JP2017181121A - Activity evaluation method for metallic sodium dispersoid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an activity evaluation method capable of easily and objectively determining, through pH measurement, whether a metallic sodium dispersoid has decreased in activity.SOLUTION: An activity evaluation method for a metallic sodium dispersoid includes: (1) a mixing process of mixing the metallic sodium dispersoid and water; (2) a separating process of separating a non-aqueous solvent layer after adding a non-aqueous solvent to the mixed liquid after an adding process and agitating them; (3) a diluting process of diluting a water layer after the separating process with refined water; (4) a measuring process of measuring a pH value of the water layer after the diluting process; and (5) an evaluation process of evaluating activity of the metallic sodium dispersoid based upon the pH value measured in the measuring process. In the evaluation process, it is determined that the metallic sodium dispersoid has high activity when the pH value measured in the measuring process is equal to or larger than a predetermined value or has low activity when less than the predetermined value.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an activity evaluation method that can easily determine the level of activity of a metal sodium dispersion used in a chemical reaction of an organic compound by measuring pH.

  Metallic sodium is a kind of alkali metal that is solid at normal temperature and pressure, but reacts violently with water or oxygen. For this reason, it is normally stored in a state immersed in a non-aqueous solvent such as white kerosene or trans oil. Dispersion (called metal sodium dispersion or sodium dispersion) in which metallic sodium is refined (average particle size 1-30 μm) and surface area is increased and dispersed in a non-aqueous solvent synthesizes or decomposes organic compounds In some cases, it is used as a reactant.

  For example, in a detoxification treatment for treating a contaminant containing an organic halogen compound such as polychlorinated biphenyl (PCB), a metal sodium dispersion is used when decomposing PCB. In this case, by contacting PCB or a solvent containing PCB with the metal sodium dispersion, a dehalogenation reaction occurs in which PCB is decomposed by reacting PCB with metal sodium.

  In such a PCB dehalogenation treatment using a sodium metal dispersion, the PCB must be treated until it reaches a predetermined residual concentration or less, so a metal sodium dispersion excellent in reactivity with the PCB is required. Here, the smaller the particle diameter of the metallic sodium, the higher the reactivity of the metallic sodium, but the metallic sodium particles in the non-aqueous solvent tend to aggregate and the dispersibility is lowered.

  When white kerosene is used as a dispersion medium, a dispersion aid such as stearic acid may be used because the dispersion stability of metal sodium particles tends to be low. However, such a dispersion aid becomes an impurity in the separation and recovery of the reaction product, and has high reactivity with water and high flammability. As a metallic sodium dispersion that solves such a problem, Patent Document 1 discloses a metallic sodium dispersion dispersed in trans-oil. The metallic sodium dispersion disclosed in Patent Document 1 is considered to be very stable with respect to water and has high dispersion stability of metallic sodium particles without adding a dispersion aid.

  As a method that can easily and efficiently produce an alkali metal dispersion, which conventionally requires a large apparatus and power, with a small and simple apparatus, Patent Document 2 is heated and melted in an inert solvent. Disclosed is a production method for producing an alkali metal dispersion by passing an alkali metal through a swirl flow homogenizer under pressure. According to the production method of Patent Document 3, a sodium liquid dispersion having an average particle size of about 2 to 5 μm is obtained using trans oil or kerosene as a dispersion medium (Examples 1 to 4).

JP-A-10-110205 JP-A-9-209006

  If the sodium metal dispersion container is observed with the naked eye and the metal sodium particles are aggregated, it can be expected that the metal sodium dispersion has deteriorated and the activity has decreased. However, even when aggregation of metallic sodium particles is not observed, the target product cannot be obtained in the chemical reaction, the yield of the product is lower than the theoretical value, or other experimental conditions are Even if they are the same, the experimental results may vary. In particular, when a metal sodium dispersion with greatly reduced activity is used, the researcher may not be able to decompose the target substance that should be decomposed or produce a product that can be synthesized. There is a risk of misunderstanding that it cannot be performed.

  It is an object of the present invention to provide an activity evaluation method that can easily and objectively determine whether or not the activity of a metallic sodium dispersion is reduced.

  The present inventor has found that in chemical reactions using metal sodium dispersion, the yield of reaction products is reduced or the experimental results vary because the activity of the metal sodium dispersion is reduced. I expected that. And this inventor repeated earnest examination about the method for determining easily whether the activity of a metal sodium dispersion has fallen.

