JP2005205401A - Composite-oxide catalyst manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite-oxide catalyst manufacturing method for manufacturing unsaturated carboxylic acid corresponding to unsaturated aldhyde by catalytically oxidizing the unsaturated aldehyde in gas phase with gas including molecular oxygen. <P>SOLUTION: The method for producing the composite-oxide catalyst having formula (1) shown below comprises the steps of heating a water solution or dispersion liquid made by dissolving and/or dispersing material compounds of metals constituting the catalyst and a material compound of Si and C including a chemical bond of Si and C into an aqueous medium at a temperature not lower than 70°C, blowing a gas including ozone into the water solution or the dispersion, then drying it to obtain powder, and molding and burning the power. The formula (1) is Mo<SB>12</SB>Nb<SB>a</SB>V<SB>b</SB>Sb<SB>c</SB>Cu<SB>d</SB>Si<SB>e</SB>C<SB>f</SB>O<SB>g</SB>, wherein a, b, c, d, e, f, and g represent the atomic ratio of the elements and, assuming that molybdenum atom is 12, 0<a≤10, 0<b≤10, 0<c≤5, 0<d≤5, 0<e≤1000, and 0<f≤1000, and g is the number determined by the oxidation degree of each component excluding Si and C among the components. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a composite oxide catalyst for producing a unsaturated carboxylic acid corresponding to a long-term stable and high yield by gas-phase catalytic oxidation of an unsaturated aldehyde with a molecular oxygen-containing gas. About.

  Conventionally, various catalysts for producing unsaturated carboxylic acids such as acrylic acid and methacrylic acid by vapor-phase catalytic oxidation of unsaturated aldehydes such as acrolein and methacrolein with molecular oxygen have been proposed. From the viewpoint of effective utilization of unsaturated aldehyde raw materials produced from olefins and rationalization of processes in the reaction, these catalysts are required to have a slightly higher unsaturated aldehyde conversion rate and the selectivity of the unsaturated carboxylic acid as the target product. . For example, when the reaction for producing acrylic acid from acrolein is produced in a plant with a scale of 60,000 tons / year, the amount of acrylic acid that is a product obtained when the conversion rate and selectivity are improved even by 0.1%. Greatly increases at the level of several hundred tons. Therefore, improvement in catalyst performance such as conversion rate and selectivity greatly contributes to effective utilization of resources and rationalization of processes even if a slight improvement.

  Conventionally, various proposals have been made with the aim of improving the catalyst performance such as the raw material conversion rate and selectivity of these reactions. For example, Patent Document 1 discloses that Mo-V-Sb produced through a process in which Mo, V and Sb are heated and reacted in an aqueous medium, and hydrogen peroxide is added to the reaction solution during or after the reaction. -Nb (or Ta) -based catalyst is disclosed, and Patent Document 2 heat-reacts Mo, V, and Sb in an aqueous medium, and molecules in the reaction solution during or after the reaction. A Mo-V-Sb-Nb (or Ta) -based catalyst manufactured through a step of blowing gaseous oxygen or a gas containing the oxygen is disclosed.

However, although these conventional complex oxide catalysts each show excellent performance, further improvement in performance of raw material unsaturated aldehyde conversion rate and unsaturated carboxylic acid selectivity is desired. Furthermore, in the case of the catalyst of Patent Document 1, it is indispensable to consider safety when using hydrogen peroxide, and in the case of the catalyst of Patent Document 2, it is necessary to blow molecular oxygen for a long time. It was sought after.
Japanese Patent Laid-Open No. 11-343261 Japanese Patent Laid-Open No. 11-343262

  The present invention is highly safe in the production process and can reduce the time required for gas injection when producing unsaturated carboxylic acid by gas phase catalytic oxidation of unsaturated aldehyde with molecular oxygen-containing gas. Provided is a method for producing a composite oxide catalyst that provides high conversion of aldehyde and high selectivity of unsaturated carboxylic acid and exhibits stable performance over a long period of time.

