JPH085835B2 - Method for producing acrolein - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing acrolein by a gas phase catalytic reaction of propylene.

More specifically, a coated catalyst prepared by coating the surface of an inert carrier with a metal oxide powder having a specific composition and prepared by controlling its specific surface area within a certain range. It relates to a method for producing acrolein by vapor-phase catalytic oxidation of propylene.

<Prior Art> It is known to produce acrolein by a gas phase catalytic reaction of propylene, and a large number of catalysts have been provided.

These are bismuth molybdate (Japanese Patent Publication No. 36-356).
3), the oxides of Mo / Bi-Fe (Japanese Patent Publication No. 39-3670) are the basic components, and in many cases various metal element components are added.

Further, regarding the shape of the catalyst to be used, a tableting catalyst (Japanese Patent Publication No. 51-47684), an extrusion catalyst (Japanese Patent Publication No. 47-38441), a coated catalyst (Japanese Patent Laid-Open No. 53-146288) and the like have been proposed.

It is said that it is advantageous to use a coated catalyst for a reaction involving heat generation such as a gas phase catalytic reaction of propylene because of problems such as heat removal.

We investigated the shape and reactivity of the catalyst and obtained the following results.

That is, a comparison was made between a tablet-molded catalyst powder having the same metal component and a catalyst coated on an inert carrier, and even a tablet-molded catalyst having a high activity had a low activity when used as a coated catalyst. Therefore, the result that the coated catalyst is advantageous is not necessarily obtained.

As a method for producing a coated catalyst, there is a technique disclosed in Japanese Patent Publication No. 56-28180.

According to the above-mentioned publication, first, an oxide powder of a molybdenum (Mo) -bismuth (Bi) -iron (Fe) -cobalt (Co) system is first pre-fired at a temperature of 450 to 500 ° C. Then, this metal oxide is pulverized to a powder of 400 μm or less, and this is coated on an inert carrier selected from alumina, diatomaceous earth, etc. with an aqueous solution of glucose or organic acid as an adhesive. The coated catalyst is further subjected to an initial calcination at a temperature of 450 to 500 ° C., then once cooled to an ambient temperature, and then a second calcination is again performed at a temperature of 450 to 500 ° C. It is a method for producing an α, β-unsaturated aldehyde with a catalyst coated with a metal oxide having a specific crystal structure and having a specific surface area of the active phase of 4 to 10 m ² / gr.

According to the reaction example using the above coated catalyst, the yield of acrolein is about 80% in the propylene conversion rate range of 91.5 to 96.5%, which is not satisfactory as a method for industrially producing acrolein. .

As a result of earnest studies on the development of a highly active catalyst without impairing the heat removal advantage of the coated catalyst, the present inventors have found that the molybdenum (Mo) -bismuth (Bi) -iron (Fe) -cobalt (Co ) Is further added with thallium (Tl) to control the oxide catalyst powder so that it has a specific surface area above a certain value, and a coating showing excellent activity when industrially producing acrolein. Succeeded in developing a catalyst.

<Means for Solving the Problems> That is, the present invention provides that “when propylene is oxidized with molecular oxygen to produce acrolein, five elements of molybdenum, bismuth, iron, cobalt and thallium are used as metal components. :
0.5 to 10: 1 to 10: 1 to 10: 0.01 to 0.5, which is a metal oxide having an atomic ratio of 10 to 20 m ² / g and has a specific surface area of the metal oxide, coated on an inert carrier. The method for producing acrolein is characterized in that the coated catalyst produced by

The method for producing acrolein of the present invention will be described in detail below.

The characteristics of the catalyst used in the acrolein production method of the present invention are that the metal components are molybdenum (Mo), bismuth (Bi),
A metal oxide powder composed of iron (Fe), cobalt (Co) and thallium (Tl) and having a specific surface area within a certain range is coated on the surface of a carrier to form a coated catalyst.

As the carrier that can be used, those which are inert to the reaction are advantageous, and silica, alumina, alumina-silica, silicon carbide, titania, zirconia and the like which are commonly used as this type of carrier can be mentioned. .

Particularly preferred carriers are low specific surface area silica, alumina and silicon carbide.

The water absorption of the carrier is preferably as low as possible in order to facilitate the drying after coating.

Any type of carrier can be used regardless of whether it is a sphere or a pellet.

However, in consideration of workability, a spherical shape is advantageous, and a diameter of 1 to 10 mm is selected.

Further, it is advantageous that the surface of the carrier is a rough surface in order to enhance the adhesion of the catalyst powder.

The ratio of the metal components contained in the metal oxide catalyst used in the present invention is Mo: Bi: Fe: Co: Tl = 12: 0.5-10: 0.1-1 in atomic ratio.
It is 0: 0.1 to 10: 0.01 to 0.5.

If the metal atom ratio deviates from this range, the yield of acrolein which is the target compound decreases, which is not preferable.

Among the various metals, Tl has the effect of improving the yield of acrolein.

