JPH0451227B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a method for producing a catalyst for producing phthalic anhydride by vapor phase catalytic oxidation of naphthalene. This invention relates to a method for producing a fluidized catalyst for gas phase catalytic oxidation of naphthalene in which vanadium, potassium sulfate, and sulfuric acid are supported on silica. <Prior art> Conventionally, as a fluidized catalyst for gas phase catalytic oxidation of naphthalene, a catalyst in which vanadium oxide, a potassium component, and sulfuric acid are supported on silica has been used.
Various methods for producing such catalysts have been proposed. Japanese Patent Publication No. 40-15096, British Patent No. 885651, and U.S. Patent No. 2973371 disclose that an ammonium vanadate solution is added to a potassium silicate solution to prepare a mixed slurry of silica hydrogel, a potassium component, and a vanadium component. A method (so-called post-deposition method) is disclosed in which the mixed slurry is then mixed with sulfuric acid to neutralize it, followed by spray drying and calcination to prepare a fluidized catalyst. In addition, British Patent No. 1053474 discloses that a carrier is prepared by spray-drying the silica hydrogel obtained by neutralizing dilute silica soda with sulfuric acid, gelling it, and washing it. A method for preparing a catalyst by supporting a mixed solution of vanadium and sulfuric acid (so-called impregnation method) is disclosed. <Problems to be solved by the present invention> However, the above-mentioned Japanese Patent Publication No. 40-15096,
In the post-deposition method described in British Patent No. 885651 and US Patent No. 2973371, even if the specific surface area of the silica support is increased in order to highly activate the catalyst, a low melting point composition is formed during the calcination process. It is not possible to increase the specific surface area or pore volume of the resulting catalyst because it is greatly influenced by active ingredients that are susceptible to oxidation. In fact, the specific surface area of the silica support is 200 to 850 m ² /g.
It is stated that even if a silica support is used, the specific surface area of the catalyst is only 75 m ² /g or less, and that the pore volume of the catalyst obtained becomes smaller as a silica support with a larger specific surface area is used. There is. That is, in these methods, the desired high specific surface area,
It is not possible to produce catalysts with pore volumes. However, in the gas phase catalytic oxidation method of naphthalene, it is necessary to lower the maximum reaction temperature and increase the specific surface area of the catalyst in order to improve the yield of phthalic anhydride. This method was not sufficient as a method for producing a catalyst for gas phase catalytic oxidation of naphthalene. Furthermore, in the conventional post-deposition method of preparing silica hydrogel from potassium silicate and ammonium vanadate, there are restrictions on the composition that can be gelled.
There was also the problem that a highly active catalyst could not be obtained because of restrictions on the composition of the resulting catalyst. On the other hand, in the catalyst prepared by the impregnation method, the distribution of the active component within the catalyst particles is non-uniform, and the content of the active component varies depending on the catalyst particle size.
Therefore, when the catalyst is used, local heat generation occurs in the catalyst,
Since it causes sintering of the active ingredient V ₂ O ₅ and scattering of SO ₃ , it has problems in that it has poor heat resistance and significantly deteriorates the performance of the catalyst. In particular, commercially available catalysts in which crushed silica particles are impregnated with active ingredients have not only poor wear resistance but also serious problems due to non-uniform distribution of the active ingredients due to the preparation method. . On the other hand, in order to obtain a catalyst in which the active ingredient is uniformly supported by the impregnation method, it is sufficient to use a carrier having a very large specific surface area and pore volume. However, a catalyst obtained by impregnating such a carrier with an active ingredient has an extremely low bulk density and extremely poor wear resistance. Therefore, when the catalyst is used, the specific surface area of the catalyst becomes small, resulting in a problem that the performance of the catalyst is eventually deteriorated. On the other hand, US Pat. No. 2,941,957 describes the use of a silica carrier prepared by spheroidizing sodium silicate in a non-aqueous solvent in order to improve the wear resistance of the catalyst. However, the silica carrier obtained by this method has limited properties such as specific surface area and pore volume, and because it is prepared by an impregnation method, it does not solve the problem of uneven distribution of active ingredients. It was still there. As mentioned above, in the conventional post-deposition method using silica hydrogel obtained by neutralizing an alkali silicate such as potassium silicate as a silica source, the catalyst composition to be prepared is limited, and the catalyst with a high specific surface area is In addition, with the impregnation method in which a silica carrier is prepared in advance and then used, the prepared catalyst has poor abrasion resistance and is difficult to obtain a catalyst with a high specific surface area. Since it is difficult to uniformly support the components, there are problems such as poor heat resistance and large performance deterioration. The present invention aims to solve such problems, and has a high specific surface area, appropriate pore volume and bulk density, uniform support of active ingredients, wear resistance,
