JPS6353282A - Production of ceric nitrate solution - Google Patents

Abstract

PURPOSE:To produce an oxidizing agent made of a soln. contg. ceric nitrate and nitric acid but not contg. ammonium ions by filling an electrolytic cell provided with an ion exchange membrane as a diaphragm with a soln. contg. cerous nitrate and nitric acid as an anolyte and an electrolyte soln. as a catholyte and by carrying out electrolytic oxidation. CONSTITUTION:An electrolytic cell 6 is divided into an anode chamber and a cathode chamber with an ion exchange membrane 1. A cation exchange membrane contg. fluorine, an anion exchange membrane or a combination of them is used as the membrane 1. The anode chamber is filled with a soln. contg. 0.1-10.0mol/l (expressed in terms of cerium) cerous nitrate and 0.5-10mol/l nitric acid as an anolyte, the cathode chamber is filled with an aq. soln. of an electrolyte such as nitric acid or sulfuric acid as a catholyte and electrolysis is carried out with PbO2 or Ir oxide coated Ti or the like as the anode 2 and the Ti, stainless steel or the like as the cathode 3. By the electrolysis, a soln. contg. ceric nitrate and nitric acid but not contg. ammonium ions is produced in the anode chamber. The soln. is used as a superior oxidizing agent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a process for preparing a nitric acid solution of ceric nitrate, which is an effective oxidizing agent and does not contain ammonium ions. The solution is widely used as an oxidizing agent in the field of organic synthesis, such as oxidation of secondary hydroxyl groups, ring opening of cycloalkanones, and carbonylation of oximes.

[Prior Art] Salts containing t7trium and their solutions have conventionally been widely used as oxidizing agents in the field of organic synthesis, such as the oxidation of diabsorbed FIIG, ring opening of cycloalkanones, and carbonylation of oximes. There is. (For example, University λIS Co., Ltd., Journal of the Society of Organic Synthetic Chemistry, Vol. 40, No. 12, p. 1171 (19
82)) As a commonly used tertiary salt, tertiary sulfate is
Cerium Ce (804)2, ceric ammonium nitrate (NH4)2 [Cc (NO3)6]
, per JIM cerium 1-12 Ce (C104
) 6 etc. are known.

Industrially, when a ceric compound is oxidized using a ceric salt, ceric is reduced to ceric, so
It is necessary to recover and oxidize this and convert it into ceric for reuse. Therefore, the oxidation reaction process of the organic compound and the process of electrochemically oxidizing and regenerating the recovered ceric to ceric are performed. A combination of indirect electrolysis methods is often used.

[Problems to be solved by the invention] However, the indirect 'r' caused by the aforementioned cerium n2
Each solution method had its drawbacks as described below.

When carrying out an oxidation reaction using a ceric sulfate solution, the solubility of the ceric sulfate produced in the reaction is relatively low. I have no choice but to set it low. Therefore, the reaction rate of the oxidation reaction using such a low concentration ceric 5A acid solution becomes slow and the reaction time becomes long. In addition, if the cerium concentration is low, 7
In the case of electrolytically oxidizing the primary ttrium ions to be regenerated into ceric ions, an overvoltage builds up at the anode, resulting in an increase in the electrolytic voltage and a more active oxygen-generating electrode reaction due to water decomposition. This causes a decrease in the current efficiency of ceric ion production.

Furthermore, reactions using low-abundance ceric ion solutions have the disadvantage that the amount of effective ceric ions D per unit volume of the solution is small, requiring large reaction vessels and incidental equipment. This makes it difficult to industrialize the oxidation reaction process using ceric sulfate.

Further, when the oxidation reaction is carried out using a ceric ammonium nitrate solution, the solubility in water is high, and the above-mentioned difficulties due to the concentration of ceric ions can be overcome.

However, the cerium source is ammonium and cerium nitrate, and in a process that combines the oxidation reaction process of organic compounds and the regeneration process of ceric by electrolysis, nitrate ions and ammonium ions are complicated in electrolytic oxidation. This has caused various problems for industrialization. In other words, nitrate ions are reduced to nitrite ions and ammonium ions at the cathode by electrolysis,
The concentration of ammonium ions and the like increases, and the cJ degree of nitrate and hydrogen ions decreases, and in extreme cases, hydrolysis occurs.

Along with this complicated behavior, the ability of the ceric salt solution as an oxidizing agent also changes, so settings such as reaction conditions must be changed, and in actual operation, periodic changes in the liquid composition are required. Analysis and adjustment, and in some cases, the need to replace the liquid may become necessary. In addition, anodic reactions involving ammonium ions other than the oxidation of ceric ions lead to a decrease in the current efficiency for producing the desired ceric ions,
Electrode deterioration also occurs in a more complex and serious manner.

