JPS6147574B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing a catalyst composition.

More specifically, the present invention relates to a method for producing an oxidation reaction catalyst composition containing a mixed oxide of vanadium and phosphorus as a main component.

BACKGROUND ART Catalysts mainly composed of mixed oxides of vanadium and phosphorus have been known to exhibit high activity in oxidation reactions, particularly in reactions that selectively oxidize butane to produce maleic anhydride. A catalyst mainly composed of a mixed oxide of vanadium and phosphorus is produced by, for example, combining a vanadium compound such as vanadium pentoxide with a phosphorus compound such as phosphorus pentoxide or phosphoric acid in a reducing aqueous medium such as hydrochloric acid or oxalic acid. It is produced by heating and mixing until the valence is lower than pentavalent, then by precipitation or evaporation to dryness to obtain a catalyst precursor consisting of a solid phosphorus-vanadium compound, which is then calcined.

As a result of research on a catalyst composition for oxidation reactions mainly composed of a mixed oxide of vanadium and phosphorus, the present inventors discovered that the solid phosphorus-vanadium compound was calcined and the calcined product obtained was washed to make a water-soluble The present inventors have discovered that a catalyst produced mainly from the remaining water-insoluble portion after removal of that portion exhibits high activity in oxidation reactions, particularly in the above reaction for producing maleic anhydride, even at relatively low temperatures. .

That is, an object of the present invention is to produce a catalyst composition that exhibits high activity in oxidation reactions even at relatively low temperatures. A mixing step in which the valence of vanadium is mixed under conditions of 4.0 to 4.3; (b) an aqueous medium separation step in which the aqueous medium is separated and removed from the mixture obtained in the mixing step to obtain a solid phosphorus-vanadium compound; c) a firing step in which the solid phosphorus-vanadium compound is fired at 350°C or higher, and (d) a washing step in which the fired product obtained in the firing step is washed with water to remove the water-soluble portion and obtain the water-insoluble portion. The present invention relates to a method for producing a catalyst composition for producing maleic anhydride by oxidizing n-butane, the method comprising the steps of:

Next, the present invention will be explained in detail.

In the method of the present invention, in the mixing step, a phosphorus compound and a vanadium compound are mixed in an aqueous medium under conditions such that the valence of vanadium is 4.0 to 4.3.

If the valence of vanadium in the mixture is outside the above range, the selectivity of the resulting catalyst composition to maleic anhydride will decrease. To make the valence of vanadium within the above range, a tetravalent vanadium compound should be used, or a pentavalent vanadium compound should be mixed with a reducing substance such as hydrochloric acid, oxalic acid, hydrazine, hydroxyamine, formaldehyde, or acetaldehyde. Bye.

Suitable examples of the tetravalent vanadium compound include vanadyl dichloride (VOCl ₂ ), vanadyl dibromide (VOBr ₂ ), vanadyl acetate, etc., and examples of the pentavalent vanadium compound include ammonium vanadate, vanadium pentoxide, etc. used.

On the other hand, as the phosphorus compound, phosphoric acids such as metaphosphoric acid, orthophosphoric acid, and pyrophosphoric acid, phosphorus oxides such as phosphorus pentoxide, phosphorus halides such as phosphorus pentachloride, and the like are used.

In addition, vanadium compounds and phosphorus compounds are P/
It is preferable to mix so that the atomic ratio of V is in the range of 1.0 to 1.2. By setting the P/V atomic ratio within the above range, a particularly highly active catalyst can be obtained. The vanadium compound and the phosphorus compound are mixed in an aqueous medium, usually at 50 to 150°C, preferably
It is carried out at 70-100°C. The concentration of the vanadium compound and the phosphorus compound in the mixed liquid is suitably in the range of 5 to 50% by weight in total.

In the method of the present invention, next, the aqueous medium is separated and removed from the liquid mixture obtained in the mixing step to obtain a solid phosphorus-vanadium compound.

The aqueous medium can be separated and removed from the mixed solution by, for example, heating the mixed solution to 80 to 150° C. and evaporating it to dryness. The solid phosphorus-vanadium compound contains about 10% by weight of water of crystallization. In the evaporation to dryness operation, it is sufficient to remove water until the water content in the solid, excluding water of crystallization, is about 1 to 10% by weight.