The object of the present invention is to provide a method for producing a highly active fluidized catalyst for gas phase catalytic oxidation of naphthalene that has excellent heat deterioration resistance. In other words, in the present invention, the specific surface area, pore volume, and bulk density of the catalyst can be adjusted as desired, and the reaction conditions can be varied over a wide range in the gas phase catalytic oxidation of naphthalene using the fluidized bed method. It is an object of the present invention to provide a method for producing a fluidized catalyst for gas-phase catalytic oxidation of naphthalene, which produces a catalyst having excellent heat resistance that can be used in the gas phase catalytic oxidation of naphthalene. <Means for Solving the Problems> As a result of intensive research to solve the problems associated with conventional catalyst manufacturing methods, the present inventors have found that silica sol is generally used as a raw material for silica, which serves as a catalyst support. Polysilicic acid solution (a sol containing polysilicic acid immediately after neutralizing or ion-exchanging low-concentration sodium silicate or potassium silicate, which is extremely unstable) is used. The present inventors have discovered that it is sufficient to use a hydrogel obtained by a specific method from a silica sol containing colloidal silica with an average particle size of 4 to 50 nm, and have accomplished the present invention. That is, the present invention provides a method for producing a fluidized catalyst for gas-phase catalytic oxidation of naphthalene by mixing a silica source, a vanadium compound, a potassium compound, and a sulfuric acid compound, and then spray-drying and calcining the fluidized catalyst for the gas-phase catalytic oxidation of naphthalene. After adding an acid to a silica sol containing colloidal silica with a diameter of 4 to 50 nm to make it acidic, adding a base to adjust the pH of the silica sol to 6 to 11, and heating, the resulting silica hydrogel is used. A method for producing a fluid catalyst for gas phase catalytic oxidation of naphthalene is provided. The present invention will be explained in detail below. In the present invention, the first silica source has an average particle size of 4
A silica sol containing colloidal silica of ~50 nm, preferably 4-25 nm is used. Here, colloidal silica is particulate polysilicic acid that, when made into a sol, does not settle when left standing or by ordinary centrifugation. Further, the average particle diameter is determined by the following formula. Average particle diameter (nm) = 6000/specific surface area (m ² /g) x 2.
2 In the formula, the specific surface area is GWSears, Analytical
It was determined by the titration method using caustic soda described in Chemistry Vol. 28, No. 12, Dec. P. 1981 (1956). Therefore, in other words, the present invention has a specific surface area of 700~
A silica sol containing 50 m ² /g of colloidal silica is used. A sol of colloidal silica with an average particle diameter of less than 4 nm is relatively stable compared to a polysilicate solution immediately after neutralizing or ion-exchanging sodium silicate, but it is inferior in stability as a sol at high concentrations.
Therefore, even if colloidal silica with an average particle diameter of less than 4 nm is used, only a low concentration of sol can be obtained, spherical particles cannot be obtained, and the abrasion resistance and fluidity of the catalyst will be poor, which is not preferable. Moreover, such colloidal silica generally contains a large amount of alkali metal as a stabilizer, which is undesirable as it contributes to a decrease in catalytic activity. Furthermore, if a silica sol containing colloidal silica with an average particle diameter of less than 4 nm is used, it will be difficult to obtain spherical particles when spray-drying and shaping the catalyst into spherical particles, resulting in poor wear resistance of the catalyst. Not only is the fluidity poor, but when the catalyst is used, the specific surface area and pore volume of the catalyst are reduced due to the influence of low-melting substances such as sulfuric compounds and potassium compounds, which ultimately leads to a decrease in catalytic activity, which is undesirable. On the other hand, when colloidal silica having an average particle diameter of more than 50 nm is used, the specific surface area of the catalyst becomes small, which not only lowers the catalytic activity but also reduces the abrasion resistance of the catalyst, which is not preferable. Therefore, in the present invention, the average particle diameter is 4 to 4.
