JPS6123602B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrical insulating oil with particularly improved oxidation stability, and more specifically to an electrical insulating oil in which an alkylbenzene base oil contains a non-basic nitrogen content and a basic nitrogen content within a specific range. More specifically, it is an electrical insulating oil in which a base oil consisting of alkylbenzene or alkylbenzene and mineral oil contains a non-basic nitrogen content of a specified amount or more, while the basic nitrogen content is limited to a specified amount or less. Electrical insulating oil is used for long-term filling in high-voltage equipment such as transformers, high-voltage cables, high-voltage circuit breakers, and capacitors, but recently, in order to carry out economical large-capacity power transmission, electrical insulating oil has been used to fill high-voltage equipment such as transformers, high-voltage cables, high-voltage circuit breakers, and capacitors. With the introduction of power transmission technology, there is a demand for electrical insulating oils that have better oxidation stability and flow antistatic properties than ever before. Electrical insulating oils based on alkylbenzene or a mixture of alkylbenzene and mineral oil have an antistatic effect in addition to improving the pour point, and although alkylbenzene itself has significantly lower oxidation stability than mineral oil, both It is known that the drawbacks of alkylbenzene can be compensated for by mixing them. However, the total acid value (hereinafter simply referred to as acid value) after the oxidation stability test (JIS-C-2101) of the previously known alkylbenzene-based electrical insulating oil is only about 0.2 mgKOH/g. Although it satisfies the JIS standard values, it is unsatisfactory as an electrical insulating oil for high-voltage power transmission, and better oxidation stability performance is required. In the lubricating oil fraction distilled from crude oil, for example, in the case of Middle Eastern crude oil, the total nitrogen content is about 350~
Nitrogen compounds are traditionally considered to be undesirable components in lubricating base oils.
A combination of hydrorefining, solvent extraction refining, solid adsorption refining, or sulfuric acid washing refining has been employed to remove as much nitrogen as possible. Therefore, the total nitrogen content in conventionally known electrical insulating oils with good oxidation stability is often limited to several ppm or less (for example, Japanese Patent Application Laid-open No. 40799/1983), and the U.S. patent Publication No. 3759817 states that the total nitrogen content is
It is also disclosed that the basic nitrogen content should be limited to 20 ppm or less, and the basic nitrogen content should be limited to 5 ppm or less. However, no idea has been found to improve oxidation stability by actively incorporating non-basic nitrogen. The inventor's detailed research has shown that reducing the basic nitrogen content while leaving the non-basic nitrogen content allows even base oils with poor oxidation stability, such as alkylbenzene, to exhibit extremely excellent performance. It was found to be effective. The present invention was completed as a result of research based on the above background. That is, the present inventors have found that an electrical insulating oil with excellent oxidation stability can be obtained by selectively containing non-basic nitrogen among the nitrogen contained in crude oil and removing basic nitrogen. This discovery led to the completion of the present invention. An object of the present invention is to provide an electrical insulating oil with significantly superior oxidation stability. The present invention provides an electrical insulating oil based on alkylbenzene or a mixture of alkylbenzene and refined mineral oil, which contains at least 16 ppm or more of non-basic nitrogen in the base oil, and in which the basic nitrogen is replaced by the non-basic nitrogen. This electrical insulating oil is characterized by being limited to 6% or less. The content of the present invention will be explained in detail below. The base oil constituting the electrical insulating oil of the present invention is an alkylbenzene or a mixture of an alkylbenzene and a refined mineral oil. However, poly α-olefin,
Even if a known synthetic base oil such as bolybdenum, alkylnaphthalene, alkyl diphenylethane, or silicone oil is mixed as an auxiliary, the effect is sufficiently exhibited. Non-basic nitrogen content (hereinafter referred to as
Nn) should be at least 16 ppm or more, and the basic nitrogen content (hereinafter Nb) should be limited as low as possible. The total amount of Nn and Nb is called the total nitrogen content (hereinafter abbreviated as Nt), and in the present invention, Nt
The main body of is Nn, and Nb should be limited as much as possible. Nn, Nb, Nt are measured by the following method,
The values measured by this method are also used in the present invention. Total nitrogen content (Nt): A value measured by the method specified in JIS-K-2609-1980 "Nitrogen content testing method for crude oil and petroleum products", and is commonly referred to as total nitrogen or simply nitrogen content. Basic nitrogen content (Nb); American UOP company test method (UOP
Method）No.313―70 “Nitrogen Bases in
Petroleum Distillates by Color Indicator
This is the value measured by the method specified in "Titration". This measurement method involves dissolving the sample oil in glacial acetic acid and using crystal violet as an internal indicator.
