JPS5932512B2 - Method for producing electrical insulating oil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an electrical insulating oil having particularly excellent oxidation stability from paraffin base crude oil or mixed base crude oil.

More specifically, a distillate having a boiling point (in terms of normal pressure) in the temperature range of 250 to 400°C obtained by distilling a paraffinic base crude oil or a mixed base crude oil at atmospheric pressure, or by distilling a residual oil from atmospheric distillation under reduced pressure. The extracted oil is desulfurized by 50 to 80 wt% (weight percent) by hydrorefining at a temperature of 310 to 370°C, and the obtained hydrogenated oil is desulfurized to 40 to 80 wt% by hydrorefining at a temperature of 310 to 370°C.
Oxidation stability characterized by further subjecting the raffinate obtained by 0wt% desulfurization to a solvent film brazing treatment and, if necessary, subsequent clay treatment to make the sulfur content of the final product 0.1 to 0.4wt%. This invention relates to electrical insulating oil with good properties.

Conventionally, electrical insulating oil has been produced using naphthenic crude oil as a raw material oil, but as naphthenic crude oil tends to be depleted worldwide, it is becoming increasingly difficult to secure such crude oil in Japan, so paraffinic crude oil is being produced. Alternatively, there has been an increasing need to produce electrical insulating oil from mixed base crude oil.

However, even if the method for producing electrical insulating oil from naphthenic crude oil is directly applied to paraffinic crude oil or mixed crude oil, electrical insulating oil with good oxidation stability cannot be obtained.

This is natural since naphthenic crude oil and paraffinic crude oil or mixed base crude oil have different compositions, and a method for producing electrical insulating oil from paraffinic crude oil or mixed base crude oil must be found.

Conventionally, in Japanese Patent Publication No. 53-47242, the boiling point (converted to normal pressure) obtained from paraffin base crude oil or mixed base crude oil is 2.50°C.
Distillate oil in the temperature range from 400°C to 30 to 75 wt% is first desulfurized by solvent refining, and the resulting raffinate is then hydrorefined to desulfurize 40 to 90 wt%, and further dewaxed if necessary. A method for producing electrical insulating oil is described in which the sulfur content in the final product is reduced to 0.1 to Q, 3 wt% by clay treatment.

According to the examples in the above specification, the total acid value after the oxidation stability test (test method specified in JIs-C2101) of electrical insulating oil manufactured by this manufacturing method is 0.35 to KOH in the most preferred example. /,9, which satisfies the electrical insulating oil (Jl5-C-2320-1978) standard of 0.60 KOH/,9 or less, but has even better oxidation stability, such as total acid value of 0. .301n9KOH/,
! It is unsatisfactory for manufacturing products that require a score of 9 or less.

As a result of intensive studies to solve this problem, the present inventors first hydrorefined distillate oil containing about 2 to about 3 wt% sulfur obtained from paraffin-base crude oil or mixed-base crude oil to a moderate level. The hydrotreated oil is then subjected to solvent refining and desulfurization to an appropriate degree, followed by solvent membrane waxing treatment, followed by clay treatment to reduce the sulfur content of the final product to 0.1 to 0.
By adjusting to 4wt%, the JIS standard value (0,
It was discovered that it was possible to produce an insulating oil that had a width of 60 KOH/It and had even better oxidation stability than the insulating oil obtained by the conventional production method (Japanese Patent Publication No. 53-47242), and the present invention was completed. reached.

The method of the present invention uses a distillate having a boiling point (converted to normal pressure) in the temperature range of 250 to 400°C obtained by atmospheric distillation of paraffin base crude oil or mixed base crude oil or vacuum distillation of residual oil from atmospheric distillation. One of its characteristics is that it is first hydrorefined and then solvent refined.

If hydrorefining is performed before solvent refining, even the extract removed in solvent refining will be included in the hydrorefining, which is somewhat economically disadvantageous.

