Process oil, high-viscosity base oil, and process for the production thereof

Abstract

A novel process for the production of an extract useful as a process oil and a raffinate useful as a high-viscosity base oil by solvent refining is provided, characterized in that reduced pressure distillation is effected under the condition that the end point of distillate is 580° C. or higher as calculated in terms of atmospheric pressure or the initial boiling point of the residue is 450° C. or higher as calculated in terms of atmospheric pressure, the resulting residual oil is deasphalted under the condition that the carbon residue content in the deasphalted oil reached 1.6% or less, and the resulting deasphalted oil is subjected to solvent refining under the condition that the yield of extract is from 35% to 60%. It is a novel and economically excellent process for the preparation of a rubber process oil having a high safety, a high penetrating power with respect to rubber polymer and the content of PCA extract of less than 3%.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a process oil for the addition into natural rubber and synthetic rubber and a high-viscosity base oil, as well as to a process for the production thereof. More particularly, the present invention relates to a rubber process oil which has a low content of a polycyclic aromatic compound so as to exhibit no toxicity or carcinogenicity and can be easily handled and to a process for the production thereof.

BACKGROUND OF THE INVENTION

[0002] A rubber process oil is used to facilitate the procedure such as kneading, extrusion and molding in the production of rubber by exhibiting a penetrating power with respect to rubber polymer structure. A rubber process oil is also used to improve the physical properties of rubber products. Such a rubber process oil is required to have an appropriate affinity for rubber. On the other hand, examples of rubbers to be processed include natural rubber and synthetic rubber. There are various synthetic rubbers. Among these rubbers, natural rubber and styrene-butadiene rubber (SBR) are often used. Therefore, a rubber process oil having a large amount of aromatic hydrocarbon and a high affinity for rubber is normally used.

[0003] The rubber process oil is obtained by extracting a lubricant fraction obtained by distillation of crude oil under reduced pressure or an oil obtained by deasphalting reduced pressure distillation residue with a solvent having an affinity for aromatic hydrocarbon. The rubber process oil thus obtained contains an aromatic compound in an amount of from 70% to 99% as determined by column chromatography, exhibits a percent CA of from 20% to 50% according to ring analysis (ASTM D2140) and contains the content of PCA (polycyclic aromatic compound) extract of from 5 to 25% by mass. The content of PCA extract is defined by IP346 method of British Society of Petroleum.

[0004] However, the carcinogenicity of PCA has recently been noticed. In Europe, the law stipulates that oils having the content of PCA extract of 3% or more shall have an indication of toxicity. There is a movement to regulate the use of these oils. Accordingly, it is of urgent necessity to reduce the content of PCA extract of rubber process oil to less than 3%.

[0005] Referring to rubber process oil having the content of PCA extract of less than 3%, JP-W-6-505524 discloses a process for the production of a rubber process oil having the content of PCA extract of less than 3% which comprises deasphalting the residue of distillation under reduced pressure, and then dewaxing the oil thus obtained (the term “JP-W” means a published Japanese translation of a PCT application).

[0006] The foregoing oil has the low content of PCA extract but has a high aniline point. The aniline point is an index of the content of aromatic hydrocarbon. A high aniline point means a low aromatic hydrocarbon content. However, when the content of aromatic hydrocarbon in an oil is decreased, the resulting oil exhibits a lowered affinity for rubber. Therefore, the rubber process oil disclosed in the above cited patent publication exhibits deterioration of properties required for rubber process oil, i.e., penetrating power with respect to rubber polymer. Further, it is made difficult to provide the final rubber product with satisfactory physical conditions.

[0007] JP-W-7-501346 discloses a noncarcinogenic bright stock extract and/or deasphalted oil and a process for the production thereof, and proposes to use characteristics related to mutagenicity index (MI) as an index of purification to reduce MI to 1 or less. In this case, an oil obtained by deasphalting the residue in a vacuum distillation column, an oil having a reduced aromatic compound content obtained by extracting a deasphalted oil or an oil obtained by dewaxing the foregoing oil is used. However, it is considered that the content of PCA extract is 3% or more. The relationship between MI and the content of PCA extract of such a deasphalted oil is not disclosed in the above cited patent publication.

