JP2005213179A - Catalyst layer and method for forming the same, fixed bed tubular reactor, method for producing methacrolein or methacrylic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst layer which can not only lower the temperature of a hot spot but also equalize the loads of an oxidation reaction to prevent the local deterioration of the catalyst, to provide a method for forming the same, and to provide a fixed bed tubular reactor, and to provide a method for producing methacrolein or methacrylic acid. <P>SOLUTION: This catalyst layer which is heated with a heating medium to react raw material gases is characterized in that the catalyst layer is divided into two or more reaction zones in the longitudinal direction of the catalyst layer and that a reaction load ratio : CRc(i) per unit mass of the catalyst in each reaction zone is 0.6 to 1.0. The fixed bed tubular reactor comprises a reaction tube in which the catalyst layer is formed, a heating medium bath filled with a heating medium for heating the reaction tube, and a gas-supplying mechanism for supplying a raw material gas to the reaction tube. The method for producing the methacrolein or methacrylic acid comprises reacting tert-butanol and / or isobutylene with molecular oxygen in the fixed bed tubular reactor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a catalyst layer used for production of methacrolein or methacrylic acid, a method for forming the catalyst layer, and a fixed bed tubular reactor. Furthermore, it is related with the manufacturing method of methacrolein or methacrylic acid.

  Methacrolein or methacrylic acid is produced by a gas phase catalytic oxidation reaction of tert-butanol and / or isobutylene using a catalyst. Since this gas phase catalytic oxidation reaction is an exothermic reaction, heat storage occurs in the catalyst layer, and as a result of the heat storage, a high temperature zone may be locally generated. The local high temperature zone is called a hot spot. If the temperature of the hot spot is too high, an excessive oxidation reaction occurs and the yield of the target product decreases. Therefore, when this gas phase catalytic oxidation reaction is carried out industrially, it is an important issue to suppress the temperature of the hot spot. However, when the concentration of tert-butanol and / or isobutylene in the raw material gas is increased in order to increase productivity, the temperature of the hot spot tends to increase. Therefore, in order to suppress the temperature of the hot spot, there are many restrictions on the reaction conditions such that the tert-butanol and / or isobutylene concentration cannot be increased.

Therefore, as a method for suppressing the temperature of the hot spot, for example, the catalyst layer is divided into a plurality of reaction zones, and the catalyst layer on the gas inlet side is diluted with an inert substance (see, for example, Patent Document 1), the catalyst layer. Is divided into a plurality of reaction zones, and the catalyst active substance loading rate (mass ratio of active substance per catalyst) is sequentially increased from the gas inlet side toward the gas outlet side (see, for example, Patent Document 2). A method of dividing the catalyst layer into a plurality of reaction zones and sequentially reducing the size of the molded catalyst from the gas inlet side to the gas outlet side has been proposed (for example, see Patent Document 3).
In these methods, the reaction rate per unit volume on the raw material gas inlet side in the catalyst layer is lowered to suppress the reaction heat generation amount per unit volume, and as a result, the temperature of the hot spot is lowered. . And according to these methods, since an excessive oxidation reaction at a hot spot can be suppressed, the yield is improved and the life of the catalyst can be extended by reducing the thermal load.
Japanese Patent Publication No.43-24403 JP-A-6-192144 JP-A-4-217932

However, these methods focus only on suppressing the temperature of the hot spot, and as a result, the oxidation reaction load distribution in the catalyst layer becomes non-uniform, and a portion with a high oxidation reaction load may be generated. was there. Furthermore, when a portion with a high oxidation reaction load occurs, the catalyst tends to fail to be reoxidized. This may accelerate the deterioration of the catalyst and significantly shorten the life of the entire catalyst layer. It was.
The present invention has been made in order to solve the above-described conventional problems, and not only suppresses the temperature of the hot spot, but also a catalyst layer that can equalize the oxidation reaction load and suppress local catalyst degradation, and the catalyst layer It is an object of the present invention to provide a forming method, a fixed bed tubular reactor, a method for producing methacrolein or methacrylic acid.

