JP2018153777A - Acrylic acid production catalyst and method for producing acrylic acid using the catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst which is excellent in mechanical strength and degree of pulverization for producing acrylic acid, can produce a target product in high yield, and has low health hazard. .. The present invention is a catalyst in which a catalytically active component containing molybdenum and vanadium as essential components and an inorganic fiber are supported on an inert carrier, wherein the inorganic fiber contains a biosoluble fiber. .. [Selection diagram] None

Description

  The present invention relates to a catalyst suitable for producing acrylic acid by catalytic gas phase oxidation of propane and / or acrolein in the presence of molecular oxygen or a molecular oxygen-containing gas, and to production of acrylic acid using the catalyst.

  Acrylic acid is important as a raw material for various synthetic resins, paints, plasticizers, and the like, and in recent years, its importance is increasing as a raw material for water-absorbing resins. As a method for producing acrylic acid, a two-stage oxidation method is generally used in which acrolein is first obtained by catalytic vapor phase oxidation of propylene, and then acrylic acid is produced by catalytic vapor phase oxidation of the obtained acrolein. . In recent years, other proposals have been made on a method for producing acrylic acid in a single step by catalytic gas phase oxidation of propane using propane which is cheaper than propylene as a raw material.

In the second-stage reaction in the two-stage oxidation method from propylene, that is, the catalytic gas-phase oxidation of acrolein or the one-stage catalytic gas-phase oxidation reaction from propane, a molybdenum-vanadium catalyst is generally used. As a form of these catalysts, there are a molded catalyst formed by molding only a catalytic active component into a fixed shape, and a supported catalyst formed by supporting a catalytic active component on the surface of an inert carrier having a fixed shape. From the viewpoint of reducing the thickness of the catalyst layer and suppressing the yield reduction due to the sequential oxidation of the target product, the supported catalyst is particularly preferred.
However, on the other hand, since the supported catalyst is in a form in which the catalytically active component is supported on the inert carrier, the catalytically active component is inactivated by, for example, an impact when dropping and filling the catalyst into the reactor. There are disadvantages that the catalyst is easily peeled from above, and that the catalytically active component is pulverized by contact between the catalysts in the catalyst transport process and filling process, or friction between the catalyst and the wall surface. These exfoliated or pulverized catalytically active components cause problems such as an increase in pressure loss of the reactor, clogging of the reaction tube, and performance deterioration due to loss of effective catalytically active components.

In this way, suppressing and preventing problems caused by the low mechanical strength of the catalyst is an extremely important issue from the viewpoint of industrial acrylic acid production, and various proposals aimed at improving the strength of the catalyst. Has been. For example, Patent Document 1 contains at least two types of inorganic fibers having different average diameters, specifically, inorganic fibers having an average fiber diameter of less than 1.0 μm and inorganic fibers having a diameter of 1.5 to 7 μm together with a catalytic active component. A catalyst is disclosed that improves the mechanical strength and the degree of powdering, and can produce the target product in a high yield. Patent Document 2 discloses a catalyst obtained by molding and calcining a dried product obtained from a starting raw material mixture, wherein the weight loss rate of the dried product is 5 to 40% by mass. In Patent Document 3, ceramic fibers, whiskers and the like can be used as a material for improving the mechanical strength of catalyst particles, and it is described in the specification that ceramic fibers are particularly preferable. Similarly, Patent Document 4 describes in its specification that inorganic fibers inert to the reaction gas, such as ceramic fibers or whiskers, are used for improving the mechanical strength of the catalyst.
On the other hand, in recent years, development of inorganic fibers having biosolubility that does not cause problems even when inhaled by the human body or is difficult to occur due to concern about the harmful effects of ceramic fibers on the living body has been promoted. 5 discloses an inorganic fiber having a specific composition excellent in solubility in physiological saline having a pH of 4.5.

