JP2011240219A - Method for manufacturing catalyst for production of methacrylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing with good productivity, a catalyst including at least phosphorus and molybdenum and used in production of methacrylic acid by catalytic oxidation of methacrolein in a vapor phase with molecular oxygen, and to provide a method for producing methacrylic acid using the catalyst manufactured by the above method.SOLUTION: The catalyst is manufactured by calcining a catalyst precursor which includes 3-10% of organic substances and has 10% or more of a weight reduction rate when raising the temperature of the precursor from 25 to 250°C at a temperature raising rate of 10°C/min in thermogravimetry. In a process of performing final calcination of the precursor at 300 to 500°C by raising from ≤150°C, the temperature raising rate in a temperature region of from 150 to 230°C is made to be 5°C/hr to 25°C/hr, and that in the region of from 230°C to a maximum temperature in the final calcination is made to be ≥20°C/hr.

Description

  The present invention relates to a method for producing a catalyst (hereinafter referred to as a methacrylic acid production catalyst) used for producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen, and the methacrylic acid production catalyst. The present invention relates to a method for producing methacrylic acid.

  As a conventionally known method for producing methacrylic acid, there is a gas phase catalytic oxidation reaction of methacrolein, and various methods have been proposed as a method for producing a catalyst for producing methacrylic acid used in the reaction. As catalysts for the production of methacrylic acid, it is known that catalysts containing a heteropolyacid as the main active ingredient are effective. To these catalysts, organic substances are added during the production process for the purpose of molding aids and pore structure control. Often there is to do. For example, Patent Document 1 discloses a method in which an organic substance such as cellulose and polyvinyl alcohol is added to form 1 to 10% by weight and then calcined to form a catalyst. Patent Document 2 includes a nitrogen-containing organic compound such as pyridine. A method is described in which a dried product obtained by adding to a slurry is molded and then fired to form a catalyst.

  However, in the calcination of a catalyst containing an organic substance, decomposition and combustion of the organic substance occur in the calcination step, and there is a concern that the catalyst performance may be reduced such as reduction and sintering of the catalyst due to the sudden heat generation. For this reason, temperature control during the firing of the catalyst is important.

  Many proposals have been made so far regarding a method for calcining a catalyst for producing methacrylic acid. For example, Patent Document 3 discloses that when a catalyst precursor is finally calcined at 300 ° C. to 500 ° C. and activated, the final calcining is performed. A method for producing a catalyst for methacrylic acid production is described, wherein the temperature is continuously raised to a temperature and calcined at a rate of temperature rise of 200 ° C. to 265 ° C. at less than 10 ° C./hr. Patent Document 4 describes that the maximum temperature in the packed bed is set to 180 ° C. to 260 ° C. in the baking in the packed bed filled with the catalyst molded product for production of methacrylic acid containing ammonium roots. In this example, the catalyst molding was heated from room temperature to 220 ° C. at a rate of 50 ° C./hr in an air stream, further increased to 230 ° C. at a rate of 5 ° C./hr, and then 5 ° C. at 230 ° C. After holding for a time, raising the temperature to 250 ° C. in an air stream and holding at 250 ° C. for 3 hours, then raising the temperature to 435 ° C. at a rate of 50 ° C./hr in a nitrogen stream and holding at 435 ° C. for 3 hours Furthermore, a method is described in which the catalyst is obtained by firing in an air stream at 390 ° C. for 3 hours in order.

  However, the method described in Patent Document 3 has a problem that the total baking time is long and productivity is lowered. Further, in the calcination method described in Patent Document 4, catalyst deterioration due to combustion of organic substances may occur.

  In the catalyst system having a large weight loss ratio when performing thermogravimetric analysis under a certain condition containing a large amount of organic matter, the present inventors performed calcination under the conditions described in Patent Document 4, It has been found that a significant performance degradation of the catalyst occurs during calcination, and under the conditions described in Patent Document 3, the performance degradation can be prevented, but it takes time for the calcination and the productivity is lowered. As a result of intensive studies to solve this problem, it is possible to control the catalyst with high productivity without degrading the performance even in such a catalyst system by controlling the rate of temperature increase in a temperature range within a specific range in the firing process. It has been found that it can be produced, and has led to the present invention.