Moreover, in order to obtain a catalyst with higher activity in the method of the present invention, it is particularly preferable that the phosphorus-vanadium compound obtained in the aqueous medium separation step has an X-ray diffraction pattern shown in Table 1 below.

Table 1 ゜2θ (CuKα) strength 15.4 VS 18.3 W 19.5 S 21.7 W 24.1 S 27.0 S 28.7 M 30.3 VS 32.0 M 33.6 M 34.3 M (W=weak, VS=very weak, S=strong, M=medium) ) The phosphorus-vanadium compound having the X-ray diffraction pattern shown in Table 1 above can be obtained by, for example, adding water to a solid obtained by evaporation to dryness in an aqueous medium separation step to create a liquid mixture containing this solid; Next, the mixed solution is evaporated to dryness to obtain a solid again, which is then obtained by repeating the operations of adding water and evaporating to dryness. The solid obtained in the first evaporation to dryness is brown in color, but as the water addition and evaporation to dryness are repeated, a bright blue solid containing a phosphorus-vanadium compound having the above-mentioned X-ray diffraction pattern is obtained. . In the evaporation to dryness operation, the amount of water added to the solid is suitably 0.2 to 5 times the weight of the dry solid.
If the temperature of evaporation to dryness is too high, a phosphorus-vanadium compound having the above-mentioned X-ray diffraction pattern cannot be obtained, so the temperature is usually 80 to 350°C, preferably 100 to 150°C. The evaporation to dryness operation is performed until the proportion of the phosphorus-vanadium compound having the X-ray diffraction pattern in the solid is at least 25% by weight or more, preferably 50% by weight in terms of vanadium amount.
It is repeated until the above is reached. The operations of adding water and evaporating to dryness are usually performed two or more times, preferably three to five times.

The proportion of the vanadium-phosphorus compound in the solid in terms of vanadium amount is 0.1 to 20 to 30 times the weight of the solid to the solid obtained after evaporation to dryness.
Add a 0.2 mol/concentration phosphoric acid aqueous solution and heat this to 80 to 100°C while stirring to dissolve only the solids other than the phosphorus-vanadium compound having the X-ray diffraction pattern, and then filter the resulting aqueous solution. ,
It can be determined by measuring the amount of vanadium in the liquid and the amount of vanadium in the excess residue.

Phosphorus having the above X-ray diffraction pattern in a solid
Vanadium compound content (converted to vanadium amount) (wt%) = amount of vanadium in the solution / amount of vanadium in the solution + amount of vanadium in the solution Also, another method to obtain a phosphorus-vanadium compound having the above-mentioned X-ray diffraction pattern As a seed crystal, a phosphorus-vanadium compound having the above-mentioned X-ray diffraction pattern or a solid containing the same prepared in advance is added to an aqueous medium containing the above-mentioned phosphorus compound and vanadium compound, and then this is added to an aqueous medium containing the phosphorus compound and vanadium compound as a seed crystal. Another method is to mix at 100°C and evaporate the mixture to dryness in a similar manner. At this time, the amount of the vanadium-phosphorus compound to be added is calculated in terms of vanadium amount with respect to the phosphorus and vanadium compound contained in the mixed liquid.
0.02 to 0.25 times the weight is appropriate. According to this method, a phosphorus-vanadium compound having the above-mentioned X-ray diffraction pattern can be obtained without repeating the evaporation to dryness operation. In order to obtain a highly purified phosphorus-vanadium compound having the above-mentioned X-ray diffraction pattern, the solid obtained by the above method may be sufficiently washed with water.

In the method of the present invention, the solid phosphorus-vanadium compound obtained in the aqueous medium separation step is calcined at 350°C or higher.

In the firing step in the method of the present invention, the firing temperature is
If it is lower than 350°C, a highly active catalyst cannot be obtained, and conversely, if it is too high, the maleic anhydride selectivity of the catalyst decreases. Therefore, the firing temperature is 350°C or higher, preferably 450-600°C, more preferably 500-600°C.
The temperature is 550℃.

An inert gas or an oxygen-containing gas is selected as the calcination atmosphere, but if the calcination is performed only under an inert gas atmosphere, a sufficiently highly active catalyst cannot be obtained; and the catalyst yield decreases slightly. Optimally, the firing is performed under an inert gas atmosphere and then under an oxygen-containing gas atmosphere. The appropriate firing time is 1 to 10 hours.

