Method for producing unsaturated aldehyde and device for producing unsaturated aldehyde

Abstract

The present invention relates to a method for producing a corresponding unsaturated aldehyde by partially oxidizing an olefin using a fixed bed multi-tube reactor. The fixed bed multi-tube reactor has a plurality of reaction tubes and a reaction bath that adjusts the temperature of the plurality of reaction tubes. More than two catalyst layers are arranged in the reaction tube in the gas flowing direction. When the reaction bath temperature at which the yield of the unsaturated aldehyde is highest is A (DEG C), and the reaction bath temperature at which the yield is 1.0% lower than the maximum value is A1 (DEG C) and A2 (DEG C), the following formulae (1) and (2) are satisfied. A1 < A < A2 (1); (A2-A1) > = 10 (2).

Description

Technical Field

[0001] The present invention relates to a method and a device for producing corresponding unsaturated aldehydes by gas-phase catalytic oxidation of olefins using molecular oxygen or a gas containing molecular oxygen. Background Art

[0002] Industrially, methods for producing corresponding unsaturated aldehydes using olefins or alcohols that can generate olefins by intramolecular dehydration reactions thereof as raw materials are widely practiced. Among them, many catalysts for synthesizing acrolein by gas-phase catalytic oxidation of propylene with molecular oxygen have been proposed.

[0003] In this gas phase system oxidation reaction, from the viewpoint of productivity, the yield is given the most importance. Therefore, as an improvement of the constituent components of the catalyst, the technology related to the atomic ratio of iron, cobalt and nickel is recorded in patent documentation 1. The technology related to the atomic ratio of iron relative to cobalt and / or nickel is recorded in patent documentation 2. The technology related to the optimization of the atomic ratio of each element relative to platinum and the atomic ratio of nickel relative to bismuth, the atomic ratio of nickel relative to alkali metal components, and the atomic ratio of bismuth relative to alkali metal components are recorded in patent documentation 3. In addition, the improvement of the composition ratio of bismuth relative to platinum is recorded in patent documentation 4.

[0004] In addition, since the reaction system is accompanied by violent heat release, the generation of local high-temperature parts (hot spots) in the catalyst layer becomes a big problem. Hot spots generally refer to the maximum temperature in the catalyst layer, which is usually generated in the catalyst layer on the gas inlet side with high raw material concentration, but may also be generated in the highly active catalyst layer located on the gas outlet side due to deactivation of the catalyst on the inlet side, sudden interference factors, and changes in various conditions. The interference factors mentioned here refer to, for example, changes in the flow rate of the heat medium supplied to the reaction bath jacket and changes in the flow rate of the raw gas caused by the air temperature.

[0005] The generation of hot spots can lead to shortened catalyst life, reduced yields due to excessive oxidation reactions, and sometimes even runaway reactions. Therefore, in order to suppress the hot spot temperature, some techniques for controlling the activity of the catalyst filled in the portion where the hot spot is generated have been proposed.

[0006] For example, Patent Document 5 discloses a technique for reducing the hot spot temperature by using a catalyst whose activity is adjusted by changing the loading amount and by using a catalyst whose activity is adjusted by changing the calcination temperature of the catalyst. Patent Document 6 discloses a technique for using a catalyst whose activity is adjusted by changing the apparent density ratio of the catalyst. Patent Document 7 discloses a technique for using a catalyst whose activity is adjusted by changing the content of the inactive component of the catalyst molded body and changing the occupied volume of the catalyst molded body, the type and / or amount of the alkali metal, and the calcination temperature of the catalyst. Patent Document 8 discloses a technique for setting a reaction zone in which the occupied volume of the catalyst molded body is changed and mixing an inactive substance in at least one reaction zone. Patent Document 9 discloses a technique for using a catalyst whose activity is adjusted by changing the calcination temperature of the catalyst. Patent Document 10 discloses a technique for using a catalyst whose activity is adjusted by changing the occupied volume of the catalyst, the calcination temperature, and / or the type and amount of the alkali metal.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2003-164763

[0010] Patent Document 2: Japanese Patent Application Publication No. 2003-146920

[0011] Patent Document 3: International Publication No. 2014 / 181839

[0012] Patent Document 4: International Publication No. 2016 / 136882

[0013] Patent Document 5: Japanese Patent Application Laid-Open No. 10-168003

[0014] Patent Document 6: Japanese Patent Application Publication No. 2004-002209

[0015] Patent Document 7: Japanese Patent Application Publication No. 2001-328951

[0016] Patent Document 8: Japanese Patent Application Publication No. 2005-320315

[0017] Patent Document 9: Japanese Patent Application Laid-Open No. 8-3093

[0018] Patent Document 10: Japanese Patent Application Publication No. 2001-226302

[0019] Patent Document 11: Japanese Patent No. 6912153 Summary of the invention

[0020] Problems to be solved by the invention

[0021] However, even if the yield is improved by the above method, the yield of the target product is also difficult to be said to be sufficient, because the use amount of the olefin required for the manufacture is affected, the manufacturing cost is greatly affected, so it is necessary to improve. In addition, due to the continuous operation with low yield and the generation of by-products in large quantities, a large load is caused to the purification process, resulting in the problem of the time and running cost rising spent in the purification process. In addition, according to the type of by-products, sometimes they also can be deposited on the catalyst surface, in the gas flow path near the catalyst, because they cover the necessary reactive sites on the catalyst surface and reduce the activity of the catalyst, therefore it is necessary to forcibly improve the activity, and the reaction bath temperature has to be increased. Then, the catalyst is subjected to thermal stress, causing the reduction of life and the reduction of selectivity, and also leading to the further reduction of yield.

[0022] In addition, there are no adequate countermeasures for stable operation, including suppression of hot spots. For example, in industrial equipment, there are sometimes fluctuations in the heat removal capacity of the reactor structure, the temperature distribution of the heat medium in the horizontal and vertical directions, and the distribution of the gas flow rate in each reaction tube, and it is almost impossible to use the catalyst in the same state in all reaction tubes.

[0023] When analyzing the catalyst used in industrial equipment, it is sometimes found that the catalyst in the raw gas inlet part is concentratedly degraded in the reaction tube, the catalyst is slowly degraded as a whole, and the catalyst in the raw gas outlet part is more surprisingly degraded than the catalyst in the inlet part. This suggests the possibility that the hot spot temperature of the catalyst layer on the raw gas outlet side is abnormally high, which may sometimes cause a runaway reaction. It is predicted that the reason is that due to the change in the diameter of the reaction tube in the above-mentioned industrial equipment, the change in the heat removal capacity from the reactor structure, the temperature distribution of the heat medium in the horizontal and vertical directions, and the gas flow rate distribution of each reaction tube, the conversion rate of the raw hydrocarbon is different, and the shape of the temperature distribution is different. As a subject, the development of a technology that can maintain the reaction more safely and stably for a long time even when various variable factors overlap is listed. Assuming that the equipment stops due to an abnormal reaction, the catalyst life is shortened due to the loss caused by the unproduced part during the period, the abnormal temperature, and the atmosphere. When a runaway reaction occurs, it is possible to cause huge losses such as damage to the industrial plant equipment itself and accidents. As described above, in particular, in a multi-tubular reactor, since a plurality of reactors are present, it is more desired to maintain a stable yield in a wide range of reaction bath temperature and to improve stable operation.

[0024] As a manufacturing technology to date, the following multi-layer filling method is adopted: a catalyst with low activity is used on the gas inlet side of the reaction tube, a catalyst with high activity is used as the catalyst on the gas outlet side of the reaction tube, and the filling length of the catalyst layer near the gas outlet side is made longer than that on the gas inlet side.

[0025] In particular, in the method of producing acrolein from propylene, a method for improving the yield of acrolein is described in, for example, Patent Document 11, but other problems may arise. That is, as described above, a catalyst with high activity is generally used in the catalyst on the outlet side of the reaction gas by multi-layer filling of the catalyst, but whether the hot spot temperature (PTf) of the most active outlet side catalyst changes sharply with the reaction bath temperature (BT) becomes an important issue from the perspective of stable operation of the equipment. This is because, when PTf changes sharply with BT (ΔPTf / ΔBT is high), due to a slight change in the reaction bath temperature and the difference in the reaction bath temperature between multiple reaction tubes, the hot spot changes sharply on the catalyst on the outlet side with the highest activity, thereby making it easier to produce thermal runaway, and the damage and explosion of the reaction tube associated therewith. In addition, when PTf is high, since the heat release on the reactor outlet side is large, the gas temperature at the reactor outlet is high, and a decrease in the yield of acrolein caused by the cold flame reaction (cold flame) of acrolein, the accumulation (coking or scaling) of carbonaceous precipitates on the outlet side of the reaction tube caused by the auto-oxidation reaction of acrolein, and the blockage in the reaction tube caused by this may occur.

[0026] As a background for the above-mentioned problems, the reasons why ΔPTf / ΔBT becomes high in the method for producing acrolein from propylene are described below. That is, in the case of producing acrolein from propylene, acrylic acid, which is a product of stepwise oxidation, is captured as a by-product, so a reactor and a process are designed so that stepwise oxidation does not occur. For example, the following can be cited: (1) gas convection and stepwise oxidation occur at low load (= low space velocity of raw material propylene), so a high load condition is set; (2) the filling amount of inactive substances arranged at the raw material gas inlet portion is reduced; (3) in order to suppress the decrease in acrolein yield caused by the stepwise oxidation reaction, the oxygen / propylene ratio at the catalyst layer inlet is set low; and (4) in order to compensate for the decrease in the overall activity of the catalyst caused by the above, the outlet pressure is set high, etc. For these reasons, in the method for producing acrolein from propylene in particular, PTf tends to reach the highest temperature in all catalyst layers filled with multiple layers, and PTf tends to change sensitively with BT.

[0027] Here, the specific calculation method of ΔPTf / ΔBT is as follows. That is, when all the measured measurement points of the three points or more of the peak temperature (PTf) closest to the outlet side and BT within the range of A1 and A2 described later are plotted in the form of a scatter plot, the slope of the approximate straight line based on the least squares method, which has an intercept with the peak temperature closest to the outlet side as the vertical axis and is assumed to be a linear function relative to BT, is defined as ΔPTf / ΔBT. In addition, when there are two measurement points, the slope of the straight line passing through the two points is set to ΔPTf / ΔBT. The measurement points are set in such a way that the difference (BT2-BT1) between the reaction bath temperature BT1 of the measurement point with the lowest reaction bath temperature (BT) and the reaction bath temperature BT2 of the measurement point with the highest reaction bath temperature is more than 30% of A2-A1.

[0028] As described above, in particular, in the method for producing acrolein from propylene, it is not known what kind of catalyst and its filling method and operation management method should be used to ensure stable operation of the equipment under the above-mentioned reactor and process restrictions. In addition, since the stable operation is focused on the peak temperature closest to the outlet side, it is not known what kind of catalyst and its filling method are preferred.

