JP3139285B2 - Method for producing acrolein and acrylic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing acrolein and acrylic acid by subjecting propylene to gas-phase catalytic oxidation using molecular oxygen in a fixed-bed multitubular reactor.

[0002]

2. Description of the Related Art The technology for producing acrolein and acrylic acid from propylene by gas phase catalytic oxidation using a so-called molybdenum-bismuth composite oxide catalyst is well known.

[0003] This oxidation reaction is usually carried out using a fixed-bed multitubular reactor. However, since the reaction generates a large amount of heat, a hot spot tends to be generated particularly on the inlet side of the raw material gas. Therefore, there is a problem in that the yield is lowered and the catalyst life is shortened due to accelerated catalyst deterioration. This problem becomes more serious especially when the raw material propylene concentration is increased or the space velocity is increased in order to increase the productivity per unit catalyst.

Several proposals have been made in the past to reduce hot spots and improve productivity and catalyst life. For example, as disclosed in Japanese Patent Publication No. 57-30688, a method of diluting a catalyst in a portion where a hot spot easily occurs with a substance inert to the reaction. Similarly, JP-A-51-127003 discloses a method in which a so-called supported catalyst is placed on the inlet side of a raw material gas, and the outlet side is used as a normal molded catalyst.

[0005] Japanese Patent Publication No. 63-38331 discloses a plurality of types of molybdenum-bismuth based multi-component catalysts whose activities are controlled by changing the types or amounts of alkali metals and thallium group elements. A method has been proposed in which a catalyst is prepared and a catalyst having higher activity is disposed from the inlet side of the raw material gas toward the outlet side.

Further, Japanese Patent Application Laid-Open No. 3-294239 discloses that the activity is controlled by changing the kind or (and) amount of the alkaline earth metal in the components of the molybdenum-bismuth-based multi-way catalyst. As a method of disposing the catalyst, Japanese Patent Application Laid-Open No. H4-217932 discloses a method of controlling the activity by changing the size of the catalyst and disposing the catalyst in the same manner.

[0007]

As described above, when performing the present gas phase catalytic oxidation reaction using a fixed-bed multitubular reactor, the productivity is improved by suppressing the hot spot at the inlet of the raw material gas. As a method to extend the catalyst life,
A method has been adopted in which the catalyst activity is controlled by some method and the reaction tube is divided and filled. These are all effective methods, but the method using an inert diluent not only requires the operation of mixing the catalyst and the diluent in advance, but also reduces the amount of the catalyst component that can be filled in the reaction tube, Since the load per unit catalyst becomes large, this is not always an advantageous method from the viewpoint of catalyst life.

[0008] Compared to this, a method of controlling the activity by changing the catalyst composition is a more excellent method, but a plurality of catalysts having different compositions must be prepared. Since they may be different, the initial appropriate distribution of activity may be disrupted during long-term operation, making it difficult to continue the reaction. Also, a method of changing the size of the catalyst is that, even if the shape is devised and, for example, a ring-shaped catalyst is used, the yield of acrolein and acrylic acid decreases as the size of the catalyst increases if the shape is the same. This is not an advantageous method in terms of rate.

An object of the present invention is to produce propylene by gas-phase catalytic oxidation using a fixed-bed multitubular reactor to suppress a hot spot at a raw material gas inlet when producing acrolein and acrylic acid. Improve
It is to provide a simpler and more reliable method for extending the catalyst life.

[0010]

Means for Solving the Problems In order to solve the above problems, the present inventors have made intensive studies on a method for controlling the activity of a catalyst and maintaining a stable and high productivity over a long period of time. It has been found that the activity can be controlled by changing the calcination temperature of, and that the above-mentioned problem can be achieved by dividing and filling the reaction tube, thereby leading to the present invention.

The present invention is as follows. (1) General formula as _{catalyst, Mo a -Bi b -Fe c -A} d -B e -C f -D g -O
_x (Mo is molybdenum , Bi is bismuth , Fe is iron
Each represents, A represents nickel and / or cobalt, B is manganese, zinc, calcium, magnesium,
C represents at least one element selected from the group consisting of tin and lead, C represents at least one element selected from the group consisting of phosphorus, boron, arsenic, tellurium, tungsten, antimony and silicon, and D represents Represents at least one element selected from the group consisting of potassium, rubidium, cesium and thallium, and when a = 12 , 0
<B ≦ 10, 0 <c ≦ 10, 1 ≦ d ≦ 10, 0 ≦ e ≦ 1
0, 0 ≦ f ≦ 20, 0 <g ≦ 2, and x is a value determined according to the oxidation state of each element), using a fixed-bed multitubular reactor filled with a complex oxide represented by the following formula: In the method of producing acrolein and acrylic acid by gas-phase catalytic oxidation of molecular gas with molecular oxygen, each reaction tube is divided into a plurality of layers, and without substantially changing the catalyst composition between each layer, the raw material gas inlet side A process for producing acrolein and acrylic acid, which comprises sequentially charging a catalyst prepared by calcining at a higher temperature. (2) As a catalyst to be filled at least into the raw material gas inlet, a mixture obtained by mixing and forming the composite oxide described in the above item (1) and molybdenum oxide which is substantially inert in the present reaction is used. ) Described method.

