JPS5992025A - Preparation of oxidation catalyst - Google Patents

Abstract

PURPOSE:To enhance the flowability, the strength and the activity of a catalyst, by a method wherein a slurry prepared by mixing a solution containing phosphoric acid and tetravalent V and a silica sol in a slurry containing specific P-V type crystalline oxide is spray dried and the obtained composition is baked. CONSTITUTION:An aqueous solvent containing pentavalent P and tetravalent V is heated to 110-250 deg.C to prepare an aqueous slurry containing V-P type crystalline oxide showing X-ray diffraction spectrum (to a cathode, Cu-Kalpha) at 2theta(+0.2 deg.), 15.7 deg., 19.6 deg., 24.2 deg., 27.0 deg., 28.8 deg. and 20.4 deg.. A vanadyl phosphate solution containing phosphoric acid and tetravelent vanadium and having vanadyl phosphate formed by a part thereof and a silica sol are mixed in said aqueous slurry to prepare a homogeneous slurry. This slurry is spray dried and the formed solid particle is baked to obtain a V-P type oxidation catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an oxidation catalyst, and in particular to a method for producing an oxidation catalyst.
- A method for producing a catalyst suitable for the production of maleic anhydride by catalytic gas phase oxidation of butane.

A hammer compound containing vanadium, phosphorus and oxygen is used to produce butane,
It is known that it is an effective catalyst for the production of maleic anhydride by catalytic gas phase oxidation of butene, butadiene, etc., and numerous proposals have been made regarding its production method. In particular, for the production of maleic anhydride from n-butane, the following
Vanadyl pyrophosphate ((■0)t''20.), a crystalline compound that shows the characteristic X-ray diffraction spectrum shown in the table, is said to be effective (B, Bordθs, P.

Courtine, J., 0ata1. ,! ri, x
36 (/yzv)).

Table 1 (vO)*P*Oy (D ni02
0 ko 3.00 700 2g, g 0 90 3o, oo s.

33.7' lI.

a6. On the other hand, since the production of maleic anhydride by catalytic gas phase oxidation of n-butane is accompanied by a large exotherm, a fluidized bed reaction system is considered appropriate.

The present invention includes phosphorus and vanadium, and the xfm of Table 1
A method is provided for producing a catalyst that provides a diffraction spectrum that matches the diffraction spectrum and is suitable for use in fluidized beds.

According to the present invention, an aqueous solution containing five phosphorus and tetravalent vanadium is added to the slurry obtained in the seventh step of the first step of obtaining an aqueous slurry containing //θ~coSO oxide, A homogeneous slurry obtained by mixing a vanadyl phosphate solution containing phosphoric acid and tetravalent vanadium and at least a part of which forms vanadyl phosphate and silica sol is obtained in the second step. By sequentially performing the third step of spray drying the slurry and the second step of firing the solid particles generated in the third step, a spectrum matching the X-ray diffraction spectrum shown in Table 1 can be obtained, and the fluidized bed A governoradium-phosphorous oxidation catalyst suitable for use in the present invention can be produced.

'Table 3 X-ray diffraction spectrum (anticathode; α to Ou)
．． 2°) Intensity ratio/! r, ri' 100/9. A0!
j;0 24t, KOIIθ KOKU o6 da5koza,za0
koS3θ, 4g0gθ (In addition, a weak peak with an intensity ratio of about 10-20 is seen at 1g, 0, J/, to, 32..2°) To explain the present invention in detail, the present invention As the 7th degree,
Contains tetravalent vanadium and five phosphorus, and
A crystalline composite oxide giving the X-ray diffraction spectrum shown in the table is produced by hydrothermal synthesis. Phosphorus-vanadium-based crystalline composite oxides that give the X-ray diffraction spectra shown in Table 2 are known, and several manufacturing methods have been reported (Japanese Patent Application Laid-open No. 5/-9, 1983; No. 90, Same s6-1 IS No., U
, S, P, 41. Kot3. (See λgt issue).

