JP5793345B2 - Method for producing catalyst for producing methacrylic acid and method for producing methacrylic acid - Google Patents

Description

  The present invention relates to a method for producing a catalyst for producing methacrylic acid, and further relates to a method for producing methacrylic acid using a catalyst obtained by this method.

  Conventionally, it has been known that a catalyst comprising a heteropolyacid containing phosphorus and molybdenum or a salt thereof is effective as a catalyst used in producing methacrylic acid by a gas phase catalytic oxidation reaction such as methacrolein. This catalyst is usually produced by drying and then calcining an aqueous mixture containing the catalyst raw material. Patent Documents 1 to 5 describe this firing method.

  Patent Document 1 discloses that after firing at 400 to 500 ° C. in a non-oxidizing gas atmosphere, firing is performed at 300 to 400 ° C. in an oxidizing gas atmosphere. In Patent Document 2, after firing at 360 to 410 ° C. in an atmosphere of oxidizing gas or non-oxidizing gas, firing is performed at 420 to 500 ° C. in atmosphere of non-oxidizing gas, and then in the atmosphere of oxidizing gas. A method of firing at 300-400 ° C. is disclosed. In Patent Document 3, after baking at 300 to 400 ° C. in an atmosphere of oxidizing gas containing 10% by volume or less of moisture, baking is performed at 400 to 500 ° C. in an atmosphere of non-oxidizing gas, and then 30% by volume or less. Discloses a method of baking at 300 to 400 ° C. in an atmosphere of an oxidizing gas containing water. In Patent Document 4, after baking at 300 to 400 ° C. in an oxidizing gas atmosphere, baking is performed at 400 to 500 ° C. in a non-oxidizing gas atmosphere, and then in the non-oxidizing gas atmosphere at 280 ° C. The cooling method is disclosed below. In Patent Document 5, first-stage firing is performed at 300 to 400 ° C. in an oxidizing gas atmosphere, and then the temperature is raised to 420 ° C. or more in a non-oxidizing gas atmosphere containing 0.1 to 10% by volume of water. After that, a second-stage firing method is disclosed at 420 to 500 ° C. in a non-oxidizing gas atmosphere.

JP 2004-188231 A JP 2005-21727 A JP-A-2005-131577 JP 2007-90193 A JP 2008-284508 A

However, the methacrylic acid production catalyst obtained by the conventional method is not always satisfactory in terms of catalyst activity and catalyst life.
The subject of this invention is providing the method of manufacturing the catalyst for methacrylic acid manufacture which has the outstanding catalyst activity and catalyst lifetime. Another object of the present invention is to provide a method for producing methacrylic acid stably over a long period of time by converting a raw material at a good conversion rate using a catalyst produced by this method.

As a result of intensive studies to solve the above problems, the present inventors have found a solution means having the following configuration, and have completed the present invention.
(1) A method for producing a catalyst for producing methacrylic acid comprising a heteropolyacid compound containing phosphorus and molybdenum,
A first calcining step of calcining the catalyst precursor at 360 to 410 ° C. in a gas atmosphere containing moisture of 0.1% by volume or more and less than 2.0% by volume;
A second firing step of further firing the fired product obtained in the first firing step at 420 to 500 ° C. in a non-oxidizing gas atmosphere; and a fired product obtained in the second firing step. A step of cooling to 280 ° C. or lower in an oxidizing gas atmosphere;
A process for producing a catalyst for producing methacrylic acid, comprising:
(2) The heteropolyacid compound further comprises:
With 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;
The method as described in (1) characterized by including.
(3) The method according to (1) or (2), wherein the catalyst precursor is calcined for 1 to 20 hours in the first calcining step.
(4) The method according to any one of (1) to (3), wherein the fired product obtained in the first firing step is fired for 1 to 20 hours in the second firing step.
(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) selected from the group consisting of methacrolein, isobutyraldehyde, isobutane and isobutyric acid in the presence of the catalyst for producing methacrylic acid obtained by the production method according to any one of (1) to (5) A method for producing methacrylic acid, comprising subjecting at least one kind of compound to a gas phase catalytic oxidation reaction.