However, on the other hand, this method can leave high concentrations of sulfur compounds that act as natural antioxidants, including hydrogenation intermediate products of sulfur compounds, so it is possible to produce electrical insulating oils with even better oxidation stability. It can be manufactured.

To explain in more detail, the sulfur compounds in the above distillation are mercaptan (R8H), sulfide (R8 Paper Q, etc.)
, disulfide (R8SR'), thiophene (()] ρC+ ) (R.

(R' refers to an alkyl group, a phenyl group, a naphthalene group, etc.), but most of the mercaptans and disulfides are removed by hydrorefining, and thiophene-type sulfur compounds such as benzothiophene are partially hydrogenated. to produce sulfide.

That is, by first hydrogenating, it is possible to increase the content of sulfide-type sulfur compounds among the sulfur compounds in the final product.

On the other hand, if solvent refining is performed first, thiophene-type sulfur compounds such as benzothiophene are selectively extracted and removed, so even if hydrogen refining is carried out afterwards, the sulfide content will be low. 1 It exhibits favorable oxidative stability. There isn't.

The content of the present invention will be specifically explained below.

In the present invention, paraffin base crude oil is a crude oil containing a large amount of paraffinic hydrocarbons, such as Pennsylvania crude oil and Minas crude oil, and mixed base crude oil is a crude oil containing a large amount of paraffinic hydrocarbons, such as Pennsylvania crude oil, Minas crude oil, etc. It is intermediate between paraffin-based crude oil and naphthenic-based crude oil, which are often found in crude oils.

In the present invention, crude oils such as kraate crude oil, Basra crude oil, Khafji crude oil, and Arabian light crude oil are preferably used.

The crude oil is produced by atmospheric distillation or vacuum distillation of residual oil from atmospheric distillation,
Distillate oil having a boiling point in the range of 250 to 400°C (converted to normal pressure) is obtained and used as a starting material.

The distillate oil has a viscosity suitable for producing electrical insulating oil as specified by JIS C-2320 (Type 1), contains a sulfur content of about 2 to about 3 wt%, and has a sulfur content of about 2 to about 3 wt%. Desulfurization is carried out in stages and the sulfur content is finally adjusted to the desired level.

The sulfur adjustment method will be explained next.

Distillate oil obtained by atmospheric distillation of the above crude oil or vacuum distillation of the residual oil from atmospheric distillation and having a boiling point (converted to normal pressure) in the temperature range of 250 to 400°C is subjected to hydrorefining treatment, and 50 to 80 wt% of sulfur contained in extracted oil is removed.

In the hydrorefining process, for example, one or more of nickel, molybdenum, cobalt, tungsten, etc. are converted into alumina,
Using a catalyst supported on a carrier made of silica etc., at 310℃
Reaction temperature of ~370°C, reaction pressure of 25-1001 y/i, 0.5-3. Ohr-” liquid hourly space velocity, 100-3
00011 H2/13 The process can be performed under conditions of a hydrogen gas supply rate of 0 il.

At temperatures higher than 370°C, natural sulfur compounds of the type that are effective as antioxidants are selectively removed, that is, the desulfide rate increases, making it difficult to obtain electrical insulating oils with excellent oxidation stability. Have difficulty.

In addition, under desulfurization conditions of 310°C or lower, the desired sulfur content cannot be achieved unless the solvent extraction and purification conditions in the next step are made harsher. This method is not economical because the specifications for gas absorption, which is an important property for oils, cannot be met, and at the same time, the yield of raffinate becomes low and the amount of solvent used increases.

The hydrogenated oil is then treated with an extraction solvent that has preferential dissolving power for aromatic compounds to remove 40-80 wt% of the sulfur present in the hydrogenated oil.

The extraction solvent used here that has preferential dissolving power for aromatic compounds is commonly used, and specifically, furfural, phenol, N-methyl-2-pyrrolidone, etc. are used. .

In the present invention, furfural is particularly suitable, and when furfural is used, the extraction temperature is usually 40 to 100°.
C1 is preferably 40 to 70°C, and the ratio of furfural to mineral oil is 0.5 to 3.0, preferably 1.0 to
Used in the range of 2.5.

