JPH08157414A - Catalyst for methacrylic acid production and production of methacrylic acid - Google Patents

Abstract

PURPOSE: To obtain a catalyst for the production of methacrylic acid by mixing a solution containing Mo, V, P and a specific element with a solution containing Mo and Si, a solution containing another specific element and optionally ammonia and drying the mixture. CONSTITUTION: A solution or slurry containing a catalyst precursor is produced by mixing a homogeneous solution containing Mo, V, P and X (X is Sb, Cu, Co, Bi or As) with a homogeneous solution containing Mo and Si as essential components, a homogeneous solution containing Y (Y is K, Rb, Cs or Tl) and optionally ammonia. The objective catalyst having a composition expressed by formula (b:0.1-2, c:1-3, d:0.05-0.5, e=0.01-3, f:0.1-3 and f+g=2-6 when a=12; h is number of O atoms) is obtained by drying the mixture. The catalyst is usable for the production of methacrylic acid by the vapor-phase catalytic oxidation of methacrolein with molecular oxygen. It has excellent catalytic activity, selectivity to methacrylic acid and catalytic stability.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a catalyst used in the vapor phase catalytic oxidation of methacrolein with molecular oxygen to produce methacrylic acid, a method for producing the same, and the molecular weight of methacrolein in the presence of this catalyst. TECHNICAL FIELD The present invention relates to a method for producing methacrylic acid, which comprises performing a vapor-phase catalytic oxidation with gaseous oxygen.

[0002]

2. Description of the Related Art Many proposals have hitherto been made regarding catalysts used for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein using molecular oxygen.
Catalysts having industrially usable properties are almost limited to heteropolyacids containing phosphorus (P) and molybdenum (Mo) as essential components, and conventional techniques relating to these are described in, for example, Kato, J. Kagaku, Vol. 28, 560. -564 (1986). Above all, in addition to P and Mo, vanadium (V)
The catalyst containing s has excellent methacrylic acid selectivity, and its improvement is being promoted. However, the catalytic activity, methacrylic acid selectivity, catalyst stability, catalyst life, etc. are not always satisfactory, and further improvements have been desired.

Attempts have been made to improve the catalytic performance by adding silicon (Si) to a heteropolyacid catalyst containing P, Mo and V as essential components. Japanese Unexamined Patent Publication (Kokai) No. 53-90214 is characterized in that methacrolein is subjected to vapor phase catalytic oxidation of methacrolein with molecular oxygen in the presence of a catalyst containing a heteropolyacid containing P, Mo and V and an oxide of Si. A method of making an acid is disclosed. Here, Si is not an essential component but an optional additive component. Although a method for producing a catalyst containing Si is not specifically described, a potassium, cesium or thallium salt of a heteropolyacid containing P, Mo and V is prepared from the general description of the catalyst production method in the specification. After that, the oxide of Si is added, or the salt of the heteropoly acid is prepared by adding the compound of potassium, cesium or thallium after adding the oxide of Si to the solution of the heteropoly acid containing P, Mo and V. It is thought that it is manufactured by the method.
JP-A-61-76436 and JP-A-63-11253
5 discloses a catalyst in which Si is added as an optional additional component to a heteropolyacid catalyst containing P, Mo and V. In the examples, a method of heating and refluxing an aqueous solution containing P, Mo, V and an additional element to prepare a catalyst is shown.
According to the knowledge of the present inventors, the catalysts prepared by these methods do not exhibit the effect of Si addition sufficiently, and the catalyst performance such as activity and methacrylic acid selectivity is low.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for preparing a catalyst which is excellent in catalytic activity, methacrylic acid selectivity and catalyst stability.

