JPS5833848B2 - Methacrylic Sanno Seizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing methacrylic acid in good yield by catalytically oxidizing methacrolein with molecular oxygen or a molecular oxygen-containing gas in a high-temperature gas phase.

Many methods have already been proposed for producing unsaturated carboxylic acids by catalytic oxidation of unsaturated aldehydes in a high-temperature gas phase, but these methods mainly produce acrylic acid from acrolein. There are only a few articles related to methods for producing methacrylic acid from methacrolein.

In fact, a method for producing acrylic acid from acrolein has actually been industrialized, but a method for producing methacrylic acid from methacrolein has not yet been industrialized, despite the above proposals.

The reason for this is that the yield when producing methacrylic acid from methacrolein is much lower than when producing acrylic acid.

In the case of methacrylic acid, the yield is lower compared to acrylic acid production because methacrolein is more easily oxidized than acrolein, and complete oxidation (-carbon oxide,
This is thought to be due to the fact that carbon dioxide (carbon dioxide production) is likely to occur.

On the other hand, catalysts that can be used as oxidation catalysts for the oxidation of methacrolein to methacrylic acid either have low reaction performance or, although they show relatively good performance in the early stages of the reaction, their active lifespan is short and they are not suitable for practical industrial use. It has drawbacks that make it unsuitable for use as a catalyst.

In the present invention, methacrylic acid can be produced in a desired high yield only by using a catalyst consisting of molybdenum, phosphorus, thallium, vanadium, and copper and oxygen.If the above conditions are not satisfied, the catalyst The effect will be unsatisfactory.

- As long as the catalyst of Rikiki's invention contains each element specified above as an essential component, good results can be obtained with any composition ratio, but in particular, when molybdenum is fixed at 12, the following Favorable results are obtained when using a catalyst shown by the empirical formula:

Here, a, b, c, d, and e are the numbers of atoms of phosphorus, thallium, vanadium, copper, and oxygen, respectively.

and a=0.1~16, b=0.01~16, c=0
．． 01 to 12, d=0.01 to 16, and e is the number of oxygen atoms sufficient to satisfy the valences of other elements.

A more preferable composition range of the catalyst is around a=2, especially a=1 to 3, b=2, as specifically shown in the examples.
Around, especially a value of 3 or less that does not include b = o, around c = 1.5, especially a value of 3 or less that does not include C = O, around d = 1, especially a value of 3 or less that does not include d = o, e=the number of oxygen atoms sufficient to satisfy the valences of other elements.

In producing the catalyst used in the present invention, this type of oxide catalyst preparation method is generally used.

For the constituent raw materials of the catalyst, molybdenum compounds such as ammonium molybdate, molybdic acid, and molybdenum oxide are used, and phosphorus compounds include phosphoric acid or its salts, polymerized phosphoric acid or its salts, and thallium, vanadium, and copper. As the compounds, nitrates, sulfates, carbonates, organic acid salts, halides, oxides, etc. are effectively used.

These raw material compounds are made into a liquid or slurry using a solvent such as water, mixed as uniformly as possible, and then the solvent is evaporated to dryness on a sand bath at 100 to 150°C.

The cake-like material obtained is dried, preferably for 25 minutes.
After firing at 0 to 400°C for 1 to 10 hours, the obtained solid is pulverized.

This is compressed into a tufflet, or the powder is calcined in air at 350 to 500°C for 1 to 20 hours to obtain a catalyst.

Although the above catalyst of the present invention is extremely effective without a carrier, it is more convenient to support it on a carrier, and silica gel, silica sol, alumina, alumina silicate, silicon carbide, diatomaceous earth, titanium oxide, etc. are used as the carrier. Ru.

The methacrolein raw material used in the present invention does not need to be pure methacrolein, but methacrolein obtained by oxidizing imbutylene with air over a catalyst,
A mixed gas containing unreacted imbutylene, carbon oxide, carbon dioxide, nitrogen gas, water vapor, etc. may be used.

Similarly, the oxygen source used may be pure oxygen, but air is generally used.

Alternatively, a gas obtained by diluting oxygen with an inert gas such as carbon dioxide or nitrogen may be used.

Suitable reaction temperatures for the reaction conditions using the catalyst of the present invention are:
Although it varies depending on the catalyst, raw material gas composition, space velocity, etc., the temperature normally used for this type of reaction, i.e. 20
The temperature is 0 to 450°C, preferably 250 to 400°C.

