阅读说明：本技术 催化剂 (Catalyst and process for preparing same ) 是由 伊藤贡悦 伊藤宏透 于 2019-03-22 设计创作，主要内容包括：本发明提供一种催化剂,其是用于制造不饱和醛及不饱和羧酸的催化剂,催化剂所具有的细孔直径为1μm以上且100μm以下的细孔的累积细孔容积(A)为0.12ml/g以上且0.19ml/g以下,而且该累积细孔容积(A)相对于累积细孔容积(B)之比(A/B)为0.30以上且0.87以下,所述累积细孔容积(B)是在特定条件下将该催化剂粉碎而得到的粉碎物中未通过泰勒标准筛6目的粉碎物所具有的细孔直径为1μm以上且100μm以下的细孔的累积细孔容积。(The present invention provides a catalyst for producing an unsaturated aldehyde and an unsaturated carboxylic acid, wherein the catalyst has pores having a pore diameter of 1 to 100 [ mu ] m, and a cumulative pore volume (A) of pores having a pore diameter of 0.12 to 0.19ml/g inclusive, and wherein the ratio (A/B) of the cumulative pore volume (A) to the cumulative pore volume (B) of pores having a pore diameter of 1 to 100 [ mu ] m inclusive, which are included in a crushed product obtained by crushing the catalyst under specific conditions and which do not pass through a Taylor standard sieve 6 mesh, is 0.30 to 0.87 inclusive.)

1. A catalyst for producing an unsaturated aldehyde and an unsaturated carboxylic acid,

the catalyst has a cumulative pore volume (A) of pores having a pore diameter of 1 to 100 μm of 0.12 to 0.19ml/g

A ratio (A/B) of the cumulative pore volume (A) of pores having a pore diameter of 1 to 100 [ mu ] m, which are contained in a crushed product obtained by crushing the catalyst under the crushing condition A and which do not pass through the mesh of the Taylor standard sieve 6, to the cumulative pore volume (B) of pores having a pore diameter of 1 to 100 [ mu ] m, is 0.30 to 0.87,

(crushing Condition A)

100G of a catalyst was charged into a tumbling granulator having a cylinder fixed to a vertical shape and a disk horizontally provided at the lower end thereof, and rotating the disk about the center of the cylinder to cause the particles to perform rotation and revolution, the operation of the disk was started at a relative centrifugal acceleration of 12G, the rotation of the disk was continued for 2 minutes at a relative centrifugal acceleration of 130G within 1 minute,

the relative centrifugal acceleration is a value represented by the ratio of the magnitude of the centrifugal force applied per unit weight of the catalyst to the gravitational acceleration, and is represented by the following formula (X),

F＝1118×r×N²×10^-8formula (X)

F: with respect to the centrifugal acceleration (G),

r: a distance (cm) from the rotation center to the lower end of the cylinder,

n: rotational speed (rpm).

2. The catalyst according to claim 1, which comprises molybdenum (Mo), bismuth (Bi), cobalt (Co), nickel (Ni) and iron (Fe), and the atomic ratio of molybdenum (Mo), bismuth (Bi), cobalt (Co), nickel (Ni) and iron (Fe) in the catalyst satisfies the following formula (1),

Mo_aBi_bCo_cNi_dFe_e(1)

wherein a to e represent the atomic ratio of each element, and when a is 12, b is 0.5 to 7, c is 0.1 to 10, d is 0.1 to 10, and e is 0.05 to 5.

3. The catalyst of claim 1 or 2, comprising a support.

4. A catalyst according to any one of claims 1 to 3, which is spherical in shape.

5. A process for producing acrolein and acrylic acid, the process comprising: a process for the gas-phase catalytic oxidation of propylene and an oxygen-containing gas by using the catalyst according to any one of claims 1 to 4.

Technical Field

The present invention relates to a catalyst for producing an unsaturated aldehyde and an unsaturated carboxylic acid.

Background

A catalyst for producing an unsaturated aldehyde and an unsaturated carboxylic acid by subjecting an olefin having 3 or 4 carbon atoms, etc. to vapor phase catalytic oxidation with an oxygen-containing gas is usually a catalyst containing molybdenum as an essential component. Specifically, from various viewpoints, improvements of a catalyst used in the production of acrolein and acrylic acid using propylene or the like as a raw material and methacrolein and methacrylic acid using isobutylene or the like as a raw material, and a production method thereof have been more actively carried out.

The method for producing an unsaturated aldehyde or an unsaturated carboxylic acid comprises: an olefin is subjected to gas phase catalytic oxidation with an oxygen-containing gas in a fixed bed reactor packed with a catalyst.

The catalyst packed in the fixed bed reactor has a shape such as a cylinder, a ring, a flat plate, or a sphere, and usually, a catalyst obtained by molding a powder of a catalytically active component or a catalyst obtained by supporting a catalytically active component on an inactive carrier having the same shape as the above-mentioned shape can be used.