Note that nitrogen is preferably used as the inert gas, and air is preferably used as the oxygen-containing gas.

In the washing step in the method of the present invention, the fired product obtained in the above firing step is washed with water to remove the water-soluble portion and obtain the water-insoluble portion.

To wash the fired product, add water to the fired product and rinse at 60 to 100 ml.
Heat to ℃ and stir, then filtrate, centrifuge,
Alternatively, this can be carried out by removing the water-soluble portion by an operation such as decanting. The amount of water used for washing is 2 to 10 times the weight of the baked product, and the stirring time is 10 minutes to 1 hour. The number of times of water washing is normally determined as appropriate within the range of 1 to 5 times.

The aqueous solution containing the water-soluble portion discharged by water washing usually has a brown to greenish-brown color. The water-soluble portion is a compound of vanadium, phosphorus, and oxygen with an average valence of 4 to 5, and the amount of the water-soluble portion removed by water washing is determined by the mixing conditions of the phosphorus compound and vanadium compound, the baking conditions, and the water washing. Although it varies depending on the conditions etc., the weight of the fired product is usually
20-80% by weight.

The water-insoluble part obtained usually has a gray color;
It is a compound consisting of vanadium, phosphorus, and oxygen, which have a valence of approximately 4, and elemental analysis shows that
V ₂ O ₄・P ₂ O ₅ (vanadium: 33.3% by weight, phosphorus:
20.2% by weight).

After drying, the water-insoluble portion is shaped and used as a catalyst. The surface area of the catalyst consisting of the dried water-insoluble part is in the range 40-50 m ² /g according to the low temperature nitrogen adsorption method (BET method).

Further, when using the water-insoluble portion of the fired product as a catalyst, it may be fired again after drying. By calcining the water-insoluble portion, the activity of the resulting catalyst can be stabilized. The firing temperature is 400-600℃, preferably 450-550℃,
A suitable firing time is 1 to 10 hours. The calcination is carried out in an inert or oxidizing atmosphere, for example, under the flow of nitrogen gas, air, or air containing 1 to 5% by volume of n-butane.

Note that if the conditions for cleaning the fired product in the cleaning step are too harsh, the activity of the resulting catalyst may be reduced. In such a case, add and mix the above-mentioned phosphorus compound and vanadium compound in an aqueous medium to the fired product,
The aqueous medium may be removed again and the catalyst may be dried. The mixing ratio of the phosphorus compound and the vanadium compound is preferably such that the P/V atomic ratio is within the range of 1 to 1.5. The valence of vanadium in the vanadium compound to be added does not necessarily have to be tetravalent, and the average valence may be in the range of 4 to 5.

The mixture obtained by adding a phosphorus compound and a vanadium compound to the calcined product may be used as a catalyst after removing the aqueous medium and drying the mixture, followed by calcining according to the method described above.

Before or after calcination, the catalyst is formed into any shape and size, such as pellets, tablets, or granules, depending on the conditions of use.

Further, the catalyst can be used alone or supported on a carrier. Silica, alumina, titania, carborundum, etc. are used as the carrier. The amount of catalyst supported on these carriers is usually appropriately selected from the range of 5 to 70% by weight.

The catalyst can be used in either a fluidized bed or a fixed bed.

Next, to explain the reaction in which the catalyst composition of the present invention is used, maleic anhydride is n
- Produced by contacting butane and oxygen in the gas phase in the presence of the catalyst according to the invention.

The raw material gas n-butane does not necessarily have to be of high purity, for example, i-butane or n-butane.
- May contain hydrocarbons such as butene.

When n-butane is diluted with another gas, the concentration of n-butane is preferably 50% or more.

As the oxygen, pure oxygen gas may be used, but it may also be diluted with a reaction inert gas such as nitrogen. Air is used industrially as the oxygen-containing gas.

The molar ratio of oxygen to n-butane is usually in the range of 2 to 200 times, preferably in the range of 4 to 40 times. Also, n in the total feed gas
- The concentration of butane is between 0.5 and 10% by volume, preferably between 1 and 5% by volume.

When using the catalyst in a fixed bed system, the space velocity of the raw material gas is 500 to 20000 hr ^-1 , preferably 1000 hr -1
Appropriately selected from the range of ~10000hr ^-1 .

