JP2014019675A - Process for producing unsaturated aldehyde and/or unsaturated carboxylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a safe and stable, high-yield process for producing acrolein, acrylic acid, methacrolein and methacrylic acid, which can, when catalytically oxidizing propylene, isobutylene or the like in a gas phase, avoid a phenomenon where an abnormal reaction is caused by considerable increase in temperature of a catalyst loaded in a reaction tube at an inlet side of a raw material than that at an outlet side of the raw material gas.SOLUTION: There is provided a production process, wherein catalyst and catalyst loading specifications are designed so that a specific condition of 0.5≤Cmax-Ccrs is satisfied, wherein Cmax represents a rate of raw material conversion at which a yield of a desired product becomes maximum; and Ccrs represents a rate of raw material conversion at which, when a maximum temperature of a catalyst layer Zin is denoted by Tin and the maximum temperature of a catalyst layer Zout is denoted by Tout, a magnitude relation of Tin and Tout reverses.

Description

  The present invention is a method for producing acrolein and acrylic acid by vapor-phase catalytic oxidation of propylene with molecular oxygen or a molecular oxygen-containing gas, or isobutylene and tertiary butanol with a molecular oxygen or a molecular oxygen-containing gas in a gas phase. The present invention relates to a method for producing methacrolein and methacrylic acid by catalytic oxidation.

  The production of corresponding unsaturated aldehydes and unsaturated carboxylic acids from propylene, isobutylene and tertiary butanol as raw materials is widely practiced industrially, but local high temperature portions (hot spots) are generated in the catalyst layer. Is a big problem. Since generation of hot spots leads to shortening of catalyst life, reduction of yield due to excessive oxidation reaction, and in the worst case, runaway reaction, several techniques for suppressing hot spots have been proposed. For example, Patent Document 1 discloses a technique for reducing the hot spot temperature by using a catalyst whose activity is adjusted by changing the loading amount, or by using a catalyst whose activity is adjusted by changing the calcination temperature of the catalyst. . Patent Document 2 discloses a technique of using a catalyst whose activity is adjusted by changing the ratio of the apparent density of the catalyst. Patent Document 3 uses a catalyst whose activity is adjusted by changing the content of the inactive component of the catalyst molded body, changing the occupied volume of the catalyst molded body, the type and / or amount of alkali metal, and the firing temperature of the catalyst. Techniques to do this are disclosed. Patent Document 4 discloses a technique in which a reaction zone in which the occupied volume of a catalyst molded body is changed is provided and an inert substance is mixed in at least one reaction zone. Patent Document 5 discloses a technique of using a catalyst whose activity is adjusted by changing the calcination temperature of the catalyst. Patent Document 6 discloses a technique of using a catalyst whose activity is adjusted by changing the occupied volume of the catalyst and the calcination temperature and / or the type and amount of alkali metal.

Japanese Patent No. 3775872 Japanese Unexamined Patent Publication No. 20004209 Japanese Unexamined Patent Application Publication No. 20011328951 Japanese Laid-Open Patent Publication No. 2005320315 Japanese Unexamined Patent Publication No. 8-3093 Japanese Patent Laid-Open No. 2001226302

Even if the hot spot is suppressed by the above means, it is still not sufficient. Furthermore, there has been a problem that catalyst performance and life expected in an industrial plant may not always be obtained, and improvement has been desired. For example,
1) The method of using a catalyst whose activity is adjusted by changing the occupied volume of the catalyst is a useful method for suppressing hot spots, but there are tens of thousands of reaction tubes in an industrial plant, When the inner diameter of the reaction tube is 20 mm to 30 mm, an error may occur about ± 0.2 mm. In the case of a catalyst with a small occupied volume, these effects are negligible. However, it has been found that the influence may not be negligible with a catalyst with a large occupied volume, that is, a catalyst with a large catalyst particle size. Specifically, a bridge is formed in the reaction tube at the time of filling, which requires a lot of labor to correct it, and the difference in pressure loss tends to vary from reaction tube to reaction tube due to changes in the filling amount and packing density. In other words, the gas flow rate is unevenly distributed, and correction thereof requires a great deal of labor. It can be easily imagined that this problem becomes more prominent when the catalyst shape is not spherical.
2) Furthermore, in industrial plants, not only the variation in reaction tube diameter as described above, but also the variation in heat removal capacity derived from the reactor structure, the heat medium temperature distribution in the horizontal and vertical directions, and the gas flow rate for each reaction tube. Distribution may occur, and it is almost impossible that the catalyst is used in the same state in all reaction tubes. When the present inventors analyzed the catalyst used in the industrial plant, the reaction tube in which the catalyst in the raw material gas inlet portion is concentrated and deteriorated, the reaction tube in which the catalyst is gradually deteriorated over the whole, Surprisingly, a reaction tube was found in which the catalyst at the outlet portion of the raw material gas was deteriorated more than the catalyst at the inlet portion. This suggests that the hot spot temperature of the catalyst layer on the source gas outlet side may be abnormally high, and in the worst case, there is a risk of causing a runaway reaction. This is due to the variation in the reaction tube diameter in the industrial plant mentioned above, the variation in the heat removal capability derived from the reactor structure, the heat medium temperature distribution in the horizontal and vertical directions, and the gas flow velocity distribution in each reaction tube. The conversion rate was different and the shape of the temperature distribution was expected to be the cause, and the development of a technology that can safely and stably maintain a high yield over a long period was cited as an issue in industrial plants.

