JPH0312937B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a catalyst composition. More specifically, the present invention relates to a method for producing a catalyst composition suitable for producing maleic anhydride by oxidizing n-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 4 carbon atoms, especially n-butane, n-butene, butadiene, etc. Are known. (US Pat. No. 3,293,268) It has also been reported that crystalline vanadyl phosphate ((VO) ₂ P ₂ O ₇ ) is effective as an active ingredient in this catalyst. [E.Bordes, P.Courtine, Journal of Catalysis (E.Bordes, P.Courtine, J.Catal.) 57 , 236
(1979)] The crystalline phase of this compound can be identified by its characteristic X-ray diffraction pattern as shown in Table 1 below.

[Table] According to the findings of the present inventors, the crystal phase of this compound is considerably larger than that of amorphous composite oxide catalysts based on conventional production methods as a gas phase oxidation catalyst for n-butane and n-butenes. It is highly active, and has the characteristic that the reaction proceeds even in a low temperature range of about 100°C, especially for the oxidation of n-butane. Therefore, the above table-1
It is preferable in terms of the process to use a catalytic active species having the X-ray diffraction peak shown in .The catalyst produced in the present invention also takes the form of an active species having the above peak in the reaction system. On the other hand, the reaction of producing maleic anhydride by gas phase oxidation from a hydrocarbon with a carbon number of 4 is a strongly exothermic reaction including complete oxidation (i.e., production of carbon monoxide and carbon dioxide) as a side reaction, and is energy efficient. It has been thought that the fluidized bed catalytic oxidation reaction is suitable because of the low explosive limit concentration of raw material hydrocarbons in air. Catalysts developed for this purpose have been prepared, for example, by spraying and drying a mixture containing vanadyl oxalate solution, phosphoric acid, silica sol, and appropriate activity-promoting components. (British Patent No. 1285075, etc.) The catalyst obtained in this way contains n-butene,
Although it is effective in oxidizing butadiene, etc., it is not sufficiently active for oxidizing n-butane, and generally requires a reaction temperature of 500°C or higher. Several reports have also been made regarding fluidized bed catalysts for the oxidation of n-butane. For example, in JP-A-49-126587, a pentavalent vanadium compound is brought into contact with a trivalent phosphorus compound to form a composite oxide containing phosphorus and vanadium, which is then ground into a fine powder. , an example of application to a flow reaction is described. Although this method makes it possible to extract crystalline active ingredients and improve the activity, it is not sufficient in terms of the strength and fluidity of the catalyst. The possibility of such a crushed fluidized bed reaction using fine powder of catalytically active components was further pointed out in JP-A-50-8788, JP-A-56-33038, etc.;
No. 56-65635 also proposes the possibility of producing a fluidized bed catalyst by depositing a composite oxide containing phosphorus and vanadium on a carrier. As a result of extensive research aimed at developing a catalyst for gas-phase oxidation of n-butane in a fluidized bed, the present inventors discovered that a special crystalline oxide containing vanadium and phosphorus as the first component, a second We discovered that it is possible to produce a catalyst with excellent strength and fluidity by preparing a slurry by mixing an aqueous solution containing vanadium and phosphorus as components and silica sol as a third component, and spray drying the slurry.
This completes the present invention. The present invention will be explained in detail below. In the present invention, a crystalline composite oxide containing tetravalent vanadium and pentavalent phosphorus, which exhibits a specific X-ray diffraction peak, is used as the first component. The X-ray diffraction peaks and intensity ratios are as follows.

