JPS5927217B2 - Production method of catalyst for methacrylic acid production - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for producing a catalyst for producing methacrylic acid containing molybdenum, phosphorus, vanadium, an alkali metal element, and oxygen.

No.0 For the production of methacrylic acid containing molybdenum, phosphorus, vanadium, alkali metal elements, and oxygen, which is conventionally used when producing methacrylic acid by contacting methacrolein with molecular oxygen in the presence of a catalyst in a high-temperature gas phase. The catalyst is disclosed in, for example, JP-A-50-582013, JP-A-5
0-96522, JP 51-113818, JP 51-115413, JP 52-3
It is described in Japanese Patent No. 6619, etc., and is well known. These catalysts containing molybdenum, phosphorus, vanadium, alkali metal elements, and oxygen are generally prepared by preparing compounds containing catalyst component elements such as molybdenum compounds, phosphorus compounds, vanadium compounds, and compounds of alkali metal elements in the presence of water. The resulting mixture is concentrated and/or dried to form a clay-like or powdered product, which is then molded into a molded product, and then the molded product is fired. However, the above-mentioned clay-like materials and powder-like materials are dry and have very poor moldability, and even if they are molded using an extruder, a rolling granulator, etc., and then calcined, they cannot be mechanically used in a fixed bed reactor for practical use. It is difficult to prepare catalysts having a strength, generally a crushing strength of one catalyst, of greater than about 3k9/catalyst. Also, even if the moldability is poor, when molding with a tablet machine,
Although it is possible to prepare molded products and catalysts with high mechanical strength by adjusting the molding machine or devising the molding operation,
The performance of the catalyst (reactivity to methacrolein, selectivity to methacrylic acid, etc.) decreases as the mechanical strength increases. The disadvantage is that the yield is significantly reduced. The inventors have developed a catalyst containing molybdenum, phosphorus, vanadium, an alkali metal element, and oxygen, with the aim of developing a catalyst that can produce methacrylic acid at a higher yield and that can improve the above-mentioned difficulties. We conducted intensive research on catalysts used in fixed bed reactors and their preparation methods.

As a result, catalysts containing molybdenum, phosphorus, vanadium, alkali metal elements, and oxygen that are columnar, spherical, etc. with a diameter of about 30 mψ or more and a size of 3 to 1001 nψ, which are generally used in fixed bed reactors, (1) The selectivity for methacrylic acid is closely related to the pores on the catalyst surface, and as the average pore radius (measured by mercury intrusion porosimetry) increases, the selectivity to methacrylic acid also improves;
(3) Adding a specific amount of organic substances such as cellulose, polyvinyl alcohol, polyethylene glycol, gelatin, etc. during catalyst preparation, especially before molding, will significantly improve moldability; (3) Organic (4) When a substance is added and mixed to form a molded product with a specific crushing strength and then fired, the average pore radius easily becomes K2OOOO ~ 12,000 and the catalytic strength increases; (4) A specific amount of organic substance is added and mixed. The inventors came to the present invention based on the knowledge that the methacrylic acid having the above-mentioned average pore radius, which was prepared by the above method, shows a high yield of methacrylic acid and has a mechanical strength that can withstand practical use.

This invention involves mixing compounds containing catalytic elements such as molybdenum compounds, phosphorus compounds, vanadium compounds, and compounds of alkali metal elements in the presence of water, and concentrating and/or drying the resulting mixture to form a clay-like or After making it into a powder, it is formed into a molded product, and then the molded product is fired to convert methacrolein into molecular oxygen and high temperature in a fixed bed reactor containing molybdenum, phosphorus, vanadium, alkali metal elements, and oxygen. In a method for producing a catalyst for producing methacrylic acid, which is used in a method for producing methacrylic acid through a catalytic reaction in the gas phase, a clay-like or powdered material consisting of cellulose, polyvinyl alcohol, polyethylene glycol, and gelatin is added to the clay-like or powdered material before molding. 2 to 8% by weight of one or more organic substances selected from the group is added and mixed so that the molded product has a crushing strength of 1.5 to 6 kg/molded product, and then the molded product is fired to improve the surface A process for producing a catalyst for producing methacrylic acid, characterized in that the catalyst has a large number of pores and has an average pore radius of 2,000 to 12,000 A, containing molybdenum, phosphorus, vanadium, an alkali metal element, and oxygen. It is.

