JP2001199710A - Method for producing chlorine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing chlorine in which hydrogen chloride in a gas containing hydrogen chloride is oxidized by using a gas containing oxygen, which suppresses an excessive hot spot in a catalyst packed bed, By effectively utilizing the packed bed, stable activity of the catalyst can be maintained and chlorine can be obtained in a stable and high yield, so that catalyst cost, equipment cost, operation cost, operation stability and easy operation The present invention provides a method for producing chlorine which is extremely advantageous from the viewpoint of performance. SOLUTION: In a method of oxidizing hydrogen chloride in a gas containing hydrogen chloride by using a gas containing oxygen in a fixed bed reaction system having a reaction zone composed of a catalyst packed bed, a gas linear velocity based on an empty column is reduced. A method for producing chlorine at 0.70 to 10 m / s.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing chlorine. More specifically, the present invention provides a method for converting hydrogen chloride in a gas containing hydrogen chloride into a gas containing oxygen.
A method for producing chlorine that is oxidized in a fixed-bed reaction system having a reaction zone consisting of a catalyst-packed layer, which suppresses excessive hot spots in the catalyst-packed layer and stabilizes the catalyst by effectively utilizing the catalyst-packed layer. The present invention relates to a method for producing chlorine, which is capable of maintaining stable activity and obtaining chlorine in a stable and high yield, and which is extremely advantageous from the viewpoint of catalyst cost, equipment cost, operation cost, stability and ease of operation. It is.

[0002]

2. Description of the Related Art It is well known that chlorine is useful as a raw material for vinyl chloride, phosgene and the like, and is obtained by oxidation of hydrogen chloride. For example, as a method for producing chlorine by catalytically oxidizing hydrogen chloride with molecular oxygen using a catalyst, a copper-based catalyst called a Deacon catalyst has been conventionally considered to have excellent activity, and copper chloride and potassium chloride have been conventionally used. Many catalysts in which various compounds are added as a third component have been proposed. In addition to the Deacon catalyst, a method using chromium oxide or this compound as a catalyst and a method using ruthenium oxide or this compound as a catalyst have been proposed.

However, the oxidation reaction of hydrogen chloride is 59%.
This is an exothermic reaction of kJ / mol-chlorine, and it is important to suppress excessive hot spots in the catalyst packed bed from the viewpoint of reducing thermal deterioration of the catalyst and ensuring stability and ease of operation. . Excessive hot spots can also cause runaway reactions in the worst case, and cause high temperature gas corrosion of equipment materials due to hydrogen chloride and / or chlorine.

The magazine “Catalyst” (Vol. 33 No. 1)
(1991)), in a reaction between pure hydrogen chloride and pure oxygen using chromium oxide as a catalyst, it is difficult to remove hot spots in a fixed-bed reaction mode, and a fluidized-bed reactor must be used in an actual apparatus. It is described.

[0005]

In such a situation,
The problem to be solved by the present invention is a method for producing chlorine in which hydrogen chloride in a gas containing hydrogen chloride is oxidized using a gas containing oxygen in a fixed bed reaction system having a reaction zone composed of a catalyst packed bed. Therefore, by suppressing excessive hot spots in the catalyst packed bed and effectively utilizing the catalyst packed bed, stable activity of the catalyst is maintained, and chlorine can be obtained in a stable and high yield, Accordingly, it is an object of the present invention to provide a chlorine production method which is extremely advantageous from the viewpoints of catalyst cost, equipment cost, operation cost, operation stability and ease.

[0006]