This method involves titration using perchlorine content in glacial acetic acid. Non-basic nitrogen content (Nn): Calculated from the above Nt and Nb by the following formula. Nn=Nt-Nb As mentioned above, Nn is a nitrogen component that cannot be titrated with a strong acid, so it is an organic nitrogen compound that has very weak basicity or does not show basicity.
The effect of Nn can be improved by adding Nn concentrate separated from mineral oil to alkyl bezene or by purification means.
This can be confirmed by mixing refined mineral oil with altered Nn and Nb contents with alkylbenzene and removing Nb using activated clay. The alkylbenzene used in the present invention is a mono-, di-, or trialkylbenzene having a total of 9 or more carbon atoms in the side chain alkyl group or a mixture thereof, and is usually a straight chain (soft) or branched (hard) for synthetic detergents. For the synthesis of alkylbenzene, it is produced by reacting benzene with a light olefin, such as a propylene oligomer, or by reacting benzene with a long-chain α-olefin or a long-chain halogenated normal paraffin. For example, the use of alkylbenzene as a lubricating oil base oil
It is disclosed in Publication No. 19084. The insulating base oil of the present invention preferably has a viscosity (at 40° C.) in the range of 5 to 30 cSt, and for example, heavy alkylbenzene bottom oil (kettle residual oil) is used. A high viscosity oil is mixed with a low viscosity refined mineral oil, while a low viscosity oil is mixed with a high viscosity refined mineral oil to obtain an electrical insulating oil of appropriate viscosity. The acid value of the alkylbenzene synthesized by the above method after JIS-C-2101 oxidation stability is usually about 5 to 9 mgKOH/g.
It is about 10 to 20 times higher than that of refined mineral oil, so improvement is necessary. The refined mineral oil used in admixture with the alkylbenzene is a lubricating oil fraction separated from conventional crude oil. The crude oil species may be paraffin groups, naphthenic groups, or mixed groups, but mixed group systems are preferably used from the standpoint of stable availability. The refined mineral oil to be mixed and used is a refined lubricating oil fraction having a viscosity of about 7 to 30 cSt (@40°C) separated by distillation from the above-mentioned crude oil. The mixing ratio of alkylbenzene and refined mineral oil is
When the ratio is in the range of 20:80 to 100:0 (volume %), the properties of alkylbenzene are effectively exhibited. That is,
By adding alkylbenzene to 20 vol% or more of the total base oil, fluid antistatic properties, corona resistance,
Low-temperature properties are effectively demonstrated. Electrical insulating oils that require high-speed circulation for cooling and heat dissipation, such as transformer oil used to fill ultra-high-voltage or ultra-super-high-voltage power transmission transformers, are easily charged during flow and are used under harsh conditions, making the use of alkylbenzenes important. . Figure 1 shows an example in which the oxidation stability of electrical insulating oil containing Nn by adding Nn concentrate separated from mineral oil to alkylbenzene was measured using an oxygen absorption method. However, the pressure drop was only about 20 mmHg. Electrical insulating oil that is made by mixing alkylbenzene with refined mineral oil that selectively contains Nn using appropriate refining methods to increase Nn also has extremely excellent oxidation stability; for example, it is composed of 30 vol% alkylbenzene and 70 vol% refined mineral oil. When the electrical insulating oil had Nn of 25.3 ppm and Nb of 0.7 ppm, the acid value after the oxidation stability test according to JIS-C-2101 could reach 0.04 mgKOH/g. When alkylbenzene was mixed with mineral oil whose Nb content was changed depending on refining conditions, the presence of Nb led to an increase in the acid value. The Nn content in the electrical insulation of the present invention is 16 ppm or more, which is based on the viewpoint of practical oxidation stability performance, and the acid value of JIS-C-2101 is 0.20 mg.
