JPS5835271B2 - Production method of hydrogen peroxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing hydrogen peroxide, in which water is produced by electrolytically decomposing an aqueous alkali hydroxide solution and introducing oxygen via a cathode formed as a gas electrode. Forming an aqueous solution containing an alkali oxide and an alkali hydroperoxide.

Hydrogen peroxide is used industrially in various applications, for example as an oxidizing agent or in the production of peroxides derived therefrom.

It is also used, for example, as a bleaching agent in the paper and textile industries.

The production of hydrogen peroxide is known.

Hydrogen peroxide is produced by anodic oxidation of sulfuric acid or ammonium sulfate solution in an electrolytic cell to sulfuric acid peroxide or sulfate salt.

The peroxide sulfuric acid or peroxide sulfate is then hydrolytically decomposed at elevated temperatures.

The hydrogen peroxide thus obtained is separated from the other reaction components by vacuum distillation.

However, this method has the disadvantage that its implementation requires relatively high energy expenditures.

Furthermore, due to the aggressiveness of the medium and the necessarily very high positive anodic potential, the anode must consist of a highly stable material, so that as an anode material it is practically
Only platinum can be used.

Finally, because of the corrosion phenomena due to hydrolytic decomposition in this known process and the necessity of carrying out a subsequent distillative separation from the hot sulfuric acid, the apparatus used when carrying out the process of the invention The drawback is that the materials used must meet high requirements.

Furthermore, processes for producing hydrogen peroxide are known, in which hydrogen peroxide is obtained in addition to quinone during the oxidation of hydroquinone with atmospheric oxygen.

In fact, this method does not have the disadvantages of the electrolytic method mentioned above.

However, this method has the disadvantage that the catalyst that can be used to regenerate hydroquinone by hydrogenating quinone is not sufficiently selective.

In this process, the catalyst is suspended in the reaction solution.

As catalysts, only very precious metals, such as platinum, Raney nickel or others, come into consideration.

Implementation of this method is therefore very expensive.

Moreover, the catalyst suspended in solution must be separated from the process liquid before starting the oxidation of hydroquinone.

As a result, this process is complicated and, since by-products are formed in this process, additionally complicated purification measures are necessary in order to remove the hydrogen peroxide from the reaction process which is carried out in a recycled manner.

Furthermore, processes are known for producing hydrogen peroxide by cathodic reduction of oxygen using an aqueous solution of potassium chloride as electrolyte.

According to this method, the electrolyte containing hydroperoxide ions is removed from the electrolysis, neutralized with hydrochloric acid, and the hydrogen peroxide thus produced is obtained by distillation (E, Berl,
Trans.

Electrochem, Sec, 76 (1939
), see page 359).

However, it became clear that this method was not suitable for practical use.

Hydrogen peroxide production is uneconomical because distillation is highly unproductive due to the presence of chloride ions in the electrolyte.

The object of the invention is to create a process for the preparation of hydrogen peroxide which is simple to implement and which ensures high yields.

Furthermore, the economics of this process should be increased by using readily available starting materials and avoiding the formation of undesirable by-products.

This problem can be solved by adding a concentrated alkaline earth hydroxide solution or an aqueous suspension of alkaline earth hydroxide to an aqueous solution containing an alkali hydroxide and an alkali hydroperoxide, and then At this time, the alkaline earth peroxide produced by the reaction between the alkaline earth hydroxide and the alkali hydroperoxide is separated from the alkali hydroxide contained in the aqueous solution simultaneously produced by precipitation and sawabetsu. The problem is solved by suspending it in water, converting it into alkaline earth carbonate with the introduction of carbon dioxide and simultaneous production of hydrogen peroxide, and then separating and removing the alkaline earth carbonate.

Hydrogen peroxide is then dissolved in water.

In the process according to the invention, therefore, hydrogen peroxide is actually dissolved in water, but is obtained without contamination by by-products.

By distillation, it is possible to adjust the concentration as required in each case.

The energy consumption required to carry out the process according to the invention is low relative to the yield.

A further important advantage is that relatively low-profile workpieces can be used as the electrodes used in this case.

If calcium hydroxide is used as the alkaline earth hydroxide, this embodiment of the process according to the invention has particularly significant economic advantages.

This is because sufficient amounts of calcium hydroxide are used in the form of slaked lime.

A further advantage is that the calcium carbonate obtained when carrying out the process according to the invention can be burned to calcium oxide, in which case carbon dioxide is obtained which can be recycled during carrying out the process according to the invention. This is because it can be used as it is.

The obtained calcium oxide can be suspended in water and recycled as calcium hydroxide for use.

In particular, potassium hydroxide is used as the alkaline compound in the process according to the invention.

This is because potassium peroxide does not crystallize from the cathode solution.

This has the advantage that the cathode remains effective over a relatively long period of time.

Another preferred embodiment of the process according to the invention consists in separating and removing the alkaline earth peroxide and reintroducing the solution containing the alkali hydroxide produced into the electrolytic cell.

It is preferred here that the alkali hydroxide obtained in the process according to the invention can be reused in the process, which further increases the economic efficiency of the process according to the invention.

The course of the method according to the invention will be explained based on the flow sheet shown in the attached drawings.

As is clear from the figure, hydroxide-h IJ is added to the anode chamber 1 of the electrolytic cell 4, which is divided into an anode chamber 1 and a cathode chamber 3 by a diaphragm 2.
Supply an aqueous solution of umum.

Oxygen generated at the anode can be exhausted from the upper part of the anode chamber and introduced into the cathode 5.

Oxygen or air is introduced from above into the cathode 5, which is designed as a gas electrode, with a light excess.

Unconsumed oxygen or air is exhausted again from the top of the cathode chamber.