The catalyst layer of the present invention is a catalyst layer that is heated by a heat medium to react a raw material gas.
The length direction of the catalyst layer is divided into two or more reaction zones, and in each reaction zone, the reaction load ratio CRc (i) per catalyst unit mass defined by the following formulas (1) to (3) Is 0.6 to 1.0.

(Where Rc (i) is the reaction load (° C. · m / kg) of the i-th layer reaction zone, and Li (j) is from the jth temperature measurement point to the j + 1th temperature measurement point in the i-th layer reaction zone. In the longitudinal direction (m), Wc (i) is the catalyst charge (kg) in the i-th reaction zone, Ti (j) is the catalyst layer temperature (° C.) at the j-th measurement point in the i-th reaction zone , TB heat medium temperature (℃), RcMAX the maximum value of Rc (i), n is the reaction zone number, _{m i} represents the temperature measurement points in the reaction zone of the i-th layer. However, i = 1 to n. In addition, i and j are counted sequentially from the inlet side of the source gas.)

The fixed bed tube reactor of the present invention includes a reaction tube in which the catalyst layer described above is formed,
A heating medium bath filled with a heating medium for heating the reaction tube;
And a gas supply mechanism for supplying a raw material gas to the reaction tube.
The method for producing methacrolein or methacrylic acid of the present invention is characterized in that tert-butanol and / or isobutylene and molecular oxygen are reacted in the above-described fixed bed tubular reactor.
The catalyst layer forming method of the present invention includes a first step of filling a reaction tube with a catalyst and forming a catalyst layer divided in a reaction zone having a length direction of two or more layers, and a raw material gas in the catalyst layer. And a second step of measuring the catalyst layer temperature during the test reaction,
The first step and the second step until the reaction load ratio CRc (i) per catalyst unit mass defined by the above formulas (1) to (3) in each reaction zone satisfies 0.6 to 1.0. It is characterized by repeating.
The catalyst layer forming method of the present invention is characterized in that the same catalyst layer as that formed by the above-described catalyst layer forming method is formed in another reaction tube.

  According to the present invention, the temperature of the hot spot in the gas phase catalytic oxidation can be suppressed, and the oxidation reaction load can be made uniform to suppress local deterioration of the catalyst, so that the catalyst can be stably used for a long time.

Hereinafter, an embodiment of the present invention will be described. This example is an example of producing methacrolein or methacrylic acid using a catalyst layer.
First, the catalyst layer will be described.
The catalyst layer is a portion containing at least a catalyst in the reaction tube. Therefore, not only the portion filled with only the catalyst but also the portion where the catalyst is diluted with an inert carrier such as silica, alumina, silica-alumina, silicon carbide, etc. are included. However, a portion where nothing is filled at both ends of the reaction tube or a portion where only the inert carrier is filled is not included in the catalyst layer because the catalyst is not substantially included. And this catalyst layer is a layer in the reaction tube which is heated with a heat medium and reacts raw material gas.

  The catalyst layer is divided into two or more reaction zones in the length direction (the tube axis direction of the reaction tube). Here, being divided into two or more reaction zones means that two or more layers having different catalyst filling conditions are formed. In each reaction zone, the reaction load ratio CRc (i) (hereinafter, abbreviated as CRc (i)) per catalyst unit mass defined by the above formulas (1) to (3) is 0.6 to 1.0. When CRc (i) is less than 0.6, local catalyst degradation occurs and the catalyst life is shortened.

  Regarding the number of divisions of the catalyst layer, if the number of divisions is increased, the mass of the substantial catalyst component can be finely adjusted and can be further optimized. 2 to 4 divisions are selected.

