JPH07315842A - Production of niobium-containing multiple metal oxide - Google Patents

Abstract

PURPOSE:To obtain a multiple metal oxide composed of niobium and other component(s), excellent in stability and catalytic performance etc., by removing the solvent from a feedstock solution containing niobium and other component(s) to deposit insolubles which are then fired. CONSTITUTION:A feedstock solution containing niobium and other components is prepared. For niobium feedstock, it is appropriate that an organic acid niobium salt (e.g. niobium oxalate) be used. The other component(s) is pref. at least one metal selected from Mo, V, Te, Sb, Bi, Ta, W, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, B, In, Ce, Si, P, Cu, alkali metals, and alkaline earth metals. This solution is then subjected to solvent removal process (e.g. spray drying process) until insolubles are deposited from this solution. The deposit is then fired to obtain the objective multiple metal oxide composed of niobium and the other component(s).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a composite metal oxide containing niobium. The composite metal oxide is a catalyst, particularly a hydrocarbon, a gas phase partial oxidation catalyst for oxygen-containing compounds,
In addition to being used for solid acid catalysts, ceramics,
It is also attracting attention as an electrode material.

[0002]

2. Description of the Related Art The following methods are mainly known as known methods for producing niobium-containing composite metal oxides. The first method is a method in which a compound of constituent metal elements of a composite metal oxide, mainly each metal oxide, is collected in a predetermined amount, pulverized and mixed, and then treated at a high temperature to produce a solid-phase reaction. Is.

The second method is to prepare a solution or slurry in which niobium and other constituent elements are mixed, and to adjust the pH of the solution or slurry in some cases to actively form a precipitate, and then to form a precipitate. It is a method of recovering a solid matter by an evaporation dryness method, a spray drying method and the like and baking the solid matter.

[0004]

However, in the first production method by the solid phase reaction, the treatment conditions are generally 60.
It is an extremely high temperature of 0 to 1000 ° C., and usually requires a long reaction time of 1 day to 1 week. Also,
The composite metal oxide produced by this method usually has a small specific surface area and is often unsuitable for use as a catalyst.

Further, in the second method, few niobium compounds have sufficient solubility in an aqueous solvent,
In addition, it is difficult to maintain the dissolved state due to the influence of compounds of other elements added, and in general, the niobium compound component precipitates in a relatively short time even if the solution does not become a homogeneous solution or becomes a homogeneous solution state. I often do it. So, conventionally,
Usually, a slurry containing an insoluble solid niobium compound component was subjected to subsequent drying and heating treatments. Such a catalyst of a composite metal oxide containing niobium often has insufficient activity or is not stable, and in order to improve this, it is possible to consider the stirring conditions of the slurry, but a sufficient effect is not obtained. Not obtained.

[0006]

Means for Solving the Problems As a result of detailed examination of the method for producing a metal oxide containing niobium, the present inventors have found that
A method comprising a step of removing a solvent in a state where a solid solution containing niobium as a main component is not contained in a raw material solution of a composite metal oxide containing niobium, that is, a solid component containing niobium as a main component is not precipitated. It has been found that by adopting the above, it is possible to obtain a stable composite metal oxide excellent in catalytic performance and arrived at the present invention. That is,
The gist of the present invention is a method for producing a composite metal oxide comprising niobium and other components, wherein a raw material solution containing niobium and other components is subjected to solvent removal before insoluble matter precipitates from the raw material solution. And a step of precipitating an insoluble matter from the raw material solution and calcining the precipitate.

The present invention will be described in detail below. As the other component elements other than niobium of the composite metal oxide containing niobium produced by the present invention, Mo, V, Te, Sb,
Bi, Ta, W, Ti, Al, Zr, Cr, Mn, F
e, Ru, Co, Rh, Ni, Pd, Pt, B, In,
One or more selected from the group consisting of Ce, Si, P, Cu, alkali metals and alkaline earth metals are generally used.

