JPH0732875B2 - Process for producing fluidized catalyst for vapor phase catalytic oxidation of o-xylene - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a fluidized catalyst for producing phthalic anhydride by vapor phase catalytic oxidation of o-xylene.

<Prior Art> Conventionally, as a catalyst for producing phthalic anhydride by vapor-phase oxidation of o-xylene in a fixed bed, vanadium pentoxide is used as an inert carrier such as alundum, silicon carbide, quartz, pumice, and α-alumina. And titanium oxide (anatase type), or vanadium pentoxide and tellurium oxide, molybdenum oxide, tungsten oxide, nickel oxide, niobium oxide, tin oxide, chromium oxide and other active metal oxides, and potassium, lithium, sodium and other alkalis. A catalyst supporting a metal salt has been announced (for example, supervised by Kimio Tarama,
Practical catalysts by reaction, P.358 (1970) Chemical Industry Co., Ltd.).

In the fixed bed, in order to remove the high heat generation of this reaction, a method of uniformly filling a small diameter pipe-shaped reaction tube of about 1 inch with a catalyst and removing the heat using a heat medium for cooling the outside is adopted. However, the labor and cost for uniformly filling the catalyst in every thousands of reaction tubes are enormous, and the pressure loss and temperature of each reaction tube must be kept constant, so the equipment cost,
The burden of operation management is heavy. In addition, the cost and labor required for replacing the catalyst after deterioration are large.

Furthermore, in the case of a catalyst with an active ingredient coated on an inert carrier, there is a risk of reaction runaway due to uneven distribution of reaction gas, hot spots, or increased pressure loss due to separation and desorption of the active ingredient during operation. There is. Further, in the fixed bed, the concentration must be kept within the explosion limit of the reaction gas, and it is required to supply the gas at a low concentration, resulting in poor productivity.

In order to solve these, it is preferable to use a fluidized bed. A fluidized bed is not only capable of suppressing heat removal, suppressing uneven flow and generation of hot spots, but is also extremely advantageous in both replacement and replenishment of the catalyst. Further, it is possible to increase the concentration of the reactant, which is a great advantage in terms of productivity.

As a fluidized catalyst for producing phthalic anhydride by gas phase oxidation of o-xylene, as in the case of using naphthalene as a raw material, silica is used as a carrier, vanadium pentoxide and potassium sulfate, and molybdenum oxide and oxidation are used. A catalyst supporting tungsten, phosphorus oxide, boron oxide, etc. has been proposed (eg, BP, 941293 (1963); USP, 323.
2955 (1966)). However, when silica is used as the carrier, C
It is difficult to obtain phthalic anhydride in high yield due to over-oxidation and side reactions that generate O and CO ₂ , and an attempt was made to mix a halogen gas such as Br ₂ with the reaction gas to improve the yield. However, equipment troubles due to corrosion occur (DP, 1144709 (1963); USP, 3455962 (1969)).

A number of catalysts supporting vanadium pentoxide with titanium oxide as a carrier have been proposed (eg, BP, 1067726).
(1967); Fr. P., 1537351 (1968)), a strong catalyst is obtained by forming a melt with ammonium thiocyanate or an alkali compound. The catalysts obtained by these methods produce a melt. Decrease in specific surface area due to
The activity is remarkably low due to the decrease in the pore volume, a high reaction temperature is required, and excessive oxidation and side reactions occur simultaneously, and it is difficult to obtain phthalic anhydride in good yield.

In addition, the formation of a melt only overlaps with the high specific gravity of titanium oxide to obtain a catalyst having a significantly large bulk specific gravity, and it is difficult to perform an efficient fluidized bed reaction with these catalysts. For these reasons, the production of phthalic anhydride by gas phase oxidation of o-xylene using a fluidized bed has not been put to practical use.

<Problems to be Solved by the Invention> As described above, the present invention provides a catalyst for a fluidized bed, which is remarkably advantageous as compared with a fixed bed in a reaction of vapor phase oxidation of o-xylene to obtain phthalic anhydride, It is an object of the present invention to provide a method for producing a highly active and highly selective fluidized bed catalyst having titanium oxide as a carrier and having sufficient strength and appropriate bulk specific gravity.