[0008] The present invention is to solve the foregoing problems. It is therefore an object of the present invention to provide a rubber process oil having a high safety, a high penetrating power with respect to rubber polymer and the content of PCA extract of less than 3% and a novel and economically excellent process for the preparation thereof.

SUMMARY OF THE INVENTION

[0009] As a result of extensive studies to achieve the foregoing object of the invention, the present inventors found that the content of PCA extract reaches less than 3% under specific distillation and solvent refining conditions. The present invention has thus been accomplished.

[0010] Based on the above finding, the present invention provides:

[0011] 1. A process for the production of an extract useful as a process oil and a raffinate useful as a high-viscosity base oil by solvent refining, which comprises

[0012] carrying out a reduced pressure distillation under the condition that the end point of distillate as converted to the value under atmospheric pressure is 580° C. or higher or the initial boiling point of the residue is 450° C. or higher as calculated in terms of atmospheric pressure,

[0013] deasphalating the resulting residual oil under the condition that the carbon residue content in the deasphalted oil reaches 1.6% or less, and

[0014] subjecting the resulting deasphalted oil to solvent refining under the condition that the yield of extract is from 35% to 60%.

[0015] 2. The production process according to 1 above, wherein the extract useful as a process oil exhibits a 100° C. dynamic viscosity of from 50 to 100 mm2/s, a percent CA of from 15% to 35%, the content of PCA extract (IP346) of less than 3%, an aniline point of 90° C. or lower, a chromatographically-determined aromatic content of from 60% to 95% by weight and Mw (weight-average molecular weight) of 650 or more.

[0016] 3. The production process according to 1 above, wherein the high-viscosity base oil having a 40° C. dynamic viscosity of from not lower than 400 mm2/s to not higher than 700 mm2/s obtained after the dewaxing of raffinate exhibits a pour point of not higher than −5° C. and a viscosity index of not lower than 95.

[0017] 4. A process oil having a 100° C. dynamic viscosity of from 50 to 100 mm2/s, a percent CA of from 15% to 35%, the content of PCA extract (IP346) of less than 3%, an aniline point of 90° C. or lower, a chromatographically-determined aromatic content of from 60% to 95% by weight and Mw (weight-average molecular weight) of 650 or more.

[0018] 5. The process oil according to 4 above, which has a mutagenicity index MI of less than 1.

DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be further described hereinafter.

[0020] In general, a process oil can be prepared from petroleum, particularly from a lubricant fraction derived from crude oil, as a starting material. The lubricant fraction can be obtained as a fraction when the residue obtained by atmospheric distillation of crude oil is distilled under reduced pressure or as a deasphalted oil when the residue obtained by reduced pressure distillation of atmospheric residue is deasphalted. As a method for separating the constituents of the lubricant fraction from each other there is used solvent refining. When the lubricant fraction is subjected to solvent refining with a solvent having a selective affinity for an aromatic hydrocarbon compound, the aromatic hydrocarbon can be separated from the lubricant fraction. The extract thus obtained contains a large amount of high boiling point aromatic compounds.

[0021] Since a solvent having a selective affinity for an aromatic hydrocarbon has a higher affinity for PCA than for an aromatic hydrocarbon, the aromatic hydrocarbon extracted by ordinary extraction method contains a large amount of PCA. If PCA can be removed from the extract, a suitable process oil can be obtained.

[0022] The inventors conducted studies of process for the production of an oil having a reduced content of PCA. As a result, it was found that an oil having a reduced content of PCA can be effectively produced by combining specific distillation and solvent refining conditions.

[0023] In accordance with embodiments of the process for the production of the rubber process oil according to the present invention, a lubricant fraction obtained by reduced pressure distillation of crude oil or a deasphalted oil fraction obtained by deasphalting the atmospheric or reduced pressure distillation residue of crude oil is treated with a solvent having an affinity for aromatic hydrocarbon. The solvent and the resulting extract are then separated and recovered. The raffinate separated during the solvent extraction may be subjected to hydrogenation/dewaxing, if necessary, and used as a high-viscosity base oil.

[0024] The process oil obtained by each of these embodiments of the production of the rubber process oil according to the present invention is the most suitable rubber process oil having a lower content of polycyclic aromatic compound but rich with aromatic hydrocarbon.