The solvent used in the method of the present invention is preferably an aqueous solvent in view of operability and safety in the solvent removal step. Specifically, water is most common, but there is no problem even if it contains water-soluble substances such as alcohols, organic acids, and inorganic acids. The niobium compound used as a raw material for the composite metal oxide is not particularly limited as long as it is soluble in the above-mentioned solvent, but it is an organic niobium compound, specifically, an organic acid, preferably oxalic acid, and / or tartaric acid. Niobium raw materials containing, for example, niobium oxalate, niobium tartrate, and / or ammonium salts thereof, that is, ammonium niobium oxalate, ammonium niobium tartrate, and the like are preferable because they have high solubility in an aqueous solvent and are easy to operate.

The raw material compounds of elements other than niobium of the composite metal oxide are not particularly limited as long as they are soluble in the above aqueous solvent. Specifically, Mo, Sb, Bi, Ta, Al, C
r, Mn, Fe, Ru, Co, Rh, Ni, Pd, P
t, Ce, Cu, alkali metal, alkaline earth metal nitrates, acetates, ammonium paramolybdate, ammonium metavanadate, vanadyl oxalate,
Telluric acid, antimony oxide dissolved in tartaric acid, molybdophosphoric acid, molybdovanadolinic acid, tungstophosphoric acid, molybdotungstophosphoric acid and the like are used.

As a method for preparing the raw material solution, an optimal method is appropriately selected depending on the concentration and composition of the raw material components. Usually, a method for preparing the solution by collectively containing the niobium compound and other raw materials is preferable. For example, a method of separately preparing a solution of a niobium compound and a solution of a raw material other than niobium and then mixing them can be adopted. In addition, as a means for subjecting the step of rapidly removing the solvent before the insoluble matter is precipitated from the raw material solution, a suitable amount of the raw material solution is prepared, and immediately thereafter, the prepared raw material solution is subjected to the solvent removal step by a liquid feed pump or the like. It is also desirable to provide a method for continuously performing the preparation of the raw material solution and the removal of the solvent of the raw material solution. The concentration of niobium in the raw material solution containing niobium prepared as described above is usually 0.005.
-25% by weight, preferably 0.01-10% by weight. The concentration of elements other than niobium is usually 0.1, though it varies depending on the composition of the target composite metal oxide.
-25% by weight.

Although the details of the content of the niobium-containing solution thus prepared are not clear, there are various polyoxoanions of the component elements contained, and regarding niobium,
For example, it is presumed that a complex in which an organic acid such as oxalic acid and tartaric acid, which coexist, is incorporated as a ligand, is stably present in an aqueous solution. However, depending on the coexisting elements, the interaction with organic acids such as oxalic acid and tartaric acid is stronger than that of niobium, so that the ligands of these organic acids migrate from niobium to other elements, resulting in the It is conceivable that the stability of niobium in the solution is lost and insoluble matter containing niobium as a main component is precipitated as a solid after a certain time has passed after the solution was prepared.

A raw material solution containing niobium and other components is subjected to a step of removing the solvent before the insoluble matter is deposited from the raw material solution, that is, the raw material solution in which the insoluble matter is not yet deposited is subjected to the step of removing the raw material. As a solvent removing method for precipitating an insoluble matter from a solution, a spray drying method or a freeze drying method is preferable. These methods are characterized in that the solvent can be quickly removed while maintaining a uniform state in the solution as much as possible even in many drying processes. Other drying methods are considered suitable as long as they have such characteristics. As a result, the solvent is removed while maintaining the morphology of the effective complex metal oxide precursor, for example, while maintaining the morphology of the polyoxoanion already formed in solution,
It is presumed that this contributes to the improvement of the catalytic activity of the finally obtained composite metal oxide.

Here, the spray drying method refers to a drying method including a step of spraying a solution to generate fine droplets, and can be carried out using a commercially available spray dryer. The spray drying conditions may be appropriately set depending on the specifications of the spray dryer, the amount of the object, etc., but the temperature at the center of the spray dryer is usually 80 to
The temperature is set to 400 ° C., preferably 120 to 280 ° C., and heated dry gas such as air, nitrogen, or argon is circulated. The dry gas should possess more than the amount of heat needed to evaporate the aqueous solvent, and a higher amount of gas is needed if the temperature of the dry gas is low. It is also possible to adjust the particle size of solid particles obtained by spray drying by adjusting the amount of liquid supplied and the number of revolutions of the disk. Usually, the average particle size is, for example, 100 microns or less, and particularly 20 to 80 microns. Etc.