When ceric perchlorate salt, which is known as another cerium source, is used, it is expensive and dangerous, and there are problems in handling from the viewpoint of corrosion, making it unsuitable for industrialization.

Although salts containing ceric and their solutions are unique and excellent oxidizing agents in fields such as paid synthesis, conventional methods have the above-mentioned drawbacks and cannot be used on an industrial scale. implementation has become extremely difficult.

[Means for solving the problem] The present inventors believe that the disadvantages of the conventional oxidation reaction using a salt containing ceric salt and its solution are mainly due to the low solubility of the cerium salt, the type of ligand, and the like. Thinking that this is due to the fact that it is a double salt, we investigated cerium salt solutions that do not have such drawbacks.

It is therefore desirable that a nitric acid solution of ceric nitrate that does not contain ammonium ions overcomes the above-mentioned drawbacks, and that
It was found that by electrolyzing a nitric acid solution containing cerous I acid, ammonium ions are generated by the reduction of l1rIR ions at the cathode, and a nitric acid solution of ferric nitrate that does not contain the desired ammonium ions cannot be produced (7). As a result of further vAQ research and study, the present invention was completed.

That is, the present invention converts a nitric acid solution containing ceric nitrate as an anolyte, an electrolyte solution as a catholyte, and an ion exchange membrane as a diaphragm into an electrolytic VEM, thereby producing ceric nitrate containing no ammonium ions. A nitric acid solution is obtained.

The ceric nitrate used in the present invention has the advantage of being relatively inexpensive and easily available as a cerium salt, and the nitric acid solution of ceric nitrate prepared according to the present invention has a high solubility of the cerium salt. Therefore, it can be obtained at a sufficient concentration as an oxidizing agent for industrial organic compounds.

The concentration of cerium in the anolyte used in the present invention may be lower than the solubility of ceric nitrate or ceric nitrate or both when they coexist at the electrolytic oxidation temperature. Has the viscosity increased? Cerium nitrate may interfere with opening operations such as electrolytic oxidation and subsequent reactions. Also, if the concentration is too low, the superiority of cerium nitrate, that is, its high solubility, will not be utilized. It is preferably within the range of 10.0 mol/l.

If the nitric acid concentration in the anolyte used in the present invention is too low, Tiw? Ceric nitrate ions generated by oxidation are unstable and cause hydrolysis, and if the temperature is too high, decomposition of the acid itself and material corrosion will be promoted at high temperatures.
Preferably, the concentration is within the range of 5 to IO, OE/1. Note that the nitric acid concentration here is the concentration as an acid, and does not include the concentration of nitrate ions coming from cerium nitrate.

The ion exchange membrane used in the present invention may be a conventional cation or anion exchange membrane or a combination thereof, but in view of the durability of the membrane, a fluorine-based ion exchange membrane is more preferable. When an ion exchange membrane is not used as a diaphragm, nitrate ions are reduced at the cathode to generate ammonium ions, which not only get mixed into the ceric nitrate solution, but also ceric ions generated at the anode diffuse and form ammonium ions at the cathode. It is reduced to cerous ions again, resulting in a decrease in current efficiency.

The catholyte is not particularly limited as long as it is an electromagnetic liquid, as it is independent from the anolyte through the ion exchange membrane. For example, an aqueous solution of nitric acid, sulfuric acid, etc. can be used. A bipolar reaction is also possible in which a specific reduction reaction is carried out in order to actively utilize .

Electrodes used in electrolysis include oxide-coated types such as titanium coated with lead dioxide, titanium coated with iridium oxide, and titanium coated with platinum-iridium oxide as anodes.
or platinum-plated titanium J3, lead, graphite, glassy carbon, etc., and as the cathode, in addition to the above-mentioned electrodes, an electrode of stainless steel (for example, 5US-3161) or the like is used.

The electrolytic oxidation temperature is determined by taking into consideration the solubility of cerium nitrate in the nitric acid solution used in the present invention, decomposition of the acid itself, corrosion of the material, and reaction eddy current of the oxidation reaction after electrolytic oxidation. Because the concentration of cerous sulfuric acid (lI!1) in the electrolyte can be set high even at relatively low temperatures, conventional electrolytic oxidation of acid solutions containing cerium salts, such as cerous sulfuric acid
Good electrolytic properties can be obtained at a relatively low temperature compared to electrolytic oxidation of cerium using an aqueous sulfuric acid solution.

