Method for producing either or both of (meth)acrolein and (meth)acrylic acid

Abstract

This method uses a heat exchange reactor, which is internally provided with a reaction tube, and produces (meth)acrolein and / or (meth)acrylic acid by means of an oxidation reaction of raw materials supplied to the reaction tube while circulating a heat medium to outside of the reaction tube. In the longitudinal direction of the reaction tube, the reaction tube has i catalyst layers having different catalyst fill amounts per unit volume, wherein i is an integer greater than or equal to 2, and the aforementioned oxidation reaction satisfies formula (1).　(1) … ξ ≤ 0.275 (mol*K*k-1*W-1), given Equation (AAA).

Description

[Technical field]

[0001] The present invention relates to a method for producing either or both of (meth)acrolein and (meth)acrylic acid. This application claims priority based on Japanese Patent Application No. 2021-087587, filed on May 25, 2021, the contents of which are incorporated herein by reference. [Background technology]

[0002] Generally, when producing (meth)acrolein or (meth)acrylic acid by oxidation reaction, a large amount of reaction heat is generated, so a heat exchange reactor is widely used in which a heat transfer medium is circulated on the outside of the reaction tube to carry out the reaction. However, the flow of the heat transfer medium is not uniform inside the reactor, so there is a large deviation in the heat transfer medium temperature inside the reactor. Inside the reaction tube, which is in an area where the heat transfer medium temperature is high, the selectivity of the target product decreases due to the excessive progress of the reaction, which generates by-products and local catalyst deterioration. In addition, the generation of reaction heat that exceeds the heat removal capacity of the reactor may cause a runaway reaction.

[0003] As a measure against such unevenness in the temperature of the heat transfer medium in a heat exchanger reactor, for example, Patent Document 1 discloses a method for setting conditions related to the raw material gas flow rate and the heat removal capacity of the reactor in consideration of the heat balance of the heat transfer medium in a gas-phase oxidation reaction using a multi-tubular heat exchanger reactor equipped with a plurality of reaction tubes having at least a catalyst-filled catalyst layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2010-132584 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the conditions are set only by focusing on the heat balance of the heat transfer medium, the reaction tube may not be filled with the necessary amount of catalyst, the target production amount may not be achieved, or the continuous operation period of the reactor may be shortened. Alternatively, the reactor may be an excessively large facility for the production amount of the target product, which may increase the production cost.

[0006] Therefore, one of the objects of the present invention is to produce one or both of (meth)acrolein and (meth)acrylic acid with high selectivity by preventing runaway reaction in a heat exchange reactor and suppressing excessive reaction progress and local catalyst deterioration. Note that "(meth)acrolein" is a general term for acrolein and methacrolein, and "(meth)acrylic acid" is a general term for acrylic acid and methacrylic acid. [Means for solving the problem]

[0007] [1]: A method for producing one or both of (meth)acrolein and (meth)acrylic acid by an oxidation reaction of a raw material supplied to a heat exchange reactor equipped with a reaction tube inside while circulating a heat medium on the outside of the reaction tube, The reaction tube has a plurality of catalyst layers having different catalyst loading amounts per unit volume in a longitudinal direction of the reaction tube, the number of layers being i, where i is an integer of 2 or more; A method for producing one or both of (meth)acrolein and (meth)acrylic acid, wherein the oxidation reaction satisfies formula (1). ξ≦0.275(mol·K / h / W) …(1) however,

number

number

[10] : The method according to any one of [1] to [9], wherein F is 2.5 to 15 (mol / h).

[11] : The A is 0.03 to 0.6 (m 2The method according to any one of [1] to

[10] , wherein

[12] : The production method according to any one of [1] to

[11] , wherein the raw material is at least one selected from propylene, isobutylene, tert-butanol, and methyl tert-butyl ether, and one or both of the (meth)acrolein and (meth)acrylic acid are (meth)acrolein and (meth)acrylic acid.

[13] : The method according to any one of [1] to

[11] , wherein the raw material is (meth)acrolein, and one or both of the (meth)acrolein and (meth)acrylic acid are (meth)acrylic acid.

[14] : The method according to

[12] , wherein a catalyst having a composition represented by formula (I) is used in the catalyst layer. Mo a1 Bi b1 Fe c1 M d1 X e1 Y f1 Z g1 S h1 O i1 (I) In formula (I), Mo, Bi, Fe, Si, and O represent molybdenum, bismuth, iron, silicon, and oxygen, respectively. M represents at least one element selected from the group consisting of cobalt and nickel. X represents at least one element selected from the group consisting of chromium, lead, manganese, calcium, magnesium, niobium, silver, barium, tin, tantalum, and zinc. Y represents at least one element selected from the group consisting of phosphorus, boron, sulfur, selenium, tellurium, cerium, tungsten, antimony, and titanium. Z represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, and thallium. a1, b1, c1, d1, e1, f1, g1, h1, and i1 represent the atomic ratios of each element, and when a1=12, b1=0.01-3, c1=0.01-5, d1=1-12, e1=0-8, f1=0-5, g1=0.001-2, and h1=0-20, and i1 is the atomic ratio of oxygen necessary to satisfy the atomic valence of the element.