This was established with the purpose of ensuring KOH/g or less. In other words, even if Nn is less than 16 ppm, if Nb is limited to an extremely low concentration, considerable performance can be achieved, for example, with an acid value of 0.25~
Although 0.30mgKOH/g can be achieved, it is insufficient for an electrical insulating oil that can be used stably under severe conditions.
According to the results of adjusting electrical insulating oils with varying Nn content up to 504ppm, the desired performance cannot be achieved with Nn of 10ppm to 12ppm, but this can be achieved by increasing Nn to 16ppm or higher. Moreover, in the range up to about 100 ppm, the induction period becomes longer as the Nn increases, and reaches an equilibrium state in the range of 100 to 200 ppm.
Above 200 ppm, the induction period decreased slightly. However, the acid value of JIS-C-2101 test is Nn16ppm.
0.20mg stably in the range of 504ppm
Achieved KOH/g or less, and also exhibited performance of 0.05mgKOH/g or less. Even if Nn is present in a specified amount or more, if a small amount of Nb is present, the desired electrical insulating oil cannot be obtained. Therefore, Nb should not be present as much as possible. Nn
Based on the results of oxidation stability tests using sample oils with varying concentrations of Nb and
2ppm or less, more preferably 1.5ppm or less, still more preferably 1.0ppm or less is required for oxidation stability performance or higher, and if Nn is several tens of ppm to 100ppm, Nb2~
It was recognized that the upper limit is 3 ppm, and even when Nn is 200 to 500 ppm, the upper limit should be 3 to 5 ppm. Therefore, Nb concentration should be kept as low as possible, but Nn
The upper limit varies somewhat in relation to
If Nn is less than about 50ppm, Nb is less than 6% of Nn,
More preferably 5% or less, even more preferably 4% or less, Nn is 50 to 100pm, 5% or less, more preferably 4% or less, still more preferably 3% or less, Nn
In the range where Nb exceeds 100 ppm, Nb needs to be limited to 5 ppm or less, more preferably 3% or less, that is, Nb needs to be limited to 4% or less of Nn, more preferably 3% or less. For producing the electrical insulating oil of the present invention, any of the following means is employed. (b) Blending Nn concentrate separated from mineral oil into base oil. (b) Mixing of refined mineral oil from which Nn is selectively left and Nb has been removed by means of refining. (c) A combination of means (a) and (b). The method (a) is preferably applied when the base oil is alkylbenzene or a mixture of alkylbenzene and highly refined mineral oil. That is, it is a means of producing an electrical insulating oil containing a specified amount of Nn by adding and blending a Nn concentrate as an additive to a base oil that does not contain either Nn or Nb or contains only a very low concentration. The means (b) above uses refined mineral oil from which Nn is selectively left and Nb is removed by a refining means as a base oil, which is mixed with alkylbenzene, and the base oil after mixing is made to contain a specified amount of Nn. This is a means of making it into an electrically insulating oil. Means (c) applies to products manufactured by means (b).