[0005]

The present invention is based on the general formula (Mo) _a (V) _b (P) _c (Si) _d (X) _e (Y) _f (N
H ₄ ) _g (O) _h (In the formula, X is one or more elements selected from the group consisting of Sb, Cu, Co, Bi and As, and Y is K, Rb,
One or more elements selected from the group consisting of Cs and Tl, where a, b, c, d, e, f and g represent the atomic ratio of each element, and when a = 12, b = 0. 1-2, c = 1
-3, d = 0.05-0.5, e = 0.01-3, f =
0.1 to 3, f + g = 2 to 6, and h is the number of oxygen atoms required to satisfy the valence of each component. ) In producing a catalyst having a composition represented by the following, a homogeneous solution containing catalyst component elements Mo, V, P and X,
A homogeneous solution containing Mo and Si which are the catalyst component elements as essential components, and a homogeneous solution containing Y which is the catalyst component element,
If necessary, a solution or slurry containing a catalyst precursor is produced by mixing with ammonia, and the solution or slurry is dried. Methacrolein is subjected to vapor phase catalytic oxidation with molecular oxygen to produce methacrylic acid. It is a manufacturing method of a catalyst for manufacturing.

Further, the present invention has the general formula (Mo) _a (V) _b (P) _c (Si) _d (X) _e (Y) _f (N
H ₄ ) _g (O) _h (In the formula, X is one or more elements selected from the group consisting of Sb, Cu, Co, Bi and As, and Y is K, Rb,
One or more elements selected from the group consisting of Cs and Tl, where a, b, c, d, e, f and g represent the atomic ratio of each element, and when a = 12, b = 0. 1-2, c = 1
-3, d = 0.05-0.5, e = 0.01-3, f =
0.1 to 3, f + g = 2 to 6, and h is the number of oxygen atoms required to satisfy the valence of each component. ), A homogeneous solution containing the catalyst component elements Mo, V, P and X, a homogeneous solution containing the catalyst component elements Mo and Si as essential components, and a catalyst component element. Methacrolein prepared by preparing a solution or slurry containing a catalyst precursor by mixing a certain homogeneous solution containing Y and ammonia if necessary, and drying the solution or slurry. Is a catalyst for producing methacrylic acid by vapor-phase catalytic oxidation of ethylene with molecular oxygen.

Furthermore, the present invention provides the general formula (Mo) _a (V) _b (P) _c (Si) _d (X) _e (Y) _f (N
H ₄ ) _g (O) _h (In the formula, X is one or more elements selected from the group consisting of Sb, Cu, Co, Bi and As, and Y is K, Rb,
One or more elements selected from the group consisting of Cs and Tl, where a, b, c, d, e, f and g represent the atomic ratio of each element, and when a = 12, b = 0. 1-2, c = 1
-3, d = 0.05-0.5, e = 0.01-3, f =
0.1 to 3, f + g = 2 to 6, and h is the number of oxygen atoms required to satisfy the valence of each component. ), A homogeneous solution containing the catalyst component elements Mo, V, P and X, a homogeneous solution containing the catalyst component elements Mo and Si as essential components, and a catalyst component element. Existence of a catalyst characterized in that a solution or slurry containing a catalyst precursor is produced by mixing a certain homogeneous solution containing Y and ammonia, if necessary, and the solution or slurry is dried. Below is a method for producing methacrylic acid, which comprises subjecting methacrolein to gas-phase catalytic oxidation with molecular oxygen.

In the present invention, a compound that is decomposed into an oxide form during the catalyst preparation process is preferably used as a raw material for preparing the catalyst. Examples of such compounds are eg nitrates,
Organic acid salts, hydroxides, oxides, carbonates and the like. However, as the Si source, a heteropoly acid containing Si or a Si compound capable of forming a heteropoly acid by mixing with a Mo compound must be used.
S capable of forming a heteropolyacid by mixing with a Mo compound
Examples of the i compound include silica sol, silica gel, sodium silicate and the like.

The catalyst of the present invention contains, in addition to Mo, V, P and Si, one or more elements selected from the group consisting of Sb, Cu, Co, Bi and As as essential components. These elements have the effect of suppressing complete oxidation and increasing the selectivity of methacrylic acid, but when Cu is used, the methacrylic acid selectivity is remarkably improved.