[15] The method according to

[13] , wherein a catalyst having a composition represented by formula (II) is used in the catalyst layer. P a2 Mo b2 V c2 Cu d2 X e2 Y f2 Z g2 O h2 (II) In formula (II), P, Mo, V, Cu, and O represent phosphorus, molybdenum, vanadium, copper, and oxygen, respectively. X represents at least one element selected from the group consisting of antimony, bismuth, arsenic, germanium, zirconium, tellurium, silver, selenium, silicon, tungsten, and boron. Y represents at least one element selected from the group consisting of iron, zinc, chromium, magnesium, tantalum, cobalt, manganese, barium, gallium, cerium, and lanthanum. Z represents at least one element selected from the group consisting of potassium, rubidium, cesium, and thallium. a2, b2, c2, d2, e2, f2, g2, and h2 represent the atomic ratios of each element, and when b2=12, a2=0.5 to 3, c2=0.01 to 3, d2=0.01 to 2, e2=0 to 3, f2=0 to 3, and g2=0.01 to 3, and h2 is the atomic ratio of oxygen necessary to satisfy the atomic valence of the above element. Effect of the Invention

[0008] According to the production method of the present invention, it is possible to produce one or both of (meth)acrolein and (meth)acrylic acid with high selectivity by preventing runaway reaction in a heat exchange reactor and suppressing excessive reaction progression and local catalyst deterioration. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic vertical sectional view showing an example of a heat exchange reactor used in the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described in detail. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits, and "A to B" means A or more and B or less. In addition, the dimensions of the figures illustrated in the following description are merely examples, and the present invention is not necessarily limited to them, and can be implemented with appropriate modifications within the scope that does not change the gist of the present invention.

[0011] The method for producing one or both of (meth)acrolein and (meth)acrylic acid of the present invention (hereinafter, "the method for producing one or both of (meth)acrolein and (meth)acrylic acid" may be simply referred to as "the production method") is a method using a heat exchange reactor equipped with a reaction tube inside, and carrying out an oxidation reaction of a raw material supplied to the reaction tube while circulating a heat medium outside the reaction tube, the reaction tube having i layers of multiple catalyst layers in the longitudinal direction of the reaction tube, each layer having a different catalyst loading amount per unit volume, where i is an integer of 2 or more. Furthermore, the production method of the present invention satisfies formula (1) in the oxidation reaction. ξ≦0.275(mol·K / h / W)···(1) however,

number

[0012] The reason for this is presumed to be as follows. In the production of one or both of (meth)acrolein and (meth)acrylic acid using a heat exchange reactor, as the reaction temperature increases, the heat generation rate in the reactor increases exponentially, while the heat removal rate increases only linearly. Therefore, as the reaction proceeds, the heat removal capacity of the reactor becomes insufficient, and the reaction temperature increases, causing the reaction to proceed excessively or local catalyst deterioration. Furthermore, excessive insufficiency in the heat removal capacity of the reactor may cause a runaway reaction. In contrast, by using a reaction tube equipped with multiple catalyst layers with different catalyst loading amounts and appropriately distributing the catalyst to each catalyst layer, it is possible to control the ratio of the heat generation rate and the heat removal rate of each catalyst layer equipped in the reactor while ensuring the required catalyst loading amount. In particular, the present invention focuses on the first catalyst layer having the highest raw material concentration, and controls the ratio of the heat generation rate and the heat removal rate in the catalyst layer. Then, by making the ratio of the heat generation rate and the heat removal rate in the first catalyst layer a value suitable for producing one or both of (meth)acrolein and (meth)acrylic acid, the ratio of the heat generation rate and the heat removal rate of each catalyst layer equipped in the reaction tube becomes appropriate, and the increase in reaction temperature can be suppressed. This suppresses reaction runaway, and one or both of (meth)acrolein and (meth)acrylic acid can be produced with high selectivity.

[0013] [Manufacturing method] The production method of the present invention can be suitably applied to a method for producing (meth)acrolein and (meth)acrylic acid using at least one selected from propylene, isobutylene, tert-butanol, and methyl tert-butyl ether as a raw material, or a method for producing (meth)acrylic acid using (meth)acrolein as a raw material. In particular, it is preferable to apply the method to a method for producing (meth)acrylic acid using (meth)acrolein as a raw material, and it is more preferable to apply the method to a method for producing methacrylic acid from methacrolein.

[0014] <Heat exchange reactor> The production method of the present invention uses a heat exchanger reactor equipped with a reaction tube inside. As the heat exchanger reactor, for example, a double-tube heat exchanger reactor, or industrially, a multi-tube heat exchanger reactor, can be used. An example of a multi-tube heat exchanger reactor is shown in Figure 1.