[0029] Means used to solve problems

[0030] The present inventors have conducted in-depth research on these above-mentioned current situations and problems, and found that by filling the catalyst in a manner that expands the reaction bath temperature region (hereinafter referred to as the operation window) in which the acrolein yield is stable, stable equipment operation can be performed at a high yield. In addition, it is also found that when the catalyst is filled in a manner that a certain relationship can be formed between the sum of the field point exothermic temperatures of the catalyst layer closest to the outlet side and the sum of the field point exothermic temperatures of all catalyst layers, PTf can change smoothly relative to BT (ΔPTf / ΔBT can be reduced), and the yield of unsaturated aldehydes is improved, and stable equipment operation can be performed at a higher yield. The present invention can be applied not only to the reaction of producing acrolein from propylene, but also to the reaction of producing methacrolein from tertiary butyl alcohol and / or isobutylene, for example.

[0031] That is, the present invention relates to the following 1) to 11).

[0032] 1) A method for producing an unsaturated aldehyde, which is a method for producing the corresponding unsaturated aldehyde by partially oxidizing an olefin using a fixed bed multi-tubular reactor, wherein:

[0033] The fixed bed multi-tube reactor comprises a plurality of reaction tubes and a reaction bath for adjusting the temperature of the plurality of reaction tubes.

[0034] In the reaction tube, two or more catalyst layers are arranged in the gas flow direction.

[0035] When the reaction bath temperature when the yield of unsaturated aldehyde is the highest is A (°C), and the reaction bath temperatures when the yield is 1.0 percentage point lower than the highest value are A1 (°C) and A2 (°C), the following equations (1) and (2) hold.

[0036] A1<A<A2 (1)

[0037] (A2-A1)≥10 (2)

[0038] 2) The method for producing an unsaturated aldehyde according to 1) above, wherein the following formula (3) holds true for Sf and St when the unsaturated aldehyde is produced at the reaction bath temperature A (°C).

[0039] (Sf / St)×100≤42.0 (3)

[0040] Here, Sf and St are determined by the following operation steps (a) to (c).

[0041] (a) disposing p (p is an integer greater than or equal to 2) thermocouples at equal intervals in the entire gas flow direction of the two or more catalyst layers provided in the reaction tube, and using the thermocouples to obtain the field point temperatures T1 at p measurement points in the reaction tube when producing unsaturated aldehyde at a reaction bath temperature A (° C.) j (℃)(j is 1~p).

[0042] (b) For each of the measurement points, calculate the field point temperature T1 j The value obtained by subtracting the reaction bath temperature A (°C) from the reaction bath temperature (T1 j -A) field point exothermic temperature T2 j Among them, in T1 j -A is a negative value, the field heat release temperature T2 of the measurement point j Set to 0.

[0043] (c) lowering the field exothermic temperature T2 of all the measuring points in the reaction tube j The total value of is set as St. The field point heat release temperature T2 of the measurement point set at the catalyst layer closest to the outlet side is set as k The total value (k is 1 to q, q is the number of measurement points provided in the catalyst layer closest to the outlet side, q<p) is referred to as Sf.

[0044] 3) The method for producing an unsaturated aldehyde according to 1) or 2) above, wherein the catalytically active component contained in the catalyst layer closest to the inlet side of the reaction raw material gas has a composition represented by the following formula (I-1).

[0045] Mo a1 Bib1 Ni c1 Co d1 Fe e1 X f1 Cs g1 Z h1 O i1 (I-1)

[0046] (In the formula, Mo, Bi, Ni, Co, Fe, Cs and O represent molybdenum, bismuth, nickel, cobalt, iron, cesium and oxygen respectively, X represents at least one element selected from tungsten, antimony, tin, zinc, chromium, manganese, magnesium, silicon, aluminum, cerium and titanium, Z represents at least one element belonging to Group 1 to Group 16 of the periodic table and selected from elements other than the above-mentioned Mo, Bi, Ni, Co, Fe, Cs, O and X, a1, b1, c1, d1, e1, f1, g1, h1 and i1 represent the atomic numbers of molybdenum, bismuth, nickel, cobalt, iron, X, Cs, Z and oxygen respectively, when a1=12, 0<b1≤7.0, 0≤c1≤10, 0<d1≤10, 0<e1≤5.0, 0≤f1≤2.0, 0<g1≤3.0, 0≤h1≤5.0 are satisfied, and i1 is a value determined by the oxidation state of each element.)

[0047] 4) The method for producing an unsaturated aldehyde according to any one of 1) to 3) above, wherein the catalytically active component contained in the catalyst layer closest to the outlet side of the reaction raw material gas has a composition represented by the following formula (I-2).

[0048] Mo a2 Bi b2 Ni c2 Co d2 Fe e2 X f2 K g2 Z h2 O i2 (I-2)

[0049] (In the formula, Mo, Bi, Ni, Co, Fe and K represent molybdenum, bismuth, nickel, cobalt, iron and potassium respectively, X represents at least one element selected from tungsten, antimony, tin, zinc, chromium, manganese, magnesium, silicon, aluminum, cerium and titanium, Z represents at least one element selected from elements belonging to Groups 1 to 16 of the periodic table other than the above-mentioned Mo, Bi, Ni, Co, Fe, K, O and X, a2, b2, c2, d2, e2, f2, g2, h2 and i2 represent the atomic numbers of molybdenum, bismuth, nickel, cobalt, iron, X, K, Z and oxygen respectively, when a2=12, 0<b2≤7.0, 0≤c2≤10, 0<d2≤10, 0<e2≤5.0, 0≤f2≤2.0, 0≤g2≤3.0, 0≤h2≤5.0 are satisfied, and i2 is a value determined by the oxidation state of each element.)

[0050] 5) The method for producing an unsaturated aldehyde according to any one of 1) to 4) above, wherein the reaction bath temperature is 310° C. or higher and 340° C. or lower.

[0051] 6) The method for producing an unsaturated aldehyde according to any one of 1) to 5) above, wherein the volume ratio of oxygen to olefin in the reaction raw material gas (oxygen / olefin) is 1.0 or more and 1.8 or less.

[0052] 7) The method for producing an unsaturated aldehyde according to any one of 1) to 6) above, wherein the reaction tube does not have an inert layer at a position closer to the inlet side than the catalyst layer.

[0053] 8) The method for producing an unsaturated aldehyde according to any one of 1) to 7) above, wherein

[0054] In the reaction tube, three catalyst layers are arranged in the gas flow direction.

[0055] The ratio of the sum of the filling lengths of the first layer and the second layer to the filling length of the third layer from the inlet side of the reaction tube ((filling length of the first layer+filling length of the second layer) / filling length of the third layer) is 1.5 or more and 3.5 or less.

[0056] 9) The method for producing an unsaturated aldehyde according to any one of 1) to 8) above, wherein

[0057] In the reaction tube, more than two catalyst layers are arranged in the gas flow direction, and the type of catalyst, dilution rate and filling length of each catalyst layer are set in such a way that akt / akn defined by the following formulas (II), (III) and (IV) is greater than 1.41 and less than 10.00.

[0058] The reaction rate of the catalyst k=-Ln(1-x / 100) (II)

[0059] The actual reaction rate of the catalyst layer ak = (the dilution rate of the catalyst layer) × (the filling length of the catalyst layer) × (the reaction rate of the catalyst in the catalyst layer k) (III)

[0060] akt / akn = (value obtained by adding up the substantial reaction rates ak of all catalyst layers) / (substantial reaction rate ak of the catalyst layer closest to the outlet of the reaction tube) (IV)

[0061] Here, x is the raw material gas conversion rate (%) when the catalyst is filled in a differential system reactor and the partial oxidation reaction of the olefin is carried out at a reaction bath temperature of 360°C.

[0062] 10) An unsaturated aldehyde production device, which is a device for producing a corresponding unsaturated aldehyde by partially oxidizing an olefin, wherein:

[0063] The unsaturated aldehyde production device comprises a fixed bed multi-tube type reactor having a plurality of reaction tubes and a reaction bath for adjusting the temperature of the plurality of reaction tubes.

[0064] In the reaction tube, two or more catalyst layers are arranged in the gas flow direction.

[0065] When the reaction bath temperature when the yield of unsaturated aldehyde is the highest is A (°C), and the reaction bath temperatures when the yield is 1.0 percentage point lower than the highest value are A1 (°C) and A2 (°C), the following equations (1) and (2) hold.

[0066] A1<A<A2 (1)

[0067] (A2-A1)≥10 (2)

[0068] 11) A method for producing an unsaturated aldehyde, which is a method for producing the corresponding unsaturated aldehyde by partially oxidizing an olefin using a fixed bed multi-tubular reactor, wherein:

[0069] The fixed bed multi-tube reactor comprises a plurality of reaction tubes and a reaction bath for adjusting the temperature of the plurality of reaction tubes.

[0070] In the reaction tube, two or more catalyst layers are arranged in the gas flow direction.

[0071] The following formula (3) holds true for Sf and St when the unsaturated aldehyde is produced at the reaction bath temperature A (° C.) at which the yield of the unsaturated aldehyde is the highest.

[0072] (Sf / St)×100≤42.0 (3)

[0073] Here, Sf and St are determined by the following operation steps (a) to (c).

[0074] (a) disposing p (p is an integer greater than or equal to 2) thermocouples at equal intervals in the entire gas flow direction of the two or more catalyst layers provided in the reaction tube, and using the thermocouples to obtain the field point temperatures T1 at p measurement points in the reaction tube when producing unsaturated aldehyde at a reaction bath temperature A (° C.) j (℃)(j is 1~p).

[0075] (b) For each of the measurement points, calculate the field point temperature T1 j The value obtained by subtracting the reaction bath temperature A (°C) from the reaction bath temperature (T1 j-A) field point exothermic temperature T2 j Among them, in T1 j -A is a negative value, the field heat release temperature T2 of the measurement point j Set to 0.

[0076] (c) lowering the field exothermic temperature T2 of all the measuring points in the reaction tube j The total value of is set as St. The field point heat release temperature T2 of the measurement point set at the catalyst layer closest to the outlet side is set as k The total value (k is 1 to q, q is the number of measurement points provided in the catalyst layer closest to the outlet side, q<p) is referred to as Sf.