When the desulfurization rate is less than 40%, the electrical properties of the resulting electrical insulating oil are unfavorable, and when the desulfurization rate exceeds 80%, the aromatic content decreases, resulting in poor gas absorption.

As mentioned above, the sulfur content can be adjusted to 0.1 to 4 wt% by performing hydrorefining and then solvent extraction refining. Can perform waxing.

Solvent film brazing treatment involves appropriately adding a dewaxing solvent consisting of a mixture of aliphatic ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, etc. and aromatic hydrocarbons such as toluene, benzene, etc., and cooling to approximately -40 to -10°C. This can be done by removing the wax content.

The solvent membrane brazing treatment in the present invention may be performed at any stage, but it is particularly preferably performed after solvent purification.

Subsequently, the solvent-refined oil is treated with white clay, which involves adding 1 to 6 wt% of white clay to the oil to be treated.
This can be carried out by contact treatment at a temperature of about 100° C. for about 30 minutes to 1 hour.

The sulfur content in the insulating oil of the present invention is 0.1 to 0.4 wt%
However, the basis for this range limitation is explained by the diagram.

That is, the figure shows the total acid value measurement results after the oxidation stability test of the insulating oil obtained by the refining method of the present invention, that is, hydrorefining followed by solvent extraction refining, and the sulfur content is Q, 1
This includes those adjusted to less than wt%.

The figure shows that when the sulfur content is less than 0.1 wt%, the oxidation stability decreases significantly;
In the wt% range, the total acid value is 0.31r19K
OH/g or less is approximately 0.21 to 0.28 KOH/&,
QJO~0.
Since a difference of about 15 to KOH/g is observed, it can be understood that the lower limit of the sulfur content is preferably 0.1 wt%.

Furthermore, the reason for setting the upper limit of sulfur content to 0.4 wt% is from the perspective of copper plate corrosion rather than oxidation stability.
In order to prevent the blackening phenomenon of the copper material used in the transformer filled with insulating oil, it is important to keep the content to 0°4 wt% or less in order to produce a good electrical insulating oil.

As described above, the electrical insulating oil produced by the method of the present invention exhibits excellent oxidation stability and is also excellent in copper plate corrosion resistance, and can be said to have extremely high industrial value.

Examples will be described below, but the present invention is not limited thereto.

Example 1 Distillate oil obtained by distilling craate crude oil (mixed base type) at atmospheric pressure and then distilling the residual oil under reduced pressure (boiling point 250 in terms of atmospheric pressure)
~400°C, sulfur content 2.4 wt%) was collected.

Next, this distillate was converted into C60-Mo with alumina as a carrier.
O3 catalyst (CoO: 3.2 wt%.

M2O3: 15.1 wt%) was used to obtain hydrogenated oil (
desulfurization rate 67wt%).

Furthermore, this hydrogenated oil was mixed with a solvent ratio (furfural/oil) of 1.5.
, Furfural extraction was carried out at an extraction temperature of 50 to 60°C to obtain raffinate (sulfur content QJ6wt%), using toluene/methyl ethyl ketone as a solvent, solvent ratio (solvent/oil) 2.0, cooling temperature = 35°C.
After dewaxing, the amount of white clay is 3 wt% to oil, and the temperature is 60.
Treated with white clay at ℃ for 30 minutes, and treated with electrical insulating oil (sulfur content 0.
18 wt%, pour point -30°C).

When this oil was subjected to a JIS method oxidation stability test, the total acid value was 0.21 to KOH/, and the 91 sludge was 0.07%, which was good.

Examples 2-5. Comparative Examples 1 to 5 The distillate of Example 1 was treated in the order of hydrorefining and solvent refining (furfural extraction) under various refining treatment conditions, and then decomposed under the same conditions as Example 1. Examples 2 to 5 in Table 1 show examples in which wax and clay treatments were performed.