[0015] In FIG. 1, a reactor 1 has a reaction tube 2 and a baffle plate 3 therein. A raw material inlet 4 is provided at the bottom of the reactor 1, and a product outlet 5 is provided at the top. The inside of the reactor 1 is vertically divided into three regions by a first partition plate 9 on the raw material inlet 4 side and a second partition plate 10 on the product outlet 5 side. The reaction tubes 2 are provided so as to extend from the first partition plate 9 to the second partition plate 10, and both end faces of the reaction tube 2 open to the raw material inlet 4 side and the product outlet 5 side, respectively. A heat medium bath 8 through which a heat medium flows is provided outside the reaction tube 2 in the region between the first partition plate 9 and the second partition plate 10 in the reactor 1. A heat medium inlet 6 is provided near the first partition plate 9 on the side wall of the reactor 1, and a heat medium outlet 7 is provided near the second partition plate 10. The baffle plate 3 is provided in the region between the first partition plate 9 and the second partition plate 10 so as to be perpendicular to the longitudinal direction of the reaction tube 2. The raw material flows into the reactor 1 from the raw material inlet portion 4, flows through the reaction tube 2 from the raw material inlet side of the reaction tube 2, and flows out from the product outlet portion 5. The raw material inlet side of the reaction tube 2 means the end face on the raw material inlet portion 4 side. The heat transfer medium flows in from the heat transfer medium inlet portion 6, flows meandering around the outside of the reaction tube 2 from the raw material inlet portion 4 side to the product outlet portion 5 side due to the baffle plate 3, and flows out from the heat transfer medium outlet portion 7.

[0016] <Catalyst layer provided in reaction tube> In the reactor used in the production method of the present invention, the reaction tube has i layers of catalyst layers with different catalyst loading amounts per unit volume in the longitudinal direction of the reaction tube. Here, i is an integer of 2 or more. This means that the reaction tube has two or more catalyst layers in its longitudinal direction, and adjacent catalyst layers have different catalyst loading amounts per unit volume. In addition, "different catalyst loading amounts per unit volume" means that the catalyst loading amounts per unit volume differ by 1% or more. When the catalyst layer contains a diluent described later, this includes cases where the mixed ratio of the filled catalyst and diluent differs by 1% or more, or where the density of the catalyst or diluent differs by 1% or more. Note that a "catalyst layer" is considered to be a layer having a thickness of 100 mm or more in the longitudinal direction of the reaction tube.

[0017] To form a catalyst layer having a different catalyst loading amount per unit volume, for example, a method of mixing and loading a diluent and a catalyst so that the catalyst loading amount per unit volume is a desired value, or a method of loading catalysts of different shapes can be mentioned. From the viewpoint of catalyst production cost, the method of mixing and loading a diluent and a catalyst is preferred.

[0018] There are no particular limitations on the diluent, so long as it is an inactive substance that does not exhibit activity in the oxidation reaction for producing one or both of (meth)acrolein and (meth)acrylic acid. Examples of the inactive substance include silica, alumina, silica-alumina, silicon carbide, titania, magnesia, ceramic balls, stainless steel, etc.

[0019] There is no particular limitation on i, the number of catalyst layers, so long as it is an integer of 2 or more. From the viewpoint of reducing the load of the catalyst packing operation, i is preferably an integer of 4 or less, and more preferably 2. When i is 2, from the viewpoint of reaction heat control on the raw material inlet side of the reaction tube, it is preferable that the catalyst packing amount per unit volume in the first catalyst layer from the raw material inlet side of the reaction tube is smaller than the catalyst packing amount per unit volume in the second catalyst layer.

[0020] The length of the catalyst layer is not particularly limited, but from the viewpoint of the production amount of either or both of (meth)acrolein and (meth)acrylic acid, the length of the first catalyst layer from the raw material inlet of the reaction tube is preferably 0.5 m or more, more preferably 1.5 m or more. Also, from the viewpoint of production cost, the length of the first catalyst layer from the raw material inlet of the reaction tube is preferably 6 m or less, more preferably 4 m or less.

[0021] The reaction tube may have an inert material layer between the end of the raw material inlet side and the catalyst layer for the purpose of supporting the catalyst layer and preheating the raw material. The inert material layer is preferably made of the above-mentioned inert material alone. When the catalyst layer is formed by a method of mixing a diluent and a catalyst and filling the mixture, it is preferable to use the same inert material as the diluent used in the catalyst layer, since this simplifies the extraction and sieving operations after the oxidation reaction is completed.

[0022] <Catalyst> It is preferable that the catalyst packed in each catalyst layer is composed of common elements, and the difference in composition ratio of each element component is 10% or less.