JP 55-73347 A JP-A-60-239439 JP 2008-272637 A JP 2003-10700 A

  The present invention uses a method for producing a catalyst for producing methacrylic acid with high productivity, which is used when producing methacrolein by vapor phase catalytic oxidation of methacrolein with molecular oxygen, and the catalyst for producing methacrylic acid. It aims at providing the manufacturing method of methacrylic acid.

The present invention is a method for producing a catalyst for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein, which contains at least phosphorus and molybdenum, and satisfies the following conditions (i) to (iii) It is a manufacturing method of the catalyst for manufacture.
(I) The catalyst precursor contains 3% to 10% of organic matter as a mass. (Ii) In the thermogravimetric analysis of the catalyst precursor, when the temperature is increased from 25 ° C. to 250 ° C. at a temperature increase rate of 10 ° C./min. (Iii) In the process of raising the temperature of the catalyst precursor satisfying the above (i) and (ii) from 150 ° C. or lower and performing final calcination at 300 ° C. to 500 ° C. The temperature increase rate in the temperature range of 270C to 230 ° C is 5 ° C / hr or more and 25 ° C / hr or less, and the temperature increase rate in the temperature range from 230 ° C to the highest temperature in the final firing is 20 ° C / hr or more.

  Moreover, this invention is a manufacturing method of the methacrylic acid which carries out the vapor phase catalytic oxidation of methacrolein with molecular oxygen using the methacrylic acid manufacturing catalyst manufactured by the said method.

  According to the present invention, a catalyst for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen can be obtained with high productivity without causing a decrease in performance.

<Catalyst preparation>
The catalyst for producing methacrylic acid produced by the method of the present invention includes an organic substance having a certain weight fraction or more in the catalyst precursor, and calcines the catalyst precursor in a specific temperature range while controlling the temperature rise rate. Manufactured by a method of calcination and activation at a temperature of from C to 500C.

  The catalyst for producing methacrylic acid produced by the method of the present invention is a catalyst for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein containing phosphorus and molybdenum with molecular oxygen, excluding organic substances contained in the catalyst. The composition is preferably represented by the following formula (1).

_{P a Mo b V c Cu d} X e Y f O g (1)
(P, Mo, V, Cu and O represent phosphorus, molybdenum, vanadium, copper and oxygen, respectively, X is iron, cobalt, nickel, zinc, magnesium, calcium, strontium, barium, titanium, chromium, tungsten, manganese At least one selected from the group consisting of silver, boron, silicon, aluminum, gallium, germanium, tin, lead, arsenic, antimony, bismuth, niobium, tantalum, zirconium, indium, sulfur, selenium, tellurium, lanthanum and cerium Y represents at least one element selected from the group consisting of potassium, rubidium and cesium, a, b, c, d, e, f and g represent the atomic ratio of each element; When b = 12, a = 0.5-3, c = 0.01-3, d = 0.01-2, e = 0-3 A f = 0.01 to 3, g is the atomic ratio of oxygen required to satisfy the valence of each component.)

  The catalyst for producing methacrylic acid produced by the method of the present invention is produced by a method in which the catalyst precursor is heat-treated at a specific temperature range while controlling the rate of temperature rise and is finally heat-treated at 300 to 500 ° C. and activated. . At this time, a solid material including all the catalyst raw materials including organic substances and before firing is referred to as a catalyst precursor.

  In the present invention, the raw materials used for the preparation of the catalyst precursor are not particularly limited, and nitrates, carbonates, acetates, ammonium salts, oxides, halides and the like of each element can be used in combination. Heteropolyacids such as phosphomolybdic acid can also be used. For example, ammonium paramolybdate, molybdenum trioxide, molybdic acid, molybdenum chloride, phosphomolybdic acid, silicomolybdic acid, etc. can be used as the molybdenum raw material.

  The method for preparing the catalyst precursor is not particularly limited, and various methods such as the evaporation and drying method, the precipitation method, and the oxide mixing method that are well known in the art are used unless significant uneven distribution of components is involved. However, it is preferable to obtain a catalyst precursor by drying a solution or slurry containing the catalyst raw material. It is more preferable to prepare by drying a solution or slurry containing 1% by mass or more of an organic substance with respect to components other than the solvent.

