JP2809476B2 - Method for producing acrolein and acrylic acid - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing acrolein and acrylic acid by subjecting propylene to gas-phase catalytic oxidation with molecular oxygen or a molecular oxygen-containing gas.

(Prior Art) Many proposals have been made regarding catalysts used for producing acrolein and acrylic acid by subjecting propylene to high-temperature gas-phase oxidation. These are mainly concerned with the selection of the components constituting the catalyst and the ratio thereof.

Since the above-mentioned oxidation reaction is a reaction accompanied by an extremely exothermic reaction, the heat storage in the catalyst layer is large, and particularly in a local abnormally high temperature zone called a hot spot, not only the yield decreases due to the excessive oxidation reaction but also the heat load. The catalyst life is greatly affected by the deterioration of the catalyst. For this reason, in industrial practice, heat storage in the hot spot becomes a serious problem, especially when the starting material concentration is increased or the space velocity is increased in order to increase productivity (hereinafter referred to as “high load reaction conditions”). However, since the heat storage in the hot spot tends to be remarkable, the reaction conditions are considerably restricted at present.

Therefore, suppressing the heat storage in the hot spot portion is not only for industrially producing acrolein and acrylic acid with high yield, but also for enabling stable operation for a long period of time by suppressing catalyst deterioration. It is very important. In particular, in the case of a molybdenum-based catalyst, it is important to prevent heat storage at the hot spot portion because the molybdenum component is easily sublimated.

Some proposals have been made in the past as a method of suppressing heat storage in a hot spot. For example,
No. 36740 proposes that the shape of the catalyst be ring-shaped. This publication discloses that the heat storage at the hot spot portion is changed by changing the shape from a spherical or cylindrical shape to a ring shape in a molded catalyst usually used as a catalyst for oxidizing propylene or isobutylene and / or t-butanol. It is stated that the suppression of excessive oxidation reaction has a great effect on the improvement of the yield. However, although this method has the effect of reducing the heat load, it cannot be said that sufficiently satisfactory results can be obtained, especially under high load reaction conditions.

In addition, the catalyst layer is divided to provide multiple reaction zones,
A method of filling a plurality of reaction zones with catalysts having different activities and subjecting them to an oxidation reaction is also known as a method for producing acrolein and acrylic acid from propylene, for example, as disclosed in
No. 38331 is known.

However, in this catalyst, the activity is controlled by changing the amount of the alkali metal added. However, as can be seen from the fact that the amount of the alkali metal component added is very small as compared with the other components, the effect of the addition is reduced. Extremely large. For this reason, great care must be taken in the preparation of the catalyst, and it cannot always be said that the catalyst is practical and appropriate in terms of controlling the catalytic activity.

JP-A-51-227013 discloses a method for producing an unsaturated aldehyde and an acid from propylene and isobutylene, which is a combination of a supported catalyst having essentially the same composition and a molded catalyst.

This catalyst system is also not sufficiently satisfactory for use in industrial practice.

(Problem to be Solved by the Invention) One object of the present invention is to provide a method for producing acrolein and acrylic acid in high yield by subjecting propylene to gas phase catalytic oxidation.

Another object of the present invention is to suppress the heat storage in the hot spot portion in the catalyst layer when producing acrolein and acrylic acid by gas phase catalytic oxidation of propylene, while improving the yield of acrolein and acrylic acid. An object of the present invention is to provide a method for producing acrolein and acrylic acid, which prevents deterioration of the catalyst and enables the catalyst to be used stably for a long time.

Another object of the present invention is to suppress the heat storage at the hot spot portion in the catalyst layer when producing acrolein and acrylic acid by subjecting propylene to gas phase catalytic oxidation under high-load reaction conditions, and to recover acrolein and acrylic acid. It is an object of the present invention to provide a method for producing acrolein and acrylic acid, which aims to improve the rate and prevent catalyst deterioration so that the catalyst can be used stably for a long period of time, and further increase productivity.

