JPS5992024A - Preparation of oxidation catalyst - Google Patents

Abstract

PURPOSE:To enhance the flowability, the strength and the activity of an oxidation catalyst, by spray drying a slurry mixture consisting of a first component comprising specific crystalline composite oxide, a second component comprising an aqueous solution containing V and P and a third component comprising a silica sol. CONSTITUTION:A first component comprising crystalline composite oxide containing P, tetravalent V and pentavalent V but containing pentavalent V in an amount of 35% or less on the basis of total V and showing X-ray diffraction peak (to a cathode Cu-Kalpha) at 2theta(+0.2 deg.), 14.2 deg., 15 deg., 7 deg., 18.5 deg. and 23.0 deg., a second component comprising an aqueous solution containing V and P and a third component comprising a silica sol are mixed to prepare a slurry. This slurry is spray dried to obtain a catalyst composition excellent in flowability and strength. Subsequently, the catalyst composition is baked at 400-600 deg.C to further enhance catalytic activity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an oxidation catalyst, and particularly to a method for producing an oxidation catalyst suitable for producing maleic anhydride from butane.

A composite oxide containing vanadium and phosphorus as essential components is effective in a method for producing maleic anhydride by vapor phase oxidation of hydrocarbons having several grams of carbon, especially n-butane, n-butene, butadiene, etc. It has been known. (U.S. Patent No. 3
, 193. Among these catalysts, it has been reported that crystalline vanadyl 191ate ((VssP,ot) is effective as an active ingredient [E. Bordes, Beakertin, Journal e of φ Catalysis (Ei, BOrd88.P, 0ourtine,
J, 0ata1. ) j'7. ．． 2JA(/97
? )). This compound can be identified by its crystal phase exhibiting an X-ray diffraction pattern as shown in the table below.

Table 7 (VO)* X#i1 diffraction of Pg Ot (Anticathode Ou-
α) Main hair beak -〇〇(10, -〇) Strength ratio/g, +2+20 /, lt, Rico 0
/g, & co.

+23. θ　　　　　　　/θθ Kog, 4t? .

30.0 30 33.7 Hiro θ J AJ & 0 According to the findings of the present inventors, the crystalline phase of this compound can be formed on a gas-phase oxidation catalyst of n-furin and n-puden based on the conventional manufacturing method. It has considerably higher activity than amorphous composite oxide catalysts, and has the characteristic that the reaction proceeds even at a low temperature of 100'C8 degrees, especially for the oxidation of furin. Therefore, X, Ii! It is preferable to use a catalytically active species having a diffraction peak in view of the process.

On the other hand, the reaction to produce maleic anhydride by gas phase oxidation from hydrocarbons with as many carbon atoms is a strongly exothermic reaction including complete oxidation (i.e., production of carbon oxide and carbon dioxide) as a side reaction, and is energy efficient. Fluidized bed catalytic oxidation reactions have traditionally been considered suitable because of the low explosive limit concentration of feedstock hydrocarbons relative to air.Catalysts developed for this purpose include, for example, oxalic acid. There is a catalyst prepared by spraying and drying a mixture containing vanadyl solution, phosphoric acid, silica sol, and appropriate activity-promoting components (British Patent No. 1.λg!?, 07A; etc.).

Although the catalyst thus obtained is effective for opening butene, butadiene, etc., its activity is not sufficient for oxidizing butane, and the reaction temperature is usually at least SOO°C.

There have also been some reports on fluidized bed catalysts for the oxidation of butane. For example, Tokukai Showaday/, 2A5g7
The issue describes an example in which a pentavalent vanadium compound was brought into contact with a trivalent phosphorus compound to form a composite oxide, which was then ground into a fine powder and applied to a fluid reaction. Although this method makes it possible to extract a crystalline active component and improve the activity, it is not sufficient in terms of hardness and fluidity of the catalyst.

Regarding the crushed fluidized bed reaction using such fine powder of catalytically active components, see Japanese Patent Application Laid-Open No. 1986-1 Near gg.