International Publication No. 2012/073584 JP 2004-243213 A JP 2003-200055 A International Publication No. 2010/052909 International Publication No. 2013/132858

As described above, various studies and proposals for improving the strength of the catalyst have been made for acrylic acid production catalysts. Often, fibrous chemicals such as silica-alumina fibers are used as mechanical strength improvers. Ceramic fibers such as, and whiskers such as silicon carbide whiskers are added.
On the other hand, in recent years, due to concerns about carcinogenicity, regulations for such fibrous chemical substances have been tightened. For example, the silica-alumina fibers mentioned above fall under the category of refractory ceramic fibers, and in the EU region, they are registered as substances of very high concern (SVHC), and their use is likely to be restricted in the future. Similarly in Japan, it has been designated as a specified chemical substance under the Industrial Safety and Health Act since 2015, and measures such as dust emission control measures, work environment measurements, and worker health checkups to prevent health hazards for the handlers. Management is obligatory. The above-mentioned silicon carbide whiskers are also classified as A2 in the carcinogenicity classification of ACGIH, and are considered substances that are suspected to be carcinogenic to humans. Alumina fiber is also used as a reinforcing material for the catalyst for acrylic acid production. However, since this fiber has a new history, there are few data on human health effects and sufficient safety has been confirmed. hard.

  Under such circumstances, various fibers are included in handling operations of various fibers in the production process of the catalyst, filling the catalyst containing the various fibers into the chemical conversion device, extracting operations, discarding the extracted catalyst, and the like. There is a high risk of health hazards to workers exposed to catalyst dust, and there is a need for a catalyst for the production of acrylic acid that is made of a safer and less hazardous health hazard.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a catalyst for acrylic acid production comprising a catalytically active component containing molybdenum and vanadium as essential components and an inorganic fiber supported on an inert carrier. By using a fiber that is biosoluble in the inorganic fiber, the health hazard is low, the target product can be produced in a high yield, and it is sufficient as well as the conventionally used fiber. The inventors have found that an acrylic acid production catalyst having catalyst strength can be obtained, and have led to the development of the present invention.
It is known that biosoluble fibers are easily decomposed in the living body, so that the residence time in the body is short and hardly cause health damage. It is said that the biosolubility increases when there are many alkaline earth components such as magnesium and calcium. Especially, what is called alkaline earth silicate wool (AES fiber) is not classified because of its carcinogenicity in the GHS classification. High nature.

  According to the present invention, as a catalyst suitable for producing acrylic acid by catalytic gas phase oxidation of propane and / or acrolein in the presence of molecular oxygen or molecular oxygen-containing gas, mechanical strength, degree of pulverization It is possible to produce a catalyst with excellent yield, high yield of the target product and low health hazards, and reduce the risk of health hazards to workers during the manufacturing and handling of the catalyst. It becomes possible to do.

  Hereinafter, the catalyst for producing acrylic acid according to the present invention and the method for producing acrylic acid using the catalyst will be described in detail. However, the scope of the present invention is not limited to these descriptions, and the examples other than the following examples are also included. The present invention can be changed and implemented as appropriate without departing from the spirit of the present invention.

The catalyst for producing acrylic acid in the present invention contains molybdenum and vanadium as essential components. As a more specific catalytic active component, the following general formula (1)
_{Mo 12 V a A b B c} C d D e O x (1)
(Where Mo is molybdenum, V is vanadium, A is at least one element selected from the group consisting of tungsten and niobium, and B is selected from chromium, manganese, iron, cobalt, nickel, copper, zinc, and bismuth. And at least one element selected from antimony, tin, tellurium, and phosphorus, D is at least one element selected from silicon, aluminum, titanium, cerium, and zirconium, and O is oxygen. A, b, c, d, e and x each represent an atomic ratio of V, A, B, C, D and O, and 0 <a ≦ 14, 0 ≦ b ≦ 12, 0 ≦ c ≦ 6, Preferred is a catalytically active component represented by 0 ≦ d ≦ 6, 0 ≦ e ≦ 50, and x is a value determined by the oxidation state of each element.

The catalyst for producing acrylic acid in the present invention is a catalyst obtained by supporting inorganic fibers on an inert carrier, and the inorganic fibers contain biosoluble fibers. The biosoluble fiber is selected from Na ₂ O, K ₂ O, CaO, MgO, SrO, and BaO from the viewpoint of obtaining a catalyst having high mechanical strength and high biosolubility. comprises at least one, and a content of their biosoluble fibers is 18 to 43 mass%, further with containing SiO _2, the content of the biosoluble fibers are 50 to 82 wt% It is preferable that More preferably, the biosoluble fiber contains MgO and SrO as essential components. For example, there is alkaline earth silicate wool as a fiber corresponding to this. In general, it is known that the biosolubility increases when the content of alkaline earth is large.

