KR101925641B1 - Method of producing catalyst used in the production of methacrylic acid and method of producing methacrylic acid - Google Patents

Abstract

The present invention relates to a process for producing a catalyst for the production of methacrylic acid comprising a heteropoly acid compound containing phosphorus and molybdenum, characterized in that the catalyst precursor is calcined at 360 to 410 캜 under a gas atmosphere containing 0.1% by volume or more and less than 2.0% A first firing step; A second firing step of further firing the fired product obtained in the first firing step at 420 to 500 DEG C under a non-oxidative gas atmosphere; And a step of cooling the fired product obtained in the second firing step so as to be 280 DEG C or lower in a non-oxidizing gas atmosphere.

Description

TECHNICAL FIELD The present invention relates to a method for producing methacrylic acid,

The present invention relates to a process for preparing a catalyst for the production of methacrylic acid, and also relates to a process for producing methacrylic acid using the catalyst obtained by this process.

The present application claims priority based on Japanese Patent Application No. 2011-116925 filed on May 25, 2011, the contents of which are incorporated herein by reference.

Conventionally, it has been known that a catalyst used when methacrylic acid is produced by a gas-phase catalytic oxidation reaction such as methacrolein includes heteropoly acids including phosphorus and molybdenum and salts thereof. This catalyst is usually produced by drying an aqueous mixture containing a raw material of a catalyst and then firing the mixture. Patent Literatures 1 to 5 describe the firing method.

Patent Document 1 discloses a method of firing at 400 to 500 캜 under an atmosphere of non-oxidizing gas and then firing at 300 to 400 캜 in an atmosphere of an oxidizing gas. Patent Document 2 discloses a method of firing at 360 to 410 캜 under an atmosphere of an oxidizing gas or a non-oxidizing gas, then firing at 420 to 500 캜 under an atmosphere of non-oxidizing gas, and then firing at 300 to 400 캜 in an oxidizing gas atmosphere . Patent Document 3 discloses a method for manufacturing a semiconductor device which comprises firing at 300 to 400 캜 under an atmosphere of an oxidizing gas containing 10% by volume or less of water and then firing at 400 to 500 캜 under an atmosphere of non-oxidizing gas, In an atmosphere of an oxidizing gas at a temperature of 300 to 400 캜. Patent Document 4 discloses a method of firing at 300 to 400 캜 under an atmosphere of oxidizing gas, followed by firing at 400 to 500 캜 under an atmosphere of non-oxidizing gas, and then cooling to 280 캜 or less while keeping the atmosphere of non-oxidizing gas have. Patent Document 5 discloses a method in which the first step is fired at 300 to 400 캜 under an atmosphere of an oxidizing gas and then the temperature is raised to 420 캜 or higher in an atmosphere of non-oxidizing gas containing 0.1 to 10% by volume of water, At a temperature of 420 to 500 占 폚.

Japanese Patent Laid-Open No. 2004-188231 Japanese Patent Application Laid-Open No. 2005-21727 Japanese Patent Application Laid-Open No. 2005-131577 Japanese Patent Application Laid-Open No. 2007-90193 Japanese Patent Application Laid-Open No. 2008-284508

However, the catalyst for the production of methacrylic acid obtained by the conventional method is not necessarily satisfactory in terms of catalytic activity and catalyst life.

It is an object of the present invention to provide a method for producing a catalyst for producing methacrylic acid having excellent catalytic activity and catalyst life. It is another object of the present invention to provide a method for producing methacrylic acid stably over a long period of time by using a catalyst prepared by this method and dialing the raw material at a good conversion rate.

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found a solution including the following constitution, and have completed the present invention.

(1) A process for producing a catalyst for producing methacrylic acid, comprising a heteropoly acid compound containing phosphorus and molybdenum,

A first calcination step of calcining the catalyst precursor at 360 to 410 캜 under a gas atmosphere containing 0.1% by volume or more and less than 2.0% by volume of water;

A second firing step of further firing the fired product obtained in the first firing step at 420 to 500 DEG C under a non-oxidative gas atmosphere; And

A step of cooling the fired product obtained in the second firing step so as to be 280 DEG C or less in an atmosphere of non-

Wherein the catalyst is a catalyst for producing methacrylic acid.

(2) the heteropoly acid compound is

Vanadium;

At least one element selected from the group consisting of potassium, rubidium, cesium and thallium;

At least one element selected from the group consisting of copper, arsenic, antimony, boron, silver, bismuth, iron, cobalt, lanthanum and cerium

(1). ≪ / RTI >

(3) The method according to (1) or (2), wherein the catalyst precursor is calcined for 1 to 20 hours in the first calcination step.