That is, the present invention oxidizes hydrogen chloride in a gas containing hydrogen chloride by using a gas containing oxygen in a fixed bed reaction system having a reaction zone composed of a catalyst packed bed. The present invention relates to a method for producing chlorine in which a gas linear velocity based on an empty tower is 0.70 to 10 m / s.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The gas containing hydrogen chloride used in the present invention includes a pyrolysis reaction and a combustion reaction of a chlorine compound, a phosgenation reaction of an organic compound, a dehydrochlorination reaction or a chlorination reaction, and a combustion in an incinerator. Any substance including hydrogen chloride generated in the above method can be used. As a gas containing hydrogen chloride, the concentration of hydrogen chloride in the gas is usually 10% by volume or more, preferably 50% by volume or more,
More preferably, 80% by volume or more is used. When the concentration is lower than 10% by volume, when separating generated chlorine and / or recycling unreacted oxygen,
Recycling can be complicated. Components other than hydrogen chloride in the gas containing hydrogen chloride include chlorinated aromatic hydrocarbons such as orthodichlorobenzene and monochlorobenzene, aromatic hydrocarbons such as toluene and benzene, and vinyl chloride and 1,2-dichloroethane. Chlorinated aliphatic hydrocarbons such as methyl chloride, ethyl chloride, propyl chloride and allyl chloride; and aliphatic hydrocarbons such as methane, acetylene, ethylene and propylene; and nitrogen, argon, carbon dioxide, carbon monoxide, phosgene, Hydrogen, carbonyl sulfide,
Inorganic gas such as hydrogen sulfide; In the reaction between hydrogen chloride and oxygen, chlorinated aromatic hydrocarbons and chlorinated aliphatic hydrocarbons are oxidized to carbon dioxide, water and chlorine, and aromatic hydrocarbons and aliphatic hydrocarbons are converted to carbon dioxide and water. Oxidized, carbon monoxide is oxidized to carbon dioxide, and phosgene is oxidized to carbon dioxide and chlorine.

As the gas containing oxygen, oxygen or air is used. Oxygen can be obtained by ordinary industrial methods such as air pressure swinging and cryogenic separation.

The theoretical molar amount of oxygen to 1 mole of hydrogen chloride is 0.25 mole, but it is preferable to supply more than the theoretical amount, and more preferably 0.25 to 2 moles of oxygen to 1 mole of hydrogen chloride. If the amount of oxygen is too small, the conversion of hydrogen chloride may decrease, while if the amount of oxygen is excessive, it may be difficult to separate generated chlorine from unreacted oxygen.

In the present invention, it is preferable that the catalyst-packed layer is divided into at least two reaction zones, and the gas containing oxygen is divided into at least two portions and introduced. As a method of dividing and introducing the gas containing oxygen, the entire amount of the gas containing hydrogen chloride and a part of the gas containing oxygen are introduced into the first reaction zone, and the reactant and the remaining gas containing oxygen are introduced into the first reaction zone. There is a method of introducing the compound into the reaction zone after the second reaction zone. Here, the first
The reaction zone means the most upstream reaction zone for the flow of the raw material gas, and the second reaction zone means the downstream reaction zone of the first reaction zone. The division amount of the gas containing oxygen introduced into the first reaction zone is 5 to 90% of the total amount, preferably 10 to 80%.
%, More preferably 30 to 60%. If the amount of division is too small, it may be difficult to control the temperature of the reaction zone after the second reaction zone.

As the catalyst for the oxidation reaction of the present invention, a known catalyst known as a catalyst for producing chlorine by oxidizing hydrogen chloride can be used. Examples of the catalyst include a catalyst obtained by adding various compounds as a third component to copper chloride and potassium chloride, a catalyst containing chromium oxide as a main component, a catalyst containing ruthenium oxide, and the like. Among them, a catalyst containing ruthenium oxide is preferable, and a catalyst containing ruthenium oxide and titanium oxide is more preferable. Catalysts containing ruthenium oxide are disclosed, for example, in JP-A-10-1821.
No. 04, EP 936184. Catalysts containing ruthenium oxide and titanium oxide are described, for example, in JP-A-10-194705 and JP-A-10-338502. The content of ruthenium oxide in the catalyst is preferably 0.1 to 20% by weight. If the amount of ruthenium oxide is too small, the activity of the catalyst may be low and the conversion of hydrogen chloride may be low. On the other hand, if the amount of ruthenium oxide is too large, the price of the catalyst may be high.

The catalyst may be used in the form of spherical granules, cylindrical pellets, extruded shapes, ring shapes, honeycomb shapes, or granules of an appropriate size which are pulverized and classified after molding. At this time, the catalyst diameter is preferably 10 mm or less. If the catalyst diameter exceeds 10 mm, the activity may be reduced. The lower limit of the catalyst diameter is not particularly limited. However, when the catalyst diameter is excessively small, the pressure loss in the catalyst packed bed increases. In addition,
The term "catalyst diameter" as used herein means the diameter of a sphere in the case of spherical particles, the diameter of a cross section in the case of a cylindrical pellet, or the maximum diameter of a cross section in other shapes.