The calculation of Rc (i) is based on the following assumption that the reaction load is uniform. 1) The amount of heat generated in the catalyst layer is proportional to the amount of oxidation reaction involving the catalyst. 2) There is no temperature distribution in the radial direction of the catalyst layer. 3) The overall heat transfer coefficient between the heat medium and the catalyst layer is constant regardless of the reaction zone. 4) In each reaction zone, the effects of the amount of heat brought in by the gas flowing in from the reaction zone inlet and the amount of heat taken out from the reaction zone outlet are not considered.
Under these assumptions, the value obtained by subtracting the heat medium temperature from the temperature in the catalyst layer (ΔT) and the amount of oxidation reaction involving the catalyst can be expressed by a linear relationship. Therefore, this ΔT is integrated in the length direction from the inlet to the outlet of each reaction zone, and the obtained value is divided by the catalyst filling mass of the reaction zone, thereby obtaining the reaction load per catalyst unit mass for each reaction zone. The ratio can be calculated.
Strictly speaking, the assumptions 1) to 4) are not satisfied. That is, depending on the position of the catalyst layer, the rate at which the main reaction in which methacrolein or methacrylic acid is generated and the reaction in which COx and other components are generated slightly differs. There is a temperature distribution in the radial direction of the catalyst layer with some difference. The overall heat transfer coefficient changes by adjusting the substantial catalyst component mass for each reaction zone. A small portion of the heat generated in each reaction zone is taken out of the reaction zone by the raw material gas. However, even if these occur, the influence is small. Therefore, if CRc (i) satisfies 0.6 to 1.0, the catalyst layer has a sufficient effect.

In order to form such a catalyst layer in the reaction tube, first, in the first step, the catalyst is filled in the reaction tube, and the catalyst layer is formed by dividing the length direction into two or more reaction zones. Usually, the first catalyst filling is performed based on empirical knowledge. Next, in the second step, the source gas is subjected to a test reaction in the catalyst layer, and the catalyst layer temperature during the test reaction is measured.
And CRc (i) is calculated | required in each reaction zone, and when CRc (i) of all the reaction zones does not satisfy 0.6-1.0, a catalyst is extracted from a reaction tube, and it begins from the 1st process. Try again. When CRc (i) of all reaction zones satisfies 0.6 to 1.0, the catalyst layer is finalized.

In the catalyst layer forming method, in the catalyst filling in the first step, two or more layers having different catalyst filling conditions are formed to form a catalyst layer divided into two or more reaction zones. The catalyst filling conditions include the type of catalyst, the mixing ratio of the catalyst and the inert carrier, the loading ratio of the catalyst, the size of the molded catalyst, and the like.
Further, in order to suppress the temperature of the hot spot on the catalyst layer inlet side, the catalyst is filled so that the substantial amount of catalyst component per unit volume of the reaction zone on the raw material gas inlet side is reduced. Examples of the filling method that reduces the amount of the substantial catalyst component per unit volume include, for example, 1) a method in which the catalyst layer is divided into a plurality of reaction zones, and the reaction zone on the raw material gas inlet side is diluted with an inert substance; ) A method in which the catalyst layer is divided into a plurality of reaction zones, and the loading ratio of the catalytically active substance (mass ratio of active substance per catalyst) is increased sequentially from the raw material gas inlet side to the product gas outlet side. Examples include a method of dividing the layer into a plurality of reaction zones and sequentially reducing the size of the catalyst molded body from the raw material gas inlet side toward the product gas outlet side. In addition, in the case of the production of methacrolein or methacrylic acid, the temperature of the hot spot is suppressed by setting the maximum value of the distribution in the length direction of the reaction tube of the value obtained by subtracting the heat medium temperature from the catalyst layer temperature (ΔT) to 45 ° C. Is to:

A solid oxidation catalyst is used as the catalyst filled in the reaction tube. As the solid oxidation catalyst, a known composite oxide containing molybdenum or the like can be used, but a composite oxide represented by the following composition formula is preferable.
_{Mo a Bi b Fe c A d} X e Y f Z g O h
(Wherein Mo, Bi, Fe, and O represent molybdenum, bismuth, iron, and oxygen, respectively, A is selected from the group consisting of nickel and / or cobalt, and X is selected from the group consisting of magnesium, zinc, manganese, tin, and lead. At least one element, Y is at least one element selected from the group consisting of phosphorus, boron, sulfur, tellurium, silicon, selenium, germanium, cerium, niobium, aluminum, titanium, zirconium, tungsten and antimony, Z Represents at least one element selected from the group consisting of potassium, sodium, rubidium, cesium, and thallium, provided that a, b, c, d, e, f, g, and h represent the atomic ratio of each element. When a = 12, 0.1 ≦ b ≦ 5, 0.1 ≦ c ≦ 5, 1 ≦ d ≦ 12, 0 ≦ e ≦ 10, 0 ≦ f ≦ 0,0.01 ≦ g ≦ 3, a, h is the atomic ratio of oxygen required to satisfy the valence of each component.)
The solid oxidation catalyst may be supported on an inert carrier such as silica, alumina, silica / alumina, or silicon carbide.