Colloidal silica in the range of 50 nm, preferably 4 to 25 nm, is used. When colloidal silica in this range is used, the specific surface area of the catalyst to be prepared is in the range of 250 to 50 m ² /g, and varies depending on the specific surface area of the colloidal silica. That is, by using colloidal silica with a large specific surface area, a catalyst with a large specific surface area can be obtained. Moreover, the pore volume and bulk density can also be controlled, and a catalyst with desired characteristics can be obtained. In addition, when a silica sol containing colloidal silica with an average particle diameter of 4 to 50 nm is used, the sphericity of the adjusted catalyst particles increases, resulting in improved wear resistance and
A catalyst with excellent fluidity can be obtained. As such a silica sol, one obtained by polymerizing low molecular weight silicic acid under alkaline conditions can be used. Such silica sol is 20wt as SiO ₂
% and is characterized by a viscosity of less than 50 c.P. and stability for months to years. Therefore, it is different from a polysilicate solution immediately after neutralizing or ion-exchanging low concentration sodium silicate or potassium silicate, which is generally called silica sol.
In other words, polysilicate liquid, which is generally referred to as silica sol, is essentially a sol of polysilicate with a very low molecular weight, and unless the concentration of SiO ₂ is less than 7wt%, stable polysilicate liquid cannot be obtained. Not obtained,
Moreover, these differ from the silica sol used in the present invention in that they become gel-like after several minutes to several days. As the silica sol that can be used in the present invention, commercially available silica sol can be used as long as the average particle size of the colloidal silica is 4 to 50 nm. SI−
45P, SI−50, SI−40, SI−30, SI−350, SI−
550, SN, (products of Catalysts Kasei Kogyo Co., Ltd.), -30, -N, -O (products of Nissan Chemical Industries, Ltd.) under the trade name Snotex, HS-40, HS- under the trade name Rudotx
Examples include 30, LS, SM-30, TM, and AS (all EIDupont products). However, when using it, Na ₂ O/
0.005 to 0.05 as SiO ₂ (weight ratio) The content of sodium contained in advance is 0.015 as Na ₂ O / SiO ₂
In the prepared catalyst,
It is preferable that the amount of Na ₂ O is 1.0 wt% or less, preferably 0.3 wt% or less. in catalyst
This is because if the amount of Na ₂ O exceeds 1.0 wt%, the reaction rate of naphthalene will decrease, which is not preferable. Therefore, among the commercially available silica sol, Cataloid S-20L, SN, Snotex -O, -N and Rudotux AS, which have low sodium content,
It is preferable to use LS etc. as is, but
Other foods containing relatively large amounts of sodium include
It is preferable to reduce sodium before use. As a method for removing sodium, well-known methods can be used, such as a method using a cation exchange resin, and a method in which sodium is neutralized with an acid and then removed as a salt using an ultrafiltration membrane or the like. In the present invention, the silica sol as described above has a pH of
1 regardless of whether it is acidic or basic.
The method is characterized in that the silica hydrogel obtained by adding acid to make an acidic silica sol, neutralizing it by adding a base, and heating it is used as a silica source for a catalyst. The reason why silica sol is made acidic once and then neutralized to obtain silica hydrogel is to obtain silica with a gel structure that does not change during subsequent steps such as preparation and use of the catalyst. This is to obtain a silica hydrogel that maintains a strongly aggregated state. To obtain such silica hydrogel,
Add acid to silica sol to adjust the pH to acidic range, preferably
After setting the pH to 2 or less, more preferably 1.5 or less,
It is advisable to adjust the pH of the silica sol to 6-11, preferably 6.5-10 by adding a base. If the neutralization pH is below 6, the gelation reaction will not be sufficient and it will be difficult to obtain a light catalyst, and the silica hydrogel will change significantly due to mechanical forces such as stirring or spray drying conditions, making it difficult to obtain a stable catalyst. Have difficulty. On the other hand, if the neutralization pH is 11 or more, the specific surface area of the catalyst obtained by heating decreases, which is not preferable. Examples of acids and bases used include acids such as nitric acid and organic acids that volatilize during calcination, and bases such as ammonia, ethanolamine, and propylamine; however, sulfuric acid and hydroxide that remain and become active components of the catalyst Potassium and the like are also suitable. Here, if the amount of salt generated by neutralization is too small, a strong gel may not be obtained.