In addition, the distillate of Example 1 was treated with various refining conditions in the order of solvent refining (furfural extraction) and hydrorefining, and dewaxing and clay treatment under the same conditions as in Example 1. Examples in which this was carried out are shown in Comparative Examples 1 to 5 in Table 1.

Comparing these Examples and Comparative Examples, it was found that the oxidation stability was better by processing in the order of hydrogen refining and solvent refining than in the order of solvent refining and hydrogen refining (in particular, the total acid It can be seen that an electrical insulating oil with a small increase in value can be obtained.

Moreover, from Examples 1 to 3, it can be seen that the oxidation stability of electrical insulating oil is almost determined by the hydrorefining treatment, which is the first refining step.

Examples 6 and 7 Distillate oil obtained by distilling Baslarite crude oil and Khafji crude oil at atmospheric pressure and distilling the residual oil under reduced pressure (boiling point 250-400°C in terms of normal pressure, sulfur content Baslarite:
2.2 wt%, Kafuji: 2.5 wt%), the oxidation stability of electrical insulating oils obtained by processing under the same conditions as in Example 2 is shown in Examples 6 and 7 in Table 2, respectively.

It can be seen that electrical insulating oil with good oxidation stability can also be produced from these crude oils.

Comparative Example 6 Distillate oil obtained by distilling a naphthenic crude oil at normal pressure and then distilling the residual oil under reduced pressure (boiling point 250-400°C in terms of normal pressure,
Sulfur content: 0.62 wt%) was collected.

Next, this distillate was mixed with Co0-MoO using alumina as a carrier.
Hydrogenated oil (sulfur content: 0.28 wt%) was obtained by hydrorefining at 320°C and hydrogen pressure of 35 kg/i using the 3 catalyst.

Further, furfural was extracted at a solvent ratio of 1.0 and an extraction temperature of 50 to 60°C, and the resulting raffinate was treated with clay to obtain electrical insulating oil with a sulfur content of Q and 16 wt%.

When we conducted a JIS oxidation stability test on this oil, we found that
The total acid value was 0.84 to KOH/&, and the slatch was 0.29%.

As described above, although hydrorefining, solvent refining, and clay treatment were performed on naphthenic crude oil within the range of the treatment conditions of the present invention, a product with good oxidation stability could not be obtained.

Comparative Example 7 The distillate of Example 1 was heated to 370% using the catalyst shown in Example 1.
°C, hydrogen pressure 35kg/crtr, LH8V 1.0
Hydrogenation treatment was carried out under the conditions of hr-1.

Next, hydrogenated oil was mixed with furfural as a solvent, and the solvent ratio was 1.0.
The resulting raffinate was subjected to dewaxing and clay treatment under the same conditions as in Example 1 to obtain electrical insulating oil with a sulfur content of 0.14 wt%.

The JIS oxidation stability test results for this oil are shown in Table 2, with a total acid value of 0.741119KOH/! 7,
It did not show favorable oxidative stability.

[Brief explanation of the drawing]

The figure shows the sulfur content in insulating oil and the JIS method (JIS-C-21
01) Shows the relationship with the total acid value after the oxidation stability test.

Claims (1)

[Claims] 1. A paraffin base crude oil or a mixed base crude oil is distilled under atmospheric pressure, or the residual oil of atmospheric distillation is distilled under reduced pressure, and the boiling point (converted to normal pressure) is within the temperature range of 250 to 400°C, and the sulfur content is 2 to 2. Distillate oil containing 3% by weight was heated at 310°C to 3% by weight.
50-80 by hydrorefining at a temperature of 70℃
wt% desulfurization to reduce sulfur content from 0.5 to 1. The hydrogenated oil is purified using a furfural solvent to desulfurize the hydrogenated oil to 40 to 80 wt%, and the resulting raffinate is further subjected to solvent membrane waxing and then clay treatment to eliminate sulfur in the final product. A method for producing electrical insulating oil with excellent oxidation stability, characterized in that the content of the oil is 0.1 to 0.4 wt%.