JPS62113701A - Production of chlorine - Google Patents

Abstract

PURPOSE:To produce chlorine from hydrogen chloride at a high space velocity in high efficiency and high low-temperature catalytic activity, by oxidizing hydrogen chloride with an oxygen-containing gas in the presence of a specific catalyst. CONSTITUTION:1mol of chromic anhydride (CrO3) is added to an aqueous solution containing 6-20mol of hydrochloric acid and made to react with each other at room temperature -100 deg.C for 10min-20hr. The obtained aqueous solution is added with ammonia to adjust the pH to nearly neutral state. The precipitated chromium compound is collected by filtration, washed with water, extruded and formed in the form of pellet, dried at room temperature -120 deg.C and calcined at 400-800 deg.C. The catalyst produced by the above process is packed in a reaction tube and heated at 300-400 deg.C. A gaseous mixture of hydrogen chloride and an oxygen-containing gas is supplied to the reaction tube at a rate of 200-1,800Nl/HCl/Hr.kg.Cat. The amount of oxygen is excess to hydrogen chloride by 5-200 equivalent %.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing chlorine, and more particularly to an improvement in a method for producing chlorine by oxidizing hydrogen chloride gas with an oxygen-containing gas.

(Prior art and the problem to be solved by the invention) Chlorine is produced on a large scale by salt electrolysis, and although the demand for chlorine has increased dramatically in recent years, it is produced simultaneously during salt electrolysis. The increase in demand for caustic soda is less than that for chlorine, making it difficult to properly balance the imbalance.

On the other hand, a large amount of hydrogen chloride is produced as a by-product during the chlorination reaction of a chemical compound or a reaction using phosgene, and the river of by-product hydrogen chloride is larger than the demand for hydrochloric acid by 1 d. The amount of hydrogen chloride in the tank remains unused and is wasted.

Also, the processing costs for disposal can be reduced.

If chlorine can be efficiently recovered from hydrogen chloride, which is largely discarded as described above, the demand for chlorine can be met without creating an imbalance with the production of t-Y soda.

What is the reaction that produces chlorine by oxidizing hydrogen chloride?

It has long been known as the Deacon reaction. 1868
A copper-based catalyst invented in 1996 was considered to be the catalyst with the most excellent activity, and it was used in chloride steel, 'l
Many catalysts have been proposed in which various chemicals are added as third components to potassium silicide. However, in order to oxidize hydrogen chloride at a reaction rate sufficient for industrial use using these catalysts, it is necessary to raise the reaction temperature to 400°C or higher, and the life of the catalyst may be shortened due to the scattering of catalyst components. Low height etc. become a problem.

Furthermore, for the oxidation reaction of hydrogen chloride.

・Since the amount of chlorine produced decreases as the temperature increases, it is desirable to use a catalyst that is active at as low a temperature as possible, which is advantageous in terms of corrosion of low-temperature gas equipment.

From this point of view, iron-based and other catalysts have been proposed as catalysts other than copper-based, but no catalyst is known that exhibits sufficient practical performance. Compared to copper-based catalysts, chromium oxide has
Because of its stability and durability against high temperatures, there have been proposals to use chromium oxide as an oxidation catalyst for hydrogen chloride, but no results have yet been reported showing sufficient activity. For example, British patent no. Hydrogen chloride is passed through catalyst E, which has been thermally decomposed by impregnating it on a suitable carrier, at around 400°C to generate chlorine, and after the catalyst is deactivated, the supply of hydrogen chloride is stopped and air is passed through to decompose the catalyst. After regeneration, a method is described in which the air flow is cut off and hydrogen chloride is allowed to flow again. Also, in British Patent No. 676.667,
Using a catalyst containing dichromate or dark green chromium oxide on a carrier, hydrogen chloride and oxygen-containing gas are
React at a reaction temperature of 0°C and a space velocity of 38011r'',
The bottom price is 67.4! At a space velocity of 68,011r'', the conversion rate of hydrogen chloride was 63%.The reaction was observed even at a reaction temperature of 340°C, but in this case, the space velocity was set to a low value of 6,511r''. keep it,
A conversion rate of only 52% was obtained.

As described above, even if chromium oxide is used as a catalyst, the conventionally known method has a high reaction temperature and a low space velocity, so it is not in a state where it can withstand commercial operation. That is, conventionally reported chromium oxide catalysts do not exhibit particularly superior performance compared to copper-based catalysts.

Therefore, the object of the present invention is low temperature activity.