As a catalyst for propylene oxidation, patent document 1 proposes a catalyst containing molybdenum, iron, and bismuth, and having a specific surface area and a specific pore volume. Patent document 2 discloses a catalyst for producing an unsaturated aldehyde and an unsaturated carboxylic acid, in which the pore volume existing in a specific pore diameter is in a specific range.

Disclosure of Invention

Problems to be solved by the invention

However, the catalyst described in patent document 1 is insufficient in reaction efficiency even when used for the gas-phase catalytic oxidation of an olefin such as propylene with an oxygen-containing gas, and cannot obtain a corresponding unsaturated aldehyde such as acrolein and an unsaturated carboxylic acid such as acrylic acid in high yields. In addition, when the gas phase catalytic oxidation is performed at a high temperature in order to improve the activity of the catalyst, there is a problem that a side reaction occurs to further lower the yield. Further, the catalyst is insufficient in strength, and the catalyst is pulverized or cracked, so that the gas-phase catalytic oxidation reaction cannot be stably and efficiently performed for a long period of time.

In addition, the catalyst described in patent document 2 has room for improvement in terms of the yield of the unsaturated carboxylic acid and the strength of the catalyst.

The present invention has been made to solve the above problems. Namely, it is an object to provide the following catalysts: as a catalyst used in the production of a corresponding unsaturated aldehyde such as acrolein and an unsaturated carboxylic acid such as acrylic acid by vapor-phase catalytic oxidation of an olefin such as propylene with an oxygen-containing gas, even under conditions in which the amount of the olefin such as propylene supplied as a raw material is large, that is, the load applied to the catalyst is high, the conversion rate of the raw material is excellent, a desired unsaturated aldehyde and an unsaturated carboxylic acid can be selectively produced with high yield, the strength is high, and a stable vapor-phase catalytic oxidation reaction can be performed over a long period of time.

Means for solving the problems

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a catalyst having a cumulative pore volume (a) of pores having a pore volume of 1 to 100 μm of 0.12 to 0.19ml/g inclusive and a ratio (a/B) of the cumulative pore volume (a) to the cumulative pore volume (a) of pores having a pore volume of 1 to 100 μm inclusive is 0.30 to 0.87 inclusive has been completed by the present invention, which has an excellent conversion rate of olefin, a good selectivity for unsaturated aldehyde such as acrolein and a good selectivity for unsaturated carboxylic acid such as acrylic acid, and particularly a high ratio of the selectivity for unsaturated carboxylic acid such as acrylic acid, and an improved yield of unsaturated aldehyde such as acrolein and unsaturated carboxylic acid such as acrylic acid, when olefin and oxygen-containing gas are catalytically oxidized in a gas phase using the catalyst, even under the condition that the amount of olefin supplied is large and the load on the catalyst is high, and has been prepared as the catalyst The cumulative pore volume (B) is the cumulative pore volume of pores having a pore diameter of 1 to 100 μm in a crushed product obtained by crushing the catalyst under specific conditions, the diameter of pores not passing through a Tyler (Tyler) sieve 6 mesh.

Namely, the present invention is as follows.

[1] A catalyst for producing an unsaturated aldehyde and an unsaturated carboxylic acid,

the catalyst has a cumulative pore volume (A) of pores having a pore diameter of 1 to 100 μm of 0.12 to 0.19ml/g

A ratio (A/B) of the cumulative pore volume (A) of pores having a pore diameter of 1 to 100 [ mu ] m, which are contained in a crushed product obtained by crushing the catalyst under the crushing condition A and which do not pass through the mesh of the Taylor standard sieve 6, to the cumulative pore volume (B) of pores having a pore diameter of 1 to 100 [ mu ] m, is 0.30 to 0.87,

(crushing Condition A)

100G of a catalyst was charged into a tumbling granulator having a cylinder fixed to a vertical shape and a disk horizontally provided at the lower end thereof, and rotating the disk about the center of the cylinder to cause the particles to perform rotation and revolution, the operation of the disk was started at a relative centrifugal acceleration of 12G, the rotation of the disk was continued for 2 minutes at a relative centrifugal acceleration of 130G within 1 minute,

the relative centrifugal acceleration is a value representing the magnitude of the centrifugal force applied per unit weight of the catalyst by the ratio to the acceleration of gravity, and is represented by the following formula (X),

F＝1118×r×N²×10^-8formula (X)

F: with respect to the centrifugal acceleration (G),

r: a distance (cm) from the rotation center to the lower end of the cylinder,

n: rotational speed (rpm).

[2] The catalyst according to [1], which comprises molybdenum (Mo), bismuth (Bi), cobalt (Co), nickel (Ni) and iron (Fe), wherein the atomic ratio of molybdenum (Mo), bismuth (Bi), cobalt (Co), nickel (Ni) and iron (Fe) in the catalyst satisfies the following formula (1).

Mo_aBi_bCo_cNi_dFe_e(1)

(wherein a to e represent the atomic ratio of each element, and when a is 12, b is in the range of 0.5 to 7, c is in the range of 0.1 to 10, d is in the range of 0.1 to 10, and e is in the range of 0.05 to 5.)

[3] The catalyst according to [1] or [2], which comprises a support.

