction.

[0034] The preferred naphthenic deasphalted oil used as the feedstock for the process of the present invention is a naphthenic deasphalted oil which has been obtained by solvent deasphalting using a solvent selected from the group consisting of C2-C8 alkanes, furfural and N-methyl-2-pyrrolidone, preferably propane.

[0035] The naphthenic deasphalted oil based feedstock preferably comprises at least 90 weight percent naphthenic deasphalted oil, and more preferably consists essentially of naphthenic deasphalted oil, in which case the feedstock may be referred to as a naphthenic deasphalted oil feedstock.

[0036] In order to better understand the present invention, it will be described through the following examples.

[0037] Example

[0038] The characteristics of the naphthenic deasphalted oil DAO based feedstock used in the experiments are shown in Table 1.

[0039] Characteristics of the naphthenic deasphalted oil based feedstock used in the experiments. The feedstock used was 100% DAO. The DAO was obtained from solvent deasphalting of vacuum residue from naphthenic crude oil. The solvent used in the deasphalting process was propane. A supercritical solvent extraction unit was used.

[0040] The characteristics listed in the table below were established using the following standard methods:

[0041] Density: ASTM D7042

[0042] Viscosity at 40°C: ASTM D7042

[0043] Viscosity at 100°C: ASTM D7042

[0044] Viscosity Index: ASTM D2270

[0045] CA / CP / CN(IR): ASTM D2150

[0046] Pour point: ASTM D7346

[0047] Cloud Point: ASTM D7689

[0048] Sulfur: ASTM D2622

[0049] Nitrogen: ASTM D4629

[0050] Simulated distillation: ASTM D2887

[0051] Refractive Index ASTM 1747

[0052] Table 1 - Characteristics of naphthenic feedstocks based on naphthenic oils

[0053]

[0054]

[0055] The low-pressure catalytic hydroprocessing step B1 was carried out using a CoNiMo catalyst. Step B1 was carried out at two different temperatures while keeping other parameters unchanged. The conditions are shown in Table 2. The characteristics of the liquid product obtained from the low-pressure catalytic hydroprocessing step B1 are shown in Table 3.

[0056] Table 2 - Low Pressure Catalytic Hydroprocessing Conditions for Step B1

[0057]

[0058] Table 3 - Characteristics of liquid products from low pressure catalytic hydroprocessing step B1

[0059]

[0060] High pressure catalytic hydroprocessing step B2 is carried out using two different common metal catalysts, NiMo common metal catalyst and NiW common metal catalyst. Step B2 is carried out at two different temperatures while keeping other parameters unchanged. The conditions are shown in Table 4. The characteristics of the liquid product obtained by high pressure catalytic hydroprocessing step B2 are shown in Table 5.

[0061] Table 4 - High Pressure Catalytic Hydroprocessing Conditions for Step B2

[0062]

[0063] Table 5 - Characteristics of liquid products from high pressure catalytic hydroprocessing step B2

[0064]

[0065] In the embodiment, the catalytic dewaxing step B3 and the catalytic hydrofining step B4 occur in the same reactor. NiMo common metal catalyst is used in both steps B3 and B4. The two steps B3 and B4 are carried out at two different temperatures respectively, while keeping other parameters unchanged. The conditions are shown in Table 6. The characteristics of the liquid product obtained by the catalytic hydrofining step B4 are shown in Table 7.

[0066] Table 6 - Conditions for Catalytic Dewaxing (DW) Step B3 and Catalytic Hydrofining (HF) Step B4

[0067]

[0068] Table 7 - Characteristics of liquid products from catalytic dewaxing step B3 and catalytic hydrofinishing step B4

[0069]

[0070] The liquid product from the catalytic hydrofinishing step B4 was subjected to two different fractionation steps. The characteristics of the bottom product obtained are shown in Table 8.

[0071] Table 8 - Characteristics of the bottom product (i.e. bright stock) from fractionation step C

[0072]

[0073] As can be seen from the examples, starting from a naphthenic DAO feedstock having a viscosity of 42.9 cSt at 100°C and a VI of 79, a resulting naphthenic bright stock having a viscosity of 28.7 cSt at 100°C and a VI of 98, or a viscosity of 18.6 cSt at 100°C and a VI of 93, can be obtained by the process of the present invention, depending on the cut point chosen.

[0074] While the above examples have been described by preferred embodiments of the process in which step B4 is included, it is believed that in similar examples in which step B4 is not included, the resulting naphthenic bright stock will have only slightly higher viscosity and slightly lower VI.