(Means for Solving the Problems) The present inventors prepared a plurality of specific molybdenum-based catalysts having different activities, and provided a plurality of reaction zones by dividing a catalyst layer into two or more layers. It was found that the above object can be achieved by filling a plurality of reaction zones with a plurality of molybdenum-based catalysts having different activities from the raw material gas inlet to the outlet so that the activity becomes higher. Thus, the present invention has been completed.

That is, the present invention relates to a method for producing acrolein and acrylic acid by gas-phase catalytic oxidation of propylene with molecular oxygen or a gas containing molecular oxygen using a fixed-bed multitubular reactor. General formula (I) Mo _a W _b Bi _c Fe _d A _e B _f C _g D _h E _i O _x (wherein, Mo is molybdenum, W is tungsten, Bi is bismuth, Fe is iron, A is nickel and cobalt. B is at least one element selected from alkali metals and thallium, C is at least one element selected from alkaline earth metals, D is phosphorus, tellurium, antimony, tin, cerium And at least one element selected from lead, niobium, manganese, arsenic and zinc, and E is at least one selected from silicon, aluminum, titanium and zirconium. Seed elements, O represents oxygen, also a, b, c, d, e, f,
g, h, i and x are Mo, W, Bi, Fe, A,
Represents the number of atoms of B, C, D, E and O, and when a = 12, b = 0 to 10, c = 0.1 to 10, d = 0.1 to 20, e = 2
-20, f = 0-10, g = 0.001-10, h = 0-4, i =
0-30, x = value determined by the oxidation state of each element). (B) The catalyst layer in each reaction tube is divided into two or more layers in the tube axis direction. In the plurality of reaction zones provided, (c) a plurality of catalysts having different activities prepared by changing the type and / or amount of the group C element in the general formula (I) in the catalyst of the above (a); The present invention relates to a method for producing acrolein and acrylic acid, which is filled so that the activity becomes higher from a gas inlet to an outlet.

 Hereinafter, the present invention will be described in detail.

The catalyst used in the present invention is a composite oxide represented by the general formula (I). The method for preparing the catalyst and the raw materials are not particularly limited, and the catalyst can be prepared using the methods and raw materials generally used for preparing this type of catalyst.

In the present invention, a plurality of catalysts having different activities represented by the general formula (I) are prepared, and the plurality of catalysts are packed in a specific sequence. ) Can be easily prepared by changing the type and / or amount of the group C element. That is, the type and / or amount of at least one element selected from alkaline earth metals such as beryllium, magnesium, calcium and strontium (within the atomic ratio defined by g in the general formula (I)) is changed. As a result, catalysts having different activities can be obtained.

The catalyst used in the present invention is composed of the elemental components represented by the general formula (I), and the object of the present invention is achieved by a combination of these elemental components.
In particular, the tungsten component is effective for improving the catalytic activity,
When this is used in combination with the group C element, a remarkable improvement in the catalytic activity can be observed without lowering the selectivity of the catalyst. When the molybdenum component is 12, the addition ratio of the tungsten component is 0 to 10, preferably 0.5 to 10.

In the present invention, "activity" means the conversion of the starting material.

The catalyst used in the present invention may be molded by a usual molding method, for example, an extrusion molding method or a tablet molding method, and a composite oxide represented by the general formula (I) as a catalyst component is carbonized. It may be supported on an inert carrier generally used as a carrier, such as silicon, alumina, zirconium oxide, and titanium oxide.

The shape of the catalyst used in the present invention is not particularly limited, and may be any of a sphere, a column, and a ring. In particular, when a ring-shaped catalyst is used, heat storage in the hot spot portion is prevented, and various advantages such as a reduction in pressure loss in the catalyst layer as well as an improvement in yield and prevention of catalyst deterioration are obtained. In the present invention, a ring catalyst is preferably used. As a ring-shaped catalyst, the outer diameter is 3 to 10 mm,
A ring-shaped catalyst having a length of 0.5 to 2 times the outer diameter and an inner diameter of the through hole in the length direction of 0.1 to 0.7 times the outer diameter is suitably used.