An object of the present invention is to provide a method for efficiently producing chlorine from hydrogen chloride using a catalyst that can process hydrogen chloride at a high space velocity and high conversion rate.

[L stage for solving the problem] The present inventors have proposed a method for producing chlorine by oxidizing hydrogen chloride,
In particular, as a result of various studies regarding catalysts used in oxidation reactions,
Regarding the oxidation reaction of hydrogen chloride, using a chromium oxide catalyst produced according to the catalyst gJ preparation method, which has never been reported before, allows the reaction temperature to be lower than that of conventionally known catalysts, and the space velocity to be much higher than that of the conventional method. The inventors discovered that chlorine can be produced from hydrogen chloride at a high conversion rate using a hydrogen chloride method, and completed the present invention.

That is, the gist of the present invention is that when hydrogen chloride is oxidized with an oxygen-containing gas to produce chlorine, chromic anhydride is reacted with an aqueous hydrochloric acid solution, and then the resulting aqueous solution is reacted with ammonia. Presence of a catalyst prepared from the produced chromium compound, or a catalyst prepared from a mixture consisting of the chromium compound and silicon compound described above F
The purpose is to react to the

The raw material hydrogen chloride used in the method of the present invention is usually +
Hydrogen chloride produced as a by-product during the compound chlorination reaction or hydrochloric acid produced as a by-product such as hydrogen chloride produced as a by-product during the reaction of phosgene with an organic compound are often used. The oxidizing agent for hydrogen chloride is an oxygen-containing gas, and oxygen gas or air is often used. Oxygen gas is often used when the reactor is a fluidized bed type, and air is often used when the reactor is a fixed bed type. The molar ratio of hydrogen chloride used for the reaction and oxygen in the oxygen-containing gas is hydrogen chloride 1
This is after 174 moles (equivalents) of oxygen to that gas, and normally,
Oxygen is often used in an excess of 5 to 200 equivalents. The amount of hydrochloric acid supplied to the catalyst bed is 200 to 180 ONj/H.
A range of g cat is suitable for r. The reaction temperature is 3
00 to 400°C, especially 330 to 380°C is frequently used.

The catalyst used in the method of the present invention is prepared by the following method.

Chromic anhydride and CrO3 are added to an aqueous hydrochloric acid solution and reacted. Alternatively, the reaction is carried out by blowing hydrogen chloride into a solution of (:r03 dissolved in water).The reaction between CrO3 and hydrogen chloride is carried out in the temperature range from room temperature to !00°C. The required amount of hydrogen is Cry;, 1
A range of 6 to 20 moles of lIC1 is often used. The time required for the reaction ranges from 10 minutes to 20 hours. Next, ammonia is added to the aqueous solution described in F to make Pl+ in the aqueous solution near neutral, thereby precipitating a chromium compound.

As the ammonia source, aqueous ammonia is usually used, or ammonia gas, liquid ammonia, or a compound that generates ammonia such as urea can also be used.

In the case of a catalyst consisting of a chromium compound and a silicon compound,
A silicon compound, such as silica sol or ethyl silicate, is mixed with the precipitate of the chromium compound, and a catalyst is prepared by the method described below. Alternatively, a silicon compound of silica sol is added in advance to an aqueous solution of chromic anhydride and hydrochloric acid,
Ammonia is added thereto to obtain a mixture of a chromium compound and a silicon compound. The ratio of chromium and silicon is Cr203.4
0~95WLL 5i02・5~6 ON L! A range of is preferred.

A chromium compound or a mixture of a chromium compound and a silicon compound is washed with water and separated using a conventional method, then made into pellets by a method such as extrusion molding, dried at room temperature to 120°C, and then calcined to produce a fixed bed catalyst. . A suitable firing temperature is in the range of 400 to 800°C. A slurry consisting of a chromium compound or a mixture of a chromium compound and a silicon compound is made into a fine spherical powder using a spray dryer, and then
Those calcined at ~800°C are suitable for use as catalysts for fluidized beds.

That is, the catalyst used in the method of the present invention is a catalyst prepared from the precipitation of a chromium compound obtained by reacting chromic anhydride with hydrogen chloride and then reacting with anthonia. Catalysts that have been thermally decomposed or catalysts that have thermally decomposed a reaction product of chromic anhydride and ammonia do not have high activity. Additionally, it is essential to use ammonia as a reagent for reacting the reaction product of chromic anhydride and hydrogen chloride, and if an alkali such as caustic soda or soda carbonate is used instead of ammonia, an active catalyst cannot be obtained. .