It is preferable to adjust the amount of acid and base added so that the amount is 0.01 g or more, preferably 0.03 g or more per 1 g of SiO ₂ . There is no particular limit to the silica concentration during neutralization, but from the viewpoint of production efficiency, 3 to 30% SiO ₂ is preferable. The heating conditions after neutralization are determined depending on the desired catalyst form, since the pore volume and bulk density of the catalyst can be controlled by changing them. For example, if it is desired to increase the pore volume and therefore decrease the bulk density, the heating temperature may be increased and the heating time may be increased. However, the heating temperature is preferably 60°C or higher, preferably 70°C or higher. Temperatures below 60°C are not practical because it takes a very long time to obtain a stable gel. The higher the temperature, the shorter the heating time may be.
At a temperature of 60°C, heating for at least 2 hours is required. As described above, the silica sol is made acidic, neutralized to a neutral pH of 6 to 11, and then heated to obtain a silica hydrogel, which is then used as a silica source for the catalyst, to form the desired pore size. Although a catalyst having a large volume and bulk density and a large specific surface area can be obtained, the silica hydrogel obtained as described above may be mixed with the original silica sol as a silica source for the catalyst. By using a mixture of silica hydrogel and silica sol, or by using a silica hydrogel obtained by mixing silica hydrogel and silica sol, adding an acid and then adding a base to neutralize the mixture, and repeating this operation several times. It is possible to further control the bulk density of the catalyst and improve wear resistance. The method for producing a catalyst according to the present invention includes preparing a mixed slurry of the silica hydrogel as described above, a vanadium compound, a potassium compound, and a sulfuric acid compound, and then
It consists of spray drying and firing. Vanadium compounds used in the present invention include those that are soluble in water and turn into vanadium oxide when fired in air, such as ammonium metavanadate, vanadyl sulfate (vanadium oxysulfate), vanadium acetate, vanadium oxalate, and oxalic acid. Examples include ammonium vanadium and vanadium oxyhalide. Potassium compounds used in the present invention include potassium hydroxide, potassium sulfate, potassium chloride, potassium nitrate, potassium oxyhalide, potassium thiosulfate, potassium nitrite, potassium sulfite, potassium hydrogen sulfite, potassium hydrogen sulfate, and potassium sulfate. Potassium acid, potassium hydrogen oxalate, and the like can be mentioned, but among these, potassium sulfate, whose residual component after firing becomes the active component, is particularly suitable. As the sulfuric acid compound, sulfuric acid, ammonium sulfate, etc. can be used. The blending amounts of these silica hydrogels, vanadium compounds, potassium compounds, and sulfuric compounds are such that the silica content in the catalyst is 45 to 90 wt% as SiO ₂ ,
Preferably, the content of active ingredients is 65-85wt%
55-10wt as the sum _{of V2O5} , _K2SO4 , _{and SO3}
%, preferably 35 to 15 wt%. If the content of the active component in the catalyst is less than 10 wt%, the activity of the catalyst will be low, which is not preferable. In this case, raising the reaction temperature in order to increase the activity is not preferable because it promotes a decrease in selectivity and deterioration of the activity. On the other hand, the content of active ingredients is 55wt
%, the bulk density of the catalyst increases.
This is undesirable because the specific surface area decreases and the activity and fluidity decrease due to crystallization of the active ingredient. Further, in the catalyst according to the present invention, the content ratio of each active component is such that the SO ₃ /K ₂ O molar ratio is 2.0 ± 0.4, preferably 2.0 ± 0.2, and the K ₂ O / V ₂ O ₅ molar ratio is 4.0.
The range is selected to be ±1.0, preferably 4.0±0.4. In the method for producing a catalyst according to the present invention, when producing a mixed slurry, the mixing order of the silica hydrogel and each active component can be changed arbitrarily, and two or more components may be dissolved together in water. Alternatively, the active ingredient may be dissolved by the water retained in the silica hydrogel. However, the amount of water in the mixed slurry is preferably 50 to 95 wt%. The mixed slurry obtained as described above is concentrated as required by a conventional method to adjust the concentration to an appropriate concentration, and then spray-dried to obtain fine spherical particles. As the spray drying method, a known method can be adopted, and the temperature at the time of drying (the outlet temperature of the dryer)
Although there is no particular restriction on the temperature, a temperature of 100 to 200°C is suitable.