[0023] When the production method of the present invention is a method for producing (meth)acrolein and (meth)acrylic acid using one or more raw materials selected from propylene, isobutylene, tert-butanol, and methyl tert-butyl ether, it is preferable to use a catalyst having a composition represented by formula (I) in the catalyst layer. Mo a1 Bi b1 Fe c1 M d1 X e1 Y f1 Z g1 S h1 O i1 (I) In formula (I), Mo, Bi, Fe, Si, and O represent molybdenum, bismuth, iron, silicon, and oxygen, respectively. M represents at least one element selected from the group consisting of cobalt and nickel. X represents at least one element selected from the group consisting of chromium, lead, manganese, calcium, magnesium, niobium, silver, barium, tin, tantalum, and zinc. Y represents at least one element selected from the group consisting of phosphorus, boron, sulfur, selenium, tellurium, cerium, tungsten, antimony, and titanium. Z represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, and thallium. a1, b1, c1, d1, e1, f1, g1, h1, and i1 represent the atomic ratios of each element, and when a1=12, b1=0.01-3, c1=0.01-5, d1=1-12, e1=0-8, f1=0-5, g1=0.001-2, and h1=0-20, and i1 is the atomic ratio of oxygen necessary to satisfy the atomic valence of each element described above.

[0024] When the production method of the present invention is a method for producing (meth)acrylic acid using (meth)acrolein as a raw material, it is preferable to use a catalyst having a composition represented by formula (II) in the catalyst layer. P a2 Mo b2 V c2 Cu d2 X e2 Y f2 Z g2 O h2 (II) In formula (II), P, Mo, V, Cu, and O represent phosphorus, molybdenum, vanadium, copper, and oxygen, respectively. X represents at least one element selected from the group consisting of antimony, bismuth, arsenic, germanium, zirconium, tellurium, silver, selenium, silicon, tungsten, and boron. Y represents at least one element selected from the group consisting of iron, zinc, chromium, magnesium, tantalum, cobalt, manganese, barium, gallium, cerium, and lanthanum. Z represents at least one element selected from the group consisting of potassium, rubidium, cesium, and thallium. a2, b2, c2, d2, e2, f2, g2, and h2 represent the atomic ratios of each element, and when b2=12, a2=0.5 to 3, c2=0.01 to 3, d2=0.01 to 2, e2=0 to 3, f2=0 to 3, and g2=0.01 to 3, and h2 is the atomic ratio of oxygen necessary to satisfy the atomic valence of each element described above.

[0025] There are no particular limitations on the shape and size of the catalyst, and it is possible to use a catalyst having a spherical, cylindrical, ring, star, or other shape formed by a normal tableting machine, extrusion machine, granulator, etc. Also, a supported catalyst in which a catalyst having the above-mentioned composition is supported on a carrier may be used. As the catalyst, catalysts of a variety of shapes may be used, but from the viewpoint of the production cost of the catalyst, it is preferable that the catalysts have the same shape.

[0026] <Oxidation reaction> In the present invention, a method for producing one or both of (meth)acrolein and (meth)acrylic acid by an oxidation reaction of a raw material will be described with reference to Fig. 1. The raw material flows in from a raw material inlet 4 and is supplied from the raw material inlet side of a reaction tube 2. Then, while removing reaction heat by circulating a heat medium through a heat medium bath 8 provided outside the reaction tube 2, the raw material is brought into contact with a catalyst layer equipped in the reaction tube 2, whereby one or both of (meth)acrolein and (meth)acrylic acid can be produced. The method for producing one or both of (meth)acrolein and (meth)acrylic acid of the present invention satisfies formula (1) in the oxidation reaction of the raw material. In formula (1), the value of ξ represents the ease of temperature change in the first catalyst layer from the raw material inlet side of the reaction tube. When ξ satisfies formula (1), the amount of catalyst distributed to the first catalyst layer is appropriate, and the ratio of heat generation rate to heat removal rate is suitable for the production of one or both of (meth)acrolein and (meth)acrylic acid. In formula (1), the upper limit of the value of ξ is preferably 0.24 (mol·K / h / W) or less, more preferably 0.12 (mol·K / h / W) or less, and even more preferably 0.06 (mol·K / h / W) or less. The lower limit of the value of ξ is preferably 0.002 (mol·K / h / W) or more. This allows the production cost relative to the production amount of one or both of (meth)acrolein and (meth)acrylic acid to be reduced. The lower limit of the ξ value is more preferably 0.004 (mol·K / h / W) or more, and further preferably 0.006 (mol·K / h / W) or more. Herein, in the case where the heat exchange type reactor has a plurality of reaction tubes, it is preferable that formula (1) is satisfied for 50% or more of the total number of the reaction tubes, more preferably that formula (1) is satisfied for 80% or more of the total number of the reaction tubes, and further preferably that formula (1) is satisfied for 90% or more of the total number of the reaction tubes.

[0027] The ratio τ of the catalyst loading amount of the first catalyst layer from the raw material inlet side of the reaction tube to the total catalyst loading amount of the reaction tube is represented by the formula (**).

[0028]

number

[0029] In the above formula (**), m1 is the catalyst packing amount (kg) in the first catalyst layer from the raw material inlet side of the reaction tube, mk is the catalyst packing amount (kg) in the kth catalyst layer from the raw material inlet side of the reaction tube, and k is an integer of 1 or more and i or less.