(4) The method according to any one of (1) to (3), wherein the fired product obtained in the first firing step is fired in the second firing step for 1 to 20 hours.

(5) The method according to any one of (1) to (4), wherein the non-oxidizing gas is at least one selected from the group consisting of nitrogen, argon, helium and carbon dioxide.

(6) A process for producing methacrylic acid, which comprises reacting, in the presence of a catalyst for the production of methacrylic acid obtained by the production process according to any one of (1) to (5), at least one selected from the group consisting of methacrolein, isobutyl aldehyde, isobutane and isobutyric acid A method for producing methacrylic acid, characterized in that one kind of compound is provided in a vapor phase catalytic oxidation reaction.

According to the present invention, the effect of obtaining a catalyst for producing methacrylic acid having excellent catalytic activity and catalyst life is obtained. Further, by using this catalyst, it is possible to produce methacrylic acid stably over a long period of time by dialing the raw material at a good conversion rate.

The catalyst for the production of methacrylic acid obtained by the production process of the present invention includes a heteropoly acid compound including phosphorus and molybdenum. Such a heteropoly acid compound may include free heteropoly acid or may include a salt of heteropoly acid. Among them, it is preferable to include an acidic salt (partially neutralized salt) of heteropoly acid, more preferably an acid salt of keggin-type heteropoly acid.

The heteropoly acid compound may contain other elements as long as it does not impair the catalytic activity, as long as it contains phosphorus and molybdenum as essential elements. Examples of the other element include vanadium, potassium, rubidium, cesium, thallium, copper, arsenic, antimony, boron, silver, bismuth, iron, cobalt, lanthanum and cerium. For example, the heteropoly acid compound preferably contains the following elements.

sign;

molybdenum;

vanadium;

At least one element selected from the group consisting of potassium, rubidium, cesium and thallium (hereinafter sometimes referred to as " X element "); And

At least one element selected from the group consisting of copper, arsenic, antimony, boron, silver, bismuth, iron, cobalt, lanthanum and cerium (hereinafter sometimes referred to as "Y element").

In particular, the heteropoly acid compound preferably contains phosphorus, vanadium, X element and Y element in a proportion of not more than 3 atoms, respectively, per 12 atoms of molybdenum.

The method for producing the catalyst for the production of methacrylic acid according to the present invention (hereinafter sometimes referred to as " the production method of the present invention ") includes the first firing step, the second firing step and the cooling step as described above.

(First firing step)

The first firing step is a step of firing the catalyst precursor at 360 to 410 캜 under a gas atmosphere containing 0.1% by volume or more and less than 2.0% by volume of water.

The catalyst precursor is a mixture of compounds containing each element contained in the catalyst for producing methacrylic acid. Examples of such compounds include oxo acids, oxo acids, oxides, nitrates, carbonates, bicarbonates, hydroxides, and halides of the respective elements. Examples of the phosphorus-containing compound include phosphoric acid, phosphate and the like. Examples of the compound containing molybdenum include molybdic acid, molybdate, molybdenum oxide, molybdenum chloride and the like. Examples of the vanadium-containing compound include vanadium acid, vanadium acid, vanadium oxide, and vanadium chloride. Examples of the compound containing the X element include oxides, nitrates, carbonates, bicarbonates, hydroxides, halides and the like. Examples of the compound containing the Y element include oxo acid, oxo acid salt, nitrate salt, carbonate, hydroxide, halide and the like.

This catalyst precursor is usually obtained by mixing the above compound with water to prepare an aqueous solution or suspension, and drying these aqueous solutions or suspensions. Drying may include spray drying using a spray dryer. Normally, the dried material is molded into a desired shape (e.g., a cylindrical shape, a spherical shape, a ring shape, or the like), and a molding assistant may be used at the time of molding at need. The obtained molded article is preferably subjected to heat treatment (preliminary firing) at a temperature of about 180 to 300 DEG C in an atmosphere of an oxidizing gas or a non-oxidizing gas. Further, after the dried material is subjected to heat treatment (preliminary firing), molding may be performed.

In preparing the above aqueous solution or suspension, it is preferable to further add ammonia or an ammonium salt to prepare an aqueous solution or suspension containing ammonium radicals. Instead of adding ammonia or an ammonium salt, an ammonium compound may be used for at least one of the above compounds including phosphorus, molybdenum, vanadium, X element or Y element. In the case of such a formulation, a catalyst precursor containing a non-keratinized heteropoly acid salt is obtained as a dried product, and a heat treatment (preliminary calcination) is performed to cause a transition reaction from a bike to a keel type, Can be obtained.

