LOW COLORED SULPHONIC ACID

The present invention relates to the field of sulfonic acids and more particularly the field of weakly colored sulfonic acids, as well as their method of preparation.

[0002] Sulfonic acids, and in particular so-called organic sulfonic acids, such as, for example, methanesulfonic acid (AMS), para-toluenesulfonic acid (APTS), benzenesulfonic acid (BS ), trifluoro-methane-sulfonic acid are strong acids widely used in many applications, especially in catalysis and surface treatment, such as electroplating, pickling, cleaning, descaling, to name only the main of them, limit themselves to them.

[0003] However, it has been observed that aqueous solutions of such sulphonic acids corrode metals, the corrosion rates depending both on the acid concentration, on the temperature and on the nature of the metal. For example, at room temperature, type 304L or 1.4307 stainless steel is corrodible at AMS concentrations greater than 5% by weight in water. Such corrosion risks are unacceptable in many applications, and particularly for the storage of these acids mainly when they are in aqueous solution.

To make sulphonic acids little, if not not, corrosive towards metals, and particularly towards stainless steels, many works have already been carried out, among which a technique which has shown satisfactory results consists in the addition of nitrates in said acids. This method is in particular described by B. Gaur and HS Srinivasan (“British Corrosion Journal”, 34 (1), (1999), 63-66) who have shown that the addition of ferric ions or nitrates makes it possible to produce a corrosion inhibiting effect by AMS on various steels.

[0005] Other solutions have been studied, among which one can for example cite that described in application EP0931854, which proposes to inhibit the corrosion of stainless steels in organosulfonic acid medium, by adding at least one oxidant chosen from among salts or oxides of cerium (IV), iron (III), molybdenum (VI) or vanadium (V), nitrites and persulphates.

[0006] Sulfonic acids additivated with nitrites are very particularly advantageous because of their character which is very particularly not very corrosive towards metals and in particular stainless steels. These weakly corrosive sulfonic acids (also called “low corrosion”) unfortunately have the drawback of becoming colored more or less rapidly, depending on the nature of the sulfonic acid, the nitrite used, and the nitrite concentration in said sulfonic acid.

[0007] This coloring can prove to be troublesome for the applications envisaged, in particular when sulfonic acids are used as cleaning agents, as reaction catalysts for the manufacture of high added value products, and others. In addition, the coloring can be considered as resulting from the presence of impurities which, besides polluting the sulfonic acid and making it unsuitable for the intended use, can at least make it incompatible with commercial specifications.

This coloring therefore represents a major drawback for "low corrosion" sulfonic acids, that is to say for sulfonic acids which include nitrites to make them weakly corrosive vis-à-vis passivable metals and alloys, in particular based on iron, nickel, titanium, copper, aluminum, molybdenum, manganese, lead, and their alloys, as well as the couples of these metals or alloys obtained by contact (crimping, riveting, bolting, welding, brazing), in particular with respect to stainless steels, and in particular common stainless steels (for example of the AISI 304L and AISI 316L type), but also more generally any stainless steel as defined in standard NF EN 10088-1.

[0009] The Applicant has now discovered that the coloration of so-called “low corrosion” sulfonic acids is in particular due to the presence of chloride ions in said sulfonic acids.

In the present invention, it is considered that a sulfonic acid is "colored" when its APHA color is strictly greater than 20. Conversely, a weakly colored sulfonic acid within the meaning of the present invention is a sulfonic acid whose the APHA color is less than 20, preferably less than 15, more particularly less than 10, very particularly less than 5.

The APHA color is a color standard named for the American Public Health Association and defined by the ASTM D1209 standard, and more specifically the ASTM D1209-05 (201 1) standard. The APHA color is a color scale, sometimes also referred to as the “yellowing index”, which assesses the quality of liquids that are light to yellowish in color. The APHA color is measured using a colorimeter with a standard range from 0 to 200 APHA.

In the present invention, by "weak corrosion sulfonic acid" is meant a sulfonic acid whose potential remains almost at the same level and does not rise after application of a quantity of current of -800 μΑ.αττ 2 , for 1 minute, then stop the application of this current, as explained later in the “low corrosion” validation test protocol.