  The inventors of the present invention preferably operate the industrial plant at a raw material conversion rate at which the catalyst yields the maximum yield, and in many reaction tubes, the catalyst is used so that the upper limit temperature of the catalyst used at the raw material conversion rate is not exceeded. Although there are deviations in the reaction conditions in the industrial plant described above, there are reaction tubes in which the raw material conversion rate such as propylene becomes small in the entire reactor, and the catalyst layer temperature Zout on the raw material gas outlet side May exceed the upper limit temperature of the catalyst, resulting in insufficient reaction yield, insufficient catalyst life, and risk of runaway reaction. In the method using the reaction tube provided with the catalyst layer formed in the above, the raw material conversion rate that maximizes the yield of the target product, the catalyst layer closest to the reaction gas inlet, and the catalyst layer closest to the reaction gas outlet To find out that the above problems can be solved by designing the catalyst and catalyst filling specifications so that the relationship with the raw material conversion rate when the magnitude relationship of each maximum temperature is reversed satisfies a specific condition. It came.

That is, the present invention
(1) Acrolein and acrylic acid obtained by gas phase catalytic oxidation of propylene or at least one selected from isobutylene and tertiary butanol with a gas containing molecular oxygen using a fixed bed multitubular reactor, or In producing methacrolein and methacrylic acid,
A) A plurality of catalyst layers formed by N division (N is an integer of 2 or more) in the direction of the raw material gas flow in the reaction tube are provided, and the catalyst layer on the most reaction gas inlet side among the catalyst layers is Zin, The catalyst layer on the reaction gas outlet side is Zout,
B) Acrolein and acrylic acid or methacrolein and methacrylic are charged so that the activity of the catalyst charged in Zout is higher than the activity of the catalyst charged in Zin and satisfies the following formula (1): Acid production method,
0.5 ≦ Cmax−Ccrs Formula (1)
Cmax: Raw material conversion rate at which the yield of the target product is maximized Ccrs: The maximum temperature of the catalyst layer Zin is Tin, the maximum temperature of the catalyst layer Zout is Tout, and the magnitude of Tin and Tout is changed when the raw material conversion rate is changed Raw material conversion rate when relationship is reversed,
(2) The process for producing acrolein and acrylic acid or methacrolein and methacrylic acid according to (1), which satisfies 0.5 ≦ Cmax−Ccrs ≦ 10,
(3) The process for producing acrolein and acrylic acid or methacrolein and methacrylic acid according to (1), which satisfies 0.5 ≦ Cmax−Ccrs ≦ 5,
(4) N is 3 or less, and the firing temperature of the catalyst filled in Zin is set to be higher than the firing temperature of the catalyst filled in Zout, and Zin is filled with the mixture of the catalyst and the inert substance molding (1) ) To (3), acrolein and acrylic acid, or a method for producing methacrolein and methacrylic acid,
(5) The method for producing acrolein and acrylic acid or methacrolein and methacrylic acid according to the above (1) to (4), wherein the catalyst is a spherical supported catalyst obtained by supporting an active powder on an inert substance.
(6) The method for producing acrolein and acrylic acid or methacrolein and methacrylic acid according to any one of the above (1) to (5), wherein the particle size of the catalyst filled in each catalyst layer is the same throughout all layers.
About.

According to the present invention, a normal industrial plant is operated at a raw material conversion rate that yields the highest yield unless there are special circumstances, and a catalyst packed in many reaction tubes is reacted at a desired raw material conversion rate. As a result, although the catalyst layer hot spot temperature at the source gas inlet portion is higher than the hot spot temperature of the catalyst at the source gas outlet side, there is a reaction tube in which the raw material conversion rate decreases due to an event peculiar to an industrial plant. As a result, the temperature of the catalyst filled in the reaction tube is considerably higher on the source gas outlet side than on the source gas inlet side, so that it is possible to avoid a phenomenon in which an abnormal reaction occurs, and safely and stably. It becomes possible to produce acrolein and acrylic acid or methacrolein and methacrylic acid in high yield.
Such a phenomenon cannot be unequivocally stated because it is likely to occur depending on the composition, shape, reaction conditions, etc. of the catalyst, and the degree thereof. However, when the inner diameter of the reaction tube to be used is 25 mm or more, the raw material gas When the molar ratio of water to propylene is 3.0 or less, the problem tends to become more prominent.