[Table] In addition to the above peaks, weak peaks with an intensity ratio of about 10 to 20 are seen at 18.5°, 21.8°, and 32.2°. The crystalline composite oxide as the first component is known, and several manufacturing methods have been reported. For example, a solution containing tetravalent vanadium ions is prepared by reducing pentavalent vanadium such as vanadium pentoxide in a non-oxidizing acidic solution such as a hydrochloric acid solution in combination with a reducing agent such as oxalic acid. , a method of reacting with a pentavalent phosphorus compound, such as phosphoric acid, and then adding water to precipitate the generated soluble vanadium-phosphorus complex (Japanese Patent Application Laid-open No. 51-95990); A method of obtaining crystals by reacting a pentavalent vanadium compound and phosphoric acid in an aqueous medium in the presence of a reducing agent such as hydrazine hydrochloride or hydroxylamine hydrochloride, and concentrating or evaporating to dryness (Japanese Patent Laid-Open No. 56-45815), or a method in which vanadium pentoxide is reduced in an organic medium such as ethanol, isopropanol, or glycerol, reacted with phosphoric anhydride, and azeotropically dehydrated with a solvent such as benzene to precipitate crystals (U.S. Patent No. 4283288
No.) etc. are known. By any of the above methods, a crystalline composite oxide exhibiting main X-ray diffraction peaks as shown in Table 2 can be obtained. In consideration of crystal purity, operability, waste disposal, etc., method is considered preferable, but is not particularly limited. The composite oxide containing vanadium and phosphorus, which is the first component, can be roughly represented by the composition formula (V ₂ O ₄ )(P ₂ O ₅ )(2H ₂ O). Therefore, the ratio of phosphorus to vanadium is theoretically 1.0 in P/V atomic ratio, so vanadium compounds and phosphorus compounds are
It is preferable to carry out the reaction within a range of P/V atomic ratio of 0.8 to 1.25. 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. Such metal ions include iron, chromium, aluminum,
Examples include ions such as titanium, cobalt, and magnesium. When such a composite oxide partially substituted with metal ions is used as a catalyst, it can significantly improve the activity and stabilize the activity. The substitution ratio is selected in the range of 0.005 to 0.4, more preferably 0.01 to 0.2 mole of metal per mole of vanadium element. A method for introducing such other metal ions into a composite oxide is to introduce these metal ions into an inorganic salt such as hydrochloride, sulfate, nitrate, carbonate, or oxalate at the stage of manufacturing the composite oxide. An example of this method is to add it in the form of an organic salt such as. 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 the 2θ° is within ±0.2°. The first component is added at a stage before preparing the slurry.
It is best to pulverize it in advance, for example, 10μ.
Thereafter, the particles are pulverized to a particle size of preferably 5 μ or less (which can be measured by Coulter Counter method, etc.). For such treatment, machines well known to those skilled in the art, such as hammer mills, jet mills, colloid mills, sand grinders, etc., can be used, and either wet or dry methods may be employed. The aqueous solution containing vanadium and phosphorus as the second component in the present invention usually contains substantially tetravalent vanadium and pentavalent phosphorus, and it is preferable that at least a part of them be present as vanadyl phosphate. This 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 contributes to improving the fluidity and strength of the fluidized catalyst. Although the method for producing such an aqueous 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 a pentavalent phosphorus compound, for example, phosphoric acid. The atomic ratio of phosphorus element to vanadium element in the aqueous solution is preferably in the range of 0.5 to 10. Generally, aqueous solutions containing vanadyl phosphate are unstable and it may be difficult to keep them stable for long periods of time, so oxalic acid can be present to stabilize the aqueous solution. The amount is the molar ratio of oxalic acid to vanadium element.
It is 1.2 or less, preferably in the range of 0.2 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 1.2 or less can be said to be a range in which vanadyl oxalate is not formed. Specific examples of methods for producing aqueous solutions include the following methods. First, vanadium pentoxide is added to an aqueous solution containing phosphoric acid and oxalic acid at a molar ratio of oxalic acid to elemental vanadium of 1.7 or less and preferably 0.7 or more to form vanadium phosphate and oxalic acid. This is a method of preparing an aqueous solution containing
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 completion of the reduction, 1.2 moles or less of oxalic acid will exist based on the vanadium element. Second, a reducing agent other than oxalic acid, preferably hydrazine hydrate, is added to the acidic aqueous solution containing phosphoric acid.
hydrazine or hydroxylamine hydrochloride,
Add one or a mixture of two or more selected from inorganic reducing agents such as phosphates and organic reducing agents such as lactic acid, and then reduce by adding vanadium pentoxide to obtain a homogeneous aqueous solution containing vanadyl phosphate. obtain.
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, when left to stand, a crystalline solid that gives a characteristic X-ray diffraction spectrum as shown in Table 3 below precipitates.