In other words, a weak corrosion sulfonic acid according to the present invention remains in the passive state after application of a current of -800 μΑ.αττ 2 , for 1 minute, while a sulfonic acid not in accordance with the present invention (corrosive) returns to the active state (corrosion) after depassivation by application of said quantity of current of -800 μΑ.αττ 2 , for 1 minute.

The low corrosion sulfonic acids of the present invention are conventional sulfonic acids in which at least one nitrite has been added, and whose nitrite / sulfonic acid molar ratio is between 200 ppm and 6000 ppm, preferably between 400 ppm and 2000 ppm, in particular between 500 ppm and 1900 ppm.

However, conventional sulphonic acids can contain chloride ions in more or less large amounts. The presence and quantity of chloride ions in conventional sulphonic acids can result from many factors, among which we can, without limitation, mention the chlorinated derivative (s) used in the process of manufacture of said conventional sulphonic acid itself, the chlorides or chlorinated derivatives present in the various solvents, additives, auxiliaries, fillers intended to formulate said sulphonic acid in order to facilitate its implementation, its use and its effectiveness in the envisaged applications, and other.

Without wishing to be bound by theory, it has been established that the presence of chloride ions causes the coloration of sulphonic acids to which nitrite ions have been added in order to give them non-corrosive or weakly corrosive properties.

It has now been discovered that it is possible to be able to have a weakly colored sulfonic acid, even when said acid comprises chloride ions, and added nitrite ions in order to give it non-corrosive or slightly corrosive properties.

[0018] Thus, and according to a first aspect, the present invention relates to a sulfonic acid comprising:

a chloride / sulphonic acid molar ratio of between 1 ppm and 200 ppm, preferably between 5 ppm and 200 ppm, more preferably between 10 ppm and 200 ppm, more preferably between 10 ppm and 190 ppm, limits included, and a molar ratio nitrite / sulphonic acid between 200 ppm and 6000 ppm, preferably between 400 ppm and 2000 ppm, particularly between 500 ppm and 1900 ppm, limits included,

and whose APHA color is less than 20, preferably less than 15, more particularly less than 10, very particularly less than 5.

In the present invention, sulfonic acid is understood to mean any sulfonic acid known to those skilled in the art and more particularly sulfonic acids of formula R-SO3H, where R represents a saturated or unsaturated, linear, branched or cyclic hydrocarbon chain , comprising from 1 to 12 carbon atoms, substituted or unsubstituted by one or more radicals and / or atoms chosen from halogen atoms (such as fluorine, chlorine, bromine), alkyl radicals containing from 1 to 6 atoms of carbon and 6- or 10-membered aryl and heteroaryl radicals.

By "alkyl" is meant a saturated, linear or branched hydrocarbon radical. The term “aryl” is understood to mean an aromatic radical, preferably phenyl or naphthyl, more preferably phenyl. By “heteroaryl” is meant an aromatic radical having one or more heteroatoms chosen from oxygen, nitrogen and sulfur.

Preferably R represents a hydrocarbon chain comprising from 1 to 6 carbon atoms, more particularly chosen from methyl, ethyl, n-propyl, / ' so-propyl, n-butyl, / ' so-butyl, sec-butyl , terf-butyl, linear or branched pentyl radicals, linear or branched hexyl radicals, and phenyl and naphthyl radicals.

Thus, and in a nonlimiting manner, the sulfonic acids included in the context of the present invention are preferably chosen from methanesulfonic acid, ethanesulfonic acid, n-propane-sulfonic acid, iso-propane-sulfonic acid, n-butane-sulfonic acid, / ' n-butane-sulfonic acid, sec-butane-sulphonic acid, tert-butane-sulphonic acid, trifluoro-methanesulfonic acid, para-toluenesulfonic acid, benzenesulfonic acid, naphthalenesulfonic acid and mixtures of two or more of them in all proportions.

[0023] According to a very particularly preferred embodiment, the sulfonic acid used in the context of the present invention is methanesulfonic acid, ethanesulfonic acid, trifluoromethanesulfonic acid or para-toluenesulfonic acid. , most preferably the sulfonic acid is methanesulfonic acid.