The obtained catalyst precursor is calcined at 360 to 410 캜 under a gas atmosphere containing less than 0.1% by volume and less than 2.0% by volume of water. The production method of the present invention is not particularly limited as long as it is a gas containing a specific amount of water. Examples of the gas include an oxidizing gas (air, oxygen, etc.), a non-oxidizing gas (inert gas (nitrogen, argon, helium, neon etc.), a reducing gas (carbon dioxide, hydrogen, ammonia etc.) , Argon, helium, and carbon dioxide are preferable, and nitrogen and air are more preferable. These gases may be used alone, or two or more of them may be used in combination.

The gas contains less than 0.1% by volume and less than 2.0% by volume of water. By including moisture in a specific range, the catalytic activity and catalyst life of the obtained catalyst can be effectively improved. The water content is preferably contained in a ratio of 0.8 to 1.8% by volume.

The first firing is performed at 360 to 410 캜. By performing the first calcination at 360 to 410 캜, the catalytic activity and catalyst life of the obtained catalyst can be effectively improved. The first firing is preferably performed at 380 to 400 캜.

The first firing is preferably performed for 1 to 20 hours, more preferably for 1 to 5 hours. By performing the first firing for 1 to 20 hours, firing is sufficiently performed regardless of the composition of the catalyst precursor.

Thus, the sintered body obtained in the first sintering step is provided in the second sintering step.

(Second firing step)

The second firing step is a step of further firing the fired product obtained in the first firing step at 420 to 500 DEG C under a non-oxidizing gas atmosphere.

The non-oxidizing gas used in the second firing process includes the above-described non-oxidizing gas (inert gas (nitrogen, argon, helium, neon, etc.), reducing gas (carbon dioxide, hydrogen, ammonia, etc.) The non-oxidizing gas used in the second baking step is preferably a non-oxidizing gas such as nitrogen, argon, helium and carbon dioxide, and more preferably nitrogen. The non-oxidizing gas may be used alone or in combination of two or more. Whether or not water is included, dry gas which does not contain moisture is preferable, though it does not matter whether it contains water or not.

The second firing is performed at 420 to 500 ° C. By performing the second calcination at 420 to 500 ° C, the catalytic activity and the catalyst life of the obtained catalyst can be effectively improved. The second firing is preferably performed at 430 to 440 캜.

The second firing is preferably performed for 1 to 20 hours, more preferably for 1 to 5 hours. The second firing is performed for 1 to 20 hours, whereby firing is sufficiently performed regardless of the composition of the catalyst precursor.

The fired product obtained in the second firing step is supplied to the cooling step.

(Cooling process)

The cooling step is a step of cooling the fired product obtained in the second firing step so as to be 280 DEG C or lower in a non-oxidizing gas atmosphere.

The non-oxidizing gas used in the cooling process includes the above-described non-oxidizing gas (inert gas (nitrogen, argon, helium, neon etc.), reducing gas (carbon dioxide, hydrogen, ammonia, etc.) The non-oxidizing gas used in the cooling process is preferably a gas which uses the same gas as the non-oxidizing gas used in the second firing step (that is, the second firing step), that is, The non-oxidizing gas used in the cooling step may be used alone or in combination of two or more. The non-oxidizing gas used in the cooling step may or may not contain moisture. However, it is preferable to use a dry gas containing no moisture.

The cooling is performed so as to be 280 DEG C or lower, preferably 250 DEG C or lower. By not being exposed to the oxidizing gas at a high temperature exceeding 280 DEG C, the catalytic activity and the catalyst life can be effectively improved.

(Method for producing methacrylic acid)

The catalyst for the production of methacrylic acid obtained by the production method of the present invention has excellent catalytic activity and catalyst life. By using the catalyst for the production of methacrylic acid, for example, raw material compounds such as methacrolein, isobutylaldehyde, isobutane, isobutyric acid and the like are subjected to a gas phase catalytic oxidation reaction, The acid can be stably produced over a long period of time.

The production of methacrylic acid is generally carried out by charging a catalyst in a fixed-bed multitubular reactor and supplying a gas containing a raw material compound and oxygen to the reactor. Also, a fluidized bed or a moving bed form can be employed instead of the stationary bed. As the gas containing oxygen, generally air or pure oxygen is used. Nitrogen, carbon dioxide, carbon monoxide, water vapor, or the like may be supplied to the reactor in addition to the gas containing oxygen and the raw material compound.

When methacrolein is used as the raw material compound, the reaction is preferably carried out under the following conditions. The space velocity is obtained by dividing the feed rate (L / h) of raw material (raw compound and other gas) per hour passing through the reactor by the catalyst capacity (L) in the reactor.

