JPH085834B2 - Method for producing 2-chloropropionaldehyde - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to the following reaction formula (1) CH ₂ = CHCl + CO + H ₂ → CH ₃ -CHCl-CHO (1), vinyl chloride, carbon monoxide and The present invention relates to a method for producing 2-chloropropionaldehyde using hydrogen as a raw material. 2-Chloropropionaldehyde can be used as a useful intermediate for chemicals and agricultural medicine.

(Prior Art) Vinyl chloride, carbon monoxide and hydrogen as raw materials 2
Methods for producing chloropropionaldehyde are known, for example, French Patent No. 1,397,779 and HELVETICA CHIMICAACTA, Volume 48, Vol.
No., pp. 1151-1157. All of these methods use cobalt carbonyl as a catalyst, for example,
According to said French patent 1,397,779 the reaction temperature 110
After 90 minutes of reaction at 200 ° C and a reaction pressure of 200 atm, vinyl chloride conversion was 57.4% and 2-chloropropionaldehyde selectivity was 86.2%.

(Problems to be solved by the invention) However, in these methods using cobalt carbonyl as a catalyst, the catalytic activity per cobalt is extremely low, which requires a large amount of cobalt carbonyl and a high reaction pressure of 160 to 200 atm. In addition, the reaction temperature 75 ~ 125 ℃
The method is such that the reaction is carried out for 90 to 120 minutes under heat. The target product, 2-chloropropionaldehyde, is a thermally unstable substance, and under such reaction temperature and reaction time, in order to reduce the reaction yield, a considerable proportion is consumed in the sequential reaction. This method is not reproducible, and hydrogen chloride is by-produced by this sequential reaction or other side reaction, which violently corrodes the material of the reactor and reacts with the cobalt carbonyl catalyst to form cobalt chloride. In addition, there is a problem in that the reuse of the catalyst is also hindered.

(Means and Actions for Solving Problems) The present inventors have conducted detailed research for solving these problems. As a result, when vinyl chloride, carbon monoxide, and hydrogen are reacted in the presence of a rhodium compound and a base, the reaction proceeds at a lower temperature and a lower pressure than in the conventional method using a cobalt carbonyl catalyst, and the reaction is sufficient. Although it has been found that selectivity to the desired product can be obtained, further detailed study on this method revealed that
Using a solvent insoluble or hardly soluble in water as a reaction solvent,
It was found that if the reaction is carried out under extraction with an aqueous medium having a pH value in the range of 0.5 to 7 at 25 ° C, the reaction can proceed more efficiently and at the same time, the reaction can be continued for a long time without lowering the catalytic activity. The present invention has been completed.

That is, the present invention, in the presence of a rhodium compound, a base and a solvent, vinyl chloride, carbon monoxide and hydrogen are reacted to produce 2-chloropropionaldehyde, insoluble or sparingly soluble solvent in water as a solvent Used,
A method for producing 2-chloropropionaldehyde, characterized in that the reaction is carried out under extraction with an aqueous medium having a pH value in the range of 0.5 to 7 at 25 ° C.

The base described here generally means a Lewis base containing a periodic group B element such as nitrogen, phosphorus or arsenic. In the method of the present invention, a trivalent organic phosphorus compound or an oxide of a trivalent organic phosphorus compound is particularly preferable as the base. The trivalent organic phosphorus compound or the oxide of the trivalent organic phosphorus compound preferably used in the method of the present invention is exemplified as follows. That is, as the trivalent organic phosphorus compound, P (R ¹ R ² R ³ ) (wherein P represents a phosphorus atom, R ¹ , R ² and R ³ are the same or different alkyls, respectively) A trivalent organic phosphorus compound represented by aryl, cycloalkyl, alkoxy, aryloxy or cycloalkoxy group is shown, and specific examples thereof include trimethylphosphine, triethylphosphine, tripropylphosphine, tributylphosphine and trioctylphosphine. , Phosphines such as triphenylphosphine, tricyclohexylphosphine, and tribenzylphosphine, trimethylphosphite, triethylphosphite, tripropylphosphite, tributylphosphite, trioctylphosphite, triphenylphosphite, tricyclohexylphosphite, Phosphites such as revenge Le phosphite, and the like.