  According to the present invention, there is an effect that a catalyst for producing methacrylic acid having excellent catalytic activity and catalyst life can be obtained. Furthermore, when this catalyst is used, the raw material can be converted at a good conversion rate, and methacrylic acid can be produced stably over a long period of time.

  The catalyst for methacrylic acid production obtained by the production method of the present invention comprises a heteropolyacid compound containing phosphorus and molybdenum. Such a heteropolyacid compound may be composed of a free heteropolyacid or a salt of a heteropolyacid. Among these, what consists of acidic salt (partially neutralized salt) of heteropolyacid is preferable, and what consists of acidic salt of Keggin type heteropolyacid is more preferable.

As long as the heteropolyacid compound contains phosphorus and molybdenum as essential elements, it may contain other elements as long as the catalytic activity is not inhibited. Examples of other elements include vanadium, potassium, rubidium, cesium, thallium, copper, arsenic, antimony, boron, silver, bismuth, iron, cobalt, lanthanum, and cerium. For example, the heteropolyacid compound preferably contains the following elements.
Rin;
molybdenum;
vanadium;
At least one element selected from the group consisting of potassium, rubidium, cesium and thallium (hereinafter sometimes referred to as “element X”); and copper, arsenic, antimony, boron, silver, bismuth, iron, cobalt , At least one element selected from the group consisting of lanthanum and cerium (hereinafter sometimes referred to as “Y element”).

  In particular, the heteropolyacid compound preferably contains phosphorus, vanadium, an X element and a Y element at a ratio of 3 atoms or less to 12 atoms of molybdenum.

  The method for producing a catalyst for producing 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 ° C. in a gas atmosphere containing moisture of 0.1 volume% or more and less than 2.0 volume%.

  The catalyst precursor is a mixture of compounds containing each element contained in the methacrylic acid production catalyst. Examples of such compounds include oxo acids, oxo acid salts, oxides, nitrates, carbonates, bicarbonates, hydroxides, halides and the like of each element. For example, phosphoric acid, a phosphate, etc. are mentioned as a compound containing phosphorus. Examples of the compound containing molybdenum include molybdic acid, molybdate, molybdenum oxide, and molybdenum chloride. Examples of the compound containing vanadium include vanadic acid, vanadate, vanadium oxide, and vanadium chloride. Examples of the compound containing X element include oxides, nitrates, carbonates, bicarbonates, hydroxides, halides, and the like. Examples of the compound containing the Y element include oxo acids, oxo acid salts, nitrates, carbonates, hydroxides, halides, and the like.

  This catalyst precursor is usually obtained by mixing the above compound with water to form an aqueous solution or suspension, and drying these aqueous solutions or suspensions. Examples of the drying include spray drying using a spray dryer. Usually, the dried product is formed into a desired shape (for example, a columnar shape, a spherical shape, a ring shape, etc.), and a forming aid may be used as necessary at the time of forming. The obtained molded body is preferably subjected to heat treatment (pre-baking) at a temperature of about 180 to 300 ° C. in an oxidizing gas or non-oxidizing gas atmosphere. In addition, you may shape | mold after heat-processing (pre-baking) to a dried material.

  When preparing the aqueous solution or suspension, it is preferable to further add ammonia or an ammonium salt to obtain an aqueous solution or suspension containing an ammonium root. Instead of adding ammonia or an ammonium salt, an ammonium compound may be used for at least one of the above compounds containing phosphorus, molybdenum, vanadium, X element or Y element. In the case of such a formulation, a catalyst precursor composed of a non-Keggin type heteropolyacid salt is obtained as a dried product, and by performing a heat treatment (pre-calcination), a transition reaction from the non-Keggin type to the Keggin type occurs. A catalyst precursor comprising a type heteropolyacid salt can be obtained.