[0030] There is no particular limitation on τ as long as ξ=F×τ / (U×A) satisfies the formula (1), but it is preferable that τ satisfies the formula (2). 0.25≦τ≦0.5 (2)

[0031] By setting the value of τ to 0.25 or more, the heat generation amount in the second or subsequent catalyst layers from the raw material inlet side of the reaction tube is more suitably suppressed. In addition, by setting the value of τ to 0.5 or less, the productivity of one or both of (meth)acrolein and (meth)acrylic acid is improved. The lower limit of the value of τ is more preferably 0.26 or more, even more preferably 0.27 or more, and particularly preferably 0.28 or more. In addition, the lower limit of the value of τ is more preferably 0.48 or less, even more preferably 0.46 or less, and particularly preferably 0.45 or less. Herein, in the case where the heat exchange type reactor has a plurality of reaction tubes, it is preferable that formula (2) is satisfied for 50% or more of the total number of the reaction tubes, more preferably that formula (2) is satisfied for 80% or more of the total number of the reaction tubes, and further preferably that formula (2) is satisfied for 90% or more of the total number of the reaction tubes.

[0032] In the formula (*), U is the overall heat transfer coefficient (W / m) based on the inner surface area of ​​the reaction tube where both the first catalyst layer and the heat transfer medium are in contact. 2 / K). U can be calculated from the results of measuring the temperature distribution in a microregion of the first catalytic layer (hereinafter, the "microregion of the first catalytic layer" may be simply referred to as the "microregion") by supplying an inert gas consisting of 21% by volume of oxygen and 79% by volume of nitrogen to the reaction tube at a temperature 50°C lower than that of the heat transfer medium flowing outside the reaction tube. The microregion refers to a region obtained by dividing the reaction tube into 20 mm segments in the longitudinal direction. Here, the temperature change dT1 (K) in the longitudinal direction of the reaction tube in the microregion is obtained by the formula (***) when the difference between the temperature of the heat transfer medium flowing outside the reaction tube and the average temperature in the microregion is dT2 (K).

[0033] dT1 = U × inner surface area of ​​the reaction tube in contact with the micro-area (m 2) × dT2 / [mass flow rate of inert gas (g / s) × specific heat of inert gas (J / g / K)] (***)

[0034] U can be calculated by using the least squares method to find the value of U such that dT1 calculated by formula (***) coincides with the measured value of dT1. U is the arithmetic mean value obtained for 20 adjacent microregions. The microregions are set so that dT2 is 3°C or higher at at least one of the 20 microregions. When finding U, the same conditions as those for the oxidation reaction are used, except that the inert gas is supplied instead of the raw material at a temperature 50°C lower than the heat transfer medium flowing outside the reaction tube.

[0035] There is no particular limit to U as long as ξ satisfies formula (1). However, from the viewpoint of suppressing the amount of heat generated by the catalyst layer, it is preferable that U is 40 (W / m 2 / K) or more, and 60 (W / m 2 / K) or more, and 70 (W / m 2 / K) or more. From the economical viewpoint of preventing the reactor from becoming expensive, U is 400 (W / m 2 / K) or less, and 300 (W / m 2 / K) or less, and 150 (W / m 2 / K) or less is more preferable.

[0036] In addition, in the case where the heat exchange reactor has a plurality of reaction tubes, it is preferable that U satisfies the above-mentioned provision in 50% or more of the total number of the reaction tubes, more preferably that U satisfies the above-mentioned provision in 80% or more of the total number of the reaction tubes, and further preferably that U satisfies the above-mentioned provision in 90% or more of the total number of the reaction tubes. Examples of methods for adjusting U include changing the flow conditions of the heat transfer medium, changing the flow rate of the nitrogen gas, changing the proportion or shape of the catalyst in one catalyst layer, changing the material or shape of the diluent in the first catalyst layer, and changing the material, diameter, or thickness of the reaction tube.

[0037] In formula (*), F is the amount (mol / h) of the raw material fed to the reaction tube. When the heat exchange reactor has a plurality of reaction tubes, F is the amount (mol / h) of the raw material fed to each of the plurality of reaction tubes. F is not particularly limited as long as ξ satisfies formula (1), but from the viewpoint of maintaining the productivity of one or both of (meth)acrolein and (meth)acrylic acid, it is preferably 1 (mol / h) or more, more preferably 2.5 (mol / h) or more, and even more preferably 6.5 (mol / h) or more. In addition, from the viewpoint of suppressing the amount of heat generated by the catalyst layer, F is preferably 20 (mol / h) or less, more preferably 15 (mol / h) or less, and even more preferably 10.5 (mol / h) or less. Herein, in the case where the heat exchange type reactor has a plurality of reaction tubes, it is preferable that F satisfies the above regulation in 50% or more of the total number of the reaction tubes, more preferably that F satisfies the above regulation in 80% or more of the total number of the reaction tubes, and further preferably that F satisfies the above regulation in 90% or more of the total number of the reaction tubes.

