DE3714856A1 - Inhibitors of corrosion by CO2 and H2S in water-in-oil emulsions - Google Patents

Abstract

There are proposed inhibitors of corrosion by CO2 and H2S in water-in-oil emulsions, containing a) imidazoline or tetrahydropyrimidine derivatives of the general formula I <IMAGE> and/or b) their open-ring precursors of the general formula II <IMAGE> where in the formulae I and II the radical R<1> stands for C7-C22-alkyl or -alkenyl, n stands for an integer 2 or 3, x denotes an integer from 0 to 5, Y stands for H, C8-C18-alkyl or -alkenyl, and in which in the formula I the radical Y can also stand for <IMAGE> with the above substituent meanings and in which in the formula II the radical Y can also stand for <IMAGE> with the above substituent meanings.n

Description

The invention relates to inhibitors against the corrosion of CO ₂ and H ₂ S in water-in-oil emulsions which contain imidazoline or tetrahydropyrimidine derivatives and / or their ring-open precursors.

The new inhibitors are effective against corrosion by CO ₂ and H ₂ S (“sour gas”) during the transport and storage of crude oils, which are generally in the form of water, in particular salt water-in-oil, emulsions.

As is well known, one brings in oil production, transport and storage of the oil through a solution or dispersion of corrosion inhibitors Inject into the oil so that the surface of the oil metal parts in contact form a protective layer.

For this purpose, DE-A-28 46 979 describes corrosion inhibitors that of an imidazoline salt, an oil-soluble solvent exist for the imidazoline salt and a hydrocarbon oil.

However, it has been shown that imidazoline salts, as described in the cited publication, do not corrode H ₂ S and CO ₂ , especially in water-in-oil emulsions containing salt water (hereinafter referred to as "W / O emulsions") suppress sufficiently. It is also disadvantageous that these imidazolines must be used with an oil-soluble solvent and a hydrocarbon oil.

DE-A-31 09 827 describes an inhibitor against the corrosion of CO ₂ and H ₂ S in W / O emulsions. This inhibitor consists of a reaction product

• A) Compounds or their salts of the formula III or precursors of formula IIIa in which mean: R ¹ = C ₆ - to C ₂₂ -alkyl or -alkenylX = -OH, -NH ₂ or R ² = C ₄ to C ₁₈ alkyl
  n = 2
  and
• B) elemental sulfur.

These inhibitors are very effective, but theirs is Production due to the mandatory incorporation of sulfur energy-intensive and its effect as an inhibitor is not yet in all Cases optimally.

EP-A-01 03 737 describes an inhibitor against the corrosion of CO ₂ and H ₂ S in W / O emulsions containing

• A) Compounds of formula IV or their ring-open precursors of the formula IVa in which R ¹ = C ₆ - to C ₂₂ -alkyl or -alkenylX = -OH, -NH ₂ or R ² = C ₄ - to C ₁₈ -alkyl and n = 2 or 3, and
• B) Maleic acids of formula V in which R ³ = C ₈ to C ₂₂ alkyl or alkenyl, components A and B in the molar ratio A: B = 1: 4 to 4: 1.

These inhibitors are already very effective, a further increase in Corrosion protection of inhibitors is desirable.

The invention has for its object to provide new inhibitors against the corrosion of CO ₂ and H ₂ S in W / O emulsions, which are even more effective than the known inhibitors.

This object is achieved with inhibitors of the type mentioned, containing

• a) Imidazoline or tetrahydropyrimidine derivatives of the general formula I and or
• b) their ring-open precursors of the general formula II where in formulas I and II
  the radical R ^{1 represents} C ₇ -C ₂₂ alkyl or alkenyl,
  n represents an integer of 2 or 3,
  x represents an integer from 0 to 5,
  Y represents H, C ₈ -C ₁₈ alkyl or alkenyl,
  and in the formula I the radical Y also for can stand with the above substituent meanings and in which in the formula II the radical Y is also for can stand with the above substituent meanings.

According to a preferred embodiment, the inhibitors according to the invention contain imidazoline derivatives of the general formula I in which R ^{1 is} a C ₁₇ alkenyl radical, n is 2, x is 0 and Y is a hydrogen atom.