  The present inventor has conducted research to achieve the above object, and as a result, newly contains a Cu component and a Si—C component as catalyst components, and Mo—Nb—V—Sb—Cu in an aqueous medium. -By heating and reacting Mo, V and Sb in the presence of all components of Si-C, and blowing ozone-containing gas during the reaction, safety is high and the gas blowing time can be shortened. It has been found that it is possible to realize a method for producing a composite oxide catalyst that gives high conversion of aldehyde and high selectivity of unsaturated carboxylic acid and exhibits stable performance over a long period of time.

Thus, the present invention is characterized by the following gist.
(1) A method for producing a composite oxide catalyst having the following formula (1) used when producing a corresponding unsaturated carboxylic acid by gas phase catalytic oxidation of an unsaturated aldehyde with a molecular oxygen-containing gas. Then, an aqueous solution or dispersion obtained by dissolving and / or dispersing a raw material compound of each metal component constituting the catalyst and a raw material compound of Si and C components containing a chemical bond of Si and C in an aqueous medium is heated to 70 ° C. or higher. A method for producing a catalyst, wherein an ozone-containing gas is blown into the aqueous solution or dispersion, then the aqueous solution or dispersion is dried to form a powder, the powder is molded, and calcined.

Mo ₁₂ Nb _a V _b Sb _c Cu _d Si _e C _f O _g (1)

(In the formula, each variable has the following meaning: a, b, c, d, e, f and g represent the atomic ratio of each element, and 0 <a ≦ 10, 0 < b ≦ 10, 0 <c ≦ 5, 0 <d ≦ 5, 0 <e ≦ 1000, 0 <f ≦ 1000, g is the degree of oxidation of each component except Si and C among the above components of (1). (The number is determined by
(2) The method for producing a composite oxide catalyst according to (1), wherein the aqueous solution or dispersion is dried by spray drying.
(3) The method for producing a composite oxide catalyst according to the above (1) or (2), wherein the raw material compound of Si and C components containing a chemical bond between Si and C is silicon carbide.
(4) The composite oxide catalyst according to any one of (1) to (3), wherein the powder is molded using one or more binders selected from the group consisting of silica, graphite, and crystalline cellulose. Method.
(5) The composite oxide catalyst manufactured by the manufacturing method in any one of said (1)-(4).
(6) A method for producing a corresponding acrylic acid by vapor-phase catalytic oxidation of acrolein with a molecular oxygen-containing gas in the presence of the composite oxide catalyst according to (5) above.

  According to the present invention, when an unsaturated aldehyde is produced by gas phase catalytic oxidation with a molecular oxygen-containing gas to produce an unsaturated carboxylic acid, the safety is high and the gas blowing time can be shortened. Provided is a method for producing a composite oxide catalyst that provides high conversion of aldehyde and high selectivity of unsaturated carboxylic acid and exhibits stable performance over a long period of time.

  In particular, the conversion rate of acrolein per catalyst unit is improved, the selectivity of acrylic acid of the catalyst is improved, and a highly active composite oxide catalyst capable of efficiently performing the gas phase catalytic oxidation reaction of acrolein can be produced.

  In the present invention, Cu, Si-C components are newly contained as catalyst components, and Mo, V, and Sb are heated in the presence of all the components of Mo-Nb-V-Sb-Cu-Si-C in an aqueous medium. The reason why the above-described excellent effect can be achieved by reacting and blowing ozone-containing gas during the reaction is not necessarily clear, but is estimated as follows.

  The active component structure of this catalyst system is presumed to be an isopolyacid structure based on Mo and V, and it has been found that the addition of Sb has a great effect on the stabilization of the isopolyacid structure and the catalyst performance. However, the incorporation of Sb into the isopolyacid structure greatly affects the process conditions for the preparation of the active species precursor. In particular, maintaining Mo-V in the reduced slurry state in the preparation process slurry solution is extremely important for producing a rigid Mo-V-Sb structure. However, in the Mo-V-Sb reductant structure, the activity is remarkably lowered, and it is important to return the reductant structure to an appropriate oxidation state, and the redox state by ozone oxidation in the precursor preparation step of the active species We estimate that control is important.