Regarding spraying, the weight average particle diameter of the obtained spherical fine particles is 60 ± 20 μm, and the particle size distribution is 44 μm or less.
It is preferable to set spray conditions so that the amount is ~40 wt%. The obtained spherical particles have a density of 300-600 in air.
℃, preferably at a temperature of 400-550℃. By the production method of the present invention as described above, a catalyst having the following properties can be obtained. Particle shape Solid spherical Bulk density (g/cc) 0.7±0.3 Specific surface area (m ² /g) 150±100 Pore volume (cc/g) 0.2-0.6 Wear rate (wt%/15hr) Weight average particles of 3 or less Diameter (μm) 60±20 Particle size distribution 44 μm or less (%) 10-40 Distribution of active components within catalyst particles Uniform Distribution of active component content between catalyst particles Uniform In the above properties, the wear resistance of the catalyst is is mainly correlated with pore volume, but the wear rate of the catalyst obtained by the present invention is 3wt%/15hr or less,
This shows that the wear resistance is superior to that of conventional post-deposition or impregnation catalysts with the same pore volume. Such excellent wear resistance reduces the decrease in specific surface area when used in a reaction, thereby suppressing a decrease in catalyst activity. In addition, since the catalyst according to the present invention has a uniform distribution of active components within catalyst particles and a uniform content distribution of active components between catalyst particles, when used in a reaction, low melting point components will not melt due to local heat generation on the catalyst. , it does not reduce the specific surface area of the catalyst and cause a decrease in activity. The excellent heat resistance of the catalyst according to the present invention means that the rate of decrease in specific surface area is small even after heat treatment at 600°C for 2 hours in a Matsufuru furnace, and the activity decreases even after long-term use in a fluidized bed. This is demonstrated by the fact that the ratio is significantly lower than that of conventional catalysts. <Example> The present invention will be explained in more detail with reference to Examples below. Example 1 (Preparation of Na-free silica sol) As a silica sol, the average particle diameter of colloidal silica was 5 nm, and sodium as a stabilizer was Na ₂ O/
Cataloid SI− containing 0.035 as SiO ₂ (weight ratio)
550 (manufactured by Catalysts Kasei Kogyo Co., Ltd.) (50 kg) was diluted to a concentration of approximately 10% by adding ion-exchanged water. This solution was packed in a column in advance, and the 7 cation exchange resin (Diaion SK-1B, Mitsubishi Chemical Industries, Ltd.) layer was added to the column at a superficial velocity.
Passage was carried out at SV = 12 hr ^-1 to obtain 93 kg of Na-free silica sol. Table 1 shows the properties of this Na-free silica sol.
Moreover, this sol did not gel for more than one month at room temperature.

[Table] (Preparation of silica hydrogel) The previously obtained Na-free silica sol was placed in a stainless steel container equipped with a stirrer and a steam jacket, and 1.46 kg of 63% nitric acid solution was mixed therein.
After setting the pH to 0.8, add 15% ammonia water.
The pH was adjusted to 8.5. Formation of silica hydrogel was observed midway through the addition of ammonia water. Steam was passed through the jacket and the silica hydrogel was heated to a constant temperature of 80°C. A portion of the resulting silica hydrogel was collected at regular intervals and used as a silica source for catalyst preparation. (Preparation of mixed slurry to firing) 0.23 kg of potassium sulfate crystals were added to 1.5 kg of heated ion-exchanged water, and then thoroughly stirred and dissolved to prepare a potassium sulfate solution. On the other hand, ammonium sulfate
0.17Kg was dissolved in 0.4Kg of ion-exchanged water to obtain an ammonium sulfate solution. 10.9 kg of silica hydrogel (SiO ₂ concentration 10.1% by weight) collected after heating for 5 hours in the preparation of the silica hydrogel described above was placed in a stainless steel container equipped with a steam jacket, and a vanadyl sulfate solution (V ₂ 19.9% as _O5 ) 0.30
Kg, the previously dissolved potassium sulfate solution, and ammonium sulfate solution were added and mixed well, and at the same time steam was passed through the jacket to heat and concentrate. The obtained mixed slurry contains solid components (V ₂ O ₅ , K ₂ SO ₄ , SO ₃
and _SiO2 ) at 25°C.
