RU2064002C1 - Method for production of base of electric insulating oil - Google Patents

Abstract

FIELD: petroleum chemistry. SUBSTANCE: straight-run petroleum fraction of 250-420 C is subjected to hydrofining and, then, to dewaxing, and these processes are conducted by cycles for 500-1000 h with catalysts being treated between cycles with hydrogen-containing gas at pressure of 3.5-7.0 MPa, temperature of 425-500 C for 12-36 h. Hydrodewaxed fraction is treated to obtain the content of aromatic hydrocarbons in oil up to 4-12 mas.%. EFFECT: higher efficiency.

Description

 The invention relates to the field of oil refining, and in particular to a method for producing a base of electrical insulating oil used in a composition with an antioxidant in transformers and other types of oil-filled equipment. The transformer oil used for filling transformers should have a low pour point, low dielectric loss and high thermo-oxidative stability. These qualities of the oil provides the chemical composition of the oil. At present, the technology for producing transformer oil is of great importance, which would ensure the production of high-quality transformer oil from ordinary paraffinic sulfurous raw materials.

It is known to obtain insulating oil with a pour point below minus 40 ^o C from 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 ^{° C.} , a feed rate of 1.0 hour _-1, the feedstock is hydrotreated on an alumina-cobalt-molybdenum catalyst. 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 With a catalyst containing 0.5% platinum, 38.4% Si0 ₂ and aluminum oxide. At the 3rd stage, the dewaxed product is subjected to distillation and contact cleaning [I]
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 feed is sent for catalytic dewaxing, which is carried out at a pressure of 10.5 MPa, a temperature of 282 ^o With a catalyst containing 0.5% Ti and 1% Pd on a carrier of decationized mordenite. After post-treatment with earth, an insulating oil with a pour point of minus 43 ^o C is obtained [2] The closest in technical essence to the claimed method is a method for producing a base of hydraulic oil by hydroprocessing in 3 stages of a straight-run oil fraction boiling in the range of 215-330 ^o C.

At the 1st stage, the feedstock is hydrotreated at a pressure of 4 MPa and a temperature of 360 ^{° C.} using a conventional hydrotreating catalyst.

At the 2nd stage, hydrotreated raw materials are dewaxed at a pressure of 3.5 MPa, a temperature of 280 ^o With a catalyst containing a hydrogenating metal and a high silica zeolite.

At the 3rd stage, the dewaxin is hydrogenated at a pressure of 3.5 MPa, a temperature of 260 ^{° C.} on a platinum-containing catalyst [3]. Upon receipt of the insulating oil by this method, a very small yield of insulating oil was noted, since in order to obtain a base of insulating oil with a pour point 135 ^o With the necessary raw materials of a heavier fractional composition.

 The technical task of this invention is to increase the yield of the base of insulating oil used in the composition of transformer oil and giving it high thermal oxidative stability and low dielectric loss.

This problem is solved in that in a method for producing a base of electrical insulating oil, including hydrotreating a straight-run oil fraction, catalytic dewaxing and hydrogenation of a hydrotreated oil fraction with subsequent isolation of the target oil fraction, according to the invention, the catalytic fraction is boiled away within 250-420 ^{° C.} dewaxing and hydrogenation are carried out in cycles of 500-1000 hours, and between cycles the catalysts of both processes are treated with hydrogen-containing gas at a temperature round of 425-500 ^o C and a pressure of 3.5-7.0 MPa for 12-36 hours and the hydrogenation is carried out fraction dewaxed to a residual content of aromatic hydrocarbons of 4-12%
The use of the straight-run fraction boiling in the range of 250-420 ^o C in the inventive method will significantly increase the yield of the base of insulating oil. But when using a heavier fractional composition of the feed, the catalytic dewaxing catalyst loses activity faster, since aromatic hydrocarbons are adsorbed on the catalyst surface and close access to the catalyst pores with normal paraffinic hydrocarbons, with an average of 18-20 carbon atoms in the paraffin chain, and the catalyst gradually loses activity and does not provide the basics of electrical insulating oil with a pour point of not higher than minus 45 ^o C. To restore the activity It is proposed that the process of obtaining the base oil be carried out in cycles of 500-1000 hours, and between cycles the catalysts for catalytic dewaxing and hydrogenation are treated with a hydrogen-containing gas. When processing the catalyst for catalytic dewaxing with a hydrogen-containing gas at a temperature of 425-400 ^o C, aromatics are hydrogenated. The naphthenic hydrocarbons formed are desorbed from the surface of the catalyst and open the pores for normal paraffin hydrocarbons to enter the active pores of the catalyst, and the cracking reaction of the latter is accelerated.