Concentration of methacrolein in the raw material: 1 to 10%

Concentration of water vapor in the raw material: 1 to 30%

Molar ratio of methacrolein to oxygen: 1/1 to 1/5 (methacrolein / oxygen)

Space velocity: 500 to 5000 h ^-1 (standard condition)

Reaction temperature: 250 to 350 DEG C

Reaction pressure: 0.1 to 0.3 MPa

When isobutane is used as the raw material compound, the reaction is preferably carried out under the following conditions.

Concentration of isobutane in the raw material: 1 to 85%

Concentration of water vapor in the raw material: 3 to 30%

Mole ratio of isobutane and oxygen: 1 / 0.05 to 1/4 (isobutane / oxygen)

Space velocity: 400 to 5000 h ^-1 (standard condition)

Reaction temperature: 250 to 400 DEG C

Reaction pressure: 0.1 to 1 MPa

When isobutylaldehyde and / or isobutyric acid is used as the raw material, the reaction is carried out under substantially the same conditions as those in the case of using methacrolein as the raw material. In addition, these raw material compounds do not need to be refined high-purity products. For example, in the case of methacrolein, methacrolein obtained by gas-phase catalytic oxidation of isobutylene or t-butyl alcohol may be used while remaining unmodified.

<Examples>

Hereinafter, the present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited to these examples. In addition, the nitrogen used in each of the Examples and Comparative Examples is substantially free from moisture.

(Preparation Example 1: Preparation of Catalyst Precursor)

First, each of the following materials was mixed to prepare solutions A and B.

&Lt; Solution A >

Ion exchanged water (40 ° C): 224 kg

Cesium nitrate (CsNO ₃ ): 38.2 kg

Ortho phosphoric acid (85% by weight product): 24.2 kg

Nitric acid (70% by weight): 25.2 kg

<Solution B (Suspension)>

Ion exchanged water (40 캜): 330 kg

Ammonium molybdate tetrahydrate ((NH ₄ ) ₆ Mo ₇ O ₂₄ .4H ₂ O): 297 kg

Meta vanadium ammonium _{(NH 4 VO 3): 8.19} kg

Then, Solution A was added dropwise to Solution B while stirring. After the dropwise addition, the mixture was stirred at 120 deg. C for 5.8 hours in a sealed vessel. Subsequently, 10.2 kg of antimony trioxide (Sb ₂ O ₃ ) and 10.2 kg of copper nitrate trihydrate (Cu (NO ₃ ) ₂ .3H ₂ O) were suspended in 23 kg of ion-exchanged water, And further stirred at 120 ° C for 5 hours.

The resulting slurry was spray-dried with a spray drier, and 4 parts by weight of ceramic fiber (SiO ₂ -Al ₂ O ₃ based, fiber diameter of 2 to 4 μm, fiber average length of 400 μm) and 13 parts by weight of nitric acid Ammonium, and 9.7 parts by weight of ion-exchanged water were added, kneaded, and extrusion-molded into a cylindrical shape (diameter: 5 mm, height: 6 mm). Subsequently, the obtained molded body was dried for 3 hours under an atmosphere of a temperature of 90 DEG C and a humidity of 30% RH. The obtained dried product was subjected to a heat treatment (preliminary calcination) for 22 hours in an air stream at 220 ° C and then at 250 ° C for 1 hour to obtain a prefired catalyst precursor containing a keel type heteropolyacid salt.

(Example 1)

The catalyst precursor obtained in Preparation Example 1 was maintained at 390 占 폚 for 3 hours in a gas stream of air and steam (water content: 1.0% by volume) (first shortening). Subsequently, the mixed gas of air and steam was changed to nitrogen and maintained at 435 DEG C for 3 hours in a nitrogen stream (second shortening). After the second short firing, the fired product was cooled to 70 DEG C in a stream of nitrogen and taken out into the atmosphere. The obtained fired product (Catalyst 1) was an acidic salt of ketene type heteropoly acid including phosphorus (1.5), molybdenum (12), vanadium (0.5), antimony (0.5), copper (0.3) and cesium (1.4). The numerical values in parentheses are atomic ratios.

(Example 2)

A fired product (catalyst 2) was obtained in the same manner as in Example 1 except that the water content was 1.4% by volume in the first short firing.

(Example 3)

In the first short firing, a fired product (catalyst 3) was obtained in the same manner as in Example 1 except that the water content was adjusted to 1.8% by volume.

(Example 4)

A fired product (catalyst 4) was obtained in the same manner as in Example 1 except that in the first short firing, a mixed gas of nitrogen and steam (water content: 1.8% by volume) was used instead of the mixed gas of air and steam.

