JP2005162744A - Method for producing unsaturated aldehyde and unsaturated carboxylic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an unsaturated aldehyde and an unsaturated carboxylic acid, capable of stably producing the aldehyde and the acid corresponding to a raw material olefin for a long period in a high yield, by catalytically oxidizing the olefin in a gaseous phase with molecular oxygen or a molecular oxygen-containing gas. <P>SOLUTION: This method comprises (A) using two or more kinds of complex oxides comprising Mo, Bi, and Si-based complex oxides and having ratios of Si contents to Mo contents different from each other as catalysts, (B) dividing a reactor in the direction of a tube axis of the reactor and arranging a plurality of reaction zones used for being filled with the catalysts, and (C) filling the plurality of reaction zones with two or more of the catalysts comprising the complex oxides in such a manner that the ratios of the Si contents to the Mo contents in the catalysts are gradually increased in the direction from the inlet of a raw material gas to the outlet of the gas. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a process for producing a corresponding unsaturated aldehyde and unsaturated carboxylic acid by vapor phase catalytic oxidation of olefin with molecular oxygen or a molecular oxygen-containing gas and stably for a long period of time in a high yield.

  Olefin such as propylene and isobutylene is subjected to gas phase catalytic oxidation with molecular oxygen in the presence of a complex oxide catalyst, and the corresponding unsaturated aldehyde such as acrolein and methacrolein and unsaturated carboxylic acid such as acrylic acid and methacrylic acid. Many proposals have been made on the method for producing acids, and some of them have already been industrially implemented.

  This production reaction is carried out using a fixed-bed multitubular reactor. However, due to the reaction with a large exotherm, a hot spot (abnormally high temperature part) tends to be generated particularly on the raw material gas inlet side, and therefore excessive oxidation occurs. There arises a problem that the yield of the reaction is reduced and the catalyst life is reduced due to acceleration of catalyst deterioration. In particular, this problem is further increased if the olefin concentration of the raw material is increased or the space velocity is increased in order to increase the production amount per unit catalyst. As a result, it has been practically difficult to produce the corresponding unsaturated aldehydes and unsaturated carboxylic acids stably over a long period of time and in high yields.

  Conventionally, production methods for suppressing the hot spots and improving productivity and catalyst life have been proposed. For example, Patent Document 1 discloses a fixed bed tubular reaction in which a catalyst in which the amount of Bi and Fe in a complex oxide catalyst is changed is packed so that the amount of Bi and Fe decreases from the raw material gas inlet toward the outlet. A method of reacting using a vessel is disclosed.

  Further, in Patent Document 2, a plurality of catalysts having different activities with different types and / or amounts of alkaline earth elements contained therein are prepared, and the catalyst layers in each reaction tube are divided into 2 in the tube axis direction. A method is disclosed in which a reaction is performed using a fixed bed tubular reactor in which a plurality of reaction zones divided into layers or more are packed so that the catalytic activity increases from the inlet to the outlet of the raw material gas.

  Furthermore, in Patent Document 3 and Patent Document 4, a plurality of catalysts having different calcination temperatures are prepared without substantially changing the catalyst composition, and two or more catalyst layers in each reaction tube are arranged in the tube axis direction. There is disclosed a method of reacting a plurality of reaction zones divided into a plurality of reaction zones using a fixed bed tubular reactor filled with a catalyst prepared by firing at a higher temperature toward the inlet side of the raw material gas.

However, according to these conventional techniques, although the effect is obtained as it is, it is not always satisfactory, and a new method for sufficiently solving the problem caused by the hot spot is required.
JP 2001-48817 A Japanese Patent No. 2809476 JP-A-10-168003 Japanese Patent No. 3139285

  In view of the prior art as described above, the object of the present invention is to solve the problem caused by hot spots in the case of vapor phase oxidation of olefins, particularly propylene, in the presence of a Mo-Bi composite oxide catalyst. It is an object of the present invention to provide a method for producing unsaturated aldehydes, particularly acrolein and unsaturated carboxylic acids, particularly acrylic acid, in a stable and high yield for a long period of time.

