JPH1015389A - Method for regenerating catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively regenerate a chromium oxide catalyst with deteriorated activity by impregnating the catalyst with a solution containing copper, alkali metal, rare earth metal, and transition metal excluding copper and burning it when the catalyst of chromium oxide as a main component which is used for the production of chlorine by the oxidation of hydrogen chloride. SOLUTION: In the regeneration of a catalyst of chromium oxide as a main component which is used for the production of chlorine by the oxidation of hydrogen chloride, the catalyst is impregnated with a solution containing copper, alkali metal, rare earth metal, and transition metal excluding copper and burned at 800 deg.C or below. In this process, potassium is preferable as alkali metal, lanthanum as rare earth metal, and cobalt as transition metal excluding copper. The catalyst containing chromium oxide as a main component, which is a basic catalyst, is prepared by burning a mixture of chromium salt such as chromium nitrate, ammonia or a compound which releases ammonia such as urea, and a silicon compound at 800 deg.C or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for regenerating a chromium oxide catalyst used for producing chlorine by catalytic oxidation of hydrochloric acid.

[0002] Chlorine is produced on a large scale by electrolysis of salt, but it is difficult to balance the demand with co-produced caustic soda. On the other hand, hydrogen chloride is by-produced in large amounts during the chlorination reaction of organic compounds or the reaction with phosgene, but the amount of by-products is much larger than demand, so a large amount of hydrogen chloride requires considerable processing costs. It is wasted and wasted.

Therefore, if chlorine can be efficiently recovered from hydrogen chloride, the demand for chlorine can be satisfied without causing imbalance with caustic soda.

[0004]

2. Description of the Related Art There have been proposals to use chromium oxide as an oxidation catalyst for hydrogen chloride, but no results have been reported that show sufficient performance for industrial use.

For example, impregnated with an aqueous solution of chromic anhydride or chromium nitrate in a suitable carrier and pyrolyzed, hydrogen chloride is passed at about 400 ° C. to generate chlorine,
After the catalyst is deactivated, a method has been proposed in which the supply of hydrogen chloride is stopped, the air is circulated to regenerate the catalyst, the supply of air is stopped, and hydrogen chloride is circulated again (UK Patent No. 5).
84,790).

Further, by using a catalyst in which dichromate or dark green chromium oxide is supported on a carrier, hydrogen chloride and oxygen-containing gas are reacted at a reaction temperature of 420 to 430 ° C. and a space velocity of 380 Hr ⁻¹ , A hydrogen chloride conversion of 67.4% equilibrium has been obtained (GB 676,667).
issue). At this time, the conversion rate is 63% at the space velocity of 680 Hr ^-1.
It is. The reaction is also observed at 340 ° C., but in this case the space velocity is reduced to 65 Hr ⁻¹ and the conversion is 5
You only get 2%. These methods have high reaction temperatures and low space velocities, and are not practical for industrial implementation.

On the other hand, it has been found that a chromium oxide catalyst obtained by calcining a compound obtained by reacting an aqueous solution of chromic acid with ammonia at a temperature of 800 ° C. or less has high activity in oxidizing hydrogen chloride. (Japanese Unexamined Patent Publication No.
No. 75104), the use of the catalyst makes it possible to produce chlorine at a lower temperature and a higher space-time yield than conventionally known catalysts.

However, as a problem of the catalyst,
When used for the oxidation reaction of waste hydrogen chloride gas, the activity decreases several months after the start of the reaction.
As a method for activating the catalyst, a method of contacting with a hydrogen chloride gas and / or an oxygen-containing gas in a high temperature gas phase has been proposed (Japanese Patent Application Laid-Open No. 62-254846). When used for oxidation reactions,
Although the activity returns to the level of a new catalyst for several days after the start of the reaction, the activity starts to decrease after one week or more, and there is a problem that it cannot withstand long-term use.

As another activation method, a method has been proposed in which the catalyst is impregnated with an aqueous solution of a chromium salt or chromium oxide and calcined at a temperature of 800 ° C. or less (Japanese Patent Application Laid-Open No. HEI 3 (1993) -313).
If the catalyst activated by this method is also used in the oxidation reaction of hydrogen chloride gas, the activity returns to the same level as that of the new catalyst for several days after the start of the reaction, but the activity starts to decrease after one month or more. However, there is a problem that it cannot withstand long-term use.

A method for producing chlorine by oxidizing hydrogen chloride using a copper-based catalyst has long been known as the Deacon reaction. For a copper-based catalyst according to the invention of Deacon in 1868, copper chloride and potassium chloride were subsequently used. Many catalysts in which various compounds are added as a third component have been proposed. However, in order to use this catalyst industrially, a sufficient reaction rate cannot be obtained unless the reaction temperature is increased.
The volatilization of the catalyst components occurs, causing a short-term decrease in activity and a fatal problem with the life of the catalyst.Also, the catalyst solidifies and becomes difficult to fluidize, especially when used as a fluidized bed catalyst, making it difficult to use it as a catalyst. It is also known that there is a big problem that it will not be done.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the above-mentioned known catalysts when producing chlorine by oxidizing hydrogen chloride. It is to provide a useful reproduction method.