[0077] Effects of the Invention

[0078] According to the present invention, when an olefin or an alcohol capable of generating an olefin by intramolecular dehydration reaction thereof is used as a raw material to produce a corresponding unsaturated aldehyde, a high yield can be maintained safely and stably for a long period of time even in an industrial facility. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Figure 1 This is a schematic diagram showing an example of an apparatus for producing an unsaturated aldehyde. DETAILED DESCRIPTION

[0080] Figure 1 FIG. 2 is a schematic diagram showing an apparatus 1 for producing an unsaturated aldehyde. Figure 1 As shown, the manufacturing apparatus 1 includes a fixed bed multi-tubular reactor having a plurality of reaction tubes 20 and a reaction bath 30. Catalyst layers 21, 22, and 23 are provided inside the reaction tube 20, and different catalysts are arranged in each catalyst layer. In addition, the temperature of the reaction tube 20 can be adjusted by the reaction bath 30. According to the manufacturing apparatus 1, for example, a reaction raw material gas containing olefin is introduced from the upper part of the manufacturing apparatus 1, and the raw material gas is passed through the reaction tube 20 to react, thereby obtaining a reaction product containing an unsaturated aldehyde.

[0081] [Relationship between A, A1, and A2]

[0082] The present invention relates to a method and apparatus for producing an unsaturated aldehyde, and its essence relates to a method for filling a catalyst layer. That is, when the reaction bath temperature when the yield of the unsaturated aldehyde reaches the highest value is set to A (°C), and the reaction bath temperature when the yield is 1.0 percentage points lower than the highest value is set to A1 (°C) and A2 (°C), the catalyst is filled in such a way that the above formulas (1) and (2) are established. The yield here means the molar yield. It should be noted that in this specification, A, A1, and A2 are defined as follows.

[0083] A: The reaction bath temperature at which the yield of unsaturated aldehydes reaches the highest

[0084] A1, A2: Reaction bath temperature at which the yield of unsaturated aldehyde is 1.0 percentage point lower than that at reaction bath temperature A

[0085] Moreover, A is higher than A1, A2 is higher than A, and (A2-A1) is above 10°C. (A2-A1) is more preferably above 10°C and below 30°C, further preferably above 10°C and below 25°C, and most preferably above 10°C and below 20°C. Here, (A2-A1) is the reaction bath temperature region (operating window) in which the acrolein yield is stable. The larger (A2-A1), the more unsaturated aldehyde can be obtained in a high yield within a wide reaction bath temperature range, so it is preferred. In addition, the maximum value of the yield (yield at reaction bath temperature A) is, for example, above 50%, preferably above 70%. It should be noted that A1 and A2 do not need to be calculated based on the relationship between the measured acrolein yield and BT, and can be calculated by interpolation or extrapolation of a series of data for measuring the acrolein yield by changing BT. The reason why the yield of acrolein decreases at a reaction bath temperature lower than A (°C) is due to the decrease in the reaction rate of raw material propylene, and the reason why the yield of acrolein decreases at a reaction bath temperature higher than A (°C) is due to the generation of carbon dioxide, acrylic acid, etc. represented by the stepwise oxidation reaction of acrolein. In the case where the target product is acrylic acid, the catalyst of the present invention is used in the first step of a two-step oxidation reaction (propylene → acrolein → acrylic acid), at which time the total amount of acrolein and acrylic acid becomes important, so even if the reaction bath temperature becomes high, the yield of acrylic acid does not decrease sharply. Therefore, in the case where the target product is acrylic acid, the reaction bath temperature region in which the yield is stable tends to become relatively wide. On the contrary, in the case where the target product is acrolein, the operating window tends to become relatively narrow, so it is difficult to control appropriately, and it can be said that its control method is not well known to those skilled in the art as described above.

[0086] When the catalyst is filled in a manner that satisfies formula (1) and formula (2), the hot spot temperature (PTf, unit: ° C) of the most active outlet catalyst can change smoothly relative to the reaction bath temperature (BT, unit: ° C) (= ΔPTf / ΔBT low), which can achieve higher yield, safe and stable equipment operation. In addition, by suppressing runaway reactions, thermal stress on the catalyst can be prevented, and a longer service life can be expected. In more detail, due to slight changes in the reaction bath temperature and differences in the reaction bath temperatures between multiple reaction tubes, the hot spot on the most active outlet catalyst changes sharply, thereby preventing thermal runaway and the damage and explosion of the reaction tubes associated therewith. In addition, since the heat release on the outlet side of the reactor is large, the gas temperature at the reactor outlet is high, which can suppress the reduction in acrolein yield caused by the cold flame reaction (cold flame) of acrolein, the accumulation of carbonaceous precipitates on the outlet side of the reaction tube caused by the self-oxidation reaction of acrolein (coking or fouling), and the resulting blockage in the reaction tube and catalyst degradation.

[0087] [Relationship between Sf and St]

[0088] The present invention preferably provides two or more catalyst layers in the gas flow direction of the reaction tube, and the Sf and St of the field exothermic temperature satisfy the above formula (3). Here, Sf and St are values ​​determined by the following operation steps (a) to (c).

[0089] (a) arranging p (p is an integer greater than or equal to 2) thermocouples at equal intervals in the gas flow direction of the two or more catalyst layers provided in the reaction tube, and obtaining the field point temperatures T1 at the p measurement points in the reaction tube when producing the unsaturated aldehyde at the reaction bath temperature A (° C.) using the thermocouples; i (℃)(i is 1~p).

[0090] (b) For each measurement point, calculate the field point temperature T1 i The value obtained by subtracting the reaction bath temperature A (°C) from the reaction bath temperature (T1 i -A) field point exothermic temperature T2 i Among them, in T1 i -A is a negative value, the field heat release temperature T2 of the measurement point i Set to 0.

[0091] (c) The field exothermic temperature T2 of all the measuring points in the reaction tube is i The total value of is set as St. The field point heat release temperature T2 of the measurement point set at the catalyst layer closest to the outlet side is set as j (j is 1 to q, q is the number of measurement points provided in the catalyst layer closest to the outlet side, q<p) and the total value is defined as Sf. That is, St and Sf are defined by equation (5) and equation (6), respectively.

[0092]

[0093] In a reactor where the thickness of the partition wall is constant from the entrance to the exit of the reaction tube like a multi-tubular reactor, according to Fourier's law of heat conduction, Sf represents the sum of the heat release of the catalyst layer closest to the exit side, and St represents the sum of the heat release of all catalyst layers. That is, the relationship that Sf and St satisfy formula (3) indicates that the heat release of the catalyst layer closest to the exit side is less than 42.0% of the heat release of all catalyst layers, and the raw gas reacts reliably before reaching the catalyst layer closest to the exit side with high activity. For those skilled in the art, it is well known that the reaction rate of generating unsaturated aldehydes from olefins by partial oxidation is one level relative to the olefin partial pressure. That is, the closer to the lower layer side of the reactor, the lower the reaction rate and (the influence of the catalyst shape and the dilution rate using the inert carrier are considered in addition to the reaction rate) reactivity, so in the case of multi-layer filling in this reaction, a highly active catalyst is usually selected closest to the exit side. However, in the design of such a filling method, it can be said that it is not clear to those skilled in the art about how to react the olefins before the catalyst closest to the exit side, and how to set the activity of the catalyst closest to the exit side to obtain the effect of the present invention. It should be noted that, as a more preferred range of Sf / St×100, the lower limit is preferably 1, 5, 7, 9, 11, 12, 13, 14, 15, 16, 17, 18, and the upper limit is preferably 40, 37, 35, 33, 31, 30, 29, 28. That is, Sf / St×100 is preferably 1 or more and 40 or less, more preferably 5 or more and 40 or less, more preferably 7 or more and 40 or less, more preferably 11 or more and 40 or less, more preferably 12 or more and 37 or less, more preferably 13 or more and 35 or less, more preferably 14 or more and 33 or less, more preferably 15 or more and 31 or less, more preferably 16 or more and 30 or less, more preferably 17 or more and 29 or less, and most preferably 18 or more and 28 or less.

[0094] <Measurement of temperature distribution in the reaction tube>

[0095] In the reaction tube, a thermocouple is inserted at a predetermined interval in the depth direction to obtain the temperature information of the catalyst layer filled with the catalyst and / or the inert layer filled with the inert carrier. The insertion method of the thermocouple is not limited as long as it is a method known to those skilled in the art, and for example, the following methods can be cited. The direction of inserting the thermocouple is the depth direction of the reaction tube and / or a direction perpendicular to the depth direction of the reaction tube, the insertion method of the thermocouple is a method of directly inserting the thermocouple in parallel with the reaction tube and / or inserting a shell (thermocouple sleeve) for inserting the thermocouple and inserting the thermocouple therein (that is, the reaction tube is a double tube structure), and the method of moving the thermocouple over time is a fixed type that does not move at all and / or a type that moves to any position in the reaction tube over time.

[0096] It should be noted that the reaction tubes into which the thermocouples are inserted are not all the reaction tubes in the reactor, but a part of the reaction tubes. Among the thousands to tens of thousands of reaction tubes, 5 or more and 100 or less, preferably 6 or more and 50 or less, more preferably 7 or more and 40 or less, and particularly preferably 8 or more and 16 or less reaction tubes are usually selected as the object. In addition, in a multi-tubular reactor, for a plurality of partitions divided on a plane perpendicular to the flow direction of the gas, the reaction tubes into which the thermocouples are inserted can be selected only from a part of the partitions, or can be selected from all the partitions as completely as possible. However, in order to grasp the temperature of the entire reactor, it is preferred to select at least one reaction tube from more than 40% of the partitions in all the partitions, more preferably from more than 60% of the partitions, and more preferably from more than 75% of the partitions. It should be noted that in the present invention, unless otherwise specified, the reaction tubes into which the thermocouples are inserted are also referred to as reaction tubes.

[0097] In addition, there is no particular restriction on the position of the thermocouple in the depth direction, and the method of equidistantly arranging the thermocouple or the method of changing the interval of the thermocouple as needed can be adopted. In the case of equidistantly arranging the thermocouple, in order to accurately obtain Sf and St, it is preferred to obtain temperature measurement data at intervals below 10 cm. In the case of changing the interval of the thermocouple, particularly in an exothermic reaction such as the reaction of the present invention, since the temperature distribution in the catalyst-filled layer on the gas inlet side presents a sharp rise in the depth direction, it is preferred to configure the method in a manner that the interval of the thermocouple position in the catalyst-filled layer on the gas inlet side narrows, on the contrary, the interval of the thermocouple position in the catalyst-filled layer on the gas outlet side widens. In addition, compared with measuring temperature information at the position of all selected multiple reaction tubes in the same depth direction, it is preferred to more easily grasp the temperature distribution of the reactor as a whole when the measurement position is staggered in the depth direction in each reaction tube.

[0098] As described above, by setting the partitions, number of thermocouples, and depth of measurement points of the reaction tube into which the thermocouples are inserted, the temperature distribution in the reaction tube can be obtained with an efficient and small number of thermocouples.

[0099] [About Catalyst]

[0100] The catalyst used in the present invention is preferably a catalyst having a composition represented by the following formula (I).