The sulfonic acid used in the context of the present invention can be sulfonic acid alone or as a mixture of two or more sulfonic acids, optionally in a solvent medium and optionally in mixture with one or more additives and / or loads well known to those skilled in the art.

Thus, the sulphonic acid (s) peuv (en) t be in a solvent medium, said solvent possibly being water or an organic solvent or a mixture of organic solvents, or else water mixed with one or more other organic solvents. As a general rule, the concentration of sulfonic acid (s) in the solvent (s) is between 0.01% and 100%, limits included, by weight of sulfonic acid (s). relative to the total weight of sulfonic acid (s) in a solvent medium, it being understood that when the concentration is equal to 100%, the amount of solvent is zero or negligible or not detectable. Preferably, this concentration is between 0.01% and 99.99%, preferably between 0.1% and 99.9%, more preferably between 0.5% and 75%, limits included, by weight of

The organic solvents indicated above and which can be used to dissolve the sulfonic acid (s) can be of any type known to those skilled in the art, and preferably the organic solvents soluble in water. , such as alcohols, sulphoxides, mineral or organic acids, more preferably

methanol, ethanol, dimethyl sulfoxide, sulfuric acid, to name only the most common and best known of them.

The additives and fillers which may be present as a mixture with the sulfonic acids can for example be, without limitation, one or more additives and / or fillers chosen from viscosity or rheology modifiers, foaming agents, anti-foaming agents, surfactants, disinfectants, biocides, stabilizers, oxidizing agents, enzymes, pigments, colorants, flame retardants, flame retardants, fragrances, flavors, and the like.

These various additives and fillers are present in amounts well known to those skilled in the art, which may vary depending on the desired effect, the nature of the sulfonic acid used and the application considered for said sulfonic acid used.

The addition of nitrite in the proportions indicated above can be carried out according to any method known to those skilled in the art, in particular by adding one or more nitrite (s) of alkali or alkaline earth metal, in solid form or dissolved in a solvent, such as water. Such sulphonic acids additivated by a nitrite are described, for example, in application EP0931854.

The amount of chlorides present in sulfonic acid can be easily controlled and adjusted depending on the nature of the manufacturing process of the sulfonic acid itself, its degree of purity, which can be improved according to one or several of the techniques known to those skilled in the art, such as distillation, recrystallization, and the like.

In addition, the amount of chlorides present in the sulfonic acid can be easily controlled and adjusted according to the nature of the possible solvent (s), additives and fillers which are added thereto. Those skilled in the art will easily understand that a sulfonic acid with a low chloride content will see this content increased, if it is decided, for example, to dilute said sulfonic acid in water with a high chloride concentration or to add a load. such as a salt containing chlorides.

The low corrosion sulfonic acid according to the present invention thus exhibits an APHA color is less than 20, preferably less than 15, more particularly less than 10, very particularly less than 5, that is to say an absence or almost no color, which makes it possible to have a low corrosion sulfonic acid thus meeting most or even all of the commercial specifications, in a very large number of fields of application.

[0033] The present invention also relates to a composition comprising at least one sulfonic acid as defined above, a solvent as defined above, preferably water, and optionally one or more additive (s) and / or load (s) as defined above.

The invention will be better understood with the aid of the examples which follow, said examples not being in any way limiting and serving only to illustrate the invention.

EXAMPLES

In a three-necked flask of 250 mL, are introduced, with stirring (400 rpm) at 20 ° C, 135 g of 70% methane-sulfonic acid (that is to say diluted to 70% by weight in water). The solution obtained contains a chloride / AMS molar ratio equal to 27 ppm.

From this methanesulfonic acid (AMS), already containing a chloride / AMS ratio of 27 ppm, 3 different samples are prepared containing variable chloride / AMS molar ratios. For this, chloride solutions, in the form of 0.1 N hydrochloric acid, are then added to the starting methanesulfonic acid solution.