Next, preferred modes for carrying out the present invention will be described.
The catalyst itself of the present invention can be prepared by a known method, and is represented by the following general formula, for example.

_{Mo a Bi b Ni c Co d} Fe f X g Y h O x

(Wherein Mo, Bi, Ni, Co, and Fe represent molybdenum, bismuth, nickel, cobalt, and iron, respectively, and X represents tungsten, antimony, tin, zinc, chromium, manganese, magnesium, silica, aluminum, cerium, and titanium. At least one element selected, Y means at least one element selected from potassium, rubidium, thallium and cesium; a, b, c, d, f, g, h, x are molybdenum, bismuth, Represents the number of atoms of nickel, cobalt, iron, X, Y and oxygen, a = 12, b = 0.1-7, preferably b = 0.5-4, c + d = 0.5-20, more preferably c + d = 1 to 12, f = 0.5 to 8, more preferably f = 0.5 to 5, g = 0 to 2, particularly preferably g = 0 to 1, h = 0.005 2, most preferably h = 0.01 to 0.5, x = a value determined by the oxidation state of each element.)

  Here, the powder containing the catalytically active component is prepared by a known method such as a coprecipitation method or a spray drying method, and the obtained powder is preferably 200 to 600 ° C., more preferably 300 to 500 ° C., preferably air. Alternatively, the catalyst active component (hereinafter referred to as pre-calcined powder) can be obtained by firing in a nitrogen stream.

  The pre-calcined powder thus obtained can be used as a catalyst as it is, but is molded into the catalyst of the present invention in consideration of production efficiency and workability. The shape of the molded product is not particularly limited, such as a spherical shape, a cylindrical shape, or a ring shape. The shape should be selected in consideration of the production efficiency of the catalyst, the mechanical strength, etc., but the spherical shape is preferable. When molding, it is common to use a single pre-baked powder and mold it, but separately prepared pre-baked powder of granules with different component compositions such as iron, cobalt, nickel, alkali metal etc. May be mixed and molded in advance, or a method may be employed in which the precalcined powder is molded into multiple layers by repeating the operation of supporting different types of precalcined powder on the inert carrier. In molding, it is preferable to mix a molding aid such as crystalline cellulose and / or a strength improver such as a ceramic whisker. The amount of the molding aid and / or strength improver used is preferably 30% by weight or less with respect to the pre-fired powder. Further, the molding aid and / or the strength improver may be mixed in advance with the above pre-fired powder before molding, or may be added at the same time as or before or after the pre-fired powder is added to the molding machine.

Although there is no particular limitation on the molding method, a method using a tableting molding machine, an extrusion molding machine or the like is preferable when molding into a cylindrical shape or a ring shape.
More preferably, it is a case of forming into a spherical shape, and the pre-fired powder may be formed into a spherical shape with a molding machine, but the pre-fired powder (including a molding aid and a strength improver if necessary) is an inert ceramic. A method of supporting it on a carrier such as the like is preferable. Here, the loading method is not particularly limited as long as it is a rolling granulation method, a method using a centrifugal fluidized coating apparatus, or a method in which a pre-fired powder such as wash coat can be uniformly loaded on a carrier, but considering the production efficiency of the catalyst, etc. In this case, the carrier loaded in the container can be rotated and revolved by rotating the disk at a high speed with a device having a flat or uneven disk at the bottom of the fixed cylindrical container. A method in which the powder component is supported on a carrier by repeatedly stirring vigorously and adding a pre-calcined powder and, if necessary, a molding aid and a strength improver is preferable. In addition, it is preferable to use a binder for carrying. Specific examples of the binder that can be used include water, ethanol, methanol, propanol, polyhydric alcohol, polyvinyl alcohol as a polymer binder, silica sol aqueous solution of an inorganic binder, etc., ethanol, methanol, propanol, polyhydric alcohol, etc. Alcohols are preferred, diols such as ethylene glycol and triols such as glycerin are preferred, and aqueous solutions having a glycerin concentration of 5% by weight or more are preferred. By using an appropriate amount of an aqueous glycerin solution, the moldability becomes good, and a highly active high performance catalyst with high mechanical strength can be obtained.
The amount of these binders used is usually 2 to 60 parts by weight with respect to 100 parts by weight of the pre-fired powder. The binder may be pre-mixed with the pre-fired powder during loading, or may be added while supplying the pre-fired powder to the rolling granulator.
An inert carrier having a diameter of about 2 to 15 mm is usually used, and pre-calcined powder is supported on the inert carrier, but the amount supported is determined in consideration of the conditions for using the catalyst, such as space velocity and raw hydrocarbon concentration. The
The molded catalyst is calcined again before use in the reaction. The firing temperature at the time of firing again is usually 450 to 650 ° C., the firing time is usually 3 to 30 hours, preferably 4 to 15 hours, and is appropriately set according to the reaction conditions to be used. At this time, the firing temperature of the catalyst installed on the raw material gas inlet side is preferably controlled by firing at a higher temperature than the catalyst on the gas outlet side, regardless of the composition. The firing atmosphere may be either an air atmosphere or a nitrogen atmosphere, but industrially an air atmosphere is preferred.