  As a result, the present inventor added water to the metal sodium dispersion to change all the metal sodium into sodium hydroxide (NaOH), and then changed the non-aqueous solvent that is the dispersion medium of the metal sodium particles into the aqueous layer. It was found that the activity of the metal sodium dispersion can be evaluated by a simple method of removing the aqueous solution and measuring the pH of the aqueous layer, and the present invention has been completed.

Specifically, the present invention
A method for evaluating the activity of a metallic sodium dispersion,
A mixing step of mixing the metal sodium dispersion and water;
A separation step of separating the nonaqueous solvent layer after adding and stirring the nonaqueous solvent to the mixed solution after the addition step;
A dilution step of diluting the aqueous layer after the separation step with purified water;
A measurement step of measuring the pH value of the aqueous layer after the dilution step;
An evaluation step of evaluating the activity of the metal sodium dispersion based on the pH value measured in the measurement step,
In the evaluation step,
When the pH value measured in the measurement step is not less than the value calculated by the following mathematical formula, it is determined that the activity of the metal sodium dispersion is high,
When the pH value measured in the measurement step is less than the value calculated by the following mathematical formula, it is determined that the activity of the metal sodium dispersion is low.
The present invention relates to an activity evaluation method.

Where B = log A,
A = (dilution ratio in the dilution step) x (amount of mixed water in the mixing step (g) ÷ amount of metal sodium dispersion in the mixing step (g)),
It is.

Metal sodium particles contained in the metal sodium dispersion change to NaOH when reacted with water, and change to sodium oxide (Na ₂ O) when reacted with oxygen. When Na ₂ O also reacts with water, it changes to NaOH, so even if the metal sodium dispersion reacts with moisture or oxygen in the air and the activity decreases, the same amount of water is added to adjust the pH of the aqueous layer. If measured, it should theoretically have the same pH value as that of a highly active sodium metal dispersion.

  However, when the inventors of the present invention add the same amount of water and measure the pH of the aqueous layer, the reason is unknown, but in the case of a highly active metallic sodium dispersion, the pH of the aqueous layer exceeds the threshold, and the activity is increased. In the case of a metal sodium dispersion having a low pH, a phenomenon was observed in which the pH of the aqueous layer was below the threshold.

  According to the present invention, it is possible to easily and objectively determine deterioration of a metallic sodium dispersion, which has been impossible in the past.

The graph showing the peak area of the monomer and dimer of 4-tert-butylpyridine is shown. About the metal dispersion of (1)-(5), the graph which plotted pH value on the vertical axis | shaft and B value on the horizontal axis | shaft is shown.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate. The present invention is not limited to the following description.

(Confirmation of metal sodium dispersion activity)
The following four types of metal sodium dispersions were used. These metallic sodium dispersions use normal paraffin as a dispersion medium, add metallic sodium to 25 wt%, and stir the metallic sodium by heating it to a temperature above the melting point of sodium. The dispersion was prepared as a sodium dispersion having a weight average particle diameter of 5 μm or less. In addition, (1) to (4) were produced in the same lot, and only (5) was produced in another lot.
(1) Metal sodium dispersion used for 4 months after production
(2) Metal sodium dispersion used for 3 months after production
(3) Metal sodium dispersion stored for 4 months after production
(4) Metal sodium dispersion immediately after production
(5) Metal sodium dispersion just after production (a lot different from (4))

  270 mg (2 mmol) of 4-tert-butylpyridine (4- (1,1-dimethylethyl) pyridine) was mixed with 4 mL of dehydrated tetrahydrofuran (THF), and this was mixed with 25 wt% metal sodium dispersion ((1) to (Metal sodium dispersion of (5)) was added so that the metal sodium was 2 mmol, and reacted at room temperature for 5 hours. After completion of the reaction, 25 μL of each mixed solution was collected in a microtube, and 0.5 mL of purified water was added to deactivate the metallic sodium remaining in the mixed solution. Thereafter, 500 μL of ethyl acetate was added to the microtube, shaken by hand and stirred, and then allowed to stand at room temperature until it was separated into two layers. 1 μL of the ethyl acetate layer was collected in a microsyringe and injected into a gas chromatograph mass spectrometer (GC / MS, manufactured by Shimadzu Corporation, model number QP5050), and the peak areas of the monomer and multimer were measured.