The amount (volume) of the catalyst used is in a standard state (0
In terms of the ratio (GHSV) to the supply rate of hydrogen chloride at 0.1 ° C. and 0.1 MPa), the reaction is usually performed at 10 to 20,000 h ⁻¹ . The direction in which the raw material flows into the reaction zone may be upward or downward. The reaction pressure is usually from 0.1 to 5 MPa. The reaction temperature is preferably from 200 to 500C, more preferably from 200 to 380C. If the reaction temperature is too low, the conversion of hydrogen chloride may decrease, while if the reaction temperature is too high, the catalyst components may volatilize.

The reaction zone comprising the catalyst packed bed of the present invention is:
A packed catalyst, and an inert substance for diluting the catalyst and / or
Alternatively, it means the whole of the filling molded only with the carrier. The upper and / or lower part of the reaction zone composed of the catalyst packed layer may be filled with an inert substance. However, a packed bed composed only of an inert substance is not considered as a catalyst packed bed.

In the present invention, the gas linear velocity based on the superficial tower must be 0.70 to 10 m / s, preferably 0.70 to 6 m / s, and more preferably 0.70 to 6 m / s.
3 m / s. Thus, by suppressing excessive hot spots in the catalyst packed bed and effectively utilizing the catalyst packed bed, stable activity of the catalyst is maintained, and chlorine can be stably obtained at a high yield. Therefore, catalyst cost, equipment cost, operation cost, operation stability and ease can be ensured. In addition, the gas linear velocity based on the superficial tower of the present invention is the ratio of the total amount of the supply rates in the standard state (0 ° C., 0.1 MPa) of all the gases supplied to the catalyst packed bed to the cross-sectional area of the reaction tube. Means

In the present invention, a fixed bed reaction system having a reaction zone comprising at least two catalyst packed beds in a reaction tube is performed. By effectively utilizing the catalyst packed bed, stable and high yield of chlorine is achieved. It is preferable because it can be obtained at a high rate. As a method of forming at least two catalyst-packed layers, a method of dividing the catalyst-packed layer in a reaction tube into at least two reaction zones in the tube axis direction, and filling catalysts having different activities, compositions, and / or particle sizes, Or a method in which the catalyst is filled with a filler molded only with an inert substance and / or a carrier at a different dilution ratio, or a catalyst and a catalyst diluted with a filler molded only with an inert substance and / or a carrier are filled There are ways to do that. Usually, successive reaction zones are in direct contact with each other, but an inert substance may be filled between the reaction zones. However, a packed bed composed only of an inert substance is not considered as a catalyst packed bed. As the number of divisions of the catalyst-packed layer increases, the catalyst-packed layer can be effectively used. However, industrially, it is usually 2 to 20 reaction zones, preferably 2 to 8 reaction zones.
It is carried out in a reaction zone, more preferably in 2 to 4 reaction zones. If the number of divisions is too large, the number of types of catalyst to be filled may increase, which may be economically disadvantageous.