Four samples are thus obtained with variable chloride levels:

- sample 1: molar ratio chlorides / AMS equal to 27 ppm (no added chloride)

- sample 2: molar ratio chlorides / AMS equal to 66 ppm

- sample 3: molar ratio chlorides / AMS equal to 100 ppm

- sample 4: chloride / AMS molar ratio equal to 220 ppm.

Using an automatic pipette, then added for 1 min, in each sample, 0.24 mL (or 0.30375 g) of 40% NaNO 2 (that is to say diluted to 40% by weight in water) (i.e. 0.1215 g of pure NaNO2). The NaNO 2 / AMS molar ratio is 1800 ppm.

The flask is immediately closed in a hermetic manner and the assembly is placed under stirring (400 rpm) for 1 hour at 20 ° C. Nitrogen is then bubbled through the solution (flow rate 10 mL.mn- 1 ) for 360 min.

The color of each sample is then measured using a LICO 620 colorimeter from the company HACH, with a standard range between 0 and 200 APHA. The device is calibrated beforehand with standard solutions ranging from 0 to 200 APHA. A 4 mL sample of the solution whose color is to be determined is introduced into a cuvette supplied by Hach and the color is read automatically on the device.

The results are collated in Table 1 below:

- Table 1 -

It is considered that there is absence of coloration when the measured value of APHA color is less than 20. Thus, it is found that for a chloride / AMS ratio less than or equal to 200 ppm, the AMS / inhibitor mixture is colorless , whereas for a chloride / AMS ratio equal to 220 ppm, the APHA value is greater than 20 and the methanesulfonic acid is colored.

There is therefore a correlation between the rate of chlorides in a sulfonic acid containing a corrosion inhibitor, in the form of nitrites: the lower the rate of chlorides, the less the solution is colored, or even be considered as colorless in many commercial specifications.

Measurement of chlorides in a sulfonic acid:

The measurement of the amount of chlorides present in a sulfonic acid is carried out by argentimetry using a potentiometer equipped with a silver sulfide electrode marketed by the company Metrohm AG under the reference 6.0404.100.

Precisely weighed 35 g of sulfonic acid in a beaker containing enough acetone to be able to immerse the electrode, and titrated with a 0.005 N solution of silver nitrate in acetic acid. The quantity (Qci) of chlorides (in ppm by mass) is expressed by the following formula:

Qc | _ Volume AgNOs (mL) x N AgNOs (m equivalents / mL) x 35,500

sample weight (gram)

Measurement of nitrites in a sulfonic acid:

The nitrites can be assayed by any method known to those skilled in the art and for example by ion chromatography.

The samples to be tested are diluted approximately 150 times (0.6 g of sample then supplemented to 100 mL with ultra-pure water) and passed through an ICS5000 device from the company Dionex ™. The detection mode is conductimetry and the results are read against a previously established calibration curve.

The calibration range is prepared from nitrite standards, as well as an AMS matrix. Commercial nitrite standards (1000 mg.L "1 in water, supplier CPA). Solutions of 1, 10 and 100 mg.L " 1 are prepared by diluting them in ultra pure water.

The AMS matrix is ​​produced from a commercial solution of 70% AMS (Sigma-Aldrich) diluted in ultra pure water. To do this, 0.6 g of 70% AMS is weighed into a 100 mL volumetric flask, then made up with ultra pure water.

"LOW CORROSION" VALIDATION TEST PROTOCOL

In order to check the "low corrosion" quality, within the meaning of the present invention, of a sulfonic acid, an electrochemistry test is carried out using a 3-electrode assembly connected to a BIOLOGIC VMP3 potentiostat. :

1) reference electrode: saturated calomel electrode or "ECS",

2) working electrode: 304L stainless steel test tube of size 1 cm 2 , and

3) against platinum electrode.

The test piece of the material to be tested is polished with P400 abrasive paper and then passivated for 1 hour in a 10% nitric acid solution at room temperature. This allows an identical starting state for all tests. The temperature of the test is thermostatically controlled at 20 ° C ± 2 ° C.

The applied protocol comprises the following three steps:

a) monitoring of the abandonment potential of the working electrode (304L) in the sulfonic acid with additives according to the method of the present invention, that is to say measurement of the potential of the material in the solution as a function of time , during 30 minutes,

b) immersion of the three-electrode system in a standard sulphonic acid solution (ie without additives), then application to the working electrode of a current of -800 μΑ.αττ 2 for 1 minute in order to depassivate the material of artificially by fixing the potential thereof in the corrosion range, c) immersing the three-electrode system again in the solution of additivated sulfonic acid according to the process of the present invention, and again monitoring the potential of abandonment of the working electrode, until stabilization thereof.

VALIDATION TEST RESULTS

In the case of a standard methanesulfonic acid, that is to say without additives, in solution at 70% by weight in water, after application of an amount of current of -800 μΑ. αττ 2 , the potential of the working electrode (304L stainless steel test tube) drops to around -350 mV, which corresponds to the passage of 304L stainless steel in the active state. When the application of the current is stopped, the potential of the material remains almost at the same level and does not rise again. 304L stainless steel remains in the active state and corrodes.

The behavior is completely different in a 70% by weight solution in water of a methanesulphonic acid additive with nitrites.

We first note a potential for abandonment of stainless steel 304L of the order of 750 mV after 30 minutes. When applying the current of -800 μΑ.αττ 2 , the potential of the material drops to around -200 mV (change from 304L stainless steel to the active state). When the application of the current is stopped, the potential of the material rises very quickly. It is 780 mV after 2 hours of potential monitoring and a total absence of corrosion is noted.

In all cases (samples 1, 2, 3 and 4 above), the methanesulfonic acid additive with sodium nitrite is a low corrosion methanesulfonic acid within the meaning of the present invention.
CLAIMS

1. Sulfonic acid comprising:

a chloride / sulfonic acid molar ratio between 1 ppm and 200 ppm, preferably between 5 ppm and 200 ppm, more preferably between 10 ppm and 200 ppm, more preferably between 10 ppm and 190 ppm, limits included, and

a nitrite / sulphonic acid molar ratio of between 200 ppm and 6000 ppm, preferably between 400 ppm and 2000 ppm, particularly between 500 ppm and 1900 ppm, limits included,

and whose APHA color is less than 20, preferably less than 15, more particularly less than 10, very particularly less than 5.

2. Sulfonic acid according to claim 1 chosen from the sulfonic acids of formula R-SO3H, where R represents a saturated or unsaturated, linear, branched or cyclic hydrocarbon chain, comprising from 1 to 12 carbon atoms, substituted or unsubstituted by a or more radicals and / or atoms chosen from halogen atoms, alkyl radicals containing from 1 to 6 carbon atoms and 6 or 10 membered aryl and heteroaryl radicals.

3. Sulfonic acid according to any one of claims 1 or 2, selected from methanesulfonic acid, ethanesulfonic acid, n-propane-sulfonic acid, / ' so-propane-sulfonic acid. , n-butanesulphonic acid, iso-butanesulphonic acid, sec-butanesulphonic acid, terf-butanesulphonic acid, trifluoromethanesulphonic acid, para-toluenesulphonic acid, l benzenesulfonic acid, naphthalenesulfonic acid and mixtures of two or more of them in all proportions.

4. Sulfonic acid according to any one of claims 1 to 3, chosen from methane-sulfonic acid, ethanesulfonic acid, trifluoromethanesulfonic acid and para-toluenesulfonic acid, preferably sulfonic acid is methanesulfonic acid.

5. Sulfonic acid according to any one of claims 1 to 4 in a solvent medium, said solvent possibly being water or an organic solvent or a mixture of organic solvents, or else water mixed with one or more other solvents. organic.

6. Sulfonic acid according to any one of claims 1 to 5 as a mixture with one or more additives and / or fillers chosen from viscosity or rheology modifiers, foaming agents, anti-foaming agents, surfactants, disinfectants. , biocides, stabilizers, oxidizing agents, enzymes, pigments, colorants, flame retardants, flame retardants, fragrances and flavors.

7. Composition comprising at least one sulfonic acid according to any one of claims 1 to 4, a solvent, and optionally one or more additive (s) and / or filler (s).