In addition to the compounds represented by the above general formula P ((R ¹ R ² R ³ ), special phosphines include diphosphines such as bisdiphenylphosphinomethane and bisphenylphosphinoethane, and crosslinked polystyrene. Bound phosphines and the like are also preferably used.

Further, as an oxide of a trivalent organic phosphorus compound, an alkylphosphine oxide such as triethylphosphine oxide, tributylphosphine oxide or trioctylphosphine oxide, an arylphosphine oxide such as triphenylphosphine oxide or tritolylphosphine oxide, or an alkyl group and an aryl Examples thereof include alkylarylphosphine oxide having a group. In addition to these, alkyl or aryl phosphite oxides such as triethyl phosphite oxide, tributyl phosphite oxide, and triphenyl phosphite oxide, and alkylaryl phosphite oxides having an alkyl group and an aryl group together can also be used. it can. Furthermore, oxides of polydentate phosphines such as bis-1,2-diphenylphosphinomethanedioxide can also be used.

Examples of the rhodium compound used in the method of the present invention include rhodium oxide, mineral acid salt, organic acid salt, and rhodium complex compound. Examples of these are rhodium oxide, rhodium chloride, rhodium bromide, rhodium iodide, rhodium nitrate,
Rhodium sulfate, rhodium acetate, triacetylacetonato rhodium, dicarbonyl acetylacetonato rhodium, dodecacarbonyl tetrarhodium, hexadecacarbonyl hexalodium, etc. are mentioned, and in addition to these, complex compounds with rhodium and other bases can be mentioned. Those formed are also preferably used. The base may be a base preferably used in the method of the present invention, but may be another base. Examples of these include hydridocarbonyltristriphenylphosphine rhodium [RhH
(CO) (PPh _{3) 3],} nitro silt list Li triphenylphosphine rhodium _{[Rh (NO) (PPh 3)} 3 ], .eta. cyclopentadienyl bis triphenylphosphine rhodium [Rh
(C ₅ H ₅ ) (PPh ₃ ) ₂ ], chlorotris (toniphenylphosphine) rhodium [RhCl (PPh ₃ ) ₃ ] and the like.

In the method of the present invention, the rhodium compound is in an amount corresponding to 0.0001 to 1000 milligram atom, preferably 0.001 to 100 milligram atom, as rhodium atom per liter of water-insoluble or sparingly soluble solvent in the reaction system. Used in. The base used in the method of the present invention is used in an amount of 0.1 to 500 mol, preferably 0.5 to 100 mol, per 1 gram atom of rhodium.

The method of the present invention is carried out in the presence of a solvent which is insoluble or sparingly soluble in water. The water-insoluble or sparingly-soluble solvent described here has a solubility in the aqueous phase of 5% by volume under the opposite conditions.
Hereinafter, particularly preferably, a solvent having a solubility of 0.5% by volume or less is meant. Among these solvents, those that do not adversely affect the reaction are preferably used. Hydrocarbons are particularly preferable as such a solvent. In particular,
Hexane, heptane, octane, nonane, saturated hydrocarbons such as decane, benzene, toluene, aromatic hydrocarbons such as xylene are preferably used, and also industrially obtained as a mixture of hydrocarbons ligroin, kerosene, Light oil, diesel oil, etc. are also included in these examples. Also, various halogenated hydrocarbons such as dichloromethane, o-dichlorobenzene, p-chlorotoluene, vinyl chloride and the like are preferable. Particularly, since vinyl chloride is one of the raw materials of this reaction, the process is simplified. Are particularly preferred solvents. In addition, dipropyl ether,
Examples of preferable solvents include ethers such as dibutyl ether, ketones such as diisobutyl ketone and holone, esters such as butyl butyrate and butyl benzoate, and carbonates such as diethyl carbonate.

In the method of the present invention, the reaction is carried out at a pH value of 25 ° C.
Performed under extraction with an aqueous medium in the range 0.5-7. twenty five
Extraction with an aqueous medium having a pH value in the range of 0.5 to 7 at 25 ° C means that reaction products such as 2-chloropropionaldehyde are reacted with the aqueous medium having a pH value in the range of 0.5 to 7 at 25 ° C during the reaction. It means that the reaction is performed while performing the extraction operation. However, in some cases, the method of the present invention also includes a method in which this operation is carried out immediately after the reaction, and the solvent containing the catalyst component after extraction, which is insoluble or hardly soluble in water, is subjected to the reaction again. By adopting such a method, the reaction results were improved and the catalyst could be reused continuously.