The pH was 3.5. This slurry was treated with a homogenizer to disperse the gel well, and then spray-dried with a spray dryer at a drying temperature of 150°C to obtain a powder.
The powder was calcined in air at 500° C. for 2 hours to prepare a catalyst with an average particle size of 60 μm and 27 wt % of particles with a particle size of 44 μm or less. Here, this catalyst was designated as catalyst D. Using the silica hydrogel sampled at regular intervals during the preparation of silica hydrogel, catalysts were prepared in exactly the same manner as catalyst D, and catalysts A, B,
I got C and E. Table 2 shows the heating time of the silica hydrogel used in these catalysts and the properties of the catalyst. The specific surface area and pore volume of the catalyst were measured by the BET method, the bulk density by the graduated cylinder method, and the wear rate by the equipment method described in British Patent No. 737429 (ACC).

[Table] Example 2 Low Na silica sol (trade name Cataloid S-20L,
Catalysts & Chemicals Co., Ltd.) was diluted with ion-exchanged water.
63% nitric acid 2.1 to 72Kg of silica sol with _SiO2 concentration 13.0%
After mixing Kg to adjust the pH to 0.68, 15% aqueous ammonia was added to adjust the pH to 9.4. Gel formation was observed immediately after pH adjustment. then gel
It was heated for 6 hours to maintain a constant temperature of 90°C. A catalyst was prepared using 9.2 kg of this gel in the same manner as in Example 1 to obtain catalyst F. The characteristics of the obtained catalyst F were as follows. Bulk density g/cc 0.55 Specific surface area m ² /g 90 Pore volume cc/g 0.58 Wear rate %/15hrs 2.6 Example 3 The amount of ammonia water used for neutralization was adjusted when preparing the silica hydrogel of Example 1. PH 6.9,
After changing to 10.6 and 11.7, heat at 80℃ for 5 hours to neutralize.
Three types of silica hydrogels with different pH values were prepared.
Catalysts were prepared using this hydrogel in the same manner as in Example 1 to obtain catalysts G and H of Examples of the present invention and catalysts of Comparative Examples. Table 3 shows the characteristics of these catalysts.
Describe it in Note that, for convenience, the characteristics of catalyst D are also described.

[Table] Example 4 A catalyst was prepared in the same manner as in Example 1, except that the silica source was a mixture of the silica hydrogel prepared after heating for 5 hours and Na-free silica sol.
The mixing ratio is the ratio of silica in gel to silica in sol.
Catalysts J, K, L, and M were obtained using catalysts of 30/70, 50/50, 60/40, and 75/25. The properties of these catalysts are listed in Table 4. For convenience, the characteristics of catalyst D will also be described.

[Table] Example 5 Silica hydrogel after 9 hours of heating in Example 1
Na-free silica sol to 69.3Kg (7.0Kg as SiO ₂ )
1.8Kg of 63% nitric acid was added to the slurry containing 28.6Kg (3.0Kg as _SiO2 ) to adjust the pH to 0.8. Catalyst N was prepared in the same manner as in Example 1 using the silica hydrogel obtained by neutralizing this with 15% aqueous ammonia to adjust the pH to 6.9 and heating at 80° C. for 9 hours. Similarly, silica hydrogel was desorbed.
The method of mixing Na-silica sol and then gelling it again was repeated three times (in each case, the ratio of SiO ₂ in the gel / SiO ₂ in the sol was 70/30) to obtain a silica hydrogel.
Catalyst O was prepared in the same manner as in Example 1 using this silica hydrogel. Table 5 shows the characteristics of catalysts N and O, and for convenience, the characteristics of catalyst E are also shown.

[Table] Comparative example 1 Sodium silicate (Dokai Chemical Industry Co., Ltd., No. 3 sodium silicate, SiO ₂ concentration 24.0%, SiO ₂ /Na ₂ O molar ratio 3.1)
was diluted with ion-exchanged water to a concentration of 5.7% SiO ₂ , and then passed through a cation-exchange resin layer to remove sodium ions, yielding 150 kg of silicic acid solution with an SiO ₂ concentration of 5.4% and a pH of 2.4. Put 126 kg of ion-exchanged water and 22.3 kg of sodium silicate into a stainless steel container and mix well to prepare a dilute sodium silicate solution.While heating this at 50℃, add the entire amount of the silicate solution obtained earlier. Added over 1.8 hours. After the addition was completed, the mixture was further heated for 1 hour to obtain a silica sol. This silica sol was passed through a cation exchange resin layer to obtain the deNa-reduced, small-particle silica sol shown in Table 1.