〔Effect of the invention〕

According to the method of the present invention, the space velocity of hydrochloric acid is 70.
0 to 1800 Hr'', which is much higher than the conventional method, and the resulting conversion rate reaches the equilibrium conversion rate of LOOO$. Since a high conversion rate of hydrogen chloride can be obtained at a much higher space velocity, it is possible to efficiently produce chlorine from hydrogen chloride, thereby providing a method for producing chlorine that is advantageous for commercial production.

Example 1 500 g of chromic anhydride was added to dissolve 35 in hydrochloric acid 31, and the mixture was reacted with stirring at 65° C. for 1 hour. Reaction path 7'
? Bubble nitrogen gas into the reaction solution L at 70°C for 10 minutes, let it cool, add ion-exchanged water, and reduce the total volume to 6.
Diluted to L. Next, 1.91 g of 2896 ammonia water was injected over 3 hours while stirring thoroughly.

The generated precipitate was filtered and washed with water, and then made into a paste using Nigu and extruded. After drying at 100℃ for 5 hours, 250℃
℃3 hours, 600℃ for 3 hours, 4m/mφx 5
m/ml catalyst was manufactured by J5I.

100 g of this catalyst was packed into a Hastelloy-C reaction tube with an inner diameter of 1 inch, and the catalyst bed was heated to 340°C using a sand 7AE moving bath from the outside.
heated to. Hydrogen chloride gas 80t/llr, oxygen 301
A mixed gas of /fir was supplied to the reaction tube, and chlorine in the generated gas was analyzed. Chlorine was produced at a conversion rate of hydrogen chloride of 80%.

Example 2 500 g of chromic anhydride was added and dissolved in 31% 35% hydrochloric acid, and reacted at 70° C. for 30 minutes with stirring. After reaction path γ, air was bubbled into the E reaction solution at 70° C. for 10 minutes, then allowed to cool, and ion-exchanged water was added to dilute the solution to 71. Next, add 28t ammonia water 1. while stirring thoroughly.
9A was injected over a period of 3 hours.

The generated precipitate was washed with water and filtered, and silica sol (Sin, 2
0WL96) was added and stirred thoroughly to form a uniform slurry. Adjust the slurry concentration to about 6.5t, and use a spray dryer to shape it into microspheres. It was dried and granulated. Next, the mixture was calcined in air at 250° C. for 211 rs and at 500° C. for 3 Hrs to prepare a microspherical catalyst for a fluidized bed.゛F of catalyst
Microspheres with an average particle diameter of 65 μm, a packing density of 1.2, and good shore abrasion resistance were obtained.

A fluidized bed reactor with an inner diameter of 2 inches was filled with 350 g of this catalyst, and 240 g/fir of chloride water and 904 g/llr of oxygen were charged.
was introduced into the catalyst bed, and the outside was heated to 340°C to cause a reaction.

The catalyst bed temperature was 370°C, and chlorine was produced at a hydrogen chloride conversion rate of 7696.

Comparative Example 1 In the same manner as in Example 1, 1 0qb R sodium aqueous solution was added to a compound obtained by reacting chromic anhydride and hydrogen chloride, and the pl+ of the mixture was adjusted to 7.5. The resulting precipitate was washed, filtered, kneaded in a kneader to form a paste, and extruded. Dry the molded product at 100°C for 5 hours, then dry at 250°C2
Hrs, then baked at 600℃ for 3 hours, diameter 4n+n
+, height 5ffI11 catalyst was prepared.

The obtained catalyst was subjected to a reaction in the same manner as in Example 1, and the conversion rate of hydrogen chloride was measured. As a result, chlorine was generated at a conversion rate of hydrogen chloride of 34t.

Comparative Examples 2 to 4 Chromic anhydride, ammonium chromate, and ammonium dichromate were heated to 100° C. to 600° C. over 7 hours, and air was blown into them to sinter them in a fluidized state. The obtained decomposed product was extruded using the same method as Comparative Example 1, and the activity was measured using the reaction method of Comparative Example 1. The obtained results are shown in Table 1.
Shown below.

Table 1

Claims (2)

[Claims] (1) When producing chlorine by oxidizing hydrogen chloride with oxygen-containing gas, in the presence of a catalyst consisting of a chromium compound produced by reacting chromic anhydride with an aqueous hydrochloric acid solution and reacting the resulting aqueous solution with ammonia. A method for producing chlorine, which comprises reacting with. (2) The method according to claim 1, wherein the catalyst comprises the chromium compound and a silicon compound.