WO2011098096A1 - Method for producing process oils having a low content of polycyclic aromatics and use thereof - Google Patents

Abstract

The invention relates to a method for producing process oils from mineral oil refining having improved properties, wherein said method comprises extracting a bright stock extract or a bright stock extract mixture comprising a bright stock extract and one or more oils. The process oils according to the invention can be used as plasticizers or extender oils for rubbers and rubber mixtures. The process oils according to the invention make the processing easier and produce a greater stability of the rubber products.

Description

 Process for the preparation of process oils with a low content of polycyclic aromatic compounds and their use

The invention relates to a process for producing a refined, extracted and optionally dewaxed process oil, which comprises as a process step the extraction of a bright stock extract (RAE) or a mixture of a bright stock extract and one or more oils, wherein as product a process oil is obtained with a content of polycyclic aromatic <3 wt .-%, and the use of the process oils produced by such a process.

Process oils are a plasticizer that has been used in rubbers for decades. The process oils are hydrocarbon mixtures which boil in the lubricating oil sector, but are usually not used as or in conjunction with lubricating oils.

The process oils are extracted from petroleum refining. The crude oil (1) is subjected to atmospheric distillation (2) to separate as distillate (3) (one or more) products which boil under normal pressure to about 350 ° C. These products are often referred to as gas, naphtha and / or kerosene. As residue (4) after distilling off, a mixture of bitumen, asphaltenes, waxes and heavy oils is obtained. The heavy oils are processed into various products, in addition to lubricating oils to the mentioned plasticizers. Since aromatic process oils are still relatively inexpensive as plasticizers, their use was not questionable until some time ago. The relatively inexpensive production is based on the fact that the aromatic process oils are obtained as a by-product in the production of base oils for lubricating oils.

Process oils are used in particular as additives for rubbers. The group of rubbers is broad. Natural rubbers are elastic polymers based on plant products, especially latex. Through crosslinking, usually by vulcanization with sulfur, rubber is obtained from them. The most important natural rubber is polyisoprene. In order to meet the growing demand for rubber and to eliminate various disadvantages, such as that natural rubbers often contain proteins that can be converted to AI-CONFIRMATION COPY lustries, rubbers have increasingly been synthetically produced. Such synthetic rubbers are, for example, styrene-butadiene rubber (SBR), polybutadiene rubber (BR), ethylene-propylene-diene rubber (EPDM) and nitrile rubber (NBR). Various other synthetic rubbers based on different monomers are known. Today, about 60% of the global demand for rubber is covered by synthetic rubbers. Synthetic rubbers are used to a substantial extent for the production of car tires.

Since many rubbers crystallize and stiffen in the cold, special plasticizers are often used. Plasticizers also have other advantages. Since they are relatively small compared to the macromolecules of which the rubbers make up, they can interpose themselves between the chains and, as a kind of spacer, increase their mobility. They reduce the hardness and the tension values of the elastomeric rubbers. As a plasticizer for vehicle tires and to improve the elasticity, which in particular an increased slip resistance is associated, one uses in particular mineral oil plasticizers. Mineral oil plasticizers are also used to improve the damping properties of engineering rubber products. The process oils according to the invention can be used as plasticizers in rubbers.

It means:

 PCA (polycyclic aromatics): The PCA content describes the content of polycyclic aromatics which are extractable by DMSO (dimethyl sulfoxide). The polycyclic aromatics include those aromatic hydrocarbons containing more than three fused aromatic rings. This includes heterocyclic compounds with sulfur and / or nitrogen. In addition, the rings may be substituted by alkyl and / or cycloalkyl groups. The analytical determination of PCA is generally done by the method according to IP-346.

C _A (content of aromatic hydrocarbons): The C _A (aromatics content) refers to the ratio of the amount of carbon atoms that are part of aromatic rings to the amount of carbon atoms in the oil as a whole. For the determination of the Aromatics content exist various methods, uA is often the method according to ASTM D 2140 used.

DAO (deasphalted oil): A deasphalted oil (or deasphalted oil) is the product of a so-called deasphalting. An extraction with saturated aliphatic hydrocarbons is carried out to remove the asphaltenes. The asphaltenes consist predominantly of layers of condensed aromatic compounds which are connected to one another via aliphatic chains. Asphaltenes contain high levels of nitrogen and sulfur.

Since such studies have shown that some of the process oils contain up to 40 or 50% by weight of polycyclic aromatics (PCA), and it has been found that these polycyclic aromatics are carcinogenic, there is a need for substitutes.