[0101] Mo a Bi b Ni c Co d Fe e X f Y g Z h O i (I)

[0102] In the above formula (I), Mo, Bi, Ni, Co and Fe represent molybdenum, bismuth, nickel, cobalt and iron, respectively, X represents at least one element selected from tungsten, antimony, tin, zinc, chromium, manganese, magnesium, silicon, aluminum, cerium and titanium, Y represents at least one element selected from sodium, potassium, cesium, rubidium and thallium, Z represents at least one element belonging to Group 1 to Group 16 of the periodic table and selected from elements other than the above Mo, Bi, Ni, Co, Fe, X, Y and O, a, b, c, d, e, f, g, h and i represent the atomic numbers of molybdenum, bismuth, nickel, cobalt, iron, X, Y, Z and oxygen, respectively, and when a=12, 0<b≤7.0, 0≤c≤10, 0<d≤10, 0<c+d≤20, 0<e≤5.0, 0≤f≤2.0, 0≤g≤3.0, 0≤h≤5.0 are satisfied, and i is a value determined by the oxidation state of each element.

[0103] In the above formula (1), when a=12, the preferred ranges of b to h are as follows.

[0104] The lower limit of b is preferably 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, and 0.70, and the upper limit is preferably 6.0, 5.0, 4.0, 3.0, 2.0, 1.8, 1.5, 1.2, and 1.0. That is, b is preferably 0.10 to 6.0, more preferably 0.10 to 5.0, more preferably 0.10 to 4.0, more preferably 0.20 to 3.0, more preferably 0.30 to 2.0, more preferably 0.40 to 1.8, more preferably 0.50 to 1.5, more preferably 0.60 to 1.2, and most preferably 0.70 to 1.0.

[0105] The lower limit of c is preferably 0.20, 0.50, 0.80, 1.0, 1.5, 1.8, 2.0, 2.5, and 2.8, and the upper limit is preferably 8.0, 7.0, 6.0, 5.0, 4.0, 3.5, and 3.3. That is, c is preferably 0.20 to 8.0, more preferably 0.50 to 8.0, more preferably 0.80 to 8.0, more preferably 1.0 to 7.0, more preferably 1.5 to 6.0, more preferably 1.8 to 5.0, more preferably 2.0 to 4.0, more preferably 2.5 to 3.5, and most preferably 2.8 to 3.3.

[0106] The lower limit of d is preferably 1.0, 2.0, 3.0, 4.0, and 5.0, and the upper limit is preferably 9.5, 9.0, 8.5, 8.0, 7.5, 7.0, 6.5, and 6.3. That is, d is preferably 1.0 to 9.5, more preferably 1.0 to 9.0, more preferably 1.0 to 8.5, more preferably 1.0 to 8.0, more preferably 2.0 to 7.5, more preferably 3.0 to 7.0, more preferably 4.0 to 6.3, and most preferably 5.0 to 6.3.

[0107] The lower limit of c+d is preferably 0.0, 2.0, 4.0, 6.0, 8.0, and 8.3, and the upper limit is preferably 20.0, 15.0, 12.5, 11.0, 10.0, and 9.0. That is, c+d is preferably 0.0 to 20.0, more preferably 2.0 to 15.0, more preferably 4.0 to 12.5, more preferably 6.0 to 11.0, more preferably 8.0 to 10.0, and most preferably 8.3 to 9.0.

[0108] The lower limit of e is preferably 0.10, 0.20, 0.50, 0.80, 1.0, 1.5, and 1.6, and the upper limit is preferably 4.5, 4.0, 3.5, 3.0, 2.5, 2.0, and 1.9. That is, e is preferably 0.10 to 4.5, more preferably 0.20 to 4.0, more preferably 0.50 to 3.5, more preferably 0.80 to 3.0, more preferably 1.0 to 2.5, more preferably 1.5 to 2.0, and most preferably 1.6 to 1.9.

[0109] The upper limit of f is preferably 1.8, 1.5, 1.0, 0.80, and 0.50, and the lower limit is preferably 0. That is, f is preferably 0 to 1.8, more preferably 0 to 1.5, more preferably 0 to 1.0, more preferably 0 to 0.80, more preferably 0 to 0.50, and most preferably 0.

[0110] The lower limit of g is preferably 0.010, 0.020, 0.030, 0.040, 0.050, and 0.060, and the upper limit is preferably 2.0, 1.0, 0.50, 0.40, 0.30, 0.20, 0.15, and 0.090. That is, g is preferably 0.010 to 2.0, more preferably 0.010 to 1.0, more preferably 0.010 to 0.50, more preferably 0.020 to 0.40, more preferably 0.030 to 0.30, more preferably 0.040 to 0.20, more preferably 0.050 to 0.15, and most preferably 0.060 to 0.090.

[0111] The upper limit of h is preferably 4.0, 3.0, 2.0, 1.8, 1.5, 1.0, 0.80, and 0.50, and the lower limit is preferably 0. That is, h is more preferably 0 to 4.0, more preferably 0 to 3.0, more preferably 0 to 2.0, more preferably 0 to 1.8, more preferably 0 to 1.5, more preferably 0 to 1.0, more preferably 0 to 0.80, more preferably 0 to 0.50, and most preferably 0.

[0112] X in the formula (1) is preferably tungsten, antimony, zinc, magnesium, or cerium, and particularly preferably antimony or zinc.

[0113] Y in the formula (1) is preferably sodium, potassium, or cesium, and more preferably potassium or cesium.

[0114] As Z in the formula (1), vanadium, copper, niobium, zirconium, calcium, beryllium, strontium, barium, lead or phosphorus is preferred.

[0115] [First Layer Catalyst]

[0116] In the present invention, the catalytic active component of the catalyst contained in the first layer (the catalyst layer closest to the inlet side of the reaction raw material gas) preferably has a composition represented by the following formula (I-1). It should be noted that, when three or more catalyst layers are provided, it is preferred that all catalyst layers except the catalyst layer closest to the outlet side contain a catalyst having a composition represented by formula (I-1).

[0117] Mo a1 Bi b1 Ni c1 Co d1 Fe e1 X f1 Cs g1 Z h1 O i1 (I-1)

[0118] In formula (I-1), Mo, Bi, Ni, Co, Fe, Cs and O represent molybdenum, bismuth, nickel, cobalt, iron, cesium and oxygen respectively, X represents at least one element selected from tungsten, antimony, tin, zinc, chromium, manganese, magnesium, silicon, aluminum, cerium and titanium, Z represents at least one element belonging to Group 1 to Group 16 of the periodic table and selected from elements other than the above-mentioned Mo, Bi, Ni, Co, Fe, Cs, O and X, a1, b1, c1, d1, e1, f1, g1, h1 and i1 represent the atomic numbers of molybdenum, bismuth, nickel, cobalt, iron, X, Cs, Z and oxygen respectively, when a1=12, 0<b1≤7.0, 0≤c1≤10, 0<d1≤10, 0<e1≤5.0, 0≤f1≤2.0, 0<g1≤3.0, 0≤h1≤5.0 are satisfied, and i1 is a value determined by the oxidation state of each element.

[0119] When a1=12 in formula (I-1), preferred b1 to f1, h1, X and Z are the same as b to f, h, X and Z in formula (I) including preferred embodiments.

[0120] Regarding g1, the lower limit is preferably 0.0010, 0.0050, 0.010, 0.015, 0.020, and 0.030, and the upper limit is preferably 2.0, 1.0, 0.50, 0.40, 0.30, 0.20, 0.15, 0.090, and 0.060. That is, g1 is preferably greater than or equal to 0.0010 and less than or equal to 2.0, more preferably greater than or equal to 0.0010 and less than or equal to 1.0, more preferably greater than or equal to 0.0010 and less than or equal to 0.50, more preferably greater than or equal to 0.0010 and less than or equal to 0.40, more preferably greater than or equal to 0.0050 and less than or equal to 0.30, more preferably greater than or equal to 0.010 and less than or equal to 0.20, more preferably greater than or equal to 0.015 and less than or equal to 0.15, more preferably greater than or equal to 0.020 and less than or equal to 0.090, and most preferably greater than or equal to 0.030 and less than or equal to 0.060.

[0121] [Catalyst closest to the outlet side]

[0122] In the present invention, the catalytic active component of the catalyst contained in the catalyst layer closest to the outlet side preferably has a composition represented by the following formula (I-2). For example, in the case of providing three catalyst layers, the catalytic active component contained in the third catalyst layer preferably has a composition represented by formula (I-2), and in the case of more layers of filling, the catalytic active component contained in the catalyst layer closest to the outlet side also preferably has a composition represented by formula (I-2).

[0123] Mo a2 Bi b2 Ni c2 Co d2 Fe e2 X f2 K g2 Z h2 O i2 (I-2)

[0124] In formula (I-2), Mo, Bi, Ni, Co, Fe, K and O represent molybdenum, bismuth, nickel, cobalt, iron, potassium and oxygen respectively, X represents at least one element selected from tungsten, antimony, tin, zinc, chromium, manganese, magnesium, silicon, aluminum, cerium and titanium, Z represents at least one element belonging to Group 1 to Group 16 of the periodic table and selected from elements other than the above-mentioned Mo, Bi, Ni, Co, Fe, K, O and X, a2, b2, c2, d2, e2, f2, g2, h2 and i2 represent the number of atoms of molybdenum, bismuth, nickel, cobalt, iron, X, K, Z and oxygen respectively, when a2=12, 0<b2≤7.0, 0≤c2≤10, 0<d2≤10, 0<e2≤5.0, 0≤f2≤2.0, 0≤g2≤3.0, 0≤h2≤5.0 are satisfied, and i2 is a value determined by the oxidation state of each element.

[0125] When a2=12 in formula (I-2), preferred b2 to f2, h2, X and Z are the same as b to f, h, X and Z in formula (I) including preferred embodiments.

[0126] Regarding g2, the lower limit is preferably 0.0010, 0.0050, 0.010, 0.015, 0.020, and 0.030, and the upper limit is preferably 2.0, 1.0, 0.50, 0.40, 0.30, 0.20, 0.15, and 0.10. That is, g2 is preferably 0.0010 or more and 2.0 or less, more preferably 0.0010 or more and 1.0 or less, more preferably 0.0010 or more and 0.50 or less, more preferably 0.0050 or more and 0.40 or less, more preferably 0.010 or more and 0.30 or less, more preferably 0.015 or more and 0.20 or less, more preferably 0.020 or more and 0.15 or less, and most preferably 0.030 or more and 0.10 or less.

[0127] [Filling method]

[0128] As methods for adjusting the relationship between A, A1, and A2, and adjusting the relationship between St and Sf, various methods may be considered, such as (1) a method for controlling the relative activity of each catalyst layer, (2) a method for controlling the particle size of each catalyst layer, (3) a method for providing an inactive material layer on the outlet side of the reaction tube, and (4) a method for setting a high gas temperature on the inlet side of the catalyst layer of the reaction tube. These methods may be used alone or in combination.