  The inorganic fiber does not necessarily need to be one type, and two or more types of biosoluble fibers may be used. Furthermore, conventionally used ceramic fibers such as silica-alumina fibers and alumina fibers, and carbonized fibers may be used. It is also possible to use a whisker such as silicon whisker and a biosoluble fiber in combination, and there is an effect of reducing the amount of ceramic fiber and whisker that are highly harmful to health.

  The content of the inorganic fiber is preferably 0.5 to 30% by mass with respect to the catalytically active component. If the content is lower than 0.5% by mass, the mechanical strength of the catalyst tends to decrease, and if it exceeds 30% by mass, the catalytically active component tends to be excessively diluted and the catalytic activity and catalyst life tend to decrease. It is.

The average fiber length of the inorganic fibers is not particularly limited, but is preferably 1 to 1000 μm, more preferably 10 to 500 μm from the viewpoint of dispersibility in the catalyst. However, even an inorganic fiber having an average fiber length exceeding 1000 μm may be used so that the fiber is cut by stirring vigorously with a homomixer or the like, and as a result, the average fiber diameter falls within the above range.
The average fiber diameter of the inorganic fibers is not particularly limited, but is preferably 7 μm or less, more preferably 1.5 to 7 μm, and further preferably 2 to 5 μm, in view of high strength of the obtained catalyst. Preferably there is.

The method for adding the inorganic fiber or the biosoluble fiber is not particularly limited, and any method can be used as long as it can be uniformly dispersed in the catalytically active component. For example, the catalyst active component represented by the general formula (1) may be added to the starting raw material mixture, or may be added to the catalyst precursor or the fired product obtained after drying or further firing. Among these, the method of adding and mixing to the starting raw material mixture is preferable from the viewpoint of fiber dispersibility. The fibers may be added all at once, or may be added separately, for example, a part of the fiber is added to the starting material mixture, and the catalyst precursor or calcination obtained after drying or further calcination of the starting material mixture The remaining fibers may be added to the object.
The catalyst of the present invention is generally used for the preparation of an acrylic acid production catalyst or an unsaturated carboxylic acid production catalyst supported on a known inert carrier, except that it contains biosoluble fibers. It can be produced according to the method.

  Specifically, as a raw material of the catalytically active component represented by the general formula (1), oxides and hydroxides of each component element, ammonium salts, nitrates, carbonates, sulfates, organic acid salts and the like, These aqueous solutions, sols, and the like, or compounds containing a plurality of elements can be used, and the starting raw material mixture is prepared by dissolving or suspending these raw materials in a solvent such as water.

  The starting material mixture is prepared by a method of mixing the above starting materials sequentially with water, a method of preparing a plurality of aqueous solutions or aquatic slurries according to the types of starting materials, and sequentially mixing them. What is necessary is just to prepare by the method generally used for manufacture. There is no restriction | limiting in particular about the mixing order of starting materials, temperature, pressure, pH, etc., According to a starting material, it can select suitably. Moreover, it is preferable to control pH within the range of 4-10, adding nitrogen-containing compounds, such as nitric acid, ammonia, ammonium nitrate, and ammonium carbonate suitably.

  Next, if necessary, the obtained starting material mixture is dried by various methods such as heating and decompression to obtain a catalyst precursor. As a drying method by heating, for example, a dry powder may be obtained using a spray dryer, a drum dryer or the like, or heated in an air stream using a box dryer, a tunnel dryer, or the like. A block-like or flake-like dried product may be obtained. Alternatively, a method of once concentrating the starting raw material mixture and evaporating to dryness to obtain a cake-like solid and further subjecting the solid to the above heat treatment can also be employed. As a drying method by reduced pressure, for example, a block or powdery catalyst precursor can be obtained using a vacuum dryer.