The catalyst used in the present invention is Mo, V, P.
And a homogeneous solution containing X, and Mo which is a catalyst component element
And a homogeneous solution containing Si as an essential component, a homogeneous solution containing Y as a catalyst component element, and, if necessary, ammonia to prepare a solution or a slurry containing a catalyst precursor. It is manufactured by drying. The homogeneous solution containing Mo, V, P and X and the homogeneous solution containing Mo and Si as essential components are preferably heteropolyacid solutions.

A homogeneous solution of a heteropolyacid containing Mo, V, P and X can be obtained, for example, by mixing the compounds of Mo, V and X in an aqueous solution of phosphoric acid and heating under reflux. The heating / refluxing time is appropriately selected within the range of 0.5 to 50 hours. If the heating / refluxing time is too short, the heteropolyacid is not produced, and it is meaningless to unnecessarily extend the heating / refluxing time after the production of the heteropolyacid is completed.

An example of a heteropolyacid containing Mo and Si as essential components is silicomolybdic acid or silicomolybdic acid in which a part of Mo atoms is replaced with another element, for example, V. Commercially available silicomolybdic acid may be used as it is or may be synthesized by a known method. It is a preferable method from the viewpoint of raw material cost to remove the sodium ion of sodium silicomolybdate with an ion exchange resin or the like to obtain a silicomolybdic acid solution. In this case, if the amount of sodium remaining in silicomolybdic acid is large, complete combustion is likely to proceed during the methacrylic acid synthesis reaction, and the selectivity of methacrylic acid decreases. Therefore, the Na / Si atomic ratio in the heteropolyacid containing Mo and Si as essential components must be suppressed to 0.1 or less.

The mixing of the homogeneous solution containing Mo, V, P and X with the homogeneous solution containing Mo and Si which are the catalytic component elements as essential components is 0 ° C to 60 ° C, preferably 0 ° C to 5 ° C.
It is carried out at a temperature of 0 ° C, most preferably 0 ° C to 40 ° C.
At this time, the solution obtained by mixing is preferably a homogeneous solution. If the mixing temperature is too high, the methacrylic acid selectivity of the catalyst tends to decrease. Without limiting the scope of the invention, if the mixing temperature is too high, Mo and S
Since the structure of the heteropolyacid in a homogeneous solution containing i as an essential component begins to break, it is considered that the catalyst performance is not sufficient when used as a catalyst. That is, in the present invention, Si
Is added as a part of the heteropolyacid without destroying its structure, so that Si is added even in the prepared catalyst.
Is present as a part of the skeleton of the heteropolyacid, and is considered to exert unprecedented catalytic performance.

In the prior art, for example, Japanese Patent Laid-Open No. Sho 53-53.
-90214, JP-A-61-76436, JP-A-63-
Examples of catalysts containing Si are listed in 112535, but in any case, Si is not an essential component, and it is not a condition that Si is contained as a part of the heteropolyacid structure. It is hard to say that excellent catalytic performance has been achieved.

In the mixing of a homogeneous solution containing Mo, V, P and the above X with a homogeneous solution containing Mo and Si which are catalytic component elements as essential components, the final pH at the time of mixing is preferably 4 or less. When the pH is 4 or less, the heteropolyacid structure is kept stable, and the performance of the obtained catalyst does not deteriorate.

After mixing a homogeneous solution containing Mo, V, P and X with a homogeneous solution containing Mo and Si which are catalytic component elements as essential components, the solution containing Y and optionally ammonia are mixed. A catalyst precursor is produced by mixing. In a preferred embodiment of the present invention, the catalyst precursor is a mixed salt of heteropolyacid Y and ammonia. Among Y, Cs is particularly preferable. Moreover, as X, Cu is preferable.

In the step of drying the solution or slurry containing the catalyst precursor to obtain the catalyst, a drying method usually used in the art, for example, a spray drying method can be adopted. The drying temperature is not particularly limited, but usually 100 to 250 ° C is used. The catalyst of the present invention thus prepared is
The crystal structure is mainly composed of a heteropolyacid salt structure.