The possibility was also pointed out in JP-A Sho&A-#303g, etc., and JP-A Sho t&-65A,? No. J also points out the possibility of producing a fluidized bed catalyst by attaching a composite oxide to a carrier.

The inventors of the present invention have conducted extensive studies with the aim of developing a suitable υN source for gas-phase oxidation of n-butane in a fluidized bed.
By preparing a slurry by mixing a special crystalline oxide containing vanadium and phosphorus as the first component, an aqueous solution containing vanadium and phosphorus as the second component, and silica sol as the third component, and spraying and drying the slurry. It was discovered that a catalyst with excellent strength and fluidity could be produced, and a patent application was previously filed (see %H Showa 5 Ku 5 Ko 6 Da S and J7-Ri I9 Ko 0).

The crystalline oxide used as the tooth component in these applications exhibits an X-ray diffraction pattern similar to that in Table 1 above and is therefore essentially (VO)*PgO.
It is believed to be vanadyl pyrophosphate, which is represented by the chemical formula t. On the other hand, according to the above-mentioned B. Fordos et al., when vanadyl pyrophosphate represented by (Vsl p, o) is heated to a high temperature in an oxygen-containing atmosphere, vanadium changes from tetravalent to trivalent according to the following formula. When oxidized, it is said to change into a crystalline vanadium phosphate compound exhibiting the characteristic X-ray diffraction pattern shown in Table 1 below.

(VO) * Pa Oq +//λO1 Usakeke β-VOP
O4 coating--Xi diffraction peak (α to Osaka pole Ou-) Ko θ Peak strength/7.1 strong/q, 3 strong colo, :1 Strongest-g, i medium, 29. / 3 out of 30.0, 4 out of θ, 6 out of 6 out of g As a result of examining the performance relationship, the crystal structure of vanadyl pyrophosphate is maintained until the ratio of trivalent vanadium reaches 3S%, but as processing and oxidation proceed further, the crystal structure changes to 10=27. A broad peak appears at Da0 (α at the anticathode Cu-), which causes destruction and transition of the crystal structure, and the catalytic performance also decreases when the ratio of trivalent vanadium is 3.
It turned out that it was actually better than vanadyl pyrophosphate itself until it reached 3.

The present invention was completed based on this knowledge, and its gist is that it contains phosphorus and tetravalent and trivalent vanadium, and trivalent vanadium is less than the 35th factor of the total vanadium;
and a first component consisting of a crystalline composite oxide exhibiting the characteristic X-ray diffraction peaks shown in the table above, a second component consisting of an aqueous solution containing vanadium and phosphorus, and a third component consisting of silica sol are mixed. The present invention relates to a method for producing an oxidation catalyst, which is characterized in that the slurry is made into a slurry, and the slurry is dried by spray drying.

To explain the present invention in detail, in the present invention, a crystalline vanadium-phosphorus oxide exhibiting the X-ray diffraction peaks shown in Table 7 is used as the first component. A compound that gives such a diffraction spectrum is vanadyl pyrophosphate, which is represented by (VO)@ROq. This product is usually produced by producing a precursor compound and then firing it. As a precursor, for example, VOPO4JH
*O, (N&)t [(VO)10104 (HI
PO4)*)'jH*,o is known (E,
Furthermore, crystalline vanadium-phosphorus oxides having the characteristic X-ray diffraction spectra shown in Table 3 below are also effective as precursors.

Table-3 Xllil diffraction peak (α to anticathode Ou-) -〇〇(
±0.2°) Intensity ratio / 3.7 / 00 / de.

6! rθ−9,2gO core, /gS+2g,g
, 2 & 3θ, G
gO This precursor compound is well known and can be produced by the following methods.

