RU2749958C2 - Method for protecting steel against corrosion in mineralized water-oil environments containing hydrogen sulfide - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: invention relates to the field of metal corrosion protection and can be used to protect equipment and pipelines from corrosion in contact with saline water-oil media containing hydrogen sulfide in the oil industry. The method includes adding 2-cyclohexylaniline with a concentration of 25-200 mg / l to a mineralized water-oil medium containing hydrogen sulfide.

EFFECT: increased degree of corrosion protection of steel equipment - (87.9 - 96.04)% and decreased corrosion rate in the presence of 2-cyclohexylaniline by 8.3-25.3 times.

1 cl, 1 tbl, 3 ex

Description

The invention relates to a method of protecting metals from corrosion in mineralized water-oil environments with inhibitors and can be used to protect against corrosion of equipment in the oil industry in contact with hydrogen sulfide environments.

Known methods of protecting steel from corrosion in acidic environments using inhibitors based on aromatic and heterocyclic compounds, such as catapins, which are alkylbenzylpyridinium chlorides differing in the number of carbon atoms in the alkyl chain. The following brands of catapins are known: A, K, B-300, BPV, EPV (TU 6-01-530-70. Introduced 06/01/1971.13 p.); condensation product of benzylamine with urotropine (TU 6-02-1192-79. Corrosion inhibitor BA-6. Introduced 01.01.80.13 p.); a mixture of alkylbenzylpyridine and a cyclic amine (TU 6-46893387-34-90. Corrosion inhibitor KI-1. Introduced 07.01.90.12 s.); a mixture of toluene diisocyanate derivatives (TU 6-03-31-81. Corrosion inhibitor TDA. Introduced 02/01/82.13 p.); quaternary pyridinium salt (TU 6-01-11-15-72. Corrosion inhibitor KPI-3. Introduced 01.02.73.14 p.).

However, these inhibitors do not have a high efficiency of steel protection in saline water-oil environments containing hydrogen sulfide.

The closest analogue in structure and efficiency is the corrosion inhibitor PB-5, which is a condensation product of aniline and urotropine (TU 6-01-28-92. Corrosion inhibitor PB-5. Introduced 01.01.93. 11 p.). The disadvantage of this inhibitor is its low efficiency in mineralized water-oil environments containing hydrogen sulfide.

The problem to be solved by the claimed technical solution is to increase the efficiency of steel protection in saline water-oil environments containing hydrogen sulfide.

The claimed technical solution proposes a method for protecting steel from corrosion in saline water-oil environments containing hydrogen sulfide, including the addition of 2-cyclohexylaniline at a concentration of 25-200 mg / l to a mineralized water-oil environment containing hydrogen sulfide. 2-Cyclohexylaniline was prepared by catalytic reduction of 2- (2-cyclohexenyl) aniline on palladium on carbon (Pd / C) in ethyl acetate.

Tests of the protective action of 2-cyclohexylaniline as a corrosion inhibitor of steel in mineralized water-oil environments containing hydrogen sulfide were carried out in laboratory conditions by the gravimetric method in accordance with GOST 9.506-87 "Inhibitors of metal corrosion in water-oil environments", Standards Publishing House, 1988.

The working media used was a water-oil mixture composed of a model of saline water (MMW) of composition, g / l: NaCl - 163.00; CaCl ₂ ⋅6H ₂ O 34.00; CaSO ₄ ⋅2H ₂ O - 0.14; MgCl ₂ ⋅6H ₂ O - 17.00 and oil. The hydrogen sulfide content was 1300 mg / l. Plates made of steel grade 3 (GOST 380-90) were used as witness samples.

Degreased and dried to constant weight samples of steel grade 3 were placed in a working environment for 6 hours at 20 ° C with and without the addition of the proposed inhibitor. After the holding time, the samples were thoroughly washed in a stream of water, immersed for 5-10 minutes in an alkali solution, washed again with running water, and dried to constant weight. Then the samples were weighed with an accuracy of 0.0002 g.

The corrosion rate (p), the degree of steel protection against corrosion (Z) were determined in accordance with the formulas (1) and (2):

where m ₁ -m ₂ is the change in mass, g;

S — sample area, m;

t - test time, h.

where p ₁ is the corrosion rate in an environment without an inhibitor, g / m ² ⋅h;

p ₂ - corrosion rate in an inhibited environment, g / m ² ⋅h.

The essence of the claimed technical solution is confirmed by examples of specific implementation.