[0012]

Means for Solving the Problems In order to solve the problems of the present invention, the present inventors diligently studied a method for regenerating a catalyst containing chromium oxide as a main component used for producing chlorine by oxidizing hydrogen chloride. As a result, we impregnated a catalyst based on chromium oxide with reduced activity with a solution containing copper, alkali metals, rare earth metals, and transition metals other than copper,
By calcination at a temperature of 800 ° C. or less, the chromium oxide catalyst with reduced activity can be activated and regenerated, and the above-mentioned problems of the conventional chromium oxide catalyst regeneration method do not occur.
The present inventors have found a method for regenerating a chromium oxide catalyst that can withstand industrial use for a long time, and have completed the present invention.

That is, according to the present invention, when regenerating a catalyst containing chromium oxide as a main component used in producing chlorine by oxidizing hydrogen chloride with an oxygen-containing gas, copper, alkali metal, rare earth metal, And a solution containing a transition metal other than copper and a catalyst.

[0014]

DETAILED DESCRIPTION OF THE INVENTION The chromium oxide-based catalyst used as the base catalyst in the process of the present invention is, for example, a chromium salt such as chromium nitrate, chromium chloride or a chromium salt of an organic acid and ammonia or urea. It is prepared by calcining a mixture comprising a reactant with an ammonia releasing compound and a silicon compound at a temperature of 800 ° C. or less. Although the mixing ratio of chromium and silica is not particularly limited, Cr _{2 in} the form obtained after final calcination of the catalyst is used.
By the weight ratio of O ₃ and SiO ₂ , Cr ₂ O ₃ / SiO ₂ = 5/95
The range of ９５95/5 is frequently used.

As the raw material hydrogen chloride used in the production of chlorine using the catalyst of the present invention, the chemical industry usually uses hydrogen chloride which is a by-product of chlorinating organic compounds or reacting with phosgene. Is economical, but not limited thereto.

An oxygen-containing gas is used as an oxidizing agent for hydrogen chloride, and oxygen gas or air is generally used frequently. The type of the reactor can be either a fixed bed or a fluidized bed. However, in the case of a reaction that generates a large amount of heat, such as an oxidation reaction of hydrogen chloride, a fluidized bed that can easily remove heat is often used. In the case of a fluidized bed type, oxygen gas is often used, and in the case of a fixed bed type, air is often used.

The molar ratio of hydrogen chloride used in the reaction to oxygen in the oxygen-containing gas is about 1/4 mole (equivalent) of oxygen to 1 mole of hydrogen chloride.
Often used in excess of%.

The hydrogen chloride supplied to the catalyst bed is 200 to 1
A range of 800 (Nl / Hr.) Kg-cat. Is suitable.

The reaction temperature is between 300 and 450 ° C., in particular 360
Frequently used at ~ 420 ° C. This reaction can be carried out under normal pressure or under pressure, but it is often preferable to carry out the reaction under a pressure of usually 1 to 11 × 10 ⁵ Pa.

When a conventionally known catalyst containing chromium oxide as a main component is used for a reaction for several months to half a year under the above reaction conditions, its activity is reduced, and the conversion of hydrogen chloride is initially 70 to 70%.
What shows 80% becomes 50-60%.

Catalysts with reduced activity include copper, alkali metals,
The activity can be recovered by impregnating with a solution containing a rare earth metal and a transition metal other than copper and firing at a temperature of 800 ° C. or less.

In the present invention, as a method for adding a transition metal other than copper, an alkali metal, a rare earth metal, and copper to a catalyst containing chromium oxide as a main component, a conventionally known catalyst such as an impregnation method, a coprecipitation method, or a vapor deposition method may be used. Although a preparation method can be adopted, the impregnation method is more effective and the operation is simple.

As an example of the impregnation method, there is a method in which a catalyst containing chromium oxide as a main component is impregnated with a solution containing copper, an alkali metal, a rare earth metal, and a transition metal other than copper, and calcined at a temperature of 800 ° C. or less. Can be

In the method of the present invention, copper, an alkali metal,
The use of three components of rare earth metals is indispensable, and the activity of the regenerated catalyst is not sufficiently improved even if any of these components is missing.

Regarding the influence of the impregnation amount of these three components, while the effect of improving the activity is increased as the impregnation amount is increased, the fluidity of the catalyst tends to decrease. Therefore, by adding a transition metal other than copper to the three components, the catalytic activity is further improved,
It is possible to reduce the decrease in the activity over time and to prevent the decrease in the catalyst fluidity due to the increase in the impregnation amount.