[4] The catalyst according to any one of [1] to [3], which is spherical in shape.

[5] A process for producing acrolein and acrylic acid, the process comprising: a step of subjecting propylene and an oxygen-containing gas to vapor-phase catalytic oxidation using the catalyst according to any one of [1] to [4 ].

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, there can be provided a catalyst which has high catalytic performance, is excellent in the conversion rate of an olefin even under a condition of a high load applied to the catalyst, and can suppress an excessive oxidation reaction to produce an unsaturated aldehyde such as acrolein and an unsaturated carboxylic acid such as acrylic acid at a high selectivity. In addition, the catalyst of the present invention has high strength and less pulverization. As a result, the reactor can be efficiently filled with the catalyst, and the catalyst can be used to produce an unsaturated aldehyde such as acrolein and an unsaturated carboxylic acid such as acrylic acid, particularly an unsaturated carboxylic acid such as acrylic acid, with high selectivity over a long period of time from the start of the gas-phase catalytic oxidation.

Detailed Description

The best mode for carrying out the present invention will be described in detail below, but the description of the constituent elements described below is a representative example of the embodiment of the present invention, and the present invention is not limited to these contents.

[ catalyst ]

A catalyst for use in the production of an unsaturated aldehyde and an unsaturated carboxylic acid, wherein the catalyst has pores having a pore diameter of 1 to 100 [ mu ] m, and wherein the cumulative pore volume (A) of pores having a pore diameter of 1 to 100 [ mu ] m is 0.12 to 0.19ml/g, and wherein the ratio (A/B) of the cumulative pore volume (A) to the cumulative pore volume (B) of pores having a pore diameter of 1 to 100 [ mu ] m, which are contained in a crushed product obtained by crushing the catalyst under the crushing condition A and which do not pass through a Taylor standard sieve 6, is 0.30 to 0.87. The ratio (a/B) is preferably 0.50 or more and 0.87 or less, more preferably 0.65 or more and 0.87 or less, and further preferably 0.60 or more and 0.87 or less. When the ratio (a/B) is within the above range, a catalyst which is excellent in conversion of the raw material in the gas-phase catalytic oxidation of an olefin (hereinafter, may be simply referred to as "conversion") and can produce an unsaturated aldehyde and an unsaturated carboxylic acid with high selectivity can be obtained, and the catalyst tends to have high strength and suppressed pulverization.

The above ratio (a/B) will be described in more detail below. The cumulative pore volume (a) reflects the volume of pores near the catalyst surface, and the cumulative pore volume (B) reflects the volume of pores inside the catalyst. That is, the smaller the cumulative pore volume (a), the higher the density of the catalyst surface, the higher the catalyst strength, while the raw material gas hardly reaches the inside of the catalyst, and the catalytically active component present in the inside of the catalyst hardly contributes to the catalytic reaction, resulting in a decrease in the conversion rate. The larger the cumulative pore volume (a), the lower the density of the catalyst surface, and the lower the catalyst strength, but the more easily the raw material gas reaches the inside of the catalyst, and not only the catalytically active component present in the vicinity of the catalyst surface but also the catalytically active component present in the inside of the catalyst is effectively utilized, and therefore the conversion rate is improved.

Therefore, when the ratio (A/B) is within the above range, the balance between the conversion of the raw material and the strength of the catalyst is optimized.

The catalyst pulverization condition a was a condition in which 100G of the catalyst was charged into a tumbling granulator having a cylindrical body fixed to a vertical shape and a disk horizontally provided at the lower end thereof, and the disk was rotated about the center of the cylindrical body to cause the particles to perform a rotation motion and a revolution motion, the operation of the disk was started at a relative centrifugal acceleration of 12G, the rotation of the disk was continued for 2 minutes at a relative centrifugal acceleration of 130G within 1 minute, and the catalyst was pulverized.

The relative centrifugal acceleration is a numerical value represented by a ratio of the magnitude of the centrifugal force applied to each unit weight of the catalyst to the gravitational acceleration, and is represented by the following formula (X).

F＝1118×r×N²×10^-8Formula (X)

F: relative centrifugal acceleration (G)

r: distance (cm) from the center of rotation to the lower end of the cylinder

N: rotational speed (rpm)

The pulverization of the catalyst under the pulverization conditions a is specifically carried out by: for example, 100g of the catalyst was charged into a Malmerizer QJ-230T-2 type (cylinder diameter 23cm) manufactured by DALTON, and the operation was started at a rotation speed of 300rpm, and the rotation speed was set to 1000rpm within 1 minute, and the operation was continued at 1000rpm for 2 minutes.

The cumulative pore volume can be measured by mercury intrusion method. The mercury pressing method is as follows: after the sample was subjected to a reduced pressure treatment under reduced pressure (50. mu. mHg or less) for 10 minutes, the total pore volume (cumulative pore volume) was determined from the measured mercury intrusion curve using an Autopore IV9520 manufactured by Micromeritics Japan.

Further, the conversion of the raw material (olefin), the selectivity for the unsaturated aldehyde, and the selectivity for the unsaturated carboxylic acid were calculated by the following formulas.