In the present invention, the catalyst layer in each reaction tube is divided into two or more layers in the tube axis direction to provide a plurality of reaction zones, and a plurality of catalysts having different activities are supplied to the reaction zones from the inlet of the raw material gas. It arrange | positions so that activity may become high sequentially toward an exit part. That is, the catalyst with the lowest activity is located at the inlet, while the catalyst with the highest activity is located at the outlet. By arranging a plurality of catalysts having different activities in this manner, heat storage in the hot spot portion can be suppressed, and the target product can be obtained with a high selectivity.

As the number of the catalyst layers is increased, the temperature distribution of the catalyst layers is more easily controlled. However, industrially, the desired effect can be sufficiently obtained by using two to three layers. Also,
Since the splitting ratio depends on the composition, shape, etc. of the catalyst of each layer, it cannot be specified unconditionally,
What is necessary is just to select suitably so that the optimal activity and selectivity as a whole may be obtained.

The gas phase catalytic oxidation reaction in the present invention may be an ordinary single flow method or a recycling method, and can be carried out under conditions generally used for this type of reaction. For example, a mixed gas composed of 1 to 10% by volume of propylene, 3 to 20% by volume of molecular oxygen, 0 to 60% by volume of steam, 20 to 80% by volume of an inert gas such as nitrogen and carbon dioxide gas is applied on the catalyst by 250%. It is introduced at a space velocity of 300 to 5000 hr ^-1 (STP) under a temperature range of ~ 450 ° C, a pressure of normal pressure ~ 10 atm.

According to the method of the present invention, under a high load reaction condition for the purpose of increasing productivity, for example, under a condition of a higher raw material concentration or a higher space velocity, particularly remarkable good results are obtained as compared with the conventional method. can get.

(Effect of the Invention) In the present invention, a plurality of specific molybdenum-based catalysts having different activities are packed into a plurality of divided catalyst layers so that the activity becomes higher from the raw material gas inlet toward the outlet. (A) acrolein and acrylic acid can be obtained at a high yield; (b) heat storage at the hot spot can be effectively suppressed; and (c) excessive oxidation reaction at the hot spot can be prevented, resulting in a high yield. (D) Deterioration of the catalyst due to heat load can be prevented, and the catalyst can be used stably for a long time. (E) High raw material concentration, high space velocity Even under high-load reaction conditions, the desired acrolein and acrylic acid can be obtained in high yield, so that the effects of greatly increasing productivity can be obtained.

Further, by using the ring-shaped catalyst, in addition to the above-described effects, there is also obtained an effect that (f) the power consumption can be reduced by reducing the pressure loss in the catalyst layer.

Therefore, the method of the present invention is a very useful method for industrial production of acrolein and acrylic acid.

(Examples) Hereinafter, the present invention will be described more specifically with reference to examples.

The conversion, selectivity and total single-stream yield are defined by the following equations.

Example 1 436 g of cobalt nitrate and 202 g of ferric nitrate were dissolved in 1000 ml of water. Also, 243 g of bismuth nitrate and 291 g of nickel nitrate
Was dissolved in an aqueous nitric acid solution of 30 ml of concentrated nitric acid and 120 ml of water.

Separately, while heating and dissolving 3000 ml of water, 1059 g of ammonium paramolybdate and 265 g of ammonium paratungstate are dissolved therein, and the two separately prepared aqueous solutions are dropped and mixed into the obtained aqueous solution, and then 5.8 g of cesium nitrate is added. And an aqueous solution obtained by dissolving 13.1 g of barium nitrate in 400 ml of water, and 203 g of a silica sol having a concentration of 20% by weight are sequentially added.
Mixed.