As a method for preparing the solid oxidation catalyst, various known methods can be adopted as long as the components are not significantly unevenly distributed. As raw materials used for preparing the catalyst, nitrates, carbonates, acetates, ammonium salts, oxides, halides and the like of each element can be used in combination. For example, ammonium paramolybdate, molybdenum trioxide, molybdic acid, molybdenum chloride, etc. can be used as the molybdenum raw material.
The solid oxidation catalyst is used after being molded, and examples of the form thereof include a tableting catalyst formed into a tablet shape, and an extrusion catalyst formed into a columnar shape or a ring shape.

  When a supported catalyst or a compression-molded catalyst is properly used for each reaction zone, even if a catalyst molded body has the same mass, the mass of the substantial catalyst component is different. Therefore, when calculating CRc (i), Wc As (i), it is preferable to adopt the mass of the substantial catalyst component in each reaction zone, not the mass of the filled catalyst molded body.

In the test reaction in the second step, the reaction temperature is usually 200 to 450 ° C., preferably 250 to 400 ° C. with the heat medium, the reaction pressure is in the range of normal pressure to about 1 MPa, and the raw material gas is allowed to react through the catalyst layer. To obtain methacrolein or methacrylic acid.
Here, the test reaction is not a reaction aiming at obtaining methacrolein or methacrylic acid, but a reaction aiming at determining packing conditions of the catalyst layer.

The source gas is not particularly limited as long as it contains tert-butanol and / or isobutylene and molecular oxygen. For example, a gas containing 3 to 9% by volume of tert-butanol and / or isobutylene, 5 to 15% by volume of oxygen, and 5 to 50% by volume of water vapor is used as the source gas. Moreover, it is economically advantageous and preferable to use air as the oxygen source. The source gas may contain an inert gas such as nitrogen or carbon dioxide. The source gas may contain an exhaust gas having an oxygen content lower than that of air generated by the oxidation reaction of the present invention or other gas phase oxidation reaction. The exhaust gas may be used as it is, or an exhaust gas in which organic substances are reduced by a method using a combustion catalyst such as platinum may be used.
The source gas may contain a small amount of impurities that do not substantially affect the reaction.
The flow rate of the source gas is not particularly limited, but is preferably a flow rate at which the space velocity is 300 to 3000 hr ⁻¹ , and particularly preferably a flow rate at which the space velocity is 500 to 2000 hr ⁻¹ .

  When tert-butanol is used as the source gas, the dehydration reaction from tert-butanol to isobutylene is an endothermic reaction, so that Ti (j) on the source gas inlet side decreases as j increases and becomes smaller than TB. is there. In the region where Ti (j) is less than TB, tert-butanol is mainly dehydrated, so the catalyst is not effectively used for the oxidation reaction. When dehydration of tert-butanol proceeds to some extent and the oxidation reaction proceeds, Ti (j) rises again and exceeds TB. Therefore, in the calculation of CRc (i), the point where Ti (j) is less than TB may be excluded from the calculation target, and may be performed from the point where Ti (j) exceeds TB.

In the second step, the catalyst layer temperature during the test reaction can be measured with a thermocouple inserted in a protective tube installed at the center of the cross section perpendicular to the length direction of the reaction tube. At this time, it is desirable to isolate the inside of the protective tube from the catalyst, and to set the temperature measurement position so that the length of the thermocouple to be inserted can be adjusted. Further, the catalyst layer temperature may be measured by a number of thermocouples fixedly inserted in the reaction tube.
Further, when measuring the catalyst layer temperature and measuring the catalyst layer temperature distribution for each reaction zone, it is preferable that Li (j) is small because the accuracy of the reaction load calculation is improved. However, in the portion where the temperature change in the length direction of the catalyst layer is small, the accuracy of the reaction load calculation does not decrease even if Li (j) is large or the value is increased. Further, when determining Li (j), it is preferable that the difference between Ti (j) and Ti (j + 1) is within a range of 5 ° C. or less.