The impregnation method of a solution in which a transition metal other than copper is dissolved is carried out before, simultaneously with and after the impregnation of a solution containing copper, an alkali metal and a rare earth metal. A post-impregnation method is possible, and there is no particular limitation on the impregnation method.

As the copper component, specifically, for example, copper nitrate, copper sulfate, copper chloride, and copper oxide can be used. Similarly, alkali metals, rare earth metals, and transition metals other than copper can also be used. , Sulfate, chloride, oxide and the like can be used. Specific examples of the alkali metal component include potassium nitrate, potassium sulfate, potassium chloride, sodium nitrate, sodium sulfate, sodium chloride, and sodium oxide. Rare earth metal salts include nitrates, sulfates, halides, oxides and the like of lanthanum, praseodymium, neodymium, promethium, samarium, europium and the like, with lanthanum salts being preferred. Examples of transition metals other than copper include nitrates, sulfates, halides, and oxides of titanium, vanadium, manganese, iron, cobalt, nickel, and the like, and among them, cobalt salts are preferable.

The effect can be obtained as the concentration of copper, alkali metal, rare earth metal and transition metal other than copper increases, but copper = 0.01 in atomic ratio to chromium of the catalyst containing chromium oxide as a main component. -0.3, potassium = 0.005-0.2, lanthanum = 0.01-0.3, cobalt = 0.01-0.3.

[0029]

Next, the method of the present invention will be described in more detail with reference to Examples. Example 1 A glass fluidized bed reactor having an inner diameter of 1 inch was charged with 40 g of a microsphere fluidized bed catalyst having an average particle size of 60 µm and consisting of 75% by weight of chromia and 25% by weight of silica. Waste hydrogen chloride gas was introduced into the fluidized bed at 334 ml / min and oxygen at 167 ml / min, and the outside of the reaction tube was heated to 380 ° C. in an electric furnace to cause a reaction. Oxygen / hydrogen chloride molar ratio = 1/2, oxygen excess ratio 100
%. The conversion of hydrogen chloride on the third day of the reaction was 73%
Met. On the 30th day from the start of the reaction, the conversion was 67%,
On day 65, it dropped to 55%. Cu
_{(NO 3) 2 · 3H 2} O3.78g, KNO 3 1.56g, L
5.32 g of a (NO ₃ ) ₂ .6H ₂ O and Co (NO ₃ )
After simultaneously impregnated with an aqueous solution 27ml was dissolved ₂ · 6H _{2 O5.92g,} and calcined 5 hours at 420 ° C.. This regenerated catalyst 40
g was reacted as described above. The conversion of hydrogen chloride on the third day from the start of the reaction was 78%. On the 30th day from the start of the reaction, the conversion was 70%, and on the 65th day, the conversion was 68%, indicating an activity and life equivalent to or higher than that of the new catalyst.

Example 2 Average particle composed of 75% by weight of chromia and 25% by weight of silica
40 g of microsphere fluidized bed catalyst with a diameter of 60 µ
Into a glass fluidized bed reactor. As in the first embodiment
The spent catalyst obtained by the reaction was extracted, and Cu was added to the spent catalyst.
(NO_Three)_Two・ 3H _Two3.78 g of O, KNO_Three1.56g, L
a (NO_Three)_Two・ 6H_Two5.32 g of O, and Co (NO_Three)
_Two・ 6H_TwoImpregnated with 25 ml of an aqueous solution in which 2.96 g of O was dissolved
Then, it was baked at 420 ° C. for 5 hours. 40 g of this regenerated catalyst
The reaction was carried out as described above. Chlorinated water on the third day of the reaction
The conversion of the element was 77%. 30 days after the start of the reaction
The conversion rate was 68%, and on the 65th day, the conversion rate was 62%.
It showed the same activity or life as the new catalyst.

COMPARATIVE EXAMPLE 1 40 g of a microsphere fluidized bed catalyst having an average particle size of 60 μm and consisting of 75% by weight of chromia and 25% by weight of silica were charged into a glass fluidized bed reactor having an inner diameter of 1 inch. The spent catalyst obtained by the reaction in the same manner as in Example 1 was extracted, and Cu (NO ₃ ) _2.
3.78 g of H ₂ O, 1.56 g of KNO ₃ , La (NO ₃ ) _2.
After impregnation in 27 ml of an aqueous solution of 5.32 g of 6H ₂ O,
It was baked at 420 ° C. for 5 hours. 40 g of this regenerated catalyst was reacted in the same manner as described above. The conversion of hydrogen chloride was 75% on the third day of the reaction, 66% on the 30th day of the reaction, and 56% on the 65th day.