The temperature of the catalyst layer is 300 to 600°C, preferably
The temperature is 350-500℃.

After the raw material gas is introduced into the catalyst layer and the reaction is carried out, the resulting reaction product gas is cooled and maleic anhydride is directly condensed, or the reaction product gas is passed through a solvent such as water. Maleic anhydride can be obtained by absorbing maleic anhydride into a solvent and then removing the solvent by an operation such as distillation.

When the catalyst composition of the present invention is used in the maleic anhydride production reaction, even at a relatively low reaction temperature, n
Since the -butane conversion rate can be increased and the maleic anhydride selectivity is also high, maleic anhydride can be produced industrially advantageously.

Next, the present invention will be explained in detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 and Comparative Example 1 24.9 g of 85% by weight orthophosphoric acid, 100 ml of water and 3.13 g of 80% by weight hydrazine hydrate were mixed, this mixed solution was heated to about 80°C, and then 18.2 g of vanadium pentoxide was added to it. g was gradually added and stirred to obtain a mixed solution containing vanadium and phosphorus having a valence of 4.0. The resulting solution was concentrated in an evaporating dish to obtain a dark blue viscous liquid. Approximately 150 in the end
After drying at a temperature of 0.degree. C., a blackish brown solid was obtained. After cooling, 50 ml of water was added to this solid and it was dried again, resulting in a dark brown solid containing some blue solids. Thereafter, the operations of adding water and evaporating to dryness were repeated four times in the same manner, and the entire mixture became a blue solid.
When this blue solid was subjected to X-ray analysis, the same X-ray diffraction pattern as shown in Table 1 was obtained. This blue solid was calcined at 550°C in a nitrogen stream for 4 hours, and then in air at 500°C for 2 hours. After firing, the atomic ratio of phosphorus to vanadium in the solid was 1.08.

Take a part of this baked product, mold it, and then crush it for 8~
Fill a stainless steel reaction tube with a tube diameter of 25 mm with 10 ml of granules of 14 mesh, and add n-butane to it with air.
A mixed gas diluted to % solubility was supplied at a rate of 10/hour. The highest yield of maleic anhydride was determined by varying the reaction temperature (the highest temperature at the center of the reaction tube was defined as the reaction temperature), and the highest yield of maleic anhydride was found to be 53 mol%, n- The conversion rate of butane was 95% and the reaction temperature was 430°C. (Comparative Example 1) 20 g of the above-mentioned baked product was taken, 100 ml of water was added thereto, and the mixture was stirred at a temperature of about 80° C. for 10 minutes and allowed to stand still. The supernatant was decanted and the insoluble solids were added with 100% water.
ml was added, stirred for 10 minutes at a temperature of about 80°C, and filtered. The resulting insoluble solid was washed with 100 ml of water and diluted with 150 ml of water.
After drying at 0.degree. C., it was calcined in air at 400.degree. C. for 1 hour to obtain 17.2 g of a gray solid. As a result of the analysis, P/
V is 1.00 and the average valence of vanadium is 4.05 BET
The surface area was 46 m ² /g. This gray solid was molded and pulverized to form granules of 8 to 14 meshes. Using 10 ml of this granular material, n-
When performing the oxidation reaction of butane, the highest yield of maleic anhydride was 62%, and the conversion rate of n-butane was 95%.
%, and the reaction temperature at that time was 380°C.

Comparative Example 2 Same X as in Table 1 obtained in Example 1
100 ml of water was added to 20 g of a blue solid showing a line diffraction pattern, stirred at a temperature of about 80° C. for 10 minutes, and allowed to stand still.
The supernatant liquid was removed by decantation, and 100 ml of water was further added to the resulting insoluble solid, stirred at a temperature of about 80° C. for 10 minutes, and filtered. The resulting insoluble solid was dissolved in 100% water.
After washing with ml and drying at 150℃, in air, 400℃
After calcination for 1 hour, a gray solid was obtained. This gray solid was molded and pulverized to form granules of 8 to 14 meshes. When oxidation reaction of n-butane was carried out using 10 ml of this granular material under the same reaction conditions as in Example 1, the maximum yield of maleic anhydride was 58%, the conversion rate of n-butane was 95%, and the conversion rate of n-butane was 95%. The reaction temperature is 400℃
It was hot.