  The obtained catalyst precursor is calcined at 360 to 410 ° C. in a gas atmosphere containing moisture of 0.1 volume% or more and less than 2.0 volume%. In the manufacturing method of this invention, if it is a gas containing a specific amount of water | moisture content, it will not specifically limit. Such gases include oxidizing gases (air, oxygen, etc.), non-oxidizing gases (inert gases (nitrogen, argon, helium, neon, etc.), reducing gases (carbon dioxide, hydrogen, ammonia, etc.), etc.) Etc. Among these, nitrogen, air, argon, helium and carbon dioxide are preferable, and nitrogen and air are more preferable. These gases may be used alone or in combination of two or more.

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

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

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

  Thus, the fired product obtained in the first firing step is subjected to the second firing 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 ° C. in a non-oxidizing gas atmosphere.

  Examples of the non-oxidizing gas used in the second firing step include the above-described non-oxidizing gases (inert gases (nitrogen, argon, helium, neon, etc.), reducing gases (carbon dioxide, hydrogen, ammonia, etc.), etc.) Can be mentioned. Among these non-oxidizing gases, nitrogen, argon, helium and carbon dioxide are preferable, and nitrogen is more preferable. A non-oxidizing gas may be used independently and may use 2 or more types together. The non-oxidizing gas used in the second firing step may or may not contain moisture, but is preferably a dry gas that does not contain moisture.

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

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

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

(Cooling process)
The cooling step is a step of cooling the fired product obtained in the second firing step to 280 ° C. or lower in a non-oxidizing gas atmosphere.

  Examples of the non-oxidizing gas used in the cooling step include the above-mentioned non-oxidizing gases (inert gases (nitrogen, argon, helium, neon, etc.), reducing gases (carbon dioxide, hydrogen, ammonia, etc.), etc.). . Among these non-oxidizing gases, nitrogen, argon, helium and carbon dioxide are preferable, and nitrogen is more preferable. The non-oxidizing gas used in the cooling step is the same as the non-oxidizing gas used in the second firing step from the viewpoint of workability (that is, the non-oxidizing gas used in the second firing step is used as it is). Preferably used). A non-oxidizing gas may be used independently and may use 2 or more types together. The non-oxidizing gas used in the cooling step may or may not contain moisture, but is preferably a dry gas that does not contain moisture.

  Cooling is performed so that it may become 280 degrees C or less, Preferably it is performed so that it may become 250 degrees C or less. By preventing exposure to an oxidizing gas at a high temperature exceeding 280 ° C., the catalyst activity and the catalyst life can be effectively improved.

(Method for producing methacrylic acid)
The catalyst for methacrylic acid production obtained by the production method of the present invention has excellent catalytic activity and catalyst life. Using this methacrylic acid production catalyst, for example, by subjecting raw material compounds such as methacrolein, isobutyraldehyde, isobutane, and isobutyric acid to a gas phase catalytic oxidation reaction, the raw material compounds are converted at a good conversion rate, Methacrylic acid can be produced stably over a long period of time.

  The production of methacrylic acid is usually carried out by filling a fixed bed multitubular reactor with a catalyst and supplying a raw material compound and a gas containing oxygen to the reactor. Moreover, the form of a fluidized bed or a moving bed can be adopted instead of the fixed bed. As the gas containing oxygen, air or pure oxygen is generally used. In addition to the gas containing oxygen and the raw material compound, nitrogen, carbon dioxide, carbon monoxide, water vapor, and the like may be supplied to the reactor.

