JP2003103168A - Producing method of catalyst for producing acrylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a producing method of catalyst which is used for production of acrylic acid based on gas phase oxidation of propane and obtains acrylic acid at high yield. SOLUTION: In this producing method of catalyst for producing acrylic acid, 5-80 mass% of total used quantity of Mo<6+> compound is used when Mo<6+> compound, V<5+> compound and Sb<3+> compound are allowed to react at >=90 deg.C in an aqueous medium, the heating of the gained aqueous reaction liquid is stopped, then, the remaining Mo<6+> compound is added into the aqueous solution and is mixed uniformly, thereafter, the gained aqueous reaction liquid is admixed with Nb compound, is further vaporized and dried and the dried material is finally sintered.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a catalyst applied to a method for producing acrylic acid by gas phase catalytic oxidation of propane. [0002] Generally, acrylic acid is
Acrolein is produced by contacting propylene with oxygen in the presence of a catalyst to produce acrolein, which is then produced by two-stage oxidation in which this is contacted with oxygen. On the other hand, in recent years, due to the price difference between propane and propylene or the complexity of the process involved in the two-stage oxidation, a method of producing acrylic acid in one step using propane as a starting material has been studied, and is used in that case. Many proposals have been made regarding catalysts. As a representative example, a [V, P, Te] -based catalyst [Catalysis.Today, 13, 679 (19)
92)], AgBiVMoO (JP-A-2-83348), BiMo12V5Nb0.5SbKOn (US
P, No. 5,198,580), [Mo, Te, V, Nb] (JP-A-6-279351) and [Mo, S
b, V, Nb] (JP-A-9-316023) catalysts. [0003] However, the above-mentioned catalyst has problems that the yield of the target acrylic acid is insufficient and that the life of the catalyst itself is short. For example, Japanese Patent Application Laid-Open No. 6-279351 proposes [Mo,
According to the [Te, V, Nb] -based catalyst, acrylic acid can be obtained in a high yield, but the activity of the catalyst is liable to be deteriorated with time because Te is easily evaporated. [Mo, Sb, V, Nb]
As a method for preparing a catalyst based on the present invention, a method of reacting molybdenum, vanadium and an antimony compound at a temperature of 70 ° C. or more by the present inventor (JP-A-10-137585); While injecting a gas containing oxygen (Japanese Unexamined Patent Publication No. Hei 10-230164), or while reacting molybdenum, vanadium and antimony compounds at a temperature of 70 ° C. or more, or after completion of the reaction. Addition method (JP-A-11-28563)
No. 6). However, the yield of acrylic acid cannot be said to be sufficiently high, and there is room for improvement in terms of the yield of acrylic acid and the reproducibility of catalyst production. DISCLOSURE OF THE INVENTION In order to obtain a catalyst capable of producing acrylic acid in a high yield by catalytic oxidation of propane, the present inventors have prepared a method for preparing a slurry comprising Mo, Sb, and V components. As a result of intensive studies, the present invention has been completed. That is, the present invention employs a method comprising the following steps (1), (2) and (3) when producing a catalyst for producing acrylic acid comprising a metal oxide represented by the following composition formula. And a method for producing a catalyst for producing acrylic acid. Step (1): Mo ⁶⁺ compound, V ⁵⁺ as metal-containing compound
The compound and the Sb ³⁺ compound were used, and after heating 5 to 80% by mass of the Mo ⁶⁺ compound, the V ⁵⁺ compound and the Sb ³⁺ compound in an aqueous medium at 90 ° C. or more for 3 hours or more, heating was performed once. Stopping and then adding the remaining Mo ⁶⁺ compound. Step (2): a step of adding a compound containing the following metal A to the aqueous liquid obtained in the above step (1). Step (3): a step of drying the dried liquid obtained by evaporating the aqueous liquid obtained in the above step (2) to dryness, and further baking it. Composition formula; in _{MoV i Sb j A k O y} ( wherein, A is, Nb, Ta, W, Ti , Zr, Re, F
e, Ni, Co, Sn, Tl, Cu, at least one selected from the group consisting of rare earth elements and alkali metal elements.