The present inventors have completed the present invention as a result of earnest research on a fluidized catalyst for producing phthalic anhydride containing titanium oxide as a main component.

That is, the present invention is a titanium oxide source and a vanadium compound,
In the method for producing a catalyst for producing phthalic anhydride containing vanadium pentoxide, an alkali metal oxide, sulfur trioxide and titanium oxide by mixing an alkali metal compound and a sulfuric acid compound and then spray-drying / calcining, Provided is a method for producing a fluidized catalyst for o-xylene vapor-phase catalytic oxidation, which comprises using titanium hydroxide that produces titanium oxide having a crystallite size of 300 Å or less as a titanium oxide source.

Hereinafter, the present invention will be described in detail.

The aqueous solution for preparing the catalyst by the method of the present invention contains titanium hydroxide, a vanadium compound, an alkali metal compound, and a sulfuric acid compound.

The titanium hydroxide used in the present invention is preferably one that produces titanium oxide having a crystallite size of 300 Å or less when dried. The crystallite diameter defined in the present invention is a value obtained from the half-value width of the diffraction peak at 2θ = 25.3 ° (CuKα anatase type titanium oxide) of the X-ray diffraction diagram by the following formula based on the Debye-Sierra method.

A catalyst using titanium oxide with a crystallite size of more than 300Å has a significantly reduced wear resistance, and when used in a fluidized bed
The scattering is large and uneconomical, and at the same time, it causes the trouble of closing the cyclone and the heat exchanger. A large amount of catalyst is mixed in the reaction product, and a good fluidized state cannot be obtained.

Further, the specific surface area becomes low and the active ingredient is not uniformly and sufficiently supported, and the activity becomes remarkably low, so that a sufficient phthalic anhydride yield cannot be obtained even in a fluidized bed having a long contact time.

As used herein, the "crystallite size when dried is
"Titanium hydroxide that produces titanium oxide of 300 Å or less" is not only in the wet state (including water) called titanium hydroxide, metatitanic acid, orthotitanic acid, titania sol, titania gel, etc. It also includes powders obtained by drying at low temperature.

The titanium hydroxide used in the present invention has a crystallite diameter of titanium oxide in the powder dried at 300 ° C. of 300 Å or less, preferably 2
As long as it is 00Å or less, the raw material and the preparation method for obtaining it can be used.

As these titanium hydroxides, titanic acid obtained by the thermal hydrolysis method obtained in the intermediate step of producing pigment titanium oxide, titania sol obtained by adding an acid thereto, and the like are used. Furthermore, titanium hydroxide, titania sol, etc. obtained by neutralizing and hydrolyzing titanium sulfate, titanyl sulfate, titanium tetrachloride, etc. or by deoxidizing and hydrolyzing by an ion exchange method are used. In particular, titanium hydroxide obtained by neutralizing and hydrolyzing a solution of titanyl sulfate or the like at a low temperature of 40 ° C. or lower shows a crystallite size of several tens of liters and is suitable.

Examples of the crystallite diameter of more than 300 Å not used in the present invention, anatase of the thermal hydrolysis method that has already undergone the firing step,
Pigmented titanium oxides such as rutile, titanium hydroxide obtained by neutralization and ion exchange, calcined powder of sol, titanium hydroxide obtained by crystal growth of titanium hydroxide during hydrolysis or by autoclave, etc. correspond to this.

The vanadium compound used in the present invention is soluble in water and becomes vanadium oxide by firing in air, for example, ammonium metavanadate, vanadyl sulfate (vanadium oxysulfate), vanadium formate, vanadium acetate, vanadyl oxalate, Ammonium vanadium oxalate, ammonium metavanadate, vanadyl phosphate, vanadium oxyhalide and the like can be used. Preferred are vanadyl sulfate, ammonium metavanadate, vanadyl oxalate and the like.