The potassium hydroperoxide produced during the reaction in the electrolytic cell 4 as well as the potassium hydroxide obtained in this case are led into a cell 6 connected to the electrolytic cell 4 and in which calcium hydroxide is added. Process.

The calcium peroxide produced at this time is separated using a filter 7 and transferred into a reaction vessel 8 which is formed airtight.

On the other hand, f consisting of a calcium hydroxide solution
The liquid is reintroduced into the anode chamber of the electrolytic cell 4.

In reaction vessel 8, peroxide is suspended in water and treated with carbon dioxide.

At that time, calcium peroxide changes to calcium carbonate.

The suspension is then separated by filtration using a filter 9 placed in the reaction vessel 8.

This tear fluid is an aqueous solution of hydrogen peroxide produced during this process.

If necessary, it can be concentrated by one distillation that is not shown in the one-step diagram.

Furthermore, it is also possible to combust the calcium carbonate remaining as a residue during filtration into calcium oxide, which is likewise not shown in the drawings; carbon dioxide is then liberated.

The calcium oxide and carbon dioxide obtained can be used again in carrying out the process according to the invention.

EXAMPLE To produce hydrogen peroxide, an electrolytic cell is used which is subdivided into an anode compartment and a cathode compartment by a membrane made of porous polyvinyl chloride.

The surface area of the electrode is 50.

The charge of electrolyte through the electrolytic cell is 401 liquid per square meter of electrode surface and every hour.

A potassium hydroxide solution with a concentration of 4 molar is used as the electrolyte, and when introduced into the anode chamber, the solution in the cathode chamber and the solution present in the anode chamber are mixed in an amount corresponding to the charged amount through the diaphragm. A level difference is formed that flows into the cathode chamber.

The gap between the anode and the cathode is adjusted to 2.4 square meters, thus resulting in a current density corresponding to approximately 2000 amperes per square meter of electrode surface.

Oxygen generated at the graphite anode is transported to the upper part of the anode chamber.

The cathode - the active material of which consists of activated carbon combined with a synthetic resin in a quality suitable for the production of hydrogen peroxide - carries oxygen with an excess of 0.1 atmosphere EE (gauge pressure) to the electrode. Converted to the unit square meter of the surface is '-'1
Delivered in a quantity corresponding to 250 liters.

This is 1.5 times the amount that could be theoretically consumed.

The excess oxygen is used to enhance the mixing of the solution in the cathode chamber and the heat supply from the solution in the cooling cord through which the water flows.

The temperature in the cathode chamber is then adjusted to between 20 and 25 DEG C., thereby further limiting the spontaneous decomposition of the hydrogen peroxide.

The temperature in the anode chamber is adjusted to 50°C.

An aqueous suspension of calcium hydroxide is added in a substoichiometric amount to the electrolyte removed from the cathode chamber, which contains potassium hydroxide and potassium hydroperoxide.

The amount of calcium hydroxide required for this purpose is calculated as follows: per square meter of electrode surface and per hour.
It weighs 78 kg.

A precipitate of calcium peroxide, which still contains a small amount of calcium hydroxide, is obtained.

The amount of calcium peroxide based on the flowing stream corresponds to a utilization of 90% of the theoretically possible amount.

The 4-molar potassium hydroxide solution separated from the precipitate and reformed is fed back to the anode compartment of the electrolysis chamber.

Calcium peroxide obtained as a residue during filtration is
The electrode surface is suspended in a pressurized airtight container with approximately 20 parts of water per square meter of electrode surface per hour, and the suspension is heated to 7 atmospheres (gauge pressure) using carbon dioxide gas.
Pressurize to .

The calcium peroxide and the calcium hydroxide present in small amounts are thereby converted into calcium carbonate, and the suspension is then filtered.

R-Liquid is a diluted solution of 5% by weight hydrogen peroxide in water.

The calcium carbonate obtained during filtration as a residue is discarded.

The amount of hydrogen peroxide produced was 82% yield for the flow used.
Corresponds to %.

[Brief explanation of the drawing]

A flow sheet of the method of the present invention is shown, and the symbols in the figure have the following meanings. 1...Anode chamber, 2...Diaphragm, 3...
...Cathode chamber, 4...Electrolytic cell, 5...
Cathode, 6... Tank, 7... Filter, 8... Reaction vessel, and 9... Swelling device.

Claims (1)

[Claims] 1. Peroxidation by forming an aqueous solution containing an alkali hydroxide and an alkali hydroperoxide by electrolytic decomposition of an aqueous alkali hydroxide solution and introducing oxygen via a cathode formed as a gas electrode. In the method for producing hydrogen, a concentrated alkaline earth hydroxide solution, a suspension of alkaline earth hydroxide in water, or a solid alkaline earth hydroxide or alkaline earth oxide is added to the aqueous solution containing alkali hydroxide and alkali hydroperoxide. and then separating the alkaline earth peroxide formed by the reaction between the alkaline earth hydroxide and the alkali hydroperoxide from the alkali hydroxide present in the aqueous solution by precipitation and separation,
Hydrogen peroxide is then suspended in water and transformed into alkaline earth carbonate with the simultaneous production of hydrogen peroxide by introducing carbon dioxide, and then the alkaline earth carbonate is separated and removed. Manufacturing method. 2. The method according to claim 1, wherein potassium hydroxide is used as the alkali hydroxide. 3. The method according to claim 1 or 2, wherein calcium oxide or calcium hydroxide is used for the precipitation of alkaline earth peroxide. 4. The method according to claim 1, 2 or 3, wherein the alkali hydroxide-containing solution formed by separation and removal of the alkaline earth peroxide is reintroduced into the electrolytic cell. 5 Claims 1 and 2, in which oxygen generated at the anode of the electrolytic cell is used as part of the oxygen supplied to the cathode,
The method according to paragraph 3 or 4.