According to this invention, the catalyst is easy to manufacture, has good moldability during molding, has excellent methacrolein reactivity and selectivity to methacrylic acid, and not only shows a high methacrylic acid yield, but also has excellent mechanical properties. It has a great feature of being extremely strong.

Therefore, when the catalyst obtained in this invention is used in a fixed bed reactor, methacrylic acid can be produced more advantageously than conventionally known catalysts containing molybdenum, phosphorus, vanadium, alkali metal elements, and oxygen. . In this invention, during catalyst production, especially before molding, one or more organic compounds selected from the group consisting of cellulose, polyvinyl alcohol, polyethylene glycol, and gelatin are added to the clay-like or powdered material containing catalyst component elements. substance 2
The crushing strength of the molded product is 1.5 to 6 after adding ~8% by weight.
It is important to mold the molded product to a weight of 1 kg/molded product, and then to fire the resulting molded product.

By adding and mixing organic substances, the moldability of clay-like materials and powder-like materials containing catalytic component elements such as molybdenum, phosphorus, vanadium, and aluori metal elements, which conventionally had poor moldability, is significantly improved. It can be easily formed into a columnar or spherical molded article, and when the molded article is fired, the organic substance is decomposed and volatilized, resulting in a practical catalyst having many pores on its surface.

The addition and mixing of the organic substance may be carried out at any stage during catalyst production before molding, but it is preferably done immediately before molding, preferably in the form of clay or powder before molding, particularly preferably in dry powder. It is best to add and mix with. If too much organic material is added and mixed, the resulting catalyst will instead become brittle with low mechanical strength.
Also, if the amount is too small, the effect of the addition will not be realized, so the amount added should be 2 times the amount of clay or powder (dry equivalent).
~8% by weight is preferable. Further, in this invention, the average pore radius of the pores of the catalyst is important.

Even with catalysts prepared by adding and mixing organic substances, methacrylic acid cannot be produced in high yield with catalysts having an average pore radius smaller than 2000A. The average pore radius largely depends on the mechanical strength of the molded product before firing, and if the mechanical strength of the molded product is too high, the average pore radius will become small. In order to produce a catalyst with an average pore radius of 2,000 to 12,000 A, the crushing strength of the molded product (measured after drying when the molded product is wet) must be 1.5 to 6 kg.
/For example, it is preferable to mold the product into a molded product using a molding machine such as a tablet press, an extrusion molding machine, or a rolling granulator, and then to bake it.

By adding and mixing the above-mentioned amounts of organic substances, forming a molded product having the above-mentioned crushing strength, and then firing, the mechanical strength is further improved compared to that during forming, and the fixed-bed reactor having the above-mentioned pore radius can be easily formed. A catalyst suitable for use in is obtained. Firing is generally carried out under an oxygen-containing gas atmosphere, such as air, for a temperature of 300-400 m
The calcination is preferably carried out at a temperature of 50°C, preferably 350 to 430°C; if the calcination temperature is too high or too low, the performance of the catalyst will deteriorate. In the method for producing a catalyst containing molybdenum, phosphorus, vanadium, an alkali metal element, and oxygen according to the present invention, the catalyst composition is not particularly limited, but in order to produce methacrylic acid with a particularly high yield, the following general composition formula: [
In this formula, MO is molybdenum, P is phosphorus, V is vanadium, A is an alkali metal element, preferably one or more alkali metal elements selected from the group consisting of potassium, cesium and rubidium, and O is oxygen; Subscript A
, b, c, d and e indicate the number of atoms, and when a is 12, b = 0.5 to 3, c = 0.1 to 2, d = 0.5 to 3
It is most preferable that e has a composition expressed by the half value 1fr of each of the above-mentioned Tr tests.