It is a seed element. i and j are each 0.01 to 1.5
And j / i = 0.3 to 1.0, and k is 0.00
1 to 3.0, and y is a number determined by the oxidation state of another element. Hereinafter, the present invention will be described in more detail. DETAILED DESCRIPTION OF THE INVENTION In step (1) of the present invention, the following reaction occurs between Mo ⁶⁺ , V ⁵⁺ and Sb ³⁺ in an aqueous medium at 90 ° C. or higher. The main reaction is a reaction represented by the reaction formula (1). With the progress of the main reaction (1), water-insoluble Sb ³⁺ compounds such as antimony trioxide decrease,
The reaction system forms an overall homogeneous aqueous dispersion. ^{V 5+ + Sb 3+ ─ → V} 3+ + Sb 5+ (1) V 3+ + Mo 6+ ─ → V 4+ + Mo 5+ (2) V 5+ + V 3+ ─ → 2V 4+ (3) In step (1), the progress of the above-mentioned reaction is significantly different depending on the ratio of Mo ⁶⁺ present in the reaction system. That is, if the proportion of Mo ⁶⁺ present in the aqueous medium at 90 ° C. or higher is too low, the reaction (2) becomes relatively disadvantageous, whereas the reaction (3) becomes advantageous. As a result, V ⁵⁺ used as a raw material is wasted by the reaction (3) in addition to the main reaction (1). On the other hand, when the proportion of Mo ⁶⁺ is large, the reaction (1) and the reaction (2) are likely to occur in the step (1), and as a result, V ⁵⁺ wasted by the reaction (3) is reduced. The present inventors have conducted a detailed study on the reaction in step (1), and found that if the proportion of Mo ⁶⁺ present in the aqueous medium at 90 ° C. or higher is too large, the resulting aqueous dispersion It was found that the performance decreased. That is, when reacting Mo ⁶⁺ , V ⁵⁺ and Sb ³⁺ in an aqueous medium in a mixing ratio to obtain a metal oxide of the above composition formula that exhibits excellent performance as an acrylic acid production catalyst, from Mo ⁶⁺ compound of the total amount used for the reaction, was charged with V ⁵⁺ compound and Sb ³⁺ compound to the reactor, than the reaction is carried out in 90 ° C. or higher of the aqueous medium, of the Mo ⁶⁺ compound used for the reaction After charging only 5 to 80% by mass of the V ⁵⁺ compound and the Sb ³⁺ compound into a reactor and performing a reaction in an aqueous medium at 90 ° C. or higher,
When the heating of the reactor was stopped and the temperature of the reaction solution dropped to less than 90 ° C., it was found that adding the remaining Mo ⁶⁺ compound yielded an acrylic acid catalyst with superior performance. Was. In the present invention, the reaction time of the metal ion in an aqueous medium at 90 ° C. or higher requires at least 3 hours, and is usually preferably 5 to 20 hours. The reaction temperature is preferably in the range of 95 ° C. to the boiling point of the aqueous medium. The content of the reaction solution in the above reaction is preferably a ratio of 3 to 30 parts by mass of the total weight of the metal compound per 100 parts by mass of water. When the total weight of the metal compound exceeds 30 parts by mass, a part of the Mo ⁶⁺ compound or the V ⁵⁺ compound is insoluble in water, and the reaction tends to be incomplete. The above reaction is preferably performed with stirring, and it is preferable to continue stirring even after adding the Mo ⁶⁺ compound to the reaction solution having a liquid temperature of less than 90 ° C. The time for adding the Mo ⁶⁺ compound may be immediately after the heating of the reactor is stopped and the temperature of the reaction solution reaches less than 90 ° C. or after a while. Also, add Mo
^{The 6+} compound may be in the form of either a powder or an aqueous solution.
The preferred amount of the ^{Mo6 +} compound charged to the reactor for the reaction in an aqueous medium at 90 ° C. or higher is 10 to 50% of the total amount.
% By mass. The compounds used in the above reaction include the following. Sb ³⁺ The V ⁵⁺ compound as constituent elements V ^5+, metavanadate Anmon'niumu or vanadium pentoxide which preferably, as constituent elements Sb ³⁺
As the compound, antimony trioxide is preferable.