In the present invention, the catalyst packed bed is divided into at least two reaction zones in the tube axis direction, and the ratio of the first reaction zone is preferably 70% by volume or less, more preferably 30% by volume or less. . In addition, the ratio of the first reaction zone is 70% by volume or less, preferably 30% by volume or less, and the temperature of the second reaction zone is usually 5 ° C. or higher, preferably 10 ° C. or higher than the first reaction zone. And / or the activity of the second reaction zone is usually 1.1 times or more, preferably 1.
It is further preferable to fill the catalyst or the filler molded only with the catalyst and the inert substance and / or the carrier so as to be at least 5 times higher. Here, the activity (mol-HCl /
ml-reaction zone · min) is the unit of catalyst weight and hydrogen chloride reaction activity per hour (mol-HCl / g-catalyst ·
min) and the catalyst loading (g) are calculated as the volume (m
means the calculated value divided by l). The hydrogen chloride reaction activity per unit catalyst weight and time was determined by comparing the catalyst volume with the standard state (0
(C, 0.1 MPa), the ratio to the supply rate of hydrogen chloride is 4400 to 4800 h ^-1 , 0.5 mol of oxygen is supplied to 1 mol of hydrogen chloride at a reaction pressure of 0.1 MPa and a reaction temperature of 280 ° C. It is a value calculated from the amount of chlorine generated at this time. In the first reaction zone, the reaction rate is high because the concentrations of the reactants hydrogen chloride and oxygen are high. Therefore, for example, in a fixed bed reaction of a heat exchange system having a jacket portion, a hot spot is generated on the inlet side of the first reaction zone. On the other hand, the outlet side of the first reaction zone has a temperature close to the temperature of the heat medium in the jacket. If the proportion of the first reaction zone is greater than 70% by volume,
The temperature of the portion near the temperature of the heat medium in the jacket increases, and the catalyst cannot be used effectively.

In the present invention, the catalyst-packed bed is divided into at least two reaction zones in the direction of the tube axis, and the catalyst or the catalyst and the inert substance and / or the inactive substance and / or the first reaction zone have the highest thermal conductivity. Alternatively, it is preferable to fill a filler molded only with a carrier, and further, from the first reaction zone toward the final reaction zone, in the gas flow direction, so that the thermal conductivity of the reaction zone is gradually reduced. preferable. Here, the final reaction zone means the most downstream reaction zone for the gas flow. The thermal conductivity of the reaction zone means the thermal conductivity of the packing filled in the reaction zone. In the reaction zone on the inlet side of the raw material, the reaction rate is high due to the high concentration of the reactants hydrogen chloride and oxygen, and the heat generated by the oxidation reaction is large. Therefore, by filling the reaction zone on the inlet side with a catalyst having a relatively high thermal conductivity of the catalyst, an excessive hot spot can be suppressed.

In the present invention, the catalyst-packed bed is divided into at least two reaction zones in the tube axis direction, and the activity of the reaction zones is sequentially increased in the gas flow direction from the first reaction zone toward the final reaction zone. So that the catalyst or the catalyst and the inert substance and / or
Or by filling the filler molded only with the carrier,
This is preferable because the temperature difference between successive reaction zones can be reduced, and thus the operation can be stably and easily performed.

In the present invention, the catalyst packed bed is divided into at least two reaction zones in the tube axis direction, and the activity of the catalyst or the catalyst is increased so that the activity of the final reaction zone is higher than the activity of the immediately preceding reaction zone. And a filler molded only with an inert substance and / or a carrier, and a hot spot in the final reaction zone is
A method in which the temperature is lower than the hot spot in the immediately preceding reaction zone is preferable. If the activity of the final reaction zone is lower than that of the previous reaction zone and the hot spot of the final reaction zone is higher than the hot spot of the immediately preceding reaction zone, hydrogen chloride is oxidized with oxygen and converted to chlorine and water. Since the reaction is an equilibrium reaction, the conversion of hydrogen chloride may be low due to the chemical equilibrium composition.

In the present invention, it is preferable to divide the catalyst packed bed into at least two reaction zones in the direction of the tube axis and to adjust the gas temperature at the outlet of the final reaction zone to 200 to 350 ° C.
A method of setting the temperature to 200 to 320 ° C is more preferable. If the gas temperature at the outlet of the final reaction zone is higher than 350 ° C., the conversion of hydrogen chloride to oxygen and conversion to chlorine and water is an equilibrium reaction. May be dominated and lower.

In the present invention, a method in which the temperature of the reaction zone comprising the catalyst packed bed is controlled by a heat exchange method is preferable because the reaction heat is well removed and the stability and operability of the operation are ensured. The heat exchange method of the present invention means a method in which a jacket is provided outside a reaction tube filled with a catalyst, and reaction heat generated by the reaction is removed by a heating medium in the jacket. In the heat exchange method, the temperature of a reaction zone formed of a catalyst packed bed in a reaction tube is controlled by a heat medium in a jacket. Industrially, a reaction tube having reaction zones consisting of catalyst packed layers arranged in series is arranged in parallel, and a fixed tube multi-tube reactor of a multi-tube heat exchanger type having a jacket portion on the outside is used. You can also. As a method other than the heat exchange method, there is an electric furnace method, but there is a problem that it is difficult to control the temperature of the reaction zone.