  As a drying method, various methods can be used, and for example, an evaporating and drying method, a spray drying method, a drum drying method, an air current drying method, and the like can be used. There are no particular limitations on the model of the dryer used for drying, the temperature, time, etc. during drying, and a catalyst precursor according to the purpose can be obtained by appropriately changing the drying conditions.

  Although 3 mass%-10 mass% organic substance is contained in the said catalyst precursor, the kind of organic substance to contain is not specifically limited, Moreover, the organic substance may be added in any manufacturing process before baking. Examples of the organic substance to be added include nitrogen-containing compounds such as pyridine and quinoline, organic acids such as acetic acid and tartaric acid, and molding aids such as cellulose and polyvinyl alcohol. The method of adding the organic substance is not particularly limited, the method of adding at the time of preparing the catalyst slurry, the method of adding the catalyst precursor to the slurry before drying, the method of dry-mixing with the catalyst after drying, the method of mixing with the catalyst precursor after dry molding There are ways to do it. The effect of the present invention is particularly great when a catalyst having a large organic content is calcined.

  The catalyst precursor has a weight reduction rate of 10% to 30% when the temperature is increased from 25 ° C. to 250 ° C. at a temperature increase rate of 10 ° C./min in thermogravimetric analysis. As a cause of weight reduction, in addition to oxidation and combustion of organic matter, volatilization of components such as ammonium root and nitrate root contained in the catalyst precursor to the outside of the catalyst system can be considered, but in the present invention, there is no particular limitation Preparation can be performed using raw materials containing ammonium and nitrate radicals.

  The shape of the catalyst precursor and the molding method are not particularly limited, and examples of the shape of the catalyst precursor include arbitrary shapes such as a spherical shape, a cylindrical shape, a cylindrical shape, and a star shape. Examples of means for forming a catalyst precursor powder to obtain a solid catalyst include a molding method using a molding apparatus such as a tableting molding machine, an extrusion molding machine, and a rolling granulator.

  The catalyst precursor thus obtained is preferably calcined using a fixed bed tubular reactor used in the production of methacrylic acid under a flow of oxygen-containing gas such as air or an inert gas. However, it can be fired in a conventionally known firing furnace. The form in the case of using a firing furnace is not particularly limited, and various firing furnaces such as a fixed bed system, a fluidized bed system, a rotary furnace, and a stationary furnace can be used. The shape of the firing furnace may be cylindrical or may have a polygonal tube shape or other irregular cross-sectional shape, and various shapes of firing furnaces can be used. In that case, it is preferable to carry out while circulating the gas used as the atmospheric gas.

  In the present invention, when the catalyst precursor is calcined using a fixed bed tubular reactor, the fixed bed tubular reactor is preferably provided with a heat medium bath. The heat medium is not particularly limited, and examples thereof include a salt melt containing potassium nitrate and sodium nitrite.

  The fixed bed reactor preferably has a structure capable of arbitrarily controlling the output of the heater that heats the heating medium, and the temperature raising rate for raising the temperature from the temperature before the firing treatment to the firing treatment target temperature is arbitrarily chosen. A controllable structure is preferred.

  The calcination temperature in the present invention is the measured temperature of the heat medium at the heat medium supply port to the heat medium bath when the fixed bed tubular reactor is a calcining container. When using other firing furnaces, the firing temperature is the measured temperature of the firing gas atmosphere in the firing furnace.

  The firing of the catalyst precursor varies depending on the catalyst raw material used, the catalyst composition, the preparation conditions, etc., and cannot be generally stated, but is performed under the flow of oxygen-containing gas such as air and / or under the flow of inert gas.

In the present invention, when the catalyst precursor is calcined using a fixed bed tubular reactor, the space velocity (hereinafter abbreviated as SV) of the calcining gas in the calcining of the catalyst precursor is the same as the apparatus used in the calcining, the furnace. Although it can be determined freely according to the size, 100 to 30000 h ⁻¹ is appropriate, and a range of 300 to 10000 h ⁻¹ is particularly preferable.