  The composite oxide catalyst produced in the present invention is represented by the above formula (1). In the above formula, Mo is molybdenum, Nb is niobium, V is vanadium, Sb is antimony, Cu is copper, Si is silicon, C is carbon, O is oxygen, and a, b, c, d, e , F, and g are as described above. Among them, 1 ≦ a ≦ 8, 0.5 ≦ b ≦ 5, 0.5 ≦ c ≦ 5, 0.5 ≦ d ≦ 5, 5 ≦ e ≦ 500 and f are preferably 5 ≦ f ≦ 500.

  The composite oxide catalyst of the present invention is obtained by dissolving a raw material compound of each metal component constituting the catalyst composition represented by the formula (1) and a raw material compound of Si and C components containing a chemical bond of Si and C in an aqueous medium. The ozone-containing gas is blown into the dispersed aqueous solution or dispersion, and then the aqueous solution or dispersion is dried to form a powder, the powder is molded and fired.

  The raw material compound of each metal component in the composite oxide catalyst of the present invention is not particularly limited as long as it is a compound that becomes an oxide by calcination, either water-soluble or poorly water-soluble. Specific examples of the raw material compounds include halides, sulfates, nitrates, ammonium salts, oxides, carboxylates, ammonium carboxylates, ammonium halides, hydrogen acids, acetylacetonates, alkoxides, and the like of each component. It is done.

  Moreover, as a raw material compound of Si and C component containing a chemical bond of Si and C, silicon carbide is preferable, and specific examples thereof include green silicon carbide and black silicon carbide. Silicon carbide has a fine thermal conductivity of 0.2 to 80 microns in order to reduce heat storage due to its large thermal conductivity due to its large thermal conductivity, and to provide functions for optimizing the dispersibility of active ingredients and the pore structure. A powdery one is preferred. The Si and C raw material compounds containing the chemical bond between Si and C are different from Si and C in the molding aid described later, and do not disappear by firing. It is an important component that contributes to suppression.

As these raw material compounds, those containing each component alone may be used, or raw material compounds containing two or more kinds of components may be used.
In the present invention, first, the raw material compound is dissolved and / or dispersed in an aqueous medium to prepare an aqueous solution or dispersion containing all catalyst components. The aqueous medium is not particularly limited, but water can be preferably used. In many cases, some components do not dissolve, resulting in a slurry. The amount of water in the aqueous solution or dispersion is not particularly limited as long as the raw material compound of each component can be completely dissolved or uniformly dispersed, but drying such as the subsequent drying method, drying temperature, drying time, etc. What is necessary is just to determine suitably considering conditions. The amount of water is usually 100 to 2000 parts by weight with respect to a total of 100 parts by weight of the raw material compounds. If the amount of water is less than the above predetermined amount, the compound may not be completely dissolved or may not be uniformly mixed. Further, if the amount of water is large, there is a risk that the energy cost during the heat treatment is increased. In many cases, the dispersion in the form of a slurry is preferably aged at room temperature to 200 ° C. for 1 minute to 24 hours.

Next, the aqueous solution or dispersion is heated to a temperature of 70 ° C. or higher, preferably 80 to 100 ° C., and an ozone-containing gas is blown into the aqueous solution or dispersion. The ozone concentration in the ozone-containing gas is preferably 0.1% by volume or more, and particularly preferably 0.5% by volume or more. The ozone-containing gas flow rate depends on the amount of the aqueous solution or dispersion, but is desirably 10 to 30 liters / hour if the amount of the fluid is about 0.5 to 1 liter. The ozone-containing gas blowing is preferably continued until Mo ⁺⁵ disappears, as will be described later. The blowing time until Mo ⁺⁵ disappears depends on the amount of liquid, but is usually 0.5 hours or more, particularly 2 to 10 It's time. During the ozone-containing gas blowing, the aqueous solution or dispersion is preferably stirred.