Next, the fixed bed tube reactor will be described.
The fixed bed tube reactor includes a reaction tube in which the catalyst layer is formed, a heat medium bath filled with a heat medium for heating the reaction tube, and a gas supply mechanism for supplying a raw material gas to the reaction tube. It is to be prepared.
In this fixed bed tubular reactor, it is sufficient that a catalyst layer is formed in at least a part of the reaction tube. As the heat medium filled in the heat medium bath, for example, salt melting including potassium nitrate, sodium nitrite and others. Things.
As an example of the gas supply mechanism, an evaporator including a plate tower or a packed tower for gasifying a liquid raw material such as tert-butanol, a booster such as a compressor for boosting a gas obtained from the evaporator, and an air Equipped with a booster such as a compressor for boosting other gaseous auxiliary materials such as nitrogen and nitrogen, and a gas mixing device such as a gas mixer for mixing the gasified and pressurized liquid material with the pressurized gaseous material Is mentioned. Further, when a gaseous raw material such as isobutylene is used in place of the liquid raw material, an evaporation device is not necessary, and this gaseous raw material is sent to a gas mixing device via a booster such as a compressor.

  In the production of methacrolein or methacrylic acid using the above fixed bed tubular reactor, a raw material gas containing tert-butanol and / or isobutylene and molecular oxygen is supplied to the reaction tube by a gas supply mechanism, React in layers. The reaction conditions at that time are the same as those in the second step.

  In the embodiment described above, the catalyst layer that is heated by the heat medium and reacts with the raw material gas is divided into two or more reaction zones, and CRc (i) is 0.6 to 1.0 in each reaction zone. Since the amount of oxidation reaction per unit catalyst mass in each reaction zone is taken into consideration, not only the temperature of the hot spot can be suppressed, but also the oxidation reaction load distribution in the catalyst layer can be made uniform. As a result, since reoxidation failure of the catalyst can be prevented, deterioration of the catalyst can be suppressed and the life of the entire catalyst layer can be extended.

The catalyst layer and the fixed bed tube reactor of the present invention are not limited to the above-described embodiment examples. For example, when a plurality of reaction tubes of the same kind are formed and a catalyst layer is formed in these reaction tubes, the first step and the second step are performed so that CRc (i) satisfies the above range as described above. The method of forming the catalyst layer by repeating the steps may not be applied to all reaction tubes. That is, a catalyst layer may be formed in one or several reaction tubes by the above-described catalyst layer forming method, and the same catalyst layer as that catalyst layer may be formed in another reaction tube. The catalyst layer formed in the other reaction tube is a replica of CRc (i) that satisfies the above range, so that CRc (i) satisfies the above range.
Industrially, this method is adopted. That is, industrially, the number of reaction tubes is several thousand to several tens of thousands, and it takes too much time to form the catalyst layer by measuring the temperature of all the reaction tubes. Therefore, first, a catalyst layer in which CRc (i) satisfies the above range is found by the above catalyst layer forming method in a pilot facility having one or several reaction tubes of the same type as the reaction tubes used for production. Then, the catalyst is filled in the reaction tube used for production under the same catalyst filling conditions as the catalyst layer, and a catalyst layer in which CRc (i) satisfies the above range is formed for all the reaction tubes. According to such a method, labor for forming a catalyst layer in which CRc (i) satisfies the above range is reduced.

  In addition, the present invention can be applied to any case where a gas phase contact reaction is performed in a catalyst layer. However, the reaction of tert-butanol and / or isobutylene with molecular oxygen is particularly effective.

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.
In the following examples or comparative examples, a salt melt composed of 50% by mass of potassium nitrate and 50% by mass of sodium nitrite was used as the heat medium of the fixed bed multitubular reactor. The temperature in the catalyst layer was measured by a thermocouple inserted in a protective tube made of SUS304 installed at the center of the cross section perpendicular to the length direction of the reaction tube. Further, the inside of the protective tube is isolated from the catalyst, and the temperature measuring position can be changed by adjusting the length of the thermocouple to be inserted.