The catalyst thus obtained is a step of producing acrolein and acrylic acid by vapor-phase catalytic oxidation of propylene with molecular oxygen or a molecular oxygen-containing gas, or isobutylene, tertiary butanol with molecular oxygen or a molecular oxygen-containing gas. Can be used in the step of producing methacrolein and methacrylic acid by gas phase catalytic oxidation. In the production method of the present invention, the flow method of the source gas may be a normal single flow method or a recycle method, and can be carried out under generally used conditions and is not particularly limited. For example, propylene, isobutylene and tertiary butanol as starting materials are preferably 1 to 10% by volume, more preferably 4 to 9% by volume, and molecular oxygen is preferably 3 to 20% by volume, more preferably 4 at room temperature. ~ 18% by volume, water vapor is preferably 0 ~ 60% by volume, more preferably 4 ~ 50% by volume, inert gas such as carbon dioxide and nitrogen is preferably 20 ~ 80% by volume, more preferably 30 ~ 60% by volume The reaction is carried out on a catalyst of the present invention filled with a mixed gas consisting of the following at 250 to 450 ° C. under atmospheric pressure to 10 atm at a space velocity of 300 to 5000 h ⁻¹ . The above reaction can be carried out using a single type of catalyst in the catalyst layer, but in the method of the present invention, N (N is an integer of 2 or more) divided catalyst layers are provided. The hot spot temperature can be lowered.
And in the method of the present invention,
Of the catalyst layers formed by dividing the reaction tube in the raw material gas flow direction, the catalyst layer closest to the reaction gas inlet is Zin, the catalyst layer closest to the reaction gas outlet is Zout,
The catalyst is filled so that the activity of the catalyst filling Zout is higher than the activity of the catalyst filling Zin so as to satisfy the following formula (1).
0.5 ≦ Cmax−Ccrs Formula (1)
Cmax: Raw material conversion rate at which the yield of the desired product is maximized.
Ccrs: Raw material conversion rate when the maximum temperature of the catalyst layer Zin is Tin, the maximum temperature of the catalyst layer Zout is Tout, and the magnitude relationship between Tin and Tout is reversed when the raw material conversion rate is changed.
In the formula (1), 0.5 ≦ Cmax−Ccrs ≦ 10 is preferable, and 0.5 ≦ Cmax−Ccrs ≦ 5 is more preferable.