The suspension thus obtained was heated and stirred, evaporated to dryness, molded into a column having an outer diameter of 6 mm and a length of 3 mm, and calcined at 480 ° C. for 4 hours in an air stream to obtain a catalyst (1). ) Got. The composition of this catalyst (1) was Mo ₁₂ W ₂ Bi ₁ Fe ₁ Co ₃ Ni ₂ Cs _0.06 Ba _0.1 Si _1.35 in atomic ratio excluding oxygen.

Catalyst (2) was prepared in the same manner as in the preparation of catalyst (1) except that the amount of barium nitrate was changed to 65.3 g. The composition of this catalyst (2) was Mo ₁₂ W ₂ Bi ₁ Fe ₁ Co ₃ Ni ₂ Cs _0.06 Ba _0.5 Si _1.35 in atomic ratio excluding oxygen.

Regarding the activities of the catalysts (1) and (2), as is clear from the results of Comparative Examples 1 and 2 described later, the activity of the catalyst (2) is higher than that of the catalyst (1).

The raw material gas inlet of a 25.4 mm diameter steel reaction tube was filled with 750 ml of the above catalyst (1), while the raw material gas outlet was filled with 750 ml of the above catalyst (2).

A mixed gas having a composition consisting of 8% by volume of propylene, 14.1% by volume of oxygen, 25% by volume of steam and 52.9% by volume of nitrogen was introduced from the inlet of the reaction tube, and the reaction temperature was 310 ° C. and the space velocity was 1600 hours.
The reaction was performed at r ^-1 (STP). Table 1 shows the results.

Comparative Example 1 A reaction was carried out in the same manner as in Example 1, except that the catalyst (2) was not used and only the catalyst (1) was charged in an amount of 1500 ml. Table 1 shows the results.

Comparative Example 2 A reaction was carried out in the same manner as in Example 1 except that the catalyst (1) was not used and only the catalyst (2) was charged in an amount of 1500 ml. Table 1 shows the results.

Comparative Example 3 A catalyst (3) was prepared in the same manner as in the preparation of the catalyst (1) in Example 1, except that the amount of barium nitrate used was changed to 39.2 g. The composition of this catalyst (3) was Mo ₁₂ W ₂ Bi ₁ Fe ₁ Co ₃ Ni ₂ Cs _0.06 Ba _0.3 Si _1.35 in atomic ratio excluding oxygen.

The reaction was carried out in the same manner as in Example 1 except that only 1500 ml of the catalyst (3) was charged into the reaction tube. Table 1 shows the results.

From the results in Table 1, it can be seen that the activity of catalyst (1) is very low, whereas catalyst (2) has high activity but low selectivity, and all have low single-stream yields. ),
It is understood that the total single stream yield is high in the catalyst system of the present invention in which (2) is combined, and the desired acrolein and acrylic acid can be obtained in high yield.

Also, when comparing the catalyst (3) having an intermediate composition between the catalyst (1) and the catalyst (2) with the catalyst system of the present invention in which the catalysts (1) and (2) are combined, the catalyst (3) has a total Since the single stream yield is low and the temperature difference (ΔT) between the reaction temperature and the maximum temperature of the catalyst layer is very large, it is considered that catalyst deterioration due to heat load is remarkable. That is, it is understood that the effect of the present invention cannot be achieved even if a single catalyst (3) having a composition substantially the same as that of the catalyst system of the present invention is used alone.

Example 2 A catalyst (1) was prepared in the same manner as in Example 1 except that sodium hydroxide was used instead of cesium nitrate, calcium nitrate was used instead of barium nitrate, and only cobalt was used as a group A element. Catalyst (4) and Catalyst (5) were prepared in the same manner as in the preparation of (3).

The compositions of the catalysts (4) and (5) were as follows in terms of atomic ratio excluding oxygen.