In addition, when manufacturing a catalyst represented by this general compositional formula,
For 12 molybdenum atoms, Ag, Al, Ba, Ca,
Even if one or more elements such as Cu, Mg, Mn, Pb, Sr, Te, etc. are present as catalyst component elements with 0.01 to 2 atoms, it will have a large effect on the effect of adding the organic substance, the average pore radius of the catalyst, etc. There isn't. In this invention, compounds containing catalyst component elements such as molybdenum compounds, phosphorus compounds, vanadium compounds, and alkali metal element compounds used as starting materials for catalyst production are conventionally generally molybdenum, phosphorus, vanadium, alkali metal elements, and oxygen. For example, molybdenum compounds such as molybdenum trioxide, 12-molybdophosphoric acid, 18-molybdoniphosphoric acid, ammonium molybdate, orthophosphoric acid, metaphosphoric acid, Phosphorus compounds such as phosphoric acid and ammonium salts of phosphoric acid; vanadium compounds such as vanadium pentoxide, ammonium metavanadate, vanadyl sulfate, and vanadium tetrachloride; nitrates, sulfates, and carbonates of alkali metal elements such as potassium, cesium, and rubidium. , chloride, etc.

In this invention, the catalyst is generally a molybdenum compound,
A compound containing a catalyst component element such as a phosphorus compound, a vanadium compound, or an alkali metal element compound is mixed in the presence of water, and the resulting mixture is concentrated and/or dried,
After it is made into a clay-like or powdered material, a predetermined amount of organic material is added and mixed, the molded product is molded so that the crushing strength of the molded product is 1.5 to 6 kg/molded product, and then the molded product is fired. manufactured by An example of a typical manufacturing method is as follows. A molybdenum compound is dissolved or suspended in water, and an aqueous solution of a phosphorus compound, an aqueous solution of an alkali metal element compound, and an aqueous solution of a vanadium compound are added and mixed under stirring.In other words, the catalyst component element is dissolved or suspended in water. and heating and concentrating the resulting mixture,
5 to 20 hours at 100 to 250 C, preferably 120
After drying at ~220°C for 6 to 16 hours and pulverizing the obtained dried product into a powder, 2 to 8% by weight of cellulose and polyvinyl alcohol polyvinyl alcohol based on the powder (in terms of dry matter) were added. The crushing strength of the molded product (measured after drying when the molded product is wet) is 1.5 to 1.5 by adding and mixing one or more organic substances selected from the group consisting of Coulcet γ-dogelatin. 6k9/moulding, and then the molding is fired at 300-450°C for 3-20 hours, preferably at 350-430°C for 5-10 hours.

When the catalyst is produced in this manner, a target catalyst having a large number of pores on its surface and an average pore radius of 2000 to 12000 A is suitable for use in a fixed bed reactor. Further, in the production of the catalyst, a mixture obtained by mixing a compound containing a catalyst component element in the presence of water may be heated and concentrated to form a clay-like material, and an organic substance may be added and mixed thereto. In producing methacrylic acid by catalytically reacting methacrolein with molecular oxygen in a high-temperature gas phase in a fixed bed reactor in the presence of the catalyst obtained in this invention, pure oxygen gas may be used as the molecular oxygen. In general, it is economical to use air since it does not need to be particularly pure.

Furthermore, methacrolein used in the catalytic reaction does not need to be of high purity.

Contains n-butene and isobutylene, such as spent BB, which is obtained by the oxidation reaction of isobutylene or is the residue after extracting and separating 1,3-butadiene from the C4 fraction produced as a by-product during naphtha decomposition. It may also be obtained by an oxidation reaction of a hydrocarbon mixture. However, if a product containing a large amount of unsaturated aldehyde other than methacrolein is used, it will not only delay the reaction, but also increase the amount of by-products and polymers, so it is better to avoid products that have an adverse effect on the reaction. In addition, in the catalytic reaction, nitrogen, carbon dioxide, water vapor, etc., which do not adversely affect the reaction, can be used as diluents along with molecular oxygen and methacrolein. Not only that, but it also has the effect of sustaining catalytic activity.

The catalytic reaction can be carried out under normal pressure, increased pressure, or reduced pressure, but it is generally convenient to carry out the reaction under normal pressure.

The reaction temperature is 250-400°C, preferably 280-36°C.
0°C is preferred. Contact time (normal pressure, room temperature) is 0.1~
A suitable time is 10 seconds, preferably 0.5 to 5 seconds. For the catalytic reaction, it is preferable to use a mixed gas of methacrolein and molecular oxygen, generally air plus water vapor, and the composition of the mixed gas is such that molecular oxygen is 0.5% of methacrolein. ~7 mol times, preferably 1 to 5 mol times,
Suitable water vapor is 1 to 30 times the mole of methacrolein, preferably 2 to 10 times the mole of methacrolein. In addition, conventionally known methods such as condensation and solvent extraction can be used to recover methacrylic acid.