[0038] A in the formula (*) is the inner surface area (m 2 ) A is not particularly limited as long as ξ satisfies formula (1). However, from the viewpoint of suppressing the amount of heat generated in the catalyst layer, it is preferable to set A at 0.03 (m 2 ) or more, and 0.06 (m 2 ) or more, and 0.09 (m 2 ) or more. From the economical viewpoint of preventing the reactor from becoming expensive, A is preferably 0.6 (m 2 ) or less, and 0.4 (m 2 ) or less, and more preferably 0.25 (m 2 ) or less is even more preferable. In addition, in the case where the heat exchange type reactor has a plurality of reaction tubes, it is preferable that A satisfies the above provision in 50% or more of the total number of the reaction tubes, more preferably that A satisfies the above provision in 80% or more of the total number of the reaction tubes, and further preferably that A satisfies the above provision in 90% or more of the total number of the reaction tubes.

[0039] In the production method of the present invention, the raw material can be supplied to the reaction tube as a raw material gas containing the raw material. The raw material concentration in the raw material gas is preferably 1 to 20% by volume, more preferably 3 to 10% by volume. As described above, when the present invention is a method for producing (meth)acrolein and (meth)acrylic acid, the raw material is at least one selected from propylene, isobutylene, tert-butanol, and methyl tert-butyl ether, and when the present invention is a method for producing (meth)acrylic acid, the raw material is (meth)acrolein.

[0040] The raw material gas preferably contains 5 to 15% by volume of oxygen. From the viewpoint of economic efficiency, air is preferable as the oxygen source. If necessary, a gas enriched with oxygen by adding pure oxygen to air may be used. The raw material gas preferably contains 5 to 50% by volume of water vapor. The raw material gas may be obtained by diluting the raw material, oxygen, and water vapor with an inert gas such as nitrogen, carbon dioxide, etc. The raw material gas may contain a small amount of impurities such as lower saturated aldehydes, but it is preferable that the amount is as small as possible.

[0041] The space velocity of the raw material in the catalyst layer is 200 to 5000 h -1 is preferred. In the oxidation reaction of the raw material, the reaction pressure is preferably atmospheric pressure to several atmospheres. The temperature of the heat transfer medium flowing outside the reaction tube is preferably 230 to 450° C. The lower limit of the temperature of the heat transfer medium is more preferably 250° C. or more, and the upper limit is more preferably 400° C. or less.

[0042] As described above, the method of the present embodiment can improve the selectivity of (meth)acrylic acid in the synthesis of (meth)acrolein and / or (meth)acrylic acid. EXAMPLES

[0043] The present invention will be specifically described below with reference to examples, although the present invention is not limited to these.

[0044] In the examples and comparative examples described later, ξ and τ are as follows:

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number

[0045] (Catalyst composition ratio) The atomic ratio of each element was determined by dissolving the catalyst in ammonia water and analyzing the components by ICP (inductively coupled plasma) emission spectrometry. Equipment used: Inductively coupled plasma (ICP) optical emission spectrometer (Perkin Elmer Optima 8300 ICP-OES Spectrometer)

[0046] (Calculation of overall heat transfer coefficient U) The overall heat transfer coefficient U was calculated from the results of measuring the temperature distribution in a micro region of the first catalyst layer by supplying an inert gas consisting of 21 vol% oxygen and 79 vol% nitrogen to the reaction tube at a temperature 50°C lower than that of the heat transfer medium flowing outside the reaction tube.

[0047] (Analysis of raw materials and products) The raw materials and products were analyzed by gas chromatography (apparatus: Shimadzu GC-2014, column: J&W DB-FFAP, 30 m×0.32 mm, film thickness 1.0 μm). The reaction rate of methacrolein, the selectivity of the produced methacrylic acid, and the yield of methacrylic acid are defined as follows. Methacrolein reaction rate (%) = (β / α) × 100 Methacrylic acid selectivity (%) = (γ / β) × 100 Methacrylic acid yield (%) = (γ / α) × 100 Here, α is the amount (mol) of methacrolein supplied, β is the amount (mol) of methacrolein reacted, and γ is the amount (mol) of methacrylic acid produced.

[0048] (Evaluation of heat generation in catalyst layer) The difference (ΔTmax) between the temperature of the hottest part of the catalyst layer and the temperature of the heat transfer medium flowing outside the reaction tube was used as an index for evaluating the amount of heat generated in the catalyst layer. ΔTmax was measured as follows. The temperature of the catalyst layer was measured using a thermocouple inserted into a protective tube installed at the center of a cross section perpendicular to the longitudinal direction of the reaction tube. The protective tube was isolated from the reaction system, and the position where the temperature was measured could be changed by adjusting the length of the inserted thermocouple. The difference between the measured catalyst layer temperature and the heat transfer medium temperature was taken as ΔT, and the ΔT distribution was calculated. The maximum ΔT in the obtained ΔT distribution was taken as ΔTmax.

[0049] <Example 1> Methacrylic acid was produced by the oxidation reaction of methacrolein as described below using a multi-tube heat exchanger reactor equipped with a heat medium bath as shown in Figure 1. The reactor was equipped with a reaction tube made of SUS304 with an inner diameter of 27.2 mm and a length of 6 m.