More specifically, the composition of the catalyst on the raw material gas inlet side, the calcination temperature, the mixing ratio with the inert material, the filling length, the composition of the catalyst on the raw material gas outlet side, the calcination temperature, and the filling length are set to 0.5 ≦ Cmax−. Determine to satisfy Ccrs. Note that Cmax-Ccrs varies with the time of operation, but in order to exert the effects of the present invention, 0.5 ≦ Cmax-Ccrs is satisfied for at least one year from the start of use of the catalyst, preferably until the catalyst is replaced. It is preferable. This is because the catalyst immediately after the start of use tends to increase the value of Zout in particular because the raw material conversion rate decreases. In general, Cmax-Ccrs tends to be small due to deterioration of the catalyst filled in Zin with the passage of time. Therefore, although depending on the catalyst used, the effect of the present invention can be maintained over a long period of time by designing the packing specifications so that the value is larger than 0.5, preferably 1 or more at the start of the reaction. In the above examination, it is preferable to determine the packing conditions of the catalyst with an experimental apparatus that can be tested under the same conditions before use in an industrial plant, and it is also possible to use a computer simulation together.
For computer simulation, CFD (Computational Fluid Dynamics) is generally used. Calculate by including data such as physical property values, reaction rate constants, reaction heat, etc. of catalysts used in commercially available software, conversion rate of raw materials under desired reaction conditions, yield of acrolein and acrylic acid, etc. Temperature distribution can be calculated.
In obtaining Cmax and Ccrs in an industrial plant or an experimental apparatus, the temperature distribution of the catalyst layer is measured using a thermocouple with a measurement width smaller than 10 cm. Measurement with a measurement width larger than 10 cm is not preferable because the temperature of the hot spot may not be accurately captured. In addition, the conversion rate of the raw material gas was changed by intentionally changing the reaction bath temperature, and the raw material conversion rate at each reaction bath temperature, the yield of active ingredients at each raw material conversion rate, and the hot spot temperature were measured, graphed, and data Cmax and Ccrs are obtained by interpolating. More accurate data can be obtained by changing the reaction bath temperature with a measurement width smaller than 5 ° C.
According to the present invention, by setting 0.5 ≦ Cmax−Ccrs, almost all reaction tubes can be obtained even if there is a deviation in reaction temperature inside the reactor, a deviation in gas flow state, and a differential pressure deviation in each reaction tube in an industrial plant. Thus, the hot spot temperature (ie, Tout) of the catalyst on the raw material gas outlet side can be prevented from becoming abnormally high, and stable and safe operation can be achieved. Further, by setting Cmax−Ccrs ≦ 5, there is a tendency that Tin can be controlled to a relatively low temperature.
As described above, subtle adjustment of the catalyst filling specifications is required depending on the operating conditions, but as in the present invention, the calcination temperature at the time of preparation of the catalyst used on the raw material gas inlet side is adjusted at the time of preparation of the catalyst used on the gas outlet side. The filling specification can be changed relatively easily by making the temperature higher than the baking temperature and diluting with an inert substance.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the examples.
The conversion, selectivity and yield in the present invention are defined as follows.
Propylene conversion (mol%)
= Number of moles of propylene reacted / number of moles of propylene fed x 100
Acrolein yield (mol%)
= Number of moles of acrolein produced / number of moles of propylene supplied x 100
Acrylic acid yield (mol%)
= Number of moles of acrylic acid produced / number of moles of propylene supplied x 100
When the raw material is isobutylene and / or tertiary butanol instead of propylene, acrolein can be replaced with methacrolein and acrylic acid can be replaced with methacrylic acid.

Example 1
(Preparation of catalyst)
While heating and stirring 3000 parts by weight of distilled water, 423.8 parts by weight of ammonium molybdate and 1.64 parts by weight of potassium nitrate were dissolved to obtain an aqueous solution (A1). Separately, 302.7 parts by weight of cobalt nitrate, 162.9 parts by weight of nickel nitrate, and 145.4 parts by weight of ferric nitrate are dissolved in 1000 parts by weight of distilled water to prepare an aqueous solution (B1), and 42 parts by weight of concentrated nitric acid. In addition, 164.9 parts by weight of bismuth nitrate was dissolved in 200 parts by weight of distilled water acidified to prepare aqueous solutions (C1). (B1) and (C1) are sequentially mixed with the aqueous solution (A1) with vigorous stirring, and the resulting suspension is dried using a spray dryer and calcined at 440 ° C. for 6 hours to obtain a pre-calcined powder (D1). Obtained. At this time, the composition ratio of the catalytically active component excluding oxygen is Mo = 12, Bi = 1.7, Ni = 2.8, Fe = 1.8, Co = 5.2, K = 0.15 in atomic ratio. Met.
Thereafter, a powder obtained by mixing 5 parts by weight of crystalline cellulose with 100 parts by weight of the pre-fired powder is formed into an inert carrier (a spherical substance having a diameter of 4.5 mm mainly composed of alumina and silica), and 50% by weight based on the catalyst after molding. A supported catalyst (E1) was obtained by supporting and molding into a spherical shape having a diameter of 5.2 mm using a 20% by weight glycerin aqueous solution as a binder so as to be occupied.
The supported catalyst (E1) was calcined in an air atmosphere at a calcining temperature of 530 ° C. for 4 hours to obtain a catalyst (F1).
Next, while heating and stirring 3000 parts by weight of distilled water, 423.8 parts by weight of ammonium molybdate and 1.08 parts by weight of potassium nitrate were dissolved to obtain an aqueous solution (A2). Separately, 302.7 parts by weight of cobalt nitrate, 162.9 parts by weight of nickel nitrate, and 145.4 parts by weight of ferric nitrate are dissolved in 1000 parts by weight of distilled water to prepare an aqueous solution (B2), and 42 parts by weight of concentrated nitric acid. In addition, 164.9 parts by weight of bismuth nitrate was dissolved in 200 parts by weight of distilled water acidified to prepare aqueous solutions (C2). (B2) and (C2) are mixed with the above aqueous solution (A2) successively with vigorous stirring, and the resulting suspension is dried using a spray dryer and calcined at 440 ° C. for 6 hours to obtain a pre-calcined powder (D2). Obtained. At this time, the composition ratio of the catalytically active component excluding oxygen is Mo = 12, Bi = 1.7, Ni = 2.8, Fe = 1.8, Co = 5.2, K = 0.10 in atomic ratio. Met.
Thereafter, a powder obtained by mixing 5 parts by weight of crystalline cellulose with 100 parts by weight of the pre-fired powder is formed into an inert carrier (a spherical substance having a diameter of 4.5 mm mainly composed of alumina and silica), and 50% by weight based on the catalyst after molding. A supported catalyst (E2) was obtained by supporting and molding into a spherical shape having a diameter of 5.2 mm using a 20% by weight glycerin aqueous solution as a binder so as to be occupied.
The supported catalyst (E2) was calcined at 530 ° C. for 4 hours to obtain a catalyst (F2). The supported catalyst (E2) was calcined at 510 ° C. for 4 hours to obtain a catalyst (F3).