Olefin conversion (% by mole) × 100 (moles of olefin reacted/moles of olefin supplied) × 100

The selectivity (mol%) of unsaturated aldehyde ═ mole (moles of unsaturated aldehyde formed/moles of olefin reacted) × 100

The selectivity (mol%) of the unsaturated carboxylic acid (mol% of the unsaturated carboxylic acid produced/mol of the olefin reacted) × 100

The cumulative pore volume (A) of the pores having a pore diameter of 1 to 100 μm is 0.12 to 0.19ml/g, preferably 0.12 to 0.18ml/g, more preferably 0.15 to 0.18 ml/g. By setting the cumulative pore volume (a) to the upper limit or less, breakage and pulverization of the catalyst can be suppressed. Further, by setting the cumulative pore volume (a) to the lower limit or more, a high conversion rate of the raw material, a high selectivity for the unsaturated aldehyde, a high selectivity for the unsaturated carboxylic acid, and a high selectivity for the unsaturated carboxylic acid can be easily achieved.

The ratio of the selectivity of the unsaturated carboxylic acid is a ratio of the selectivity of the unsaturated carboxylic acid to the total of the selectivity of the unsaturated aldehyde and the selectivity of the unsaturated carboxylic acid.

The catalyst contains molybdenum (Mo), bismuth (Bi), cobalt (Co), nickel (Ni), and iron (Fe), and the atomic ratio of molybdenum (Mo), bismuth (Bi), cobalt (Co), nickel (Ni), and iron (Fe) in the catalyst preferably satisfies the following formula (1).

Mo_aBi_bCo_cNi_dFe_e(1)

(wherein a to e represent the atomic ratio of each element, and when a is 12, b is in the range of 0.5 to 7, c is in the range of 0.1 to 10, d is in the range of 0.1 to 10, and e is in the range of 0.05 to 5.)

By satisfying the above formula (1), it is possible to produce an unsaturated aldehyde such as acrolein and an unsaturated carboxylic acid such as acrylic acid with high selectivity, while having excellent conversion of propylene.

The catalyst preferably further comprises a support. More preferably, the support is inactive in the gas phase catalytic oxidation of the olefin and the oxygen-containing gas. Examples of the carrier include: silica, silicon carbide, alumina, mullite, corundum, etc., and alumina is more preferable. By including the carrier, the catalyst can exhibit a catalytic function not only on the surface but also inside of the catalyst, and improvement of the selectivity for the unsaturated aldehyde and the selectivity for the unsaturated carboxylic acid can be expected.

The amount of the carrier is an amount in which the ratio of the amount of the powder of the catalyst active component to the total amount of the powder of the catalyst active component and the amount of the carrier (the amount of the powder of the catalyst active component/(the amount of the powder of the catalyst active component + the amount of the carrier)) is usually 10 to 90% by weight, preferably 30 to 80% by weight. By setting the ratio within the above range, the cumulative pore volume (a) of the catalyst to be produced can be easily set within the range of the present invention.

The shape of the catalyst may be circular, cylindrical, flat, spherical, etc., and is preferably spherical. The spherical shape is not only a geometrically regular spherical shape but also an ellipsoidal shape, and is more preferably a spherical shape close to a regular spherical shape. In the present embodiment, among 3 mutually orthogonal diameters of the catalyst particles, the catalyst having a ratio of the longest diameter (major axis diameter) to the shortest diameter (minor axis diameter) of 2 or less, preferably 1.3 or less, is spherical as the shape. By making the catalyst spherical, there is a possibility that an increase in pressure loss of the catalyst-packed layer in the fixed-bed reactor can be suppressed.

It should be noted that the ratio of the major axis diameter to the minor axis diameter of the catalyst can be calculated as follows: the major axis diameter and the minor axis diameter of each of 100 catalyst particles were measured by a high-precision two-dimensional size measuring device VM-8040 manufactured by KEYENCE corporation, and then the average of the major axis diameter and the average of the minor axis diameter were obtained to calculate the ratio thereof.

The pulverization rate of the catalyst is preferably 3.0% or less, and more preferably 1.0% or less. When the pulverization rate of the catalyst is within the above range, the catalyst is excellent in strength, and the catalyst can be packed in a reaction tube of a fixed bed reactor without pulverization or cracking.

It should be noted that the pulverization rate of the catalyst can be calculated as follows: for example, a funnel (150 mm in the diameter of the upper part of the cone and 25mm in the diameter of the lower part of the cone) was inserted into the upper part of a cylinder (diameter: 66mm) having a height of 1m in the acrylic acid production, about 20g of the catalyst (sample for measuring pulverization rate) was thrown into the upper part of the cone of the funnel, the catalyst was dropped into a tray provided in the lower part of the cylinder through the cylinder, the dropped sample for measuring pulverization rate was collected from the tray, and the weight (pulverization weight) of fine particles sieved through a sieve having a sieve opening of 2.36mm was measured and calculated according to the following formula.