[Table] Such precipitation of crystalline solids is not preferable from the purpose of the present invention, and when it is necessary to keep the aqueous solution stable for a long time, it is preferable to add oxalic acid. The aqueous solution containing vanadium and phosphorus mentioned above may contain alcohol, ketone,
An organic solvent such as ether may be used in combination. In the present invention, a catalyst composition is produced by mixing the above-described first and second components and silica sol as a third component to prepare a slurry, and spray drying the slurry. Silica sol is 10-50 in advance
It is prepared as a concentration of % by weight, mixed with the first component and the second component, and stirred to form a uniform slurry. The ratio of the first component, second component and third component is dry weight %, first component: second component = 20:80 ~
80:20 2nd component: 3rd component = 50:50~90:10
The first component: the third component is selected within the range of 50:50 to 90:10. Note that the dry weight of the second component can be calculated by assuming vanadium and phosphorus as V ₂ O ₄ and P ₂ O ₅ . If the amounts of the first component and the second component are too small relative to the third component, the catalyst strength will improve, but
A decrease in activity is observed. Also, the amount of the second component is
When the content of the first component is below the above range, the catalyst strength tends to decrease. The slurry thus obtained can be spray-dried to yield a catalyst composition with excellent fluidity and strength. It is usually best to adjust the air volume and liquid supply amount appropriately and set the gas temperature in the drying area in the range of 120 to 350°C, and the inlet temperature of the drying gas at this time is usually 200°C. ~350℃. In addition, the amount of liquid supplied and the rotational speed of the disk are adjusted so that the average diameter of the catalyst particles after spray drying is in the range of about 30 to 100 microns. A more preferable range of average particle diameter is 40 to 70
It is micron. The catalyst composition obtained as described above has a 400%
It is more preferable to use it after firing at a temperature in the range of 600°C to 600°C in terms of catalytic activity. At this time, it is preferable to carry out the calcination in the presence of air containing butane or butenes or in an inert gas atmosphere such as argon or nitrogen. change into something. The catalyst composition obtained as described above has excellent fluidity, strength, and activity, and contains hydrocarbons having 4 carbon atoms,
In particular, it is suitably used as a catalyst for producing maleic anhydride by oxidizing n-butane. The present invention will be explained below using examples. Example 1 (Synthesis of first component A-1) 9.22 kg of phosphoric acid (85%, special reagent grade), 1.30 kg of hydrazine hydrochloride, 550 g of hydrazine monohydrochloride were added to 40 g of demineralized water
After dissolving in water, it was heated. After raising the temperature to 75°C, 7.28 kg of vanadium pentoxide was added little by little with stirring, and after the entire amount was added, the mixture was further boiled for 1 hour to complete the reduction.
After concentrating this liquid under reduced pressure using a rotary evaporator to about 1/2 of the liquid volume, it was placed in an evaporating dish and heated to 170°C.
It was evaporated to dryness. After confirming that a constant weight has been reached, coarsely crush the
The solid was boiled and washed with water to completely remove residual hydrochloric acid. After washing with water, dry again in the dryer at 170℃,
The first component (A-1) having an atomic ratio of P/V=1 was obtained by fine grinding in a hammer mill. The average particle size was 6.5μ. The X-ray diffraction spectrum of this product matched that shown in Table 2. Example 2 (Synthesis of first component A-2) 691.8 g of phosphoric acid, 104.7 g of hydrazine hydrochloride, and 30.0 g of hydrazine monohydrochloride were dissolved in 1.9 g of demineralized water and heated. After heating to 75℃, vanadium pentoxide 518.4
g was added little by little with stirring, and after the entire amount was added, the mixture was further boiled for 1 hour to complete the reduction. The mixture was allowed to cool, and then a solution of 81.0 g of ferric chloride (FeCl ₃ .6H ₂ O) dissolved in 100 g of water was added. This liquid was directly concentrated to about 2/3 of its liquid volume, and then evaporated to dryness in an evaporating dish at a temperature of 170°C. Confirm that a constant weight has been reached, and proceed with Example 1.
A first component (A-2) having an atomic ratio of P/V/Fe=1/0.9/0.1 was obtained through the same treatment. The X-ray diffraction spectrum of this product was within a range of ±0.2° from the positions of each peak shown in Table 2. Examples 3 to 7 (Synthesis of first components A-3 to 7) Chromium chloride, aluminum chloride, titanium oxalate, cobalt chloride, and magnesium chloride were used instead of ferric chloride, which is the promoting component in Example 2. Oxides A-3 to A-7 having the element ratios shown in Table 3 below were manufactured according to the method of Example 2. Note that the amount of raw materials used in Example 2 was also adjusted according to the change in the atomic ratio. Note that A-1 and A-2 are also listed in Table-3.

[Table] Example 8 (Synthesis of second component B-1) 1635 g of phosphoric acid (85% solution) and 1500 g of oxalic acid were dissolved in 500 ml of demineralized water, and the solution was heated to 80°C. Next, 1082 g of vanadium pentoxide was added little by little and dissolved. The P/V atomic ratio of the solution is 1.2
The resulting solution was a viscous blue homogeneous solution. By slightly concentrating, the converted oxide concentration of [V ₂ O ₄ +P ₂ O ₅ ] was set to 45.0% by weight. The molar ratio of residual oxalic acid to elemental vanadium is 0.5 since 1 mole of oxalic acid was used per mole of vanadium pentoxide in the reduction reaction. Example 9 (Synthesis of second component B-2) A blue uniform solution B-2 with a converted oxide concentration of 45.0% by weight was obtained in the same manner as in Example 8 except that the amount of oxalic acid used was changed to 1125 g. Ta. In this solution, P/V=1.2 and the molar ratio of residual oxalic acid to elemental vanadium is 0.25. Example 10 Example 8 except that the amount of phosphoric acid used was 2250g
In the same manner as above, a solution B-3 having a converted oxide concentration of 45.0% by weight was obtained. Example 11 (Production of fluidized catalyst by spray drying) Crystalline active ingredient fine powder obtained in Examples 1 to 7 (first component), blue uniform solution obtained in Examples 8 to 10 (second component), and silica sol (Third component) in various proportions, thoroughly and uniformly mixed with a homogenizer, and then spray-dried to form a fluidized catalyst (Catalyst No. 1 to
8) was manufactured. The results are summarized and shown in Table 4. In the same table, the mechanical strength of the catalyst is determined by colliding the catalyst particles against a SUS metal plate in a fluidized state and measuring the amount of crushing loss within 2 hours for those fired at 500℃ for 2 hours under a nitrogen stream. It is displayed as an indicator. This value becomes smaller for stronger catalysts.