The pH value at 25 ° C. used in the method of the present invention is 0.5 to
The aqueous medium in the range of 7 is adjusted so that the pH value at 25 ° C is in the range of 0.5 to 7 by dissolving various acids, salts or both in a solution using water as a solvent. Means a solution. Preferred examples of such a solution include aqueous solutions of various acids, aqueous solutions of salts of these acids and bases, or buffer solutions. As such an acid, an acid having a pKa in the range of 0.5 to 7 is preferable, and a carboxylic acid is particularly preferable. As examples of these carboxylic acids, specifically, formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, heptanoic acid, acrylic acid, methacrylic acid, crotonic acid, oxalic acid, malonic acid, methylmalonic acid, succinic acid,
Adipic acid, maleic acid, fumaric acid, aliphatic saturated or unsaturated mono- or polycarboxylic acids such as 1,2,3-propanetricarboxylic acid, and benzoic acid, toluic acid, phthalic acid, isophthalic acid, trimellitic acid, Pyromellitic acid,
Examples thereof include monovalent or polyvalent aromatic carboxylic acids such as meritic acid. In addition, halogens, amino groups, carboxylic acids having a substituent such as a hydroxyl group in the alkyl group or aryl group of these carboxylic acids are also preferable, and examples of these include monofluoroacetic acid, difluoroacetic acid, trifluoroacetic acid, monochloroacetic acid, Dichloroacetic acid, trichloroacetic acid,
Halogen-substituted aliphatic carboxylic acids such as monobromoacetic acid, dibromoacetic acid, 2-chloropropionic acid, 3-chloropropionic acid and 2,2-dichloropropionic acid, o-chlorobenzoic acid, m-chlorobenzoic acid, p-chloro benzoic acid,
halogen-substituted aromatic carboxylic acids such as o-fluorobenzoic acid, glycine, sarcosine, alanine, β-alanine,
Amino acids such as 4-aminobutyric acid, valine, serine, aspartic acid, glutamic acid, glycolic acid, lactic acid, 2-hydroxybutyric acid, glyceric acid, malic acid, tartaric acid, citric acid, p-hydroxybenzoic acid, salicylic acid, 2,4- There are hydroxycarboxylic acids such as dihydroxybenzoic acid. In addition, phenylacetic acid, pyruvic acid, anisic acid,
Preferred examples include carboxylic acids having a substituent other than the above, such as o-nitrobenzoic acid and cinnamic acid. Among these carboxylic acids, halogen-substituted aliphatic carboxylic acids and monovalent or polyvalent aromatic carboxylic acids are particularly preferably used in the method of the present invention. In the method of the present invention, as acids other than carboxylic acids, phosphoric acid, phosphorous acid, and various phosphorus oxyacids such as phosphonic acids, phosphonous acids, phosphinic acids, or phosphinic acids are also preferably used. To be Examples of these are methylphosphonic acid, ethylphosphonic acid, phenylphosphonic acid, phenylphosphonous acid, dimethylphosphinic acid, diethylphosphinic acid, diphenylphosphinic acid,
Examples include diphenylphosphinous acid. Furthermore, boric acid, carbonic acid and the like are also included in the examples of preferable acids.

In the method of the present invention, an aqueous solution of a salt composed of these acids and bases is also preferably used. Examples of the base include oxides or hydroxides of alkali metals or alkaline earth metals, and specifically, magnesium oxide, calcium oxide, strontium oxide, lithium hydroxide, sodium hydroxide, potassium hydroxide. , Cesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide and the like. Further, guanidines are also preferable bases, and specifically, various substituted guanidines other than guanidine, for example, methylguanidine and 1,1-dimethylguanidine are exemplified. In addition to these, various ammonium hydroxides, particularly quaternary ammonium hydroxide, are also mentioned as examples of preferable bases, and specific examples thereof include tetramethylammonium hydroxide, tetraethylammonium hydroxide and choline. The salts of these acids and bases can be obtained by mixing them, for example, a method of mixing a carbonate or bicarbonate of an acid with a base, a method of mixing an ammonium salt of a base with an acid, etc. Thus, a method of obtaining the same product obtained by mixing an acid and a base as a result is also included in the scope of the present invention.