The alkali metal compounds such as potassium, cesium and rubidium (hereinafter abbreviated as M ₂ O) used in the present invention include hydroxides, sulfates, carbonates, chlorides, nitrates, oxyhalides and thiosulfates. , Nitrite, sulfite, bisulfite, hydrogen sulfate, oxalate, hydrogen oxalate, and the like can be used. Preferred are hydroxides, sulfates and carbonates.

As the sulfuric acid compound, those which can be converted into sulfur trioxide by firing in air, for example, sulfuric acid, ammonium sulfate,
Ammonium hydrogen sulfate etc. are mentioned. Preferred are sulfuric acid and ammonium sulfate.

In the present invention, vanadium compounds, alcal metal compounds, and sulfuric acid are used as active ingredients.

In the present invention, the content of titanium oxide in the catalyst is 50 to 50 as TiO _2.
95 wt% is preferable, more preferably 60 to 90 wt%, the content of the active ingredient is 5 to 50 wt% as V ₂ O ₅ + M ₂ O + SO ₃ , more preferably 10 to 40 wt%, of which V ₂ O ₅ content is Is 1
Each component is mixed and prepared in an amount of 30 wt%, preferably 1 to 15 wt%. If the content of the active ingredient in the catalyst is less than 5 wt%, sufficient activity cannot be obtained, and if it is 50 wt% or more, the specific surface area of the catalyst is remarkably reduced, the dispersion of the active ingredient is deteriorated, and crystal precipitation occurs. It is not preferable because the activity and fluidity may be reduced. In the catalyst according to the present invention, the content of each active component is such that the SO ₃ / M ₂ O molar ratio is 0.1 to 6, preferably 1 to 4, and the M ₂ O / V ₂ O ₅ molar ratio is 0.1 to 5, preferably 0.5. A range of ˜3 is desirable.

The method for producing a catalyst according to the present invention includes the steps of mixing the above components, spray-drying and firing. The components may be mixed in any order, and a method of dissolving two or more components together, a method of dissolving the active ingredient in the titanium hydroxide dispersion, or the like can also be adopted.

Further, as the titanium source, it is also possible to use a mixture of titanium hydroxide that produces titanium oxide having a crystallite size of 300 Å or less and another titanium compound such as titanium oxide having a crystallite size of more than 300 Å.

After adjusting the mixed slurry obtained as described above to an appropriate concentration by concentrating it as necessary, by spray drying,
Obtain spherical microparticles. A known method can be adopted as the spray drying method. In the spraying, it is preferable to set the spraying conditions so that the weight average particle diameter of the obtained spherical fine particles is 40 to 150 μm. The spherical particles obtained are calcined in air at a temperature of 300 to 700 ° C, preferably 400 to 600 ° C.

<Examples> Hereinafter, the present invention will be specifically described based on Examples.

Example 1 (1) Preparation of Titanium Hydroxide Gel 100 kg of titanyl sulfate crystals containing 32.6% of TiO _{2 and} 51.0% of H ₂ SO ₄ were poured into 550 kg of pure water, and stirred well to dissolve the crystals. A 5% strength aqueous solution of titanyl sulfate was obtained as TiO ₂ . After cooling this to 15 ° C, add 15% ammonia water, 150 over 7 minutes (neutralize) with vigorous stirring.
A titanium hydroxide gel was obtained. The pH of this gel is 8.9,
The temperature was 29 ° C. The TiO ₂ concentration in the gel was 4.7%. 20 kg of this gel slurry was taken, poured onto a flat plate filter, dehydrated under reduced pressure from the bottom, and further 250 pure water was poured to remove the ammonium sulfate produced by neutralization. The concentration of TiO ₂ in the obtained titanium hydroxide gel was 12.6%.
Met. A part of this gel was taken and dried at 300 ° C. for 3 hours, and the crystallite diameter of the anatase type titanium oxide determined from the peak at X-ray diffraction diagram 2θ = 25.3 ° of the powder was 43Å.

