RU2123028C1 - Method of preparing electroinsulating oil - Google Patents

Abstract

FIELD: petroleum refining. SUBSTANCE: petroleum stock is subjected to hydrorefining, catalytic deparaffination and hydrogenation, catalytic deparaffination and hydrogenation being carried out in two reactors consecutively charged with unique system of circulation of water-containing gas which contains hydrogen content within 75-95 vol % at system inlet, and base oil includes 0.2-0.5% antioxidative additive. In order to stabilize quality of transformer oil, base oil is recycled to catalytic deparaffination and hydrogenation stage. Petroleum stock includes petroleum fractions or rafinates of selective refining of sulfur petroleums which evaporate at temperatures from 275-430 C and contain sulfur form 0.1 to 1.0 wt % and aromatic hydrocarbons from 15 to 30 wt %. The method makes it possible to increase yield of quality product and widen raw material basis for preparation thereof. EFFECT: more efficient preparation method. 3 cl, 6 ex, 1 tbl

Description

 The invention relates to the field of oil refining, and in particular to a method for producing insulating oil used in various types of oil-filled equipment: transformers, electrical inputs, oil-filled cables, etc.

 Insulating oil used in various electrical equipment should have a low pour point, low dielectric loss, high thermal oxidative stability and good gas resistance.

 The behavior of oil in electrical equipment depends on the chemical composition of the oil - the less aromatic hydrocarbons in the oil, the higher its oxidative stability. It is known that gas resistance of oil, i.e. the oil’s resistance to the effects of ionized gas molecules also strongly depends on the content of aromatic hydrocarbons in the oil, the more aromatic hydrocarbons in the oil, the better its gas resistance.

It is known to obtain insulating oil with a pour point below minus 40 ^o C from a low-paraffin vacuum gas oil of Kuwaiti oil in 3 steps. In the first stage, at a pressure of 13.8 MPa and a temperature of 375 ^o C, a feed rate of 1.0 h ^-1 on the alumina-cobalt-molybdenum catalyst, the feedstock is hydrotreated. At the 2nd stage, the hydrotreated product is sent for catalytic dewaxing, which is carried out at a pressure of 3.5 MPa, a temperature of 320 ^o C on a catalyst containing 0.5% platinum, 38.4% SiO ₂ and aluminum oxide. At the 3rd stage, the dewaxed product is subjected to distillation and contact cleaning (GB 1449515, C 5 E, 73).

 The disadvantage of this method lies in the need for contact cleaning and disposal of waste land, as well as in carrying out stage I hydroprocessing at high pressure.

It is also known to obtain transformer oil from a paraffinic light vacuum gas oil of paraffinic oil. Raw materials having a pour point of + 4.4 ^° C are hydrotreated at a pressure of 10.5 MPa, a temperature of 387 ^° C on a catalyst containing 6% Ni and 19% W on alumina. Hydrotreated raw materials are sent for catalytic dewaxing, which is carried out at a pressure of 10.5 MPa, a temperature of 282 ^o C on a catalyst containing 0.5% Ti and 1% Pd on a carrier - decationized mordenite. After post-treatment with earth, an insulating oil is obtained with a pour point of -43 ^° C and a cloud point of -40 ^° C (US 4057489, 108-89, 77).

 The disadvantage of this method is the high pour point and cloudiness of the obtained insulating oil.

The closest in technical essence to the claimed is a method for producing low-viscosity bases of hydraulic oils by hydrotreating a straight-run oil fraction, boiling in the range of 250-420 ^o C, subsequent catalytic dewaxing, hydrogenation of the dewaxed fraction and the selection of the target fraction, in which catalytic dewaxing and hydrogenation are carried out in cycles of duration 500-1000 hours, between cycles of both processes the catalysts are treated with a hydrogen-containing gas at a pressure of 3.5-7.0 MPa, temperature of 425-500 ^o C for 12-36 hours and the hydrogenation is carried out until dewaxed fraction of aromatic hydrocarbons in oil of 4-12 wt. % (RU 2064002, C 10 G 65 / 12.1996).

 When using this method to obtain electrical insulating oil, a low oil yield is noted, because to obtain electrical insulating oil requires raw materials of a heavier fractional composition. In addition, this method processes only low-sulfur oils.