The catalysts are used in fixed beds as granules or shaped bodies, but can also be used in moving beds or fluidized beds. The shape of the catalyst is not particularly limited, and conventionally known shapes such as sphere, tablet, ring, spoke ring, convex and convex ring can be used. As the molding method, tablet molding, extrusion molding, stirring granulation, rolling granulation and the like are used. The catalyst of the present invention can be used without a carrier, but may be diluted with silica, alumina, silica-alumina, carbon, silicon carbide or the like, if necessary, or can be used as a supported catalyst.

The present invention also relates to a method for producing methacrylic acid, which comprises subjecting methacrolein to gas phase catalytic oxidation with molecular oxygen in the presence of the above catalyst. In the gas phase catalytic oxidation reaction according to the present invention, a mixed gas composed of 1 to 10% by volume of methacrolein, 3 to 20% by volume of molecular oxygen and 70 to 90% by volume of a diluent gas is used as a source gas.
The gas is placed on the catalyst in the temperature range of 250 to 450 ° C. and the atmospheric pressure to 10 atm under the space velocity of 300 to 5000.
It is implemented by introducing with / hr. Air is usually used as the molecular oxygen, but pure oxygen may be used.
An inert gas such as nitrogen or carbon dioxide is used as the diluting gas. Further, a part of the non-condensable gas contained in the reaction gas may be circulated and used. It is preferable to use water vapor together as a diluent gas in order to enhance activity and selectivity. In that case, the water vapor in the source gas is usually 6
Add up to 0% by volume.

[0020]

【Example】

Example 1 While stirring 6000 ml of water with heating, 94 g of 85% phosphoric acid,
810 g of molybdenum trioxide, 63 g of vanadium pentoxide,
Copper oxide (9.7 g) was added and the mixture was heated under reflux for 3 hours to obtain a uniform solution (Liquid A). The solution A was cooled to 40 ° C., and 260 g of commercially available silicomolybdic acid (30 hydrate) was added to the solution A to obtain a uniform solution. This was used as the first raw material solution.
The Na content in the silicomolybdic acid used is Na / Si
The atomic ratio was 0.002. 28% ammonia water 13
6 g and 473 g of a 10% cesium nitrate aqueous solution were mixed to prepare a second raw material solution. The second raw material solution was added dropwise to the first raw material solution, and the resulting mixed solution was spray-dried. The dried powder is calcined and formed into a cylinder with a diameter and height of 5 mm.
Mo / V / P / C by firing in air at 60 ° C for 10 hours
u / Si / Cs / NH4 ratio is 12 / 1.2 / 1.4 /
A composite oxide catalyst of 0.2 / 0.2 / 0.4 / 3.9 was obtained. When this catalyst was analyzed by XRD, it had a heteropolyacid structure.

240 ml of the obtained catalyst was charged into a 3/4 inch steel reactor, and the raw material gas composition and reaction were 3% by volume of methacrolein, 9% by volume of oxygen, 20% by volume of steam, and 68% by volume of the remaining nitrogen. The initial performance of the catalyst was evaluated by carrying out the reaction under standard conditions of a vessel bath temperature of 290 ° C., a space velocity of 1500 / hr, and a reactor outlet pressure of 0.2 kg / cm ² G. After initial performance evaluation, methacrolein 5% by volume, oxygen 1
3% by volume, 25% by volume of water vapor, and 57% by volume of the remaining nitrogen was 57% by volume of raw material gas composition, reactor bath temperature 350 ° C., space velocity 30000 / hr, reactor outlet pressure 0.2 kg / cm ² G
After conducting the reaction for 10 days under the forced deterioration condition, the standard conditions were restored and the stability of the catalyst was evaluated. The results are shown in Table 1.

Example 2 While stirring 6000 ml of water with heating, 94 g of 85% phosphoric acid,
830 g of molybdenum trioxide, 53 g of vanadium pentoxide,
Copper oxide (9.7 g) was added and the mixture was heated under reflux for 3 hours to obtain a uniform solution (Liquid A). The solution A was cooled to 40 ° C., and 260 g of commercially available vanadium 1-substituted silicomolybdic acid (30 hydrate) was added to the solution A to obtain a uniform solution. This was used as the first raw material solution. 28% ammonia water 136g and 10
% Cesium nitrate aqueous solution 473 g was mixed to obtain a second raw material solution. After dropping the second raw material solution into the first raw material solution, a catalyst was prepared according to Example 1. The composition is Example 1
Is the same as The results of performance evaluation of this catalyst are shown in Table 1.