  As a result of diligent research to solve the above-mentioned problems, the present inventor is a Mo-Bi composite oxide catalyst having a specific composition, and a plurality of types of catalysts having different Si contents relative to Mo in the component. And providing a plurality of reaction zones for dividing the fixed bed tubular reaction tube and filling the catalyst, and for each of these plurality of reaction zones, It has been found that the above problem can be solved by adopting a new method of using a reactor filled with a catalyst.

That is, the present invention has the following gist.
(1) In a method for producing an unsaturated aldehyde and an unsaturated carboxylic acid by vapor-phase catalytic oxidation of an olefin with molecular oxygen or a molecular oxygen-containing gas using a fixed bed tubular reactor,
(A) As a catalyst, the following formula (1)
MoaBibCocNidFeeXfYgZhQiSijOk (1)
(Wherein X represents at least one element selected from the group consisting of Na, K, Rb, Cs and Tl; Y represents at least one element selected from the group consisting of B, P, As and W) Represents an element, Z represents at least one element selected from the group consisting of Mg, Ca, Zn, Ce and Sm, Q represents a halogen atom, a to k represent an atomic ratio of each element, When a = 12, 0.5 ≦ b ≦ 7, 0 ≦ c ≦ 10, 0 ≦ d ≦ 10, 0 ≦ c + d ≦ 10, 0.05 ≦ e ≦ 3, 0.0005 ≦ f ≦ 3, 0 ≦ (g ≦ 3, 0 ≦ h ≦ 1, 0 ≦ i ≦ 0.5, 0 ≦ j ≦ 40, and k is a numerical value that satisfies the oxidation state of other elements.)
And two or more complex oxide catalysts having different atomic ratios of Si to Mo
(B) providing a plurality of reaction zones in which the reactor is divided in the tube axis direction and filled with a catalyst;
(C) Filling each of the plurality of reaction zones with the two or more composite oxide catalysts so that the atomic ratio of Si to Mo increases from the source gas inlet toward the outlet. A method for producing saturated aldehydes and unsaturated carboxylic acids.
(2) When the atomic ratio of Si to Mo of the catalyst on the source gas inlet side is 1, two or more kinds of composites so that the atomic ratio of Si to Mo of the catalyst on the gas outlet side is greater than 1 and 10 or less The production method according to the above (1), wherein the oxide catalyst is filled.
(3) The manufacturing method as described in said (1) or (2) whose number of reaction zones is 2-4.
(4) The production method according to any one of (1) to (3), wherein the olefin is propylene, and the unsaturated aldehyde and the unsaturated carboxylic acid are acrolein and acrylic acid, respectively.

  According to the method of the present invention, the generation of by-products due to runaway reaction and excessive oxidation reaction associated with the occurrence of hot spots is suppressed, and the target unsaturated aldehyde and unsaturated carboxylic acid are obtained with high selectivity and high yield. Can be manufactured. Furthermore, deterioration of the catalyst due to heat load is prevented, and the catalyst can be used stably for a long time, so that productivity can be greatly improved.

  The reason why the above-described excellent effect is achieved by the present invention is not necessarily clear, but is estimated as follows.

  The molybdenum-bismuth complex oxide catalyst used in the present invention is a catalyst represented by the above formula (1).

  In the present invention, two or more types of catalysts having different composition ratios of Si with respect to Mo are used. In this case, when the atomic ratio of Mo is 12, different catalysts are used in the range of Si of 0 to 40, preferably 0.5 to 30. And in this invention, when the atomic ratio of Si with respect to Mo of the catalyst in which the atomic ratio of Si with respect to Mo differs, for example, the catalyst of the raw material gas inlet side is set to 1, the atomic ratio of Si with respect to Mo of the catalyst of the gas outlet side is Preferably, two or more different catalysts are used in the range of 1 to 10, particularly preferably 2 to 5.