When processing a hydrogenation catalyst containing platinum with a hydrogen-containing gas at a temperature of 425-500 ^o C, partially deactivated sulfur platinum is reduced to an active metal, which will allow hydrogenation of the dewaxed fraction to a residual aromatic hydrocarbon content in the range of 4-12% with such a content of aromatic hydrocarbons ( determined by the sulfonation method) the base of the oil perceives the antioxidant additive and the marketable oil obtained by the specified method obom will have a high thermo-oxidative stability and low dielectric losses. The induction period of oxidation will be 120-170 hours.

Thus, only a combination of using heavier fractional feedstock and carrying out catalytic dewaxing and hydrogenation stages in cycles allows us to obtain an insulating oil with a pour point of no higher than minus 45 ^o С and aromatic hydrocarbons in the range of 4-12%. Processing of the catalysts with hydrogen-containing gas restores the activity of the catalysts.

 The invention is illustrated by the following examples.

Example 1. Straight-run oil fraction of a mixture of Volgograd and Shaim oils, boiling in the range of 250-390 ^o With, with the following characteristics:
fractional composition, ^o С
boiling point 250
5% boils at a temperature of 265
boiling point 392
viscosity at 50 ^o C, mm ² / s 5.62
pour point, ^o С minus 1
sulfur content, 0.19
aromatic hydrocarbon content, vol. 18.0
subjected to hydrotreatment, which is carried out at a pressure of 4.2 MPa, a temperature of 375 ^o With a catalyst of the following composition, wt.

nickel oxide 7.1
molybdenum oxide 18.0
rare earth oxide 1.0
alumina up to 100.

Hydrotreated fraction having the following characteristics:
viscosity at 50 ^{° C.} 5.2 mm ² / s
pour point 2 ^o C
sulfur content 0.01%
aromatic hydrocarbon content 17% vol.

sent for catalytic dewaxing and subsequent hydrogenation, which is carried out at a pressure of 4.7 MPa, a temperature of 350-390 ^o With at the stage of catalytic dewaxing and at a temperature of 250-265 ^o With the same pressure at the stage of hydrogenation. For these stages, the following catalysts are used, wt.

for the stage of catalytic dewaxing
molybdenum oxide 8
boron oxide 6
alumina 30
high silica zeolite up to 100
for the hydrogenation step
platinum 0.5
aluminosilicate up to 100.

The cycle of work on obtaining a base oil with a pour point of not higher than minus 45 ^o C was 1000 hours, after which the activity of the catalysts decreased, oil became obtained with a pour point above minus 45 ^o C, which does not meet the requirements of technical specifications for insulating oil. To restore activity, the catalysts are treated with a hydrogen-containing gas at a pressure of 5.0 MPa, a temperature of 480 ^o C for 18 hours. After treatment with hydrogen-containing gas, the catalysts restored their initial activity. After catalytic dewaxing and hydrogenation, a dewaxed fraction is obtained with the following characteristics.

Fractional composition, ^o C:
start of boiling 80
end of boil 360
viscosity at 50 ^o C 3.46 mm ² / s
pour point below minus 70
aromatic hydrocarbon content 3.4%
A fraction with the specified characteristics is subjected to rectification with the allocation of the fraction boiling off at a temperature above 270 ^o C, which is the basis of electrical insulating oil.

The base of the oil has the following characteristics:
Viscosity at 50 ^{° C.} 6.7 mm ² / s
Pour point minus 47 ^o C
Flash point 136 ^o C
Aromatic hydrocarbon content 4%
Refractive Index 1.4720
Copper Plate Corrosion Resists
The output of the base insulating oil on raw materials 38% wt.

Example 2. Straight-run oil fraction of a mixture of Volgograd and Shaim oils, boiling in the range of 270-420 ^o With the following characteristics:
Fractional composition, ^o С
Start of boiling 270
The end of the boil 420
Viscosity at 50 ^{° C.} 8.2 mm ² / s
Pour point 6 ^o C
Sulfur content 0.31%
The aromatic hydrocarbon content of 22% vol.

subjected to hydrotreatment at a pressure of 4.5 MPa, a temperature of 375 ^o With a catalyst of the following composition, wt.

molybdenum oxide 10
nickel oxide 3.1
phosphorus oxide 4.2
rare earth oxide 1.5
zirconium oxide 2.5
alumina up to 100.

