JPS5814417B2 - 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 galboxic 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, and Japanese Patent Publication No. 38-19260 discloses a method for producing acrylic acid using a catalyst consisting of P, Mo, and As. Examples include a method for producing acrylic acid.

Many proposals have been made regarding the production method of methacrylic acid. For example, in Japanese Patent Publication No. 47-6605, Mo, Ni, Ti
, a catalyst consisting of Mo
, TI, U.S. Pat. No. 379
There are P, Mo, alkali metal catalysts in No. 5703, PMoSb catalysts in Belgian Patent No. 817100, etc.
From an industrialization standpoint, both have drawbacks in terms of selectivity and longevity.

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.The present inventors have also discovered a catalyst that is highly practical in terms of activity, selectivity, and longevity. They have found that the invention can be applied, and have 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: Mo12PaVbCroQdReSfO2, where Mo is molybdenum, P is phosphorus, ■ is vanadium, Cr is chromium, 0 is oxygen, and Q is (Mg, Ca,]
R is one or more metals selected from (K,
Rb. C8. One or more metals selected from TI, 1, S are (Al, Sb, Se. Cd. Bi, Nb
, Ta, Bi + Mn, Sr, Ba), as b, C
- ci, e, f, g are the respective numbers of atoms,
a=0.5-6, b=0.01-6, c=0.01-6
, d=o-2~6, e=0.2~6, f=0.01~
6.g 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, molybdenum, 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 form extremely complex compounds depending on their mixing ratio and heat treatment temperature and atmosphere. do.

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

However, it has been found that the catalyst system of the present invention maintains high catalytic activity over a long period of time.

This is thought to be because the added metals other than phosphorus and molybdenum form extremely stable salts with phosphorus and molybdenum in the catalyst of the present invention, and this contributes 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.

To give an example, add ammonium metavanadate to an aqueous solution of ammonium molybdate, then add potassium nitrate, add phosphoric acid, add an aqueous solution of magnesium nitrate, then add tantalum oxide and chromic anhydride, and then evaporate and dry. Hardening method, molybdic acid, potassium phosphate, magnesium oxide, vanadium oxide, chromic anhydride,
A method of mixing antimony oxide powder, a method of adding an aqueous solution of phosphoric acid, cesium nitrate, chromic anhydride, and calcium nitrate to an aqueous solution of phosphomolybdic acid, and then adding niobium oxide and selenium oxide powder and evaporating to dryness. The mixture obtained in step 1 is molded and then heat treated, or heat treated and molded to obtain a catalyst.

Further, the catalyst component may be supported on a known inert carrier such as silica, alumina, silica-alumina, silicon carbide, etc., or it 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.

As vanadium, vanadate, ammonium metavanadate, etc. are used.

For chromium, chromium compounds such as chromic anhydride, potassium chromate, and ammonium chromate are used.

As the phosphorus, phosphoric acid, phosphorus pentoxide, phosphomolybdic acid, phosphate, etc. can be used.

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

Examples include magnesium nitrate, calcium nitrate, barium chloride, caustic potassium, potassium nitrate, cesium carbonate, thallous nitrate, 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° to 650°C, preferably 350°C.
A range of 600°C 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.

Although the reaction temperature can be selected within the range of 2400 to 450°C, 2600 to 400°C is 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).

Example 1 2.4 parts of ammonium paramolybdate was dissolved in 200 parts of pure water at about 60°C.

Add and dissolve 0.7 parts of ammonium metapanadate, add 4.6 parts of 85% phosphoric acid, and then add 4.04 parts of potassium nitrate, 5.13 parts of magnesium nitrate, and 1 part of chromic anhydride to the purified solution. A solution dissolved in 50 parts of water was added, and finally a solution of 3.75 parts of aluminum nitrate in 30 parts of pure water was added, and the mixture was evaporated to dryness while heating.

The obtained cake was dried at 130° C. for 16 hours, compression molded, and calcined at 450° C. for 2 hours, and this was used as a catalyst.

What is the composition of the catalyst in atomic ratio? o 12P2Mg1K2Vo, 3Cr. ,Alo,
It was 5.

This catalyst was packed into a reactor, and 5% methacrolein and 1% oxygen were added.
A mixed gas of 0% nitrogen, 30% water vapor, and 55% nitrogen (volume %) was passed through the reactor at a reaction temperature of 270°C and a contact time of 3.6 seconds.

When the product was collected and analyzed by gas chromatography, the methacrolein reaction rate was 83.5%, and the methacrylic acid selectivity was 84.0%.

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 82.7% and the methacrylic acid selectivity was 84.
．． It was 2%.

Example 2-18 The following catalyst was prepared in the same manner as in Example 1 and reacted under the same conditions as in Example 1 to obtain the results shown in Table 1.

It was reacted with a mixed gas of 10% oxygen, 30% water vapor, and 55% nitrogen at a predetermined temperature for a contact time of 3.6 seconds, and the results shown in Table 2 were obtained.

Comparative Examples 1, 2, 3 Catalysts were prepared using the method of Example 1, except for potassium nitrate or chromic anhydride, or ammonium metavanadate and chromic anhydride, and tested using the method of Example 1. The results are shown in Table 3. Indicated.

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. Mo12PaVbCrcQdReSfOg, where Mo is molybdenum, P is phosphorus, ■ is vanadium, Cr is chromium, 0 is oxygen, Q is one or more metals selected from (Mg, Ca), and R is (K, Rb,
S is one or more metals selected from (Al, Sb, Se, Cd, Bi, Nb, Ta,
One or two selected from Bi+Mn, Sr, Ba)
Representing more than one metal, a, b, c, d, e, f, g
are the respective numbers of atoms, a=0.5 to 6, b=0
．． 01-6, c=0.01-6, d=0.2-6, e=
0.2-6, f=0.01-6, g indicates the number required to make an oxide.