 The technical task of this invention is to increase the yield of insulating oil, expanding the raw material base for its production and the possibility of obtaining oil with good thermal oxidative stability and low dielectric loss.

The problem is solved in that in the method for producing electrical insulating oil by hydrotreating petroleum feedstock, subsequent catalytic dewaxing, hydrogenation of the dewaxed fraction and isolating the base oil, according to the invention, the petroleum fraction boiling in the range 275-430 ^o C, with the content sulfur from 0.1 to 1.0 wt.% and aromatic hydrocarbons from 15 to 30 vol.%, and the catalytic dewaxing and hydrogenation of the dewaxed fraction are carried out in 2 successively loaded catalysts in reactors with a unified hydrogen-containing gas circulation system with a hydrogen content in the range of 75-95 vol.% at the outlet to the system and into the base oil are injected with 0.2-0.5 wt.% antioxidant additives. The oil fraction used as a raw material may be a straight-run oil fraction or a selective refined raffinate.

 The most important role in the technology for producing high-quality transformer oil is played by the processes of catalytic dewaxing and hydrogenation, which provide a low pour point of the oil and its electrical insulating properties. Therefore, when implementing the proposed method, it is possible to recycle to the stage of catalytic dewaxing and hydrogenation of 25-50% of the base oil per hydrotreated feedstock. This will allow to obtain high-quality transformer oil that meets the requirements for thermal oxidative stability and pour point while reducing the activity of catalytic dewaxing and hydrogenation catalysts.

The proposed method is carried out at a pressure of 3.8-4.8 MPa in all three stages:
At the stage of hydrotreating, a catalyst is used containing, wt.%:
Molybdenum Trioxide - 10 - 15
Nickel oxide - 2 - 4
Phosphorus Pentoxide - 2 - 7
Rare earth oxides - 0.1 - 10
Zirconium oxide - 0.1 - 10
Alumina - Up to 100
The hydrotreatment process is carried out at a temperature of 330-400 ^o C and a volumetric feed rate of 0.65-1.2 h ^-1 .

In the first along the hydrotreated feed the reactor is loaded dewaxing catalyst containing, wt.%:
Molybdenum oxide - 6 - 15
Boron oxide - 2 - 15
Alumina - 10 - 40
High Silica Zeolite - Up to 100
At the stage of hydrogenation, a catalyst is loaded containing, wt.%:
Platinum - 0.48 - 0.54
Aluminosilicate - 17 - 30
Alumina - Up to 100
The stage of catalytic dewaxing and hydrogenation is carried out at a feed rate of 0.6-1.2 h ^-1 , the circulation of a hydrogen-containing gas 1500-2000 nm ³ / m ³ raw materials.

The pour point of the oil and the content of aromatic hydrocarbons in the oil are controlled by the temperature in the reaction zone. In the first reactor along the raw material, the temperature in the reaction zone varies from 330 to 390 ^o C, in the second hydrogenation reactor the temperature varies from 220 to 270 ^o C. The hydrogenated dewaxing is subjected to rectification and 0.2-0.5 wt. .% antioxidant additives.

The expansion of the raw material base in the present method is carried out through the use of both straight-run crude oil fractions of low-sulfur oils and selective raffinates of ordinary sulphurous oils, moreover, to obtain oil from sulphurous oils, a shallow selective raffinate is used, obtained in 90-95% yield distillate. In this case, raw materials containing a smaller amount of tri- and tetracyclic aromatic hydrocarbons are supplied to the hydroprocesses for processing, which makes it possible to obtain electrical insulating oil from ordinary sulfur raw materials. In the case of the use of an oil fraction or selective raffinate boiling within 275-430 ^o C, significantly increases the yield of electrical insulating oil compared to the prototype by increasing the fractional composition of the feedstock. In addition, during the hydrotreatment process, easy hydrocracking of the feedstock is carried out, which leads to the expansion of the fractional composition of the hydrotreated product, i.e. to the formation of fractions that boil away before the boiling of the feedstock. During rectification of the hydrogenated dewaxing fractions boiling from 265 ^o C to the beginning of the boiling of the feedstock are involved in the oil, which also leads to an increase in the yield of oil.

 Carrying out 2 processes - catalytic dewaxing and hydrogenation at a pressure of 3.8-4.8 MPa in a system with a single circulation of hydrogen-containing gas in 2 successively loaded reactors allows to reduce the cost of production, since this uses one system of pipelines, pumps compressors.