Example 1.

Synthesis of 2-cyclohexylaniline.

To a solution of 5 g of 2- (2-cyclohexenyl) aniline in 50 ml of ethyl acetate, Pd / C (10% molar) was added and stirred on a magnetic stirrer in a hydrogen atmosphere. Upon completion of the reaction (control by TLC), the reaction mass was filtered off, the solvent was removed under reduced pressure. 4.7 g of product was obtained with a yield of 93%. ¹ H NMR spectrum (CDCl ₃ , δ / ppm, J / Hz): 1.29-1.37 m (1H, H ^4'a ), 1.43-1.51 m (4H, H ^2'a , H ^3'a , H ^5'a , H ^6'a ), 1.81-1.85 m (1H, H ^4'b ), 1.92-1.96 m (4H, H ^2'b , H ^3'b , H ⁵ ' ^b , H ^6'b ), 2.50-2.55 m (1H, H ^{1 '} ), 3.72 br. from. (2H, NH ₂ ), 6.72 d (1H, J 7.7, H ³ ), 6.83 t (1H, J 7.7, H ⁵ ), 7.06 t (1H, J 7.7, H ⁴ ), 7.17 d (1H, J 7.7 , H ⁶ ). ¹³ C NMR spectrum (CDCl ₃ , δ / ppm, J / Hz): 26.42 (C ^{4 '} ); 27.22 (C ^{3 '} , C ^5' ); 32.88 (C ^{2 '} , C ^6' ); 38.46 (C ^{1 '} ); 115.97 (C ³ ); 119.14 (C ⁵ ); 126.02 (C ⁶ ); 126.48 (C ⁴ ); 132.05 (C ² ); 143.26 (C ¹ ).

Example 2.

Testing the effectiveness of the protective action of 2-cyclohexylaniline as a corrosion inhibitor of steel was carried out according to the above procedure. The water-oil mixture IIM: oil with a content of hydrogen sulphide CH ₂ s = 1300 mg / l, the corrosion rate without inhibitor is 0.91 g / m ² ⋅ch, and in the presence of 200 mg / l of 2-tsiklogeksilanilina (hereinafter the reagent) - 0.036 g / m ² ⋅h. The degree of protection against corrosion under the specified conditions is 96.04%.

Example 3.

Tests of the effectiveness of corrosion protection by the prototype (inhibitor PB-5) were carried out similarly to example 2. The corrosion rate in the water-oil mixture of MMV: oil containing hydrogen sulfide CH ₂ s = 1300 mg / l is 0.91 g / m ² h without reagent and 0.46 g / m ² ⋅h in the presence of 200 mg / l of the prototype. The degree of protection under these conditions is 49.5%.

The table shows other examples of testing the reagent as a corrosion inhibitor for steel in saline water-oil environments containing hydrogen sulfide.

The test results shown in the table indicate the high efficiency of the proposed steel corrosion inhibitor in saline water-oil environments containing hydrogen sulfide. The highest efficiency is achieved when the inhibitor concentration is from 25 to 200 mg / l. With an increase in the concentration of the inhibitor above 200 mg / L, the degree of protection does not change significantly, and with a decrease in its concentration below 25 mg / L, a sharp decrease in the degree of protection is observed. In the case of the prototype at a concentration of 200 mg / l corrosion rate is 0.46 g / m ² ⋅ch, and the degree of protection is equal to 49.5%.

The advantages of the proposed steel corrosion inhibitor over the prototype are as follows:

1. High degree of corrosion protection with 2-cyclohexylaniline (87.9-96.04%) compared to the prototype (49.5%).

2. Reduction of the corrosion rate of steel in the presence of 2-cyclohexylaniline by 8.3-25.3 times, and in the presence of a prototype - by 1.9 times.

3. Effective dosages of the proposed inhibitor are 25-200 mg / l (degree of protection 87.9-96.04%), and in the presence of a prototype, even at dosages of 200 mg / l, the degree of protection does not exceed 49.5%.

The results obtained allow us to conclude that the proposed method for protecting steel from corrosion in mineralized water-oil environments containing hydrogen sulfide is highly effective, which can be used in the oil industry.

Claims (1)

A method of protecting steel against corrosion in mineralized water-oil environments containing hydrogen sulfide, including the addition of 2-cyclohexylaniline with a concentration of 25-200 mg / l to a mineralized water-oil environment containing hydrogen sulfide.