[0025] The conventional definition of PCA may include an aromatic compound having three or more cycles, but the IP346 method is an ordinary and standard method approved as a method for determining PCA content in oil material.

[0026] Since the rubber process oil obtained according to the production process of the present invention has an extremely low content of polycyclic aromatic compounds but shows little or no decrease in the chromatographically-determined aromatic hydrocarbon content as compared with the conventional rubber process oil. Thus, the rubber process oil of the present invention has a high penetrating power with respect to rubber such as SBR rubber and natural rubber and thus does not lower the workability of rubber. In addition, the rubber process oil of the present invention is a material which can provide a rubber exhibiting physical properties of the almost same level as that of rubber products obtained by treatment with a conventional process oil containing much PCA.

[0027] Embodiments of the production process of the present invention will be further described hereinafter.

[0028] In order to produce a rubber process oil of the present invention, crude oil is subjected to atmospheric distillation. The atmospheric residue is then subjected to reduced pressure distillation. The resulting residue is then deasphalted. The deasphalted oil fraction thus obtained is then treated with a solvent having a selective affinity for aromatic hydrocarbon to remove raffinate therefrom. In this manner, an extract is obtained in the form of mixture with the solvent. A rubber process oil can be obtained by removing the solvent from the mixture.

[0029] Deasphalted oils obtained by deasphalting the residue of distillation under reduced pressure of the atmospheric residue of various crude oils such as paraffin oil and naphthalene oil can be preferably used.

[0030] The reduced pressure distillation may be carried out under the condition that the end point of distillate is 580° C. or higher as calculated in terms of atmospheric pressure or the initial boiling point of the residue is 450° C. or higher as calculated in terms of atmospheric pressure.

[0031] The end point of distillate which is lower than 580° C. is not preferable, because the resulting extract would have the high content of PCA extract.

[0032] Subsequently, the residue obtained by reduced pressure distillation is deasphalted under the condition that the carbon residue content in the deasphalted oil reached 1.6% or less. The carbon residue content in the deasphalted oil exceeding 1.6% is not preferable, because the resulting extract would have an increased PCA content and the oxidation stability of the high-viscosity base oil obtained as a raffinate would be adversely influenced.

[0033] The deasphalted oil thus obtained is then subjected to solvent refining, i.e., extraction with a solvent having an affinity for aromatic hydrocarbon. Examples of the solvent having a selective affinity for aromatic hydrocarbon include furfural, phenol or N-methyl-2-pyrrolidone, singly or in combination of selected two or more thereof.

[0034] The solvent refining is effected under the condition that the yield of extract becomes from 35% to 60%. The solvent refining under the condition that the yield of extract falls below 35% is not preferable, because the content of PCA extract would not fall below 3%. On the contrary, the solvent refining under the condition that the yield of extract exceeding 60% is not preferable, because the resulting extract would exhibit a reduced aromatic content and the yield of the high-viscosity base oil obtained as a raffinate would be reduced to lower the economy.

[0035] Specific extraction conditions under which the yield of extract falls within the above defined range depend on the composition of the deasphalted oil to be processed and thus cannot be unequivocally determined. In practice, however, the extraction conditions can be adjusted by the solvent ratio, pressure, temperature, etc.

[0036] In general, the deasphalted oil is brought into contact with the solvent at a temperature of generally 60° C. or higher, preferably from 60° C. to 155° C., and a solvent/oil ratio of about 2/1 to 7/1 (by volume) to remove the raffinate -therefrom. The raffinate thus removed may be subjected to hydrogenation/dewaxing as necessary so that it is used as a high-viscosity lubricating base oil.

[0037] The extract useful as a process oil in the present invention exhibits a 100° C. dynamic viscosity of from 50 to 100 mm2/s, a percent CA (ASTM D2140) of from 15% to 35%, the content of PCA extract (IP346) of less than 3%, an aniline point of 90° C. or lower, a chromatographically-determined aromatic content of from 60% to 95% by weight and Mw (weight-average molecular weight) of 650 or more. The extract also exhibits a mutagenicity index MI of less than 1.