(Oxidation reaction test)
Silica having a diameter of 5.2 mm from the raw material gas inlet side of a stainless steel reactor having an inner diameter of 25.4 mm, in which a jacket for circulating the molten salt as a heat medium and a thermocouple for measuring the catalyst layer temperature are installed on the tube axis -20 cm of alumina spheres, 100 cm of a diluted catalyst in which the oxidation catalyst (F1) and a silica-alumina mixture inert carrier having a diameter of 5.2 mm were mixed at a weight ratio of 4: 1 as the first oxidation catalyst layer (raw material gas inlet side), The oxidation catalyst (F3) was filled in the order of 250 cm as the oxidation catalyst second layer (gas outlet side), and the reaction bath temperature was set to 330 ° C. Here, a gas in which the supply amounts of propylene, air, nitrogen and water are set so that the raw material molar ratio is propylene: oxygen: nitrogen: water = 1: 1.7: 8.8: 1 at a space velocity of 1500 h ⁻¹ . When introduced into the oxidation reactor and the reactor outlet pressure is 70 kPaG and 200 hours have elapsed after the start of the reaction, the reaction bath temperature is changed in increments of 2 ° C., and the raw material conversion, acrolein, acrylic acid yield, and hot spot temperature are changed. When a test to be measured (hereinafter referred to as reaction temperature change test) was carried out, the raw material conversion was 97.8%, and the total yield of acrolein and acrylic acid was 91.8% at the maximum. At this time, the reaction bath temperature was 330 ° C., the hot spot temperature of the catalyst layer on the gas inlet side was 434 ° C., and the hot spot temperature of the catalyst layer on the gas outlet side was 378 ° C. The magnitude relationship between these two hot spot temperatures was reversed when the raw material conversion rate was 95.5%. That is, Cmax−Ccrs = 2.3. The propylene conversion was 93% at a reaction bath temperature of 320 ° C., but the hot spot temperature of the catalyst layer on the gas inlet side was 352 ° C., and the hot spot temperature of the catalyst layer on the gas outlet side was 401 ° C. Thus, it was suggested that even when the propylene conversion rate greatly decreased, the hot spot temperature of the catalyst layer on the gas outlet side did not become extremely high, and stable operation was possible for a long period of time.

Example 2
The catalyst charged in the raw material gas inlet portion under the oxidation reaction conditions of Example 1 is a diluted catalyst of 120 cm in which F2 and a silica-alumina mixture inert carrier having a diameter of 5.2 mm are mixed at a weight ratio of 4: 1. The propylene oxidation reaction was carried out in the same manner as in Example 1 except that the catalyst to be filled was 230 cm of F3 catalyst.
When the reaction temperature change test was conducted, the raw material conversion was 97.2%, and the total yield of acrolein and acrylic acid was 92.1% at the maximum. At this time, the reaction bath temperature was 332 ° C., the hot spot temperature of the catalyst layer on the gas inlet side was 431 ° C., and the hot spot temperature of the catalyst layer on the gas outlet side was 372 ° C. The magnitude relationship between these two hot spot temperatures was reversed when the raw material conversion rate was 95.1%. That is, Cmax−Ccrs = 2.1. The propylene conversion was 93% at a reaction bath temperature of 322 ° C., but the hot spot temperature of the catalyst layer on the gas inlet side was 353 ° C., and the hot spot temperature of the catalyst layer on the gas outlet side was 398 ° C. Thus, it was suggested that even when the propylene conversion rate greatly decreased, the hot spot temperature of the catalyst layer on the gas outlet side did not become extremely high, and stable operation was possible for a long period of time.

