JPH06134317A - Catalyst for producing unsaturated carboxylic acid and use thereof - Google Patents

Abstract

(57) [Summary] [Object] To provide a catalyst in a novel form for advantageously producing an unsaturated carboxylic acid from an unsaturated aldehyde. [Claim] A cylindrical catalyst having a circular cross section having a central hole inside, wherein the central cross section has at least three rounded convex curves in contact with its circumscribing circle, and the same number. Contact particles having a shape consisting of rounded concave curves. The catalyst component contains at least molybdenum and vanadium. [Effect] It is possible to improve the yield when an unsaturated carboxylic acid is obtained by a gas phase catalytic oxidation reaction of an unsaturated aldehyde.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the shape of a molded catalyst used for producing an unsaturated carboxylic acid by vapor phase catalytic oxidation of an unsaturated aldehyde.

[0002]

BACKGROUND OF THE INVENTION Conventionally, a method and a catalyst for producing an unsaturated carboxylic acid by vapor-phase catalytic oxidation of an unsaturated aldehyde,
Many proposals have been made. Various catalyst shapes such as a ring shape and a wheel shape have been proposed therein. For example, JP-A-58-166939 and 59-
There are reports such as 115750 and JP-A No. 2-169036. However, under the present circumstances, further improvement is desired when used as an industrial catalyst.

[0003]

The ring-shaped catalyst has insufficient mechanical strength and is disadvantageous in terms of life. The present invention is
It is an object of the present invention to provide a molded catalyst product having a novel shape, which can advantageously produce an unsaturated carboxylic acid from an unsaturated aldehyde.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to improve the shape of conventional catalyst moldings, and as a result, they are superior in mechanical strength to ordinary ring-shaped catalysts and, in addition, unsaturated carboxylic acids The shape of a novel catalyst molded body that can be obtained in high yield was found. The present invention provides a cylindrical catalyst particle having a circular cross-section with a central hole having a shape consisting of at least three rounded convex curves contacting the circumscribed circle of the central hole and the same number of rounded concave curves. A catalyst for producing an unsaturated carboxylic acid by vapor-phase catalytic oxidation of an unsaturated aldehyde containing at least molybdenum and vanadium as a catalyst component, and a method for producing an unsaturated carboxylic acid using this catalyst.

Generally, a ring-shaped catalyst has a larger outer surface area than a cylindrical catalyst. Therefore, the outer surface area of the molded catalyst in the reactor is increased, and the catalytic activity is improved. Furthermore, since the catalyst bed has a higher porosity, the pressure loss is lower. However, the actual volume of the catalyst is reduced, which is disadvantageous in terms of the life of the catalyst and the mechanical strength is greatly reduced, so that the handling becomes complicated when the catalyst is filled in the reaction tube. The cylindrical catalyst having the uneven central hole according to the present invention can achieve the same outer surface area with a larger actual volume than the ring-shaped catalyst by increasing the degree of the unevenness. Therefore, the filling amount of the molded catalyst in the reactor is increased, so that the catalytic activity is improved, and as a result, the unsaturated carboxylic acid is obtained in a high yield. Also, the mechanical strength of the catalyst is improved.