Claims

1. A method for preparing naphthenic bright stock, comprising the following steps: A) providing a naphthenic feedstock based on naphthenic deasphalted oil (DAO); B) hydrotreating the naphthenic feedstock based on naphthenic deasphalted oil to obtain a hydrotreated product; as well as, C) fractionating the hydrotreated product to obtain naphthenic bright oil, The viscosity of the cycloalkane raw material in step (A) is 45 mm at 100°C. 2 / s-65mm 2 / s range, The hydroprocessing step (B) comprises the following three independent steps: B1) subjecting the naphthenic feedstock based on naphthenic deasphalted oil to low-pressure catalytic hydroprocessing to obtain a low-pressure catalytic hydroprocessed liquid product, wherein the low-pressure catalytic hydroprocessing step (B1) is carried out at a hydrogen partial pressure range of 5.0 MPa to 7.0 MPa; B2) subjecting the low-pressure catalytic hydroprocessing liquid product leaving the low-pressure catalytic hydroprocessing step (B1) to high-pressure catalytic hydroprocessing to obtain a high-pressure catalytic hydroprocessing product, wherein the high-pressure catalytic hydroprocessing step (B2) is carried out at a hydrogen partial pressure range of 13 MPa to 15 MPa; and B3) catalytically dewaxing the high pressure catalytic hydroprocessing product leaving the high pressure catalytic hydroprocessing step (B2) to obtain a catalytically dewaxed product, which constitutes the hydroprocessing product obtained from step (B).

2. The method according to claim 1 further comprises a step of solvent deasphalting using a solvent selected from C2-C8 alkanes, furfural and N-methyl-2-pyrrolidone, preferably propane, to obtain cycloalkane DAO of the cycloalkane feedstock in step (A).

3. The method according to claim 1 or 2, wherein the viscosity of the raw material in step (A) is 50 mm at 100°C. 2 / s-60mm 2 / s range.

4. The method according to any one of the preceding claims, wherein the low-pressure catalytic hydrotreatment step (B1) is carried out under one or more conditions selected from the following group of conditions: temperature in the range of 340°C to 375°C; LHSV at 0.1 h -1 -0.4h -1 The hydrogen-to-oil ratio is within 300 Nm 3 / m 3 -700Nm 3 / m 3 and preferably under a combination of all conditions.

5. The method according to any one of the preceding claims, wherein the high pressure catalytic hydrotreatment step (B2) is carried out under one or more conditions selected from the following group of conditions: temperature in the range of 370°C to 420°C; LHSV at 0.7h -1 -1.4h -1 The hydrogen-to-oil ratio is within 700 Nm 3 / m 3 -1400Nm 3 / m 3 and preferably under a combination of all conditions.

6. The method according to any one of the preceding claims, wherein the catalytic dewaxing step (B3) is carried out under one or more conditions selected from the following group of conditions: temperature in the range of 240°C to 370°C; hydrogen partial pressure in the range of 2.0MPa to 15MPa, preferably 2.0MPa to 7.5MPa or 13MPa to 15MPa; LHSV in the range of 0.5h -1 -2.0h -1 The hydrogen-to-oil ratio is within 200 Nm 3 / m 3 -1400Nm 3 / m 3 , preferably 700Nm 3 / m 3 -1400Nm 3 / m 3 or 200Nm 3 / m 3 -500Nm 3 / m 3 and preferably under a combination of all conditions.

7. The process according to any one of the preceding claims, wherein the hydrotreatment step (B) additionally comprises the following fourth step: B4) subjecting the catalytically dewaxed product leaving the catalytic dewaxing step (B3) to catalytic hydrofining, thereby obtaining a catalytically hydrofined product, which constitutes the hydrotreated product obtained from step (B).

8. The method according to claim 7, wherein the catalytic hydrofining step (B4) is carried out under one or more conditions selected from the following group of conditions: temperature in the range of 240°C to 370°C; hydrogen partial pressure in the range of 2.0MPa to 7.5MPa; hydrogen to oil ratio in the range of 200Nm 3 / m 3 -500Nm 3 / m 3 and LHSV in 3h -1 -20h -1 and preferably under a combination of all conditions.

9. The method according to claim 7 or 8, wherein the catalytic dewaxing step (B3) and the catalytic hydrofinishing step (B4) are both carried out in the same reactor.

10. A method according to any one of the preceding claims, wherein: In steps (B1), (B2) and (B3), and also in step (B4) when step (B4) is included, only common metal catalysts are used.

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