  On the other hand, in the present invention, two or more reaction zones are provided by dividing the catalyst layer of the reactor of the fixed bed tubular reactor into two or more layers in the tube axis direction. The division of the reactor becomes easier as the number of divisions increases, so that suppression of hot spots is facilitated, but the division is usually preferably performed so as to form reaction zones of 2 to 4, preferably 2 or 3. The number of reaction tubes to be used, the length to be filled with the catalyst, and the diameter of the reaction tube vary depending on operating conditions and production capacity, and are appropriately determined.

  In the present invention, two or more types of catalysts having different atomic ratios of Si to Mo described above are mixed in the catalyst from the raw material gas inlet to the outlet with respect to the reaction zone of the two or more divided reactors. It fills so that content ratio of Si with respect to Mo may become large. For example, when two reaction zones are provided by dividing the reactor, two types of catalysts having different atomic ratios of Si to Mo are prepared, and a reaction zone on the raw material gas inlet side (hereinafter referred to as a pre-stage reaction zone). The catalyst is packed so that the atomic ratio of Si to Mo of the catalyst packed in the outlet side reaction zone (hereinafter referred to as the subsequent reaction zone) is larger than the atomic ratio of Si to Mo of the catalyst packed in the catalyst. Is done. That is, a catalyst having a relatively small atomic ratio of Si to Mo is filled in the former reaction zone, and a catalyst having a relatively large atomic ratio of Si to Mo as compared to the preceding reaction zone is filled in the latter reaction zone.

  In the present invention, when two or more kinds of catalysts having different atomic ratios of Si to Mo with respect to a plurality of reaction zones are filled from the raw material gas inlet to the outlet, the atomic ratio of Si to Mo of the catalyst on the raw material gas inlet side Is set to 1, the atomic ratio of Si to Mo of the catalyst on the gas outlet side is preferably larger than 1, particularly preferably 2 or more, and preferably 10 or less, particularly preferably 5 or less. It is preferable to do this. When the atomic ratio of Si to Mo of the catalyst on the source gas outlet side is larger than 10 on the catalyst on the source gas inlet side, the difference in activity between the inlet side and the outlet side is not preferable.

  In the present invention, the shape, size, etc. of the catalyst charged in each reaction zone are not particularly limited, and can be appropriately selected from known shapes, sizes, etc. For example, the shape may be any of a spherical shape, a cylindrical shape, a ring shape, and the like.

  The method for preparing the catalyst used in the present invention is not particularly limited. Usually, the required amount of the raw material compound containing each element component is appropriately dissolved or dispersed in an aqueous medium, heated and stirred, and then evaporated to dryness. Manufactured by drying and grinding. As the raw material of each component, nitrates, ammonium salts, hydroxides, oxides, acetates of the respective elements are used. The obtained powdery catalyst is usually preferably molded into the above-described arbitrary shape by a molding method such as extrusion molding or granulation molding. At this time, in order to improve the strength and the degree of pulverization of the catalyst, generally known inorganic fibers such as glass fibers, various whiskers and the like may be added. In order to control the physical properties of the catalyst with good reproducibility, additives generally known as binders such as ammonium nitrate, cellulose, starch, polyvinyl alcohol and stearic acid can also be used.

  In the present invention, the composite oxide represented by the formula (I) can be used alone, but alumina, silica, silica-alumina, silicon carbide, titanium oxide, magnesium oxide, aluminum sponge, silica- It may be used by supporting it on a carrier generally known as an inert carrier such as titania. In this case as well, the above-mentioned inorganic fibers may be added to improve the strength of the catalyst, and a binder such as ammonium nitrate may be used in order to control the physical properties of the catalyst with good reproducibility. it can. These compacts or carriers are fired, for example, at a temperature of 300 to 600 ° C. for about 1 to 10 hours under air flow.