Powder ratio (%) - (powder weight/powder ratio measurement sample weight) × 100

Next, a preferred method for producing the catalyst will be described.

The method for producing the catalyst preferably includes the following 2 steps.

A step (a): a step of integrating and heating respective source compounds of elements containing molybdenum, bismuth, cobalt, nickel and iron (hereinafter, sometimes referred to as "catalytically active elements") in an aqueous system to obtain powders of catalytically active components

A step (b): a step of molding the powder of the catalytically active component obtained in the step (a) to prepare a molded body

The integration of the respective source compounds of the catalytically active elements containing molybdenum, bismuth, cobalt, nickel and iron in the aqueous system in the step (a) means that: the aqueous solution or aqueous dispersion of each source compound of the above-mentioned catalytically active element is mixed at once or stepwise, followed by aging treatment. Specifically, there are methods (a1) to (a5) described below, which are all included in the concept of integration of the source compounds of the catalytic active element in an aqueous system.

(a1) A method of mixing the above-mentioned source compounds at once.

(a2) A method of mixing the above-mentioned source compounds at once and then aging the mixture.

(a3) A method of mixing the above-mentioned source compounds in a stepwise manner.

(a4) The method of mixing the above-mentioned source compounds stepwise and carrying out the aging treatment is repeated.

(a5) A method comprising a combination of the above (a1) to (a 4).

Here, the aging means: "an operation of treating an industrial raw material or a semi-finished product under a specific condition such as a predetermined time and a predetermined temperature to obtain or improve a desired physical property or chemical property or to progress a predetermined reaction" (chemical dictionary/co-publication). In the present invention, the above-mentioned fixed time is in the range of 10 minutes to 24 minutes, and the above-mentioned fixed temperature is in the range from room temperature to the boiling point of the aqueous solution or aqueous dispersion.

The heating in the step (a) is a heat treatment for forming a composite metal oxide from the metal oxide of each of the above-mentioned source compounds of the catalytically active element, forming a composite metal oxide from a composite compound produced by integrating the source compounds of the catalytically active element, forming a final composite metal oxide produced, and the like. The heating is not necessarily limited to 1 time. That is, the heating may be optionally performed between and/or during the respective stages of the integration shown in (a1) to (a5), or may be additionally performed after the integration as needed. The heating temperature is usually in the range of 200 to 600 ℃.

The integration and heating may be performed before, after, or during drying, pulverization, or the like, as necessary.

Examples of the source compound of molybdenum (Mo) include: ammonium paramolybdate, molybdenum trioxide, molybdic acid, ammonium phosphomolybdate, phosphomolybdic acid, and the like.

Examples of the source compound of bismuth (Bi) include: bismuth chloride, bismuth nitrate, bismuth oxide, bismuth subcarbonate, and the like. The amount of the bismuth supply source compound to be added is preferably an amount such that b is 0.5 to 7, more preferably 0.7 to 5.0, and even more preferably 1.0 to 4.9, when a is 12 in the above formula (1). When b is within the above range, a catalyst having a high conversion rate, a high selectivity for the unsaturated aldehyde, a high selectivity for the unsaturated carboxylic acid, and a high selectivity for the unsaturated carboxylic acid can be obtained.

Examples of the source compound of cobalt (Co) include: cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt carbonate, cobalt acetate, and the like. The amount of the cobalt-supplying source compound to be added is preferably an amount such that c is 0.1 to 10, more preferably 0.3 to 5.0, and even more preferably 0.5 to 3.0, when a is 12 in the above formula (1). When c is in the above range, a catalyst having a high conversion rate, a high selectivity for the unsaturated aldehyde, a high selectivity for the unsaturated carboxylic acid, and a high selectivity for the unsaturated carboxylic acid can be obtained.

Examples of the source compound of nickel (Ni) include: nickel nitrate, nickel sulfate, nickel chloride, nickel carbonate, nickel acetate, and the like. The amount of the nickel supply source compound to be added is preferably an amount such that d is 0.1 to 10, more preferably 0.3 to 8, and even more preferably 0.5 to 5, when a is 12 in the above formula (1). When d is within the above range, a catalyst having a high conversion rate, a high selectivity for the unsaturated aldehyde, a high selectivity for the unsaturated carboxylic acid, and a high selectivity for the unsaturated carboxylic acid can be obtained.

Examples of the iron (Fe) supplying source compound include: ferric nitrate, ferric sulfate, ferric chloride, ferric acetate, and the like. The amount of the iron supply source compound to be added is preferably 0.05 to 5% by weight, more preferably 0.1 to 3% by weight, and even more preferably 0.2 to 2% by weight, when a is 12 in the above formula (1). When e is in the above range, a catalyst having a high conversion rate, a high selectivity for the unsaturated aldehyde, a high selectivity for the unsaturated carboxylic acid, and a high selectivity for the unsaturated carboxylic acid can be obtained.