Oxygen contained in the catalyst is present in the form of a metal oxide or a metal salt in combination with each of the above metals.

Therefore, the amount of oxygen contained is inevitably determined by the atomic ratio and valence of the metal component, and is usually in the range of 38 to 81 corresponding to the numerical value of the metal atomic ratio.

If the specific surface area is less than 10 m ² / g even with the above metal composition, the yield of the desired acrolein will decrease under a certain reaction condition because the rate of propylene conversion will decrease.

When the reaction temperature is increased for the purpose of improving the yield of acrolein, the selectivity of acrolein is lowered, and the molybdenum (Mo) scattering rate in the catalyst component is increased, so that the catalyst life is shortened.

On the other hand, even if it is attempted to control the specific surface area to 20 m ² / g or more, it is difficult with this type of catalyst production method, and it is not necessary to increase it from the viewpoint of activity.

Having the metal atomic ratio and the numerical value of oxygen atoms, and
The catalyst used in the present invention having a specific surface area of 10 to 20 m ² / g is produced, for example, as follows.

First, an aqueous solution of a water-soluble molybdenum (Mo) compound [eg ammonium molybdate = (NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O] is added to a bismuth (Bi) compound [eg bismuth nitrate = Bi (N
_{O 3) 3 5H 2 O]} , cobalt (Co) compound [for example, cobalt nitrate _{= Co (NO 3) 2 ·} 6H 2 O], iron (Fe) compound [for example, ferric nitrate = Fe (NO _{3) 3} · 9H ₂ O] and thallium (Ti) compound [for example, thallium nitrate] are dissolved in an aqueous nitric acid solution, and this aqueous solution is added while stirring well.

In this case, the temperature is less than 60 ° C, preferably about 50 ° C, and the both are mixed.

When mixed at a temperature of 60 ° C. or higher, the numerical value of the specific surface area of the obtained catalyst powder becomes small.

Further, when the rate of adding the mixture aqueous solution is slow, the numerical value of the specific surface area becomes small.

Further, the numerical value of the specific surface area increases by vigorous stirring when adding the mixture aqueous solution.

For example, it can be carried out in an agitator equipped with a flat blade turbine rotating at a speed of 300 rpm or more.

In any case, the temperature, addition rate, and stirring conditions affect the control of the specific surface area, so it is necessary to carry out the mixing operation while considering these factors.

In order to increase the numerical value of the specific surface area, the conditions at the time of production may be set as follows.

That is, the temperature is low, the stirring is vigorous, the concentration is low,
Is.

The order in which the aqueous solution of each salt is added is not particularly related to the control of the numerical value of the specific surface area.

Water is removed by concentrating the slurry obtained by the reaction.

In this case, if the catalyst powder is concentrated for a long time, the specific surface area of the obtained catalyst powder becomes low, so it is preferable to concentrate the catalyst powder in a short time.

Since the concentration time varies depending on the conditions during mixing work, it is necessary to consider the conditions during mixing, but concentration for 8 hours or longer is not preferable.

 The cake obtained by concentration is dried at 100-160 ° C.

If the drying temperature is less than 100 ° C, it will take a long time to dry,
It is not preferable for industrial production.

On the other hand, if the drying temperature exceeds 160 ° C, decomposition of nitrate occurs during drying and the heat of decomposition accumulates heat, which is not preferable because nitrate disperses rapidly.

The obtained solid substance is heated to a temperature near 350 ° C. to be pyrolyzed.

 The solid obtained is ground for coating the carrier.

The particle size of the catalyst powder needs to be at least smaller than the particle size of the carrier used, and it is desirable that the particle size is substantially 250 μm or less.

The volume ratio of the catalyst powder to the carrier is 30 to 70%, preferably 40 to 60% [(catalyst powder volume) / (catalyst powder volume +
Carrier volume)].

As a method for coating the catalyst powder on the carrier, a general coating method is used, and as a particularly preferable method, there is a method described in JP-A-62-95141 already disclosed by the present inventors.

By adopting this method, the catalyst powder composed of the metal oxide is firmly adhered to the carrier, and preferable results are obtained.

In the above method, while blowing the drying air through the circumferential slit at the bottom, while applying the planetary motion that combines the orbital motion and the rotational motion to the granular simple substance, the powdery catalyst substance and the adhesive aqueous solution are It is a method in which the catalyst substance is coated on the carrier by spraying and the drying finish is performed simultaneously.

The adhesive used to attach the metal catalyst to the carrier is preferably water, polyvinyl alcohol aqueous solution, or the like.

A catalyst for acrolein production having high activity can be obtained by calcining the coated catalyst prepared as described above at a temperature of about 500 ° C. for several hours.

In the present invention, the reaction conditions for oxidizing propylene to produce acrolein can be those generally used in this field.

Specifically, the reaction temperature is 300.
370 ° C., propylene 4 to 10 mol%, air 26 to 66 mol%, and the remaining inert gas for 3 to 8 seconds.