[0038] The 100° C. dynamic viscosity of the extract exceeding 100 mm2/s is not preferable, because the extract exhibits a lowered workability when used as a process oil and the extract does not exert a sufficient effect of lowering viscosity with respect to rubber when used as a process oil. On the contrary, the 100° C. dynamic viscosity of the extract falling below 50 mm2/s is not preferable, because it becomes extremely difficult to reduce the content of PCA extract to less than 3% and the economical efficiency of refining process is lowered.

[0039] When the percent CA (ASTM D2140) of the extract falls below 15%, it would be difficult to produce a rubber using a rubber process oil and there is a possibility that the resulting rubber products have deteriorated physical properties. On the contrary, when the percent CA (ASTM D2140) exceeds 35%, there is a possibility that the resulting rubber products have deteriorated physical properties similarly to the case where the percent CA (ASTM D2140) falls below 15% and it might be extremely difficult to reduce the content of PCA extract to less than 3% and the economical efficiency of refining process is lowered.

[0040] The content of PCA extract (IP346) should be below 3% because the content of PCA extract of 3% or more conflicts with EU regulations for the reason that it can be carcinogenic.

[0041] The aniline point of the extract exceeding 90° C. is not preferable, because the affinity to a rubber is lowered.

[0042] When the chromatographically-determined aromatic content of the extract falls below 60%, there is a possibility that the production of a rubber using a rubber process oil becomes difficult and that the resulting rubber products have deteriorated physical properties. On the contrary, when the chromatographically-determined aromatic content of the extract exceeds 95%, there is a possibility that the resulting rubber products have deteriorated physical properties and it would be difficult to reduce the content of PCA extract to less than 3% and the economical efficiency of refining process is lowered.

[0043] The Mw (weight-average molecular weight) of the extract falling below 650 is not preferable, because it would be extremely difficult to reduce the content of PCA extract to less than 3% and the economical efficiency of refining process is lowered.

[0044] When the mutagenicity index MI of the extract is 1.0 or more, the resulting product can be carcinogenic and thus it is not preferable.

[0045] The glass transition point of the extract determined by a differential scanning calorimeter (DSC) is preferably not lower than −70° C. because the resulting extract exerts an improved effect of providing the rubber products with reduced loss. From the standpoint of low temperature properties, the glass transition point of the extract is preferably not higher than −20° C.

[0046] The raffinate obtained by solvent refining is optionally performed to hydrogenation/dewaxing to obtain a high-viscosity base oil having a pour point of not higher than −5° C., a viscosity index of not lower than 95 and a dynamic viscosity (40° C.) of from 400 mm2/s to 700 mm2/s.

[0047] In accordance with the production process of the invention, the extract obtained by the one-step solvent extraction can be used as a product as it is, making it possible to reduce the production cost as compared with the two-step solvent extraction process or the process required second step such as hydrogenation.

[0048] The production process of the invention makes it possible to obtain a noncarcinogenic process oil and a high-viscosity lubricating base oil, VI of which is higher than usual at the same time, giving an excellent economy.

[0049] The present invention will be further described-in the following examples, but the present invention should not be construed as being limited thereto.

[0050] The various properties of the invention were determined according to the following methods.

[0051] Measurement of concentration of polycyclic aromatic compound (PCA):

[0052] The content of PCA extract was determined by IP346 testing method (edition of 1992).

[0053] Ring analysis:

[0054] The ring analysis percent CA was calculated according to ASTM D 2140-97.

[0055] The dynamic viscosity was measured according to the method defined in JIS K2283-1993.

[0056] Aniline point:

[0057] The aniline point was measured according to the method defined in JIS K2256-1998.

[0058] Mw (weight-average molecular weight):

[0059] Mw is defined as &Sgr;Mi2Ni/&Sgr;MiNi (Mi: molecular weight; Ni: number of mols). Mw is generally measured by GPC (gel permeation chromatography).

[0060] Mw was measured by GPC under the following conditions (in polystyrene equivalence).

[0061] Solvent: Tetrahydrofuran

[0062] Column temperature: 50° C.

[0063] Flow rate: 1.0 ml/min.

[0064] Column: Shodex GPC KF-805L

[0065] Detector: Shimadzu RID-6A

[0066] Pour point:

[0067] The pour point was measured according to the method defined in JIS C2101-1999.

[0068] Viscosity index:

[0069] The viscosity index was calculated according to the method defined in JIS K2283-1993.