The catalyst preferably further contains sodium (Na), potassium (K), and silicon (Si). That is, the catalyst preferably contains molybdenum (Mo), bismuth (Bi), cobalt (Co), nickel (Ni), iron (Fe), sodium (Na), potassium (K), and silicon (Si), and the atomic ratio of molybdenum (Mo), bismuth (Bi), cobalt (Co), nickel (Ni), iron (Fe), sodium (Na), potassium (K), and silicon (Si) in the catalyst preferably satisfies the following formula (2).

Mo_aBi_bCo_cNi_dFe_eNa_fK_gSi_h(2)

(wherein a to h represent the atomic ratio of each element, and when a is 12, f is in the range of 0 to 2, g is in the range of 0 to 2, and h is in the range of 0 to 70, and b to e are the same as b to e in formula (2), and preferred embodiments thereof are also the same.)

Examples of the sodium (Na) supplying source compound include: sodium chloride, sodium carbonate, sodium nitrate, sodium sulfate, sodium acetate, sodium borate, and the like. The amount of the sodium supply source compound to be added is preferably 0 to 2, more preferably 0.1 to 1, and even more preferably 0.2 to 0.5, where a is 12 in the above formula (2). When f is not less than the above lower limit, a catalyst having a high ratio of selectivity for the unsaturated aldehyde, selectivity for the unsaturated carboxylic acid, and selectivity for the unsaturated carboxylic acid can be obtained, and when f is not more than the above upper limit, a catalyst having an excellent conversion can be obtained.

Examples of the source compound of potassium (K) include: potassium nitrate, potassium sulfate, potassium chloride, potassium carbonate, potassium acetate, and the like. The amount of the potassium supply source compound to be added is preferably 0 to 2g, more preferably 0.05 to 1 g, and still more preferably 0.05 to 0.5 g, when a is 12 in the above formula (2). When g is not less than the above lower limit, a catalyst having a high ratio of selectivity for the unsaturated aldehyde, selectivity for the unsaturated carboxylic acid, and selectivity for the unsaturated carboxylic acid can be obtained, and when g is not more than the above upper limit, a catalyst having an excellent conversion can be obtained.

Examples of the source compound for supplying silicon (Si) include: silica, particulate silica, colloidal silica, fumed silica, and the like. The amount of the silicon supply source compound to be added is preferably 0 to 70, more preferably 5 to 50, and even more preferably 10 to 30, when a is 12 in the formula (2). When h is not less than the lower limit, the dispersibility of each component becomes good, and a catalyst having an excellent conversion rate can be obtained. When h is not more than the upper limit, a balance between the silicon content and the content of other metals can be maintained, and a catalyst having an excellent conversion can be obtained.

The step (b) is a step of molding the powder of the catalytically active component obtained in the step (a) to prepare a molded body. The powder of the catalytically active component in the step (a) has catalytic activity even when it is used as it is, but the catalyst is usually packed in a fixed bed reactor and used for gas phase catalytic oxidation, and therefore, it is preferable to carry out molding. The reason for this is that: by molding the catalyst, the operability at the time of filling and removing the catalyst into and from the reactor is improved, and an increase in pressure loss at the time of performing the gas phase catalytic oxidation can be suppressed. When the catalyst after molding is spherical, the average diameter of the catalyst is preferably 2mm to 15mm, more preferably 3mm to 10 mm.

It should be noted that the average diameter of the catalyst can be calculated as follows: the average diameter of each of the 100 catalyst particles was measured by a high-precision two-dimensional size measuring device VM-8040 manufactured by KEYENCE, Inc. to obtain an average value.

The method for forming the powder of the catalyst active ingredient may be any conventionally known method, and for example, there are two methods described below. One method is a method in which a carrier is fluidized, powder of a catalytically active component is supplied to the fluidized carrier, and the powder of the catalytically active component is supported on the surface of the carrier, and granulated and molded to produce a molded article (hereinafter, may be referred to as "rolling granulation method"). Another method is a method in which a powder of the catalytically active component is charged into a mold, and granulated and molded by applying a mechanical pressure to obtain a molded article (hereinafter, may be referred to as "tablet molding method").

In the tumbling granulation method, a binder is preferably used in order to facilitate the support of the powder of the catalyst active component on the carrier and to improve the strength of the catalyst to be produced. Examples of the carrier used in the tumbling granulation method include spherical carriers having a major axis diameter of preferably 2.5 to 10mm, more preferably 2.5 to 6mm, such as silica, silicon carbide, alumina, mullite, and corundum. Among these, the porosity of the carrier is preferably 20% to 60%, more preferably 30% to 57%, and still more preferably 40% to 55%. The water absorption of the carrier is preferably 10% to 60%, more preferably 12% to 50%, and still more preferably 15% to 40%. By setting the porosity and water absorption of the carrier to the above ranges, the catalyst active component can be easily supported on the carrier, the cumulative pore volume (a) of the produced catalyst can be easily set to be within the range of the present invention, and the ratio (a/B) of the cumulative pore volume (a) to the cumulative pore volume (B) of the pulverized product obtained by pulverizing the catalyst can be easily adjusted to be within the range of the present invention.

