KR830000881B1 - Preparation of methacrolein - Google Patents

Abstract

No content.

Description

Preparation of methacrolein

Results display of Example 1-4 and Reference Example 1-2 of the present invention.

The present invention relates to an improved method for producing methacrolein, and more particularly, to a method for preparing methacrolein by inhibiting a by-product of acetone by the gas phase (rapor phase) catalytic oxidation of isobutylene or t-butyl alcohol. .

In the gas phase catalytic oxidation of isobutylene or t-butyl alcohol for the production of methacrolein, the introduction of steam in the reaction system has been suggested to be easy to control the reaction and to increase the yield of methacrolein. ("Catalysts" in Ohara, vol. 19, pp. 157-163, 1977).

On the basis of the removal as described above, steam has typically been introduced in the reaction steam in large amounts of 6 moles or more, preferably 8 moles or more, per mole of isobutylene or t-butyl alcohol.

On the other hand, from an industrial point of view, the most important point regarding the use of methacrolein is to prepare methacrylic acid by vapor phase catalytic oxidation.

There are several means for such gas phase catalytic oxidation, including the supply of purified methacrolein to the reactor for the production of methacrylic acid (published in 1975 by Oda's number, Hydrocarbon Production, pages 115-117). ).

This method is said to be effective to avoid the resulting gas mixture reaching within the explosive composition range.

The inventors believe that introducing methacrolein without purification may adversely affect the potency of the catalyst for methacrylic acid production and may result in a decrease in the yield of methacrylic acid.

If gas phase catalytic oxidation of isobutyl or t-butyl alcohol can provide methacrolein with high purity or only very minor by-products, the reaction mixture containing methacrolein is prepared for methacrylic acid without intermediate purification steps. It can be introduced directly into the reactor.

In the gas phase catalytic oxidation of isobutylene or t-butyl alcohol to methacrolein, metal oxide catalyst compositions of molybdenum and bismuth are frequently used.

In such cases, in addition to other by-products such as carbon monoxide, carbon dioxide and acetic acid, a few percent amount of acetone is always produced as a by-product.

Among the various by-products, acetone has an undesirable effect on the gas phase oxidation of methacrolein, especially in the presence of mixed oxide catalysts containing molybdenum or heteropolymolybdate catalysts.

Therefore, the removal or reduction of acetone from methacrolein containing products has been required in using methacrolein as a starting material for methacrylic acid production.

Extensive studies to inhibit acetone by-products have shown that the introduction of large amounts of steam, which has been removed as a necessity, into the reaction system as a diluent is rather undesirable to raise acetone by-products and the amount of vapor introduced below certain limits. Regulation was found to significantly reduce the amount of acetone by-products.

The accompanying drawings showing various results of substituting some carbon dioxide for vapor to be introduced as a diluent into the reaction system for the gas phase catalytic reaction of isobutylene producing methacrolein are described in Examples 1 to 4 as described below. The results obtained in Examples 1 to 2 are distinguished from each other. In the graph of the drawing, the horizontal axis shows the composition of the gaseous mixture as isobutylene: air: steam: carbon dioxide = 1: 15: X: Y (in molar ratio) and X. When changed under the condition of + Y = 8, the X value is indicated, and the ordinate indicates the conversion and the yield, and the curves (1) to (4) indicate the conversion of isobutylene, the yield of methacrolein, and the acetone, respectively. Selectivity for and acetic acid.

As shown in the above figures, the amount of acetone produced by-products is significantly reduced when the amount of vapor to be introduced into the reaction system is 4 mol or less per mol of isobutylene.

It can also be seen that in this case the use of steam at this ratio can simultaneously reduce the amount of acetic acid produced as a by-product and increase the yield of methacrolein.

When t-butyl alcohol is used instead of isobutylene, the following general formula:

Based on 1 mole of water per 1 mole of t-butyl alcohol is produced. Therefore, the amount of vapor introduced may be 3 moles or less per mole of t-butyl in order to reduce the amount of acetone produced by-products.