 The use of a hydrogen-containing gas with a high hydrogen content at the entrance to the system in the range of 75-95 vol. % is necessary to maintain the partial pressure of hydrogen at the hydrogenation stage, since hydrocarbon gases (methane, ethane, propane, butanes) are formed during catalytic dewaxing, which reduce the hydrogen content in the hydrogen-containing gas and, therefore, reduce the partial pressure of hydrogen at the hydrogenation stage.

Example 1. Straight-run oil fraction of a mixture of Volgograd and Shaim oils, boiling in the range 275-400 ^o C, with the following characteristics:
Boiling point - 275 ^o C
Boiling point - 400 ^o C
Viscosity at 50 ^o C - 7.9 mm ² / s
Pour point - +3 ^o C
Sulfur content - 0.35 wt.%
The content of aromatic hydrocarbons is 18.5 vol.%
subjected to hydrotreating at a pressure of 3.8 MPa, a temperature of 380 ^o C, a feed rate of 0.7 h ^-1 on a catalyst containing molybdenum trioxide 10%, nickel oxide 2%, phosphorus pentoxide 7%, rare earth oxides 5%, zirconium oxide 5%, alumina up to 100%.

Hydrotreated fraction with the following characteristics:
Boiling point - 240 ^o C
Boiling point - 383 ^o C
Viscosity at 50 ^o C - 7.6 mm ² / s
Sulfur content - 0.01 wt.%
Pour point - +1 ^o C
sent to catalytic dewaxing and hydrogenation, which is carried out at a pressure of 4.5 MPa in two successively loaded reactors at a volumetric feed rate of 0.68 h ^-1 . The catalytic dewaxing catalyst of the following composition is loaded into the first reactor along the feedstock, wt.%:
Molybdenum oxide - 7.5
Boron oxide - 5.9
Alumina - 29.5
High Silica Zeolite - Up to 100
in a second reactor for the hydrogenation step, a catalyst is loaded comprising:
Platinum - 0.5%
Aluminosilicate - 20.0%
Alumina - Up to 100%
The temperature in the catalytic dewaxing reactor is 330 ^o C, at the hydrogenation stage 250 ^o C. The hydrogen content in the circulating hydrogen-containing gas (HCV) is 90 vol.% At the entrance to the catalytic dewaxing reactor. The obtained hydrated dewaxin is subjected to rectification with the separation of a fraction boiling above 260 ^o C, which is a base electrical insulating oil, into which 0.2 wt.% Agidol is introduced.

Determination of thermal oxidative stability of the oil is carried out according to the methodology of the International Electrotechnical Commission. The criterion for the stability of the oil is taken to be the time — in hours — during which the amount of low molecular weight acids equivalent to 0.28 mg of caustic potassium per 1 g is released from the oil at a temperature of 120 ^o C in the presence of a copper wire while blowing oxygen at a speed of 1 l / g of oil oils.

Insulating oil has the following characteristics:
Viscosity at 50 ^o C - 8.1 mm ² / s
Viscosity at -30 ^o C - 1273 mm ² / s
Pour point - minus 46 ^o C
Flash point - 136 ^o C
Sulfur Content - No
Contents of solids - Lack
Color, CNT units - 0.5
Dielectric loss tangent at 90 ^o C - 0.3%
Copper Plate Corrosion - Withstand
The induction period of oxidation according to the method of IEC - 120 h
The yield of oil on the raw materials of the hydrotreatment stage is 42.8 wt.%
The resulting oil has good thermal oxidative stability and can be used in high voltage power transformers.

Example 2. Straight-run oil fraction of a mixture of Volgograd and Shaim oils, boiling in the range 275-385 ^o C, with the following characteristics:
Boiling point - 275 ^o C
Boiling point - 385 ^o C
Viscosity at 50 ^o C - 5.9 mm ² / s
Pour point - +2 ^o C
Sulfur content - 0.10 wt.%
The content of aromatic hydrocarbons is 15.0 vol.%
subjected to hydrotreatment at a pressure of 36 MPa, a temperature of 370 ^o C, a feed rate of 0.65 h ^-1 on the catalyst described in example 1.