Catalyst (4) Mo ₁₂ W ₂ Bi _1.2 Fe ₁ Co ₅ Na _0.1 Ca _0.2 Si _1.35 catalyst (5) Mo ₁₂ W ₂ Bi _1.2 Fe ₁ Co ₅ Na _0.1 Ca _0.6 Si _1.35 or less, catalyst (4) The reaction was carried out in the same manner as in Example 1 except that 750 ml of the raw material gas and 750 ml of the catalyst (5) were charged into the outlet of the raw material gas. Table 1 shows the results.

Comparative Example 4 A reaction was carried out in the same manner as in Example 2 except that the catalyst (5) was not used and only the catalyst (4) was charged in an amount of 1500 ml. Table 1 shows the results.

Comparative Example 5 The reaction was carried out in the same manner as in Example 2 except that the catalyst (4) was not used and only the catalyst (5) was charged in an amount of 1500 ml. Table 1 shows the results.

Comparative Example 6 A catalyst (6) was prepared in the same manner as in the preparation of the catalyst (4) except that the amount of calcium nitrate was changed in the preparation of the catalyst (4) in Example 2.

The composition of the catalyst (6) was Mo ₁₂ W ₂ Bi _1.2 Fe ₁ Co ₅ Na _0.1 Ca _0.4 Si _1.35 in atomic ratio excluding oxygen.

Thereafter, the reaction was carried out in the same manner as in Example 2 except that 1500 ml of the catalyst (6) was charged instead of the catalysts (4) and (5). Table 1 shows the results.

Example 3 In the preparation of the catalyst (1) of Example 1, potassium hydroxide was used instead of cesium nitrate, barium was added as a group C element, and strontium nitrate was used, in the same manner as in the catalyst (1). Catalyst (7) and catalyst (8) were prepared.

The compositions of the catalysts (7) and (8) were as follows in terms of atomic ratio excluding oxygen.

Catalyst (7) Mo ₁₂ W ₂ Bi ₁ Fe ₁ Co ₃ Ni ₂ K _0.06 Ba _0.1 catalyst (8) Mo ₁₂ W ₂ Bi ₁ Fe ₁ Co ₃ Ni ₂ K _0.06 Ba _0.4 or less, catalyst (7 The reaction was carried out in the same manner as in Example 1 except that 600 ml) and 900 ml of the catalyst (8) were charged into the outlet. Table 1 shows the results.

Comparative Example 7 A reaction was carried out in the same manner as in Example 3, except that only the catalyst (7) was used in an amount of 1500 ml. The results are shown in Table 1. Comparative Example 8 A reaction was carried out in the same manner as in Example 3, except that only the catalyst (8) was used in an amount of 1500 ml. Table 1 shows the results.

Comparative Example 9 The catalyst (7) in Example 3 was changed by changing the amount of barium.
In the same manner as in the above, catalyst (9) was prepared.

The composition of the catalyst (9) was _{Mo 12 W 2 Bi 1 Fe 1} Co 3 Ni 2 K 0.06 Ba 0.3 in atomic ratio excluding oxygen.

The reaction was carried out in the same manner as in Example 3, except that 1500 ml of the catalyst (9) alone was used. Table 1 shows the results.

Example 4 In the preparation of the catalyst (1) of Example 1, the contents of tungsten, cobalt, iron and bismuth were changed, sodium and potassium were used as Group C elements, and 6 g of titanium dioxide and 43 g of cerium dioxide were added. Catalysts (10), (11) and (12) were prepared in the same manner as catalyst (1), except that they were molded into a sphere and calcined at 465 ° C. for 8 hours under flowing air.

The compositions of catalysts (10), (11) and (12) were as follows in atomic ratio excluding oxygen.