In order to suppress the amount of acetone produced as a by-product according to the present invention, the amount of vapor in the gaseous mixture is not more than 4 mol per mol of isobutylene or not more than 3 mol per mol of t-butyl alcohol so that isobutylene or t By gas phase catalytic oxidation of isobutylene or t-butyl alcohol by contacting a gaseous mixture of butyl alcohol, molecular oxygen and steam with a metal oxide catalyst composition of molybdenum and bismuth as an essential metal component An improved method for producing methacrolein is provided.

The catalyst used in the process of the present invention is a metal oxide catalyst composition of molybdenum and bismuth as an essential metal component. Particularly effective are metal oxide catalyst compositions comprising molybdenum, bismuth and iron as essential metal components. Therefore, a metal oxide catalyst composition composed of a metal component or the like corresponding to the following general formula is used as an appropriate one.

Mo-Bi-Fe-X-Y-Z

Wherein X is at least one of Ni, Co, Mg, Mn, Cr, W, Sn and Cu, Y is at least one of P, Sb, B and Te, Z is K, Rb, Cs and Tl, and Y And Z are optional.

Generally the catalyst is used together with a carrier which is for example silica, alumina, titania, zirconia and the like.

These metal oxide catalyst compositions and carriers are well known and conventional.

The gaseous mixture as starting material consists of isobutylene or t-butyl alcohol, molecular oxygen and steam.

The molar ratio between isobutylene or t-butyl alcohol and molecular oxygen is 1: 2.0-4.5.

As described above, the vapor is preferably 4 moles or less, preferably 3 moles or less, per mole of isobutylene and 3 moles or less per mole of t-butyl alcohol. Shall use 2 moles or less. Lower limit of vapor volume is irrelevant and any trace amount of steam can be used.

When t-butyl is used, water is produced in the reaction system, thereby eliminating the need for any intentional incorporation of vapor into the gaseous mixture.

That is, t-butyl alcohol is actually equivalent to isobutylene and molar amounts of animal in the reaction system of the method according to the present invention.

In more detail, t-butylalcohol forms an azeotrope of water with a molar ratio of about 1: 1.1.

Such azeotrope is available at low cost compared to pure t-butyl alcohol and its use is desirable from an industrial point of view.

Instead of using only isobutylene or t-butyl alcohol, these

Mixtures may be used.

In this case, the amount of molecular oxygen or vapor to be used will be the total amount determined for isobutylene or t-butyl alcohol, respectively, based on the above proportions.

The presence of small amounts of methane, propane and saturated hydrocarbons such as butane or carbon monoxide in the gaseous mixture does not really interfere with catalytic oxidation.

In industrial application of the process of the invention, the gaseous mixture should be stored outside the explosive composition range.

In order to ensure this, an inert gas such as nitrogen or carbon dioxide may be incorporated into the gas phase mixture as a diluent. The use of carbon dioxide among various inert gases is desirable because of its large specific heat.

Advantageously, carbon dioxide is readily available at low prices because it is contained in large quantities in the emissions of various chemical plants.

Since carbon dioxide as a diluent can contain nitrogen and some other inert gases such as small amounts of oxygen and carbon monoxide, it is possible to use it from equipment such as furnaces or boilers that use clean fuels that do not contain any sulfuric acid-containing substances. Can be used as a diluent.

Exhaust gases from the reactor for gas phase catalytic oxidation of isobutylene or t-butyl alcohol may also be used as diluents.

Such inert diluent gases other than steam can be used in a molar ratio of 10 to 40 moles per mole of isobutylene or butyl alcohol and in a molar ratio of 3.8 to 10 moles per mole of molecular oxygen.

The reaction temperature is usually 300 to 450 ° C.

The space velocity of the gaseous mixture as starting material is usually between 500 and 6000 hr ⁻¹ .

The pressure in the reactor is preferably about atmospheric pressure, in particular instrument pressure 4 kg / cm 2 or less.

The methacrolein thus produced is further reduced in the amount of acetone and acetic acid in contamination and can be used as a starting material for methacrylic acid production.

In other words, the present invention isothermally reacts isobutylene or t-butyl alcohol via methacrolein to oxidize the methacrolein to methacrylic acid so that the continuous production of methacrylic acid can be accomplished without any intermediate purification steps. Reactor isobutylene or t-butyl alcohol to oxidize methacrolein to methacrylic acid so that the continuous production of methacrylic acid from butylene or t-butyl alcohol via methacrolein can be accomplished without any intermediate purification steps. Allow direct connection to the reactor which oxidizes to methacrolein.