[0070] Nitrogen content:

[0071] The nitrogen content was calculated according to the method defined in JIS K2609-1998.

[0072] Sulfur content:

[0073] The sulfur content was measured according to the method defined in JIS K2541-1996.

[0074] Chromatographically-determined aromatic content:

[0075] The chromatographically-determined aromatic content was measured according to the method defined in ASTM D2007-98.

[0076] Mutagenicity index (MI):

[0077] The mutagenicity index (MI) was measured according to the method defined in ASTM E1687-98.

[0078] The gas chromatographic distillation was measured according to the method fined in ASTM 2887-97a.

[0079] The carbon residue content was measured according to the method defined in JIS K2270-1998.

EXAMPLE 1

[0080] The atmospheric residue of Arabian light crude oil was distilled under reduced pressure until the end point (gas chromatographic distillation FBP) reached 600° C. The resulting residue was then deasphalted with propane (solvent ratio: 700%; pressure: 3.3 MPaG; reaction column temperature: 72° C.) so that the carbon residue content reached 1.3%. The deasphalted oil was then subjected to solvent extraction with furfural as a solvent at a solvent ratio of 400% so that the yield of extract reached 42%.

[0081] The raffinate thus obtained was subjected to purification by hydrogenation in the presence of an alumina-based catalyst having 3 wt % of nickel and 12 wt % of molybdenum supported thereon (hydrogen pressure: 6.5 MPaG; liquid hourly space velocity (LHSV): 2.5 h−1; temperature: 315° C.; desulfurization rate: 48%) to remove light contents therefrom, and then subjected to solvent dewaxing (methyl ethyl ketone: toluene=1:1; solvent ratio: 330%; cooled to −20° C.; yield: 84%) to obtain a high-viscosity base oil having a dynamic viscosity (40° C.) of 508.4 mm2/s, a pour point of −10° C. and a viscosity index of 101.

[0082] The extract thus obtained exhibited the content of PCA extract of 2.7% by mass as measured by IP346 method, a percent CA of 25.3%, a dynamic viscosity (100° C.) of 65.26 mm2/s, an aniline point of 72° C., a chromatographically-determined aromatic content of 84% by weight and MW of 785.

COMPARATIVE EXAMPLE 1

[0083] The atmospheric residue of Arabian light crude oil was distilled under reduced pressure until the end point (gas chromatographic distillation FBP) reached 600° C. The resulting residue was then deasphalted with propane (solvent ratio: 700%; pressure: 3.3 MPaG; reaction column temperature: 72° C.) so that the carbon residue content reached 1.3%. The deasphalted oil was then subjected to solvent extraction with furfural as a solvent at a solvent ratio of 350% so that the yield of extract reached 30%.

[0084] The extract thus obtained exhibited the content of PCA extract of 4.0% by mass as measured by IP346 method, a percent CA of 28.6%, a dynamic viscosity (100° C.) of 80.24 mm2/s, an aniline point of 63° C., a chromatographically-determined aromatic content of 86% by weight and MW of 730.

COMPARATIVE EXAMPLE 2

[0085] The atmospheric residue of Arabian light crude oil was distilled under reduced pressure until the end point (gas chromatographic distillation FBP) reached 600° C. The resulting residue was then deasphalted with propane (solvent ratio: 700%; pressure: 3.3 MPaG; reaction column temperature: 72° C.) so that the carbon residue content reached 1.3%. The deasphalted oil was then subjected to solvent extraction with furfural as a solvent at a solvent ratio of 280% so that the yield of extract reached 20%.

[0086] The extract thus obtained exhibited the content of PCA extract of 5.3% by mass as measured by IP346 method, a percent CA of 33.5%, a dynamic viscosity (100° C.) of 110.6 mm2/s, an aniline point of 51° C., a chromatographically-determined aromatic content of 86% by weight and MW of 645.

COMPARATIVE EXAMPLE 3

[0087] The atmospheric residue of Arabian light crude oil was distilled under reduced pressure until the end point (gas chromatographic distillation FBP) reached 560° C. The resulting residue was then deasphalted with propane (solvent ratio: 700%; pressure: 3.3 MPaG; reaction column temperature: 720° C.) so that the carbon residue content reached 1.3%. The deasphalted oil was then subjected to solvent extraction with furfural as a solvent at a solvent ratio of 280% so that the yield of extract reached 25%.