[0050] In each reaction tube, the composition ratio excluding oxygen is P 1.1 Mo 12 V 0.6 Cu 0.1 Fe 0.05 Cs 1.3 Two catalyst layers were formed using a cylindrical catalyst with a diameter of 6 mm and a height of 5 mm. The first catalyst layer from the raw material inlet side of the reaction tube was packed with a mixture of 1000 g of catalyst and 250 g of alumina balls with a diameter of 5 mm as a diluent. The second catalyst layer was packed with 2500 g of catalyst. The length and τ value of each catalyst layer are shown in Table 1. An inert material layer made of alumina balls with a diameter of 5 mm was formed between the end of the raw material inlet side of the reaction tube and the catalyst layer.

[0051] Next, while the heat medium was circulating through the heat medium bath installed outside the reaction tube, a raw material gas consisting of 6.0% by volume of methacrolein, 10% by volume of oxygen, 10% by volume of steam, and 74.0% by volume of nitrogen was introduced at a space velocity of 1700 h -1 The mixture was fed to the reaction tube at 50% by mass of potassium nitrate and 50% by mass of sodium nitrite, and the heat medium temperature was set to 310° C. The methacrolein feed rate F, overall heat transfer coefficient U, ξ value, and methacrolein reaction rate at this time are shown in Table 1. After that, continuous operation was carried out for 40 days while maintaining the reaction rate by adjusting the temperature of the heat transfer medium. During the continuous operation, the temperature of the catalyst layer was measured periodically and the ΔT distribution was calculated. The ΔTmax during the continuous operation period was 31°C in the first catalyst layer and 22°C in the second catalyst layer. In addition, the average selectivity of methacrylic acid during the continuous operation period was 82%.

[0052] <Comparative Example 1> Using the same multi-tube heat exchanger reactor as in Example 1, methacrylic acid was produced by the oxidation reaction of methacrolein as described below. In each reaction tube, one catalyst layer was formed using the same catalyst as in Example 1. The catalyst layer was filled with 3500 g of catalyst only. The length of the catalyst layer and the value of τ are shown in Table 1. An inert material layer similar to that in Example 1 was formed between the end of the raw material inlet side of the reaction tube and the catalyst layer. Next, the oxidation reaction was carried out by supplying the raw material gas in the same manner as in Example 1 while circulating the heat transfer medium in the same manner as in Example 1. The methacrolein supply amount F, the overall heat transfer coefficient U, the value of ξ, and the methacrolein reaction rate are shown in Table 1. After that, continuous operation was carried out while maintaining the reaction rate by adjusting the temperature of the heat transfer medium, but two days after the start of operation, the ΔTmax of the catalyst layer reached 200 ° C., and operation had to be stopped. In addition, the methacrylic acid selectivity before operation was stopped was 77%.

[0053] <Examples 2 to 4 and Comparative Examples 2 to 3> A simulation was created to reproduce the reaction results of Example 1, as described below. The same conditions as in Example 1 were applied for the formation of the catalyst layer and the supply of the reaction gas, and the reaction rate was calculated for each microregion divided from the inlet of the reaction tube in the longitudinal direction of the reaction tube with respect to the temperature and concentration. From the obtained reaction rate, a material balance equation and a heat balance equation were created in the longitudinal direction of the reaction tube, and the temperature in the region adjacent to the product outlet side and the concentration of each compound present in the reaction tube were calculated. This was repeated up to the region closest to the product outlet side, and the reaction rate parameters were fitted so that the same ΔTmax, methacrolein reaction rate, and methacrylic acid selectivity as in Example 1 were obtained. The change in the amount of substance in the microregion in the longitudinal direction of the reaction tube was calculated using the stoichiometric coefficient of the compound based on the reaction formula of each reaction occurring in the reaction tube and the reaction rate per volume (mol / m 3 / s) and the volume of the micro area (m 3 ) is M1, the sum of M1 (mol / s) for all reactions occurring in the reaction tube is obtained. The temperature change dT1' (K) in the longitudinal direction of the reaction tube in the micro region is calculated by the reaction rate per volume (mol / m 3 / s), the heat of reaction (J / mol), and the volume of the micro region (m 3 ) is M2(W), which is obtained by equation (***)'. dT1' = [U × inner surface area of ​​the reaction tube in contact with the micro-area (m 2 ) × dT2' + sum of M2 for all reactions occurring in the reaction tube] / [mass flow rate of raw gas (g / s) × specific heat of raw gas (J / g / K)] ··· (***)'

[0054] Using the prepared simulation, it was confirmed that when the same heat transfer medium flow conditions as in Example 1 were used, the same ΔTmax, methacrolein reaction rate, and methacrylic acid selectivity as in Example 1 could be obtained.

[0055] Next, the simulation prepared above was carried out. The length of the catalyst layer, the amount of catalyst packed, the value of τ, the value of U, and the value of ξ in each Example and Comparative Example are shown in Table 1. The flow conditions of the heat transfer medium and the supply conditions of the raw material gas were the same as in Example 1. The ΔTmax, methacrolein reaction rate, and methacrylic acid selectivity obtained by the simulation are shown in Table 1.