According to a further preferred embodiment, the inhibitors according to the invention contain precursors of the general formula II in which R ^{1 is} C ₁₅ -C ₁₉ alkenyl, n is 2, x is an integer from 1 to 5 and Y is a C ₁₃ - Alkenylrest means.

In the compounds of the general formulas I and II, the radical R ^{1 represents} a C ₇ -C ₂₂ alkyl radical or a C ₇ -C ₂₂ alkenyl radical. These residues can be straight-chain or branched. The alkyl or alkenyl radicals preferably have 8 to 19, in particular 15 to 19, carbon atoms. The alkenyl radicals can have one or more double bonds.

The radical Y represents hydrogen, C ₈ -C ₁₈ alkyl or C ₈ -C ₁₈ alkenyl. In the general formula I, the radical Y can also be for

stand, wherein R ¹ , n and x have the above substituent meanings.

In the general formula II, the radical Y can also be used for

stand, wherein R ¹ , n and x have the above meanings.

If Y is alkyl or alkenyl, C ₁₀ -C ₁₈ alkyl or alkenyl radicals are preferred.

The production of the heterocycles and their ring-open precursors expediently takes place as follows:

Men preferably uses one mole of imidazoline or tetrahydropyrimidine derivative or their ring-open precursors with one mole of urea and if desired, one mole of alkylamine with stirring under heat. Appropriately is heated to 160 ° C for about 8 hours, whereby ammonia splits off. The mixture is then heated to complete the reaction another 2 hours at, for example, 120 ° C. and a pressure of, for example 27 mbar. This way of working creates imidazoline or Tetrahydropyrimidine derivatives or their ring-open precursors, in which the radical Y represents hydrogen or alkyl.

One can prepare the imidazoline or tetrahydropyrimidine derivatives or their ring-open precursors, in which the rest Y are those shown above Corresponds to formulas, by producing, for example, 2 mol of the imidazoline or tetrahydropyrimidine derivative or the like ring-open preliminary product heated with, for example, one mole of urea. It is advantageous to stir at about 160 ° C. for about 8 hours, with ammonia splits off. It is useful to complete the reaction then heated again for 2 hours at 120 ° C / 27 mbar.  

For the preparation of the ring-open precursors of the general formula II you can also work in a one-pot reaction. To do this, for example 1 mole of polyethyl (propylene) amine, 1 mole of fatty acid and 1 mole Urea, and optionally 1 mol of alkylamine in the heat. Appropriately you work at about 160 ° C and heated for 8 hours. Here water and ammonia are split off. To complete the reaction expediently heated again at about 27 mbar for 2 hours. Here the precursors of the general formula II are obtained, in which the radical Y represents hydrogen or alkyl.

By professional modification of the above-mentioned working methods all inhibitors of the general formulas I and II can be prepared.

The inhibitors according to the invention are in the water-in-oil emulsion generally in amounts of 2 to 2000 ppm by weight, preferably 3 to 100 ppm by weight, in particular 5 to 50 ppm by weight, based on the weight of the Emulsion added.

In oil production, it can be advantageous to use an inhibitor Feed probe in such a way that, e.g. B. at a shutdown, a Dissolve the inhibitor in a suitable solvent in the probe is pressed in, preferably in discontinuous addition (batch addition). As a solvent such. B. liquid Hydrocarbons, for example petroleum condensate, into consideration. The Concentration of the inhibitor is, based on the solution, in generally 5 to 20% by weight, preferably 5 to 10% by weight.

The invention is illustrated by the following examples.

example 1

139.6 g (0.6 mol) of 2-heptadecenyl-1-aminoethylimidazoline (prepared from 1 mol of oleic acid and 1 mol of diethylenetriamine) are heated to about 80 ° C. and then 24 g (0.6 mol) of urea are introduced. The mixture is then heated to 160 ° C. for 8 hours with stirring. This releases ammonia. To complete the reaction, residual ammonia is removed for 2 hours at 120 ° C./27 mbar. The product of the formula I in which R ^{1 is} C ₁₇ H ₃₃ , n is 2, x is 0 and Y is H is obtained in quantitative yield.