Examples of the heat medium include a molten salt, steam, an organic compound and a molten metal, but a molten salt or steam is preferred in terms of thermal stability and ease of handling, and more favorable thermal stability. In view of this, a molten salt is more preferred. Molten metal has problems such as high cost and difficulty in handling. As the composition of the molten salt, a mixture of 50% by weight of potassium nitrate and 50% by weight of sodium nitrite,
53% by weight of potassium nitrate and 40% by weight of sodium nitrite
And 7% by weight of sodium nitrate. Examples of the organic compound include Dowsome A (a mixture of diphenyl oxide and diphenyl).

In the present invention, the temperature of the reaction zone composed of the catalyst-packed layer is controlled by at least two independent temperature controls. It is preferable because it can be obtained by As this method, a method in which the catalyst packed bed in the reaction tube is divided into at least two reaction regions in the tube axis direction and the temperature of the reaction region is controlled by a combination of a heat exchange method and a method other than the heat exchange method, at least A method in which an independent jacket portion is formed in the reaction region divided into two, and a heating medium is independently circulated to control the temperature of the reaction region, and / or the jacket portion is divided into at least two parts by a partition plate and partitioned. A method of controlling the temperature of the reaction zone by independently circulating a heat medium in the portion where the heat medium is circulated. The partition plate may be directly fixed to the reaction tube by welding or the like, but in order to prevent thermal distortion from occurring in the partition plate and the reaction tube, within a range where the heat medium can be substantially independently circulated. An appropriate distance can be provided between the partition plate and the reaction tube. It is preferable that the flow of the heat medium in the jacket is made to flow upward from below. The more the number of reaction zones by independent temperature control, the more effectively the reaction zone can be utilized. However, industrially, usually 2 to 20 reaction zones, preferably 2 to 8 reaction zones, more preferably 2 to 8 reaction zones. ４4 reaction zones. If the number of reaction zones to be controlled is too large, the number of devices for temperature control may increase, which may be economically disadvantageous.

In the present invention, a method in which the catalyst packed bed is divided into at least two reaction zones in the tube axis direction and the temperature of the entire reaction zone is controlled by a heat exchange method is a method in which the reaction heat is removed satisfactorily. Is preferable because the stability and easiness of the above are ensured.

The inner diameter of the reaction tube is usually 10 to 50 mm, preferably 10 to 40 mm, more preferably 10 to 30 m.
m. If the inner diameter of the reaction tube is too small, it may be disadvantageous because an excessive number of reaction tubes is required in order to obtain a satisfactory throughput of hydrogen chloride in an industrial reactor. If the inner diameter is too large, an excessive hot spot may be generated in the catalyst packed bed.

The ratio (D / d) of the inner diameter (D) of the reaction tube to the catalyst diameter (d) is usually 5/1 to 100/1, preferably 5/1 to 50/1, more preferably 5/1. ２０20/1. If the ratio is too small, excessive hot spots may occur in the catalyst packed bed, or an excessive number of reaction tubes may be required to obtain a satisfactory throughput of hydrogen chloride in an industrial reactor. If it is disadvantageous and the ratio is too large, excessive hot spots may be generated in the catalyst packed bed, or pressure loss of the catalyst packed bed may be large.

[0028]

