JPH0479699B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a catalyst composition suitable for fluidized bed reactions. More specifically, carbon number 4
The present invention relates to a method for producing a catalyst suitable for producing maleic anhydride from an aliphatic hydrocarbon by a gas phase oxidation reaction in a fluidized bed. introducing a substantially pentavalent vanadium-containing compound, in particular vanadium pentoxide, into an organic solvent capable of reducing the pentavalent vanadium compound to its tetravalent state as an active component of the catalyst for this reaction and reducing it by heating;
It is known that a crystalline precursor obtained by reacting this with orthophosphoric acid or a fired product thereof is effective. This crystalline precursor and the vanadium-phosphorus composite oxide obtained by sintering it have the characteristic X shown in Table 1 and Table 2, respectively.
Showing a line diffraction pattern (U.S. Pat. No. 4,283,288,
(See Japanese Patent Application Laid-Open No. 50-35088).

【table】

【table】

[Table] On the other hand, it is also known that a similar crystalline catalyst precursor can be obtained by reaction in an aqueous medium (see JP-A-56-45815, etc.). This precursor exhibits a characteristic X-ray diffraction pattern as shown in Table 3, for example.

[Table] Comparing Table 1 and Table 3 above, the positions of the diffraction peaks in both coincide with each other, but there is a significant difference in the intensity ratio. That is, the precursor produced by the organic solvent method has a characteristic that the peak intensity at 2θ = 30.5° (±0.2°, the same applies hereinafter) is greater than the peak intensity at 2θ = 15.6°, and the precursor produced by the aqueous media method This shows that the way the crystals develop is different from that obtained in . There have been several proposals so far regarding methods for producing catalyst precursors using organic solvents. For example, JP-A-50-35088 uses vanadyl trichloride (VOCl ₃ ), vanadium pentoxide, ammonium metavanadate, etc. as pentavalent vanadium compounds, and combines these with orthophosphoric acid, tetrahydrofuran, isobutanol, 1,2-dimethoxy We have proposed a method in which the reaction is carried out in an organic solvent such as ethane. Also, JP-A-56-
No. 91845 uses alcohols as reducing organic liquids,
In particular, a method is proposed in which a pentavalent vanadium compound is reacted with orthophosphoric acid using isobutanol. Similarly, JP-A-56-168837 proposes a method for preparing precursors in the medium of substantially anhydrous reducing organic liquids, inter alia selected from alcohols, ketones, aldehydes, ethers and mixtures thereof; The use of butanol is indicated. Furthermore, in US Pat. No. 4,283,288, vanadium pentoxide is reduced using an ethanol-glycerol system,
This is reacted with 100% (crystalline) orthophosphoric acid to synthesize a precursor, which is then separated by over-drying. It has been found that X-ray diffraction of this product shows the same pattern as shown in Table 1. According to the knowledge of the present inventors, the removal of water produced by reduction in the synthesis process of this crystalline precursor (usually
If the isobutanol solvent itself or azeotropic removal by adding an azeotropic solvent such as benzene) is incomplete,
In the X-ray diffraction pattern of the resulting crystal, 2θ=
The peak intensity ratio of 15.6° and 2θ=30.4° is reversed and gradually approaches that shown in Table 3. Therefore, it is desirable to carry out the manufacturing process of this precursor in an anhydrous state as much as possible. JP-A-57-122944 discloses that the precursor obtained by the above method is directly used or dispersed in an aqueous medium containing silica sol to form an aqueous slurry, and then spray-dried to form microspheroidal catalyst particles. A method for producing a fluidized bed oxidation catalyst containing vanadium and phosphorus is proposed. but,
Further tests by the present inventors revealed that the mechanical strength of the obtained catalyst was extremely low and it lacked suitability as an industrial catalyst.Furthermore, the particles were sticky and had poor fluidity, making it unsuitable for industrial use. When used in a fluidized bed reactor, a slugging phenomenon occurred and it was difficult to maintain a stable fluidized state. The present inventors have been intensively investigating a method for producing a catalyst suitable for truly industrial fluidized bed reactions that eliminates these drawbacks. By preparing an aqueous slurry containing a mixed solution containing a phosphorus compound and a silica sol, and spray-drying the mixture after appropriate mixing and homogenization, the mechanical strength and fluidity of the particles are significantly improved, and the active The present invention was completed after discovering that a good catalyst could be obtained. That is, the present invention aims to provide a method for producing a catalyst