Unlike these known methods, the method of the present invention produces the above-mentioned crystalline composite oxide by hydrothermal synthesis. According to this method, the average particle diameter determined by the Coulter counter method is 0.
．． Extremely fine crystals of 2 to 70 microns are produced. Therefore, it is not always easy to separate by filtration, but
It is rather convenient to add other ingredients to the slurry and spray dry it to use as a catalyst. Hydrothermal synthesis involves reacting five vanadium compounds, such as vanadium pentoxide, in an acidic aqueous solution containing phosphoric acid and a non-halogen reducing agent such as hydrazine hydrate. an aqueous solution containing
θ~2jOC preferably /2θ~lzaOC 0.3-2
This is done by holding it for about 0θ time (Tokugansho!
(See t-32//θ issue). The phosphoric acid concentration in the acidic aqueous solution is 5 to Sθ (weight), preferably 5 to 3 t (weight) %. If the phosphoric acid concentration is too high, vanadium pentoxide may react with the phosphoric acid before being reduced, and the liquid viscosity will also become significantly high, making handling difficult.

Please note that the stoichiometric amount of reducing agent required to reduce five vanadiums to tetravalent is sufficient, and usually 95
It is used in the range of ~/2θ. The reducing agent is preferably a non-halogen inorganic reducing agent such as hydrazine, hydroxylamine, or their phosphoric acid. If desired, an organic reducing agent such as oxalic acid may also be used, but this is not industrially advantageous. In addition, vanadium is reduced by dissolving phosphoric acid and a reducing agent in an acidic aqueous solution prepared in advance.
This should be done by adding vanadium pentoxide, which can produce crystals of high quality.

During hydrothermal synthesis, it is preferable to add a small amount of finely ground seed crystals to the aqueous solution. The crystalline composite oxide produced by this hydrothermal synthesis is Habo (V2O3) (ptOs).
(2HtO) '7) The composition formula can be seen.

Therefore, since the ratio of phosphorus to vanadium is theoretically 80 in P/V atomic ratio, the vanadium compound and phosphorus compound should be reacted within the range of θ1g to HA2j in P/V atomic ratio. is preferred.

Further, vanadium in this crystalline composite oxide 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 female metal ions is used as a catalyst, it can significantly improve the activity and stabilize the activity. The substitution ratio is such that the ratio of these metals in the crystalline composite oxide is 0.002 to 0.01 h as polymetal per 1 gram atom of vanadium,
More preferably, it is selected within the range of 0.07 to O32 gram atom. In order to introduce such other metal ions into the composite oxide, these metal ions are added to the hydrothermal synthesis system using inorganic salts such as hydrochloride, sulfate, nitrate, carbonate, etc., or organic salts such as oxalate. One method is to add it in the form of

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 -〇〇 is within ±0.2°.

In the present invention, the vanadyl phosphate solution added to the slurry obtained in the first step described above is a solution containing tetravalent vanadium and five phosphorus, at least a part of which exists as vanadyl phosphate. be.

This solution has the effect of acting as a binder between the composite oxide in the slurry obtained in the first step and the silica sol as a support described later, and contributes to improving the fluidity and strength of the fluidized catalyst. Although the judgment of this solution is not particularly limited, some examples are shown below.

Generally, it is obtained by adding and dissolving a reducing agent and vanadium pentoxide in an aqueous solution containing five phosphorus compounds, for example, phosphoric acid. The atomic ratio of phosphorus to vanadium in an aqueous solution is θ,! A range of ˜lθ is preferable. Generally, aqueous solutions containing vanadyl phosphate are unstable and may be difficult to keep stable for long periods of time, so oxalic acid may be present to stabilize the aqueous solution.

The amount is in the molar ratio of oxalic acid to vanadium element, and is preferably in the range of 0.0 to 1. If the amount of oxalic acid is too large, it will have an unfavorable effect on the mechanical strength, bulk density and active surface of the catalyst. In other words, a range in which the molar ratio of oxalic acid to vanadium element is less than or equal to 50% can be said to be a range in which vanadyl oxalate is not formed.

Examples of the jJll method for aqueous solutions include the following methods.

First, in an aqueous solution containing phosphoric acid and oxalic acid,
A method of preparing an aqueous solution containing vanadyl phosphate and oxalic acid by adding vanadium pentoxide so that the molar ratio of oxalic acid to vanadium atoms is 8 or less, and preferably td, 0.7 or more. be. Specifically, it is produced by dissolving oxalic acid in an acidic aqueous medium containing phosphoric acid, and adding vanadium pentoxide while maintaining the temperature at which reduction proceeds by slight heating. According to this method, after the completion of the reduction, less than half a mole of oxalic acid exists per vanadium atom.

First, a reducing agent other than oxalic acid is added to an acidic aqueous solution containing phosphoric acid, preferably an inorganic reducing agent such as hydrazine hydrate, hydrochloride or phosphate of hydrazine or hydroxylamine, or an organic reducing agent such as lactic acid. One or a mixture of two or more selected from the following are added, and vanadium pentoxide is then added to reduce the solution to obtain a homogeneous aqueous solution containing vanadyl phosphate. After this, oxalic acid is preferably added.