The buffer solution in the method of the present invention means a solution having a buffering ability against a factor of varying the pH value, and is usually prepared by dissolving an appropriate combination of an acid, a base and various salts in a solvent. . These buffers have different pH values depending on the target pH value.
It is necessary to select the types of acids and bases that make up the buffer solution, and their concentrations and mixing ratios, and appropriate selection of these will prepare buffer solutions in various pH ranges.
Examples of these are hydrochloric acid-potassium chloride buffer solution (typical pH range: 1 to 2.2), potassium hydrogen phthalate-hydrochloric acid buffer solution (typical pH range: 2.2 to 4.0), potassium hydrogen phthalate-water. Sodium oxide buffer (typical pH range: 4.1 ~
5.9), potassium dihydrogen phosphate-sodium hydroxide buffer solution (typical pH range: 5.8 to 8), and the like. In addition, the type of acid, base or salt that constitutes these buffer solutions can be changed. Various buffer solutions are also mentioned as examples. As an example of these, an aqueous solution containing both the above-mentioned acid and a salt of the acid and a base is particularly preferable. In particular, when a polyvalent acid such as phthalic acid or pyromellitic acid is used, it is possible to form a part of the acid radical in the form of a salt with a base and the rest in the form of a free acid. It is one of the preferable means for allowing a salt to coexist, and examples thereof include lithium hydrogen phthalate, sodium hydrogen phthalate,
Preferred examples include potassium hydrogen phthalate and guanidine hydrogen phthalate. In addition to the polyvalent carboxylic acids described above, examples of acids that can be used in such a method include phosphoric acid and phosphorous acid. In addition, although it is preferable to use an aqueous buffer solution in the method of the present invention, most of the aromatic polycarboxylic acids have low solubility in water. However, by adopting the method as described above, most of the aromatic polycarboxylic acid has good solubility in water, and it becomes possible to form a buffer solution very suitable for the method of the present invention. Examples of these include phthalic acid and pyromellitic acid, as well as isophthalic acid and mellitic acid.
In addition, terephthalic acid and the like, which are not included in the above-mentioned preferable acid examples, are included in the preferable acid examples by this method. The pH value of these buffers usually varies depending on the measurement temperature,
In the method of the present invention, the pH value at 25 ° C. is conveniently represented. In the method of the present invention, among these buffers, an aqueous buffer having a pH value in the range of 0.5 to 7 is preferably used.

Under the extraction with such an aqueous medium, the rhodium compound exhibits high activity for synthesizing 2-chloropropionaldehyde from vinyl chloride and synthesis gas in the presence of the above-mentioned base. Further, 2-chloropropionaldehyde, which is a reaction product, is extracted into an aqueous medium immediately after being produced in the reactor, so that it is easily separated from the organic layer containing vinyl chloride, rhodium and a base as raw materials. Further, in this case, 2-, separated from the raw material vinyl chloride and the catalyst,
The aqueous medium containing chloropropionaldehyde can be prepared by distillation under normal pressure or slightly reduced pressure.
Chloropropionaldehyde can be easily separated. On the other hand, the aqueous medium thus recovered can be reused by removing a part of the aqueous medium and removing foreign ions as a by-product of the reaction or exchanging it with a newly prepared aqueous medium. The method is highly preferred as an industrial method for producing 2-chloropropionaldehyde.

The concentration of these aqueous media is also important in the method of the present invention. When a low-concentration aqueous medium is used, the reaction results similar to those of a high-concentration aqueous medium are obtained in the initial stage,
Usually, the pH value of the aqueous medium decreases as the reaction progresses, and if it deviates from the preferable pH value range, the catalytic activity is impaired. Therefore, it is generally preferable that the concentration of the aqueous medium is high, but it is not preferable in view of handling that the concentration is too high. Usually, the concentration of the acid and the salt constituting the aqueous medium is preferably 0.001 mol to 10 mol per liter of the aqueous medium, and particularly preferably 0.01 mol to 1 mol. Further, the amount of the aqueous medium to be used may be small if the concentration of the aqueous medium is high, and conversely it is preferable to use a large amount if the concentration is low. The concentration and amount of these aqueous media are usually such that the pH value of the aqueous media at the reactor outlet is 0.5.
It is particularly preferable to select it so as to fall within the range of ˜7.
Usually, the amount of the aqueous medium is 1 per liter of reactor volume.
It is preferably in the range of 0.1 to 10 liters per hour.