(0) In a non-oxidizing N2 solution such as a hydrochloric acid solution, trivalent vanadium such as vanadium pentoxide is reduced with a reducing agent such as f; Preparation 1~, Method of reacting a solution with phosphoric acid and then precipitating the generated soluble vanadium-phosphorus complex by adding water (% open! r/-9!; No. 990), ■ Vanadium pentoxide A method in which trivalent vanadium compounds such as Kaisho 54-'I!;
g/jt), sieving or ■ Vanadium pentoxide is reduced in an organic medium such as ethanol, impropatol, or glycerol, reacted with phosphoric anhydride, and azeotropically dehydrated with a solvent such as benzene to precipitate crystals. There are known methods to do this (US Pat. No. 21!, No. 3.-gg).

In addition, the present inventors produced a precursor having the above-mentioned characteristic X-ray diffraction spectrum by a hydrothermal synthesis method in which an aqueous solution containing tetravalent vanadium ions and phosphoric acid was heated to a temperature of /10°C to 50°C. proposed a method to
(See Ko/No. 10).

The precursors obtained by these methods are (v*on)(P, O
, ) (xato).

Therefore, the ratio of phosphorus to vanadium is theoretically /, 0 in P/V atomic ratio, so when producing by any method, vanadium compounds and phosphorus compounds have P/V atomic ratio θ0.
It is preferable to react within the range of g~/, 2&.

Further, the first component used in the present invention may be partially substituted with various metal ions having a small difference in ionic radius from vanadium ions. Examples of such metal ions include ions of iron, chromium, aluminum, titanium, cobalt, magnesium, and the like. When such a composite oxide partially substituted with metal ions is used as a catalyst, it can bring about significant improvement in activity improvement and activity stabilization. The ratio of conversion to 1 is o, oos to o, q mol as metal per mol of vanadium element, more preferably O20
is selected in the range of -0, -mol. As a method for introducing such other metal ions into the composite oxide, these metal ions can be added to hydrochloride, sulfuric acid, nitrate, inorganic salts of carbonate, oxalic acid, etc. at the stage of manufacturing the composite oxide precursor. An example is a method of adding it in the form of an organic salt such as salt.

The X-ray diffraction pattern of the substituted solid solution type composite oxide thus obtained is slightly shifted from the peaks shown in Table 2, but -00 is within ±0.2°.

When this precursor is calcined in an inert gas atmosphere such as argon or nitrogen, a compound having the main X-ray diffraction peaks shown in Table 1 is obtained.

In this compound, vanadium is obtained in a substantially tetravalent state. The ratio of trivalent vanadium in the first component is correlated with the performance of the final catalyst, and generally the best results are obtained when the ratio of trivalent vanadium is /S~u,ll-%. , performance deteriorates when the ratio is larger or smaller than this range.

When the ratio of trivalent vanadium exceeds 3s%, the crystal phase of (VO)*PtOt begins to break down.

Such excessively oxidized calcined products sometimes have the disadvantage of forming gummy solids during catalyst production, and only catalysts with poor performance can be obtained. Therefore, firing in air must be carried out within a range in which the ratio of trivalent vanadium is 3j or less. What is the preferred ratio of trivalent vanadium in the first component? r~, 7! It is rq6.

Note that instead of firing in one step with an inert gas and air, the aforementioned precursor is fired in air diluted with an inert gas to give a predetermined X a1 diffraction peak as shown in Table 5. The first component may also contain trivalent vanadium at a ratio of . When the precursor is fired in normal air to form the first component, care must be taken to control the temperature so that the oxidation of vanadium does not proceed excessively.

The firing of the precursor can be carried out in any type of furnace, but typically a Matsufuru furnace, a rotary kiln, a fluidized bed firing furnace, etc. are used. Firing temperature It is the dehydration temperature of the precursor body.
0~7θ0' CC electric power, preferably yso~
The temperature is 1.00°C.

In addition, from the viewpoint of the strength of the final catalyst obtained, the first component has an average particle diameter of 7.
Below 0μ, especially! It is preferable that the particles be microscopic or smaller, and therefore it is preferable to crush them at the precursor stage or after calcination. According to the above-mentioned hydrothermal synthesis method, it is possible to generate a fine precursor, so when a slurry containing a fine precursor obtained by hydrothermal synthesis is spray-dried,
Fine precursors of the above-mentioned size can be obtained directly. When pulverizing, a known wet or dry pulverizer such as a hammer mill, jet mill, colloid mill, or sand grinder can be used. In the case of performing wet pulverization, either the second component or the third component ti may be mixed with the whole to form a slurry.