The analysis of the raw material gas and the reaction product gas was performed using gas chromatography. And the reaction rate of tert-butanol and isobutylene, the selectivity of the produced methacrolein and methacrylic acid, and the yield are defined as follows, respectively.
Reaction rate of tert-butanol and isobutylene (%) = (B / A) × 100
Selectivity of methacrolein (%) = (C / B) × 100
Methacrylic acid selectivity (%) = (D / B) × 100
Yield of methacrolein and methacrylic acid (%) = {(C + D) / A} × 100
Here, A is the total number of moles of tert-butanol and isobutylene supplied, and B is the total number of moles of tert-butanol and isobutylene at the reactor outlet from the total number of moles of tert-butanol and isobutylene used in the oxidation reaction. Subtracted, C is the number of moles of methacrolein produced, and D is the number of moles of methacrylic acid produced.

(Comparative Example 1)
To 1000 parts of pure water, 500 parts of ammonium paramolybdate, 6.2 parts of ammonium paratungstate, and 23.0 parts of cesium nitrate were added and stirred with heating (solution A). Separately, 60% by mass and 41.9 parts of nitric acid were added to 600 parts of pure water to make it uniform, and then 68.7 parts of bismuth nitrate were added and dissolved. To this, 200.2 parts of ferric nitrate, 116.6 parts of nickel nitrate, 432.7 parts of cobalt nitrate and 54.5 parts of magnesium nitrate were sequentially added, and 400 parts of water was further added and dissolved (Liquid B). Liquid B was added to liquid A to form an aqueous slurry, and then 24.1 parts of antimony trioxide was added, heated and stirred, and dried using a spray dryer to obtain dry spherical particles. The dried spherical particles were calcined at 300 ° C. for 1 hour and at 510 ° C. for 3 hours to obtain a catalyst calcined product. 15 parts of hydroxypropylmethylcellulose was added to 500 parts of the catalyst calcined product thus obtained and dry mixed. After mixing 170 parts of pure water and mixing with a kneader until a clay-like substance is obtained, the irregular shaped kneaded product is extruded using a screw-type extruder, and is a circle having a diameter of 45 mm and a length of 280 mm. A columnar primary molded product was obtained. Next, this primary molded product was sealed with a plastic film so as not to evaporate moisture, and further sealed in a sealed container and cured in a thermostatic bath at 25 ° C. for 22 hours. After curing, this primary molded product was extruded using a piston-type extruder, and a ring-shaped catalyst molded product having an outer diameter of 5 mm, an inner diameter of 2 mm, and a length of 5 mm was obtained. Next, the obtained catalyst molded product was dried using a 110 ° C. hot air dryer and fired again at 400 ° C. for 3 hours to obtain a final fired product of the catalyst molded product. The composition of the obtained catalyst molded product is an atomic ratio excluding oxygen,
Mo ₁₂ Bi _0.6 Fe _2.1 Ni _1.7 Co _6.3 Mg _0.9 W _0.1 Sb _0.7 Cs _0.5
Met. The composition of the catalyst was determined from the raw material charge of the catalyst component.

  For the reaction, a fixed bed tubular reactor made of SUS304 equipped with a heat medium bath and a reaction tube having an inner diameter of 25.4 mm was used. The catalyst layer is divided into two reaction zones. In the gas inlet side reaction zone (first reaction zone) located on the source gas supply side, the catalyst is 0.37 kg (570 mL) and the outer diameter is 5 mm alumina spheres 190 mL. And was mixed. The length of the catalyst layer in the source gas inlet side reaction zone was 1502 mm. In the gas outlet side reaction zone (second layer reaction zone), 0.49 kg (760 mL) of the catalyst was charged. At this time, the length of the catalyst layer in the gas outlet side reaction zone was 1506 mm.