In addition, the method of the present invention is effective in increasing the yield of methacrolein and improving the potency of the catalyst.

Through this specification, the conversion of isobutylene or t-butyl alcohol, yield of methacrolein, selectivity for acetone and selectivity for acetic acid are calculated by the following equation:

Practical and presently preferred embodiments of the present invention are clearly indicated in the following examples and the like.

[Example 1-4 and Reference Example 1-2]

Bismuth nitrate (12.13 g) is dissolved in a mixture of concentrated nitric acid (60% by weight; 4 ml) and water (30 ml) and ferric nitrate (20.20 g), cobalt nitrate (29.12 g), nitric acid in water (250 ml) Nickel (36.42) and thallium nitrate (3.33 g) were added to the solution.

A solution obtained by dissolving ammonium paramolybdate (52.98 g) in a mixture of aqueous ammonia (28% by weight; 30 ml) and water (300 ml) in the resulting mixture and adding phosphoric acid (85% by weight; 0,95 g) Was added to obtain a suspension.

Silica sol (100 ml) containing 20% of SiO ₂ by weight was added to the suspension and stirred vigorously.

The resulting suspension was evaporated to dryness. The residue was then calcined in air at 300 ° C. for 3 hours, cooled and crushed.

The crushed product thus obtained was made into tablets using a tablet machine and these tablets were calcined at 550 ° C. for 6 hours.

The catalyst thus prepared had the following composition:

Mo ₁₂ Bi ₁ Fe ₂ Ni ₅ Co ₄ Tl ₀ P _0.4 O _50.8 15SiO

The catalyst was powdered to mix particles of 24-32 mesh size (2 g) with molten alumina (alandom) (24-32 mesh: 18 ml). This mixture was placed in a ceramic reactor with an inner diameter of 15 mm.

The reactor was heated in an electric furnace and the temperature of the catalyst bed was adjusted to 380 ° C.

A gaseous mixture with a composition as indicated in the first table was fed into the reactor at a space velocity of 5000 hr ⁻¹ . The results are shown in the first table and in the drawings of the accompanying drawings.

In the figure, the horizontal side represents the molar ratio of steam to isobutylene, and the ordinate represents conversion and yield.

Curves (1) through (4) show conversion of isobutylene, yield of methacrolein, selectivity for acetone and selectivity for acetic acid, respectively.

[Table 1]

Example 5

The reaction was carried out as in Example 1 except using a gaseous mixture having a composition of isobutylene: air: nitrogen: steam = 1: 15: 6: 2 (molar).

The results are as follows: conversion of isobutylene 92.6%: yield of methacrolein 82.6%: selectivity for acetone 1.9%: selectivity for acetic acid 1.8%.

Comparing this example with Example 2, the results are practically the same. And it can be seen that using carbon dioxide as the diluent gives practically the same results as using nitrogen as the diluent.

4의 범위 이내에 유지하는데 기인한다.That is, the effect of decreasing the yield of acetone shown in Example 1-4 is not due to the use of carbon dioxide as the diluent, and the amount of steam is H ₂ O / isobutylene.

It is due to keeping within the range of 4.

Example 6

The same catalyst (10 ml) as used in Example 1 was placed in a ceramic reactor having an inner diameter of 15 mm and heated in an electric furnace to adjust the temperature in the catalyst at 360 ° C.

Subsequently, a gaseous mixture with a composition of isobutylene: air: carbon dioxide: steam = 1: 15: 6: 2 (moles) was fed into the reactor at a space velocity of 1500 hr ^_1 and the reaction was carried out continuously for 61 days.

The results after 1 day from the start of the reaction were as follows:

Isobutylene 98.7%: yield of methacrolein 81.7%: selectivity to acetone 2.7%.

The results after 61 days from the start of the reaction were as follows:

Isobutylene 98.5%: Methacrolein yield 82.3%: Selectivity to acetone 2.7%.

These results are shown in the second table along with the results at the other stages.