Also in the aqueous solution or dispersion in the present invention, redox reactions of the following formulas (I) and (II) proceed at 70 ° C. or higher in the presence of Sb ³⁺ .

V ⁵⁺ + Sb ³⁺ → V ³⁺ + Sb ⁵⁺ (I)
V ³⁺ + Mo ⁺⁶ → V ⁴⁺ + Mo ⁵⁺ (II)

In this process, it is presumed that a reduced structure of Mo-V-Sb isopolyacid is generated, and the reduced body structure is oxidized by blowing in ozone-containing gas to obtain a precursor of a highly active composite oxide catalyst. In the present invention, the valences of Mo and V in the reaction solution are determined by analytical means such as an electron spin resonance spectrum, and it is preferable to continue blowing ozone-containing gas until Mo ⁵⁺ disappears.

  Next, the aqueous solution or dispersion is dried to obtain a powder. The drying is not particularly limited as long as the aqueous solution or dispersion can be sufficiently dried and a powder can be obtained. For example, drum drying, freeze drying, spray drying and the like are preferable methods. Spray drying is a method that can be preferably applied to the present invention because it can be dried from an aqueous solution or aqueous dispersion into a homogeneous powder state in a short time.

  The drying temperature varies depending on the amount of catalyst components and the amount of the aqueous solution or dispersion, but is usually 100 to 300 ° C, preferably 120 to 250 ° C, and 0.5 to 24 hours, preferably 1 to 10 hours. Do time. The particle size of the powder obtained by such drying is preferably 10 to 200 μm. For this reason, the powder can optionally be pulverized after drying.

  Subsequently, it is preferable to heat-treat the dry powder obtained above. The heat treatment temperature is usually 160 to 450 ° C., preferably 200 to 350 ° C., and the heat treatment time is usually 1 to 20 hours, preferably 2 to 10 hours. Moreover, as a specific heat treatment method, a known method is possible and there is no particular limitation. By performing such heat treatment, a catalyst with better uniformity and less powdering can be obtained.

  Next, the dried powder or the heat-treated powder after drying is formed. There is no restriction | limiting in particular in a shaping | molding method, Preferably it shape | molds using a binder. Preferred binders are selected from the group consisting of silica, graphite and crystalline cellulose. The binder is preferably used in an amount of about 1 to 50 parts by weight with respect to 100 parts by weight of the powder. If necessary, inorganic fibers such as ceramic fibers and whiskers can be used as a material for improving the mechanical strength of the catalyst particles. However, fibers that react with catalyst components such as potassium titanate whiskers and basic magnesium carbonate whiskers are not preferred. For improving the strength, ceramic fiber is particularly preferable. The amount of these fibers used is preferably 1 to 30 parts by weight with respect to 100 parts by weight of the powder. The molding aid is usually used in advance mixed with powder.

  For the powder mixed with a molding aid such as a binder, an appropriate method such as (A) tableting molding, (B) extrusion molding, (C) spherical or other desired well-known support molding method can be employed. As the molded body, an appropriate shape such as a spherical shape, a cylindrical shape, or a ring shape is preferably selected.

  Next, the molded product thus molded is fired to obtain a composite oxide catalyst. The firing temperature can be usually 250 to 500 ° C, preferably 300 to 420 ° C, and the firing time is 1 to 50 hours. Firing can be performed in an atmosphere in the presence of an inert gas or molecular oxygen. If the calcination temperature is too low, the remaining of the ammonium salt derived from the raw material becomes a problem, and if it is too high, the active component structure is crystallized and the structure is destroyed, resulting in a decrease in catalyst performance. The molecular oxygen in the atmospheric gas is preferably 10% by volume or less, and if the content of molecular oxygen exceeds 10% by volume, the activity of the catalyst may be insufficient. The content of molecular oxygen may be 0% by volume, but is preferably 0.05% by volume or more.