  The obtained dried product is sent to a subsequent supporting step through a pulverization step and a classification step for obtaining a powder having an appropriate particle size as required. The particle size of the catalyst precursor at that time is not particularly limited, but is preferably 500 μm or less, preferably 200 μm or less, and more preferably 100 μm or less in terms of excellent supportability. Moreover, before sending to the subsequent carrying | support process, the obtained catalyst precursor is once baked and it is good also as a baked product. For example, the firing temperature is 250 to 600 ° C., preferably 300 to 550 ° C., more preferably 350 to 450 ° C., and the firing time is preferably 1 to 20 hours. Such a catalyst precursor powder is once calcined, supported on an inert carrier, and calcined again. This technique is known as two-stage calcining.

  There is no particular limitation on the method for supporting the inert carrier in the supporting step. For example, the starting material mixture is evaporated while heating and stirring the inert carrier having a certain shape described in Japanese Patent Publication No. 49-11371. According to a method of drying and adhering to a support, or a method described in JP-A No. 64-85139, JP-A No. 8-29997 or JP-A No. 2004-136267, the catalyst precursor is formed on an inert support. Or the granulation method etc. which carry | support the baked product in powder form are employable.

  Examples of the inert carrier include alumina, silica, silica-alumina, titania, magnesia, steatite, cordierite, silica-magnesia, silicon carbide, silicon nitride, zeolite, and the like. There is no restriction | limiting in particular about the shape, The thing of well-known shapes, such as spherical shape, cylinder shape, and ring shape, can be used. The amount of the catalytically active component supported on the inert carrier is not particularly limited, but is preferably in the range of 10 to 300% by mass, and more preferably in the range of 20 to 200% by mass.

  In the supporting step, a molding aid and a binder for improving the supportability, a pore forming agent for forming appropriate pores in the catalyst, and the like can be used. Specific examples include organic compounds such as ethylene glycol, glycerin, propionic acid, maleic acid, benzyl alcohol, propyl alcohol, butyl alcohol, phenols, celluloses such as cellulose and ethyl cellulose, water, nitric acid, ammonium nitrate, and ammonium carbonate. Can be mentioned. These may be used alone or in combination of two or more.

  The carrier obtained in the above supporting step is sent to the subsequent drying step and / or firing step. The drying step is not necessarily required, and the baking may be performed without going through the drying step. In addition, the firing step is not necessarily required, and in the case of the support using the fired product of the catalyst precursor in the supporting step, only the drying step for removing the molding aid and binder used in the supporting step may be used.

  In the drying step, the carrier is dried in a stream of air, inert gas such as nitrogen, or other nitrogen oxides using a commonly used box dryer, tunnel dryer, or the like. The drying temperature is 80 to 300 ° C, preferably 100 to 250 ° C, and the drying time is preferably 1 to 20 hours.

  In the firing step, the firing furnace to be used is not particularly limited, and a generally used box-type firing furnace or tunnel-type firing furnace may be used. The firing temperature is 250 to 600 ° C, preferably 300 to 550 ° C, more preferably 350 to 450 ° C, and the firing time is preferably 1 to 20 hours. The firing atmosphere can be appropriately selected from an air atmosphere, an air flow, an inert gas atmosphere, a superheated steam atmosphere, and the like.

The reactor used for producing acrylic acid by catalytic gas phase oxidation of acrolein or propane-containing gas in the presence of molecular oxygen in the present invention is not particularly limited, but is usually a fixed bed reactor. In particular, a fixed bed multitubular reactor is preferred.
When the catalyst is charged into the reactor, it is not always necessary to use a single catalyst. For example, a plurality of types of catalysts having different activities are used, and these are charged in the order of different activities, or a part of the catalyst is inactive. It may be diluted with a carrier or the like.