The cross-sectional shape of the catalyst particles according to the invention can be defined by a number of parameters. For example, L is the radius of the catalyst particle, R is the radius of the circumscribed circle where the rounded convex curve touches in the central hole, r is the distance between the circumscribed circle and the end of the concave curve, and N is the roundness of the convex curve. It can be specified as a number. L is preferably in the range of 1.5 to 10 mm. When L is less than 1.5 mm when the reaction tube is filled with the catalyst, the pressure loss becomes large and the catalytic reaction cannot be smoothly performed.
Also, when L is larger than 10 mm, the filling amount becomes small,
It is disadvantageous in terms of catalyst life. N is preferably in the range of 3 to 8. Further, R / L is preferably 0.1 to 0.9, (LR) is 0.5 mm or more, and r / R is preferably 0.2 to 0.8. The present catalyst can be molded by a usual extrusion molding machine or tablet molding machine. When molding the present catalyst, conventionally known additives, for example, organic compounds such as polyvinyl alcohol and carboxymethyl cellulose, inorganic compounds such as graphite and diatomaceous earth, and inorganic fibers may be further added. The shaped catalyst thus obtained is then heat treated. In the present invention, the processing conditions are not particularly limited, and known processing conditions can be applied. Usually, the heat treatment is performed at 300 to 500 ° C. The method for preparing the catalyst of the present invention does not need to be limited to a special method, and as long as there is no significant uneven distribution of components, it is possible to use the well-known evaporation dryness method, precipitation method, oxide mixing method, etc. Various methods can be used. The raw materials used to prepare the catalyst are oxides of each element,
A combination of nitrates, carbonates, ammonium salts, halides and the like can be used. For example, ammonium paramolybdate, molybdenum trioxide, molybdenum chloride, etc. can be used as the molybdenum raw material, and ammonium metavanadate, vanadium pentoxide, vanadium chloride, etc. can be used as the vanadium raw material. The catalyst of the present invention can also be used after diluting it with an inert carrier such as silica, alumina, silica-alumina, magnesia, titania or silicon carbide. When the unsaturated carboxylic acid is produced using the catalyst of the present invention, the concentration of the unsaturated aldehyde in the raw material gas can be varied over a wide range, but 1-20% by volume is suitable, and particularly 3% 10% is preferable. The starting unsaturated aldehyde may contain a small amount of impurities such as water and lower saturated aldehyde, and these impurities do not substantially affect the reaction. It is economical to use air as the oxygen source, but if necessary, air enriched with pure oxygen can also be used.
The oxygen concentration in the raw material gas is defined by the molar ratio to the unsaturated aldehyde, and this value is 0.3 to 4, particularly 0.4 to 2.
5 is preferable. The raw material gas may be diluted by adding an inert gas such as nitrogen, steam or carbon dioxide gas. The reaction pressure is preferably atmospheric pressure to several atmospheres. The reaction temperature can be selected in the range of 200 to 450 ° C, but 210 to 400 ° C is particularly preferable. The reaction can be carried out in a fixed bed.

Examples of the production of unsaturated carboxylic acid by vapor phase catalytic oxidation of unsaturated aldehyde in the present invention include production of acrylic acid by oxidation of acrolein and production of methacrylic acid by oxidation of methacrolein. The catalyst for acrylic acid production by oxidation of acrolein, the general formula _{Mo a V b A c X d} Y e O f ( wherein wherein Mo, V and O each represent molybdenum, vanadium and oxygen, A is iron, Cobalt, chrome,
At least one element selected from the group consisting of aluminum and strontium is shown, and X is selected from the group consisting of germanium, boron, arsenic, selenium, silver, silicon, sodium, tellurium, lithium, antimony, phosphorus, potassium and barium. And at least one element, Y is magnesium, titanium, manganese, copper, zinc,
At least one element selected from the group consisting of zirconium, niobium, tungsten, tantalum, calcium, tin and bismuth is shown. a, b, c, d, e and f represent the atomic ratio of each element, and when a = 12, b = 0.01
~ 6, c = 0.1-5, d = 0-10, e = 0-5, and f is the number of oxygen atoms required to satisfy the valence of each component. ) The thing which has a composition represented by these is mentioned.

The catalyst for the production of methacrylic acid by oxidation of methacrolein has the general formula P _a Mo _b V _c Cu _d X _e Y _f Z _g O _h (wherein P, Mo, V, Cu and O Represents phosphorus, molybdenum, vanadium, copper and oxygen, and X represents at least one element selected from the group consisting of arsenic, antimony, bismuth, germanium, zirconium, tellurium, silver, selenium, silicon, tungsten and boron. , Y represents at least one element selected from the group consisting of iron, zinc, chromium, magnesium, tantalum, manganese, cobalt, barium, gallium, cerium and lanthanum, and Z represents potassium, rubidium, cesium and thallium. At least one element selected from the group consisting of a, b, c, d, e, f, g and h is Atomic ratio, a = 0.5 to 3, c when b = 12
= 0.01 to 3, d = 0 to 2, e = 0 to 3, f = 0
3, g = 0.01 to 3, and h is the number of oxygen atoms required to satisfy the valence of each component. ) The thing which has a composition represented by these is mentioned.

[0009]

EXAMPLES Hereinafter, a method for preparing the catalyst of the present invention and a reaction example using the same will be specifically described. In Examples and Comparative Examples,
The reaction rate of unsaturated aldehyde and the selectivity of unsaturated carboxylic acid produced are defined as follows.