^Examples of the Mo ⁶⁺ compound containing o ⁶⁺ as a constituent element include ammonium molybdate, molybdenum oxide, molybdic acid, and the like, and ammonium molybdate is preferably water-soluble. After adding the Mo ⁶⁺ compound,
Stirring is continued for the time necessary for it to mix well with the other components in the aqueous medium, after which the reaction is cooled to about room temperature before proceeding to step (2). In the step (2), a compound containing metal A (hereinafter referred to as a component A compound) is added to the aqueous reaction solution obtained in the step (1). By this operation, a fine precipitate is formed in the reaction solution. Metal A is Nb, T
a, W, Ti, Zr, Re, Fe, Ni, Co, Sn,
At least one element selected from the group consisting of Tl, Cu, rare earth elements and alkali metal elements. It is preferable that the component A compound is added to the aqueous reaction solution obtained in the step (1) within as short a time as possible, and is immediately and uniformly mixed. The time required for adding the component A compound is preferably 3 minutes or less, more preferably 1 minute or less. The component A compound is preferably added in the form of an aqueous solution, and the aqueous reaction solution to which it is added is preferably stirred vigorously during the addition. As the component A compound, oxides, nitrates,
Carboxylates, oxoacid salts, oxalates and the like can be used. A
The component compound may be used in the form of being dispersed in water, but is more preferably used in the form of an aqueous solution using oxalic acid or the like. The amount of the component A compound used is such that A is 0.001 to 3.0 when Mo is 1 in the atomic ratio of the metal in the obtained metal oxide catalyst. M in the catalyst
If the ratio of A when o is 1 is less than 0.001, the catalyst will deteriorate, while if it exceeds 3.0, the catalyst will have low activity and the conversion of propane will be poor. When nitric acid or ammonium nitrate is added to the reaction solution obtained by adding the component A compound in the step (2), the physical strength of the finally obtained metal oxide catalyst is improved. A preferable addition amount of nitric acid or ammonium nitrate is 0.7 to 2.1 in a molar ratio to Sb, and more preferably 0.5 to 2.1.
〜1.7. After the above step (2) is completed, the obtained aqueous liquid is evaporated to dryness, and the obtained solid is dried and calcined. Evaporation to dryness and drying can be performed by a conventionally known method. It is efficient to blow an inert gas such as nitrogen or air during evaporation to dryness. The temperature of evaporation to dryness is preferably in the range of 50 to 130 ° C. The dried solid obtained by the above operation is first heated to 280 in the presence of oxygen.
After firing at 320 ° C for 2 to 20 hours, the temperature is further in the absence of oxygen at a temperature of 500 to 660 ° C, preferably 570 to 620 ° C.
For 1 to 3 hours to obtain a target metal oxide. The content of the metal element in the metal oxide obtained by the above-mentioned calcination can be confirmed by fluorescent X-ray analysis. The catalyst for producing acrylic acid obtained by the above method can be used as it is, but it is more preferable to pulverize it to an appropriate particle size to increase the surface area. As a pulverization method, any of a dry pulverization method and a wet pulverization method can be used, and examples of a pulverization device include a mortar, a ball mill and the like. In the case of wet grinding, examples of the type of the solvent used as a grinding aid include water and alcohols. The preferred particle size of the present catalyst is 20 μm or less, more preferably 5 μm or less. The catalyst for producing acrylic acid in the present invention can be used in the state of no carrier, but can also be used in the state of being supported on a carrier such as silica, alumina, silica-alumina and silicon carbide having an appropriate particle size. Next, a gas phase oxidation reaction method will be described. Propane and oxygen gas, which are the raw materials for producing acrylic acid, may be separately introduced into the reactor and mixed in the reactor, or may be introduced into the reactor in a state where both are mixed in advance. As oxygen gas, pure oxygen gas or air,
And gases obtained by diluting them with nitrogen, steam or carbon dioxide. When propane and air are used, the ratio of air to propane is preferably 30 times or less by volume, more preferably 0.2 to 2 times.
The range is 0 times. Propane, an unreacted raw material obtained from the outlet of the reactor, and propylene, an intermediate product, can be used as fuel as it is, but after being separated from other components in the product, it is introduced into the reactor. It can be reused. The preferred reaction temperature is from 300 to 600 ° C, more preferably from 350 to 500 ° C. The gas space velocity (hereinafter referred to as SV) is 300 to 50.
00 hr ^-1 is appropriate. It is presumed that the metal oxide obtained by the present invention exerts excellent effects even when applied to the synthesis of acrylic acid by oxidation of acrolein or propylene. Examples and Comparative Examples Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. The catalyst obtained in each example was prepared by adding 1.5 ml (about 2.2 g) of the catalyst to 10
The reaction tube was filled in a quartz reaction tube of mmφ. Reaction tube at 420 ° C
And 4.4% by volume of propane, 7.0% by volume of oxygen, 26.3% by volume of nitrogen and 62.3% by volume of steam
Was supplied at a rate of 2400 / hr to synthesize acrylic acid. Based on the reaction product, the following conversion and selectivity were calculated, and the performance of the catalyst used was evaluated based on those values. The results are shown in Table 1 below. The propane conversion and the acrylic acid selectivity were calculated based on the following formulas (all calculated by moles). -Propane conversion (%) = (supply propane-unreacted propane) / supply propane-Acrylic acid selectivity (%) = formed acrylic acid / (supply propane-unreacted propane)-Acrylic acid yield (%) = propane Conversion rate × Acrylic acid selectivity Example 1 In a 500 ml glass flask, 120 ml of distilled water, 5.87 g of antimony trioxide, 10.9 g of ammonium molybdate and 6.15 g of ammonium metavanadate were added. A large amount of nitrogen gas was circulated to sufficiently purge with nitrogen. Next, the solution was subjected to a heat treatment for 14 hours while refluxing the solution at the boiling point of water while rotating the stirrer at a speed of 350 revolutions / minute. 8 of the resulting blue colloidal dispersion
The mixture was allowed to cool to 0 ° C., 20.0 g of ammonium molybdate was added at a liquid temperature of 80 ° C., and the mixture was stirred for about 5 minutes to dissolve. While continuing to stir, the flask containing the reaction solution was cooled to 10 ° C. with ice water. 70 ml of 8.82 g of oxalic acid and 2.33 g of niobic acid were added to the slurry cooled to 10 ° C.