Catalyst (10) Mo ₁₂ W _0.5 Bi _1.5 Fe ₂ Co ₆ Na _0.1 K _0.05 Ce _0.5 Si _1.35 Ti _0.15 B
a _0.1 Catalyst (11) Mo ₁₂ W _0.5 Bi _1.5 Fe ₂ Co ₆ Na _0.1 K _0.05 Ce _0.5 Si _1.35 Ti _0.15 B
a _0.3 Catalyst (12) Mo ₁₂ W _0.5 Bi _1.5 Fe ₂ Co ₆ Na _0.1 K _0.05 Ce _0.5 Si _1.35 Ti _0.15 B
from the raw material gas inlet side to the reaction tube of a _0.5 inner diameter 30mm toward the outlet side catalyst (10) 400 ml, the catalyst (11) 400 ml and the catalyst (1
2) The reaction was carried out by filling 1000 ml and introducing a mixed gas having the same composition as in Example 1 at a space velocity of 2000 hr ^-1 (STP).
At a reaction temperature of 325 ° C., the propylene conversion was 98.5 mol%, and the total single stream yield of acrylic acid and acrolein was 92.1 mol%. Table 1 shows the results.

Comparative Example 10 A reaction was carried out in the same manner as in Example 4, except that 1800 ml of the catalyst (10) was charged instead of the catalysts (10) to (12). Table 1 shows the results.

Comparative Example 11 The reaction was carried out in the same manner as in Example 4, except that 1800 ml of the catalyst (11) was charged instead of the catalysts (10) to (12). Table 1 shows the results.

Comparative Example 12 A reaction was carried out in the same manner as in Example 4, except that 1800 ml of the catalyst (12) was charged instead of the catalysts (10) to (12). Although the reaction temperature was lowered to 300 ° C., the heat generated in the catalyst layer was large, and the reaction was unstable, so that the reaction could not be continued.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C07C 47/22 C07C 47/22 G 57/05 57/05 // C07B 61/00 300 C07B 61/00 300 (72) Inventor Masahiro Wada 992, Nishioki, Okihama-shi, Aboshi-ku, Himeji-shi, Hyogo Japan Examiner, Catalyst Research Laboratory, Nippon Shokubai Chemical Industry Co., Ltd. Hiroko Fujiwara (56) References JP-A-3-200733 (JP, A) Int.Cl. ⁶ , DB name) C07C 27/12-27/14 C07C 47/22 C07C 57/05

Claims (3)

(57) [Claims] 1. A method for producing acrolein and acrylic acid by subjecting propylene to gas phase catalytic oxidation with molecular oxygen or a molecular oxygen-containing gas using a fixed-bed multitubular reactor, comprising the steps of: General formula (I) Mo _a W _b Bi _c Fe _d A _e B _f C _g D _h E _i O _x (wherein, Mo is molybdenum, W is tungsten, Bi is bismuth, Fe is iron, A is nickel and cobalt. B is at least one element selected from alkali metals and thallium, C is at least one element selected from alkaline earth metals, D is phosphorus, tellurium, antimony, tin, cerium And at least one element selected from lead, niobium, manganese, arsenic and zinc, and E is at least one element selected from silicon, aluminum, titanium and zirconium O represents oxygen, also a, b, c, d, e, f,
g, h, i and x are Mo, W, Bi, Fe,
Represents the number of atoms of A, B, C, D, E and O, and when a = 12, b = 0 to 10, c = 0.1 to 10, d = 0.1 to 20, e
= 2 to 20, f = 0 to 10, g = 0.001 to 10, h = 0 to 4,
(i = 0 to 30, x = a value determined by the oxidation state of each element). (b) The catalyst layer in each reaction tube is divided into two or more layers in the tube axis direction. (C) a plurality of catalysts having different activities prepared by changing the type and / or amount of the group C element in the general formula (I) in the catalyst of the above (a). Characterized in that the starting material gas is filled from the inlet to the outlet so that the activity becomes higher. 2. The process for producing acrolein and acrylic acid according to claim 1, wherein the number of reaction zones is 2 or 3. 3. The catalyst has an outer diameter of 3 to 10 mm and a length of 0.
5 to 2 times, the inner diameter of the through hole in the length direction is 0.1 to 0.7 of the outer diameter
The method for producing acrolein and acrylic acid according to claim (1) or (2), which is a double ring catalyst.