JPH06340402A - Preparation of chlorine dioxide - Google Patents

Abstract

PURPOSE: To provide the method for producing the chlorine dioxide with a relatively small sized device, conveniently and in a high yield by a momentary reaction.

CONSTITUTION: A soln. containing 0.5-60 wt.% alkali metal chlorate and a sulfuric anhydride in a molecular state are supplied to a reaction column to allow to react momentarily in vacuum, and the generated chlorine dioxide is dissolved immediately in a diluent liq. to take out in a safety concn.

COPYRIGHT: (C)1994,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing chlorine dioxide.

[0002]

Chlorine dioxide has been used in various industries for many years. In the pulp and paper industry, it is used as a bactericide and pulp bleaching agent in the pulp manufacturing process. In water purification plants, it is used for the purpose of suppressing off-flavors, oxidizing and decomposing trihalomethanes precursors, and disinfecting. It is also used as a disinfectant for process water, drainage and cooling water in various industries. It is used as a disinfectant for food and agricultural products in order to prevent spoilage and diseases. It is also used to sterilize food processing and beverage industry manufacturing plants, canning plants, dairy processing plants, and their manufacturing facilities. In oil fields, chlorine dioxide is used as a sterilizing agent for liquids produced, drilling mud, oil well water, drainage, and cooling towers. It is also used as an oxidant for the purpose of activating oil wells and decomposing sulfides. Chlorine dioxide is used for environmental purification by oxidative decomposition of phenols, mercaptans and cyanides,
It is used for the purpose of suppressing malodor and decomposition of polymer composites.

However, chlorine dioxide has the drawback that it cannot be compressed and transported as a gas or concentrated into a stable liquid. This means that chlorine dioxide must be manufactured where it is used. Currently, chlorine dioxide is produced using chlorite (i) or chlorate (ii) as a raw material. _{(i) NaClO 2 → ClO 2} + Na + + e - (ii) NaClO 3 + e - → ClO 2 + Na + + O 2-

The most typical oxidizer used in the chlorine dioxide production method using chlorite as a raw material is US Pat.
590,057 and U.S. Pat. No. 4,247,531.
Chlorine as described by Hicks in US Pat. No. 4,013,761 or hypochlorous acid as described in US Pat. Other chlorine dioxide production methods include automatic reduction in acidic conditions, reduction with sodium persulfate, and electrolytic oxidation of chlorite. Except for the process invented by Hicks, the process for producing chlorine dioxide from chlorite is generally relatively simple and utilizes equipment with low chlorine dioxide production capacity (up to 0.25 ton / day). . This equipment is relatively inexpensive.

An acid and a reducing agent are used in a chlorine dioxide production method using a chlorate as a raw material. These processes are
Many US Patents, Rapson's 4,534,952,
No. 3,789,108, No. 2,863,722 and No. 2,936,219, Grother's No. 3,920,
No. 801, Westerund, No. 3,404,952. In addition to this, hydrochloric acid, nitric acid, and sulfuric acid are used as acids, and chloride is used as a reducing agent to produce a mixture of chlorine dioxide and chlorine from chlorate. There are many methods for producing chlorine dioxide, such as a method for producing chlorine dioxide containing substantially no chlorine from a chlorate using methanol, chlorous acid, sulfur dioxide, or hydrogen peroxide as a reducing agent. A standard chlorine dioxide production system using chlorate as a raw material has a chlorine dioxide production capacity of 2,000 to 50,000 tons / day.

Generally, the process of producing chlorine dioxide from chlorate requires more complicated and expensive production equipment than the process of using chlorite as a raw material. This is because, as shown in reaction formula (i), for example, in the case of sodium chlorite, it decomposes into sodium ion and chlorite ion in water, and is easily oxidized from the chlorite ion by electron transfer. Chlorine can be produced. However, the reaction formula (i
As shown in i), for example, in the case of sodium chlorate, it decomposes into sodium ion and chlorate ion in water, but in order to produce chlorine dioxide, it is necessary to remove one oxygen atom from chlorate ion. must not. Moreover,
Since chlorate is a more stable compound than chlorite,
Less likely to react than chlorite. And chlorite is
Since chlorine dioxide is once produced from a chlorate and then produced by reacting it with caustic soda, it can be said that the compound is more likely to become chlorine dioxide.

In terms of cost, if the cost of a chemical used in a chlorate-based chlorine dioxide production system is 1, the cost of a chemical used in a chlorite-based chlorine dioxide production process is It becomes 7. If the facility cost of the chlorate-based chlorine dioxide production process is 100, the facility cost of the chlorite-based chlorine dioxide production process is 5. Therefore, since chlorate can be mass-produced at a lower cost than chlorite, it tends to be used in large-scale applications as a raw material for bleaching paper pulp and sodium chlorite. The chlorite-based chlorine dioxide production process is used in industrial fields where the equipment cost is low, and the production equipment is small and convenient, such as relatively small amount of water treatment, sterilization, agriculture, and promotion of processing process. Used.