Based on the above results, the relationship between the number of days after initiation of reaction (X) and the result obtained is represented by the following equation based on the method of least provision.

% Conversion of isobutyrene = 98.6-0.006X (γ = -0.31).

Yield of methacrolein (%) = 81.8 + 0.01X (γ = + 0.56)

Is the correlation coefficient between the number of days after the start of the reaction and the result obtained.

The correlation coefficient of isobutylene conversion is -0.31 and the correlation with the inhibition of activity is considered to be low.

[Table 2]

Example 7

Bismuth nitrate (12.13 g) was dissolved in a mixture of concentrated nitric acid (60% by weight; 4 mol) and mol (30 ml).

Then, a solution containing ferric nitrate (101.0 g), cobalt nitrate (29.12 g), nickel nitrate (36.42 g) and thallium nitrate (3.33 g) was added to water (350 ml).

A solution obtained by dissolving ammonium paramolybdate (52,98 g) in a mixture of aqueous ammonia (29% by weight; 30 ml) and water (300 ml), and adding phosphoric acid (85% by weight; 1.15 g) by weight And stirred to obtain a suspension.

To this suspension was added silica gel (100 ml) containing 20% SiO ₂ by weight and stirred vigorously.

The resulting suspension was evaporated to dryness and the residue calcined in air at 300 ° C. for 3 hours, then cooled and crushed.

The resulting crushed product was made into tablets using a refiner. These tablets were then calcined at 550 ° C. for 6 hours.

The catalyst prepared in this way had the following composition.

Mo ₁₂ Bi ₁ Fe ₁₀ Ni ₅ Co ₄ Tl _0.5 P _0.4 O _62.8 15SiO ₂

The catalyst was powdered to mix particles of 24-32 mesh size (2 g) with molten alumina (alandom) (24-32 mesh; 18 ml). This mixture was placed in a ceramic reactor with an inner diameter of 15 ml.

The reactor was then heated in an electric furnace and a gaseous mixture with a composition of isobutylene: air: nitrogen: steam = 1: 15: 6: 2 (molo) was fed at a space velocity of 5000 hr ^-1 . The temperature in the reactor was adjusted to a maximum of 420 ° C. and the reaction was run over 14 consecutive days.

The results after 1 day from the start of the reaction are as follows:

100% conversion of isobutylene; Yield of methacrolein 82.4%.

The results after 14 days from the start of the reaction are as follows:

Conversion of isobutylene 99.4%; Yield 82.5% of methacrolein.

Based on the results 4 and 7 days after the start of the reaction and the above result, the relationship between the number of days after the start of reaction (X) and the result obtained is expressed by the following equation based on the least square method.

Conversion of isobutylene (%) = 99.9-0.045X (γ = -0.82)

Yield of methacrolein (%) = 82.1 + 0.023 X (γ = + 0.43)

Where γ is the correlation between the number of days after the start of the reaction and the result obtained.

And the selectivity to acetone is always 0.8%.

Example 8 and Reference Example 3

Except for using potassium nitrate (0.51 g) instead of thallium nitrate, the material for preparing the catalyst was mixed together as in Example 1. The resulting suspension was evaporated to dryness. The residue was then calcined in air at 300 ° C. for 3 hours and then cooled and crushed.

The resulting crushed product was made into tablets using a refiner and the tablets were calcined at 550 ° C. for 6 hours. The catalyst thus prepared has the following composition;

Mo ₁₂ Bi ₁ Fe ₂ Ni ₅ Co ₄ K _0.2 P _0.4 O _50.6. 15 SiO ₂

The catalyst was powdered to mix particles of 24-32 mesh size (4.0 g) with molten alumina (alandom) (24-32 mesh; 18 ml). This mixture was placed in a ceramic reactor with an inner diameter of 15 ml.

The reactor was heated in an electric furnace and a gaseous mixture having a composition as indicated in Table 3 was fed into the reactor at 2500 hr ^-1 space velocity.

The temperature of the catalyst layer was adjusted to 370 ° C.

The results are shown in FIG.