When using methacrolein as a raw material compound, the reaction is preferably carried out under the following conditions. The space velocity is obtained by dividing the supply amount (L / h) of raw materials (raw material compounds and other gases) per hour passing through the reactor by the catalyst capacity (L) in the reactor.
Concentration of methacrolein in the raw material: 1 to 10% by volume
Concentration of water vapor in raw material: 1-30% by volume
Molar ratio of methacrolein to oxygen: 1/1 to 1/5 (methacrolein / oxygen)
Space velocity: 500-5000h ^-1 (standard condition standard)
Reaction temperature: 250-350 ° C
Reaction pressure: 0.1-0.3 MPa

When isobutane is used as a starting compound, the reaction is preferably carried out under the following conditions.
Concentration of isobutane in the raw material: 1 to 85% by volume
Concentration of water vapor in raw material: 3 to 30% by volume
Molar ratio of isobutane to oxygen: 1 / 0.05 to 1/4 (isobutane / oxygen)
Space velocity: 400-5000h ^-1 (standard condition standard)
Reaction temperature: 250-400 ° C
Reaction pressure: 0.1-1 MPa

  When isobutyraldehyde and isobutyric acid are used as raw material compounds, the reaction is carried out under substantially the same conditions as when methacrolein is used as the raw material compound. Moreover, these raw material compounds do not need to be purified high-purity products. For example, in the case of methacrolein, methacrolein obtained by a gas phase catalytic oxidation reaction of isobutylene or t-butyl alcohol may be used without purification.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited to these Examples. The nitrogen used in each example and each comparative example is substantially free of moisture.

(Preparation Example 1: Preparation of catalyst precursor)
First, the following raw materials were mixed to prepare liquid A and liquid B.
<Liquid A (solution)>
Ion-exchanged water (40 ° C): 224kg
Cesium nitrate (CsNO ₃ ): 38.2 kg
Orthophosphoric acid (85% by weight product): 24.2 kg
Nitric acid (70% by weight product): 25.2kg
<Liquid B (suspension)>
Ion exchange water (40 ° C): 330 kg
Ammonium molybdate tetrahydrate ((NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O): 297 kg
Ammonium metavanadate (NH ₄ VO ₃ ): 8.19 kg

Subsequently, A liquid was dripped at B liquid, stirring. After dropping, the mixture was stirred in a sealed container at 120 ° C. for 5.8 hours. Then, 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 It added in the airtight container and stirred at 120 degreeC for further 5 hours.

The obtained slurry was spray-dried with a spray dryer, and 4 parts by weight of ceramic fiber (SiO ₂ -Al ₂ O ₃ type, fiber diameter _{2 to} 4 μm, fiber average length 400 μm with respect to 100 parts by weight of the obtained dried product. ), 13 parts by weight of ammonium nitrate, and 9.7 parts by weight of ion-exchanged water were added and kneaded and extruded into a cylindrical shape (diameter 5 mm, height 6 mm). Next, the obtained molded body was dried for 3 hours in an atmosphere of a temperature of 90 ° C. and a humidity of 30% RH. The obtained dried product was heat-treated (pre-calcined) for 22 hours in an air stream at 220 ° C. and then for 1 hour at 250 ° C. to obtain a pre-calcined catalyst precursor comprising a Keggin heteropolyacid salt.

Example 1
The catalyst precursor obtained in Preparation Example 1 was held at 390 ° C. for 3 hours in a mixed gas of air and steam (water content: 1.0% by volume) (first stage calcination). Next, the mixed gas of air and steam was changed to nitrogen, and the mixture was further maintained at 435 ° C. for 3 hours in a nitrogen stream (second stage firing). After the second stage firing, the fired product was cooled to 70 ° C. in a nitrogen stream and taken out into the atmosphere. The obtained calcined product (catalyst 1) contains phosphorus (1.5), molybdenum (12), vanadium (0.5), antimony (0.5), copper (0.3) and cesium (1.4). The acid salt of the Keggin type heteropolyacid containing The numbers in parentheses are atomic ratios.

(Example 2)
In the first stage firing, a fired product (catalyst 2) was obtained in the same procedure as in Example 1 except that the water content was 1.4% by volume.