Example 3 A catalyst was prepared according to Example 2 by replacing the commercially available vanadium 1-substituted silicomolybdic acid in Example 2 with vanadium 2-substituted silicomolybdic acid. The results of performance evaluation of this catalyst are shown in Table 1.

Example 4 In order to clarify the influence of the mixing temperature of silicomolybdic acid on the catalytic performance, the same method as in Example 1 was adopted except that the mixing temperature of the liquid A and the commercially available silicomolybdic acid was changed to 80 ° C. To prepare a catalyst. The results of performance evaluation of this catalyst are shown in Table 1.

Comparative Example 1 In order to clarify the effect of silicon on the catalyst performance, a catalyst was prepared by removing only silicon from the composition of Example 1. That is, while stirring 6000 ml of water with heating, 85% phosphoric acid 94
g, molybdenum trioxide 1000 g, vanadium pentoxide 6
3 g and copper oxide 9.7 g were added and heated under reflux for 3 hours to obtain a uniform solution. This was used as the first raw material solution. 28% ammonia water 136g and 10% cesium nitrate aqueous solution 473
g to prepare a second raw material solution. After dropping the second raw material solution into the first raw material solution, a catalyst was prepared according to Example 1. The atomic ratio of each component of the catalyst was the same as in Example 1 except for Si.
Is the same as The results of performance evaluation of this catalyst are shown in Table 1.

Comparative Example 2 In order to clarify the effect of the silicon source on the catalytic performance,
A catalyst was prepared in the same manner as in Example 1, except that the homogeneous solution containing silicon was silicic acid instead of silicomolybdic acid. The amount of molybdenum trioxide was adjusted so that the catalyst composition was the same as in Example 1. In this case, silicic acid does not dissolve,
It did not become a homogeneous solution. The results of performance evaluation of this catalyst are shown in Table 1.

Example 5 The Na content in the silicomolybdic acid used was Na / Si.
A catalyst was prepared in the same manner as in Example 1 except that the atomic ratio was 0.02. The results of evaluation of the initial performance of this catalyst by the same method as in Example 1 are shown in Table 2.

Example 6 The content of Na in the silicomolybdic acid used was Na / Si.
A catalyst was prepared in the same manner as in Example 1 except that the atomic ratio was 0.3. The results of evaluation of the initial performance of this catalyst by the same method as in Example 1 are shown in Table 2.

[0029]

[Table 1]

[0030]

[Table 2]

The following can be seen from the examples. The catalyst having a heteropolyacid structure containing silicon as a part of the heteropolyacid structure was superior in activity and selectivity as compared with the catalyst having a heteropolyacid structure not containing silicon (Examples 1 to 3 and Comparative Example). 1). When the temperature at which the homogeneous solution containing silicon as a part of the heteropolyacid and the homogeneous solution containing the heteropolyacid containing Mo, V, and P as essential components are mixed is increased, the activity and the selectivity are lowered (Example 4). When the homogeneous solution containing silicon is not the solution containing heteropolyacid, the activity and the selectivity are lowered (Comparative Example 2). The lower the Na content in silicomolybdic acid, the higher the activity and selectivity. (Examples 1, 5, 6)

[0032]

INDUSTRIAL APPLICABILITY According to the present invention, a catalyst excellent in activity, methacrylic acid selectivity and stability can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Tokio Nagayama 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd. (72) Takashi Jimbo 1190 Kasama-cho, Sakae-ku, Yokohama, Kanagawa Mitsui Toatsu Inside Chemical Co., Ltd.