Example 9-18 and Reference Example 4-5

As in Example 1, the following composition:

Mo ₁₂ Bi ₁ Fe ₂ Ni ₉ O _49.5. 15SiO ₂ and _{Mo 12 Bi 1 Fe 1 Co 7} K 0.14 O 46. A catalyst was prepared having the 10SiO _2.

The calcining temperature of this catalyst was 650 degreeC and 600 degreeC, respectively.

As in Example 8, the reaction was carried out at a space velocity of 2500 hr ⁻¹ .

The results are shown in Table 3.

[Table 3]

Example 11

As in Example 1, the materials for preparing the catalyst were mixed together. The resulting suspension was evaporated to dryness and the residue was calcined in air at 300 ° C. for 3 hours, then cooled and crushed to yield the following composition:

Mo ₁₂ Bi ₁ Fe ₂ Ni ₅ Co ₄ Tl _0.5 P _0.4 O _50.8. 15 SiO ₂

Particles were obtained. The particles were attached to the surface of a spherical carrier (main component α-alumina) having a diameter of about 5 mm while rotating by spraying water using a dish granulator, dried and calcined in an atmosphere of 550 ° C. for 6 hours. .

The catalyst thus obtained retains 30% of the active ingredient by weight and has a spherical shape of about 5 mm in diameter. This catalyst (12 ml) was placed in a ceramic reactor having an inner diameter of 15 mm and heated to 420 ° C. in an electric furnace.

The reaction was carried out by feeding a gaseous mixture having a composition of isobutylene: air: carbon dioxide: nitrogen: steam = 1: 20: 2: 5: 1 (molo) into the reactor at a space velocity of 1500 hr ⁻¹ .

The result is as follows:

Conversion of isobutylene 92.0%; Yield of methacrolein 77.1%; 2.7% selectivity to acetone; 2.3% selectivity to acetic acid.

Example 12

The same catalyst (12 ml) as used in Example 11 was placed in a ceramic reactor with an inner diameter of 15 mm and heated to 420 ° C. using an electric furnace.

A gaseous mixture with a composition of t-butyl alcohol: air: nitrogen: steam = 1: 20: 7: 0.1 (moles) was fed into the reactor at a space velocity of 1500 hr ⁻¹ .

the results are as follow.

100% conversion of t-butyl alcohol; Yield of methacrolein 77.8%; 2.3% selectivity to acetone; Selectivity to acetic acid 2.1%.

Example 13

The reaction was carried out in the same manner as in Example 12 except for using t-butyl alcohol, which was broken together instead of pure t-butyl alcohol.

The composition of the gaseous mixture fed into the reactor was t-butyl alcohol: air: nitrogen: steam = 1: 20: 7: 0.1 (in moles).

The result is as follows:

100% conversion of t-butyl alcohol; Yield of methacrolein 77.3%; 2.5% selectivity to acetone; Selectivity to acetic acid 2.1%.

Example 14

The reaction was carried out in the same manner as in Example 12 except that a gaseous mixture having a composition of t-butyl alcohol: air: nitrogen: steam = 1: 20: 7: 0.1 (moles) was used.

In this case, a small amount of water was added to the azeotropic t-butyl alcohol. That is, a mixture of t-butyl alcohol and water in a molar ratio of 1: 3 was used as starting material.

The result is as follows:

100% conversion of t-butyl alcohol; Yield of methacrolein 76.0%; 2.8% selectivity to acetone; 2.4% selectivity to acetic acid.

Claims (1)

In the production of methacrolein by gas phase oxidation of isobutylene t-butyl alcohol, the steam is not more than 4 mol per mol of isobutylene or not more than 3 mol per mol of t-butyl alcohol. Mo-Bi-Fe-XYZ, a metal oxide catalyst composition of molybdenum and bismuth as an essential metal component with a gaseous mixture of butylene or t-butyl alcohol, molecular oxygen and steam, wherein X is at least Ni, Co, Mg, Mn, Cr, W, Xn or one of Cu, Y is at least one of P, Sb, B and Te, and Z is at least one of K, Rb, Cs and TL, and the presence of Y or Z Optional), but the method of methacrolein to suppress the amount of acetone produced as a by-product at a temperature of 300-450 ℃, instrument pressure 4kg / ㎠ or less at a space velocity of 500.-6000hr ^-1 .

Images