Example 3
In Example 2, a gas having a feed rate of propylene, air, nitrogen, and water so that the raw material molar ratio is propylene: oxygen: nitrogen: water = 1: 1.8: 10: 1.5 is a space velocity of 1500 h. ^-1 was introduced into the oxidation reactor and tested in the same manner as in Example 2 except that the reactor outlet pressure was 55 kPaG. The raw material conversion was 97.9%, and the total yield of acrolein and acrylic acid was The maximum was 92.3%. At this time, the reaction bath temperature was 330 ° C., the hot spot temperature of the catalyst layer on the gas inlet side was 424 ° C., and the hot spot temperature of the catalyst layer on the gas outlet side was 370 ° C. The magnitude relationship between these two hot spot temperatures was reversed when the raw material conversion rate was 96.2%. That is, Cmax−Ccrs = 1.7. The propylene conversion was 95% at a reaction bath temperature of 318 ° C., but the hot spot temperature of the catalyst layer on the gas inlet side was 348 ° C., and the hot spot temperature of the catalyst layer on the gas outlet side was 410 ° C. Thus, it was suggested that even when the propylene conversion rate greatly decreased, the hot spot temperature of the catalyst layer on the gas outlet side did not become extremely high, and stable operation was possible for a long period of time.

Example 4
In Example 3, when the space velocity was introduced into the oxidation reactor at 1715 h ⁻¹ and the reactor outlet pressure was set to 70 kPaG, a test was conducted in the same manner as in Example 3 to find that the raw material conversion was 97.8% and that acrolein was used. And the total yield of acrylic acid was 91.6% at maximum. At this time, the reaction bath temperature was 332 ° C., the hot spot temperature of the catalyst layer on the gas inlet side was 429 ° C., and the hot spot temperature of the catalyst layer on the gas outlet side was 371 ° C. The magnitude relationship between these two hot spot temperatures was reversed when the raw material conversion rate was 96.1%. That is, Cmax−Ccrs = 1.7. The propylene conversion was 95% at a reaction bath temperature of 319 ° C., but the hot spot temperature of the catalyst layer on the gas inlet side was 350 ° C., and the hot spot temperature of the catalyst layer on the gas outlet side was 414 ° C. Thus, it was suggested that even when the propylene conversion rate greatly decreased, the hot spot temperature of the catalyst layer on the gas outlet side did not become extremely high, and stable operation was possible for a long period of time.

Example 5
In Example 2, a gas having a feed rate of propylene, air, nitrogen, and water so that the raw material molar ratio is propylene: oxygen: nitrogen: water = 1: 1.9: 12: 1 is a space velocity of 2000 h ^−1. Was introduced into the oxidation reactor, the reactor outlet pressure was 65 kPaG, and acrolein was used as the target product, and the test was conducted in the same manner as in Example 2. As a result, the raw material conversion was 96.5% and the acrolein yield was the highest. It became 85.2%. At this time, the reaction bath temperature was 334 ° C., the hot spot temperature of the catalyst layer on the gas inlet side was 420 ° C., and the hot spot temperature of the catalyst layer on the gas outlet side was 385 ° C. The magnitude relationship between these two hot spot temperatures was reversed when the raw material conversion rate was 95.5%. That is, Cmax−Ccrs = 1.0. The propylene conversion was 94% at a reaction bath temperature of 326 ° C., but the hot spot temperature of the catalyst layer on the gas inlet side was 347 ° C., and the hot spot temperature of the catalyst layer on the gas outlet side was 415 ° C. Thus, it was suggested that even when the propylene conversion rate greatly decreased, the hot spot temperature of the catalyst layer on the gas outlet side did not become extremely high, and stable operation was possible for a long period of time.

Example 6
Silica having a diameter of 5.2 mm from the raw material gas inlet side of a stainless steel reactor having an inner diameter of 27.2 mm, in which a jacket for circulating the molten salt as a heat medium and a thermocouple for measuring the catalyst layer temperature are installed on the tube axis -20 cm of alumina spheres, 100 cm of a diluted catalyst obtained by mixing the oxidation catalyst (F1) and a silica-alumina mixture inert carrier having a diameter of 5.2 mm at a weight ratio of 3: 1 as an oxidation catalyst layer first layer (source gas inlet side), The oxidation catalyst (F3) was packed in the order of 210 cm as the oxidation catalyst second layer (gas outlet side), and the reaction bath temperature was 325 ° C. Here, a gas in which the supply amounts of propylene, air, nitrogen, and water are set so that the raw material molar ratio is propylene: oxygen: nitrogen: water = 1: 1.7: 8.8: 1 at a space velocity of 1250 h ⁻¹ . When introduced into the oxidation reactor and the reactor outlet pressure was 50 kPaG and 200 hours had passed after the start of the reaction, a reaction temperature change test was conducted by changing the reaction bath temperature in increments of 2 ° C., and the raw material conversion rate was 97.8%. The total yield of acrolein and acrylic acid was 91.5% at maximum. At this time, the reaction bath temperature was 322 ° C., the hot spot temperature of the catalyst layer on the gas inlet side was 424 ° C., and the hot spot temperature of the catalyst layer on the gas outlet side was 373 ° C. The magnitude relationship between these two hot spot temperatures was reversed when the raw material conversion rate was 96.6%. That is, Cmax−Ccrs = 1.2. The propylene conversion was 92% at a reaction bath temperature of 310 ° C., but the hot spot temperature of the catalyst layer on the gas inlet side was 330 ° C., and the hot spot temperature of the catalyst layer on the gas outlet side was 400 ° C. Thus, it was suggested that even when the propylene conversion rate greatly decreased, the hot spot temperature of the catalyst layer on the gas outlet side did not become extremely high, and stable operation was possible for a long period of time.