Catalyst P was prepared in the same manner as in Example 1 using 165 kg of this. The characteristics of the obtained catalyst P were as follows. Bulk density g/cc 0.64 Specific surface area m ² /g 26 Pore volume cc/g 0.17 Wear rate % 21.6 Moreover, the catalyst particles were not spherical but doughnut-shaped. After concentrating the silica sol, an attempt was made to obtain a Na-free silica sol, but when the silica sol was concentrated under reduced pressure, the viscosity increased at a SiO ₂ concentration of about 11%, and further concentration was not possible. Furthermore, when the concentrated solution was poured into the cation exchange resin layer, it instantly became a gel, making it impossible to remove sodium. Moreover, the silica sol used for preparing the catalyst gelled in 6 days when left to stand. Comparative Example 2 1N sulfuric acid was added to 250 kg of a sodium silicate solution diluted with ion-exchanged water to 4.0% SiO ₂ with stirring over 10 minutes to adjust the pH to 6.8. Initially, the liquid was in the form of a sol, but after a few minutes, the entire liquid became a gel. After aging this at 80°C for 30 minutes, it was dehydrated using a flat plate strainer and at the same time washed with 5000 ion exchanged water to obtain a SiO ₂ concentration of 5.2%, a Na ₂ O/SiO ₂ weight ratio of 0.009,
154 kg of hydrogel with a gel constituent particle size of 3.1 nm was obtained. Using this hydrogel, vanadyl sulfate, potassium sulfate, and ammonium sulfate solutions were mixed in the same manner as in Example 1, and then the gel was dispersed using a homogenizer. After that, heating and concentration was performed, but the solid content concentration was 7.2%.
It became a viscous liquid and could not be concentrated any further. This slurry was spray dried and fired to obtain catalyst Q. The characteristics of this catalyst Q were as follows. Bulk density g/cc 0.47 Specific surface area m ² /g 67 Pore volume cc/g 0.63 Attrition rate % 10 In addition, the catalyst had low sphericity and the surface was particles lacking smoothness. Comparative Example 3 The hydrogel obtained in Comparative Example 2 was used as SiO ₂
After concentrating to 6.9% and performing homogenizer treatment, spray drying was performed with only silica hydrogel without mixing with the active component of the catalyst to obtain a powder, and the powder was calcined at 500 ° C for 2 hours to obtain silica powder. Ta.
The properties of this powder were as follows. Bulk density g/cc 0.28 Specific surface area m ² /g 720 Pore volume cc/g 1.01 Average particle size μm 67 74 kg of this powder was placed in a vacuum impregnation equipment at -600 mmHg
After adding a mixed solution of vanadyl sulfate, potassium sulfate, and ammonium sulfate prepared in the same manner as in Example 1 under reduced pressure (160 mmHg) and impregnating and supporting the solution,
It was dried at ℃ for 8 hours and calcined at 500 ℃ for 2 hours to obtain catalyst R. The characteristics of this catalyst R were as follows. Bulk density g/cc 0.58 Specific surface area m ² /g 300 Pore volume cc/g 0.50 Wear rate % 8.2 Moreover, the catalyst particles had low sphericity and low surface smoothness. Comparative Example 4 Cataloid SI-80p, a silica sol with a large average particle size of colloidal silica (average particle size 80.2n)
A sodium-free silica sol was obtained in the same manner as in Example 1 using (m). This was hydrogel prepared and catalyzed under the same conditions as Catalyst D to obtain Catalyst S. The characteristics of the obtained catalyst S were as follows. Bulk density g/cc 0.91 Specific surface area ^m2 /g 19 Pore volume cc/g 0.20 Wear rate %/15hrs 24.7 (Examples 1 to 5 (catalysts A to H, K to O), Comparative example 1
- 4 (Activity evaluation of catalysts I, P - S) and commercially available catalysts) The following activity evaluations () -
I did (). The results are shown in Table 6. The commercially available catalyst is the only commercially available catalyst (US