[Equation 1] Parts in the following Examples and Comparative Examples are parts by weight, and analysis was by gas chromatography.

Example 1 100 parts of ammonium paramolybdate, 4.4 parts of ammonium metavanadate and 4.8 parts of potassium nitrate were dissolved in 400 parts of pure water. While stirring this, a solution prepared by dissolving 6.5 parts of 85% phosphoric acid in 10 parts of pure water was added, and further a solution prepared by dissolving 1.1 parts of copper nitrate in 10 parts of pure water was added. Next, 7.0 parts of 60% nitric acid and 40 parts of pure water were added to 6.9 parts of bismuth nitrate, the obtained uniform solution of bismuth nitrate was added to the mixed solution, and the temperature was raised to 95 ° C. 6 for this
A solution prepared by dissolving 2.2 parts of 0% arsenic acid in 10 parts of pure water was added,
Subsequently, 2.1 parts of antimony trioxide was added. The mixture was evaporated to dryness with heating and stirring, and then the obtained solid was dried at 130 ° C. for 16 hours.

The degree of polymerization is 500 with respect to 100 parts of this dry powder.
3 parts of polyvinyl alcohol and 15 parts of water are mixed, and the cross-sectional shape of the catalyst particles is L = 2.5 mm by an extrusion molding machine.
Then, it was molded into a cylindrical shape having a central hole of R = 1 mm, r = 0.5 mm and N = 3 (FIG. 1) and an average length of 5 mm. The shaped catalyst was dried at 130 ° C. for 6 hours, and then heat-treated at 380 ° C. for 5 hours under air flow to be used as a catalyst.
The composition of elements other than oxygen in the obtained catalyst (the same applies hereinafter) is
P _1.2 Mo ₁₂ V _0.8 Cu _0.1 Sb _0.3 Bi _0.3 As _0.2
It was K ₁ . The catalyst was filled in a reaction tube, and a mixed gas of methacrolein 5%, oxygen 10%, water vapor 30%, and nitrogen 55% (volume%) was passed at a reaction temperature of 290 ° C. and a contact time of 3.6 seconds. When the product was collected and analyzed by gas chromatography, the methacrolein conversion was 91.4% and the methacrylic acid selectivity was 88.2%.

Example 2 In Example 1, the catalyst particles were shaped such that the cross-sectional shape of the catalyst particles was L = 2.5 mm, R = 1 mm, r = 0.5 mm, N =
Molding and reaction were performed in the same manner as in Example 1 except that the sample had a central hole of 4 (FIG. 2) and a cylindrical shape having an average length of 5 mm. As a result, the methacrolein conversion was 91.4% and the methacrylic acid selectivity was 88.3%.

Comparative Example 1 In Example 1, the shape of the catalyst particles was a ring shape having an average length of 5 mm with a cross-sectional shape of the catalyst particles of L = 2.5 mm and a circular hole with a radius of 1 mm (FIG. 3). Example 1 except
Molding and reaction were carried out in the same manner as in. As a result, the methacrolein conversion rate was 90.0% and the methacrylic acid selectivity was 8
It was 8.1%.

Example 3 100 parts of molybdenum trioxide, 4.2 parts of vanadium pentoxide
Parts, 10.0 parts of 85% phosphoric acid are mixed with 800 parts of pure water. This was heated and stirred under reflux for 3 hours, and then copper oxide of 0.
5 parts, 0.9 part of ferrous oxide and 0.4 part of boric acid were added, and the mixture was again heated and stirred under reflux for 2 hours. This slurry at 50 ° C
It was cooled to 1.2 parts, and 1.2 parts of germanium dioxide dissolved in 43.4 parts of 20% cesium hydroxide aqueous solution was added.
Stir for minutes. Next, a solution prepared by dissolving 10 parts of ammonium nitrate in 30 parts of pure water was added, and the mixed solution was evaporated to dryness while heating and stirring at 100 ° C. The solid obtained is 120 ° C.
After being dried for 16 hours in the same manner as in Example 1,
Shaped in the same shape as. The shaped catalyst was dried at 130 ° C. for 6 hours, and then heat-treated at 380 ° C. for 5 hours under air flow to be used as a catalyst. The composition of the obtained catalyst is P
_1.5 Mo ₁₂ V _0.8 Ge _0.2 B _0.1 Cu _0.1 Fe _0.2 Cs
_{Was 1} . Using this catalyst, the reaction was carried out under the same conditions as in Example 1 except that the reaction temperature was 275 ° C.
The methacrolein conversion was 93.5% and the methacrylic acid selectivity was 87.5%.