[0129] In the method (1) of controlling the relative activity of each catalyst layer, the catalyst is filled into a differential system reactor, and the reaction rate is calculated from the raw gas conversion rate x obtained under a specific BT according to an integral type reaction rate formula. For example, in the oxidation reaction of propylene, since it is a first-order rate formula with respect to the propylene concentration, the reaction rate k of this reaction is calculated by the following formula (II).

[0130] k=-Ln(1-x / 100) (II)

[0131] Here, k is the reaction rate of this reaction (unitless), Ln is the natural logarithm, and x is the propylene conversion rate (unit: %).

[0132] Next, the reaction rate of each catalyst layer is calculated under the same conditions using this method, and then the substantial reaction rate ak of each catalyst layer in the device is calculated using the following formula (III).

[0133] ak = (dilution rate of the catalyst layer) × (filling length of the catalyst layer) × (reaction rate k of the catalyst in the catalyst layer) (III)

[0134] Here, the dilution rate has the same meaning as the dilution rate using inactive substances described later, and the filling length is the length of the filled catalyst layer expressed in units of cm. It should be noted that the filling length preferably uses the measured value rather than the designed value. In the equipment, since there are multiple reaction tubes in most cases, the average value obtained based on the measurement results of a part of them can also be used. For example, the catalyst can be filled in sequence from the upper part to the lower part of the reaction tube, and the spatial length of the upper part of each layer can be measured using a tape measure or the like to calculate.

[0135] From the ak of each layer thus calculated, akt / akn is calculated by the following formula (IV). The preferred numerical range of akt / akn is as follows: the lower limit is preferably 1.41, 1.42, 1.43, 1.44, 1.45, and the upper limit is preferably 10.00, 7.50, 5.00, 4.00, 3.00, 2.75, 2.65, 2.55, 2.50. That is, akt / akn is preferably greater than 1.41 and less than 10.00, more preferably greater than 1.41 and less than 7.50, more preferably greater than 1.41 and less than 5.00, more preferably greater than 1.41 and less than 4.00, more preferably greater than 1.41 and less than 3.00, more preferably greater than 1.42 and less than 2.75, more preferably greater than 1.42 and less than 2.65, more preferably greater than 1.42 and less than 2.55, and most preferably greater than 1.45 and less than 2.50.

[0136] akt / akn = (value obtained by adding up the substantial reaction rates ak of all catalyst layers) ÷ (substantial reaction rate ak of the catalyst layer closest to the outlet side of the reaction tube) (IV)

[0137] It should be noted that the above-mentioned raw gas conversion rate x is calculated by the following method in the present invention. A reaction tube with an inner diameter of 28.4 mm is filled with 4 g of catalyst in a state where the catalyst is diluted with an inactive substance so as not to generate hot spots, and the molar ratio of propylene: oxygen: nitrogen: water = 1: 1.7: 6.4: 3.0 and the space velocity (GHSV) of propylene = 400 h -1 The reaction was carried out at a reaction bath temperature of 360° C. The propylene flow rate at the outlet was calculated by calibrated gas chromatography, and the propylene conversion rate x was calculated by the following formula.

[0138] x = 100 - outlet propylene gas flow rate ÷ inlet propylene gas flow rate × 100

[0139] In the method of (2) controlling the particle size of each catalyst layer, the catalyst particle size of the catalyst layer closest to the outlet side of the reaction tube can be different from the catalyst particle size of other catalyst layers, and can be larger or smaller than the catalyst particle size of other catalyst layers. When the particle size of the catalyst on the outlet side of the reaction tube is large, the retention of gas on the outlet side is reduced, resulting in an increase in the yield of the target product, and as a secondary effect, the operation window can be adjusted to be wide. In addition, when the particle size of the catalyst on the outlet side of the reaction tube is small, the pressure and reaction rate on the inlet side increase, and the reaction is reliably carried out on the inlet side, so the operation window can be adjusted to be wide. These effects are different depending on the pressure setting in the reaction tube, the reaction bath temperature, the inner diameter of the reaction tube, the inlet gas molar ratio and the propylene concentration, so the particle size of each catalyst layer should be appropriately controlled according to each condition. For example, when the pressure in the reaction tube is high and / or the reaction bath temperature is low and / or the inner diameter of the reaction tube is large and / or the inlet propylene concentration is high, it is preferred to increase the particle size of each catalyst layer, and it is particularly preferred to increase the particle size of the catalyst layer on the inlet side of the reaction tube. In addition, as the preferred range of its particle size ratio (catalyst particle size of the catalyst layer closest to the outlet side of the reaction tube ÷ catalyst particle size of other catalyst layers), the lower limit is 0.50, 0.60, 0.70, 0.80, 0.90, 1.00 in the preferred order, and the upper limit is 1.50, 1.40, 1.30, 1.20, 1.10 in the preferred order. That is, the particle size ratio is preferably 0.50 or more and 1.50 or less, more preferably 0.60 or more and 1.50 or less, more preferably 0.70 or more and 1.40 or less, more preferably 0.80 or more and 1.30 or less, more preferably 0.90 or more and 1.20 or less, and most preferably 1.00 or more and 1.10 or less. In the case of setting more than three catalyst layers, the weighted average of the catalyst particle sizes obtained by weighting the filling lengths of each catalyst layer except the catalyst layer closest to the outlet side is used as the "catalyst particle size of other catalyst layers".

[0140] In the method (3) of providing an inactive material layer on the outlet side of the reaction tube, by providing the inactive material layer at a position closer to the outlet side than the catalyst layer, the pressure on the inlet side of the reaction tube is increased, and the reaction can be reliably carried out on the inlet side of the reaction tube. The filling length of the inactive material on the outlet side varies depending on the raw material load and the diameter of the reaction tube, and is, for example, 5 cm or more, preferably 10 cm or more, more preferably 20 cm or more, and most preferably 30 cm or more. The filling length of the inactive material on the outlet side can be, for example, 50 cm or less.

[0141] In the method (4) of setting the gas temperature at the inlet side of the reaction tube to be high, by increasing the inlet gas temperature, the catalyst at the inlet side of the reaction tube is easily activated, and the reaction can be reliably carried out. The inlet gas temperature is preferably 150°C or higher, 200°C or higher, 250°C or higher, 270°C or higher, 290°C or higher, 300°C or higher, 310°C or higher, 320°C or higher, 330°C or higher, and 340°C or higher. The inlet gas temperature may be, for example, 360°C or lower.

[0142] [Regarding the filling length of the catalyst layer]

[0143] The method of adjusting the filling length of the catalyst layer in (1) among the above methods will be described in detail based on the following definition of the filling length of the catalyst layer.

[0144] Ln: When n catalyst layers are arranged in the gas flow direction of the reaction tube, the filling length of the nth layer from the gas inlet side of the reaction tube

[0145] L: Total filling length from the first layer to the n-1th layer from the gas inlet side of the reaction tube

[0146] The case where L / Ln is 1.5 or more and 3.5 or less is a preferred filling method. In addition, it is more preferred that the catalyst layer has the above-mentioned catalyst composition. The further preferred upper limit of this L / Ln is 3.4, 3.3, 3.2, 3.1, and particularly preferably 3.0. In addition, the preferred lower limit is 1.6, 1.7, 1.8, 1.9, and particularly preferably 2.0. Therefore, L / Ln is preferably 1.6 or more and 3.4 or less, more preferably 1.7 or more and 3.3 or less, more preferably 1.8 or more and 3.2 or less, more preferably 1.9 or more and 3.1 or less, and most preferably 2.0 or more and 3.0 or less.

[0147] The number n of divisions of the catalyst layer is preferably two to five layers, more preferably two to four layers, particularly preferably two to three layers, and most preferably three layers.

[0148] The shape of the catalyst contained in the catalyst layer used in the present invention is not particularly limited, and spherical, cylindrical, doughnut-shaped, powdery, etc. can be used, but a spherical shape is particularly preferred.

[0149] When two layers are filled, both the catalyst contained in the upper layer and the catalyst contained in the lower layer may be diluted with an inactive substance, but a method in which neither the catalyst contained in the upper layer nor the catalyst contained in the lower layer is diluted is more preferred.

[0150] As the dilution rate using inactive substances, the preferred range is described below. The dilution rate mentioned here is a numerical value representing the mass ratio of the catalyst in the catalyst layer composed of the catalyst and the inactive substance, for example, the catalyst layer is 80 mass% dilution means that the catalyst is 80 mass% and the inactive substance is 20 mass%. It should be noted that, as described in the manufacturing method of the catalyst described later, when the catalyst active component is loaded on an inactive carrier to make a catalyst, the dilution rate is calculated based on the mass of the catalyst containing the inactive carrier. Below, taking the case of n=2 or 3 as an example, the preferred mode is described, but the present invention is not limited thereto.

[0151] As the method for filling the catalyst layer of the present invention, the following 1) and 2) are preferable.

[0152] 1) n=2, the upper layer is a catalyst containing a catalytically active component represented by formula (I-1), and the dilution rate is 100% by mass. The lower layer is a catalyst containing a catalytically active component represented by formula (I-2), and the dilution rate is 100% by mass.

[0153] 2) n=3, the middle layer is a catalyst containing a catalyst active component having a composition represented by formula (I-1), and the dilution rate is 100% by mass. The upper layer is a catalyst obtained by diluting the same catalyst as the middle layer with an inactive substance, and the dilution rate is greater than or equal to 60% by mass and less than 100% by mass. The lower layer is a catalyst containing a catalyst active component having a composition represented by formula (I-2), and the dilution rate is 100% by mass.

[0154] In addition, there is also a filling method in which an inactive material layer (inert layer) is provided at a position closer to the inlet side of the reaction tube than the catalyst layer, and this filling method may also be adopted as long as it does not hinder the effect of the present invention. However, in the present invention, it is preferred that there is no inert layer at a position closer to the inlet side of the reaction tube than the catalyst layer.

[0155] Examples of the inactive material include known materials such as silicon dioxide, aluminum oxide, titanium dioxide, zirconium oxide, niobium oxide, silicon dioxide-alumina, silicon carbide, carbide, and mixtures thereof. Among them, silicon dioxide, aluminum oxide, or mixtures thereof are preferred, silicon dioxide and aluminum oxide are particularly preferred, and a mixture of silicon dioxide and aluminum oxide is most preferred.

[0156] The shape of the inactive material is not particularly limited, but is preferably spherical. The average particle size of the inactive material is preferably 3 mm to 10 mm, more preferably 3.5 mm to 9 mm, and particularly preferably 4 mm to 8 mm.