This is a means of blending a concentrate to create an electrical insulating oil containing a specified amount of Nn. Nn concentrates separated from mineral oil exhibit favorable oxidative stability enhancing effects. The concentrate is made from a vacuum distillate of crude oil or an oil obtained by hydrorefining it, treated with activated clay, then treated with silica gel, and the silica gel is mixed with a light hydrocarbon solvent such as pentane or a mixed solvent of methylene chloride/pentane. It is obtained by sequentially washing with water, followed by elution with a mixed solvent of methanol/methylene chloride, and evaporating the solvent in the eluate. The Nn concentrate exhibits favorable solubility. Since the concentration of Nn in the concentrate is high, addition of a small amount is sufficient. To obtain conventionally refined mineral oil base lubricant base oils,
Solvent extraction (abbreviated as EX), hydrogenation treatment (abbreviated as HF), solvent dewaxing (abbreviated as DW), solid adsorption treatment (abbreviated as CA), sulfuric acid cleaning (abbreviated as SW), solvent deasphalting (abbreviated as SD) ), etc., have been carried out by a combination of two or more of the following methods. A refined mineral oil selectively containing Nn can be obtained based on any of the flows shown in FIG. In the same figure, V・O is a lubricating oil fraction separated by distillation from crude oil, that is, the residual oil from atmospheric distillation of crude oil is further vacuum distilled to produce 1 side oil, 2 side oil, 3 side oil, etc. according to the viscosity classification. This includes fractionated oil or deasphalted oil obtained by deasphalting residual oil from vacuum distillation using light hydrocarbons such as propane. For producing low viscosity insulating oil, the first side oil may be further distilled and divided. In the upper stage of each flow shown in the figure, for example, (V
O) → HF → EX → DW → CA is a conventional method for obtaining refined mineral oil (base oil), and in this process, refined base oil (referred to as first refined mineral oil) in which not only Nb but also Nn is highly removed is obtained. ) can only be obtained. The lower part of each flow (~) is a refining process that does not go through the EX process, but the refined base oil obtained by this process (referred to as the second refined mineral oil) is mixed with the first refined mineral oil at an appropriate mixing ratio, at least By mixing after the EX step, a refined mineral oil that selectively contains Nn and removes Nb can be obtained. Not going through the EX process means not making the desulfurization too harsh, and if the extraction conditions are mild and the extract yield is about 30 vol% or less, then EX is not necessary to obtain the second refined mineral oil. There is no problem with process processing. In Figure 2
DW is not important for the purpose of the present invention since it is only intended to lower the pour point and does not participate in the adjustment of Nn. The refined mineral oil obtained by the method shown in Figure 2 is used in combination with alkylbenzene. The value of Nn in refined mineral oil is determined by the mixing ratio of the first and second refined mineral oils, HF,
EX and/or CA processing conditions can be set arbitrarily, and the sulfur content in refined mineral oil is mainly HF and/or
Can be set arbitrarily using EX processing conditions. In the HF process,
Contact treatment is carried out under a known hydrogenation catalyst supporting one or more of Ni, Ti, Mo, Co, W, etc. under hydrogen pressure of 20 to 100 Kg/cm ² (gauge) and temperature conditions of 280 to 380°C, In the EX process, furfural, N-methyl-
Undesirable components are extracted and removed as an extract using a known solvent having an affinity for aromatic hydrocarbons such as 2-pyrrolidone and phenol. HF
In the and EX steps, sulfur and nitrogen are removed to a considerable extent, but only Nb cannot be selectively removed. The Nt in oil that has gone through the EX process is usually about 20~
70ppm, Nb approx. 10-60ppm, S approx. 0.1-0.6wt%
By further performing CA treatment, Nb
is almost completely removed, and the Nn content in the oil after CA treatment is highly refined to about 10 ppm or less. This refined mineral oil can be mixed with alkylbenzene, but in order to contain more than a specified amount of Nn, it is necessary to adjust it by adding Nn concentrate. Nn