The third method is to mix vanadium pentoxide, phosphoric acid and phosphorous acid in an aqueous medium and convert the mixture into tetravalent vanadium ions by the reducing action of the phosphorous acid. From the aqueous solution containing vanadyl phosphate obtained by this method, a crystalline solid which gives a Q in-machine X-ray diffraction spectrum as shown in Table 3 below precipitates after a few steps.

Table 3 (Anticathode; α to Ou) Such precipitation of crystalline solids is not desirable from the purpose of the present invention, and when it is necessary to keep the aqueous solution stable for a long time, oxalic acid should not be added. is preferred.

The vanadyl phosphate solution containing vanadium and phosphorus may contain an organic solvent such as alcohol, chthon, or ether, if necessary.

In the present invention, a slurry is prepared by mixing the above-mentioned vanadyl phosphate solution and silica sol with the slurry obtained in the first step, and the slurry is blown and dried. The silica sol was prepared in advance at a concentration of 10-A; 0 wt%, and the first
The slurry obtained in the step and the vanadyl phosphate solution are mixed and stirred to form a uniform slurry. The proportions of the slurry, vanadyl phosphate solution and silica sol in the first step are:
Slurry vanadyl diphosphate solution in dry form i% = 20:
Z θ ~ g θ: 2 θ, vanadyl phosphate M liquid nizirikasol =
ro:so~riθ:/θ, slurry: silica sol-go
: So~? θ: Selected within a range of 10. Note that the dry M amount of the vanadyl phosphate solution can also be calculated as vanadium, phosphorus, and P2O1+.

The amount of slurry and vanadyl phosphate solution in the first step is too small relative to the silica sol.

Catalyst strength improves, but activity decreases.

Furthermore, if the amount of the vanadyl phosphate solution is less than the above range relative to the slurry in the first step, the catalyst strength tends to decrease.

When mixing the slurry, vanadyl phosphate solution, and silica sol in the first step, use a wet mixing device such as a ball mill, rod mill, stirring mill, sand grinder, Ultra Homo Mixer, Ultra Turrax, or ultrasonic mill to achieve as homogeneous mixing as possible. Preferably, it is a slurry.

The slurry obtained in the first step described above is then spray dried into spherical solid particles. Spray drying conditions are usually
Inlet temperature of drying gas is 10θ~3SOC1 outlet temperature is 1
00~3! Ensure that QC is achieved. Further, the liquid supply angle and the disk rotation speed are adjusted so that the average particle diameter of the solid particles obtained by spray drying is in the range of about 3θ to loo microns. A more preferable range of average particle diameter is
~70 microns.

The solid particles obtained as described above are further calcined to form an oxidation catalyst. Firing is usually tio.

~toor2. Preferably, this is done from 0 to 6001Z'-. The firing atmosphere is air or butane,
Air containing organic substances such as butenes can be used.

Firing may also be carried out in an inert gas atmosphere such as argon or nitrogen. By this firing, the crystalline oxide produced in the first culm in the solid particles is changed into a composite oxide giving the X-ray diffraction pattern shown in Table 1.

The oxidation catalyst obtained by the method of the present invention has excellent fluidity, strength, and activity, and is suitable as a catalyst for producing maleic anhydride by oxidizing hydrocarbons having several grams of carbon atoms, particularly n-butane.

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Example - Preparation of crystalline oxide slurry In a 100 t glass-lined jacketed pressure vessel, add 3 g of demineralized water, 3 g of θ, and 3 g of G3 phosphoric acid.
g, KO% hydrazine hydrate solution 2, prepare gjky,
Then, without stirring, add vanadium pentoxide powder/A, 1IO
ky was added and dissolved in small portions, being careful not to foam. During this time, in order to suppress the temperature rise due to heat generation and maintain the slip temperature between tθ and gOC, a low-temperature heating medium was circulated inside the jacket to remove heat.