[0157] [Regarding the method for producing the catalyst]

[0158] The catalyst used in the present invention can be produced, for example, through the following steps a) to e).

[0159] <Step a) Preparation>

[0160] Usually, the starting materials of each element constituting the active component of the catalyst are not particularly limited. As the raw material of the molybdenum component, molybdenum oxides such as molybdenum trioxide; molybdenum acids such as molybdic acid and ammonium molybdate or their salts; molybdenum-containing heteropoly acids such as phosphomolybdic acid and silicomolybdic acid or their salts can be used. It is preferred to use ammonium molybdate, which can obtain a high-performance catalyst. In particular, there are various compounds such as ammonium dimolybdate, ammonium tetramolybdate, and ammonium heptamolybdate in ammonium molybdate, among which ammonium heptamolybdate is most preferably used.

[0161] As the raw material of the bismuth component, bismuth salts such as bismuth nitrate, bismuth subcarbonate, bismuth sulfate, bismuth acetate, etc. can be used; bismuth trioxide, metallic bismuth, etc. Bismuth nitrate is preferred. When using this bismuth nitrate, a high-performance catalyst can be obtained. As raw materials for iron, cobalt, nickel and other elements, oxides or nitrates, carbonates, organic acid salts, hydroxides, etc. that can be converted into oxides by strong heat, or mixtures thereof can usually be used. For example, the iron component raw material and the cobalt component raw material and / or the nickel component raw material are dissolved in water at a desired ratio under the conditions of 10°C to 80°C and mixed, and mixed with the molybdenum component raw material and the Z component raw material aqueous solution or slurry separately prepared under the conditions of 20°C to 90°C, heated and stirred for about 1 hour under the conditions of 20°C to 90°C, and then the aqueous solution in which the bismuth component raw material is dissolved and the X component raw material and the Y component raw material as required are added to obtain an aqueous solution or slurry containing the catalyst component. Hereinafter, the aqueous solution or slurry obtained in this way is collectively referred to as the preparation solution (A).

[0162] Here, the preparation liquid (A) does not necessarily need to contain all the constituent elements of the catalyst active components, and a part of the elements or a part of the amount thereof may be added in a subsequent step. In addition, when preparing the preparation liquid (A), when the amount of water for dissolving the raw materials of each component, or the acid concentration in the aqueous solution sufficient to dissolve the raw materials when adding acids such as sulfuric acid, nitric acid, hydrochloric acid, tartaric acid, acetic acid, etc. for dissolution is not suitable for preparation in a range of, for example, 5% to 99% by mass, the form of the preparation liquid (A) sometimes becomes a clay-like mass. In this case, an excellent catalyst cannot be obtained. As the form of the preparation liquid (A), an aqueous solution or a slurry is preferred because an excellent catalyst can be obtained.

[0163] <Step b) Drying>

[0164] Next, the prepared liquid (A) obtained above is dried to prepare a dry powder. There is no particular limitation on the drying method as long as it is a method that can completely dry the prepared liquid (A), and examples thereof include drum drying, freeze drying, spray drying, evaporative drying, and the like. Among them, in the present invention, spray drying that can dry a slurry into a powder or granules in a short time is particularly preferred. The drying temperature of the spray drying varies depending on the concentration of the slurry, the liquid conveying speed, and the like, and the temperature at the outlet of the dryer is about 70°C to about 150°C. In addition, it is preferred to dry in such a manner that the average particle size of the dry powder obtained at this time is 10 μm to 700 μm. In this manner, a dry powder (B) is obtained.

[0165] <Step c) Pre-calcination>

[0166] By calcining the obtained dry powder (B) at 200°C to 600°C, preferably at 300°C to 600°C, under air circulation, the moldability, mechanical strength and catalyst performance of the catalyst tend to be improved. The calcination time is preferably 1 hour to 12 hours. In this way, a pre-calcined powder (C) is obtained.

[0167] <Process d) Molding>

[0168] There is no particular limitation on the molding method. When molding into a cylindrical or annular shape, it is preferred to use a tablet molding machine, an extrusion molding machine, or the like. In the case of further preferred molding into a spherical shape, the pre-calcined powder (C) can be molded into a spherical shape using a molding machine, but it is preferred to load the pre-calcined powder (C) (including a molding aid and a strength enhancer as required) on an inactive ceramic or other carrier. Here, as a loading method, there are widely known methods such as a rotary granulation method, a method using a centrifugal flow coating device, and a wash coating method. As long as the method can uniformly load the pre-calcined powder (C) on the carrier, there is no particular limitation. However, in consideration of the manufacturing efficiency of the catalyst and the performance of the prepared catalyst, the following method is more preferred: in a device having a flat or concave-convex disk at the bottom of a fixed cylindrical container, the disk is rotated at a high speed, thereby utilizing the repeated rotation and revolution of the carrier itself to vigorously stir the carrier filled in the container, and the pre-calcined powder (C) and the molding aid and / or strength enhancer as required are added thereto, thereby loading the powder component on the carrier. In this way, a molded body (D) is obtained.

[0169] It should be noted that, when loading, it is preferred to use a binder. As specific examples of binders that can be used, water, ethanol, methanol, propanol, polyols, polyvinyl alcohol as a polymer binder, silica sol aqueous solution as an inorganic binder, etc. can be cited, preferably ethanol, methanol, propanol, polyols, more preferably diols such as ethylene glycol, triols such as glycerol, etc. By using an appropriate amount of glycerol aqueous solution, the moldability becomes good, and a catalyst with high mechanical strength and high performance can be obtained. Specifically, when a glycerol aqueous solution with a concentration of 5% by mass or more is used, a particularly high-performance catalyst can be obtained. Relative to 100 parts by mass of the pre-calcined powder (C), the amount of these binders used is usually 2 parts by mass to 80 parts by mass. Regarding the inactive carrier, an inactive carrier with a diameter of about 2 mm to about 8 mm is usually used, and the pre-calcined powder (C) is loaded on the inactive carrier. Its loading rate is determined by considering the catalyst use conditions, such as the reaction conditions such as the space velocity of the reaction raw materials and the raw material concentration, and is usually 20% by mass to 80% by mass. Here, the load factor is defined by the following formula (4).

[0170] Loading rate (mass %) = 100 × [mass of the pre-calcined powder (C) used in molding / (mass of the pre-calcined powder (C) used in molding + mass of the inactive carrier used in molding)] (4)

[0171] <Step e) Main calcination>

[0172] By calcining the molded body (D) obtained by step d) at a temperature of 200°C to 600°C for about 1 hour to about 12 hours, there is a tendency for the catalyst activity and selectivity to be improved. The calcination temperature is preferably above 400°C and below 600°C, and more preferably above 500°C and below 600°C. As the circulating gas, air is convenient and therefore preferred. In addition, inert gases, gases for forming a reducing atmosphere, and mixtures thereof can also be used. Examples of inert gases include nitrogen and carbon dioxide. Examples of gases for forming a reducing atmosphere include: gases containing nitrogen oxides, gases containing ammonia, and hydrogen. In this way, a catalyst (E) is obtained.

[0173] [Olefin concentration in raw material]

[0174] The gas-phase catalytic oxidation reaction of olefins of the present invention is carried out as follows: a mixed gas of 6% to 12% by volume of olefins (more preferably 6% to 10% by volume), 5% to 18% by volume of molecular oxygen, 0% to 60% by volume of water vapor and 20% to 70% by volume of an inert gas such as nitrogen, carbon dioxide, etc., in a raw material gas composition, is introduced onto the catalyst prepared as described above at a temperature range of 250° C. to 450° C. and a pressure of normal pressure to 10 atmospheres, preferably at normal pressure to 5 atmospheres, and more preferably at normal pressure to 3 atmospheres, for a contact time of 0.5 seconds to 10 seconds.

[0175] In addition, it is preferred that the volume ratio of oxygen to olefin in the raw material gas (oxygen / olefin) is 1.0 or more and 1.8 or less. The more preferred upper limits of oxygen / olefin are 1.7, 1.6, and more preferably 1.5. In addition, the more preferred lower limits are 1.1, 1.2, and 1.3, respectively. As can be seen from the above, oxygen / olefin is more preferably 1.1 or more and 1.7 or less, more preferably 1.2 or more and 1.6 or less, and most preferably 1.3 or more and 1.5 or less.

[0176] It should be noted that, in the present invention, olefins also include alcohols such as tert-butyl alcohol that generate olefins in their intramolecular dehydration reactions. From the viewpoint of production efficiency, it is preferred that the space velocity of the reaction substrates such as olefins relative to the catalyst volume (reaction substrate supply rate (NL / hour) / catalyst filling space volume (L)) is higher, but when it is too high, the yield of the target product is sometimes reduced, or the life of the catalyst is shortened. Therefore, in fact, the space velocity of the reaction substrate relative to the catalyst volume is preferably 40 hours. -1 ~200 hours -1 , more preferably 60 hours -1 ~180 hours -1 Here, NL represents the volume of the reaction substrate under standard conditions. In addition, as the conversion rate of olefins, it is preferably around the conversion rate that can obtain a high acrolein yield, usually 90% to 99.9%, preferably 95% to 99.5%, and more preferably 96% to 99%.

[0177] When the catalyst layer on the reaction gas outlet side is too short, the overall activity of the catalyst layer decreases, and sometimes the reaction bath temperature required to obtain the target product in order to obtain the usual raw material conversion rate is excessively increased. When the reaction bath temperature is too high, the hot spot becomes high temperature, and the catalyst may deteriorate and the performance may decrease. In addition, depending on the situation, it is also possible that the high-activity catalyst layer on the gas outlet side will produce a high-temperature hot spot due to the early degradation of the catalyst on the gas inlet side, causing a sharp decrease in the selectivity and yield of the target product. Therefore, it is also necessary to consider the balance of the catalyst on the gas inlet side and the gas outlet side so that the catalyst layer on the outlet side is not too short, thereby reducing the overall activity of the catalyst layer and excessively increasing the reaction bath temperature. The reaction bath temperature is appropriately set according to the characteristics of the catalyst, the conditions of use, the necessary catalyst life, etc., so it cannot be generalized, but as the reaction bath temperature at the initial stage of the reaction, it is preferably 350°C or less, and more preferably 340°C or less. In addition, the lower limit is 300°C or more, and more preferably 310°C or more. That is, the reaction bath temperature at the initial stage of the reaction is preferably 300°C or more and 350°C or less, and more preferably 310°C or more and 340°C or less. It should be noted that the reaction bath temperature is a set temperature, which is set in order to obtain an appropriate raw material conversion rate.

[0178] In industrial equipment, by implementing the above-mentioned manufacturing method, the yield of unsaturated aldehyde can be improved and the runaway of the highly active gas outlet side can be suppressed. Thus, a high yield can be maintained for a long time and the industrial equipment can be operated stably. It can be considered that this effect is due to the fact that the occupancy rate of the catalyst layer with a relatively high selectivity exceeds the occupancy rate of the catalyst layer with a relatively high activity, thereby increasing the contribution of the high-selectivity catalyst to the reaction.