Example 2

21.6 g (0.4 mol) of diethylenetriamine residue (main constituent is triethylenetetramine and higher polyamines and aminoethylethanolamine [more than 90% of the total mixture); the residue amines are obtained in the diethylenetriamine distillation; the product has the characteristics n = 2 and x = 1-5], 120.6 g (0.4 mol) tall oil fatty acid (mixture of free fatty acids with C ₁₅ -C ₁₉ in the alkyl radical with main components of oleic acid, linoleic acid and linolenic acid ( about 90%), 80 g (0.4 mol) of i-tridecylamine and 24 g (0.4 mol) of urea are combined and heated at 160 ° C. for 8 hours. Here ammonia escapes. The mixture is then stirred for a further 2 hours at 120 ° C./27 mbar. The product of the general formula II with R ¹ = C ₁₅ -C ₁₉ , n = 2, x = 1-5 and Y = C ₁₃ H _{27 is obtained} in quantitative yield.

In general, in the examples above, acids of the formula R ¹ COOH, in which R ^{1 has} the meanings mentioned above, can be reacted with diethylenetriamine, dipropylenetriamine, aminoethylethanolamine or aminopropylpropanolamine. Suitable acids of the formula R ¹ COOH are e.g. B. 2-ethylhexanoic acid, nonanoic acid, oleic acid, stearic acid, lauric acid, elaidic acid, and mixtures of natural fatty acids such as coconut or tallow fatty acid and tall oil fatty acid.

Urea derivatives whose imidazoline component is derived from the C ₁₂ -C ₂₀ carboxylic acids are particularly valuable.

The imidazoline or tetrahydropyrimidine-urea derivatives or their ring-open precursors used as inhibitors according to the invention are advantageous over the corresponding, non-derivatized compounds in that they provide improved protection against corrosion. The corrosion protection exists against CO ₂ alone as well as against the combination of CO ₂ and H ₂ S.

To test the inhibitor compositions, a dynamic test (so-called "Wheel test") performed a method according to the corrosion inhibitors be tested for oil and gas production.

Steel sheets measuring 130 mm × 10 mm × 1 mm were chosen as test coupons. These strips of metal were sanded, degreased with toluene and weighed. White spirit containing 3% NaCl - based on water - emulsified as test medium. The emulsion contained 50% by weight of salt water and was saturated with H ₂ S + CO ₂ .

Then 25 ppm - based on the weight of the emulsion - of inhibitor added.  

The degreased and weighed sheets were then added to the emulsion introduced and at 80 ° C for 16 hours of mechanical movement (40 rpm by means of a shaft rotating the test vessels).

The test panel strips were then inhibited with an acid cleaned, degreased and after drying to determine weight loss weighed. The evaluation was made in comparison to the blank value (experiment without addition of inhibitor).

The speed of corrosion and the percentage corrosion protection Z was calculated from the results of the weighing:

where G _{0 is} the rate of corrosion without inhibitor and G _{1 is} the rate with inhibitor.

The results are shown in the following tables.

Table I

Table II

Table III

Table IV

Claims (3)

1. Containing inhibitors against the corrosion of CO ₂ and H ₂ S in water-in-oil emulsions

• a) Imidazoline or tetrahydropyrimidine derivatives of the general formula I and or
• b) their ring-open precursors of the general formula II where in formulas I and II
  the radical R ^{1 represents} C ₇ -C ₂₂ alkyl or alkenyl,
  n represents an integer of 2 or 3,
  x represents an integer from 0 to 5,
  Y represents H, C ₈ -C ₁₈ alkyl or alkenyl,
  and in the formula I the radical Y also for can stand with the above substituent meanings and in which in the formula II the radical Y is also for can stand with the above substituent meanings.

2. Inhibitors according to claim 1, containing imidazoline derivatives of the general formula I, in which R ^{1 is} a C ₁₇ alkenyl radical, n is 2, x is 0 and Y is a hydrogen atom. 3. Inhibitors according to claim 1, containing precursors of the general formula II, in which R ^{1 is} C ₁₅ -C ₁₉ alkenyl, n is 2, x is an integer from 1 to 5 and Y is a C ₁₃ alkenyl radical means.