DAVISON) was used. This commercially available catalyst had the following properties. Bulk density g/cc 0.54 Specific surface area m ² /g 358 Pore volume cc/g 0.57 Wear rate % 11.1 Particle shape: Shape of crushed product Active ingredient content between particles: Heterogeneous fluidity: Poor () Fixed bed activity Evaluation Sum of reaction rate constants determined from the yields of naphthoquinone and phthalic anhydride from naphthalene in fixed bed reaction operation (temperature 355°C, naphthalene feed rate 1 ml/hr, air feed rate 7.5 Nl/hr, catalyst amount 5 g) (k ₁ +k ₂ ) (k ₁ ; naphthalene→naphthoquinone; k ₂ ; naphthalene→phthalic anhydride). () Activity reduction rate in 48-hour fluidized bed test Fluidized bed reaction operation (temperature 355°C, naphthalene feed rate 105 g/hr, air feed rate 960 Nl/hr,
The sum of the reaction rates (k ₁ + k ₂ ) was determined in the same manner as in the fixed bed evaluation using a catalyst amount of 3.75 kg), and the rate of decrease after 48 hours was used for evaluation. () Heat deterioration resistance The catalyst was placed in a Matsufuru furnace with a thickness of 5 mm, and
The rate of decrease in specific surface area after heat treatment at ℃ for 2 hours was measured and defined as heat deterioration resistance.

[Table] (Relationship between catalyst pore volume and wear rate) The logarithm of the wear rate is plotted against the pore volume for catalysts A to S of Examples 1 to 5 and Comparative Examples 1 to 4 and commercially available catalysts. Figure 1 was obtained. From FIG. 1, the wear rate of the catalyst according to the present invention has a correlation with the pore volume, and when silica hydrogel is used as the silica source (indicated by a solid line in the figure),
In the case of using a mixture of silica hydrogel and silica sol (indicated by a dotted line in the figure), the difference between the heating time and the pore volume of silica hydrogel and the pore volume of silica hydrogel/silica sol lies on a different straight line. It can be seen that there is also a correlation between the mixing ratio and the pore volume. On the other hand, the characteristic values of the catalyst of the comparative example do not show the same correlation as the catalyst of the present invention. Therefore, it can be seen that according to the present invention, a catalyst having desired characteristics can be obtained by controlling the heating time of the silica hydrogel, the mixing ratio of the silica hydrogel and the silica sol, etc. (Particle shape of catalyst) The surfaces of catalysts A to S of Examples 1 to 5 and Comparative Examples 1 to 4 and commercially available catalysts were observed using a microscope, and all of the catalysts of Examples of the present invention had a solid shape. FIG. 2 shows micrographs of catalyst D of Example 1, catalyst Q of Comparative Example 2, and a commercially available catalyst. <Effects> The catalyst of the present invention has high activity, which conventional catalysts could not satisfy, in the reaction of producing phthalic anhydride through gas phase catalytic oxidation of naphthalene using a fluidized bed.
Satisfies heat deterioration resistance and high wear resistance at the same time. Here, the catalyst according to the present invention has a higher specific surface area and improved wear resistance than a catalyst manufactured using a method that simply uses silica sol as a silica source. Furthermore, according to the present invention, it is possible to arbitrarily control the specific surface area, pore volume, and bulk density.
Catalysts can be produced that are compatible with a wide range of reaction conditions.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing the relationship between pore volume and wear rate of Examples, Comparative Examples, and commercially available catalysts. Figure 2a
- c are drawing-substituting photographs (microscopic photographs) representing the particle structures of Examples, Comparative Examples, and commercially available catalysts, respectively.

Claims (1)

[Claims] 1. A method for producing a fluidized catalyst for gas phase catalytic oxidation of naphthalene by mixing a silica source, a vanadium compound, a potassium compound and a sulfuric acid compound, followed by spray drying and sintering, wherein the silica source has an average particle size of 4 to 50 nm. After adding acid to the silica sol containing colloidal silica to make it acidic,
A method for producing a fluidized catalyst for gas phase catalytic oxidation of naphthalene, which comprises using a silica hydrogel obtained by adjusting the pH of the silica sol to 6 to 11 by adding a base and heating.