Next, Examples and Comparative Examples will be shown. Reaction rate in each example (4)
, selectivity (a) and yield (4) are in accordance with the following definitions. In each example, the average pore radius of the pores in the catalyst is a value measured by mercury porosimetry. The crushing strength of a molded product or catalyst (Kg/molded product or catalyst) is measured by placing one molded product or catalyst on a smooth sample stand, applying a load from above, and measuring whether the molded product or catalyst is crushed. Using a Kiya type hardness tester that measures the load (1<g) when
This is the average value of the results measured on 30 molded products or catalysts. Example 1 12-molybdophosphoric acid [H3 (PMOl
2O4O) 29.5H20] 200f! Add 5.39 cesium nitrate [CSNO3] and 1 potassium nitrate [KNO3] to 100 ml of water.
6.6 g and ammonium metavanadate [NH4T
A solution in which O3]49 was dissolved was added and mixed with stirring, and the resulting mixture was heated and concentrated, and then heated to 15% at 13°C.
The product was dried for an hour to obtain a dry product, and then the dried product was ground to a particle size of 20 mesh (0.833111n) or less to obtain a powder containing catalyst component elements.

Next, 7.5 f1 of cellulose microcrystals [trade name: Avicel] were added and mixed with the powdered material 1509, and the tablet press was adjusted so that the crushing strength of the molded product was approximately 4k9/molded product. The powdered material to which crystals were added and mixed was molded into a columnar molded product with a diameter of 5111111ψ and a height of 5[001H].

The powdered material had very good moldability and was not dry and difficult to tablet. The molded product was fired at 400° C. for 5 hours in an air atmosphere to obtain a catalyst.

The composition of this catalyst (atomic ratio, oxygen omitted, same below) is:
MOL2PlKl. 9CSO. 3VO. It is 4. Next, 12 ml of this catalyst was packed into a stainless steel reaction tube with an inner diameter of 70 nψ and a length of 40 mm, and a volume of methacrolein 401), oxygen 10%, steam 30%, and nitrogen 56
01) was flowed at a flow rate of 150ml/min,
The catalytic reaction was carried out at a reaction temperature of 320°C.

Table 1 shows the crushing strength of the molded product, the crushing strength of the catalyst, the average pore radius of the pores in the catalyst (hereinafter referred to as the average pore radius of the catalyst), and the results of the contact reaction.

Comparative Example 1 Except that cellulose or microcrystals were not added,
A catalyst having the same composition as in Example 1 was prepared under the same conditions as in Example 1.

However, even if the powdered material is molded under the same tableting conditions as in Example 1, the crushing strength of the molded material is low, the powdered material is dry and difficult to enter the tablet machine, and its moldability is poor. In addition, the crushing strength of the obtained catalyst was also low. Table 1 shows the crushing strength of the molded product, the average pore radius and crushing strength of the catalyst, and the results of a catalytic reaction conducted under the same conditions as in Example 1.

〉Comparative Example 2 The crushing strength of the molded product is approximately 31
<9/ A catalyst having the same composition as in Example 1 without adding cellulose microcrystals in the same manner as in Comparative Example 1, except that the tableting machine was adjusted to form a powdered product. was prepared.

5. In this case, the moldability of the powdered material was poor as in Comparative Example 1.

Table 1 shows the crushing strength of the molded product, the average pore radius and crushing strength of the catalyst, and the results of a catalytic reaction conducted under the same conditions as in Example 1.

3 Comparative Example 3 The crushing strength of the molded product is approximately 10
A catalyst having the same composition as in Example 1 was prepared by adding cellulose microcrystals in the same manner as in Example 1, except that the tableting machine was adjusted to form a powdered product to obtain k9/molded product. Prepared.

In this case, the moldability of the powdered material was good, and the crushing strength of the molded product and catalyst was high, but the average pore radius of the catalyst was small. Table 1 shows the crushing strength of the molded product, the average pore radius and crushing strength of the catalyst, and the results of a catalytic reaction conducted under the same reaction conditions as in Example 1.

Comparative Example 4 Cellulose microcrystals 2 were added to powder 1509 so that the amount of cellulose microcrystals added was 15% by weight based on the powder.
By adding and mixing 2.5f1, the crushing strength of the molded product is approximately 3kg.
A catalyst having the same composition as in Example 1 was prepared in the same manner as in Example 1, except that the tableting machine was adjusted to form a powdered product.

In this case, the moldability of the powdered material was good and the pore radius of the catalyst was large, but the crushing strength of the catalyst was extremely low.
Table 1 shows the crushing strength of the molded product, the average pore radius and crushing strength of the catalyst, and the results of a catalytic reaction conducted under the same reaction conditions as in Example 1.

Examples 2 to 4 Instead of the cellulose microcrystals of Example 1, polyvinyl alcohol (degree of polymerization about 500), polyethylene glycol (average molecular weight about 400) and gelatin were added to the powder at a concentration of 5% by weight. A catalyst having the same composition as in Example 1 was prepared in the same manner as in Example 1, except that the powdered material was mixed and molded so that the crushing strength of the molded product was 2 to 3 k9/molded product.

Regardless of whether polyvinyl alcohol, polyethylene glycol or gelatin was used, the moldability of the powder was good and the mechanical strength of the catalyst was suitable for use in a fixed bed reactor. Table 1 shows the results of a catalytic reaction conducted under the same reaction conditions as in Example 1, the crushing strength of the molded product, the average pore radius of the catalyst, and the crushing strength.

Examples 5 to 11 Example 1 was carried out so that the composition of the catalyst was as shown in Table 2.
After preparing a powder containing catalyst component elements in the same manner as above, adding and mixing cellulose microcrystals in the amount listed in Table 2 to the powder to obtain a powder having the crushing strength listed in Table 2. Diameter 5mψ, height 501! A catalyst was prepared by molding the product into a columnar molded product of NH using a tablet press and then calcining it in the same manner as in Example 1.

Note that rubidium nitrate [RbNO3] was used as the rubidium in Examples 8 and 9. Further, in Example 9, firing was performed at 410°C. A contact reaction was then carried out under the same reaction conditions as in Example 1.

In addition, only in Example 9, the reaction temperature was changed to 310° C. and the catalytic reaction was carried out. The crushing strength of the molded product and the catalyst are shown in Table 2, and the average pore radius of the catalyst and the results of the contact reaction are shown in Table 3.
Shown in the table.

Example 12 Example 1 was carried out so that the composition of the catalyst was as shown in Table 2.
After preparing a powder containing molybdenum, phosphorus, vanadium and potassium in the same manner as above, the powder 150
7% by weight of cellulose microcrystals and water 15 m
1 and mix in a two-dimensional machine to form a clay-like material.The clay-like material is made into a string using an extruder, and the string-like material is placed in a rolling granulator (trade name: Marmerizer 1) to a diameter of 3. ~5[[0nψ
The catalyst was prepared by molding it into a spherical molded product and calcining it at 390° C. for 5 hours in an air atmosphere.

The crushing strengths of the molded products and catalysts are shown in Table 2, and the average pore radius of the catalysts is shown in Table 3.

Next, a catalytic reaction was carried out under the same reaction conditions as in Example 1, except that the reaction temperature was changed to 300°C.

Claims (1)

[Claims] 1. A compound containing a catalyst component element such as a molybdenum compound, a phosphorus compound, a vanadium compound, or an alkali metal element compound is mixed in the presence of water, and the resulting mixture is concentrated and/or dried to form a clay-like or powdered material. After that, it is formed into a molded product, and then the molded product is fired to produce methacrolein in a high-temperature gas phase with molecular oxygen in a fixed bed reactor containing molybdenum, phosphorus, vanadium, alkali metal elements, and oxygen. In a method for producing a catalyst for producing methacrylic acid used in a method for producing methacrylic acid by catalytic reaction, a clay or powder material selected from the group consisting of cellulose, polyvinyl alcohol, polyethylene glycol and gelatin is added to the clay-like or powdered material before molding. 2 to 8% by weight of one or more of the above organic substances are added and mixed and molded so that the crushing strength of the molded product is 1.5 to 6 kg/molded,
Next, the molded product is fired to produce molybdenum having a large number of pores on the surface and an average pore radius of 2,000 to 12,000.
A method for producing a catalyst for producing methacrylic acid, characterized by obtaining a catalyst containing phosphorus, vanadium, an alkali metal element, and oxygen.