[0008]

In the conventional chlorine dioxide production method, the chlorine dioxide production process using chlorate as a raw material has a drawback that the production plant is huge and the facility cost is high, and chlorite is used as a raw material. The chlorine dioxide production process described above has the drawback that the cost of the raw chemicals is high. In order to eliminate these drawbacks, an object of the present invention is to provide a method for producing chlorine dioxide from a chlorate as a raw material simply with a relatively small facility and at a high yield.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to alkali metal M chlorate MClO ₃ and sulfuric anhydride (sulfur trioxide) SO.
₃ is used to produce chlorine dioxide by the following reaction. Preferably in _{2MClO 3 + 2SO 3 → 2ClO 2} + M 2 S 2 O 4 present invention, sodium Na is used as the alkali metal M, in this case represented by the following reaction formula. _{2NaClO 3 + 2SO 3 → 2ClO 2} + Na 2 S 2 O
_Four

The method of the present invention is a synthetic process in which chlorine dioxide and persulfuric acid are produced by the reaction of chlorate and sulfuric anhydride. The chlorate and sulfuric anhydride react rapidly in the vacuum reaction zone, after which the reaction product is immediately sent to the diluent. As a preferable operating condition, a fluid such as water or an aqueous solution having a constant pressure is caused to flow through the Venturi tube to bring the reaction column into a vacuum state. This vacuum provides power to deliver the reactants in the reservoir to the reaction column via a flow metering device such as a rotameter (variable area constant head flow meter). The reactants are quickly mixed in the reaction column to form chlorine dioxide and persulfate. Chlorine dioxide and persulfate are preferably diluted by the liquid flowing through the Venturi tube within 5 seconds after the reaction.

The chlorate solution is fed to the reaction zone as an ionizing solution containing 0.5 to 60% by weight, preferably 5 to 50% by weight of sodium chlorate, and anhydrous sulfuric acid in the molecular state is fed to the reaction zone. Ideally supplied. These reactants react promptly and thoroughly in the reaction zone with immediate mixing. The residence time of the reaction product in the reaction zone is controlled to 1 minute or less, preferably 5 seconds or less. The chlorine dioxide evolved is diluted with a suitable diluent and is withdrawn at a safe concentration, typically 0.01 to 100 g / l, preferably 1 to 10 g / l. The reaction zone should be constructed of materials that are durable to the reactants, reaction products and heat of reaction.

[0012]

According to the method of the present invention, chlorine dioxide can be produced with a relatively simple production facility. Further, according to the present invention, a high yield of chlorine dioxide can always be produced even in continuous or intermittent operation. The chlorine dioxide production capacity according to the present invention is 1 to 75,000 kg / day, and the highest efficiency is 15 to 50,000 kg / day. If the equipment cost of the conventional chlorate-based chlorine dioxide production process is 100, the equipment cost of the chlorine dioxide production process of the present invention is 14. Also, if the cost of chemicals used in the conventional chlorate-based chlorine dioxide production process is 1, the cost of chemicals used in the chlorine dioxide production process according to the present invention is 0.5. Therefore, according to the present invention, since the cost of chlorine dioxide is reduced, the application is expanded to the industrial field where chlorine dioxide cannot be used due to its high cost. Also, in the field where chlorine is used, if chlorine dioxide is used instead, environmental problems such as organic chlorine compounds and dioxins can be solved.

[0013]

EXAMPLES Examples of the present invention will be described below. A 40% by weight aqueous sodium chlorate solution was fed to the reaction column together with technical grade anhydrous sulfuric acid at 5.5 mol / min each. The residence time of the reaction product in the reaction column was 5 seconds or less. Ordinary tap water was used as the diluting solution to flow into the Venturi tube. The liquid (product stream) discharged from the chlorine dioxide production apparatus was analyzed to measure the contents of chlorine dioxide, chlorine, chlorite, and chlorate. Ultraviolet spectrophotometry was used to analyze chlorine dioxide, and ion chromatography was used to analyze chlorite, chlorate, and persulfate. A sample of the product stream was purged for 15 minutes and then absorbed in potassium iodide. Chlorine concentration was measured using the amperometric titration method. The chlorine dioxide concentration was also confirmed using the same measurement method. The product stream contained chlorine dioxide in a concentration corresponding to a production rate of 5.3 mol / min and sodium persulfate in a concentration corresponding to a production rate of 5.4 mol / min. The reaction yields 96%.

For comparison, a chlorine dioxide production experiment was conducted using 98% sulfuric acid, 31% hydrochloric acid, 98% sulfuric acid and 95% methanol instead of anhydrous sulfuric acid. No chlorine dioxide was formed in any case.

[0015]

Industrial Applicability As described above, according to the present invention, chlorine dioxide can be produced in a high yield by a simple reaction in a relatively small-sized facility by an instant reaction.

[Procedure amendment]

[Submission date] December 17, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

[0009]

SUMMARY OF THE INVENTION The present invention is directed to alkali metal M chlorate MClO ₃ and sulfuric anhydride (sulfur trioxide) SO.
₃ is used to produce chlorine dioxide by the following reaction. Preferably in _{2MClO 3 + 2SO 3 → 2ClO 2} + M 2 S 2 O 8 The present invention, sodium Na is used as the alkali metal M, in this case represented by the following reaction formula. _{2NaClO 3 + 2SO 3 → 2ClO 2} + Na 2 S 2 O
₈

Claims (3)

[Claims] 1. A method for producing chlorine dioxide, which comprises reacting an alkali metal chlorate with sulfuric acid anhydride (sulfur trioxide). 2. A process for producing chlorine dioxide, which comprises reacting 0.5 to 60% by weight of a chloric acid solution of an alkali metal with anhydrous sulfuric acid (sulfur trioxide) in a molecular state. 3. A method of reacting an alkali metal chlorate with anhydrous sulfuric acid (sulfur trioxide), immediately dissolving chlorine dioxide generated by the reaction in a diluting solution, diluting to a safe concentration, and taking out. A method for producing chlorine dioxide.