An aqueous solution at room temperature dissolved in distilled water was added. After the obtained mixture was vigorously stirred for 30 minutes, 5.0 g of ammonium nitrate was added and mixed uniformly. The reaction solution that had undergone the above operation was concentrated by heating, and further evaporated to dryness at 120 ° C. The obtained solid was calcined in air at 300 ° C. for 5 hours and then calcined in a nitrogen gas stream at 600 ° C. for 2 hours to obtain a target metal oxide catalyst. The resulting catalyst was tableted, crushed to 16 to 30 mesh, and used for the acrylic acid production reaction. The atomic ratio of this catalyst is Mo / V / Sb / Nb = 1.0 / 0.3 / 0.25
/0.10. The results of conducting an acrylic acid synthesis test using this catalyst are as shown in Table 1. Table 1
In the formula, AA represents acrylic acid, and PP represents propane. Example 2 Same as Example 1 except that the weight of ammonium molybdate initially charged was 5.15 g, and the weight of ammonium molybdate added after lowering the liquid temperature to 80 ° C. was 25.75 g. The operation was performed. The results obtained by conducting an acrylic acid synthesis test using the obtained catalyst are as shown in Table 1. Comparative Example 1 The same operation as in Example 1 was carried out except that 30.9 g of ammonium molybdate was initially charged into the reactor, and thereafter no ammonium molybdate was added. The results obtained by conducting an acrylic acid synthesis test using the obtained catalyst are as shown in Table 1. [Table 1] According to the method of the present invention, a catalyst which is applicable to the production of acrylic acid by a gas phase catalytic oxidation reaction of propane and can obtain acrylic acid in a high yield can be produced with good reproducibility. .

   ────────────────────────────────────────────────── ─── Continuation of front page    F term (reference) 4G069 AA02 AA08 BB06A BB06B                       BC01A BC19A BC22A BC26A                       BC26B BC31A BC38A BC50A                       BC51A BC54A BC54B BC55A                       BC55B BC56A BC59A BC59B                       BC60A BC64A BC66A BC67A                       BC68A CB17 DA05 EA01Y                       FA01 FB06 FB29 FB30 FB31                       FB37 FB57 FC08                 4H006 AA02 AC46 BA12 BA13 BA14                       BA30 BE30 BS10                 4H039 CA65 CC10 CC30

Claims (1)

1. A process for producing a catalyst for producing acrylic acid comprising a metal oxide represented by the following composition formula, comprising the following steps (1), (2) and (3): A method for producing a catalyst for producing acrylic acid, comprising employing a method. Step (1): Mo ⁶⁺ compound, V ⁵⁺ as metal-containing compound
The compound and the Sb ³⁺ compound were used, and after heating 5 to 80% by mass of the Mo ⁶⁺ compound, the V ⁵⁺ compound and the Sb ³⁺ compound in an aqueous medium at 90 ° C. or more for 3 hours or more, heating was performed once. Stopping and then adding the remaining Mo ⁶⁺ compound. Step (2): a step of adding a compound containing the following metal A to the aqueous liquid obtained in the above step (1). Step (3): a step of drying the dried liquid obtained by evaporating the aqueous liquid obtained in the above step (2) to dryness, and further baking it. Composition formula; in _{MoV i Sb j A k O y} ( wherein, A is, Nb, Ta, W, Ti , Zr, Re, F
e, Ni, Co, Sn, Tl, Cu, at least one selected from the group consisting of rare earth elements and alkali metal elements.
It is a seed element. i and j are each 0.01 to 1.5
And j / i = 0.3 to 1.0, and k is 0.00
1 to 3.0, and y is a number determined by the oxidation state of another element. )