The carcinogenicity of process oils with higher PCA levels is especially problematic because the plasticizer evaporates over time from the rubber, a process that is promoted primarily by direct UV irradiation and heat. Measurements have shown that more than 10% plasticizer can be washed out of the tire tread within two years. In particular, since process oils are used as plasticizers in many other areas in addition to tire production or find other applications, such. Use as carrier oils for printing inks, plasticizers or extender oils for rubbers and rubber compounds in general, both artificial and natural, results in the necessity of treating these process oils with high contents of polycyclic aromatics against those with a PCA content <3%, determined according to the IP rating. 346 method, because this is the limit above which a carcinogenic effect has been detected.

Process oils as plasticizers for rubber mixtures with a low content of polycyclic aromatics of less than 3% by weight, determined by the IP-346 method, are known to the person skilled in the art. Known process oils with a low PCA content are, for example, TDAE (Treaten Distillate Aromatic Extract) and MES (Mild Extracted Solvate).

To obtain a conventional TDAE, a method as shown in FIG. 1 is usually used. Crude oil (1) is subjected to atmospheric distillation (2) to remove gas, naphtha and kerosene fractions (3). The atmospheric residue (4) is removed by vacuum distillation (5) to a vacuum residue (7) and one or more distillates (6) ) separated. The distillate (6) is then separated in an extraction (17) with a suitable solvent into a raffinate (18) and an extract (primary extract) (19). From the raffinate (18) base oil and waxes are obtained. Further extraction (20) of the primary extract (19) yields the TDAE (21), it being possible, with a suitable choice of the reaction conditions, to obtain a process oil which has a content of polycyclic aromatics <3% by weight. In addition, in the second extraction (20), another extract (secondary extract) (22) is produced.

EP 1 148 112 A2 describes a process for preparing a process oil with a content of polycyclic aromatics <3% by weight, in which process the residue of the vacuum distillation is used to obtain the desired product. A crude oil is subjected to distillation under reduced pressure, with the end point of the distillate being at least 580 ° C under atmospheric pressure and boiling at least 450 ° C below atmospheric pressure. The residual oil is deasphalted so that the carbon residue in the DAO reaches 1.6% or less. In a further step, refining takes place by solvent extraction under the condition that the yield is between 35 and 60%. By this method, a process oil is obtained, which has a high viscosity between 50 and 100 mm ² / s, a C _A value of 15 to 35% and a PCA content <3 wt .-%, determined by the IP-346 method , contains. A disadvantage of this process oil is that due to its high viscosity uniform distribution in the rubber or in the rubber mixture is difficult to achieve. Also, a process as described in EP 1 148 112 A2, due to the strong dependence of the C _A value on the PCA content of the process oil, does not allow the production of a process oil with a very low content of polycyclic aromatics at a simultaneously very high C _A value. However, a very high C _A value would be desirable as the miscibility and solvent power of the process oil in the rubber increases with increasing C _A value.

An aromatic hydrocarbon content index is the aniline point of a process oil. A high aniline point means a low content of aromatic hydrocarbons. However, the lower this content is, the lower the affinity of the oil to the rubber or to the rubber mixture.

The object of the invention is therefore to provide a process for the preparation of an improved process oil, wherein the process oil should have a content of polycyclic aromatics of <3 wt .-% and the highest possible CA value and this process oil has a viscosity lower than 50 mm ² / s than the aforementioned conventional process oils with a low PCA content.

The object is achieved by a method for producing a refined, extracted and possibly dewaxed process oil having a content of polycyclic aromatic <3 wt .-%, determined by the IP-346 method, wherein first a bright stock extract according to the following steps are made:

 A) vacuum distillation of a crude oil to obtain a vacuum residue (-) (step A),

 B) deasphalting the vacuum residue from step A (step B) by treating the vacuum residue, preferably in a deasphalting plant, whereby a deasphalted oil and a residue are obtained,

 C) extraction of the deasphalted oil from step B in an extraction plant to give a bright stock extract and a raffinate (step C), which is then e.g. to be further processed by dewaxing to brightstock, characterized in that

D) extracting the obtained bright stock extract (RAE) from step C or a mixture of the brightstock extract with one or more oils in a further process step D, for example in an extraction plant, resulting in a TRAE and a secondary extract. The TRAE can then be mixed with other process oils (eg TDAEs) for the desired properties. Furthermore, the secondary extract may also be mixed with other secondary extracts before step D is performed in the extraction plant, or the secondary extract may be mixed with other aromatic oils and extracted by a wide process step D.