The aqueous solution containing vanadium and phosphorus as the second component in the present invention usually contains substantially tetravalent vanadium and trivalent phosphorus, at least a part of which is present as vanadyl phosphate. The second component has an effect as a binder between the composite oxide of the first component and the silica sol as a carrier of the third component, and serves as a fluid catalyst 1f11. Contributes to improved fluidity and strength. Although the method for producing such an aqueous solution is not particularly limited, some examples are shown below.

Generally, IA is produced by adding a reducing agent and vanadium pentoxide to an aqueous solution containing phosphoric acid and bath-dissolving the mixture. The atomic ratio of phosphorus element to vanadium element in the aqueous solution is preferably in the range of θ, S to /θ. Generally, vanadyl phosphate is unstable in aqueous solutions containing vanadyl phosphate, and it may be difficult to keep it stable for a long time, so oxalic acid can be added to stabilize the aqueous solution.

The amount is the molar ratio of oxalic acid to vanadium element λ1, which is less than Pano, preferably in the range of i+i2 of UO, - to /.

1) If the amount of acid is too large, it will have an unfavorable effect on the degree, height and activity of the catalyst.
/',give.

In other words, a range in which the molar ratio of oxalic acid to elemental vanadium is 8 or less can be said to be a range in which nazyl oxalate is not formed.

Specific examples of methods for producing aqueous bath liquid include the following methods.

Vanadium pentoxide is added to an aqueous solution containing the first K*i acid and ylene acid in a molar ratio of y6 acid to elemental vanadium of 7 or less, and preferably 0, q or more. (This is a method to prepare an aqueous solution containing Nazir and oxalic acid. Specifically, oxalic acid is dissolved in an acidic aqueous medium containing phosphoric acid, and vanadium pentoxide is slightly heated to a temperature at which the i element proceeds. According to this method, after the completion of Zhaoyuan, there will be less than hecomole of oxalic acid for elemental sodium.

In an acidic aqueous solution containing No. K, θ11 acid, an agent other than oxalic acid, preferably an Ig machine reducing agent such as hydrazine hydrate, hydrazine-1fCId hydroxylamine hydrochloride or phosphate, and lactic acid. 14 selected from such organic reducing agents! I or a mixture of two or more is added and then reduced by adding vanadium pentoxide to obtain a homogeneous aqueous solution containing vanadyl phosphate.

After this, the oxalic acid is preferably cooled.

The third method is to mix vanadium pentoxide, -methic acid and phosphorous acid in an aqueous medium, and convert the mixture into tetravalent vanadium ions by the reducing action of the phosphorous acid.

The aqueous solution containing vanadyl phosphate obtained by this method is
If left for a long time, a crystalline solid will precipitate giving a characteristic X-ray diffraction spectrum that is not suitable for the downstream self-reflection (Anticathode Cu=I(α)). This is not preferred from the purpose of the invention, but it is preferable to add oxalic acid when it is necessary to keep the aqueous solution stable for a long period of time.

The aqueous solution containing vanadium and phosphorus described above may contain an organic solvent such as alcohol, ketone, or ether, if necessary.

In the present invention, a slurry is prepared by mixing the above-mentioned first component and second component, and the third component silica sol,
The catalyst composition is prepared by spray drying. Silica sol is prepared in advance with IO-! ;Prepare as a slurry with an OM amount of %, mix it with the first component and the second component, and stir to make a uniform slurry. The ratio of the first component, second component, and third component is determined in the drying room i: first component: second component =
ao: go-go: Yu θ second component: third component = so = s
o~deO: 10 first component: third component -so: 5o-to
:Selected within the range of lo.