Comparative Example 2 Average particle composed of 75% by weight of chromia and 25% by weight of silica
40 g of microsphere fluidized bed catalyst with a diameter of 60 µ
Into a glass fluidized bed reactor. As in the first embodiment
The spent catalyst obtained by the reaction was extracted, and Co was added to the spent catalyst.
(NO_Three)_Two・ 6H _Two27 ml of an aqueous solution containing 5.92 g of O
After immersion, the mixture was fired at 420 ° C. for 5 hours. This regenerated catalyst 4
0 g was reacted as described above. Day 3 of reaction start
The conversion of hydrogen chloride is 55%, and there is no improvement in the conversion
Was.

Example 3 Average particle composed of 75% by weight of chromia and 25% by weight of silica
40 g of microsphere fluidized bed catalyst with a diameter of 60 µ
Into a glass fluidized bed reactor. As in the first embodiment
The spent catalyst obtained by the reaction was extracted, and Cu was added to the spent catalyst.
(NO_Three)_Two・ 3H _Two3.78 g of O, KNO_Three1.56g, L
a (NO_Three)_Two・ 6H_TwoAn aqueous solution 20 in which 5.32 g of O is dissolved
After impregnation, the mixture was fired at 420 ° C. for 5 hours. Then Co
(NO_Three)_Two・ 6H_Two7.4m of an aqueous solution in which 5.92g of O is dissolved
After the impregnation, the mixture was fired at 420 ° C. for 5 hours. This regenerated catalyst
40 g were reacted as described above. Day 3 of reaction start
The conversion of hydrogen chloride was 78%. 30 days after the start of the reaction
The conversion rate was 70%, and the conversion rate was 68% on the 65th day.
And showed an activity and life equivalent to or higher than that of the new catalyst.

Example 4 Average particle composed of 75% by weight of chromia and 25% by weight of silica
40 g of microsphere fluidized bed catalyst with a diameter of 60 µ
Into a glass fluidized bed reactor. As in the first embodiment
The spent catalyst obtained by the reaction was extracted, and Cu was added to the spent catalyst.
(NO_Three)_Two・ 3H _Two15.17 g, KNO_Three6.24 g,
La (NO_Three)_Two・ 6H_TwoO.64 g and Co (N
O_Three)_Two・ 6H_Two50.0 ml of an aqueous solution containing 5.92 g of O
And baked at 420 ° C. for 5 hours. This regenerated catalyst 4
0 g was reacted as described above. Day 3 of reaction start
The conversion of hydrogen chloride was 80%. 30 days after the start of the reaction
Shows a conversion rate of 72%. On the 65th day, the conversion rate is 70%.
And showed activity and life equivalent to or better than the new catalyst.

Comparative Example 3 Average particle composed of 75% by weight of chromia and 25% by weight of silica
40 g of microsphere fluidized bed catalyst with a diameter of 60 µ
Into a glass fluidized bed reactor. As in the first embodiment
The spent catalyst obtained by the reaction was extracted, and Cu was added to the spent catalyst.
(NO_Three)_Two・ 3H _Two15.17 g, KNO_Three6.24 g,
La (NO_Three)_Two・ 6H_TwoAn aqueous solution in which 10.64 g of O is dissolved
After impregnation with 50.0 ml, it was baked at 420 ° C. for 5 hours. This
Was reacted in the same manner as described above. reaction
The conversion of hydrogen chloride on the third day after the start was 79%. reaction
On the 30th day, the conversion rate was 71%, and on the 65th day, the conversion rate was 71%.
Conversion rate is 69%, and the activity and service life are equal to or higher than that of the new catalyst.
As shown, the catalyst fluidity tends to decrease slightly from the 30th day.
It was observed.

[0036]

According to the method of the present invention, a conventionally known chromium oxide-based catalyst which has been used for a long period of time in the oxidation reaction of hydrogen chloride and has reduced activity can be used as a catalyst for copper, alkali metals, rare earth metals, and copper. Impregnated with a solution containing a transition metal other than
Activation and regeneration can be performed by firing at a temperature of 00 ° C or less. The regenerated catalyst thus obtained has high activity and good catalyst fluidity, and has the same performance as the new catalyst in a long-term life test.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Kunihiro Yamada, Inventor: 30 Asamuta-cho, Omuta-shi, Fukuoka Prefecture Mitsui Toatsu Chemical Co., Ltd.

Claims (4)

[Claims] (1) When regenerating a catalyst containing chromium oxide as a main component used in producing chlorine by oxidizing hydrogen chloride with an oxygen-containing gas, copper, an alkali metal, a rare earth metal,
And a catalyst containing a transition metal other than copper. 2. The method according to claim 1, wherein the alkali metal is potassium. 3. The method according to claim 1, wherein the rare earth metal is lanthanum. 4. The method according to claim 1, wherein the transition metal other than copper is cobalt.