Then, a raw material gas consisting of 7.0% by volume of tert-butanol, 10% by volume of oxygen, 10% by volume of water vapor and 73.0% by volume of nitrogen was passed through the catalyst layer at a space velocity of 1500 hr ⁻¹ at a heat medium temperature of 319 ° C. Reaction was performed.
Two days after the start of the reaction, the catalyst layer temperature was measured. As a result, a hot spot having a maximum temperature was observed at a position of 950 mm from the upstream end of the gas inlet side reaction zone, and ΔT at this maximum temperature was 38 ° C. Further, the catalyst layer temperature substantially exceeded the heat medium temperature at a position 350 mm from the upstream end of the gas inlet side reaction zone. Rc (i) of the gas inlet side reaction zone is 105.9 ° C. · m / kg, CRc (i) is 1.0, Rc (i) of the gas outlet side reaction zone is 61.4 ° C. · m / kg, CRc (I) was 0.58.

In Comparative Example 1, the reaction rate of tert-butanol and isobutylene was 83.4%, the methacrolein selectivity was 87.6%, the methacrylic acid selectivity was 2.1%, and the yields of methacrolein and methacrylic acid were It was 74.8%.
In addition, the catalyst layer filled under the conditions of Comparative Example 1 had a rapid decrease in activity, and the temperature of the heat medium was increased to 330 ° C. to compensate for the decrease in activity due to the deterioration of the catalyst. The reaction rate of tert-butanol and isobutylene could not be maintained.

(Example 1)
In Comparative Example 1, since CRc (i) in the gas outlet side reaction zone was less than 0.6, the catalyst was removed from the reaction tube, and the amount of catalyst in the gas inlet side reaction zone was reduced and refilled. Specifically, in the gas inlet side reaction zone, the catalyst was mixed with 0.29 kg (460 mL) and 300 mL of alumina spheres having an outer diameter of 5 mm. Then, the reaction was performed in the same manner as in Comparative Example 1 except that the heat medium temperature was 322 ° C.

  Two days after the start of the reaction, the catalyst layer temperature was measured. As a result, a hot spot having a maximum temperature was observed at a position 200 mm from the upstream end of the gas outlet side reaction zone, and ΔT at this maximum temperature was 39 ° C. Further, the catalyst layer temperature substantially exceeded the heat medium temperature at a position 350 mm from the upstream end of the gas inlet side reaction zone. The Rc (i) of the raw material gas inlet side reaction zone is 107.2 ° C. · m / kg, the CRc (i) is 1.0, and the Rc (i) of the raw material gas outlet side reaction zone is 73.8 ° C. · m. / Kg, CRc (i) was 0.69.

  The reaction rate of tert-butanol and / or isobutylene was 84.2%, the methacrolein selectivity was 87.8%, the selectivity of methacrylic acid was 2.0%, and the yield of methacrolein and methacrylic acid was 75. It was 6%. Even after 30 days from the start of the reaction, the reaction rate of tert-butanol was 84.5% with the heat medium temperature kept at 322 ° C., and the catalyst layer maintained sufficient reaction activity. Therefore, in Example 1, the catalyst life was longer in spite of the fact that the mass of the substantial catalyst component in the catalyst layer was smaller than in Comparative Example 1.

(Example 2)
A catalyst layer identical to the catalyst layer of Example 1 was formed in another reaction tube without inserting a thermocouple protection tube into the reaction tube and measuring the temperature distribution in the catalyst layer during the reaction. The length of the catalyst layer in the gas inlet side reaction zone was 1408 mm, and the length of the catalyst layer in the gas outlet side reaction zone was 1501 mm.
Two days after the start of the reaction, the reaction rate of tert-butanol and isobutylene was 84.7%, the methacrolein selectivity was 87.9%, the methacrylic acid selectivity was 2.0%, and the yields of methacrolein and methacrylic acid were 76. 1%. Even after 30 days from the start of the reaction, the heat medium temperature was kept at 322 ° C., and the reaction rates of tert-butanol and isobutylene were 84.7%, and the catalyst layer maintained sufficient reaction activity.

(Example 3)
The catalyst layer was divided into three reaction zones. In the reaction zone on the gas inlet side, a mixture of 0.21 kg (330 mL) of catalyst and 330 mL of alumina spheres having an outer diameter of 5 mm was filled. The length of the catalyst layer in the gas inlet side reaction zone was 1305 mm. In the intermediate reaction zone, a mixture of 0.10 kg (150 mL) of catalyst and 100 mL of alumina spheres having an outer diameter of 5 mm was packed. The length of the catalyst layer in this reaction zone was 498 mm. In the gas outlet side reaction zone, 0.39 kg (610 mL) of catalyst was charged. The length of the catalyst layer in the gas outlet side reaction zone was 1206 mm.