[Examples] The present invention will be described in detail below using Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 Cerous nitrate (
ce (NO3) 3 ・6 H20) 2400(
1 (equivalent to 5,53 moles - ○C) is charged into an anolyte tank as an anolyte, and 1 mole #! Iil'18
An aqueous solution is charged into a catholyte tank as a catholyte, and each solution is separated by an ion exchange membrane as shown in Figure 1.
Electrolytic oxidation was carried out for 2 hours under the following conditions at a temperature of 50° C. while circulating in a chamber electrolytic cell, and a nitric acid solution of ceric nitrate was used as the anolyte.

Anode: Pt-plated Ti electrode Cathode: 5US3161 Diaphragm: Fluorine-based cation exchange membrane (DuPont, Nafion 423) Current density: 15 A/dm 2 After electrolytic oxidation, determine the concentration of ceric ion 4+ in the anolyte: 1 constant As a result, 1.010t-Lu Ce
/j! The current efficiency at this time was 97.3%. Furthermore, no ammonium ions were detected in the anolyte after electrolytic oxidation.

Example 2 Electrolytic oxidation was carried out under the same conditions as in Example 1 except that the catholyte composition was 1 mol/1 sulfuric acid aqueous solution, and the second anode liquid was i, 007 mol C:, e/1.
1 nitric acid solution of ceric nitrate containing cerium ions
It's 9. The current efficiency at this time was 970%, and no ammonium ions were detected in the anolyte after electrolytic oxidation.

Example 3 Electrolytic oxidation was carried out under the same conditions as in Example 1 except that the electrolytic oxidation temperature was 20° C., and nitric acid of ceric nitrate containing ceric ions of 0.9824+ [Leuce/1] was used as the anolyte. A solution was obtained. The current efficiency at this time is
It was 94.6% despite the low electrolytic oxidation temperature.

No ammonium ions were detected in the anolyte after electrolytic oxidation.

Example 4 Electrolytic oxidation was carried out under the same conditions as in Example 1 except that the diaphragm was an anion exchange membrane. A solution of cerium in nitric acid was obtained.

The current efficiency was 98.2%, and no ammonium ions were detected in the anolyte after electrolytic oxidation.

Example 5 Electrolytic oxidation was carried out under the same conditions as in Example 2 except that the diaphragm was an anion exchange membrane, and the anolyte contained 1020 mol of Ce #! A nitric acid solution of ferric 1111 acid containing ceric ions was prepared.

The current efficiency at this time was 98.3%. Furthermore, no ammonium ions were detected in the anolyte after electrolytic oxidation.

Example 6 Add nitric acid to 500 cc of 5 mol/1 lil' 1M aqueous
Electrolytic oxidation was carried out under the same conditions as in Example 1, except that cerium 2400G (equivalent to 5,53 mol-Ce) was dissolved and used as the anolyte, and the anolyte was 1.008
An Ii1'1 acid solution of ceric nitrate containing 4+ mol-Ce/1 of ceric ions was obtained. The current efficiency at this time was 97.1%, and no ammonium ions were detected in the anolyte after electrolytic oxidation.

Comparative Example 1 Using a cell with the ion exchange membrane removed, electrolytic oxidation was carried out under the same conditions as in Implementation Stop 1, except that the only electrolyte was a solution prepared by dissolving 2400 q of cerous nitrate in 500 cc of a 1 mol/l nitric acid aqueous solution. However, 0.499 mol-Ce /
Although the presence of ceric ions of 1 was observed, the current efficiency at this time was only 48.0%. Additionally, 0.12 mol/l of ammonium ion was detected in the anolyte.

Comparative Example 2 When electrolytic oxidation was carried out under the same conditions as in Example 1 except for the first step using an unglazed diaphragm plate instead of the ion exchange membrane, the electrolytic voltage increased by about 10% and the current efficiency was 4+ 77.0. 0.799 mol in %-〇〇 /j! the second of
Obtain an anolyte containing cerium ions. Furthermore, ammonium ions of 0.03 mol/l were detected in the anolyte after electrolytic oxidation, and the presence of cerium ions due to leakage of the anolyte was observed in the catholyte.

Comparative Example 3 1 mol/1 @ 1969 jl (5,
Cerous sulfate (Ce 2
(804) 3 ・81-120> was added and left for a day and night without stirring to try to dissolve it, but it remained undissolved. Therefore, the undissolved portion was removed by filtration, and the filtrate was used as an anolyte (electrolytic oxidation was performed under the same conditions as in 11), and the anolyte contained 4+ 0.22 mol-Cc/1 of thtrium ions. A sulfuric acid aqueous solution of ceric sulfate was obtained.The current efficiency at this time was only 20.0%.