The tumbling granulation method is a method in which, for example, a granulator having a smooth disk or a disk having irregularities on the bottom in a fixed vessel is rotated at a high speed to vigorously stir a carrier in the vessel by repeated rotation and revolution motions, and a powder of a catalytically active component and suitable additives such as a binder, a forming aid, and a strength-enhancing material are added thereto to support the powder of the catalytically active component on the carrier. Examples of the method of adding the additive include the following methods: (1) a method of mixing powders of the above-mentioned catalyst active ingredients and additives to prepare a homogeneous mixture, and feeding the homogeneous mixture into a pelletizer to agitate; (2) a method of simultaneously feeding powder of the catalyst active ingredient and the like and the additive into a granulator and stirring; (3) a method of stirring powder of the catalyst active ingredient and the like in a granulator, and then adding the additive to the granulator and further stirring; (4) a method in which an additive is added to a powder of a catalyst active ingredient or the like to prepare an inhomogeneous mixture, and the inhomogeneous mixture is fed into a granulator and stirred; (5) a method of separately feeding powders of the catalyst active ingredient and the like and additives into a granulator at the same time, alternately or in different order and stirring them. Any method may be employed, for example, by adding the total amount of the components (1) to (5) in an appropriate combination. Among them, in (5), for example, in order to support a predetermined amount of the powder of the catalytically active component on the carrier without causing adhesion to the wall of the fixed container and aggregation of the powder of the catalytically active component, it is preferable to adjust the addition rate by using an automatic feeder or the like. In addition, the cumulative pore volume (a) of the produced catalyst is easily set within the range of the present invention, and the ratio (a/B) of the cumulative pore volume (a) to the cumulative pore volume (B) of the pulverized product obtained by pulverizing the catalyst is easily adjusted within the range of the present invention, and from this point of view, (5) is particularly preferable.

Examples of the binder include: organic binders such as ethanol, glycerin, and polyvinyl alcohol, and inorganic binders such as aqueous silica sol solutions are preferred, organic binders are preferred, glycerin and polyvinyl alcohol are more preferred, and glycerin is particularly preferred. The organic binder may be used as it is, and is preferably used in the form of an aqueous solution from the viewpoint of handling properties. The concentration of the aqueous solution is usually 0.1% by weight or more, preferably 2% by weight to 50% by weight, more preferably 3% by weight to 50% by weight, still more preferably 5% by weight to 50% by weight, and particularly preferably 7% by weight to 50% by weight. The amount of the binder used is usually 0.1 to 50 parts by weight, preferably 0.5 to 20 parts by weight, based on 100 parts by weight of the powder of the catalyst active component, and is preferably 1 to 40% by weight, more preferably 2 to 35% by weight, still more preferably 7 to 30% by weight, and particularly preferably 10 to 28% by weight, based on the catalyst. By using a binder, particularly an organic binder, in the above aqueous solution concentration and the above amount, the cumulative pore volume (a) of the catalyst to be produced can be easily adjusted within the range of the present invention, and the ratio (a/B) of the cumulative pore volume (a) to the cumulative pore volume (B) of the pulverized product obtained by pulverizing the catalyst can be easily adjusted within the range of the present invention.

Examples of the molding aid include silica, diatomaceous earth, alumina, glass, and cellulose powder. These may be used alone or in combination of two or more, and preferably in combination of two or more. The molding aid is used in an amount of usually 1 to 20 parts by weight based on 100 parts by weight of the powder of the catalyst active component. Further, the use of a strength-enhancing material such as an inorganic fiber such as a ceramic fiber or a whisker is useful for enhancing the strength of the catalyst. The strength-enhancing material is used in an amount of usually 0.5 to 20 parts by weight based on 100 parts by weight of the powder of the catalyst active component.

In the rolling granulation method, it is preferable to perform granulation under a high load so that the cumulative pore volume (a) of pores having a pore diameter of 1 μm or more and 100 μm or less in the catalyst is in a specific range and the ratio (a/B) of the cumulative pore volume (a) to the cumulative pore volume (B) of pores having a pore diameter of 1 μm or more and 100 μm or less in the crushed product obtained by crushing the catalyst and not passing through the taylor standard sieve 6 is in a specific range. The high load means: when the powder of the catalyst active component is loaded on the carrier, the impact strength between the powder of the catalyst active component and the carrier is improved, and the adhesion strength between the powder of the catalyst active component and the carrier is enhanced. From this, it is presumed that as a result, the amount of the catalyst active component entering the pores of the carrier is reduced, and the ratio (a/B) can be set to a specific range, and the cumulative pore volume (a) can be set to a specific range.

The time for granulation also depends on the granulation scale, and the longer the granulation scale, the more the time is, the preferable order is 1 to 140 minutes, 1 to 130 minutes, 1 to 120 minutes, 1 to 110 minutes, 1 to 100 minutes, 1 to 95 minutes, 1 to 90 minutes, 1 to 85 minutes, 1 to 80 minutes, 1 to 70 minutes, 1 to 60 minutes, 1 to 50 minutes, and 1 to 40 minutes. By setting the ratio (a/B) within the above range, the ratio can be set to a specific range. Further, by setting the upper limit of the granulation time to the above time, it is possible to prevent the cumulative pore volume (a) of the catalyst from decreasing due to excessive compacting of the catalyst surface, and the cumulative pore volume (a) can be set to a specific range.