  FIG. 1 is a graph showing the peak areas of the monomer and dimer of 4-tert-butylpyridine for the mixed liquids (1) to (5). In (1) to (3), the peak area of the monomer was much higher than the peak area of the dimer, but in (4) and (5), the peak area of the dimer was reversed. Was higher than the peak area of the monomer. That is, it was confirmed that the monomer was changed to a dimer.

  From FIG. 1, it was confirmed that among the five metallic sodium dispersions, (4) and (5) had high activity and (1) to (3) had low activity.

[Test example]
(Mixing process)
While stirring a 200 ml glass beaker containing 100 ml of pure water with a magnetic stirrer, 0.5 g of metal sodium dispersion (1) to (5) (0.125 g as metal sodium) was collected and added to water. All the metallic sodium was changed to NaOH, and the metallic sodium dispersion was deactivated.

(Separation process)
The mixed solution in the beaker (mixed solution of non-aqueous solvent as dispersion medium and aqueous solution containing NaOH) was transferred to a separatory funnel, and 10 mL of n-hexane (JIS special grade) was further added as a non-aqueous solvent. The separatory funnel was shaken, and the lower aqueous layer was extracted. The extracted aqueous layer was transferred to another separatory funnel, and 10 mL of n-hexane was added again as a non-aqueous solvent, and the separatory funnel was shaken. The lower aqueous layer was extracted and collected in a beaker.

(Dilution process)
1 mL of the aqueous layer collected in the beaker was collected in a 200 ml beaker and diluted 100 times with purified water.

(Measurement process)
The pH of the diluted aqueous layer was measured using a pH meter (manufactured by Horiba, Ltd., model number D-72AL).

  The pH of each of the metal sodium dispersions (1) to (5) was measured once. Table 1 shows the pH value of each metallic sodium dispersion: a) the amount of water actually mixed with the metallic sodium dispersion in the mixing step; b) the metallic sodium dispersion actually collected in the mixing step (in Table 1) C) pH measured value (average value); and d) Theoretical pH value calculated from the actual amount of water and the metal sodium dispersion mass in the mixing step.

(Evaluation process)
Here, for the metal dispersions of (1) to (5), A = (dilution ratio in the dilution step) × (mixed water amount in the mixing step (g) ÷ metal sodium dispersion amount in the mixing step (g)) B = log A was calculated. FIG. 2 shows a graph in which the pH measurement value is plotted on the vertical axis and the B value is plotted on the horizontal axis.

  The regression line calculated from the five plots was y = -0.9x + 14.413. In the metal sodium dispersions (4) and (5) confirmed to have high activity, the measured pH value (actual value) in the measurement step was not less than the pH value calculated by the regression line. On the other hand, the metal sodium dispersions (1) to (3) that were confirmed to have low activity had pH measurement values (actual measurement values) in the measurement step that were less than the pH value calculated by the regression line.

  As described above, the activity evaluation method of the present invention objectively evaluates a metal sodium dispersion ((4) and (5)), which has been confirmed to have high activity, as “high activity” based on the pH value. It was possible. Similarly, the activity evaluation method of the present invention objectively evaluates a metal sodium dispersion ((1) to (3)) that has been confirmed to have low activity as “low activity” based on the pH value. Was possible.

  The activity evaluation method of the present invention is useful in the field of organic chemistry using a metal sodium dispersion.

Claims (1)

A method for evaluating the activity of a metallic sodium dispersion,
A mixing step of mixing the metal sodium dispersion and water;
A separation step of separating the nonaqueous solvent layer after adding and stirring the nonaqueous solvent to the mixed solution after the addition step;
A dilution step of diluting the aqueous layer after the separation step with purified water;
A measurement step of measuring the pH value of the aqueous layer after the dilution step;
An evaluation step of evaluating the activity of the metal sodium dispersion based on the pH value measured in the measurement step,
In the evaluation step,
When the pH value measured in the measurement step is not less than the value calculated by the following mathematical formula, it is determined that the activity of the metal sodium dispersion is high,
When the pH value measured in the measurement step is less than the value calculated by the following mathematical formula, it is determined that the activity of the metal sodium dispersion is low.
Activity evaluation method.
Where B = log A,
A = (dilution ratio in the dilution step) x (amount of mixed water in the mixing step (g) ÷ amount of metal sodium dispersion in the mixing step (g)),
It is.