Comparative Example 1
In the oxidation reaction conditions of Example 1, the catalyst charged in the raw material gas inlet portion is a dilute catalyst 100 cm in which F3 and a silica-alumina mixture inert carrier having a diameter of 5.2 mm are mixed at a weight ratio of 2: 1, and the raw material gas outlet portion. The oxidation reaction of propylene was carried out in the same manner as in Example 1 except that the catalyst charged in the catalyst was changed to 250 cm F3 catalyst. When the reaction temperature change test was conducted, the raw material conversion rate was 98.5%, and the total yield of acrolein and acrylic acid was 91.9% at the maximum. At this time, the reaction bath temperature was 335 ° C., the hot spot temperature of the catalyst layer on the gas inlet side was 418 ° C., and the hot spot temperature of the catalyst layer on the gas outlet side was 380 ° C. The magnitude relationship between these two hot spot temperatures was reversed when the raw material conversion rate was 98.2%. That is, Cmax−Ccrs = 0.3. When the reaction bath temperature was 326 ° C., the propylene conversion was 95.5%, the hot spot temperature of the catalyst layer on the gas inlet side was 358 ° C., and the hot spot temperature of the catalyst layer on the gas outlet side was 445 ° C. Compared with the comparative example, when the propylene conversion rate was greatly reduced, the hot spot temperature of the catalyst layer on the gas outlet side became extremely high.

  According to the present invention, acrolein and acrylic acid, or methacrolein and methacrylic acid can be produced in a high yield in a safe and stable manner.

  Although the invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

Claims (6)

Using a fixed bed multi-tubular reactor, at least one selected from propylene or isobutylene and tertiary butanol is subjected to gas phase catalytic oxidation with a gas containing molecular oxygen, and acrolein and acrylic acid, or In producing methacrolein and methacrylic acid,
A) A plurality of catalyst layers formed by N division (N is an integer of 2 or more) in the direction of the raw material gas flow in the reaction tube are provided, and the catalyst layer on the most reaction gas inlet side among the catalyst layers is Zin, The catalyst layer on the reaction gas outlet side is Zout,
B) Acrolein and acrylic acid or methacrolein and methacrylic are charged so that the activity of the catalyst charged in Zout is higher than the activity of the catalyst charged in Zin and satisfies the following formula (1): Acid production method.
0.5 ≦ Cmax−Ccrs Formula (1)
Cmax: Raw material conversion rate at which the yield of the desired product is maximized.
Ccrs: Raw material conversion rate when the maximum temperature of the catalyst layer Zin is Tin, the maximum temperature of the catalyst layer Zout is Tout, and the magnitude relationship between Tin and Tout is reversed when the raw material conversion rate is changed. The method for producing acrolein and acrylic acid or methacrolein and methacrylic acid according to claim 1, wherein 0.5 ≦ Cmax−Ccrs ≦ 10 is satisfied. The method for producing acrolein and acrylic acid or methacrolein and methacrylic acid according to claim 1, wherein 0.5 ≦ Cmax−Ccrs ≦ 5 is satisfied. The N is 3 or less, the firing temperature of the catalyst filled in Zin is set higher than the firing temperature of the catalyst filled in Zout, and Zin is filled with the mixture of the catalyst and the inert substance molding. The method for producing any one of acrolein and acrylic acid, or methacrolein and methacrylic acid. The method for producing acrolein and acrylic acid or methacrolein and methacrylic acid according to any one of claims 1 to 4, wherein the catalyst is a spherical supported catalyst obtained by supporting an active powder on an inert substance. The method for producing acrolein and acrylic acid, or methacrolein and methacrylic acid according to any one of claims 1 to 5, wherein the particle size of the catalyst filled in each catalyst layer is the same throughout all layers.