Comparative Example 4 1-El/fiil'3087 in 500cc of 1M aqueous solution
g (5,53T Nyl-Ce equivalent) of ceric ammonium nitrate ((Nl-14)2 Ce (NO3)6
・Example 1 except that 4l-120) was dissolved and used as an anolyte.
When electrolytic oxidation was performed under the same conditions as 0.920D
An anolyte containing ttrium ions of Leu Ce 4+/1 was obtained. However, compared to before electrolytic oxidation, the ammonium ion 'Q degree in the anolyte has decreased by 0.5%.
The current efficiency was lower than in Example 1, at 89%.

Comparative Example 5 Using a cell with the ion exchange membrane removed, electrolytic oxidation was performed under the same conditions as in Example 1, except that 3087q of ceric ammonium nitrate was dissolved in 500cc of a 1 mol/l nitric acid aqueous solution to prepare an electrolyte. , 4+ 0, 491 mol Ce/j! A solution containing ceric ion Δn of 151% was produced with a current efficiency of 47%. Also, compared to before electrolytic melting, is the electric fl'? Ammonium ion in M =
degree increased by 0.8%.

Comparative example 6 Pure water 500 cckm 2400g (7) Iil'l
When electrolytic oxidation was carried out under the same conditions as in Example 1 except that ceric K was dissolved and used as the anolyte, pale yellowish white precipitates of various sizes were observed on the anode due to hydrolysis of ceric ions. The intended electrolytic oxidation could not be carried out.

[Effects of the Invention] As is clear from the Examples and Comparative Examples, by carrying out the present invention, ceric nitrate, which is useful as an oxidizing agent! 1'I acid solution without containing ammonium ions,
Not only can it be obtained with a high concentration of 2T7 ion, but also it can be put to practical use without causing any complicated changes in the composition of the liquid containing cerium in a process that combines an oxidation reaction step and an electrolytic oxidation step. Understood. Furthermore, by implementing the present invention, it is also possible to save energy in the electrolytic oxidation process.

[Brief explanation of the drawing]

FIG. 1 shows a simplified method of the present invention. Figure 1 ■ Ion exchange membrane ■ Anode ■ Cathode ■ Anolyte tank ■ Cathode tank ■ Electrolytic cell procedure
February 22nd, Commissioner of the Patent Office, Kuro 1) Mr. Akio, 1, Indication of the case, 1985 Patent Application No. 197083, 2, Name of the invention, Process for manufacturing ceric nitrate solution 3, Person making the amendment, Relationship with the case, Patent application 5-1 Koma PJ, Higashi-ku, Osaka, Osaka (462) Nippon Shokubai Kagaku Kogyo Co., Ltd. Representative Director: Jiro Nakajima 4, Agent: 3-11-36 Mita, Minato-ku, Tokyo 108 Nippon Shokubai Kagaku Kogyo Co., Ltd. Tokyo Within the branch (telephone) 0
3-798-7071 (Main) 5. Column of the title of the invention in the application to be amended and Column 6 of the detailed description of the invention in the manifest N. Contents of the amendment (1) The application is corrected as shown in the attached sheet. (2) In the 5th line from the bottom of page 8 of Book 111 of Meiji, “Second
Correct the text ``seium ion'' to ``cerium ion.'' (3) On page 15, line 6 of the specification, rCe (NO
3) Correct “6 J” to “rce (NO3)5”. (4) In MeitlJ, page 15, line 9, rce4+
Correct #j to 4+ "Ce /1". (5) In the first row from the bottom of Ming store No. 15, 4+ [mol Ce /j! Correct J to 4+ "Mole-Ce/1".

Claims (1)

[Scope of Claims] (1) Ceric nitrate containing no ammonium ions is electrolytically oxidized using a nitric acid solution containing cerous nitrate as an anolyte, an electrolyte solution as a catholyte, and an ion exchange membrane as a diaphragm. (2) The method according to claim (1), wherein the concentration of cerium in the anolyte is 0.1 to 10.0 mol/l. (3) The concentration of nitric acid in the anolyte is 0. .5 to 10 mol/l The method according to claim (1) (4) The ion exchange membrane is a fluorine-based cation exchange membrane, a fluorine-based anion exchange membrane, or a combination thereof. Method described in scope (1)