  The means for producing a corresponding unsaturated carboxylic acid by vapor phase oxidation of an unsaturated aldehyde using molecular oxygen or a molecular oxygen-containing gas using the catalyst produced according to the present invention is performed by an existing method. be able to. For example, a fixed bed tube reactor is used as the reactor. In this case, the reaction may be a single flow method or a recycle method through the reactor, and can be carried out under conditions generally used for this type of reaction.

For example, a mixed gas composed of 4 to 8% by volume of acrolein, 6 to 10% by volume of molecular oxygen, 10 to 20% by volume of water vapor, 62 to 80% by volume of an inert gas such as nitrogen or carbon dioxide, and the like preferably has an inner diameter. It is introduced at a space velocity (SV) of 300 to 5000 hr ⁻¹ under a pressure of 250 to 450 ° C. and a pressure of 0.1 to ¹ MPa into a catalyst layer filled in each reaction zone of each reaction tube of 15 to 50 mm. In the present invention, it is possible to operate under high load reaction conditions, for example, higher raw material gas concentration or high space velocity conditions in order to increase productivity. Thus, acrylic acid can be produced with high selectivity and high yield by the catalyst produced in the present invention.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention should not be construed as being limited to these examples. The acrolein conversion rate, acrylic acid selectivity, and acrylic acid yield are defined by the following formulas.
Acrolein conversion (mol%) = 100 × (number of moles of reacted acrolein) / (number of moles of supplied acrolein)
Acrylic acid selectivity (mol%) = 100 × (number of moles of acrylic acid produced) / (number of moles of converted acrolein)
Acrylic acid yield (mol%) = 100 × (number of moles of acrylic acid produced) / (number of moles of acrolein supplied)

Example A composite metal oxide in which the catalyst composition excluding oxygen was Mo ₁₂ Nb ₂ V _3.5 Cu ₂ Sb ₁ Si ₁₅₀ C ₁₅₀ was prepared as follows.
First, 1124 ml of pure water was heated to 80 ° C., and 298.7 g of ammonium paramolybdate and 57.94 g of ammonium metavanadate were dissolved with stirring. An aqueous solution in which 32.45 g of niobium ammonium oxalate was dissolved in 324 ml of pure water at 80 ° C. was added to this aqueous solution, and an aqueous solution in which 70.24 g of copper sulfate was dissolved in 95 ml of pure water at 80 ° C. was further added. To this aqueous solution, 20.54 g of antimony trioxide was added and stirred. This liquid has a maximum particle size of 63 microns or less, a particle size of 50% or less at a cumulative height of 3%, a particle size of 25 ± 2.0 microns at a cumulative height of 50%, and a particle size of 16 microns at a cumulative height of 94%. 848 g of silicon carbide powder having the following particle size distribution characteristics was added and sufficiently stirred and mixed to obtain a slurry dispersion.

  After this slurry-like dispersion was heated to 90 ° C., ozone-containing gas was blown. The ozone concentration in the ozone-containing gas was 3% by volume, and the ozone-containing gas flow rate was 15 liters / hour. The pentavalent Mo in the liquid was detected by electron spin resonance spectrum, and the ozone-containing gas was blown in continuously for 4 hours while stirring the liquid until the pentavalent Mo disappeared.

  The slurry liquid thus obtained was heated to 90 ° C. and dried. After heat-treating this at 200 ° C., 1.5% by weight of graphite was added and mixed, and formed into a cylindrical shape having a height of 4 mm and a diameter of 5 mm with a small tableting machine, and this was flown in a nitrogen stream in a firing furnace. The catalyst was produced by calcination at 380 ° C. for 3 hours.