The present invention will be described below with reference to examples. Example 1 In a reactor, a Ni reaction tube having an inner diameter of 18 mm and a length of 1 m equipped with a jacket using a molten salt (potassium nitrate / sodium nitrite = 1/1 weight ratio) (temperature measurement of an outer diameter of 5 mm) was used. A fixed-bed reactor comprising a sheath tube was used. In the reaction tube, anatase crystalline TiO ₂ having a diameter of 1 to 2 mm was placed.
Supported 6.6% by weight ruthenium oxide spherical granular catalyst 99.4
g (100 ml) to form a catalyst-packed layer. 238 of α-Al ₂ O ₃ spheres having a diameter of 2 mm (manufactured by Nikkat Co., Ltd., SSA995) were respectively placed on the upper and lower parts of the catalyst packed bed.
g and 164 g. The anatase crystalline TiO ₂ supported 6.6 wt% ruthenium oxide spherical granular catalyst having a diameter of 1 to 2 mm was prepared according to the method described in JP-A-10-338502. used. 9.4 l / min of hydrogen chloride (standard condition, hydrogen chloride: 99% by volume or more) and 4.7 l / m of oxygen
in (standard condition, oxygen: 99% by volume or more) in an electric furnace
A 30 mm inner diameter Ni preheated tube heated to 80 ° C. (outer diameter 6 mm)
mm of a temperature measuring sheath tube) and heated, and water 0.75
6mm / min heated to 380 ° C in an electric furnace 2mm inner diameter
Was supplied to a stainless steel preheating tube and vaporized into steam.
Subsequently, the preheated mixed gas of hydrogen chloride and oxygen was mixed with water vapor, and then flowed downflow from the upper part to the lower part of the reaction tube. The molar ratio of hydrogen chloride / oxygen / water is 10/5
/ 1, GHSV is calculated to be 5639 h ^-1 , and the gas linear velocity based on an empty tower is calculated to be 1.1 m / s. The temperature of the molten salt in the jacket is 336 ° C, the reaction temperature of the catalyst layer is 337 ° C at the inlet,
The outlet temperature was 356 ° C and the hot spot was 368 ° C. At this time, the pressure at the inlet of the reaction tube was 0.12 MPa-G. The outlet gas is sampled in an aqueous potassium iodide solution to absorb generated chlorine, unreacted hydrogen chloride and generated water, and the amount of chlorine generated and the amount of unreacted hydrogen chloride are determined by iodine titration and neutralization titration, respectively. Was measured. The conversion of hydrogen chloride to chlorine was 21.5%.

Comparative Example 1 The amount of the catalyst was 48.1 g (49 ml), and the amount of hydrogen chloride was 4.7.
1 / min, 2.4 l / min of oxygen and 0.378 g of water
The procedure was performed in the same manner as in Example 1 except that / min was used. The molar ratio of hydrogen chloride / oxygen / water is 10/5/1, GH
The SV is 5761 h ^-1 and the gas linear velocity based on the superficial tower is 0.54
m / s. The temperature of the molten salt in the jacket is 3
At 36 ° C., the hot spot of the catalyst layer is 3 due to the heat of reaction.
The temperature exceeded 80 ° C and became uncontrollable.

Comparative Example 2 The amount of the catalyst was changed to 18.8 g (20 ml), and 1.9 hydrogen chloride was used.
l / min, oxygen 0.96 l / min and water 0.151
Except having set it as g / min, it carried out based on Example 1. The molar ratio of hydrogen chloride / oxygen / water is 10/5/1, GH
The SV is 5724 h ^-1 and the gas linear velocity based on the superficial tower is 0.22.
m / s. The temperature of the molten salt in the jacket is 3
At 36 ° C., the hot spot of the catalyst layer is 3 due to the heat of reaction.
The temperature exceeded 80 ° C and became uncontrollable.

[0031]

As described above, according to the present invention, there is provided a method for producing chlorine by oxidizing hydrogen chloride in a gas containing hydrogen chloride using a gas containing oxygen, the method comprising: By effectively controlling the catalyst packed bed, the stable activity of the catalyst can be maintained, and chlorine can be obtained in a stable and high yield. From the viewpoint of the stability and easiness of the production of chlorine.

Claims (3)

[Claims] 1. A method for oxidizing hydrogen chloride in a gas containing hydrogen chloride by using a gas containing oxygen in a fixed bed reaction system having a reaction zone comprising a catalyst packed bed, wherein a gas linear velocity based on an empty column is used. Is 0.70 to 10 m / s. 2. The method for producing chlorine according to claim 1, wherein the oxidation is carried out by a fixed bed reaction system having a reaction zone comprising at least two catalyst packed beds. 3. The method for producing chlorine according to claim 1, wherein the temperature of the reaction zone comprising the catalyst packed bed is controlled by at least two independent temperature controls.