Example 4 Molding and reaction were carried out in the same manner as in Example 3 except that the shape of the catalyst particles in Example 3 was the same as in Example 2. As a result, the methacrolein conversion was 93.5% and the methacrylic acid selectivity was 87.6%.

Comparative Example 2 Molding and reaction were carried out in the same manner as in Example 3 except that the shape of the catalyst particles in Example 3 was the same as that in Comparative Example 1. As a result, the methacrolein conversion was 92.2% and the methacrylic acid selectivity was 87.4%.

Example 5 100 parts of ammonium paramolybdate, 5.0 parts of ammonium paratungstate and 16.6 parts of ammonium metavanadate were dissolved in 1000 parts of pure water. A solution prepared by dissolving 9.5 parts of ferric nitrate in 200 parts of pure water was added thereto, and further a solution prepared by dissolving 5.5 parts of cobalt nitrate in 200 parts of pure water and 4.1 parts of manganese nitrate in 200 parts of pure water. The solution dissolved in 1 part was sequentially added. Next, the general formula Na ₂ O.2.
2SiO ₂ · 2.2H ₂ O-3.9 parts of water glass represented a solution prepared by dissolving 30 parts of pure water was further added 20% silica sol 49.6 parts. The mixture was evaporated to dryness with heating and stirring, and the solid obtained was dried at 130 ° C for 1 hour.
It was dried for 6 hours.

20 parts of water and 10 parts of an inorganic fiber having an average length of 200 μm were mixed with 100 parts of the dry powder,
The cross-sectional shape of the catalyst particles was L = 2.5m by the extruder.
At m, it was shaped into a cylinder with an average length of 5 mm with a central hole of R = 1 mm, r = 0.5 mm, N = 5 (FIG. 4). The shaped catalyst was dried at 130 ° C. for 6 hours, and then heat-treated at 380 ° C. for 5 hours under air flow to be used as a catalyst. The composition of the obtained catalyst was Mo ₁₂ V ₃ Fe _0.5 Si.
_{It was 4.3} Na _0.7 Co _0.4 Mn _0.3 W _0.4 . The catalyst was filled in a reaction tube, and a mixed gas of acrolein 5%, oxygen 10%, water vapor 30%, and nitrogen 55% (volume%) was passed at a reaction temperature of 270 ° C. and a contact time of 3.6 seconds. The product was collected and analyzed by gas chromatography to find that the acrolein conversion was 99.7% and the acrylic acid selectivity was 95.3%.
Met.

Comparative Example 3 Molding and reaction were carried out in the same manner as in Example 5 except that the shape of the catalyst particles in Example 5 was the same as that in Comparative Example 1. As a result, the acrolein conversion was 98.8% and the acrylic acid selectivity was 95.1%.

[0020]

The catalyst prepared by the method of the present invention has the effect of improving the yield of unsaturated carboxylic acid produced in the gas phase catalytic oxidation reaction of unsaturated aldehydes.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a catalyst of the present invention.

FIG. 2 is a cross-sectional view of another catalyst of the present invention.

FIG. 3 is a cross-sectional view of a conventional catalyst

FIG. 4 is a cross-sectional view of another catalyst of the present invention.

Claims (2)

[Claims] 1. A cylindrical catalyst grain having a circular cross section with a central hole having a shape consisting of at least three rounded convex curves contacting the circumscribed circle of the central hole and the same number of rounded concave curves. A catalyst for producing an unsaturated carboxylic acid by vapor-phase catalytic oxidation of an unsaturated aldehyde containing at least molybdenum and vanadium as a catalyst component. 2. When at least three molybdenum and vanadium are contained as catalyst components in the vapor phase catalytic oxidation of acrolein or methacrolein to produce acrylic acid or methacrylic acid, there are at least three rounded portions in contact with the circumscribed circle of the central hole. A process characterized in that a cylindrical catalyst grain with a circular cross section having a central hole in the shape of a convex curve and the same number of rounded concave curves is used in a fixed bed.