In order to evaluate the obtained catalyst, 0.3 g of a 20-28 mesh pulverized and sized particle was charged into a U-shaped reaction tube having an inner diameter of 4 mm, and this reaction tube was heated in a night bath (temperature: 280). And introducing a composition gas of acrolein: 3.4% by volume, oxygen: 9.3% by volume, steam: 41.5% by volume and nitrogen gas: 45.8% by volume, and SV (space velocity; unit) The reaction was performed at a flow rate of the raw material gas per hour / apparent volume of the packed catalyst) of 20000 / hr ⁻¹ .

The nighter bath is a salt bath in which a reaction tube is placed in a heat medium made of an alkali metal nitrate and reacted. This heat medium melts at 200 ° C. or higher, can be used up to 400 ° C., and has a good heat removal efficiency.
As a result of the reaction, the acrolein conversion rate was 99.0%, the acrylic acid selectivity was 98.5%, and the acrylic acid yield was 97.5%.

Comparative Example A catalyst having the same composition as the example was obtained in the same manner as in the example except that the ozone-containing gas was not blown into the slurry dispersion in the catalyst production process.
Acrylic acid was produced from this catalyst under the same conditions as in the Examples. The reaction results were as follows: acrolein conversion = 99.0%, acrylic acid selectivity = 95.5%, and acrylic acid yield = 94.5% at a reaction bath temperature of 306 ° C.

  Thus, in the example in which the ozone-containing gas was blown, compared with the comparative example in which the blow was not carried out, the acrolein conversion, acrylic acid selectivity, and acrylic acid yield were all excellent, and the gas phase of acrolein The catalytic oxidation reaction was performed efficiently.

  The catalyst produced by the process of the present invention is used for the gas phase catalytic oxidation of unsaturated aldehydes with molecular oxygen-containing gas to produce the corresponding unsaturated carboxylic acid in high yield. Produced unsaturated carboxylic acids such as acrylic acid are used in a wide range of applications as raw materials for various chemicals, monomers for general-purpose resins, monomers for functional resins such as water-absorbing resins, flocculants, and thickeners. Is done.

Claims (6)

A method for producing a composite oxide catalyst having the following formula (1) used for producing a corresponding unsaturated carboxylic acid by vapor-phase catalytic oxidation of an unsaturated aldehyde with a molecular oxygen-containing gas, An aqueous solution or dispersion obtained by dissolving and / or dispersing a raw material compound of each metal component and a raw material compound of Si and C components containing a chemical bond between Si and C in an aqueous medium is heated to 70 ° C. or higher, and the aqueous solution Alternatively, an ozone-containing gas is blown into the dispersion, then the aqueous solution or dispersion is dried to form a powder, the powder is molded, and calcined.

Mo ₁₂ Nb _a V _b Sb _c Cu _d Si _e C _f O _g (1)

(In the formula, each variable has the following meaning: a, b, c, d, e, f, and g represent the atomic ratio of each element, and 0 <a ≦ 10, 0 < b ≦ 10, 0 <c ≦ 5, 0 <d ≦ 5, 0 <e ≦ 1000, 0 <f ≦ 1000, g is the degree of oxidation of each component except Si and C among the above components of (1). (The number is determined by   The method for producing a composite oxide catalyst according to claim 1, wherein the aqueous solution or dispersion is dried by spray drying.   3. The method for producing a composite oxide catalyst according to claim 1, wherein the raw material compound of the Si and C components including the chemical bond between Si and C is silicon carbide.   The method for producing a composite oxide catalyst according to any one of claims 1 to 3, wherein the powder is formed using one or more binders selected from the group consisting of silica, graphite and crystalline cellulose.   The composite oxide catalyst manufactured by the manufacturing method in any one of Claims 1-4.   A method for producing a corresponding acrylic acid by vapor-phase catalytic oxidation of acrolein with a molecular oxygen-containing gas in the presence of the composite oxide catalyst according to claim 5.