The specific surface area of the catalyst powder was measured by a normal nitrogen adsorption method.

The instrument used for measuring the specific surface area of the catalyst was a Sorptomatic 1800 surface area measuring device manufactured by Carlo Erba.

Example -1 14.6 parts of bismuth nitrate _{Bi (NO 3) 3 5H 2} O] , and concentrated nitric acid 4.1
Parts and then dissolved by adding a mixture of water 41 parts, 36.4 parts of ferric nitrate _{Fe (NO 3) 3 · 9H} 2 O, cobalt nitrate Co (NO ₃₎ 69.8 parts
₂ · 6H ₂ O and added to 0.41 parts of thallium nitrate was dissolved, 5
Heated to 0 ° C.

63.5 parts of ammonium molybdate (NH ₄ ) ₆ Mo
The ₇ O ₂₄ · 4H ₂ O of 50 ° C. dissolved in water 158 parts of solution was added with good stirring.

After the addition was completed, the mixture was concentrated at 100 to 120 ° C for 30 minutes with stirring.

The obtained cake was dried at 150 ° C. and further heated to 350 ° C. to decompose the produced salt.

The obtained solid was pulverized (passed through 60 mesh) to obtain a catalyst powder.

As the coating apparatus, using a centrifugal fluidized coating granulator (Kurointo Sangyo Co., Ltd.), a carrier (alumina: 3 mm ^phi, absorptance 2.3%) 50 parts catalyst powder in 50 parts by using water as binder The coated catalyst thus obtained was calcined at 500 ° C. for 3 hours to obtain a catalyst.

The metal composition ratio of the catalyst powder of this catalyst is Mo ₁₂ Bi ₁ Co ₈ Fe ₃ T
The specific surface area was 18 m ² / g at i _0.05 .

60 ml of this catalyst was filled in a stainless steel reaction tube having an inner diameter of 27 mm, and a gas consisting of propylene: 6 oxygen: 7.8 water: 25 nitrogen: 61.2 (both above vol.%) Was supplied at a contact time of 5 seconds, Reaction temperature
The reaction was carried out at 350 ° C.

As a result, the yield of acrolein was 84.9% with a propylene conversion rate of 99.2%.

Comparative Example 1 was calcined in Example catalyst powder obtained in the -1 to about ^5mm φ × 3mm ^h 3 h at 500 ° C. After tabletting to be the size of, to obtain a catalyst.

This tableting catalyst was reacted under the same conditions as in Example-1. As a result, the propylene conversion rate was 93.2% and the acrolein yield was 7
The result was 7.1%.

Comparative Example-2 A catalyst powder was produced in the same manner as in Example-1.

However, the temperature of the salt solution was slowly increased to 80 ° C. for 2 hours.

The specific surface area of the obtained catalyst powder was 4.2 m ² / g.

This catalyst powder was coated under the same conditions as in Example-1, a coated catalyst was produced, and reacted under the same reaction conditions as in Example-1.

 The results are shown in Table-1.

Example-2. To 7. The catalyst powder was manufactured in the same manner as in Example-1. However, in order to change the specific surface area of the catalyst powder, the salt solution temperature, the addition rate, and the concentration time were changed to produce a catalyst powder having a moderate specific surface area, and the coated catalyst was prepared in the same manner as in Example-1. Was prepared and reacted under the same reaction conditions as in Example.

 The results are shown in Table-2.

Examples-8. To 11 Using the catalyst powder used in Example 5, the particle size of the carrier and the coating amount were changed, and the reaction was performed under the same reaction conditions as in Example-1.

 However, the reaction temperature was changed.

 The results are shown in Table-3.

Examples-10 to 15 A catalyst was produced in the same manner as in Example-1 except that the metal composition ratio was changed, and the catalysts were reacted under the same reaction conditions. The composition of the catalyst used in each example was as follows.

Example 10: Mo ₁₂ Bi ₁ Fe ₂ Co ₈ Ti _0.05 11: Mo ₁₂ Bi ₁ Fe ₄ Co ₈ Ti _0.05 12: Mo ₁₂ Bi ₁ Fe ₃ Co ₆ Ti _0.05 13: Mo ₁₂ Bi ₁ Fe ₃ Co ₁₀ Ti _0.05 14: Mo ₁₂ Bi _0.5 Fe ₃ Co ₈ Ti _0.05 15: Mo ₁₂ Bi _1.5 Fe ₃ Co ₈ Ti _{0.05 The} results are shown in Table-4.

Claims (1)

[Claims] 1. Five elements of molybdenum, bismuth, iron, cobalt and thallium are 12: 0.5 to 10: 1 to 10: 1 as metal components when propylene is oxidized with molecular oxygen to produce acrolein. ~ 10: 0.01 ~ 0.5 is a metal oxide having an atomic ratio of 10 to 20 m ² specific surface area of the metal oxide
A method for producing acrolein, which comprises using a coated catalyst produced by coating an inert carrier with a powder of / g.