Hydrotreated fraction with the following characteristics:
Boiling point - 240 ^o C
The temperature of the end of boiling - 378 ^o C
Viscosity at 50 ^o C - 5.7 mm ² / s
Pour point - +1 ^o C
Sulfur content - 0.005 wt.%
sent for catalytic dewaxing and hydrogenation, which is carried out in 2 successive reactors, on the catalysts described in example 1.

The process of catalytic dewaxing and hydrogenation is carried out at a pressure of 3.8 MPa, a temperature of 325 ^o C in the 1st reactor along the feedstock and at a temperature of 245 ^o C in the hydrogenation reactor at a feed rate of 0.6 h ^-1 . The hydrogen content in the hydrogen-containing gas at the system inlet was 95 vol.%
Deparaffinizate is subjected to rectification with the release of base oil (see table), which is introduced 0.3 wt.% Agidol. The yield of insulating oil is 41.7 wt.%. The insulating oil obtained by this method has good thermal oxidative stability and low dielectric loss.

Example 3. Straight-run oil fraction of a mixture of oils, boiling in the range of 300-430 ^o C, with the following characteristics:
Viscosity at 50 ^o C - 9.2 mm ² / s
Pour point - +6 ^o C
Sulfur content - 1.0 wt.%
The content of aromatic hydrocarbons is 30 vol.%
subjected to hydrotreating at a pressure of 4.0 MPa, a temperature of 400 ^o C, a feed rate of 1.2 h ^-1 on a catalyst containing, wt.%:
Molybdenum Trioxide - 10
Nickel Oxide - 4
Phosphorus Pentoxide - 5
Rare Earth Oxides - 8
Zirconium oxide - 7
Alumina - Up to 100
Hydrotreated fraction with the following characteristics:
Boiling point - 255 ^o C
Boiling point - 412 ^o C
Viscosity at 50 ^o C - 7.9 mm ² / s
Pour point - +5 ^o C
Sulfur content - 0.02 wt.%
subjected to catalytic dewaxing and hydrogenation in 2 sequentially charged reactors on the catalysts described in example 1, at a pressure of 4.8 MPa, a temperature in the catalytic dewaxing reactor of 360 ^o C, in a hydrogenation reactor of 240 ^o C. The feed rate is 1.1 h ^-1 . The hydrogen content in the WASH at the system inlet was 75%.

 The characteristics of the electrical insulating oil isolated by distillation of dewaxin and stabilized with 0.5% agidol are shown in the table. The output of electrical insulating oil is 45.2 wt. % The resulting oil has an induction period of oxidation (according to the IEC method) of only 80 hours

Example 4. To the hydrotreated fraction with the characteristics described in example 3, 25% of the base oil (based on the hydrotreated fraction) obtained in example 3 is recycled. As a result, a mixture of the hydrotreated fraction and base oil with the following characteristics is sent to the catalytic dewaxing and hydrogenation step :
Viscosity at 50 ^o C - 8.10 mm ² / s
Pour point - minus 15 ^o C
Boiling point - 261 ^o C
Boiling point - 412 ^o C
Sulfur content - 0.009%,
which is subjected to hydroprocessing on the catalysts described in example 1 under the conditions of example 3.

As a result of hydroprocessing, an insulating oil was obtained after stabilization with 0.5% agidol, which has the following characteristics (see table):
Viscosity at 50 ^o C - 8.76 mm ² / s
Viscosity at minus 30 ^o C - 1062 mm ² / s
Pour point - minus 49 ^o C
Acid number - 0.008 mg KOH / g
Refractive index, n $\genfrac{}{}{0ex}{}{\text{20}}{\text{D}}$ - 1.4783
The induction period of oil oxidation - 125 hours
The yield of transformer oil is 42% in the feed of the hydrotreatment stage.

 Example 5. In the hydrotreated fraction of example 3 recycle 50% of the base oil (calculated on hydrotreated raw materials) obtained in example 3.

A mixture of hydrotreated raw materials with a base oil with the following characteristics is sent to the stage of catalytic dewaxing and hydrogenation:
Viscosity at 50 ^o C - 8.35 mm ² / s
Pour point - minus 20 ^o C
Boiling point - 269 ^o C
Boiling point - 420 ^o C
Sulfur content - 0.006%
The stages of catalytic dewaxing and hydrogenation are carried out on the catalysts described in example 1 under the conditions of example 3. The hydrogenated dewaxing is subjected to rectification and stabilization of 0.5% agidol. The base oil obtained in example 5 has the following characteristics:
Viscosity at 50 ^o C - 8.95 mm ² / s
Viscosity at minus 30 ^o C - 1120 mm ² / s
Acid number - 0.004 mg KOH / g
Pour point - minus 55 ^o C
Refractive index, n $\genfrac{}{}{0ex}{}{\text{20}}{\text{D}}$ - 1.4788
The induction period of oil oxidation - 156 h
The yield of transformer oil is 43% in the feed of the hydrotreatment stage.

