JPS584013B2 - Fuhouwa Carbon Sanno Seizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for producing the corresponding unsaturated carboxylic acid from an unsaturated aldehyde and molecular oxygen.

Many methods have already been proposed for producing unsaturated carboxylic acids from unsaturated aldehydes by gas phase oxidation.

For example, Japanese Patent Publication No. 44-12129 describes a method for producing acrylic acid from acrolein using a catalyst consisting of Mo, V, W, and silica;
, Mo, and As.

Many proposals have been made regarding the production method of methacrylic acid. For example, in Japanese Patent Publication No. 47-6605, Mo, Ni, Ti
Catalyst consisting of Mo, T
U.S. Pat. No. 3,795,703
No. P, Mo, alkali metal catalyst, Belgian patent No. 8
There are P, Mo, sb based catalysts such as No. 17100, but from the viewpoint of industrialization, all of them have drawbacks in terms of selectivity and life.

The present inventors have researched catalysts used to produce methacrylic acid from methacrolein, and have discovered a catalyst with high practicality in terms of activity, selectivity, and lifespan.This catalyst can also be used in the production of acrylic acid from acrolein. They found that the invention can be applied and completed the present invention.

The present invention uses a mixed gas containing acrolein or methacrolein and molecular oxygen as a catalyst represented by the following formula: Mo12PaQbRcSdOe, where Mo represents molybdenum, P represents phosphorus, and 0 represents oxygen.
Further, Q is one or more metals selected from (Mg, Ca), R is one or more metals selected from (K, Rb, Cs, Tl), and S is (Ta, sb, Nb,B
i) represents one or more metals selected from a);
, b, c, d, e represent the number of atoms, a=0
．． 5-6, b=0.2-6, c=0.2-6, d=0.
01-6, e indicates the number required to make an oxide.

This is a method for producing acrylic acid or methacrylic acid, which is characterized in that it is brought into contact with acrylic acid or methacrylic acid in a high-temperature gas phase.

In the catalyst used in the present invention, the state of existence of phosphorus, morin, and additional metals is complex and not strictly clear, but it is likely that none of the components exists as a single oxide but is tightly bound together. I think that the.

It is well known that catalyst systems containing phosphorus and molybdenum are effective for the gas-phase oxidation of acrolein or methacrolein, but phosphorus and molybdenum are extremely complex compounds depending on their mixing ratio, heat treatment temperature and atmosphere. generate.

Therefore, when a catalyst system containing phosphorus and molybdenum is used for gas phase oxidation, activity and selectivity often decrease over time due to changes in the catalyst structure in the reaction temperature range normally used.

In the catalyst of the present invention, added metals other than phosphorus and molybdenum have the property of forming extremely stable salts with phosphorus and molybdenum, and this is thought to contribute to maintaining activity and selectivity.

Various methods can be used to produce the catalyst.

For example, conventionally well-known evaporation to dryness methods, precipitation methods, oxide mixing methods, etc. can be used.

For example, add potassium nitrate to an aqueous solution of ammonium molybdate, add phosphoric acid, add an aqueous solution of magnesium nitrate, and then add tantalum oxide powder and evaporate to dryness. Molybdic acid, potassium phosphate, A method of mixing powders of magnesium oxide and antimony oxide, a method of adding phosphoric acid, an aqueous solution of cesium nitrate, an aqueous solution of calcium nitrate to an aqueous solution of phosphomolybdic acid, and then adding powders of niobium oxide and tantalum oxide and evaporating to dryness, etc. The mixture obtained in step 1 is molded and then heat treated, or the mixture obtained is molded after heat treatment to obtain a catalyst.

Further, the catalyst component may be supported on a known inert carrier such as silica, alumina, silicon carbide, or the like, or may be used after being diluted.

As raw materials for each element, for example, molybdenum trioxide, molybdic acid, ammonium molybdate, phosphomolybdic acid, etc. can be used for molybdenum.

Phosphorus is extracted using phosphoric acid, phosphorus pentoxide, phosphomolybdic acid, phosphates, etc.

As the additive metal, nitrates, chlorides, phosphates, oxides, carbonates, ammonium salts, etc. can be used.

For example, magnesium nitrate, calcium nitrate, caustic potash, potassium nitrate, cesium carbonate, thallous nitrate,
These include bismuth nitrate, niobium oxide, antimony oxide, and tantalum oxide.