Hereinafter, the present invention will be described in detail. The catalyst used in the present invention includes a general formula Moa-Bib-Fe known as a so-called multi-component composite oxide catalyst.
c-Ad-Be-Cf-Dg-Ox (Mo, Bi, Fe
Represents molybdenum, bismuth and iron, A represents nickel and / or cobalt, B represents at least one element selected from the group consisting of manganese, zinc, calcium, magnesium, tin and lead;
Is at least one selected from the group consisting of phosphorus, boron, arsenic, tellurium, tungsten, antimony and silicon.
D represents at least one element selected from the group consisting of potassium, rubidium, cesium and thallium, and when a = 12, 0 <b ≦ 10, 0
<C ≦ 10, 1 ≦ d ≦ 10, 0 ≦ e ≦ 10, 0 ≦ f ≦ 2
0, 0 <g ≦ 2, and x is a value determined by the oxidation state of each element).
7-27490, JP-B-47-32044, JP-B-47-32051, JP-B-47-42.
241.

Specifically, for example, a catalyst having the following composition (excluding oxygen atoms) is exemplified. Mo ₁₂ Bi _0.1-5 Fe _0.5-5 Co _5-10 Cs _0.01-1 Si
_0.1-20 Mo ₁₂ W _0.1-2 Bi _0.1-5 Fe _0.5-5 Co _5-10 Cs
_0.01-1 Si _0.1-20 Mo ₁₂ W _0.1-2 Bi _0.1-5 Fe _0.5-5 Co _5-10 K _0.01-1
Si _0.1-20 Mo ₁₂ Bi _0.1-5 Fe _0.5-5 Co _5-10 Tl _0.01-1 P
_{0.01-2 Si 0.1-20 Mo 12 Bi 0.1-5 Fe} 0.5-5 Ni 5-10 Tl 0.01-1 P
_0.01-2 Si _0.1-20

The method for preparing the catalyst used in the present invention except for the calcination temperature and the raw materials other than molybdenum oxide used for mixing and molding are not particularly limited.
Commonly used methods and raw materials can be employed. The shape of the catalyst is not particularly limited, and may be spherical,
It can be formed into a columnar shape, a cylindrical shape, or the like, and the molding method can be carrier molding, extrusion molding, tablet molding, or the like.

In the present invention, each reaction tube is divided into a plurality of regions, preferably two or three regions, and they are arranged so that the activity becomes higher from the inlet side to the outlet side of the raw material gas. Is mainly controlled by a simple method of arranging a catalyst in which the final calcination temperature of the catalyst is changed.
The catalyst of the present invention is usually formed in air or in an inert gas at a temperature of 400 ° C. to 600 ° C. after molding or before molding.
It is activated by calcining for ２０20 hours and used for the reaction. The preferred calcining temperature is determined by the composition of the catalyst, and conventionally, the reaction yield is determined to be the highest. It was found that the higher the temperature, the lower the activity but the higher the selectivity. Therefore, a conventional high-activity catalyst calcined at a relatively low temperature is used as a catalyst to be charged on the outlet side, and a catalyst having a lower activity is calcined at a higher temperature on the inlet side.

The firing time as a means for controlling the activity depends on the firing temperature but may be 2 hours or more, and can be appropriately determined within the above range. The catalyst calcined at a high temperature has a higher selectivity than the catalyst at the outlet, so that the reaction yield is higher than that obtained by the conventional dilution method, and the substantial use of the catalyst is advantageous in terms of the life of the catalyst.

The method for suppressing the activity of the catalyst used in the present invention is basically only at the calcination temperature, that is, for example,
The catalyst fired at 500 ° C., 480 ° C., and 450 ° C. is merely charged in order from the inlet side of the raw material gas toward the outlet side, and the composition of the catalyst is such that an inert diluent or molybdenum oxide mixed and molded is used. Do not change except. Catalysts whose activities have been changed by changing the type or amount of alkali metals, etc., have different behaviors of activity change over long-term operation.For example, a catalyst with a large amount of alkali metal filled at the entrance side is compared with a catalyst with a small amount of alkali metal at the exit side. There is a possibility that the activity decreases at a high rate, and a long-term operation reduces only the activity on the entrance side, and a new hot spot appears on the layer on the exit side.