[0056] [Table 1]

[0057] As shown in Table 1, Example 1, in which the oxidation reaction of methacrolein was carried out under the conditions satisfying formula (1), was able to perform continuous operation for 40 days with a higher methacrylic acid selectivity than the Comparative Example. Examples 2 to 4 also showed stable ΔTmax and good methacrylic acid selectivity. On the other hand, in Comparative Example 1, the heat generation amount of the catalyst layer increased rapidly, so the operation was stopped in 2 days, and the methacrylic acid selectivity was also low. In addition, Comparative Examples 2 and 3 had a high ΔTmax compared to the examples, indicating that the heat generation amount in the first catalyst layer was large compared to the heat removal capacity of the reactor. [Industrial Applicability]

[0058] According to the present invention, by preventing runaway reaction in a heat exchange reactor and suppressing excessive reaction progress and local catalyst deterioration, one or both of (meth)acrolein and (meth)acrylic acid can be produced with high selectivity, and thus the present invention is industrially useful. [Explanation of symbols]

[0059] 1. Reactor 2. Reaction tube 3. Baffle plate 4...Raw material inlet 5...Product outlet section 6...Heating medium inlet 7...Heating medium outlet part 8...heat medium bath 9. First partition plate 10 Second partition plate

Claims

1. A method for producing (meth)acrylic acid by an oxidation reaction of (meth)acrolein, which is a raw material supplied to a heat exchange reactor equipped with a reaction tube inside, while a heat medium is circulated outside the reaction tube, comprising the steps of: The reaction tube has a plurality of catalyst layers having different catalyst packing amounts per unit volume in a longitudinal direction of the reaction tube, the number of layers being i, where i is an integer of 2 or more, The method for producing (meth)acrylic acid, wherein the oxidation reaction satisfies formula (1). ξ≦0.275 (mol・K / h / W)…(1) however, [0010] In the formula (*), m1 is the catalyst packing amount (kg) in the first catalyst layer from the raw material inlet side of the reaction tube, mj is the catalyst packing amount (kg) in the jth catalyst layer from the raw material inlet side of the reaction tube, j is an integer of 1 to i, F is the supply amount (mol / h) of the raw material to the reaction tube, A is the inner surface area (m ２ ), and U is the overall heat transfer coefficient (W / m) based on the inner surface area of ​​the reaction tube where the first catalyst layer and the heat transfer medium are in contact with each other. ２ / K).

2. The method according to claim 1 , wherein the oxidation reaction further satisfies formula (1′). 0.002≦ξ≦0.275 (mol・K / h / W) …(1')

3. The method according to claim 1 , further comprising satisfying formula (1″) in the oxidation reaction. ξ≦0.24 (mol・K / h / W) …(1”)

4. The method according to claim 1 , wherein the oxidation reaction further satisfies formula (2). 0.25≦τ≦0.5 ... (2) however, [0025] In the formula (**), m1 is a catalyst packing amount (kg) in the first catalyst layer from the raw material inlet side of the reaction tube, mk is a catalyst packing amount (kg) in the kth catalyst layer from the raw material inlet side of the reaction tube, and k is an integer of 1 or more and i or less.

5. The method according to claim 4 , wherein the oxidation reaction further satisfies formula (2′). 0.26≦τ≦0.5 ... (2')

6. 2. The method according to claim 1, wherein the number i of catalyst layers provided in the reaction tube is 2 to 4.

7. The U is 40 to 400 (W / m ２ / K).

8. The U is 50 to 300 (W / m ２ / K).

9. The method according to claim 1, wherein F is 1 to 20 (mol / h).

10. The F is 2.5 to 15 (mol h －１ 2. The method according to claim 1 , wherein

11. The A is 0.03 to 0.6 (m ２ 2. The method according to claim 1 , wherein

12. The method according to claim 1 , wherein the catalyst layer uses a catalyst having a composition represented by formula (II): P ａ２ Mo ｂ２ V ｃ２ Cu ｄ２ X ｅ２ Y ｆ２ Z ｇ２ O ｈ２ ・・・(--) In formula (II), P, Mo, V, Cu, and O represent phosphorus, molybdenum, vanadium, copper, and oxygen, respectively. X represents at least one element selected from the group consisting of antimony, bismuth, arsenic, germanium, zirconium, tellurium, silver, selenium, silicon, tungsten, and boron. Y represents at least one element selected from the group consisting of iron, zinc, chromium, magnesium, tantalum, cobalt, manganese, barium, gallium, cerium, and lanthanum. Z represents at least one element selected from the group consisting of potassium, rubidium, cesium, and thallium. a2, b2, c2, d2, e2, f2, g2, and h2 represent the atomic ratios of each element, and when b2=12, a2=0.5 to 3, c2=0.01 to 3, d2=0.01 to 2, e2=0 to 3, f2=0 to 3, g2=0.01 to 3, and h2 is the atomic ratio of oxygen necessary to satisfy the valence of the element.

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