In the freeze-drying method, after freezing the solution,
It refers to a method of removing the solvent by sublimation, and can be carried out using a commercially available freeze dryer. After cooling the raw material solution with dry ice solution, liquid nitrogen, etc., and immediately freezing,
The method of drying using a freeze dryer is common. The drying conditions may be set according to the specifications of each freeze dryer, and the drying is usually performed under reduced pressure of about 0.01 to 10 mmHg. The particle size distribution of the dried product is not particularly limited, and the performance of the catalyst is particularly affected even if about several% of water remains in the dried product which has reached a constant weight by freeze-drying. is not. It is also possible to use a spray freeze-drying method that is a combination of both the above spray-drying method and freeze-drying method.

The precipitate solid thus obtained is fired. The baking method can be arbitrarily set depending on the solid components, properties, and scale, but in general, the method is heat treatment on an evaporation dish or a heating furnace such as a rotary furnace or a fluidized baking furnace. Target. Moreover, you may combine these heat processing operation in multiple types. The firing conditions are usually 300 to 700 ° C., preferably 400 to 650 ° C.,
It is about 0.5 to 30 hours. The firing atmosphere is not particularly limited and may be vacuum, but an inert gas atmosphere of nitrogen, argon, helium or the like is preferable. Further, the inert gas may contain a reducing gas such as hydrogen or hydrocarbon, or steam.

Among the composite metal oxides containing niobium produced as described above, those containing molybdenum and vanadium as components other than niobium are particularly effective as a catalyst, and more preferably the following empirical formula (1) Is effective, and when used as a catalyst for producing a nitrile from an alkane, a remarkable effect is exhibited.

[0017]

[Number 2] In _{Mo a V b Nb c X x} O n (1) ( Formula (1), X is Te, Sb, Bi, Ta,
W, Ti, Al, Zr, Cr, Mn, Fe, Ru, C
represents one or more elements selected from o, Rh, Ni, Pd, Pt, B, In and Ce, and when a = 1, b = 0.01 to 1.0 c = 0 0.01 to 1.0 x = 0 to 1.0, and n represents a numerical value determined by the oxidation state of the element. ) Here, when X is Te or Te and another metal, the performance as a catalyst is particularly excellent. Further, when propane or isobutane is used as the alkane, the catalytic performance is remarkable. When propane and isobutane are used as raw materials, their products, acrylonitrile, and methacrylonitrile are industrially important.

In the case of using propane as the alkane and air as the oxygen source, the present invention will be described in more detail. The reactor system may be either a fixed bed or a fluidized bed, but since it is an exothermic reaction, It is easier to control the reaction temperature in the fluidized bed method. The ratio of air supplied to the reaction is important with respect to the selectivity of acrylonitrile produced, and the air usually has a high acrylonitrile selectivity in a range of 25 mol times or less, particularly 1 to 18 mol times, relative to propane. . The proportion of ammonia supplied to the reaction is 0.2 to 5 times the molar amount of propane, particularly 0.1.
A range of 5 to 3 molar times is suitable. The reaction is usually carried out under atmospheric pressure, but it can also be carried out under slightly elevated pressure or reduced pressure. For other alkanes, the composition of the feed gas is selected according to the conditions for propane. The reaction temperature is generally 340 to 480 ° C, preferably 380 to 440 ° C. Gas space velocity SV in the gas phase reaction is usually 100～10000H ^-1, preferably in the range of 300~2000h ^-1. An inert gas such as nitrogen, argon, or helium can be used as a diluent gas for adjusting the space velocity and the oxygen partial pressure. When the ammoxidation reaction of propane is carried out by the method of the present invention, carbon monoxide, carbon dioxide, acetonitrile, hydrocyanic acid and the like are by-produced in addition to acrylonitrile, but the production amount is small.