(2) Preparation of catalyst Take 138 kg of gel with TiO ₂ concentration of 12.6% obtained by repeating washing with pure water on a flat plate filter, add 240 kg of pure water, and stir well to obtain 4.6% of TiO ₂ . It was made into a slurry.
Separately prepared 6.1 kg of vanadyl sulfate solution containing 19.6% as V ₂ O ₅ , 6.3 kg of potassium sulfate solution containing 15.0% as K ₂ SO ₄ and 2.3 kg of ammonium sulfate solution containing 20.0% as SO ₃ were mixed. After that, a dilute nitric acid solution was further added to adjust the pH of the slurry to 3.5. While stirring this slurry, it is heated to evaporate the water content, and TiO ₂ + V ₂ O ₅ + K ₂ SO ₄ + SO ₃
Was concentrated to a concentration of 21.2%.

Further, the slurry was well dispersed by a homogenizer, spray-dried by a disc-type spray drier, and the obtained powder was dried at 150 ° C for 24 hours and then calcined at 500 ° C for 3 hours to obtain catalyst A (oxidation in this catalyst). The crystallite diameter of titanium is 52Å
Met).

Example 2 A titanium hydroxide gel was obtained by diluting a metatitanic acid slurry, which is an intermediate product for producing pigment titanium oxide, and then performing the same neutralization and washing as in Example 1. The concentration of TiO _{2 in} this gel was 30.8%. The crystallite size of the powder obtained by taking a portion of this gel and drying it in the same manner as in Example 1
It was 170Å. Using this gel, a powder containing an active ingredient was obtained in the same manner as in Example 1, and then calcined at 500 ° C. for 3 hours to obtain a catalyst B.

(Example 3) In the same manner as in Example 1, four types of titanium hydroxide gels having different crystallite diameters were obtained by changing the gel preparation conditions, and the catalysts C, D, E, and F were used as starting materials. Obtained. Table 1 shows the conditions for producing the titanium hydroxide gel and the crystallite size.

Example 4 The titanium hydroxide gel prepared for Catalyst E of Example 3 was used
It dried at 0 degreeC for 6 hours, and obtained the powder. The crystallite size of this powder was 120Å.

This powder was resuspended in pure water and then dispersed well with a homogenizer to obtain a catalyst G according to the method of Example 1.

(Comparative Example 1) Fine particle silica sol which was previously Na-free using a cation exchange resin (SiO ₂ concentration 10.5%, particle diameter 5.0 μm, N
a ₂ Owt / SiO ₂ wt, 0.002) 70.9 kg and vanadyl sulfate solution (V ₂ Owt
₅ as 19.9%) 2.0 kg, potassium sulfate solution (K ₂ SO ₄ as 14.1%) 10.9 kg, ammonium sulfate solution (SO ₃ as 1
After thoroughly mixing 3.6 kg of 8.5%), the solid content (V ₂ O ₅ + K ₂ SO
₄ + SO ₃ + SiO ₂ ) and heated to 18% concentration. This slurry was spray-dried with a spray dryer, and the obtained powder was dried at 150 ° C. for one day and then calcined at 500 ° C. for 3 hours to obtain a catalyst H having silica as a carrier.

(Comparative Example 2) A commercially available anatase type titanium oxide powder (A # 200 manufactured by Teikoku Kako Co., Ltd.) was suspended in pure water to prepare a slurry having a concentration of 30% as TiO ₂ . Using this slurry, a catalyst I was obtained in the same manner as in Example 1.

Comparative Example 3 The titanium hydroxide gel used in Example 4 was dried at 110 ° C. in a dryer.
After drying for 18 hours at 450 ° C., it was baked at 450 ° C. for 3 hours to obtain anatase type titanium oxide powder. The crystallite size of this powder was 620Å.

The powder was diluted with pure water to 20% as TiO ₂ and diluted nitric acid solution was added to adjust the slurry pH to 3, and then well dispersed using a colloid mill. Using this slurry, a catalyst J was obtained in the same manner as in Example 1.