[0179] Example

[0180] Hereinafter, the present invention will be further described with reference to specific examples, but the present invention is not limited to these examples unless it departs from the gist of the present invention.

[0181] In addition, below, the definition of acrolein yield is as follows.

[0182] Acrolein yield (mol %)

[0183] =(number of moles of acrolein produced / number of moles of propylene supplied)×100

[0184] [Production Example (Preparation of Catalyst)]

[0185] (Catalyst A1)

[0186] While heating and stirring 3000 parts by mass of distilled water, 423.7 parts by mass of ammonium molybdate and 0.73 parts by mass of potassium nitrate were dissolved to obtain an aqueous solution (preparation solution 1). In addition, 378.4 parts by mass of cobalt nitrate, 139.6 parts by mass of nickel nitrate, and 161.6 parts by mass of iron nitrate were dissolved in 1000 parts by mass of distilled water to prepare an aqueous solution (preparation solution 2), and in addition, 97.1 parts by mass of bismuth nitrate were dissolved in 200 parts by mass of distilled water that was acidic by adding 81 parts by mass of concentrated nitric acid to prepare an aqueous solution (preparation solution 3). While vigorously stirring, preparation solution 2 and preparation solution 3 were sequentially mixed into the above-mentioned preparation solution 1 to generate a suspension, and the suspension was dried using a spray dryer and calcined at 440° C. for 6 hours to obtain a pre-calcined powder. The composition ratio of the catalyst active components other than oxygen at this time is Mo:Bi:Fe:Co:Ni:K=12:1.0:2.0:6.5:3.0:0.050 in atomic ratio. Then, the mass of the carrier used in the molding and the mass of the pre-calcined powder are adjusted so that the powder obtained by mixing 5 mass parts of crystalline cellulose with 100 mass parts of the pre-calcined powder is loaded on an inactive carrier (a spherical substance with a diameter of 4.5 mm with alumina and silica as the main components) at a loading rate defined by the above formula (4) of 50 mass%. Using a 20 mass% glycerol aqueous solution as a binder, the load is molded into a sphere with a diameter of 5.20 mm, thereby obtaining a loaded catalyst. The loaded catalyst was calcined at a calcination temperature of 530°C in an air atmosphere for 4 hours, thereby obtaining catalyst A1. The activity of catalyst A1 was evaluated as follows. 4 g of the catalyst was filled into a reaction tube with an inner diameter of 28.4 mm in a state of dilution with an inactive substance without heat storage, and the reaction mixture was heated to 400 hr at a molar ratio of propylene: oxygen: nitrogen: water = 1: 1.7: 6.4: 3.0 and a propylene hourly space velocity (GHSV) of 400 hr. -1 The reaction was carried out at a reaction bath temperature of 360° C. The propylene flow rate at the outlet was calculated by calibrated gas chromatography, and the propylene conversion rate x was calculated. Based on this, the reaction rate k of catalyst A1 calculated by the above formula (II) was 0.63.

[0187] (Catalyst B1)

[0188] In the production of catalyst A1, except that potassium nitrate as a raw material was changed to cesium nitrate, a pre-calcined powder with an atomic ratio of Mo:Bi:Fe:Co:Ni:Cs=12:1.0:2.0:6.5:3.0:0.030 was obtained by the same method. The subsequent steps were also carried out in the same manner as the production of catalyst A1, and catalyst B1 with a diameter of 5.20 mm was obtained. The reaction rate k of catalyst B1 was 0.35.

[0189] (Catalyst B2)

[0190] Catalyst B2 having a diameter of 5.00 mm was obtained by the same operation as catalyst B1, except that a spherical substance having a diameter of 4.0 mm and containing alumina and silica as main components was used as an inactive carrier and the pre-calcined powder obtained in the preparation of catalyst B1 was molded in such a manner that the loading rate was 60 mass %. The reaction rate k of catalyst B2 was 0.43.

[0191] (Catalyst C1)

[0192] In the manufacture of catalyst A1, the ratio of raw materials was changed to obtain a pre-calcined powder with an atomic ratio of Mo:Bi:Fe:Co:Ni:K=12:1.8:1.9:5.0:2.6:0.090. The pre-calcined powder was molded in a manner with a loading rate of 40 mass % using a spherical substance with a diameter of 4.4 mm and mainly composed of alumina and silica as an inactive carrier, and the operation was completely the same as catalyst A1 to obtain catalyst C1 with a diameter of 4.80 mm. The reaction rate k of catalyst C1 was 0.42.

[0193] (Catalyst D1)

[0194] In the preparation of catalyst A1, 60% by weight of nitric acid was added before adding the preparation solution 2 in the preparation step to adjust the pH of the preparation solution to 4.0, and the ratio of the raw materials was further changed to obtain a pre-calcined powder with an atomic ratio of Mo:Bi:Fe:Co:Ni:K=12:0.6:2.1:5.7:3.0:0.090. The pre-calcined powder was operated in the same manner as the preparation of catalyst A1 to obtain catalyst D1 with a diameter of 5.30 mm. The reaction rate k of catalyst D1 was 0.62.

[0195] (Catalyst E1)

[0196] In the preparation of catalyst A1, the ratio of raw materials was changed to obtain a pre-calcined powder with an atomic ratio of Mo:Bi:Fe:Co:Ni:K=12:0.8:2.1:6.6:2.2:0.040. The pre-calcined powder was operated in the same manner as the preparation of catalyst A1 to obtain catalyst E1 with a diameter of 5.40 mm. The reaction rate k of catalyst E1 was 0.60.

[0197] [Example 1]

[0198] A temperature jacket for thermocouples with an outer diameter of 3 mm was set in a stainless steel reactor with an inner diameter of 25 mm, and a jacket for circulating molten salt as a heat medium and a thermocouple for measuring the temperature of the catalyst layer was set on the tube axis. From the raw gas inlet side to the gas outlet direction, 120 cm of a diluted catalyst (70 mass % dilution, calculated similarly below) obtained by mixing catalyst B1 and inactive spherical carriers of silica-alumina mixture in a mass ratio of 70:30 as the upper layer (raw gas inlet side), 120 cm of undiluted catalyst B1 as the middle layer, and 160 cm of undiluted catalyst A1 as the lower layer were filled. akt / akn was 1.71. Thus, the catalyst layer was made into a three-layer structure. The reaction bath temperature was set to 315°C, and the supply amounts of propylene, air, water, and nitrogen were set in a raw material molar ratio of propylene: oxygen (oxygen contained in the supplied air): water: nitrogen (nitrogen supplied separately from air) = 1:1.4:1.4:1.6. So that the space velocity of propylene is 190 hours -1 The supply raw material was circulated in a manner, and the pressure on the outlet side of the reaction tube when all gases were circulated was adjusted to 110 kPaG. After 300 hours from the start of the reaction, the reaction bath temperature was changed, and the oxidation reaction of propylene was carried out. The results obtained by changing the reaction bath temperature and investigating the reaction results are shown in Table 1. The peak temperature of each catalyst layer refers to the temperature at the position with the highest temperature in each catalyst layer in the temperature distribution diagram in the reaction tube obtained by measuring the temperature at a specified interval (5 cm interval in this embodiment). It should be noted that the rows without the peak temperature and reaction results of each layer in A1 and A2 in Table 1 mean that A1 and A2 are calculated values ​​calculated by interpolation or extrapolation of the measured data (the same applies hereinafter). In addition, the calculation process of Sf / St at BT of 330°C, where the acrolein yield is the highest, is shown in Table 1-2.

[0199] Table 1

[0200]

[0201] Table 1-2

[0202]

[0203] According to the sum of the field point exothermic temperatures of the first layer = 935, the sum of the field point exothermic temperatures of the second layer = 983, and the sum of the field point exothermic temperatures of the third layer = 837, Sf / St is 837÷(935+983+837)×100=30.4.

[0204] [Example 2]

[0205] The reaction was started in the same manner as in Example 1, except that 120 cm of a diluted catalyst obtained by mixing the catalyst B1 and the silica-alumina mixture inactive spherical carrier at a mass ratio of 80:20 was filled as the upper layer (raw material gas inlet side), 120 cm of the undiluted catalyst B1 was filled as the middle layer, and 160 cm of the undiluted catalyst A1 (akt / akn=1.75) was filled as the lower layer. The reaction was investigated. The results are shown in Table 2.

[0206] Table 2

[0207]

[0208] [Example 3]

[0209] 120 cm of diluted catalyst obtained by mixing catalyst B1 and inactive spherical carrier of silica-alumina mixture in a mass ratio of 70:30 was filled as the upper layer (raw gas inlet side), 180 cm of undiluted catalyst B1 was filled as the middle layer, and 100 cm of undiluted catalyst A1 (akt / akn=2.47) was filled as the lower layer. In addition, as reaction conditions, the supply amounts of propylene, air, water, and nitrogen were set in a raw material molar ratio of propylene: oxygen (oxygen contained in the supplied air): water: nitrogen (nitrogen supplied separately from the air) = 1:1.4:1.4:1.6. The space velocity of propylene was set to 130 h / min. -1 The reaction was started in the same manner as in Example 1, and the reaction results were examined, except that the supply raw material was circulated in a manner of 100 and the pressure on the outlet side of the reaction tube was adjusted to 85 kPaG when all the gases were circulated. The results are shown in Table 3.

[0210] Table 3

[0211]

[0212] [Example 4]

[0213] A temperature jacket for thermocouples with an outer diameter of 6 mm was inserted into a stainless steel reactor with an inner diameter of 27 mm, and 15 cm of silica-alumina balls with a diameter of 5.2 mm were filled from the raw gas inlet side. 77 cm of a diluted catalyst obtained by mixing catalyst B1 and an inactive spherical carrier of a silica-alumina mixture in a mass ratio of 85:15 was filled as the upper layer (raw gas inlet side), 77 cm of undiluted catalyst B1 as the middle layer, and 176 cm of undiluted catalyst A1 (akt / akn=1.45) as the lower layer were filled respectively. In addition, as reaction conditions, the supply amounts of propylene, air, water, and nitrogen were set in a raw material molar ratio of propylene: oxygen (oxygen contained in the supplied air): water: nitrogen (nitrogen supplied separately from air) = 1:1.7:1:2.4. So that the space velocity of propylene is 100 h / min -1 The reaction was started in the same manner as in Example 1, and the reaction results were examined, except that the supply raw material was circulated in a manner of , and the pressure on the outlet side of the reaction tube was adjusted to 35 kPaG when all the gas was circulated. The results are shown in Table 4.