The above composite metal oxide catalysts may be used alone or in combination with well-known carriers such as silica, alumina, titania, zirconia, aluminosilicate, diatomaceous earth and the like. In this case, the carrier as described above may be added to the raw material solution containing niobium before the step of removing the solvent, or may be added and mixed after the solvent is removed, for example, before and after firing. Good.
When these carrier components are added, a solid solution derived from the carrier is already contained before being subjected to the step of removing the solvent, not as a homogeneous solution, but the solid is originally insoluble and precipitates after dissolving once. If the insoluble matter containing niobium as the main component is not precipitated in the solution, the method of the present invention can be applied to a raw material solution containing a carrier component. In this method, it may not always be possible to clearly determine the state of precipitation of the insoluble matter containing niobium as the main component, but in such a case, usually, within the time period in which the insoluble matter does not precipitate in the raw material solution excluding only the carrier component. The raw material solution may be subjected to the step of removing the solvent.

[0020]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded. The conversion rate (%), selectivity rate (%) and yield rate (%) in the following examples are shown by the following equations, respectively.

[0021]

## EQU00003 ## Propane conversion rate (%) = (mol number of consumed propane / mol number of propane fed) × 100 acrylonitrile yield (%) = (mol number of acrylonitrile produced / mol number of fed propane) × 100 Acrylonitrile selectivity (%) = (mol acrylonitrile produced / mol propane consumed) × 100

Example 1 A composite oxide having the empirical formula Mo ₁ V _0.3 Nb _0.12 Te _0.23 O _n was prepared as follows. 10.59 g of ammonium paramolybdate tetrahydrate was dissolved in 95 ml of warm water, and 2.11 g of ammonium metavanadate and 3.17 g of telluric acid were sequentially added thereto to prepare a uniform aqueous solution at room temperature. The concentration of niobium in this solution is 0.396 mol / kg
18.2 g of an aqueous solution of ammonium niobium oxalate was mixed. While this solution was visually in a uniform solution state, water was removed by a spray drying method to obtain a precipitated solid. This solid was molded into a size of 5 mmφ × 3 mmL using a tablet molding machine, pulverized, sieved to 16 to 28 mesh, and baked in a nitrogen stream at 600 ° C. for 2 hours.

Comparative Example 1 A solution containing molybdenum, vanadium, tellurium and niobium was prepared in the same manner as described in Example 1, but it was observed that a solid was deposited in about 10 minutes. Water was removed from the slurry thus obtained by precipitating solids by the spray drying method in the same manner as in Example 1 to obtain solids. Molding, crushing and firing were performed in the same manner as in Example 1.

Example 2 A composite oxide having the empirical formula Mo ₁ V _0.3 Nb _0.12 Te _0.23 O _n was prepared as follows. 70.9 g of ammonium paramolybdate tetrahydrate was dissolved in 402 ml of warm water, and 14.1 g of ammonium metavanadate and 2
An aqueous solution was prepared by sequentially adding 1.2 g. The solution was cooled to about 5 ° C and the niobium concentration was 0.396mo.
122 g of 1 / kg ammonium niobium oxalate aqueous solution
Were mixed. While this solution was in a uniform solution state, water was removed by a spray drying method to obtain a solid precipitate. This solid was molded into a size of 5 mmφ × 3 mmL using a tablet molding machine, pulverized, sieved to 16 to 28 mesh, and baked in a nitrogen stream at 600 ° C. for 2 hours.

Example 3 A composite oxide having the empirical formula Mo ₁ V _0.3 Nb _0.1 Te _0.2 O _n was prepared as follows. 4.7 g of ammonium paramolybdate tetrahydrate was dissolved in 43 ml of warm water, and 0.94 g of ammonium metavanadate and 1.
2 g was sequentially added to prepare a uniform aqueous solution. Further, 9.2 g of an aqueous solution of ammonium niobium oxalate having a niobium concentration of 0.29 mol / kg was mixed. While this solution was in a uniform solution state, water was removed by freeze-drying to obtain a solid precipitate. This solid was molded into a size of 5 mmφ × 3 mmL using a tablet molding machine, and then pulverized to 16 to 28
The mixture was sieved into a mesh and fired at 600 ° C. for 2 hours in a nitrogen stream.