On the other hand, in the case where the activity is controlled by the firing temperature, the behavior of the activity changes with time is basically the same, and such a problem hardly occurs. It has been found that the reason why the activity is decreased by increasing the calcination temperature is mainly due to the decrease in the specific surface area of the catalyst, and the specific surface area hardly changes depending on the reaction. Therefore, according to the present invention, the operation can be stably continued for a long time with high productivity.

By the way, even in a method of controlling the activity at the calcination temperature without changing the catalyst composition and dividing and packing the catalyst, deterioration of the catalyst cannot be avoided in a very long operation. The inventors of the present invention have previously proposed a method of suppressing the catalyst deterioration by coexisting molybdenum oxide which is substantially inactive in the present reaction with at least the catalyst on the inlet side of the raw material gas. (Japanese Patent Application 5-15
No. 4885)

[0020] In this method, the deterioration of the catalyst is mainly caused by volatilization of the molybdenum component at the entrance,
It has been found that it is necessary to coexist in the form of molybdenum oxide which is substantially inactive in the present reaction so as not to lower the reaction yield. Since molybdenum oxide itself is an inert diluent, it is argued that its use as an inlet diluent would be one of the methods to reduce the activity at the entrance side.
It is necessary to make モ 60% of molybdenum oxide coexist. On the other hand, in order to suppress deterioration, a relatively small amount of coexistence, for example, 2 to 20% is sufficient.

In the method of the present invention, the activity of the catalyst formed by mixing and molding a relatively small amount of molybdenum oxide is controlled by changing the calcination temperature, and by dividing and filling the catalyst, the objectives of suppressing hot spots and suppressing catalyst deterioration are achieved. It is assumed that. The catalyst formed by mixing and forming molybdenum oxide must be filled at least on the gas inlet side, but it may be coexisted in all layers or its concentration may be changed depending on the divided layers. Molybdenum oxide may be any substance that is substantially inert to the present reaction. For example, molybdenum oxide can be obtained by heat-treating commercially available ammonium molybdate at 550 ° C. to 700 ° C. in air. If the heat treatment temperature is lower than this, the olefin has a complete oxidation activity, and when it is coexisted with a catalyst, it causes a decrease in the selectivity of the reaction. Alternatively, a commercially available molybdenum trioxide that is inert to the reaction can be selected.

The conditions for the gas phase catalytic oxidation reaction of propylene with molecular oxygen can be carried out by a conventionally known method.
For example, the propylene concentration in the raw material gas is 3 to 15%, the ratio of molecular oxygen to propylene is 1 to 3, and the rest is nitrogen, steam, carbon oxide, propane, or the like. Air is advantageously used as a supply source of molecular oxygen, but if necessary, oxygen-enriched air or pure oxygen can be used, and a one-pass method or a recycling method is used. The reaction is performed at a reaction temperature of 250 ° C. to 450 ° C., a reaction pressure of normal pressure to 5 atm, and a space velocity of 500 to 3000 h ⁻¹ (STP).

[0023]

The present invention will be described in more detail with reference to the following examples. The conversion (%), selectivity (%), and yield (%) in this specification are defined as follows. Conversion (%) = (moles of propylene reacted / moles of propylene supplied) × 100 Selectivity (%) = (moles of product / propylene reacted)
Number of moles) × 100 Yield (%) = (Mole number of product / Mole number of supplied propylene) × 100

Example 1 [Preparation of catalyst] Ammonium molybdate [(NH ₄ ) ₆
Hot water Mo ₇ O ₂₄ · 4H ₂ O] 11500g 37.6L
And 20% silica sol (SiO ₂ ) 163
Add 0 g, and use this solution A. Cobalt nitrate [Co
_{(NO 3) 2 · 6H 2} O ] 11080g and ferric nitrate _{[Fe (NO 3) 3 · 9H} 2 O ] 4400g and cesium nitrate (CsNO ₃₎ was dissolved 53g of warm water 20L, the At the B solution . 60% nitric acid 75 in 3.2L of pure water
0 g, and add bismuth nitrate [Bi (NO ₃ ) ₃ .5H ₂
O] 2640 kg was dissolved, and this was designated as solution C. Then B
Mix liquid and liquid C.

While stirring the solution A, a mixed solution of the solution B and the solution C is added to obtain a slurry. This is concentrated and dried, and then subjected to salt decomposition at 200 to 250 ° C. in an air stream. Then crush and 5
Extruded into a cylinder of mmφ × 2mmφ × 6mmH, 46
It was calcined at 0 ° C. for 6 hours to obtain catalyst A. The catalyst composition excluding oxygen is Mo ₁₂ Bi ₁ Fe ₂ Co ₇ Cs _0.05 Si ₁ .