Comparative Example 4 The washed titanium hydroxide gel obtained in Example 2 was washed with pure water.
At the same time as diluting to 15%, the pH of the slurry was adjusted to 2 using a dilute nitric acid solution. This slurry was placed in an externally heated autoclave equipped with a stirrer, and hydrothermally treated at 170 ° C for 72 hours while stirring. The crystallite diameter of the obtained titanium hydroxide is
It was 320Å. Using this titanium hydroxide, a catalyst K was obtained in the same manner as in Example 1.

(Example 5) A catalyst L was obtained by using the dried titanium hydroxide powder having a crystallite diameter of 120Å used in Example 4 and using cesium sulfate instead of potassium sulfate according to the method of Example 1.

(Example 6) A catalyst M was obtained by using the dry powder of titanium hydroxide having a crystallite diameter of 120Å used in Example 4 and using rubidium sulfate instead of potassium sulfate according to the method of Example 1.

Table 2 shows the chemical composition and physical properties of the catalysts obtained in the above Examples and Comparative Examples, and Table 3 shows the measurement results of the oxidation activity of o-xylene.

The fluid catalytic properties were evaluated by bulk specific gravity and wear rate, and the reaction properties (activity, selectivity) were evaluated by o-xylene conversion rate and phthalic anhydride selectivity measured by a microreactor (fixed bed system).

The physical properties were measured by the following methods.

Specific surface area Measured using the BET method.

Pore volume Measured by the nitrogen gas adsorption method.

Bulk specific gravity was measured using the graduated cylinder method.

Abrasion rate ACC method (method described in British Patent 737429) 5
The average particle size ratio of abrasion during 20 hours was measured.

The particle size corresponding to a crystallite size of 50% by weight was measured by the Micro Mesh Sieve method.

It was measured by X-ray diffraction in the same manner as above.

The catalyst obtained by the present invention has the following properties.

Specific surface area 10 to 200 m ² / g Pore volume 0.1 to 0.6 cc / g Bulk specific gravity 0.4 to 1.8 g / cc Wear rate 5% or less Average particle size 40 to 150 μm Crystallite size of titanium oxide in catalyst 20 to 300 Å The reaction characteristics (activity selectivity) are microreactor (fixed bed system), that is, a tubular reactor with a catalyst of the above (A to M).
1 g was charged, at a reaction temperature of 340 ° C., an o-xylene feed rate of 0.85 g / Hr and an air feed rate of 7.5 Nl / Hr were introduced, and reaction products (maleic anhydride as a by-product other than phthalic anhydride, o
-Including tolylaldehyde) was analyzed by gas chromatography to examine the o-xylene conversion rate and the phthalic anhydride yield. The results are shown in Table 3.

From these results, it was found that the use of the catalyst of the present invention significantly increased the o-xylene conversion rate and the yield of phthalic anhydride.

<Effects of the Invention> Since the catalyst according to the present invention has an appropriate specific surface area and pore distribution, it is highly active at low reaction temperatures and exhibits high selectivity.

Also, because it has high wear resistance, the wear rate during flow is low,
Moreover, since it has an appropriate bulk specific gravity and the sphericity of the particles is high, it has excellent fluidity.

It was found that the yield of phthalic anhydride obtained by conversion of o-xylene was higher than that of the conventional catalyst.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yusaku Arima 1560 Hirotari, Onga-cho, Onga-gun, Fukuoka (72) Inventor Susumu Fujii 1-1-34 Nijima, Wakamatsu-ku, Kitakyushu, Fukuoka

Claims (1)

[Claims] 1. An anhydrous solution containing vanadium pentoxide, an alkali metal oxide, sulfur trioxide and titanium oxide by mixing a titanium oxide source with a vanadium compound, an alkali metal compound and a sulfuric acid compound and then spray-drying and firing the mixture. A method for producing a catalyst for producing phthalic acid, which comprises using titanium hydroxide that produces titanium oxide having a crystallite size of 300 Å or less as the titanium oxide source, and producing a fluidized catalyst for o-xylene vapor phase catalytic oxidation. Method.