(Comparative Example 1)

A fired product (catalyst 5) was obtained in the same manner as in Example 1 except that in the first short firing, air alone (water content: 0.0% by volume) was used instead of air and steam mixture gas.

(Comparative Example 2)

A fired product (catalyst 6) was obtained in the same manner as in Example 1, except that the first short firing was performed with nitrogen only (water content: 0.0% by volume) instead of air and steam mixed gas.

(Comparative Example 3)

A fired product (catalyst 7) was obtained in the same manner as in Example 1, except that the water content in the first short firing was 2.8% by volume.

(Comparative Example 4)

In the first short firing, a fired product (Catalyst 8) was obtained in the same procedure as in Example 1, except that the water content was adjusted to 3.5% by volume.

(Comparative Example 5)

A fired product (Catalyst 9) was obtained in the same manner as in Example 1, except that the water content was adjusted to 4.0% by volume in the first firing.

The catalysts (Catalysts 1 to 9) obtained in each of the Examples and Comparative Examples were subjected to the activity test of the catalyst by the following methods.

(Activity test of catalyst)

9 g of the obtained catalyst was weighed and charged into a glass microreactor having an inner diameter of 16 mm, and the furnace temperature (the temperature of the furnace for heating the microreactor) was raised to 280 ° C. Then, the methacrolein, air, a raw material gas prepared by mixing nitrogen and water vapor (4 vol.% Of methacrolein, molecular oxygen 12 volume%, water vapor 17 volume%, nitrogen 67% by volume), of 670 h ^-1 Was fed into the microreactor at a space velocity and the reaction was initiated. One hour after the start of the reaction, the outflow gas (gas after the reaction) from the outlet of the microreactor was sampled and analyzed by gas chromatography, and the methacrolein conversion rate was calculated based on the following equation (1).

here,

A is the number of moles of methacrolein reacted.

B is the number of moles of methacrolein supplied.

Then, the furnace temperature was raised to 355 DEG C, the raw material gas was supplied at the space velocity (670 h &lt; ^-1 &gt;), and the reaction was performed for 1 hour to forcibly degrade the catalyst. The furnace temperature was set to 280 DEG C again, and the raw material gas was supplied to the deteriorated catalyst at the space velocity (670 h &lt; ^-1 &gt;) to initiate the reaction. One hour after the start of the reaction, the outflow gas (gas after the reaction) from the outlet of the microreactor was sampled and analyzed by gas chromatography in the same manner as above to obtain the methacrolein conversion rate. Table 1 shows the conversion of methacrolein before and after forced deterioration of each catalyst (Catalysts 1 to 9).

As shown in Table 1, the catalysts (Catalysts 1 to 4) obtained in Examples 1 to 4 exhibited a higher methacrolein conversion rate even after forced deterioration as compared with the catalysts obtained in Comparative Examples 1 to 5 (Catalysts 5 to 9) And methacrylic acid can be produced over a long period of time at a good conversion rate.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit of the present invention. The present invention is not limited by the above description, but is limited only by the appended claims.

Claims (6)

A process for producing a catalyst for the production of methacrylic acid comprising a heteropoly acid compound containing phosphorus and molybdenum,
A first firing step of firing the catalyst precursor at 360 to 410 캜 under a gas atmosphere containing 0.8 to 1.8% by volume of water;
A second firing step of further firing the fired product obtained in the first firing step at 420 to 500 DEG C under a non-oxidative gas atmosphere; And
A step of cooling the fired product obtained in the second firing step so as to be 280 DEG C or less in an atmosphere of non-
Wherein the catalyst is a catalyst for producing methacrylic acid. The method according to claim 1, wherein the heteropoly acid compound
Vanadium;
At least one element selected from the group consisting of potassium, rubidium, cesium and thallium;
At least one element selected from the group consisting of copper, arsenic, antimony, boron, silver, bismuth, iron, cobalt, lanthanum and cerium
&Lt; / RTI &gt; The method according to claim 1, wherein the catalyst precursor is calcined for 1 to 20 hours in a first calcination step. The method according to claim 1, wherein the baked material obtained in the first baking step is baked in the second baking step for 1 to 20 hours. The method according to claim 1, wherein the non-oxidizing gas is at least one selected from the group consisting of nitrogen, argon, helium, and carbon dioxide. A process for producing methacrylic acid according to any one of claims 1 to 5, wherein at least one kind selected from the group consisting of methacrolein, isobutyl aldehyde, isobutane and isobutyric acid Wherein the compound is subjected to a gas-phase catalytic oxidation reaction.