[Table] ** Silica sol slurry weight
Example 12 (Reaction example) A fluidized bed catalyst obtained by spray drying was heated at 500°C for 2
It was calcined for an hour under a nitrogen stream, and then the particle size portion of 25-88μ was sieved. A catalyst amount of 20 ml was taken, and an air mixed gas having an n-butane concentration of 4 mol % was passed through the reactor at a flow rate of GHSV500 to carry out the reaction. The product was taken up in water, and the yield was determined by potentiometric titration and compositional analysis of the waste gas. The results are shown in Table-5.

[Table] Example 13 (Reaction Example) Using the catalyst obtained in Example 11, the influence of reaction conditions was investigated. The reaction was carried out in the same manner as in Example 12, except that GHSV was kept constant at 500 and only the n-butane concentration was changed, and the reaction results were investigated. The results are shown in Table-6.

[Table] Example 14 (Synthesis of second component B-4) Mix 1.33 kg of V ₂ O ₅ , 0.844 kg of 85% phosphoric acid, 0.660 kg of phosphorous acid (purity 97.6%) and 4.5 kg of water to make a slurry, The mixture was boiled and heated under reflux for 10 hours while a small amount of nitrogen was blown in and stirred. The entire amount of V ₂ O ₅ was dissolved to obtain a uniform blue solution, which was diluted to 10 to prepare a second component solution (B-4). The equivalent oxide concentration of this product is approximately 18.5% by weight. The P/V of this solution was 1.05, and it was stored in a cool, dark place. In order to control the amount of phosphorus during use, a desired amount of phosphoric acid is added. Example 15 (Production of fluidized catalyst by spray drying) 1.12 kg of the first component obtained in Example 1, 3.38 kg of the aqueous solution of the second component obtained in Example 14, and 2.22 Kg of 20% silica sol solution as the third component. and 77 g of 85% phosphoric acid were mixed, and then mixed and stirred using a homogenizer for 60 minutes to obtain a uniform gel slurry. The oxide concentration was 30% by weight. A fluidized catalyst (No. 9) was produced by spray drying this slurry,
After fluidized firing at 500℃ for 2 hours under a nitrogen stream,
Particles of 25-88μ were sieved and used for the reaction. Example 16 (Production of fluidized catalyst by spray drying) A catalyst was produced in the same manner as in Example 15 except that the amount of phosphoric acid was changed to 130 g (Catalyst No. 10) Example 17 (Reaction example) The amount of catalyst was 20 ml. Then, an air mixed gas having an n-butane concentration of 4 mol % was passed through the reactor at a flow rate of GHSV500 to perform a fluid reaction. As in Example 12, the main product was absorbed in water, and the yield was determined by potentiometric titration and compositional analysis of the waste gas. The results are shown in Table-7.

【table】

Claims (1)

[Claims] 1. A crystalline composite oxide containing vanadium and phosphorus as a first component and exhibiting the following characteristic X-ray diffraction peaks, an aqueous solution containing vanadium and phosphorus as a second component, and A method for producing a catalyst composition suitable for the production of maleic anhydride by the oxidation of n-butane, characterized in that a slurry is prepared by mixing silica sol as three components and spray-dried. 2θ° (±0.2°) (Anticathode Cu-Kα) 15.7 19.6 24.2 27.1 28.8 30.4 2 The method according to claim 1, characterized in that the second component is an aqueous solution containing vanadyl phosphate. 3 The mixing ratio of the first component, second component, and third component is dry weight %, first component: second component = 20:80 to 80:20, second component: third component = 50:50 to 90: 10 Method 4 according to claim 1, characterized in that the ratio of first component: third component is in the range of 50:50 to 90:10. Vanadium as the first component is substantially tetravalent. 5. The method according to claim 1, characterized in that the second component vanadium is substantially tetravalent.