Steps C and D can be carried out in the same or in different extraction plants. Furthermore, the extraction equipment used to make TDAE from vacuum distillates may be the same or different from the extraction equipment.

According to the invention is understood as:

 TDAE (Treated Distillate Aromatic Extract): This is the treated aromatic extract from a treated distillate. A TDAE has a low PCA content of <3% by weight.

Brightstock extract: This is often referred to in the literature as RAE (Residual aromatic extract). The brightstock extract is obtained by the following steps: vacuum distillation of a residue from atmospheric distillation, deasphalting of the vacuum residue and extraction of the deasphalted oil.

TRAE (Treated residueal aromatic extract): This is the aromatics extract from a treated vacuum residue treated according to the invention. So this is a treated RAE. A TRAE has a low PCA content of <3% by weight.

Further embodiments are the subject matter of the subclaims or described below.

The deasphalting of the vacuum residue is carried out with non-polar solvents, preferably in a propane deasphalting plant (PDA). Through the PDA By means of an extraction under pressure, a separation of bitumen and asphalt from the further processed oil, wherein the resulting oil is referred to as DAO. Usually, a temperature of at least 100 ° C is used in this extraction, so that the vacuum residue dissolves in the solvent. The light hydrocarbon propane as solvent dissolves aliphatic components, but not the asphaltenes. A PDA delivers a very high quality DAO.

Extraction of the deasphalted oil (DAO), in addition to the so-called brightstock raffinate from which the brightstock and the brightstock slack waxes are obtained, provides the brightstock extract (RAE).

As extraction, countercurrent extraction is preferably carried out. The extraction column used in this case can be designed in various ways.

For extraction, polar solvents are used. In principle, any polar solvent which is customarily used in the processing or refining of lubricating oil, or mixtures thereof, is suitable as the solvent. In particular, as a solvent for the extraction of the brightstock extract or the mixture of a brightstock extract and one or more oils, furfural, N-methylpyrrolidone and phenol are suitable. Particularly preferred furfural is used.

In one embodiment of the process according to the invention, the product produced moreover has a C _A value> 25%, preferably> 28%, determined by the method according to ASTM D 2140. The method thus makes accessible a process oil which is not only free of labeling but also It is also particularly easy to distribute homogeneously in the rubber or in the rubber mixture.

In general, as in the solvent extraction of distillates, also in the extraction of bright stock extract or the mixture with other aromatic oils primarily continuous extraction processes are used in the same or similar design and in the same or similar design, discontinuous process variants are also possible. However, the ratio of extractant used to the feedstock is significantly lower than in the preparation of known Base oil raffinates and base oils which are prepared by the route of solvent refining. Other process parameters, such as temperature, may differ as well as changes in solvent mixtures to affect their solvent power and selectivity.

Preferably, a process oil is obtained as the product of the process according to the invention, which is referred to as TRAE.

Since the carcinogenic effect of polycyclic aromatics has become known, oils with a higher PCA content are to be labeled for the indication of their toxic effect. The method according to the invention thus gives a TRAE which is guaranteed free of labeling.

Before the second extraction (process step D), which supplies the TRAE from the bright stock extract, it is possible to mix the bright stock extract with one process oil or several process oils, which usually does not occur due to dependence between PCA content and C _A value alone by extraction to a high quality, higher aromatic TDAE according to the requirements for use in rubber compounds. For example, the C _A value should usually be greater than 20, preferably 25% by mass, in order to ensure good incorporation into the rubber matrix and good compatibility therewith. Certain process oils have a too low C _A (aromatics content) value, which also lowers the C _A values below the requirements of compatible TDAEs by the methods of extraction to reduce PCA levels. This correlation of the two properties always goes hand in hand.

Surprisingly, with the process according to the invention, these process oils can also be processed by mixing with the brightstock extract to give a process oil having very good properties. The ratio of Brightstock extract to less high-grade oil should preferably be about 20:80 to 70:30. As a result, yields of process oils (TRAE or mixtures of TRAE and TDAE) of between 60 and 70% can be achieved. The process oils produced by the process according to the invention are preferably used as plasticizer or extender oil for natural or synthetic rubber or rubber products, preferably for tires and / or technical rubber goods.