[0088] The extract thus obtained exhibited the content of PCA extract of 9.9% by mass as measured by IP346 method, a percent CA of 33.6%, a dynamic viscosity (100° C.) of 58.33 mm2/s, an aniline point of 55° C., a chromatographically-determined aromatic content of 86% by weight and MW of 601.

[0089] The conditions under which solvent refining was conducted in these examples and comparative examples and the properties of the high-viscosity lubricating base oils obtained by solvent dewaxing of the resulting extracts and raffinates are set forth in Table 1 below. 1 TABLE 1 Comparative Comparative Comparative Example Example Example Example 1 1 2 3 Process Gas chromatographic 500 600 600 560 oil distillation FBP Solvent ratio 400 350 280 280 Yield (%) 42 30 20 25 Density (15° C.) g/cm3 0.9716 0.9853 1.0094 0.9994 Dynamic viscosity 226.7 304.9 485.4 213.5 (75° C.) mm2/g Dynamic viscosity 65.26 80.24 110.6 58.33 (100° C.) mm2/g Nitrogen content mass-% 0.11 0.14 0.15 0.16 Aniline point (° C.) 72 63 51 55 PCA extract 2.7 4.0 5.3 9.9 mass-% Mw (weight-average 785 730 645 601 molecular weight) Refractive index (nD20) 1.5432 1.5522 1.5671 1.5634 VGC 0.9005 0.9160 0.9535 0.9464 RI 1.0589 1.0611 1.0639 1.0652 % CA 25.3 28.6 33.5 33.6 Aromatic content wt-% 84 86 86 86 Glass transition point −45 −42 −42 −42 (° C.) Mutagenicity index (MI) <1 <1 <1 ≧1 High- Density (15° C.) g/cm3 0.8940 0.8977 0.9011 — viscosity Dynamic viscosity 508.4 520.9 510.7 — base (40° C.) mm2/g oil Dynamic viscosity 34.12 33.91 33.00 — (100° C.) mm2/g Viscosity index 101 98 97 — Sulfur content mass-% 0.50 0.61 0.75 — Aniline point ° C. 128 124 122 — Pour point ° C. −10 −10 −10 —

[0090] As mentioned above, the production process of the invention makes it possible to obtain a process oil having a high safety and a high penetrating power with respect to rubber polymer and a high-viscosity base oil at the same time and a reduced cost.

[0091] While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

[0092] This application is based on Japanese patent application No. 2000-117447, filed on Apr. 19, 2000, and incorporated herein by reference.

Claims

1. A process for the production of an extract useful as a process oil and a raffinate useful as a high-viscosity base oil by solvent refining, which comprises

carrying out reduced pressure distillation under the condition that the end point of distillate as converted to the value under atmospheric pressure is 580° C. or higher or the initial boiling point of the residue is 450° C. or higher as calculated in terms of atmospheric pressure,

deasphalating the resulting residual oil under the condition that the carbon residue content in the deasphalted oil reaches 1.6% or less, and subjecting the resulting deasphalted oil to solvent refining under the condition that the yield of extract is from 35% to 60%.

2. The production process according to

claim 1, wherein said extract useful as a process oil exhibits a 100° C. dynamic viscosity of from 50 to 100 mm2/s, a percent CA of from 15% to 35%, the content of PCA extract (IP346) of less than 3%, an aniline point of 90° C. or lower, a chromatographically-determined aromatic content of from 60% to 95% by weight and Mw (weight-average molecular weight) of 650 or more.

3. The production process according to

claim 1, wherein the high-viscosity base oil having a 40° C. dynamic viscosity of from not lower than 400 mm2/s to not higher than 700 mm2/s obtained after the dewaxing of raffinate exhibits a pour point of not higher than −5° C. and a viscosity index of not lower than 95.

4. A process oil having a 100° C. dynamic viscosity of from 50 to 100 mm2/s, a percent CA of from 15% to 35%, the content of PCA extract (IP346) of less than 3%, an aniline point of 90° C. or lower, a chromatographically-determined aromatic content of from 60% to 95% by weight and Mw (weight-average molecular weight) of 650 or more.

5. The process oil according to

claim 4, which has a mutagenicity index MI of less than 1.