  The direction in which the calcination gas is circulated is not particularly limited, but it is preferable that the calcination gas is circulated in the direction opposite to the direction in which the reaction gas is circulated after the calcination is completed. By causing the reaction gas to flow in the direction opposite to the flow direction, it is possible to prevent the activity from becoming excessively high in the reaction gas containing side portion of the catalyst during the reaction.

  The firing temperature of the catalyst precursor is finally increased to 300 ° C. to 500 ° C., but in the present invention, in the firing step, the temperature rises in a specific temperature range from the temperature before the firing start to the final firing temperature. Control the temperature rate. That is, in the temperature range of 150 ° C. to 230 ° C., the rate of temperature rise is set to 5 ° C./hr or more and 25 ° C./hr or less. The above temperature range is a temperature range where organic substances added to the catalyst precursor are considered to be burned and decomposed, and it is expected that some components contained in the catalyst are desorbed in this temperature range. By setting the rate of temperature rise in this region to 5 ° C./hr or more and 25 ° C./hr or less, rapid decomposition of organic matter and heat generation and local desorption of ammonium roots can be suppressed, so It is presumed that a simple reduction reaction and a local reduction of the ammonium root can be suppressed, and a decrease in the performance of the catalyst can be prevented.

  The temperature raising method in the temperature range of 150 ° C. to 230 ° C. is not particularly limited except that the temperature raising rate is 5 ° C./hr or more and 25 ° C./hr or less. In the temperature range, the firing may be performed by changing the heating rate, but it is more preferable to continuously raise the temperature at a constant rate in terms of performing firing simply and quickly.

  The lower limit of the rate of temperature increase is required to be 5 ° C./hr or more from the point that it is important to prevent the catalyst performance from deteriorating to some extent, and is 10 ° C./hr or more. It is more preferable.

  The firing treatment start temperature in the present invention must be 150 ° C. or lower for controlling the rate of temperature rise, but the rate of temperature rise from the temperature before the firing treatment to 150 ° C. is not particularly limited. It is also possible to preheat the container for carrying out the process and charge the catalyst precursor to start firing.

  The temperature increase rate from 150 ° C. to 230 ° C. after the temperature increase is completed at a temperature increase rate of 5 ° C./hr or more and 25 ° C./hr or less until reaching the final maximum firing temperature is 20 ° C. / Although it does not specifically limit except being more than hr, It is preferable that it is 20-100 degreeC / hr at the point of shortening calcination time, preventing deterioration of the catalyst by rapid temperature change, and 20-50. More preferably, it is ° C / hr.

  In the production of methacrylic acid of the present invention, the concentration of methacrolein in the raw material gas is not particularly limited, but usually 1 to 20% by volume is appropriate, and 3 to 10% by volume is particularly preferable. The raw material methacrolein may contain a small amount of impurities such as water and lower saturated aldehyde, and these impurities do not have a substantial adverse effect on the reaction.

  It is economical to use air as the oxygen source, but if necessary, air enriched with pure oxygen can also be used. The oxygen concentration in the raw material gas is defined by the molar ratio to methacrolein, and this value is preferably 0.3 to 4, particularly 0.4 to 2.5. The source gas may be diluted by adding an inert gas such as nitrogen, water vapor or carbon dioxide. The reaction pressure is preferably from normal pressure to several atmospheres. The reaction temperature is preferably in the range of 230 to 450 ° C, and more preferably 250 to 400 ° C.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, "part" in an Example and a comparative example means a mass part. The catalyst precursor composition was determined from the raw material charge of the catalyst precursor component. The obtained catalyst precursor was mixed and filled with 620 ml of alumina spheres having an outer diameter of 5 mm and 130 ml of alumina spheres on the gas inlet side of a steel fixed-bed tube reactor having an inner diameter of 25.4 mm each equipped with a heat medium bath. On the outlet side, 750 ml of catalyst precursor was filled. As a heat medium for the reactor, a salt melt composed of 50% by mass of potassium nitrate and 50% by mass of sodium nitrite was used.

  The temperature control of the heating medium bath uses a mechanism that feeds back the temperature of the heating medium bath and controls the output of the heater installed in the heating medium bath, and automatically adjusts the heater output according to the arbitrarily set rate of temperature rise. The one that can be controlled automatically was used. The calcination temperature and reaction temperature were the measured temperatures of the heat medium at the heat medium supply port to the heat medium bath of the fixed bed tube reactor.