The gas phase catalytic oxidation reaction using molecular oxygen or molecular oxygen-containing gas of the present invention may be a single flow method or a recycling method through a reaction tube, and the conditions generally used for this kind of reaction. Can be implemented below. For example, a mixed gas composed of 1 to 15% by volume of propylene, 3 to 30% by volume of molecular oxygen, 0 to 60% by volume of water vapor, 20 to 80% by volume of an inert gas such as nitrogen or carbon dioxide, The catalyst layer filled in each reaction zone of each 15-50 mm reaction tube is introduced at a space velocity (SV) of 300-5000 hr ⁻¹ under a pressure of 250-450 ° C. and 0.1-1 MPa. However, in the present invention, it is possible to operate under high load reaction conditions, for example, higher raw material concentration or high space velocity conditions in order to increase productivity.

EXAMPLES The present invention will be described in more detail below with reference to examples of the present invention, but the present invention should not be construed as being limited to such examples. In the following, Example 1 is an example of the present invention, and Examples 2 to 4 are comparative examples. The conversion rate, selectivity, and yield in each example are calculated by the following equations.
Conversion (mol%) = (number of moles of reacted propylene / number of moles of supplied propylene) × 100
Selectivity (mol%) = (mol number of produced acrolein + mol number of produced acrylic acid) / mol number of reacted propylene × 100
Yield (mol%) = (number of moles of produced acrolein + number of moles of produced acrylic acid) / number of moles of supplied propylene × 100

Example 1
(Preparation of catalyst 1)
105.5 g of ammonium paramolybdate was dissolved in 500 ml of heated pure water. Next, 10.1 g of ferric nitrate and 97.0 g of cobalt nitrate were dissolved in 100 ml of heated pure water. These solutions were gradually mixed with thorough stirring.

Next, 0.96 g of borax and 0.51 g of potassium nitrate are dissolved in 40 ml of pure water under heating, and added to the slurry. Next, 72.9 g of silica was added and stirred thoroughly. Subsequently, a solution in which 2.7 ml of nitric acid was dissolved in 20 ml of pure water was added, and 24.1 g of bismuth nitrate was further added, followed by stirring and mixing.
The slurry was heat-dried and then subjected to a heat treatment at 300 ° C./1 hour in an air atmosphere.
The obtained granular solid was pulverized and formed into tablets having a diameter of 5 mm and a height of 4 mm with a tableting machine.

Next, the tablet-molded product was put into a firing container, heated to 510 ° C. over 3 hours while circulating a small amount of air, and fired at that temperature for 4 hours to produce a composite oxide catalyst.
The catalyst calculated from the charged raw materials is a complex oxide having the following atomic ratio.
Mo: Bi: Co: Fe: Na: B: K: Si = 12: 1: 6.6: 0.6: 0.1: 0.2: 0.1: 24

(Preparation of catalyst 2)
105.5 g of ammonium paramolybdate was dissolved in 500 ml of heated pure water. Next, 10.1 g of ferric nitrate and 97.0 g of cobalt nitrate were dissolved in 100 ml of heated pure water. These solutions were gradually mixed with thorough stirring.
Next, 0.96 g of borax and 0.51 g of potassium nitrate were dissolved in 40 ml of pure water under heating, and added to the slurry. Next, 15.0 g of silica was added and stirred thoroughly.
Subsequently, a solution in which 2.7 ml of nitric acid was dissolved in 20 ml of pure water was added, and 24.1 g of bismuth nitrate was further added, followed by stirring and mixing.
The slurry was heat-dried and then subjected to a heat treatment at 300 ° C./1 hour in an air atmosphere.
The obtained granular solid was pulverized and formed into a tablet having a diameter of 5 mm and a height of 4 mm with a tableting machine.