The reaction conditions in the present invention are not particularly limited, and any conditions generally used for this type of reaction can be used. For example, the reaction raw material gas is 1 to 15% by volume, preferably 4 to 12% by volume acrolein and / or propane, 0.5 to 25% by volume, preferably 2 to 20% by volume molecular oxygen, and 0 to 30% by volume. %, Preferably 0 to 25% by volume of water vapor, with the balance being an inert gas such as nitrogen at a temperature of 200 to 400 ° C. under a pressure of 0.1 to 1.0 MPa and 300 to 5,000 h ^{− The} catalyst may be contacted at a space velocity of ¹ (STP).
As a reaction raw material gas, not only a mixed gas composed of acrolein and / or propane, molecular oxygen and an inert gas, but also, for example, a mixed gas containing acrolein obtained by a dehydration reaction of glycerin or a catalytic oxidation reaction of propylene is used. You can also. In addition, air or molecular oxygen can be added to the mixed gas as necessary.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. Hereinafter, for convenience, “parts by mass” may be referred to as “parts”. The conversion rates and yields in the examples and comparative examples were determined by the following equations.
Conversion rate [mol%]
= (Mole number of reacted acrolein) / (Mole number of supplied acrolein) × 100
Yield [mol%]
= (Number of moles of acrylic acid produced) / (number of moles of acrolein supplied) × 100
[Measuring method of mechanical strength of catalyst]
A stainless steel reaction tube having an inner diameter of 25 mm and a length of 5000 mm is installed in the vertical direction, and the lower end of the reaction tube is closed with a stainless steel receiving plate having a thickness of 1 mm. About 50 g of the catalyst is dropped into the reaction tube from the upper end of the reaction tube, the stainless steel receiving plate at the lower end of the reaction tube is removed, and the catalyst is gently extracted from the reaction tube. The extracted catalyst was passed through a sieve having an opening of 5 mm, and the mass (g) of the catalyst remaining on the sieve was weighed.
Mechanical strength (mass%) = (mass of catalyst remaining on sieve (g) / mass of catalyst dropped from upper end of reaction tube (g)) × 100
[Measuring method of catalyst fineness]
About 200 g of catalyst is placed in a cylindrical drum-shaped stainless steel sealed container having a vertical cross section of a circle having a diameter of 150 mm and a horizontal width of 150 mm. The container was rotated at 150 rpm for 30 minutes around its central axis in the horizontal direction, and then the catalyst was taken out from the container, passed through a sieve having an opening of 2 mm, and the weight (g) of the catalyst remaining in the sieve shape was weighed.
Degree of pulverization (mass%) = [(mass of catalyst put in container (g) −mass of catalyst remaining on sieve (g)) / mass of catalyst put in container (g)] × 100

<Example 1>
[Catalyst preparation]
While heating and stirring 10,000 parts of pure water, 1000 parts of ammonium molybdate, 331 parts of ammonium metavanadate, and 166 parts of ammonium paratungstate were dissolved. Separately, 148 parts of copper nitrate was dissolved while heating and mixing 400 parts of pure water. The obtained two aqueous solutions were mixed, and 95 parts of iron nitrate and 21 parts of antimony trioxide were further added. Further, as a reinforcing material, the carcinogenicity according to the GHS classification is out of the category, and an alkaline earth comprising a composition having an average fiber diameter of 3 μm, an average fiber length of 50 μm, CaO, MgO and SrO in total 25% by mass, and SiO ₂ in 75% by mass. Silicate wool was added so that it might become 10 mass% with respect to a catalyst active component, and the starting raw material liquid mixture was obtained. The obtained starting material mixture was dried with a spray dryer, and then the obtained dried product was pulverized and sieved to 100 μm or less to obtain a catalyst precursor powder. Into a dish type rolling granulator, 2000 parts of a spherical alumina carrier having an average diameter of 5.2 mm is put, and then the powder of the catalyst precursor is sprayed while spraying pure water of a binder while rotating the rotating dish. After gradually being introduced and supported on a carrier, it was dried with hot air of about 90 ° C. to obtain a supported product. The obtained support was calcined at 400 ° C. for 6 hours in an air atmosphere to obtain Catalyst A1. The catalyst loading was about 35% by mass, and the metal element composition of the catalytically active component excluding oxygen was as follows.
Catalyst A1: Mo ₁₂ V _6.0 W _1.3 Cu _1.3 Fe _0.5 Sb _0.3
The loading rate was determined by the following formula.
Support rate (mass%) = mass of supported catalyst powder (g) / mass of support used (g) × 100
Table 1 shows the mechanical strength and degree of pulverization of this catalyst A1.