  The reaction rate of the raw material methacrolein, the selectivity of methacrylic acid to be produced, and the yield of methacrylic acid in the examples and comparative examples were calculated by the following equations.

Methacrolein reaction rate (%) = A / B × 100
Methacrylic acid selectivity (%) = C / A × 100
Methacrylic acid yield (%) = C / B × 100
Here, A is the number of moles of reacted methacrolein, B is the number of moles of methacrolein supplied, and C is the number of moles of methacrylic acid produced.

[Example 1]
In 400 parts of pure water, 200 parts of molybdenum trioxide, 10.8 parts of ammonium metavanadate and 5.6 parts of copper nitrate were dissolved. The temperature was raised to 95 ° C. while stirring. Next, after maintaining at 95 ° C. for 2 hours, cooling to 60 ° C., stirring with a rotary blade stirrer, adding 22.5 parts of cesium nitrate and 23.5 parts of ammonium nitrate, stirring for 15 minutes, and 85 mass A solution prepared by dissolving 13.3 parts of% phosphoric acid and 9.4 parts of ferric nitrate in 20 parts of pure water was added. 5.0 parts of hydroxymethylcellulose was added to the slurry, stirred for 15 minutes, and the resulting slurry was dried using a spray dryer.

4 parts of methylcellulose was added to and mixed with 100 parts of the obtained dried product, and kneaded with 20 parts of pure water was extruded to obtain a catalyst precursor 1 having an outer diameter of 5 mm, an inner diameter of 2 mm, and a length of 4 mm. Obtained. The composition of the catalyst precursor 1 excluding organic substances was P _1.0 Mo ₁₂ Cu _0.2 V _0.8 Fe _0.2 Cs ₁ in terms of atomic ratio excluding oxygen.

  The weight loss ratio when this catalyst precursor 1 was heated from 25 ° C. to 250 ° C. at a temperature rising rate of 10 ° C./min was measured using a thermogravimetric analyzer. As the measuring device, a thermogravimetric measuring device (trade name: TGA-50, manufactured by Shimadzu Corporation) was used. As measurement conditions, a compacted catalyst precursor was pulverized using a mortar and powdered, 50 mg was used as a sample, air was circulated at 300 mL / min, and heated at 10 ° C./min. It was measured. The weight reduction rate from 25 ° C. to 250 ° C. was 13% with respect to the sample weight used for the measurement.

After filling the catalyst precursor 1, with the air of SV1000h ^-1 flowing in the direction opposite to the direction in which the reaction gas is supplied, the firing temperature is increased from room temperature 25 ° C to 150 ° C at a rate of 25 ° C / hr. The temperature was raised, and the temperature was raised from 150 ° C. to 230 ° C. at 20 ° C./hr. Thereafter, the temperature from 230 ° C. to 380 ° C. was increased again at 25 ° C./hr, and when the temperature reached 380 ° C., the temperature increase was stopped and maintained at 380 ° C. for 12 hours. After maintaining at 380 ° C. for 12 hours, the firing temperature was lowered to 260 ° C. at a temperature decrease rate of 25 ° C./hr. At this time, the time taken for firing was 31.8 hours.

  Thereafter, the air flowing in the reaction tube was temporarily stopped, and a raw material mixed gas composed of 5% methacrolein, 12% oxygen, 10% water vapor and 73% nitrogen was added to the reaction tube at a reaction temperature of 290 ° C. and a contact time of 4. The reaction was allowed to pass in 5 seconds. The results are shown in Table 1.

[Comparative Example 1]
After the catalyst precursor 1 was filled, firing was carried out under the same conditions as in Example 1 except that the firing temperature was raised in the range from 150 ° C. to 230 ° C. at a rate of temperature rise of 50 ° C./hr to carry out the oxidation reaction. The results are shown in Table 1. In addition, sintering was observed in a part of the catalyst after the reaction.