Reaction Test Example 1 0.55 g of the composite metal oxide obtained in Example 1 was charged into a reactor, the reaction temperature was 400 ° C., the space velocity was SV1005h ^-1 ,
Table 1 shows the results of gas-phase catalytic reaction in which gas was supplied at a molar ratio of propane: ammonia: air = 1: 1.2: 15.
Shown in.

Reaction Test Example 2 Using the composite metal oxide obtained in Comparative Example 1, a gas phase catalytic oxidation reaction of propane and ammonia was carried out under the same reaction conditions as in Example 1. The results are shown in Table-1.

Reaction Test Example 3 0.38 g of the composite metal oxide obtained in Example 2 was charged into a reactor, the reaction temperature was 410 ° C., the space velocity was SV 1000 h ^-1 ,
Table 1 shows the results of gas-phase catalytic reaction in which gas was supplied at a molar ratio of propane: ammonia: air = 1: 1.2: 15.
Shown in 1.

Reaction Test Example 4 A reactor was charged with 0.55 g of the catalyst obtained in Example 3, the reaction temperature was 400 ° C., the space velocity was SV923 h ⁻¹ , and the molar ratio of propane: ammonia: air = 1: 1.2: 15. Table 1 shows the results of the gas-phase catalytic reaction performed by supplying the gas at a ratio.

[0030]

[Table 1]

[0031]

According to the present invention, a composite metal oxide containing niobium having stable properties can be produced by a relatively simple method. Such a composite metal oxide has excellent performance as a catalyst, and is particularly suitable as a catalyst for nitrile production by a gas phase catalytic oxidation reaction of an alkane and ammonia.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location C01G 41/00 A // C07B 61/00 300 C07C 253/24 255/08

Claims (8)

[Claims] 1. A method for producing a composite metal oxide comprising niobium and other components, wherein a raw material solution containing niobium and other components is subjected to solvent removal before insoluble matter is precipitated from the raw material solution. A method for producing a composite metal oxide containing niobium, which comprises subjecting the material to a step, depositing an insoluble matter from the raw material solution, and firing the deposit. 2. A method for producing a composite metal oxide comprising niobium and other components, wherein a raw material solution containing niobium and other components in which insoluble matter is not deposited is spray-dried or freeze-dried. A method for producing a composite metal oxide containing niobium, which comprises: providing a solvent to remove an insoluble matter from the raw material solution; and calcining the deposited matter. 3. The other components are Mo, V, Te, Sb,
Bi, Ta, W, Ti, Al, Zr, Cr, Mn, F
e, Ru, Co, Rh, Ni, Pd, Pt, B, In,
The method according to claim 1 or 2, wherein the method is one or more selected from the group consisting of Ce, Si, P, Cu, alkali metals and alkaline earth metals. 4. The method according to claim 1, wherein niobium organic acid is used as a niobium raw material. 5. The method according to any one of claims 1 to 4, wherein the raw material solution contains a carrier component. 6. The method according to claim 1, wherein the composite metal oxide is represented by the following empirical formula (1). [Number 1] in _{Mo a V b Nb c X x} O n (1) ( Formula (1), X is Te, Sb, Bi, Ta,
W, Ti, Al, Zr, Cr, Mn, Fe, Ru, C
represents one or more elements selected from o, Rh, Ni, Pd, Pt, B, In and Ce, and when a = 1, b = 0.01 to 1.0 c = 0 0.01 to 1.0 x = 0 to 1.0, and n represents a numerical value determined by the oxidation state of the element. ) 7. The method according to claim 1, wherein the raw material solution contains a carrier component. 8. A catalyst for nitrile production by vapor phase catalytic oxidation reaction of an alkane and ammonia, comprising a composite metal oxide produced by the method according to any one of claims 1 to 7.