In this case, preference is given to using so much plasticizer that the rubber product / the rubber contains from 1 to 45 phr of plasticizer. The unit "phr" is a unit common in the rubber industry and means "per hundred rubber". 1 phr thus corresponds to one part by weight of a substance, in the present case a process oil as plasticizer, per 100 parts by weight of the total rubber.

When using the process oils for tires produced by the process according to the invention is preferably used within the following concentration ranges: for treads of a car tire: 25 to 45 phr; for treads of a truck tire: 10 to 20 phr plasticizer.

A process oil produced by the process according to the invention can also be treated with a second process oil whose PCA content is <3% by weight, determined by the IP-346 method, and whose C _A value is> 25%, preferably ^ 28%, is, according to the method ASTM D 2140, mixed. The mixing ratio is preferably between 10:90 TRAE to second process oil, more preferably 40:60 to 60:40. This second process oil is preferably prepared by a process comprising the following process steps: 1. Distillation of a crude oil, 2. Extraction of the distillate obtained by step 1; 3. extraction of the extract obtained by step 2.

The inventive method is shown by way of example in FIG. The process according to the invention follows, for example, a process for the recovery of TDAE, as is known from FIG. According to the invention, a vacuum distillation of a crude oil is carried out to obtain a vacuum residue (7). Then the deasphalting of the vacuum residue by treatment of the vacuum residue (7) in a deasphalting plant (8), wherein a deasphalted oil (9) and a residue (10) is obtained. This is followed by extraction of the deasphalted oil (9) in an extraction plant (11) to obtain a bright stock Extract (13) and a raffinate (12). The raffinate (12) can then be further processed eg by deproteinization to bright stock. The obtained bright stock extract (13) (RAE) is extracted either in an extraction unit (14), resulting in a TRAE (15) and a secondary extract (16). Furthermore, the bright stock extract (13) may also be mixed with other extracts (19) before the extraction step (step D) is performed in the extraction plant (14), or the bright stock extract (13) may be mixed with other aromatic oils (23) and extracted by a further process step D.

example 1

 According to the invention, a bright stock extract (RAE) was treated in a countercurrent extraction plant with the solvent furfurol. Here, a solvent ratio of 120% (furfurol based on RAE) at a column temperature and a pressure of 1 bar was used. The speed of the rotor in the extraction column was 250 revolutions per minute.

The essential properties of the starting material (RAE) and of the TRAE obtained according to the invention are summarized in Table 1. The yield in the extraction was 77%.

ten TRAEs Example 2

In a further experiment, the TRAE prepared according to Example 1 was mixed with a process oil of the MES (Mild Extracted Solvate) type. The MES had a C _A content (according to ASTM D 2140) of 9% and was therefore not well suited for rubber compounds.

The mixture was carried out in a ratio of 55% MES and 45% TRAE. The essential data of the process oil of the type MES and the corresponding mixed product are listed in Table 2. As can be seen from Table 2, the blend has a C _A content of 25% according to ASTM D 2140 and is thus well suited for rubber compounds.

 Table 2: Mixture of a process oil of type MES with a TRAE

Example 3

In a further experiment, the TRAE prepared according to Example 1 was mixed with a process oil of the type TDAE (Treated Distillate Aromatic Extract). The TDAE had a C _A content (according to ASTM D 2140) of 23% and was thus conditionally suitable for rubber compounds.

The mixture was carried out in a ratio of 80% TDAE and 20% TRAE. The essential data of the TDAE process oil and the corresponding mixed product are listed in Table 3. As can be seen from Table 3, the blend has a C _A content of 25% according to ASTM D 2140 and is thus well suited for rubber compounds. TDAE blend TDAE / TRAE

Density 15 ° C [kg / m ³ ] 934.8 942.7

Viscosity 100 ° C [mm ² / sec] 12.4 17.8

 PCA content according to [M%] 2.5 2.4

 IP 346

C _A (ASTM D 2140) [M%] 23 25

 Table 3: Mixture of a process oil of type TDAE with a TRAE

Example 4

In a further experiment, the TRAE prepared according to Example 1 was mixed with another process oil of the type TDAE (Treated Distillate Aromatic Extract). The TDAE had an already C _A content (according to ASTM D 2140) of 25% and was thus well suited for rubber compounds.

The mixture was carried out in a ratio of 50% TDAE and 50% TRAE. The essential data of the TDAE process oil and the corresponding mixed product are listed in Table 4. As can be seen from Table 4, the mixture has a C _A content of 28% according to ASTM D 2140 and is thus outstandingly suitable for rubber mixtures.