[0214] Table 4

[0215]

[0216] [Example 5]

[0217] A temperature sheath for thermocouples with an outer diameter of 3 mm was inserted into a stainless steel reactor with an inner diameter of 21 mm, and 20 cm of silica-alumina balls with a diameter of 5.2 mm were filled from the raw gas inlet side. 200 cm of undiluted catalyst C1 as the upper layer (raw gas inlet side) and 150 cm of undiluted catalyst D1 (Akt / akn=1.89) as the lower layer were filled respectively. In addition, as reaction conditions, the supply amounts of propylene, air, water, and nitrogen were set in a raw material molar ratio of propylene: oxygen (oxygen contained in the supplied air): water: nitrogen (nitrogen supplied separately from the air) = 1:1.75:0.6:4.35. The space velocity of propylene was set to 180 h / min. -1 The reaction was started in the same manner as in Example 1, and the reaction results were examined, except that the supply raw material was circulated in a manner of 90 kPaG and the pressure on the outlet side of the reaction tube was adjusted to 90 kPaG when all the gas was circulated. The results are shown in Table 5.

[0218] Table 5

[0219]

[0220] [Comparative Example 1]

[0221] The reaction was started in the same manner as in Example 1, except that 75 cm of a diluted catalyst obtained by mixing the catalyst B1 and the silica-alumina mixture inactive spherical carrier at a mass ratio of 75:25 was filled as the upper layer (raw gas inlet side), 75 cm of an undiluted catalyst B1 was filled as the middle layer, and 250 cm of an undiluted catalyst A1 (akt / akn=1.29) was filled as the lower layer. The reaction was investigated. The results are shown in Table 6.

[0222] Table 6

[0223]

[0224] [Comparative Example 2]

[0225] The reaction was started in the same manner as in Example 1, except that 75 cm of a diluted catalyst obtained by mixing the catalyst B2 and the silica-alumina mixture inactive spherical carrier at a mass ratio of 85:15 was filled as the upper layer (raw gas inlet side), 75 cm of an undiluted catalyst B2 was filled as the middle layer, and 250 cm of an undiluted catalyst E1 (akt / akn=1.40) was filled as the lower layer. The reaction was investigated. The results are shown in Table 7.

[0226] Table 7

[0227]

[0228] [Comparative Example 3]

[0229] The reaction was started in the same manner as in Example 1, except that 75 cm of a diluted catalyst obtained by mixing the catalyst B1 and the silica-alumina mixture inactive spherical carrier at a mass ratio of 85:15 was filled as the upper layer (raw material gas inlet side), 75 cm of an undiluted catalyst B1 was filled as the middle layer, and 250 cm of an undiluted catalyst A1 (akt / akn=1.31) was filled as the lower layer. The reaction was investigated. The results are shown in Table 8.

[0230] Table 8

[0231]

[0232] The results so far are summarized as shown in Table 9. As can be seen from Table 9, by obtaining a wide operating window (A2-A1), ΔPTf / ΔBT is significantly reduced. In particular, in the method of producing acrolein from propylene, it is beneficial to the stable operation of the equipment under the above-mentioned reactor and process restrictions. Similarly, it can be seen that by making Sf / St at the reaction bath temperature when the acrolein yield reaches the highest lower than a specific value, ΔPTf / ΔBT is significantly reduced. As described above, it can be seen that the operating window and Sf / St can be controlled by akt / akn.

[0233] Table 9

[0234]

[0235] This application is based on Japanese patent application No. 2022-163792 filed on October 12, 2022, the contents of which are incorporated herein by reference.

[0236] Industrial Applicability

[0237] According to the present invention, the yield in the unsaturated aldehyde production facility can be improved and the runaway reaction can be suppressed, thereby maintaining a stable yield in the industrial facility for a long period of time and enabling stable operation.

Claims

1. A method for producing an unsaturated aldehyde, which is a method for producing the corresponding unsaturated aldehyde by partially oxidizing an olefin using a fixed bed multi-tubular reactor, wherein: The fixed bed multi-tube reactor comprises a plurality of reaction tubes and a reaction bath for adjusting the temperature of the plurality of reaction tubes. In the reaction tube, two or more catalyst layers are arranged in the gas flow direction. When the reaction bath temperature when the yield of the unsaturated aldehyde is the highest is defined as A (°C), and the reaction bath temperature when the yield is 1.0 percentage point lower than the highest value is defined as A1 (°C) and A2 (°C), the following equations (1) and (2) hold: A1<A<A2 (1); (A2-A1)≥10 (2).

2. The method for producing an unsaturated aldehyde according to claim 1, wherein For Sf and St when producing unsaturated aldehyde at the reaction bath temperature A (°C), the following formula (3) holds true: (Sf / St)×100≤42.0 (3) Here, Sf and St are determined by the following operation steps (a) to (c), (a) disposing p (p is an integer greater than or equal to 2) thermocouples at equal intervals in the entire gas flow direction of the two or more catalyst layers provided in the reaction tube, and using the thermocouples to obtain the field point temperatures T1 at p measurement points in the reaction tube when producing unsaturated aldehyde at a reaction bath temperature A (° C.) j (℃)(j is 1~p); (b) For each of the measurement points, calculate the field point temperature T1 j The value obtained by subtracting the reaction bath temperature A (°C) from the reaction bath temperature (T1 j -A) field point exothermic temperature T2 j , where in T1 j -A is a negative value, the field heat release temperature T2 of the measurement point j Set to 0; (c) lowering the field exothermic temperature T2 of all the measuring points in the reaction tube j The total value of is set as St, and the field point heat release temperature T2 of the measurement point set at the catalyst layer closest to the outlet side is set as k The total value (k is 1 to q, q is the number of measurement points provided in the catalyst layer closest to the outlet side, q<p) is referred to as Sf.

3. The method for producing an unsaturated aldehyde according to claim 1 or 2, wherein The catalytically active component contained in the catalyst layer closest to the inlet side of the reaction raw material gas has a composition represented by the following formula (I-1): Mo a1 Bi b1 Ni c1 Co d1 Feb e1 X f1 Cs g1 Z h1 O i1 (I-1) (In the formula, Mo, Bi, Ni, Co, Fe, Cs and O represent molybdenum, bismuth, nickel, cobalt, iron, cesium and oxygen respectively, X represents at least one element selected from tungsten, antimony, tin, zinc, chromium, manganese, magnesium, silicon, aluminum, cerium and titanium, Z represents at least one element belonging to Group 1 to Group 16 of the periodic table and selected from elements other than Mo, Bi, Ni, Co, Fe, Cs, O and X, a1, b1, c1, d1, e1, f1, g1, h1 and i1 represent the atomic numbers of molybdenum, bismuth, nickel, cobalt, iron, X, Cs, Z and oxygen respectively, when a1=12, 0<b1≤7.0, 0≤c1≤10, 0<d1≤10, 0<e1≤5.0, 0≤f1≤2.0, 0<g1≤3.0, 0≤h1≤5.0 are satisfied, and i1 is a value determined by the oxidation state of each element).

4. The method for producing an unsaturated aldehyde according to claim 1 or 2, wherein The catalytically active component contained in the catalyst layer closest to the outlet side of the reaction raw material gas has a composition represented by the following formula (I-2): Mo a2 Bi b2 Ni c2 Co d2 Feb e2 X f2 K g2 Z h2 O i2 (I-2) (In the formula, Mo, Bi, Ni, Co, Fe and K represent molybdenum, bismuth, nickel, cobalt, iron and potassium respectively, X represents at least one element selected from tungsten, antimony, tin, zinc, chromium, manganese, magnesium, silicon, aluminum, cerium and titanium, Z represents at least one element belonging to Group 1 to Group 16 of the periodic table and selected from elements other than Mo, Bi, Ni, Co, Fe, K, O and X, a2, b2, c2, d2, e2, f2, g2, h2 and i2 represent the atomic numbers of molybdenum, bismuth, nickel, cobalt, iron, X, K, Z and oxygen respectively, when a2=12, 0<b2≤7.0, 0≤c2≤10, 0<d2≤10, 0<e2≤5.0, 0≤f2≤2.0, 0≤g2≤3.0, 0≤h2≤5.0 are satisfied, and i2 is a value determined by the oxidation state of each element).

5. The method for producing an unsaturated aldehyde according to claim 1 or 2, wherein The reaction bath temperature is 310° C. or higher and 340° C. or lower.

6. The method for producing an unsaturated aldehyde according to claim 1 or 2, wherein The volume ratio of oxygen to olefin in the reaction raw material gas (oxygen / olefin) is 1.0 or more and 1.8 or less.

7. The method for producing an unsaturated aldehyde according to claim 1 or 2, wherein The reaction tube does not have an inert layer at a position closer to the inlet side than the catalyst layer.

8. The method for producing an unsaturated aldehyde according to claim 1 or 2, wherein In the reaction tube, three catalyst layers are arranged in the gas flow direction. The ratio of the sum of the filling lengths of the first layer and the second layer to the filling length of the third layer from the inlet side of the reaction tube ((filling length of the first layer+filling length of the second layer) / filling length of the third layer) is 1.5 or more and 3.5 or less.

9. The method for producing an unsaturated aldehyde according to claim 1 or 2, wherein In the reaction tube, two or more catalyst layers are arranged in the gas flow direction, and the type, dilution rate and filling length of the catalyst in each catalyst layer are set in such a way that akt / akn defined by the following formulas (II), (III) and (IV) is greater than 1.41 and less than 10.00, The reaction rate of the catalyst k=-Ln(1-x / 100) (II) The actual reaction rate of the catalyst layer ak = (the dilution rate of the catalyst layer) × (the filling length of the catalyst layer) × (the reaction rate of the catalyst in the catalyst layer k) (III) akt / akn = (value obtained by adding up the substantial reaction rates ak of all catalyst layers) / (substantial reaction rate ak of the catalyst layer closest to the outlet of the reaction tube) (IV) Here, x is the raw material gas conversion rate (%) when the catalyst is filled in a differential system reactor and the partial oxidation reaction of the olefin is carried out at a reaction bath temperature of 360°C.

10. An apparatus for producing an unsaturated aldehyde, the apparatus being for producing the corresponding unsaturated aldehyde by partially oxidizing an olefin, wherein: The unsaturated aldehyde production device comprises a fixed bed multi-tube type reactor having a plurality of reaction tubes and a reaction bath for adjusting the temperature of the plurality of reaction tubes. In the reaction tube, two or more catalyst layers are arranged in the gas flow direction. When the reaction bath temperature when the yield of the unsaturated aldehyde is the highest is defined as A (°C), and the reaction bath temperature when the yield is 1.0 percentage point lower than the highest value is defined as A1 (°C) and A2 (°C), the following equations (1) and (2) hold: A1<A<A2 (1); (A2-A1)≥10 (2).

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