The reaction was started at a heat medium temperature of 325 ° C. Two days after the start of the reaction, the catalyst layer temperature was measured. As a result, a hot spot having a maximum temperature was observed at a position 300 mm from the upstream end of the gas outlet side reaction zone, and ΔT at this maximum temperature was 36 ° C. Further, the catalyst layer temperature substantially exceeded the heat medium temperature at a position 350 mm from the upstream end of the gas inlet side reaction zone. Rc (i) of the gas inlet side reaction zone is 109.7 ° C. · m / kg, CRc (i) is 0.91, Rc (i) of the intermediate reaction zone is 120.7 ° C. · m / kg, CRc ( i) was 1.0, Rc (i) in the reaction zone on the raw material gas outlet side was 76.8 ° C. · m / kg, and CRc (i) was 0.64.
In this reaction, the reaction rate of tert-butanol and isobutylene was 83.3%, the methacrolein selectivity was 88.3%, the methacrylic acid selectivity was 2.0%, and the yield of methacrolein and methacrylic acid was 75.2. %Met. Even after 30 days from the start of the reaction, the heat medium temperature was kept at 325 ° C., and the reaction rates of tert-butanol and isobutylene were 83.6%, and the catalyst layer maintained sufficient reaction activity.

Claims (5)

In the catalyst layer that is heated by the heat medium to react the raw material gas,
The length direction of the catalyst layer is divided into two or more reaction zones, and in each reaction zone, the reaction load ratio CRc (i) per catalyst unit mass defined by the following formulas (1) to (3) Is in the range of 0.6 to 1.0.

(Where Rc (i) is the reaction load (° C. · m / kg) of the i-th layer reaction zone, and Li (j) is from the jth temperature measurement point to the j + 1th temperature measurement point in the i-th layer reaction zone. In the longitudinal direction (m), Wc (i) is the catalyst charge (kg) in the i-th reaction zone, Ti (j) is the catalyst layer temperature (° C.) at the j-th measurement point in the i-th reaction zone , TB heat medium temperature (℃), RcMAX the maximum value of Rc (i), n is the reaction zone number, _{m i} represents the temperature measurement points in the reaction zone of the i-th layer. However, i = 1 to n. In addition, i and j are counted sequentially from the inlet side of the source gas.) A reaction tube in which the catalyst layer according to claim 1 is formed;
A heating medium bath filled with a heating medium for heating the reaction tube;
A fixed bed tube reactor comprising a gas supply mechanism for supplying a raw material gas to the reaction tube.   A method for producing methacrolein or methacrylic acid, comprising reacting tert-butanol and / or isobutylene with molecular oxygen in the fixed bed tubular reactor according to claim 2. A first step of filling the reaction tube with a catalyst and forming a catalyst layer whose length direction is divided into two or more reaction zones, and a test reaction of the raw material gas in the catalyst layer, and at the time of the test reaction A second step of measuring the catalyst layer temperature,
The first step and the second step until the reaction load ratio CRc (i) per catalyst unit mass defined by the following equations (4) to (6) in each reaction zone satisfies 0.6 to 1.0: The catalyst layer forming method characterized by repeating.

(Where Rc (i) is the reaction load (° C. · m / kg) of the i-th layer reaction zone, and Li (j) is from the jth temperature measurement point to the j + 1th temperature measurement point in the i-th layer reaction zone. In the longitudinal direction (m), Wc (i) is the catalyst charge (kg) in the i-th reaction zone, Ti (j) is the catalyst layer temperature (° C.) at the j-th measurement point in the i-th reaction zone , TB heat medium temperature (℃), RcMAX the maximum value of Rc (i), n is the reaction zone number, _{m i} represents the temperature measurement points in the reaction zone of the i-th layer. However, i = 1 to n. In addition, i and j are counted sequentially from the inlet side of the source gas.) A catalyst layer forming method, wherein the same catalyst layer as the catalyst layer formed by the catalyst layer forming method according to claim 4 is formed in another reaction tube.