A refined mineral oil selectively containing can be obtained by mixing a second refined mineral oil with a first refined mineral oil. As shown in each flow in Figure 2, the second refined mineral oil is a refined mineral oil obtained without EX treatment or under mild conditions, so it contains a high degree of Nn and is moderately refined. Therefore, by mixing with the first refined mineral oil, a refined mineral oil that selectively contains Nn is obtained. Therefore, by mixing the refined mineral oil with alkylbenzene, the resulting electrical insulation has a Nn content of 16 ppm or more, exhibiting favorable performance. Refined mineral oil that selectively contains Nn and has limited Nb can be used as it is or mixed with alkylbenzene in an intermediate process, but as another method for producing the electrical insulating oil of the present invention, for example, the flowchart shown in FIG. A method is adopted in which only the second refined mineral oil or V.O shown in 2 is mixed with alkylbenzene, and then a severe CA treatment is performed to remove Nb. In this case, although a large amount of solid adsorbent may be required in the CA treatment, an electrical insulating oil with excellent oxidation stability can be obtained because unstable components in the alkylbenzene can be removed at the same time. When adjusting Nn in a mixed electric insulating oil of refined mineral oil and alkylbenzene by mixing it with refined mineral oil, the mixing ratio of refined mineral oil depends on the Nn content in the refined mineral oil, but for example,
If Nn is approximately 200 ppm, it may be mixed with the alkylbenzene in an amount of approximately 7 to 8 vol% or more, and if Nn is approximately 50 ppm, it may be mixed in approximately 30 vol% or more. The sulfur content in the electrical insulating oil of the present invention depends on the degree of refining of the mineral oil and the mixing ratio with alkylbenzene.
It can be set arbitrarily within the range of 0.02 to 0.7wt%. Conventional electrical insulating oil was designed not to selectively leave Nn, but to reduce Nt.
Both HF and EX are processed under harsh conditions, and therefore the sulfur content has been stolen at low concentrations, but in the present invention, the sulfur content is limited as long as it does not cause corrosiveness to metals. There is no need to give special consideration to
There is no problem in the range of 0.02 to 0.7 wt%. Furthermore, for example, a phenol-based or amine-based synthetic antioxidant may be added. The contents of the present invention will be explained below based on examples. Example 1 Hard alkylbenzene (manufactured by Mitsubishi Yuka, trade name Pansolve H) and refined mineral oil whose basic nitrogen content (Nb) and non-basic nitrogen content (Nn) were adjusted by the following method were mixed in a ratio of 30:70, respectively. (capacity ratio) to obtain electrical insulating oil. Method for producing refined mineral oil: Vacuum distillate of Kuwaiti crude oil (viscosity @40℃
12.49cSt, sulfur content 2.46wt%, Nt420ppm,
Using a Ni-Co-Mo supported alumina catalyst, the hydrogen pressure was 35 Kg/cm ² (gauge pressure) and the temperature was 335.
℃, space velocity (LHSV) 1.5hr ^-1 to obtain HF oil, and then solvent extraction using furfural solvent (solvent ratio 250%, temperature 45℃)
and obtained EX oil. Next, add the HF oil and EX oil obtained earlier.
The mixture was mixed at a ratio of 20:80 (by volume), cooled to -40℃ in the presence of methyl ethyl ketone/toluene, and dewaxed.
1.5wt%) and refined mineral oil (Nt36ppm,
Nb 1ppm or less, sulfur content 0.36wt%). Table 1 shows the performance and properties of the electrical insulating oil according to this example. At the same time, the performance of a commercially available electrical insulating oil (a mixture of alkylbenzene and mineral oil, containing 30% by volume of alkylbenzene) is also listed.

【table】

[Table] Table 2 The electrical insulating oil of Example 1 has an acid value of 0.04mg
KOH/g, demonstrating unprecedented oxidation stability performance. Example 2 A first refined mineral oil and a second refined mineral oil were obtained based on the flowchart of FIG. 2, and by mixing these with the alkylbenzene used in Example 1, an electrical insulating oil was obtained. First refined mineral oil; The EX oil described in Example 1 was dewaxed by the above-mentioned means to obtain the first refined mineral oil shown in Table 2. Properties are shown in Table 2. Second refined mineral oil: The HF oil described in Example 1 was cooled to -40°C in the presence of methyl ethyl ketone and dewaxed to obtain the second refined mineral oil shown in Table 2. The first and second refined mineral oils and Example 1
The alkylbenzenes used in Table 3 were mixed as shown in Table 3, and the mixture was brought into contact with activated clay and treated to produce electrical insulating oil. The electrical insulating oil of the present invention containing specified amounts of Nn and Nb exhibited extremely excellent oxidation stability.