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

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

(Comparative Example 1)
In the first stage calcination, the calcined product (catalyst 5) was prepared in the same procedure as in Example 1 except that only air (water content: 0.0% by volume) was used instead of the mixed gas of air and steam. Obtained.

(Comparative Example 2)
In the first stage calcination, the calcined product (catalyst 6) was prepared in the same procedure as in Example 1 except that instead of the mixed gas of air and steam, only nitrogen (water content: 0.0% by volume) was used. Obtained.

(Comparative Example 3)
In the first stage firing, a fired product (catalyst 7) was obtained by the same procedure as in Example 1 except that the water content was 2.8% by volume.

(Comparative Example 4)
In the first stage firing, a fired product (catalyst 8) was obtained by the same procedure as in Example 1 except that the water content was 3.5% by volume.

(Comparative Example 5)
In the first stage firing, a fired product (catalyst 9) was obtained in the same procedure as in Example 1 except that the water content was 4.0% by volume.

  About the catalyst (catalysts 1-9) obtained by each Example and each comparative example, the activity test of the catalyst was done with the following method.

(Catalyst activity test)
9 g of the obtained catalyst was weighed and filled in a glass microreactor having an inner diameter of 16 mm, and the furnace temperature (furnace temperature for heating the microreactor) was raised to 280 ° C. Subsequently, a raw material gas (4% by volume of methacrolein, 12% by volume of molecular oxygen, 17% by volume of water vapor, 67% by volume of nitrogen) prepared by mixing methacrolein, air, water vapor, and nitrogen was converted into a space velocity of 670 h ⁻¹ . Was fed into the microreactor to start the reaction. One hour after the start of the reaction, the outflow gas (gas after reaction) from the microreactor outlet was sampled and analyzed by gas chromatography, and methacrolein conversion was determined based on the following formula.
Conversion rate of methacrolein (%) = (A / B) × 100
here,
A is the number of moles of reacted methacrolein.
B is the number of moles of methacrolein supplied.

Next, the furnace temperature was raised to 355 ° C., the above raw material gas was supplied at the above space velocity (670 h ⁻¹ ), and the reaction was carried out for 1 hour to forcibly deteriorate the catalyst. Again, the furnace temperature was set to 280 ° C., and the raw material gas was supplied to the deteriorated catalyst at the space velocity (670 h ⁻¹ ) to start the reaction. One hour after the start of the reaction, the outflow gas from the microreactor outlet (the gas after the reaction) was sampled and analyzed by gas chromatography in the same manner as described above to determine the methacrolein conversion rate. Table 1 shows the methacrolein conversion rate 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 were compared with the catalysts (catalysts 5 to 9) obtained in Comparative Examples 1 to 5, even after forced deterioration. It can be seen that a high methacrolein conversion rate is maintained and methacrylic acid can be produced over a long period of time with a good conversion rate.

Claims (6)

A method for producing a methacrylic acid production catalyst comprising a heteropolyacid compound containing phosphorus and molybdenum,
A first calcining step of calcining the catalyst precursor at 360 to 410 ° C. in 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 ° C. in a non-oxidizing gas atmosphere; and a fired product obtained in the second firing step. A step of cooling to 280 ° C. or lower in an oxidizing gas atmosphere;
A process for producing a catalyst for producing methacrylic acid, comprising: The heteropolyacid compound is further
With 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;
The method of claim 1, comprising:   The method according to claim 1 or 2, wherein the catalyst precursor is calcined for 1 to 20 hours in the first calcining step.   The method according to any one of claims 1 to 3, wherein the fired product obtained in the first firing step is fired for 1 to 20 hours in the second firing step.   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.   In the presence of the catalyst for producing methacrylic acid obtained by the production method according to any one of claims 1 to 5, at least one selected from the group consisting of methacrolein, isobutyraldehyde, isobutane and isobutyric acid. A method for producing methacrylic acid, comprising subjecting a compound to a gas phase catalytic oxidation reaction.