In the tumbling granulation method, the catalyst active ingredient can be supported on the surface of the carrier in a concentrated manner by setting the granulation conditions to high loads, and the granulation time can be shortened, so that the catalyst-packed layer in the fixed-bed reactor can be made thinner.

In order to control the cumulative pore volume (a) of pores having a pore diameter of 1 μm or more and 100 μm or less in the catalyst, it is important to know the affinity between the carrier and the powder of the catalytically active component. The carrier generally has a high water absorption rate and is so-called hydrophilic. If the powder of the catalytically active component has the same degree of hydrophilicity, the powder of the catalytically active component easily enters the pores of the carrier, and it is difficult to control the cumulative pore volume. Therefore, by appropriately selecting a compound having low solubility in water as the source compound to be supplied in the step (a), the hydrophilicity of the powder of the catalytically active component can be adjusted, and the entry of the powder of the catalytically active component into the carrier can be controlled. Examples of the source compound having low solubility in water include bismuth subcarbonate and bismuth oxide.

The carrier used in the tablet press molding method is preferably silica, silicon carbide, alumina, mullite, corundum, or the like, and the size of the carrier is preferably the same as that of the powder of the catalyst active ingredient. In addition, in order to facilitate the support of the powder of the catalytically active component on the carrier and to improve the mechanical strength of the catalyst to be produced, it is preferable to use a binder and a forming aid. Further, it is preferable to use a pore-providing material, and by using this pore-providing material, the cumulative pore volume (a) of pores having a pore diameter of 1 μm or more and 100 μm or less in the catalyst to be produced can be controlled. In the tablet press molding method, it is preferable that a binder, a pore-providing material, and the like are sufficiently mixed in advance with the powder of the above-mentioned catalytically active component, and the mixture is molded to form a molded body.

The binder and the molding aid used in the tablet compression molding method are preferably the same as those used in the above-described tumbling granulation method, and their usage and amount are preferably the same.

Examples of the pore-providing material include organic compounds, and the following can be preferably used: cellulose powder, polyvinyl alcohol and glycerol. The pore-providing material is exposed to high temperature and decomposed and/or burned when the molded powder is fired, and is detached from the molded powder to form pores.

In the tablet-forming method, in order to control the cumulative pore volume (a) of pores having a pore diameter of 1 μm or more and 100 μm or less in the catalyst, the pressure at the time of tablet-forming is preferably set to be low. Among them, it is critical to set an appropriate pressure in consideration of the strength of the catalyst to be produced.

Next, the molded body obtained by molding the powder of the catalytically active component in the step (b) is dried and fired to obtain the catalyst. At the time of firing, the pore-providing material is detached from the catalyst particles by evaporation and combustion, and at this time, pores are formed in the catalyst particles. The firing temperature is usually from 250 to 800 ℃, preferably from 300 to 600 ℃, and the firing time is from 1 to 50 hours. In order to quickly remove the pore-providing agent detached from the catalyst particles, it is preferable to perform the firing step under air circulation. This makes it possible to obtain a catalyst having a large number of pores and high strength. Further, by quickly removing gas generated from the catalyst particles and supplying air to the catalyst particles, a uniformly calcined catalyst can be obtained. If the air flow is insufficient, the catalyst is destroyed by a pressure change at the time of detachment of the pore-providing agent, and the strength is lowered, and the conversion rate, the selectivity for the unsaturated aldehyde, and the selectivity for the unsaturated carboxylic acid are lowered.

The catalyst thus produced is supplied to a fixed bed reactor and used for a reaction for producing acrolein, an unsaturated aldehyde such as acrylic acid, and an unsaturated carboxylic acid by catalytic gas phase oxidation of an olefin such as propylene and an oxygen-containing gas. The content of the olefin in the gas supplied to the fixed bed reactor is preferably in the range of 5 to 15 vol%, and the space velocity of the olefin is preferably 50 hours^-1～320h^-1More preferably 80h^-1～320h^-1The range of (1).

The spatial velocity is a value represented by the following equation.

Space velocity SV (h)^-1) The volume flow rate of the olefin gas supplied to the reactor (0 ℃ C., 1 atm condition)/the volume of the catalyst charged into the reactor (containing no unreactive solid matter)

For example, the reaction for producing acrolein and acrylic acid by gas-phase catalytic oxidation of propylene and an oxygen-containing gas is carried out by supplying a gas composed of 5 to 15% by volume of propylene, 5 to 18% by volume of molecular oxygen, 0 to 40% by volume of steam, and 20 to 70% by volume of an inert gas such as nitrogen gas or carbon dioxide gas to a fixed bed reactor packed with the catalyst produced as described above. As the reaction conditions, it is preferable to set: a contact time with the catalyst in a temperature range of 300 to 450 ℃ and a pressure range of normal pressure to 150kPa, and 0.5 second to 5 seconds.