Note that the dry M amount of the second component is V for vanadium and phosphorus,
04 and P, 0. It can also be calculated as

If the amount of the first component and the second component is too small relative to the third component, the catalyst strength will be improved, but the activity will be decreased. Moreover, if the scavenging of the second component is below the above range relative to the first component, the catalyst strength tends to decrease.

The slurry thus obtained is spray-dried to
A catalyst composition with excellent fluidity and strength is obtained. The conditions for total drying are usually to adjust the air volume and liquid supply amount appropriately, and to set the gas temperature in the drying area in the range of 7-0 to 350°C. f1. The A degree is usually 200-3SO°C. The average diameter of the catalyst particles after spray drying is adjusted by adjusting the amount of liquid supplied and the rotation speed of the disk.
α is about 30 to 700 microns, more preferably 110 to
Make it 70 microns.

The catalyst composition obtained as above was 1Ioo~A
It is more preferable to use it after firing at a temperature in the range of 00°C from the viewpoint of catalytic activity. The firing is preferably carried out in air, air containing butane or butenes, or an inert gas atmosphere such as argon or nitrogen.

The catalyst composition obtained as described above has excellent fluidity, strength and activity, and is suitably used as a catalyst for producing maleic anhydride by oxidizing a hydrocarbon having a carbon number of 2, particularly n-butane.

The present invention will be explained below with reference to Examples.

Preparation of the first component Preparation of the precursor Place 3 g of demineralized water, 0 kfl, S5 phosphoric acid co/, 1!3 to 9, go hydrated hydrazine solution λ, g
skg was charged and stirred to form a homogeneous solution. Add 10 kg of sodium pentoxide/A to this while being careful not to foam.
was added little by little and dissolved. This song has a liquid temperature of 6o-t.
A low-temperature heating medium was passed through the jacket to maintain the temperature below ro°C. After the dissolution was completed and foaming stopped, precursor seed crystals/Okg were added and preheated to 140°C. A high-temperature heating medium was passed through the jacket to heat the jacket in a closed state. /
Warmed to 470'C/5 hours, j#. Subsequently, heating and stirring were continued for 10 hours. During that time, the vessel internal pressure was constant at approximately λ, 1 Ik17/ctll G. 9
After cooling to 0°C, 9 was added to 10.3 of demineralized water, and the contents were extracted and allowed to cool. When we measured the X-ray diffraction spectrum of the pale blue solid obtained by using this slurry, we found that
It was found that it completely matched that of the first component precursor shown in Table 3. The slurry was made sufficiently homogeneous using a stirrer, and then spray-dried using a spray dryer with a high-speed rotating disk to obtain a finely powdered precursor solid. The drying conditions are gas inlet temperature 330~. The temperature was 370°C and the outlet temperature was W/60°C. The P/V atomic ratio of this powder is /, θ
It was 5.

Firing of Precursor The precursor obtained above was calcined in a small rotary kiln at 520°C under nitrogen gas flow for an S distillation time of 11 minutes. The X-ray diffraction spectrum of this product was exactly the same as that in Table 1. Moreover, the ratio of five vanadiums to the total vanadium in this product was 0%.

Firing of the precursor (Part 2) The precursor obtained above was fired in a small rotary kiln under nitrogen gas flow at 0°C for 13 minutes, and then further fired in the same rotary kiln under air flow at 0°C.
C. and a residence time of 75 minutes. The xi diffraction spectrum of this product was exactly the same as that in Table 1, and the ratio of the five vanadiums to the total vanadium was 2/.

Calcination of the precursor (part 3) The precursor obtained above was heated in a small rotary kiln under the flow of air diluted with nitrogen (oxygen concentration 2q6).
℃, residence time 1S minutes. The X-ray diffraction spectrum of this product was exactly the same as that in Table 1, and the ratio of five sodium atoms was 76.3.