Claims (8)

[Claims] 1. The general formula (Mo) _a (V) _b (P) _c (Si) _d (X) _e (Y) _f (N
H ₄ ) _g (O) _h (In the formula, X is one or more elements selected from the group consisting of Sb, Cu, Co, Bi and As, and Y is K, Rb,
One or more elements selected from the group consisting of Cs and Tl, where a, b, c, d, e, f and g represent the atomic ratio of each element, and when a = 12, b = 0. 1-2, c = 1
-3, d = 0.05-0.5, e = 0.01-3, f =
0.1 to 3, f + g = 2 to 6, and h is the number of oxygen atoms required to satisfy the valence of each component. ) In producing a catalyst having a composition represented by the following, a homogeneous solution containing catalyst component elements Mo, V, P and X,
A homogeneous solution containing Mo and Si which are the catalyst component elements as essential components, and a homogeneous solution containing Y which is the catalyst component element,
If necessary, a solution or slurry containing a catalyst precursor is produced by mixing with ammonia, and the solution or slurry is dried. Methacrolein is subjected to vapor phase catalytic oxidation with molecular oxygen to produce methacrylic acid. A method of manufacturing a catalyst for manufacturing. 2. A homogeneous solution containing catalyst component elements Mo, V, P and X, and catalyst component elements Mo and S.
A catalyst precursor is prepared by mixing a uniform solution containing i as an essential component at a temperature of 0 ° C. to 60 ° C., and mixing the mixed solution, a uniform solution containing Y as a catalyst component element, and, if necessary, ammonia. To produce a solution or slurry containing
The method for producing a catalyst according to claim 1, wherein the solution or slurry is dried. 3. The method for producing a catalyst according to claim 1, wherein the homogeneous solution containing Mo, V, P and X and the homogeneous solution containing Mo and Si are solutions containing heteropolyacid, respectively. 4. The method for producing a catalyst according to claim 1, 2 or 3, wherein the catalyst has a heteropolyacid structure. 5. The method for producing a catalyst according to claim 1, wherein the amount of Na present in the homogeneous solution containing Mo and Si is 0.1 or less in terms of Na / Si atomic ratio. 6. The method for producing a catalyst according to claim 1, wherein X is Cu and Y is Cs. 7. The general formula (Mo) _a (V) _b (P) _c (Si) _d (X) _e (Y) _f (N
H ₄ ) _g (O) _h (In the formula, X is one or more elements selected from the group consisting of Sb, Cu, Co, Bi and As, and Y is K, Rb,
One or more elements selected from the group consisting of Cs and Tl, where a, b, c, d, e, f and g represent the atomic ratio of each element, and when a = 12, b = 0. 1-2, c = 1
-3, d = 0.05-0.5, e = 0.01-3, f =
0.1 to 3, f + g = 2 to 6, and h is the number of oxygen atoms required to satisfy the valence of each component. ), A homogeneous solution containing the catalyst component elements Mo, V, P and X, a homogeneous solution containing the catalyst component elements Mo and Si as essential components, and a catalyst component element. Methacrolein prepared by preparing a solution or slurry containing a catalyst precursor by mixing a certain homogeneous solution containing Y and ammonia if necessary, and drying the solution or slurry. A catalyst for producing methacrylic acid by gas-phase catalytic oxidation of molecular oxygen. 8. The general formula (Mo) _a (V) _b (P) _c (Si) _d (X) _e (Y) _f (N
H ₄ ) _g (O) _h (In the formula, X is one or more elements selected from the group consisting of Sb, Cu, Co, Bi and As, and Y is K, Rb,
One or more elements selected from the group consisting of Cs and Tl, where a, b, c, d, e, f and g represent the atomic ratio of each element, and when a = 12, b = 0. 1-2, c = 1
-3, d = 0.05-0.5, e = 0.01-3, f =
0.1 to 3, f + g = 2 to 6, and h is the number of oxygen atoms required to satisfy the valence of each component. ), A homogeneous solution containing the catalyst component elements Mo, V, P and X, a homogeneous solution containing the catalyst component elements Mo and Si as essential components, and a catalyst component element. Existence of a catalyst characterized in that a solution or slurry containing a catalyst precursor is produced by mixing a certain homogeneous solution containing Y and ammonia, if necessary, and the solution or slurry is dried. Below, a method for producing methacrylic acid, characterized by subjecting methacrolein to gas-phase catalytic oxidation with molecular oxygen.