Furthermore, although the present invention can be carried out either under pressure or reduced pressure,
It is convenient to carry out under normal pressure.

Space velocity is 100-12000 hr-1, preferably 2
It is 50 to 6000 hr-1.

The raw material gas composition is 0.1 to 10 mol% methacrolein, 01 to 20 mol% oxygen, and 0 to 90 mol% water vapor, preferably 10 to 80 mol%.

The coexistence of water vapor in the raw material mixed gas is extremely advantageous in terms of the yield of methacrylic acid, which is the target product.

The catalyst of the present invention is generally used in a fixed bed, but can also be used in a fluidized bed.

The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples.

In addition, the methacrolein reaction rate, methacrylic acid selectivity, and acetic acid selectivity in the present specification are defined as follows.

Gas chromatography was used as the analysis method.

Example 1 Ammonium molybdate 53. A solution prepared by dissolving 85% by weight of orthophosphoric acid (5.81ml) in 501ml of water was mixed with a solution containing 5.8ml of 85% by weight of orthophosphoric acid dissolved in 150ml of 10% ammonia water.

Next, a solution prepared by dissolving 4.41 parts of ammonium metavanadate and 70 parts by weight of a 10% by weight monoethanolamine aqueous solution was added thereto, and then a solution prepared by dissolving 4.71 parts of copper nitrate in 25 ml of water was mixed.

Next, add 134 grams of thallium nitrate to this mixture and add 10,011 grams of water.
The solution dissolved in No. 11 was mixed.

This mixed solution was evaporated to dryness on a sand bath at a temperature of 100 to 150°C, and the resulting solid was calcined in air at 300°C for 3 hours, and then pulverized.

Approximately 1% by weight of graphite was added to the thus obtained powder, which was then compressed into metallets with a diameter of 5 mm and a height of 5 mm, and the resulting tablets were fired in air at 400°C for 16 hours.

The catalyst thus completed has an atomic ratio (excluding oxygen) It has a composition of Mo12P2T12V1.5Cu1.

The catalyst 101111 prepared in this way was
Filled into a mrIt glass reaction tube, and the reaction temperature was 330°C.
, 1 mol% methacrolein at a space velocity of 500 hr',
A raw material gas having a composition of 1.6 mol % oxygen, 24 mol % nitrogen, and 73.4 mol % water vapor was brought into contact.

The results were that the methacrolein reaction rate was 90.3%, the methacrylic acid selectivity was 80.9%, and the acetic acid selectivity was 7.1%.

Examples 2 to 4 The reaction was carried out in the same manner as in Example 1, except that the atomic composition ratio of the catalyst system and the reaction temperature were varied, and the results shown in Table 1 were obtained.

Example 5 85% by weight of orthophosphoric acid in ion-exchanged water 11 50.45? Add and stir.

Next, 529.7f of ammonium molybdate was gradually added and dissolved, followed by 133.2f of thallium nitrate. Add and dissolve.

Separately, ion exchange water 25011 heated to 80℃
A solution obtained by dissolving 52.5y of oxalic acid in 11, and gradually adding 22.75f of vanadium pentoxide, and 15.5y of copper nitrate in 15TL of ion-exchanged water. After adding the solution containing IP to the Mo-P mixture, heat while stirring.
Evaporate to dryness.

This dried product was calcined at 230°C for 4 hours and then further calcined at 380°C for 5 hours.

The catalyst thus produced has an atomic ratio (excluding oxygen) of Mo 12 Pl, 75 T12V1 cube-2
It has a composition of 5.

10 m4 of this catalyst was packed into a glass reaction tube with an inner diameter of 19 m7ffi, and the reaction temperature was 340°C and the space velocity was 2000 hr.
' methacrolein: oxygen: nitrogen: water vapor - 1:1
A raw material gas having a composition of 4:19:4 (molar ratio) was supplied.

As a result, the methacrolein reaction rate was 74.3%, the methacrylic acid selectivity was 81.4%, and the acetic acid selectivity was 5.6%.

Claims (1)

[Claims] 1. In producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen or molecular oxygen-containing gas, the empirical formula [where a, b, c, d, and e are each phosphorus] is used. , the number of atoms of thallium, vanadium, copper and oxygen, and when the number of atoms of molybdenum is fixed to 12, a-0,1 to 1
6, b=0.01-16, C=0.01-12, d=0
．． 01 to 16, and e is a number naturally determined by the valence of other elements and the values of a to d.