Firing of the precursor (1I) The precursor obtained above was heated to porcelain 1i of 27 answers. ! Put 1kg each in the baking dish and use this as the internal volume! The materials were distributed and stacked in a Matsufuru furnace of 0073. After the furnace was sufficiently purged with nitrogen gas, it was heated and fired at slo° C. for an hour. Next, air was gradually introduced into the furnace, and the mixture was heated at 330° C. for 7 hours, and then allowed to cool.

The X-ray diffraction spectrum of this product is exactly the same as shown in Table 3, and the ratio of five vanadiums is 3. I was in charge of q.

Firing of the precursor (Part S) The above (Part 3) was repeated except that the firing temperature was 400°C. A broad and weak peak appeared in Da 0. However, the β-vopo peak shown in Table 1 was not detected.The ratio of the five vanadiums in this was 75..2.

Add 9.29 kg of phosphoric acid and 7 g of oxalic acid (H,0j04・,2H,O) to 10 kg of IAI demineralized water as the second component, and heat to 10'Q. Dissolved with stirring.

Vanadium pentoxide in this? 9 was added little by little to /9 and dissolved while being careful not to foam. After leaving this to cool, add water and make a total of 4? , 1 kg, and was used as the second component.

Example: To 20.0 kg of the second component obtained above, a silica sol solution having a concentration of 2. To lf, 2, 9 and 1/kg of the fired precursor obtained above were added to prepare a slurry. This was sufficiently homogenized using a continuous wet pulverizer, and then spray-dried using a spray dryer equipped with a high-speed rotating disk. The drying conditions are: input log gas temperature θ0-. The temperature was 210°C, and the outlet gas temperature was /, 2θ~/, JO°C. Moreover, the average particle size of the obtained powder was between 5 g and 6.2 microns. This was fired in a fluidized firing furnace at 310° C. for 7 hours under air flow, and then activated by firing at jt 00'C for 2 hours under nitrogen gas flow. This was sieved and a portion having a particle size of 1I~//Aμ was collected and used as a catalyst.

Test Example The catalyst obtained above was placed in a heat-resistant glass fluidized bed reactor, and air containing 3% n-butane (Wtai) was heated to GH8V.
, jt Oθ to produce maleic anhydride. The product was collected by absorption in water. The reaction results were calculated from potentiometric titration of the absorption liquid and gas chromatograph analysis of the waste gas. The results are shown in Table-3.

Table-5/0 'IAO70J 3'1
．． 7,! 2/, 7 Q; 10 9LO
! i0.93 /I! 1. ．． ? ri3/
g9. /lI9. ．． 2g +2
3. Da Da+20 g 3. ! ;k
g, t3 Jj,, 2 4t, 33
Ta θ, 4t Da 68,? patent applicant
Mitsubishi Kasei Shiba Co., Ltd. and 7 others"''l'4;'

Claims (1)

[Scope of Claims] (1) Contains phosphorus, a nitrogen value and pentavalent vanadium,
Pentavalent vanadium accounts for 3S% or less of the total vanadium, and the Fangl component is made of a crystalline composite oxide that exhibits the following characteristic X-ray diffraction peaks, and the Fangl component is made of an aqueous solution containing vanadium and phosphorus. , and silica sol to form a slurry, and the slurry is spray-dried. X-ray diffraction peak (α to the polar Ou-) λθ (10, 2°) /4t, 2°/S, 7/g, 5 +23.0 -g, 1I 30.0 33.7 36, (2) A crystalline composite oxide in which the fang component exhibits the following characteristic X-ray diffraction peaks and does not substantially contain pentavalent vanadium is calcined in an atmosphere containing oxygen. 18. The method according to claim 17, which is prepared by firing in an oxygen-free atmosphere and then firing in an oxygen-containing atmosphere. X-ray diffraction peak λθ (+0.2°) /S, 7 79.6 11 ahead +27. / -g0g 30, Da(3) Fang λ component is an aqueous solution containing vanadyl phosphate, Claim Fang/Claim 1! Or 1
The method described in Section 2. (4) The method according to any one of claims 17 to 3, wherein the vanadium component is substantially heptavalent.