As raw materials for each component, in addition to those exemplified above, materials that become oxides by thermal decomposition, hydrolysis, oxidation, etc. can also be used.

The temperature of the heat treatment is 300°C to 650°C, preferably 350°C.
A range of ℃ to 600℃ is preferable.

The heat treatment time varies depending on the temperature, but is suitably within the range of one hour to several tens of hours.

The raw material unsaturated aldehyde may contain small amounts of impurities such as water and lower saturated aldehydes, but these impurities do not affect the reaction.

Although the unsaturated aldehyde concentration in the raw material gas can be varied within a wide range, it is preferably 1 to 20% by volume, particularly 3 to 10% by volume.

It is economical to use air as the oxygen source, but air enriched with oxygen can also be used if necessary.

The oxygen concentration in the raw material gas is defined by the molar ratio to the unsaturated aldehyde, and this molar ratio is 0.3 to 4, particularly 0.4 to 4.
2.5 is preferred.

The raw material gas may be diluted with an inert gas such as nitrogen, water vapor, or carbon dioxide.

The reaction pressure is preferably from normal pressure to several atmospheres.

The reaction temperature can be selected within the range of 240°C to 450°C, with 260°C to 400°C being particularly preferred.

The method of the present invention will be explained in detail below with reference to Examples and Comparative Examples.

In the following, parts represent parts by weight.

The unsaturated carboxylic acid selectivity is the unsaturated aldehyde (
represents the ratio (%) of moles).

The reaction time represents the elapsed time measured from the time when the stated reaction conditions were established.

Example 1 42.4 parts of ammonium rosemolybdate was dissolved in 200 parts of pure water at about 60°C.

To this, 4.04 parts of potassium nitrate and 4.6 parts of 85% phosphoric acid were added, and then 5.13 parts of magnesium nitrate dissolved by heating in 50 parts of pure water was added, and finally, 4.04 parts of tantalum pentoxide was added.
, 42 parts were added, and the mixture was heated and evaporated to dryness with stirring.

The resulting case was dried at 130°C for 16 hours, compression molded, sieved to 10 to 20 mesh, and fired at 450°C for 2 hours.
This was used as a catalyst.

The composition of the catalyst is Mo12, P2, Mg1, K2,
It was Ta1.

This catalyst was packed into a reactor, and 5% methacrolein and 1% oxygen were added.
A mixed gas of 0% water vapor, 30% water vapor, and 55% nitrogen (volume %) was passed through the reactor at a reaction temperature of 340° C. and a contact time of 3.6 seconds.

When the product was collected and analyzed by gas chromatography, the methacrolein reaction rate was 80.0% and the methacrylic acid selectivity was 80.1%.

In addition, acetic acid, carbon dioxide gas, carbon monoxide, etc. were produced.

The reaction was continued for about 1000 hours under the same conditions, but the methacrolein reaction rate was 79.8% and the methacrylic acid selectivity was 80%.
．． It was 3%.

Examples 2 to 11 The following catalysts were prepared in the same manner as in Example 1 and reacted under the same conditions to obtain the results shown in Table 1.

Examples 10 to 12 Using the catalysts of Examples 1, 7, and 8, a mixed gas of 5% aqueous rain, 10% oxygen, 30% water vapor, and 55% nitrogen was reacted at a predetermined reaction temperature and for a catalyst time of 3.6 seconds. The reaction was performed and the results shown in Table 2 were obtained.

Comparative Examples 1 to 3 A catalyst was prepared using the method of Example 1 except for potassium nitrate, and a catalyst was prepared using the method of Example 5 except for calcium nitrate or calcium nitrate and antimony oxide, and the conditions were the same as in Example 1 except for the reaction temperature. The results shown in Table 3 were obtained.

Claims (1)

[Claims] 1. A method for producing acrylic acid or methacrylic acid, which comprises bringing a mixed gas containing acrolein or methacrolein and molecular oxygen into contact with a catalyst represented by the following formula in a high-temperature gas phase. Mo12PaQbRcSdOe where Mo is molybdenum, P is phosphorus, 0 is oxygen, Q is one or two metals selected from (Mg, Ca), and R is 1 selected from (K, Rb, Cs, Tl).
The species or two or more metals, S are (Ta, Sb, Nb, Bi
), one or more metals selected from a, b, c,
d and e each represent the number of atoms, a = 0.5 to 6,
b=0.2-6, c=0.2-6, d=0.01-6,
e indicates the number required to make an oxide.