A catalyst obtained by performing only the final calcination of this catalyst at 490 ° C. for 6 hours is referred to as catalyst B. [Reaction] A reaction tube having an inner diameter of 30 mmφ × 6000 mm was charged with 1.15 L of catalyst B and then 2.3 L of catalyst A as a catalyst on the raw material gas inlet side, and started at a salt bath temperature of 325 ° C. : Nitrogen: Steam = 1: 8: 3:
At a molar ratio of 1.5, SV = 1300 h ^-1 , inlet pressure 2.8
The reaction was performed under the conditions of atm. Table 1 shows the results.

Comparative Example 1 The catalyst A prepared in Example 1 was diluted and charged. That is, 0.8 L of catalyst A and 0.35 L of magnetic Raschig ring were mixed and charged into the raw material gas inlet side in the same manner as in Example 1, and 2.3 L of catalyst A was charged into the outlet side in the same manner as in Example 1. went. Table 2 shows the results. Comparative Example 1 has a larger decrease in the overall yield of acrolein and acrylic acid.

[0028]

[Table 1]

[0029]

[Table 2]

Comparative Example 2 In the same manner as in the catalyst A of Example 1, only the amount of the raw material cesium nitrate was changed, and the catalyst composition excluding oxygen was changed to Mo ₁₂ Bi ₁ Fe _2.
A catalyst C of Co ₇ Cs _0.3 Si ₁ was prepared. Similarly, 1.15 L of the catalyst C was charged at the inlet side of the raw material gas, and 2.3 L of the catalyst A was charged at the outlet side, and the reaction was carried out in the same manner as in Example 1. Table 3 shows the results.

The activity of the catalyst C layer on the entrance side is significantly reduced,
It is necessary to increase the salt bath temperature at a fast rate. After 250 days, the temperature of the hot spot in this layer had dropped, but the second hot spot in the catalyst A layer had risen and the temperature had been reversed. There is a high possibility that it cannot withstand long-term operation as compared with the first embodiment.

[0032]

[Table 3]

[0033] Example 2 Ammonium molybdate _{(NH 4) 6 Mo 7 O} 24 · 4
H ₂ O was calcined in air at 630 ° C. for 3 hours to obtain MoO ₃ . Catalyst precursor powder 90 after salt decomposition obtained in Example 1
And 10 parts of this MoO ₃ were mixed and extruded into the same shape. This was calcined at 490 ° C. for 6 hours to obtain catalyst D. 1.15 L of this catalyst D was charged on the gas inlet side, and 2.3 L of catalyst A was charged on the outlet side, and a reaction was carried out in the same manner as in Example 1. Table 4 shows the results. The change in the salt bath temperature was very slight, and no reduction in the reaction yield was observed.

[0034]

[Table 4]

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C07C 57/05 C07C 57/05 // C07B 61/00 300 C07B 61/00 300 (72) Inventor Yasuo Ito 5th Sokai-cho, Niihama-shi, Ehime No. 1 Sumitomo Kagaku Kogyo Co., Ltd. (56) References JP-A-3-294238 (JP, A) JP-A-4-217932 (JP, A) JP-A-5-317714 (JP, A) JP-A Sho 61-221149 (JP, A) JP-A-64-56634 (JP, A) JP-A-51-227013 (JP, A) JP-B-53-30688 (JP, B2) JP-B-43-24403 (JP, A) B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07C 27/00 340 B01J 23/88 C07C 45/35 C07C 47/22 C07C 51/25 C07C 57/05 C07B 61/00 300

Claims (2)

(57) [Claims] 1. A general formula as _{catalyst, Mo a -Bi b -Fe c -A} d -B e -C f -D g -O
_x (Mo is molybdenum , Bi is bismuth , Fe is iron
Each represents, A represents nickel and / or cobalt, B is manganese, zinc, calcium, magnesium,
C represents at least one element selected from the group consisting of tin and lead, C represents at least one element selected from the group consisting of phosphorus, boron, arsenic, tellurium, tungsten, antimony and silicon, and D represents Represents at least one element selected from the group consisting of potassium, rubidium, cesium and thallium, and when a = 12 , 0
<B ≦ 10, 0 <c ≦ 10, 1 ≦ d ≦ 10, 0 ≦ e ≦ 1
0, 0 ≦ f ≦ 20, 0 <g ≦ 2, and x is a value determined according to the oxidation state of each element), using a fixed-bed multitubular reactor filled with a complex oxide represented by the following formula: In the method of producing acrolein and acrylic acid by gas-phase catalytic oxidation of molecular gas with molecular oxygen, each reaction tube is divided into a plurality of layers, and without substantially changing the catalyst composition between each layer, the raw material gas inlet side A process for producing acrolein and acrylic acid, which comprises sequentially charging a catalyst prepared by calcining at a higher temperature. 2. A catalyst which is formed by mixing and molding the composite oxide according to claim 1 and molybdenum oxide which is substantially inert in itself in the present reaction, as a catalyst to be filled at least into a raw material gas inlet. The method of claim 1.