[Example 2]
The catalyst was prepared using the same preparation method as in Example 1, and the catalyst was prepared under the same conditions as in Example 1 except that 6 parts of methylcellulose mixed with the resulting dried product was used. Got. When this catalyst precursor 2 was measured using a thermogravimetric analyzer in the same manner as in Example 1, a 15% weight reduction was observed with respect to the weight before the measurement. This catalyst precursor 2 was calcined under the same conditions as in Example 1 to carry out an oxidation reaction. The results are shown in Table 1.

[Comparative Example 2]
After the catalyst precursor 2 was filled, the calcination temperature was baked under the same conditions as in Example 1 except that the temperature was raised in the range of 150 ° C. to 230 ° C. at a rate of temperature increase of 50 ° C./hr, and an oxidation reaction was carried out. The results are shown in Table 1. In addition, sintering was observed in a part of the catalyst after the reaction.

[Example 3]
When charging the catalyst precursor 1 into the reactor, the reactor was preheated to 150 ° C. and charged, and firing was started from 150 ° C., and the temperature was raised to 230 ° C. at a rate of 20 ° C./hr. Firing was carried out under the same conditions as in No. 1 to carry out an oxidation reaction. The results are shown in Table 1.

[Comparative Example 3]
When charging the catalyst precursor 1 into the reactor, the reactor was preheated to 200 ° C. and charged, firing was started from 200 ° C., and the temperature was raised to 230 ° C. at 20 ° C./hr. Firing was carried out under the same conditions as in No. 1 to carry out an oxidation reaction. The results are shown in Table 1. In addition, sintering was observed in a part of the catalyst after the reaction.

[Comparative Example 4]
After the catalyst precursor 1 was filled, the catalyst was calcined under the same conditions as in Example 1 except that the temperature was increased at a temperature increase rate of 10 ° C./hr in the range from 25 ° C. to 380 ° C. The reaction was carried out. The results are shown in Table 1.

[Comparative Example 5]
A slurry containing a catalyst raw material was prepared in the same manner as in Example 1, and a catalyst precursor 3 was obtained in the same manner as in Example 1 except that methylcellulose was not added to the obtained dried product. The composition of the catalyst precursor 3 excluding organic substances was Mo ₁₂ P _1.0 Cu _0.2 V _0.8 Fe _0.2 Cs ₁ in terms of atomic ratio excluding oxygen. When this catalyst precursor was heated up to 250 ° C. at a rate of 10 ° C./min using a thermogravimetric analyzer, a 5% weight reduction was observed with respect to the weight before the measurement. This catalyst precursor was calcined under the same conditions as in Example 1 to carry out an oxidation reaction. The results are shown in Table 1.

[Comparative Example 6]
After filling the catalyst precursor 3, the firing temperature was the same as in Example 1 except that the firing temperature was raised in the range of 150 ° C. to 230 ° C. at a heating rate of 50 ° C./hr. Firing was carried out and an oxidation reaction was carried out. The results are shown in Table 1.

  From these results, it can be seen that the present invention is effective for a catalyst system containing a large amount of organic substances and having a large weight loss by thermal analysis.

Claims (3)

A method for producing a catalyst for producing methacrylic acid by vapor phase catalytic oxidation of methacrolein, comprising at least phosphorus and molybdenum, wherein the catalyst for producing methacrylic acid satisfies the following conditions (i) to (iii): Production method.
(I) The catalyst precursor contains 3% to 10% of organic matter as a mass. (Ii) In the thermogravimetric analysis of the catalyst precursor, when the temperature is increased from 25 ° C. to 250 ° C. at a temperature increase rate of 10 ° C./min. (Iii) In the process of raising the temperature of the catalyst precursor satisfying the above (i) and (ii) from 150 ° C. or lower and performing final calcination at 300 ° C. to 500 ° C. The temperature increase rate in the temperature range of 270C to 230 ° C is 5 ° C / hr or more and 25 ° C / hr or less, and the temperature increase rate in the temperature range from 230 ° C to the highest temperature in the final firing is 20 ° C / hr or more.   The method for producing a catalyst according to claim 1, wherein the catalyst precursor is obtained by drying a solution or slurry containing 1% by mass or more of an organic substance with respect to components other than the solvent.   A method for producing methacrylic acid, which comprises subjecting methacrolein to gas phase catalytic oxidation using the catalyst for producing methacrylic acid produced by using the production method according to claim 1.