In the method of the present invention, the reaction is preferably carried out in a continuous reaction apparatus, but at this time, the extraction is carried out in the reactor or in an extractor provided separately from the reactor.

When the extraction is carried out in the reactor, a solvent containing a catalyst component is charged into the reactor, and vinyl chloride as a raw material, carbon monoxide and hydrogen are continuously supplied thereto. The solvent containing the catalyst component can be kept in a certain amount in the reactor and the reaction can be continued without supplying a new catalyst. It is also possible to continuously supply a solvent containing a catalyst component to the reactor and continuously withdraw a portion corresponding to the solvent from the reactor. While carrying out the reaction by such a method, an aqueous medium having a pH value in the range of 0.5 to 7 at 25 ° C. is continuously supplied from above the reactor to extract reaction products such as 2-chloropropionaldehyde into an aqueous phase. Then take it out of the reaction system.

Further, when the extraction is carried out by an extractor provided separately from the reactor, the solvent containing the catalyst component, vinyl chloride, carbon monoxide and hydrogen are continuously supplied to the reactor and the reaction liquid coming out of the reactor is removed. It leads to the reaction liquid supply port provided in the lower part of the extractor. From the top of the extractor, the pH value at 25 ℃ is 0.5-7.
The reaction product such as 2-chloropropionaldehyde is extracted into the aqueous phase by continuously supplying the aqueous medium in the range of 1, while the reaction solution is recycled to the reactor for reuse.

The method of the present invention is usually carried out at a reaction temperature of 20 to 150 ° C. and a reaction pressure of 1 to 200 kg / cm ² gauge, preferably 5 to 150 kg / c.
It is done in the m ² gauge range. The reaction temperature is preferably as low as possible from the viewpoint of the thermal stability of the 2-chloropropionaldehyde produced, and therefore, 20-100 ° C is a particularly preferred temperature range. The mixing molar ratio of carbon monoxide and hydrogen of the raw materials is usually in the range of 10 to 0.1, preferably 4 to 0.2.
Range. Carbon monoxide and hydrogen may be mixed gas containing both components in the above composition ratio, water gas,
A water gas containing methane, a gas inert to the reaction such as nitrogen, or carbon dioxide or water is used. The other raw material, vinyl chloride, is used in the form of gas, liquid, or solution dissolved in the solvent used for the reaction.

(Examples) Hereinafter, the method of the present invention will be described more specifically with reference to Examples.

Example 1 Pressure resistance with a 10-stage impeller and hot water jacket
100kg / cm ² gauge reactor 1 (made of SUS 316L, inner diameter 25mm,
Height 350 mm, actual volume about 170 cm ³ , inside diameter 25 mm, height 1
To a 50 mm stationary separation tank 2), 0.5 mmol of hydridocarbonyltristriphenylphosphine rhodium, 5 mmol of trophenylphosphine and 50 ml of toluene as a reaction solvent were charged, and the reaction temperature was 45 ° C. and the reaction pressure was 75 kg / cm ² Under the conditions of a gauge, from the introduction pipes 4 and 5 provided in the lower part of the reactor, 8.7 g / hr of vinyl chloride, and a mixed gas of carbon monoxide and hydrogen of a molar ratio of 1: 2 about 24 l / hr.
Each hour was supplied continuously. At the same time, an aqueous solution having a pH value of 3.9 at 25 ° C. in which 10 g of potassium hydrogen phthalate was dissolved was supplied from the aqueous medium storage tank 3 at a rate of 150 g / hr from the liquid introduction pipe 6 provided at the upper part of the reactor. A liquid take-out pipe 7 is provided below the stationary separation tank 2 provided at the bottom of the reactor.
Is installed and the aqueous phase consisting of an aqueous solution of potassium hydrogen phthalate containing the reaction product 2-chloropropionaldehyde is continuously supplied from the liquid take-out pipe 7 so that the liquid level in the reactor is kept constant. To the outside of the reactor, while
From the gas extraction pipe 8 provided at the top of the reactor, the reactor 1
A gas containing unreacted vinyl chloride and unreacted carbon monoxide and hydrogen was continuously withdrawn so that the internal pressure was kept constant. It was confirmed that, in addition to potassium hydrogen phthalate, 6.8 g / hour of 2-chloropropionaldehyde, a small amount of chlorine ions, propionate ions, and rhodium at a concentration of 0.1 ppm were present in the aqueous phase.