 Table 4: Mixture of a process oil of type TDAE with a TRAE

Example 5:

In a further experiment, in a countercurrent extraction plant with the solvent furfurol, a TDAE from a DAE was first prepared using a solvent ratio of 110% (furfurol / DAE) and a column temperature of 44 ° C. The throughput in this example was 470 tons / day.

The essential properties of the starting material (DAE) and of the TDAE obtained are summarized in Table 5. The extraction yield was 58%.

Table 5: Preparation of a TDAE

To demonstrate the effect of adding RAE to a DAE on the achievable yield of non-marking process oils, the experiment was continued. In this case, a DAE similar to the starting material of the first extraction was mixed with an RAE in the ratio DAE: RAE = 91: 9. This mixture was then treated with furfurol in the same countercurrent extraction unit using a solvent ratio of 120% (furfurol: feed oil mixture). The throughput in this case was 745 tons / day.

The non-marking process oil in this experiment is a mixture of a TDAE and a TRAE. The essential properties of the starting materials and of the resulting non-marking process oil are summarized in Table 6. The yield could be increased in this example by 2%, although only an admixture of 9% was carried out and the system throughput was increased by 67% This was surprising in that an increase in the plant throughput usually results in a lower yield. DAE RAE identification fr.

 process oil

Density 15 ° C [kg / m ³ ] 981, 3 984.2 946.8

Viscosity 100 ° C [mm ² / sec] 26.5 43.0 19.7

PCA content according to [wt%] 2.8 IP-346

C _A (ASTM D2140) [wt%] 26

 Table 6: Preparation of a labeling-free process oil

Claims

Patent claims 1. Process for producing a refined, extracted and, if necessary, dewaxed process oil which has a polycyclic aromatic content of <3% by weight, determined according to the IP-346 method, wherein a brightstock extract is first prepared according to the following steps: A) vacuum distillation of a crude oil to obtain a vacuum residue, B) deasphalting the vacuum residue from step A, C) extraction of the deasphalted oil from step B to obtain a brightstock extract, characterized in that in a further process step D, the brightstock extract from step C or a mixture of the brightstock extract and one or more oils is extracted. 2. Method according to claim 1, characterized in that the finished process oil to be produced has a C _A value > 25%, preferably 28%, determined by C _A analysis according to the ASTM D 2140 method. 3. Method according to claim 1 or 2, characterized in that the process oil, which is obtained as a product, is a TRAE. 4. Method according to one of the preceding claims, characterized in that to produce the mixture of the Brightstock extract and one or more process oils, a process oil/oils are used whose C _A value is greater than 20% and whose polycyclic aromatic content is greater than 3.0 wt. -% is. 5. Method according to one of the preceding claims, characterized in that the deasphalting of the vacuum residue is preferably carried out by extraction with propane. 6. Process oil mixture a) a first process oil, produced by a method according to one of claims 1 to 5, and b) a second process oil with a content of polycyclic aromatics <3% by weight, determined according to the IP-346 method, and a C _A value > 25%, preferably > 28%, determined by C _A analysis according to ASTM D 2140. 7. Process oil mixture a) a first process oil, produced by a method according to one of claims 1 to 5, and b) a second process oil with a content of polycyclic aromatics <3% by weight, determined according to the IP-346 method, and a C _A value <25%, determined by C _A analysis according to ASTM D 2140, characterized in that the finished process oil mixture has a content of polycyclic aromatics <3% by weight, determined according to the IP-346 method, and a C _A value > 25%, determined by C _A analysis according to ASTM D 2140. 8. Process oil mixture according to claim 6 or 7, wherein the second process oil is produced by the process steps . distillation of a crude oil, 2. Extraction of the distillate obtained through step 1, 3. Extraction of the extract obtained by step 2. 9. Use of a process oil, produced by a method according to one of claims 1 to 5, or a process oil mixture according to one of claims 6, 7 or 8 as a plasticizer or extender oil for natural or synthetic rubber or rubber products, preferably for tires and / or technical rubber products . 10. Use according to claim 8, characterized in that the rubber product/rubber contains 1 to 45 phr of plasticizer. 11. Use according to claim 9 or 10 as a plasticizer for tires, characterized in that the tread of a car tire is 25 to 45 phr and the The tread of a truck tire contains 10 to 20 phr of plasticizer.