Addition of vanadium pentoxide was completed in about 7 hours, and a blue vanadyl phosphate solution was obtained. Seed crystals /, Okg were added to this, and then /AOC heating medium was circulated inside the jacket to heat it. The temperature was raised to the liquid temperature/DaOC in 2 hours, and the trench was subjected to hydrothermal treatment for 10 hours. During this time, the pressure is approximately -,4
It was 1 kg. ? After cooling to OC, demineralized water 10.3k
g was added to adjust the solid concentration in the slurry to about 35 g, and the slurry was discharged. When we performed X-ray diffraction measurements on this solid, we found that
It was found that it exhibited the main diffraction peaks shown in Table 2, and it was confirmed that it was a pure crystalline oxide. broken coulter
When the particle size distribution of the solid in the slurry was investigated using a counter method, the average particle size of θ and μ was shown. The charging standard P/'v atomic ratio of this oxide slurry is 80S.

<Production of vanadyl phosphate solution> Add 6.0 kg of gs phosphoric acid to 5.0 kg of demineralized water. To Wokota, 7 g and 9 kg of oxalic acid (H2O, 0, .uH20) was added and dissolved while stirring while heating to θC. Next, vanadium pentoxide 11.3/9 was foamed with a small amount of ψ and 0 g mol of oxalic acid per gram atom, and this solution was stable and did not cause solid precipitation even if stored at room temperature for 77 months. It didn't happen.

<Production of slurry for spray drying and spray drying> To 20 kg of the governoradyl IJ acid solution obtained above, 1 kg of the crystalline oxide slurry A obtained above was added with stirring. Then, the beating (,2 while lI.

Tisilica sol solution 3. g, lky were added. After processing this slurry with a continuous wet grinder and thoroughly homogenizing it,
Spray drying was performed using a spray dryer with a high speed rotating disc. The solids concentration of the slurry is 20%;
Drying gas input temperature so'6. The temperature was 0.001m/g.theta.C. The average particle diameter of the obtained particles was srμ, and both sphericity and strength were good.

<Calcination and activity test> The solid particles obtained above were placed in a fluidized bed and heated at 7
Calcinate under air atmosphere for 5 hours, followed by under nitrogen atmosphere for 5 hours.
The catalyst was fired at 00C for 2 hours. Sieve and q daμ
A particle size fraction of ~//6μ was obtained and tested for activity using a small fluidized bed reactor. That is, a catalyst, 20@l, was charged into a reaction tube with an inner diameter of 7 mm, and n-
Pig/Part 3/! :F/, gas mixture GH8V 3θO
It was introduced into the reactor and reacted in such a manner that The product was absorbed into water, and the reaction results were determined by potentiometric titration of the aqueous solution and gas chromatographic analysis of the waste gas. The optimum reaction temperature is 1 Ips'r3, the butane reaction rate is 2.0 cm, and the maleic anhydride yield is 1.
Ig, 0%.

Note that the catalyst obtained by calcination is
The diffraction peaks shown in the table were obtained, indicating that this was a crystalline oxide produced by hydrothermal synthesis during catalyst preparation. Also, what is the intensity of this diffraction peak?

The strength almost matched that expected from the amount of crystalline oxide used in catalyst preparation. Therefore, it is considered that the crystalline oxide is not destroyed in the catalyst preparation process, and it is also presumed that the oxide in the vanadyl phosphate solution used as the binder is not converted to the crystalline oxide.

Patent applicant: Mitsubishi Chemical Industries, Ltd. Representative Patent Attorney Hase - Others/Names

Claims (3)

[Claims] (1) An aqueous slurry containing a vanadium-phosphorus crystalline oxide that exhibits the characteristic xi diffraction spectrum shown below by heating an aqueous solvent containing five phosphorus and tetravalent vanadium to /10-coSOC The first step is to mix the slurry obtained in the first step with a vanadyl phosphate solution containing phosphoric acid and tetravalent vanadium and at least a part of which forms vanadyl phosphate, and a silica sol. It is characterized by consisting of the following steps: a first step of making a homogeneous slurry, a third step of spray drying the sludge IJ obtained in the first step, and a third step of calcining the solid particles produced in the third step. A method for developing a vanadium-phosphorus oxidation catalyst. Xa diffraction spectrum (Anticathode; α to Ou) Coθ (±
0.2°) /! , ri0 /9.6°211, co0 core, θ0 . 2g, za 0 3θ, da 0 (2) The vanadyl phosphate solution in the first step is
A method according to claim 1, characterized in that it contains no more than 8-gram moles of oxalic acid per gram atom. (3) The P/V atomic ratio of the vanadyl phosphate solution in the first step is 0. ! 3. A method according to claim 1 or 2, characterized in that it is in the range r-10. (・1) The P/V atomic ratio of the fired product obtained in the th step is θ
, t to /, S.