【table】

[Table] Example 3 A Nn compound concentrate obtained by the following method was added to the hard alkylbenzene used in Example 1 to produce electrical insulating oils with varying Nn content. Nn compound concentrate: Vacuum distillate oil (V・O) and HF oil used in Example 1 were treated with activated clay (Japanese activated clay), respectively.
Co., Ltd.'s white clay calcined at 140°C for 4 hours was added to the above oil in an amount of 5wt%, contacted in batches at 45°C for 1 hour), separated, and the oil was packed into a glass column using silica gel (Wako Gel C). -100 at 140℃ 5
Oil was passed through the silica gel (oil/silica gel = 1/1 (weight ratio)). The part adsorbed on silica gel was first eluted and washed with pentane, then methylene chloride and pentane (5:95v/v)
Wash and elute with a mixture (2 times the volume of silica gel), then wash and elute with 4 times the volume of the same mixture (15:85 v/v ratio), and then wash and elute with methanol/methylene chloride (15:85 v/v ratio). /v ratio) was eluted with the mixed solution. The eluate of methanol/methylene chloride mixture was heated and evaporated under a nitrogen gas flow to obtain a Nn concentrate. V.O.
The Nn in the Nn concentrate (Nc-C-VO) obtained from
1.22wt%, Nn concentrate obtained from HF oil (Nn-C-
Nn in HF) was 2.30wt%, and no Nb could be detected. Electrical insulating oils shown in Table 4 were produced by adding Nn concentrate to alkylbenzene.

【table】

[Table] The electrical insulating oil of the present invention can be produced by slightly changing the commonly used refining conditions, and has extremely excellent oxidation stability, so it can be used in transformers used under ultra-high voltage or ultra-super high voltage. It can be used for long-term filling, etc., and has extremely high industrial value.

[Brief explanation of the drawing]

Figure 1 shows the relationship between pressure drop and time in an oxygen absorption test of electrical insulating oils with varying amounts of non-basic nitrogen in the alkylbenzene. FIG. 2 is an illustration of the production flow of refined mineral oil that selectively contains non-basic nitrogen.

Claims (1)

[Scope of Claims] 1. An electrical insulating oil whose base oil is alkylbenzene or a mixture of alkylbenzene and refined mineral oil, which contains at least 16 ppm or more of non-basic nitrogen, and in which the basic nitrogen content is greater than the non-basic nitrogen content. Electrical insulating oil characterized by being limited to 6% or less of 2 The alkylbenzene content in the base oil is 20 or more.
The electrical insulating oil described in the preceding paragraph which is 100% by volume. 3. The electrical insulating oil according to claim 1, wherein the non-basic nitrogen content is nitrogen of a non-basic nitrogen compound naturally present in crude oil. 4 Refined mineral oil selectively containing non-basic nitrogen compounds is mixed with alkylbenzene, the non-basic nitrogen content is at least 16 ppm or more, and the basic nitrogen content is limited to 6% or less of the non-basic elements. A method for producing electrical insulating oil, characterized in that the electrical insulating oil is made into electrically insulating oil. 5 Hydrotreated refined mineral oil is mixed with alkylbenzene and then treated with a solid adsorbent so that it contains at least 16 ppm or more of non-basic nitrogen, and the basic nitrogen content is reduced to 6% or less of the non-basic nitrogen content. 1. A method for producing electrical insulating oil, characterized in that the electrical insulating oil is made into a restricted electrical insulating oil.