Example 6. The raffinate of the selective purification of a mixture of oils, boiling in the range 275-400 ^o C, with the following characteristics:
Boiling point - 275 ^o C
Boiling point - 400 ^o C
Viscosity at 50 ^o C - 7.2 mm ² / s
Pour point - + 10 ^o C
Sulfur content - 0.13 wt.%
The content of aromatic hydrocarbons is 18 vol.%
subjected to hydrotreating at a pressure of 3.8 MPa, a feed rate of 0.9 h ^-1 , a temperature of 330 ^o C on a catalyst containing wt.%:
Molybdenum Trioxide - 12
Nickel Oxide - 4.5
Phosphorus Pentoxide - 6.1
Zirconia - 8
Rare earth oxides - 6.5
Alumina - Up to 100
Hydrotreated raffinate with the following characteristics:
Boiling point - 240 ^o C
Boiling point - 389 ^o C
Viscosity at 50 ^o C - 6.0 mm ² / s
Pour point - +7 ^o C
Sulfur content - 0.007 wt.%
sent for catalytic dewaxing and hydrogenation, which are carried out in 2 successively loaded reactors. In the first along the raw material reactor loaded catalyst containing, wt.%:
Molybdenum Oxide - 8.5
Boron Oxide - 10
Alumina - 25
High Silica Zeolite - Up to 100
The hydrogenation step is carried out on the catalyst described in Example 1.

The process is carried out at a pressure of 4.0 MPa, a feed rate of 0.87 s ^-1 , a temperature of 350 ^o C in a catalytic dewaxing reactor and a temperature of 230 ^o C in a hydrogenation reactor. The hydrogen content in the WASH is 85 vol.% At the entrance to the system. Deparaffinizate is subjected to rectification and stabilization of 0.25 wt.% Agidol.

The characteristic of electrical insulating oil is given in the table. The insulating oil obtained in the described example has good thermal oxidative stability and low dielectric loss. The induction period of oil oxidation according to the IEC method is 129 hours. Oil yield 43.4 wt.%
Thus, the proposed method for producing electrical insulating oil allows you to:
expand the raw material base for oil production, i.e. use both low-sulfur and ordinary sulfur oils to obtain oil;
significantly increase the yield of electrical insulating oil: the average oil yield increased by 17.2% compared with the prototype;
receive electrical insulating oils with high thermal oxidative stability and low dielectric losses;
Electrical insulating oils obtained by the proposed method can be used in any type of electrical equipment.

Sources of information taken into account during the examination
1. British patent N 1449515, CL C 5 E publ. 1973

 2. US patent N 4057489, CL. 208-89 publ. 1977

3. Patent of the Russian Federation N 2064002, M. cl. ⁶ C 10 G 65/12, publ. 07/20/96, Bull. N 20. (prototype) 0

Claims (3)

1. A method of producing electrical insulating oil by hydrotreating petroleum feedstock, subsequent catalytic dewaxing, hydrogenation of the dewaxed fraction and isolating the base oil, characterized in that the petroleum fraction is used as a petroleum feedstock, boiling in the range 275-430 ^o C, with a sulfur content of from 0, 10 to 1.0 wt.% And aromatic hydrocarbons from 15 to 30 vol.%, And the catalytic dewaxing and hydrogenation of the dewaxed fraction are carried out in two reactors sequentially loaded with catalysts with a single a hydrogen-containing gas circulation system with a hydrogen content in the range of 75 - 95 vol.% at the entrance to the system and into the base oil is injected with 0.2 - 0.5 wt.% antioxidant additives.  2. The method according to claim 1, characterized in that 25-50% of the base oil per hydrotreated feed is recycled at the stage of catalytic dewaxing and hydrogenation.  3. The method according to PP.1 and 2, characterized in that the raw materials use straight-run oil fraction or selective raffinate.

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