However, potassium hydrogen phthalate was analyzed by the dry weighing method, 2-chloropropionaldehyde and propionate ion were analyzed by the GC method, chlorine ion was analyzed by the silver nitrate titration method, and rhodium was analyzed by the atomic absorption method.

The reaction was continued for 6 hours in this way, but no substantial change was observed in the catalyst performance even 6 hours after the start of the reaction.

Incidentally, from the aqueous phase, 2-chloropropionaldehyde (about 10% water content) as a reaction product was obtained by applying it to a glass batch distillation apparatus operated at a pressure of 50 mm mercury column and a can temperature of 60 ° C. It was confirmed to be isolated.

Example 2 Instead of potassium hydrogen phthalate in Example 1, 1
P at 25 ° C in which 13 g of dichloroacetic acid was dissolved per liter
The reaction was performed in the same manner except that an aqueous solution having an H value of 1.1 was used. 2-Chloropropionaldehyde was added to the water phase from the liquid take-out pipe 7 every hour for 6 hours after the start of the reaction.
It was confirmed that it was generated at a rate of 4 g.

However, 2-chloropropionaldehyde was analyzed by the GC method.

Example 3 Instead of potassium hydrogen phthalate in Example 1, 5
% Aqueous sodium hydrogen phthalate solution, 10% aqueous sodium hydroxide solution was added as appropriate, and the reaction was performed in the same manner except that an aqueous buffer solution having a pH value of 6.0 at 25 ° C. was used. The water phase from the liquid take-out pipe 7 was kept for 2 hours for 6 hours after the reaction was started.
-It was confirmed that chloropropionaldehyde was produced at a rate of 6.2 g / h.

However, 2-chloropropionaldehyde was analyzed by the GC method.

(Effects of the Invention) By the method of the present invention, 2-chloropropionaldehyde can be produced in high yield at a low temperature and a low pressure as compared with conventional methods, using vinyl chloride, carbon monoxide and hydrogen as raw materials. In particular, the method of the present invention allows the catalyst to be continuously used under higher catalytic activity than ever before.

[Brief description of drawings]

FIG. 1 is a process chart for explaining an embodiment of the present invention. In the figure, 1 is a reactor, 2 is a stationary separation tank, 3 is pH at 25 ° C.
Figure 3 shows an aqueous medium reservoir with values in the range 0.5-7.

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Claims (8)

[Claims] 1. A method of reacting vinyl chloride, carbon monoxide and hydrogen in the presence of a rhodium compound, a base and a solvent to give 2
-When producing chloropropionaldehyde, a solvent insoluble or sparingly soluble in water is used as a solvent, and the reaction is carried out under extraction with an aqueous medium having a pH value in the range of 0.5 to 7 at 25 ° C. A method for producing 2-chloropropionaldehyde. 2. The method according to claim 1, wherein the base is a trivalent organic phosphorus compound or an oxide of a trivalent organic phosphorus compound. 3. The method according to claim 1, wherein the water-insoluble or sparingly-soluble solvent is a hydrocarbon. 4. The method according to claim 1, wherein the water-insoluble or sparingly water-soluble solvent is vinyl chloride. 5. An aqueous medium having a pH value in the range of 0.5 to 7 at 25 ° C. is an aqueous solution of a carboxylic acid or an aqueous solution of a carboxylic acid salt having a pH value in the range of 0.5 to 7 at 25 ° C. The method according to any one of items 1 to 4. 6. The method according to claim 5, wherein the carboxylic acid is a halogen-substituted aliphatic carboxylic acid. 7. The method according to claim 5, wherein the carboxylic acid is a monovalent or polyvalent aromatic carboxylic acid. 8. An aqueous medium having a pH value in the range of 0.5 to 7 at 25 ° C. is an aqueous buffer solution having a pH value in the range of 0.5 to 7 at 25 ° C. The method described.