[Reactor]
A reactor comprising a steel reaction tube having a total length of 3000 mm and an inner diameter of 25 mm and a shell for flowing a heat medium covering the steel reaction tube was prepared in the vertical direction. The catalyst A1 obtained from the upper part of the reaction tube was dropped and filled so that the layer length was 2800 mm.
[Oxidation reaction]
From the lower part of the reaction tube filled with the catalyst, a mixed gas composed of 6% by volume of acrolein, 7.5% by volume of oxygen, 20% by volume of water vapor, and the balance of an inert gas such as nitrogen is a space velocity of 2000 hr ⁻¹ (standard state). And acrolein oxidation reaction was carried out. At that time, the heat medium temperature (reaction temperature) was adjusted so that the acrolein conversion was about 98.5 mol%. The results are shown in Table 2.

<Comparative Example 1>
In Example 1, it prepared like Example 1 except having not added the fiber used as a reinforcing material, and obtained catalyst R1. The loading ratio of this catalyst R1 and the metal element composition of the catalytically active component excluding oxygen were the same as those of the catalyst A1. Table 1 shows the mechanical strength and the degree of pulverization of the catalyst R1. Catalyst R1 was charged into the reactor in the same manner as in Example 1, and an acrolein oxidation reaction was performed under the same conditions. The results are shown in Table 2.

<Comparative Example 2>
In Example 1, refractory ceramic fibers (silica-alumina fibers) having a carcinogenicity according to the GHS classification of Category 2 and having an average fiber diameter of 2 μm and an average fiber length of 50 μm were added instead of alkaline earth silicate wool as a reinforcing material. Except for this, the catalyst R2 was obtained in the same manner as in Example 1. The catalyst R2 loading rate and the metal element composition of the catalytically active component excluding oxygen were the same as those of the catalyst A1. Table 1 shows the mechanical strength and degree of pulverization of the catalyst R2. Catalyst R2 was charged into the reactor in the same manner as in Example 1, and an acrolein oxidation reaction was performed under the same conditions. The results are shown in Table 2.

<Example 2>
In Example 1, a catalyst A2 was obtained in the same manner as in Example 1 except that the reinforcing material, alkaline earth silicate wool, was added in an amount of 25% by mass with respect to the catalytically active component. The catalyst A2 loading ratio and the metal element composition of the catalytically active component excluding oxygen were the same as those of the catalyst A1. Table 1 shows the mechanical strength and the degree of dusting of the catalyst A2. Catalyst A2 was charged into the reactor in the same manner as in Example 1, and an acrolein oxidation reaction was performed under the same conditions. The results are shown in Table 2.

<Example 3>
In Example 1, a catalyst A3 was obtained in the same manner as in Example 1 except that alkali earth silicate wool as a reinforcing material was added to 1% by mass with respect to the catalytically active component. The supporting rate of this catalyst A3 and the metal element composition of the catalytically active component excluding oxygen were the same as those of the catalyst A1. Table 1 shows the mechanical strength and the degree of pulverization of the catalyst A3. Catalyst A3 was charged into the reactor in the same manner as in Example 1, and an acrolein oxidation reaction was performed under the same conditions. The results are shown in Table 2.

Claims (5)

  A catalyst for producing acrylic acid, comprising a catalyst active component containing molybdenum and vanadium as essential components and an inorganic fiber supported on an inert carrier, wherein the inorganic fiber contains a biosoluble fiber. . The biosoluble fiber contains at least one selected from Na ₂ O, K ₂ O, CaO, MgO, SrO, and BaO, and the content of the biosoluble fiber in the biosoluble fiber is 18 to 43% by mass. The catalyst according to claim 1, wherein the catalyst further contains SiO ₂ and its content in the biosoluble fiber is 50 to 82% by mass.   The catalyst according to claim 2, wherein the biosoluble fiber contains MgO and SrO as essential components.   The catalyst according to any one of claims 1 to 3, wherein a content of the inorganic fiber is 0.5% by mass to 30% by mass with respect to the catalytically active component.   The manufacturing method of acrylic acid using the catalyst in any one of Claims 1-4.