Hydrotreated fraction having the following characteristics:
Viscosity at 50 ^o C 7.95 mm ² / s
Pour point 7 ^o C
Sulfur content 0.012%
Aromatic hydrocarbon content 20%
sent for catalytic dewaxing and subsequent hydrogenation, which is carried out at a pressure of 4.8 MPa, a temperature of 360-390 ^o With at the stage of catalytic dewaxing and a temperature of 260-280 ^o With at the stage of hydrogenation. The processes are carried out on the catalysts, the composition of which is described in example 1. The cycle of operation of the catalysts in the mode of catalytic dewaxing and hydrogenation was 500 hours, after which the catalysts were treated with hydrogen-containing gas at a pressure of 3.5 MPa and a temperature of 500 ^o C for 36 hours.

The base of electrical insulating oil, isolated by distillation of the dewaxed fraction, has the following characteristics:
Viscosity at 50 ^° C 8.4 mm ² / s
Pour point minus 46 ^o C
Flash point 140 ^o C
Aromatic hydrocarbon content 12%
Refractive Index 1.4765
Copper Plate Corrosion Resists
The output of the basics of electrical insulating oil 41.7%
Example 3. Straight-run oil fraction boiling in the range of 265- 380 ^o C, with the following characteristics:
Fractional composition, ^o С
Start of boiling 265
5% boils at a temperature of 276
The end of the boil 380
Viscosity at 50 ^{° C.} 5.4 mm ² / s
Pour point 2 ^o C
Sulfur content 0.22%
Aromatic hydrocarbon content 17%
subjected to hydrotreating on a catalyst of the composition described in example 2, at a pressure of 4.6 MPa, a temperature of 385 ^o C.

Hydrotreated fraction with the following characteristics:
Viscosity at 50 ^{° C.} 5.0 mm ² / s
Pour point 4 ^o C
Sulfur content 0.018%
Aromatic hydrocarbon content 16%
sent for catalytic dewaxing and subsequent hydrogenation, which is carried out on the catalysts of example 1 at a pressure of 4.6 MPa, a temperature of 340-385 ^o With the stage of catalytic dewaxing and a temperature of 250-255 ^o With at the stage of hydrogenation.

The cycle of operation of the catalytic dewaxing and hydrogenation catalysts was 800 hours, after which the catalysts were treated with a hydrogen-containing gas at a pressure of 7.0 MPa, a temperature of 425 ^o C for 12 hours.

The base of electrical insulating oil, isolated by distillation of the dewaxed fraction, has the following characteristics:
Viscosity at 50 ^° C 6.5 mm ² / s
Pour point minus 50 ^o C
Flash point 138 ^o C
Refractive Index 1.4740
Aromatic hydrocarbon content 7%
Copper Plate Corrosion Resists
The output of the basics of electrical insulating oil 39.4%
Obtained in the conditions of examples 1-3, the base of the insulating oil is characterized by high thermal oxidative stability and low dielectric loss. To determine the thermo-oxidative stability, 0.25% wt. antioxidant additives agidol-1 and determine the induction period of oxidation by the method of the International Electrotechnical Commission. The oil test is carried out as follows: through a layer of oil at 120 ^o In the presence of a copper wire, oxygen is blown at a speed of 1 l / g of oil. The criterion for the stability of the oil is taken as the time during which the amount of low molecular weight acids equivalent to 0.28 mg of potassium hydroxide per 1 g of oil is released from the oil.

 The induction period of oxidation of commercial insulating oil obtained in examples 1, 2 and 3, is 170, 120 and 140 hours, respectively.

 Thus, the proposed method allows to obtain the basis of high-quality insulating oil, the yield of which is 13-16.7% more than in the method used as a prototype.

Claims (1)

A method of obtaining a base of electrical insulating oil by hydrotreating a straight-run oil fraction, followed by catalytic dewaxing, hydrogenating the dewaxed fraction and isolating the desired oil fraction, characterized in that the fraction boiling out within 250-420 ^° C is subjected to hydrotreating, catalytic dewaxing and hydrogenation are carried out in cycles of 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 idrirovanie fractions dewaxing is conducted to aromatics content in the oil 4-12 wt.