Example 2 68.5 g of 85% by weight orthophosphoric acid and 1 mole/
146 ml of hydrazine solution were mixed, heated to about 50° C., and 50 g of vanadium pentoxide was gradually added.
The aqueous solution was reacted under reflux using a reflux condenser for 2 hours to obtain a mixed solution containing vanadium and phosphorus with a valence of 4.0. Thereafter, this was transferred to an evaporating dish, and the operations of adding water and evaporating to dryness were repeated three times in the same manner as in Example 1 to obtain a blue solid. When this blue solid was subjected to X-ray analysis, the same X-ray diffraction pattern as shown in Table 1 was obtained. This blue solid is placed in a nitrogen stream.
Calcinate at 550℃ for 2 hours, followed by 1.5 hours at 500℃ in air.
Baked for an hour. Take 20g of this fired sample and add water
100 ml was added and stirred at 80°C for 10 minutes. The liquid had a brown edge. Further, 100 ml of water was added to the insoluble solid, filtered, dried at 150°C, and then calcined in air at 400°C for 1 hour to obtain 16 g of a gray solid. This gray solid was molded and pulverized to form granules of 8 to 14 meshes. When oxidation reaction of n-butane was carried out using 10 ml of this granular material under the same reaction conditions as in Example 1, the maximum yield of maleic anhydride was 67%, the conversion rate of n-butane was 95%, and the conversion rate of n-butane was 95%. The reaction temperature at that time was 370°C.

Examples 3 and 4 A blue solid was obtained in the same manner as in Example 1 from 49.8 g of 85% by weight orthophosphoric acid, 200 ml of water, 6.26 g of 80% by weight hydrazine hydrate, and 36.4 g of vanadium pentoxide. The mixture was fired at 550°C for 2 hours in a medium atmosphere, and then fired at 550°C for 1 hour in air. Take 25g of the solid after firing and add 100ml of water to make about 80 g.
The mixture was stirred for 10 minutes at a temperature of °C and allowed to stand. Decant and remove the greenish brown supernatant liquid, add 100ml of water and add about 80ml of water.
The mixture was stirred for 10 minutes at a temperature of .degree. After washing the obtained insoluble solid with 100 ml of water and drying at 150 °C,
Calcined in air at 400°C for 1 hour to obtain 17.5g of gray solid. Take a part of this solid, mold it and crush it.
It was made into a granular material of 14 mesh. When oxidation reaction of n-butane was carried out using 10 ml of this granular material under the same reaction conditions as in Example 1, the maximum yield of maleic anhydride was 53% and the conversion rate of n-butane was 89%. The reaction temperature was 340°C. Separately, on the other hand, 85% by weight orthophosphoric acid was added to vanadium pentoxide so that P/V = 1.08, and after mixing in an aqueous medium, the mixture was evaporated to dryness, and Baked in air at 500℃ for 1 hour,
A vanadium-phosphorus composite oxide, which is mainly pentavalent vanadium, was prepared. Next, 18 g of the insoluble solid was taken, 2 g of the vanadium-phosphorus composite oxide and 50 ml of water were added thereto, mixed, and then evaporated to dryness. This dried product was calcined at 550℃ for 1 hour in a nitrogen stream, molded, and crushed to give an 8-14
It was made into granules of mesh. Take 10 ml of this granular material and use it under the same reaction conditions as in Example 1.
- When the oxidation reaction of butane was carried out, the maximum yield of maleic anhydride was 66%, and the conversion rate of n-butane was
95%, the reaction temperature at this time was 380°C.

Claims (1)

[Claims] 1 (a) Mixing step of mixing a phosphorus compound and a vanadium compound in an aqueous medium under conditions such that the valence of vanadium is 4.0 to 4.3; (b) Separating the aqueous medium from the mixed liquid obtained in the mixing step. (c) an aqueous medium separation step to remove and obtain a solid phosphorus-vanadium compound;
A firing process in which the solid phosphorus-vanadium compound is fired at 350°C or higher, and (d) a cleaning process in which the fired product obtained in the firing process is washed with water to remove the water-soluble part and obtain the water-insoluble part. A method for producing a catalyst composition for producing maleic anhydride by oxidizing n-butane, the method comprising: