Weakly coloured sulfonic acid

Abstract

The subject of the present invention is a weakly corrosive and weakly coloured sulfonic acid, with an APHA colour index of less than 20, comprising chlorides and nitrites in a chloride/sulfonic acid molar ratio of between 1 ppm and 200 ppm, and a nitrite/sulfonic acid molar ratio of between 200 ppm and 6000 ppm, limits inclusive.

Claims

1. Sulfonic acid comprising: a chloride/sulfonic acid molar ratio of between 1 ppm and 200 ppm, limits inclusive, and a nitrite/sulfonic acid molar ratio of between 200 ppm and 6000 ppm, limits inclusive, and the APHA colour of which is less than 20.

2. The sulfonic acid according to claim 1, having the formula R—SO.sub.3H, where R is selected from linear, branched or cyclic hydrocarbons having from 1 to 12 carbon atoms, where the hydrocarbons are unsubstituted or substituted with one or more radicals and/or atoms selected from halogen atoms, alkyl radicals containing from 1 to 6 carbon atoms, aryl or heteroaryl radicals having 6 or 10 ring members.

3. The sulfonic acid according to claim 1, selected from methanesulfonic acid, ethanesulfonic acid, n-propanesulfonic acid, iso-propanesulfonic acid, n-butanesulfonic acid, iso-butanesulfonic acid, sec-butanesulfonic acid, tert-butanesulfonic acid, trifluoromethanesulfonic acid, para-toluenesulfonic acid, benzenesulfonic acid, naphthalenesulfonic acid, or mixtures thereof.

4. The sulfonic acid according to claim 1, selected from the group consisting of methanesulfonic acid, ethanesulfonic acid, trifluoromethanesulfonic acid and para-toluenesulfonic acid.

5. Composition comprising at least one sulfonic acid according to claim 1, and a solvent, where said solvent is water, an organic solvent a mixture of organic solvents, or water as a mixture with one or more organic solvents.

6. Composition comprising at least one sulfonic acid according to claim 1, and one or more additives and/or fillers selected from viscosity or rheology modifiers, foaming agents, anti-foams, surfactants, disinfectants, biocides, stabilizers, oxidizing agents, enzymes, pigments, dyes, fire retardants, flame retardants, fragrances and aromas.

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

8. The sulfonic acid according to claim 1, where the sulfonic acid is methanesulfonic acid.

9. The sulfonic acid according to claim 1, where the chloride/sulfonic acid molar ratio is between 5 ppm and 200 ppm, limits inclusive, and the nitrite/sulfonic acid molar ratio is of between 400 ppm and 2000 ppm, limits inclusive, and the APHA colour of which is less than 15.

10. The sulfonic acid according to claim 1, where the chloride/sulfonic acid molar ratio is between 10 ppm and 200 ppm, limits inclusive, and the nitrite/sulfonic acid molar ratio is between 400 ppm and 2000 ppm, limits inclusive, and the APHA colour of which is less than 10.

11. The sulfonic acid according to claim 1, where the chloride/sulfonic acid molar ratio is between 10 ppm and 190 ppm, limits inclusive, and the nitrite/sulfonic ratio is between 500 ppm and 1900 ppm, limits inclusive, and the APHA colour is less than 5.

Description

EXAMPLES

(1) 135 g of methanesulfonic acid at 70% (that is to say diluted to 70% by weight in water) are introduced, with stirring (400 rpm) at 20° C., into a 250 ml three-necked round-bottomed flask. The solution obtained contains a chlorides/MSA molar ratio equal to 27 ppm.

(2) Three different samples containing variable chlorides/MSA molar ratios are prepared from this methane sulfonic acid (MSA), already containing a chlorides/MSA ratio of 27 ppm. For this, solutions of chloride, in the form of 0.1 N hydrochloric acid, are then added to the starting methanesulfonic acid solution.

(3) Four samples with variable chloride contents are thus obtained:

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

(5) sample 2: chlorides/MSA molar ratio equal to 66 ppm

(6) sample 3: chlorides/MSA molar ratio equal to 100 ppm

(7) sample 4: chlorides/MSA molar ratio equal to 220 ppm.

(8) By means of an automatic pipette, 0.24 ml (i.e. 0.30375 g) of 40% (that is to say diluted to 40% by weight in water) NaNO.sub.2 (i.e. 0.1215 g of pure NaNO.sub.2) is then added, over the course of 1 min, to each sample. The NaNO.sub.2/MSA molar ratio is 1800 ppm.

(9) The round-bottomed flask is immediately hermetically closed and the whole is stirred (400 rpm) for 1 hour at 20° C. Nitrogen is then sparged into the solution (flow rate 10 ml.Math.min.sup.−1) for 360 min.

(10) The colour 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 pre-calibrated with standard solutions ranging from 0 to 200 APHA. A 4 ml sample of the solution of which it is desired to determine the colour is introduced into a cuvette supplied by Hach and the colour is read automatically on the device.

(11) The results are collated in Table 1 below:

(12) TABLE-US-00001 TABLE 1 Sample tested APHA colour 1 2 2 7 3 12 4 23

(13) It is considered that there is an absence of colouring when the APHA colour value measured is less than 20. Thus, it is noted that, for a chlorides/MSA ratio of less than or equal to 200 ppm, the MSA/inhibitor mixture is colourless, whereas for a chlorides/MSA ratio equal to 220 ppm, the APHA value is greater than 20 and the methanesulfonic acid is coloured.

(14) There is therefore a correlation between the chloride content in a sulfonic acid containing a corrosion inhibitor, in nitrite form: the lower the chloride content, the less coloured the solution is, or the solution can even be considered to be colourless in many commercial specifications.

(15) Measurement of Chlorides in a Sulfonic Acid:

(16) The amount of chlorides present in a sulfonic acid is measured by argentometry using a potentiometer equipped with a silver sulfide electrode sold by the company Metrohm AG under the reference 6.0404.100.

(17) Precisely 35 g of sulfonic acid are weighed into a beaker containing enough acetone to be able to immerse the electrode, and titration is carried out with a 0.005 N silver nitrate solution in acetic acid. The amount (Q.sub.Cl) of chlorides (in ppm by weight) is expressed by the following formula:

(18) $Q_{\mathrm{Cl}}=\frac{\mathrm{Volume}{\mathrm{AgNO}}_3\left(\mathrm{ml}\right)\times N{\mathrm{AgNO}}_3\left(m\mathrm{equivalent}/\mathrm{mL}\right)\times 35500}{\mathrm{weight}\mathrm{of}\mathrm{the}\mathrm{sample}\left(\mathrm{grams}\right)}$
Measurement of the Nitrites in a Sulfonic Acid:

(19) The nitrites can be quantitatively determined according to any method known to those skilled in the art and for example by ion chromatography.

(20) The samples to be tested are diluted, approximately 150 times (0.6 g of sample then made up to 100 ml with ultrapure water), and passed over an ICS5000 instrument from the company Dionex™. The detection mode is conductimetry and the results are read relative to a pre-established calibration curve.

(21) The calibration range is prepared from nitrite standards, and also from an MSA matrix. Solutions of the commercial nitrite standards (1000 mg.Math.l.sup.−1 in water, supplier CPA) are prepared at 1, 10 and 100 mg.Math.l.sup.−1 by diluting them in ultrapure water.

(22) The MSA matrix is prepared from a commercial solution of MSA at 70% (Sigma-Aldrich) diluted in ultrapure water. To do this, 0.6 g of 70% MSA are weighed into a 100 ml volumetric flask, then the volume is made up with ultrapure water.

(23) “Low-Corrosion” Validation Test Protocol

(24) In order to verify the “low-corrosion” quality, within the meaning of the present invention, of a sulfonic acid, an electrochemical test is carried out using an assembly of 3 electrodes connected to a Biologic VMP3 potentiostat:

(25) 1) reference electrode: saturated calomel electrode or “SCE”

(26) 2) working electrode: test specimen of 304L stainless steel, 1 cm.sup.2 in size, and

(27) 3) platinum counter electrode.

(28) The test specimen of the material to be tested is polished with P400 abrasive paper then passivated for 1 hour in a 10% nitric acid solution at ambient temperature. This allows an identical starting state for all the tests. The temperature of the test is thermostatted at 20° C.±2° C.

(29) The protocol applied comprises the following three steps: a) monitoring of the rest potential of the working electrode (304L) in the sulfonic acid additivated according to the process of the present invention, that is to say measurement of the potential of the material in the solution as a function of time, for 30 minutes, b) immersion of the three-electrode system in a standard (i.e. non-additivated) sulfonic acid solution, then application to the working electrode of a current of −800 μA.Math.cm.sup.−2 for 1 minute in order to depassivate the material artificially by fixing the potential thereof in the corrosion range, c) immersion of the three-electrode system again in the sulfonic acid solution additivated according to the process of the present invention, and monitoring again of the rest potential of the working electrode, until stabilization thereof.
Results of the Validation Test

(30) In the case of a standard, that is to say non-additivated, methanesulfonic acid in solution at 70% by weight in water, after application of an amount of current of −800 μA.Math.cm.sup.−2, the potential of the working electrode (test specimen of 304L stainless steel) drops to around −350 mV, which corresponds to the passing of the 304L stainless steel into the active state. When the application of the current is stopped, the potential of the material remains virtually at the same level and does not rise back up. The 304L stainless steel remains in the active state and corrodes.

(31) The behaviour is completely different in a solution at 70% by weight in water of a nitrite-additivated methanesulfonic acid.

(32) A rest potential of the 304L stainless steel of about 750 mV after 30 minutes is first of all noted. During the application of the current of −800 μA.Math.cm.sup.−2, the potential of the material drops to around −200 mV (passing of the 304L stainless steel into the active state). When the application of the current is stopped, the potential of the material rises back up very rapidly. It is 780 mV after 2 hours of monitoring the potential and a total absence of corrosion is noted.

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