Next, the tablet-molded product was put into a firing container, heated to 510 ° C. over 3 hours while circulating a small amount of air, and fired at that temperature for 4 hours to produce a composite oxide catalyst.
The catalyst calculated from the charged raw materials is a complex oxide having the following atomic ratio.
Mo: Bi: Co: Fe: Na: B: K: Si = 12: 1: 6.6: 0.6: 0.1: 0.2: 0.1: 5
(Oxidation reaction) 500 ml of the catalyst 2 was filled on the raw material gas inlet side of a stainless steel reaction tube having a diameter of 25 mm provided with a thermocouple, and 1000 ml of the catalyst 1 was filled on the raw material gas outlet side. A mixed gas of 8% by volume of propylene, 67% by volume of air, and 25% by volume of water vapor was introduced at SV1800hr- ¹ from the reaction tube inlet, and the reaction was continued for 1,000 hours. Table 1 shows the initial reaction performance and the performance after 1,000 hours.

Example 2
In Example 1, the reaction was performed in the same manner as in Example 1 except that only 1500 ml of Catalyst 1 was used. Table 1 shows the initial reaction performance and the performance after 1,000 hours.

Example 3
In Example 1, the reaction was performed in the same manner as in Example 1 except that only 1500 ml of catalyst 2 was used. Table 1 shows the initial reaction performance and the performance after 1,000 hours.

  The production method of the present invention comprises gas-phase catalytic oxidation of olefins, particularly propylene, with molecular oxygen or molecular oxygen-containing gas, and the corresponding unsaturated aldehydes, particularly acrolein and unsaturated, corresponding to long-term stable and high yields. It can be widely used to produce carboxylic acids, especially acrylic acid. The produced unsaturated aldehydes and unsaturated carboxylic acids are used in a wide range of applications as intermediate raw materials for chemicals.

Claims (4)

In a method for producing unsaturated aldehydes and unsaturated carboxylic acids by gas-phase catalytic oxidation of olefins with molecular oxygen or a molecular oxygen-containing gas using a fixed bed tubular reactor packed with a catalyst,
(A) As a catalyst, the following formula (1)
MoaBibCocNidFeeXfYgZhQiSijOk (1)
(Wherein X represents at least one element selected from the group consisting of Na, K, Rb, Cs and Tl; Y represents at least one element selected from the group consisting of B, P, As and W) Z represents an element, Z represents at least one element selected from the group consisting of Mg, Ca, Zn, Ce and Sm, Q represents a halogen atom, and a to k represent the atomic ratio of each element. And when a = 12, 0.5 ≦ b ≦ 7, 0 ≦ c ≦ 10, 0 ≦ d ≦ 10, 0 ≦ c + d ≦ 10, 0.05 ≦ e ≦ 3, 0.0005 ≦ f ≦ 3, (0 ≦ g ≦ 3, 0 ≦ h ≦ 1, 0 ≦ i ≦ 0.5, 0 ≦ j ≦ 40, and k is a numerical value that satisfies the oxidation state of other elements.)
And two or more complex oxide catalysts having different atomic ratios of Si to Mo
(B) Dividing the reactor in the direction of the tube axis and providing a plurality of reaction zones filled with catalyst,
(C) Filling each of the plurality of reaction zones with the two or more composite oxide catalysts so that the atomic ratio of Si to Mo increases from the source gas inlet toward the outlet. A method for producing saturated aldehydes and unsaturated carboxylic acids.   Two or more complex oxide catalysts so that the atomic ratio of Si to Mo of the catalyst on the gas outlet side is 1 and the atomic ratio of Si to Mo of the catalyst on the gas outlet side is greater than 1 and 10 or less The manufacturing method of Claim 1 filled with.   The production method according to claim 1 or 2, wherein the number of reaction zones is 2 to 4.   The production method according to any one of claims 1 to 3, wherein the olefin is propylene, and the unsaturated aldehyde and the unsaturated carboxylic acid are acrolein and acrylic acid, respectively.