composition suitable for industrial fluidized bed reactions, in which pentavalent vanadium as a first component is reduced to a tetravalent state in an organic solvent. A crystalline composite oxide containing tetravalent vanadium and pentavalent phosphorus obtained by reacting a pentavalent vanadium compound and a pentavalent phosphorus compound, tetravalent vanadium and phosphorus as the second component. The gist of the present invention is a method for producing a catalyst composition, which comprises mixing an aqueous solution containing a silica sol and a silica sol as a third component to prepare a slurry, and spray-drying the slurry. Next, the method of the present invention will be divided into standard steps and each will be explained in detail. The crystalline catalyst precursor that gives the X-ray diffraction pattern shown in Table 1 is obtained by reducing a pentavalent vanadium compound, especially vanadium pentoxide, in a reducing organic solvent as close to anhydrous as possible, as described above. It can be synthesized by reacting it with orthophosphoric acid. Orthophosphoric acid is easily available on an industrial scale85
Although % aqueous solutions can be used, it is preferable to use anhydrous solutions, especially those that are usually commercially available as colorless solids. The purity of this product is usually in the range of 98-100%. Orthophosphoric acid may be mixed with vanadium pentoxide and an organic solvent from the beginning, or may be added after at least a portion of vanadium pentoxide is reduced by heating in an organic solvent. In this case, orthophosphoric acid may be added as a solid, or it may be added as a solution separately dissolved in an organic solvent, if necessary, after water is azeotropically removed. Organic solvents that can be used include aliphatic or cycloaliphatic alcohols, ketones, aldehydes, ethers, and mixtures thereof, but organic solvents with low boiling points slow down the reduction rate of vanadium pentoxide at the boiling point. It may be necessary to take measures such as using other easily reducible organic compounds in combination or carrying out the synthesis reaction under pressure. Most preferably, the synthesis reaction is carried out using an organic solvent with a boiling point close to that of water, such as a _C3 to _C5 alcohol such as isobutanol or n-propanol, while removing water produced by reduction azeotropically. good. In addition, iron, titanium, chromium, aluminum, magnesium, calcium,
Ions of metals such as nickel and cobalt may be added in an amount ranging from 0 to 0.4 gram atom per gram atom of vanadium. When the synthesis reaction is completed, the entire slurry turns into a pale blue uniform slurry, which is separated, washed with a low-boiling organic solvent such as methanol or acetone, and recovered. For more complete separation of the organic solvent, drying treatment by heating, reduced pressure, etc. is also a preferable operation for the following steps, which are problematic. In the above first step, a crystalline vanadium phosphate precursor containing substantially tetravalent vanadium is obtained, and the X-ray diffraction pattern of the powder is as shown in Table 1.
It matches what is shown in 1. The second step in the present invention is an optional step of firing the precursor. Preferably, the crystalline precursor obtained in the first step is used in this step.
Calcinate at a temperature range of 350-650℃. This firing is performed in a gas atmosphere such as nitrogen, rare gas, carbon dioxide, or air. It is also possible to calcinate using air containing butane, butene, etc. The precursor is dehydrated by calcination, and the crystal morphology changes from the X-ray diffraction pattern shown in Table 1 to that shown in Table 2. The X-ray diffraction pattern shown in Table 2 corresponds to that of the already known beta phase. Regarding the beta phase, U.S. Patent No.
Described in No. 3864280. In addition, the X-ray diffraction pattern in Table 2 was published in the Journal of E.Bordes et al.
Catalysis, 57 , 236−252 (1979) (VO) ₂ P ₂ O ₇
It is also similar to the crystalline phase reported as Examples of suitable firing methods discovered by the present inventors include the following method. After firing at 450-650℃ for 0.1-10 hours in an atmosphere of a gas that does not substantially contain oxygen, such as nitrogen or rare gas, and then at 450-600℃ for 0.1-10 hours in an oxygen-containing gas atmosphere such as air. How to add to baking. 450-650℃ for 0.1-10 hours, oxygen concentration 1-1
A method of firing under a gas atmosphere in the range of 15%. By these firing methods, the X-ray diffraction pattern matches that shown in Table 2, but the valence of vanadium is oxidized to a pentavalent state in about 2 to 35% of the total vanadium. In this state, when catalyzed through the following steps, it exhibits particularly high performance in terms of active surface. The third step of the present invention is a step of producing a mixed solution containing a vanadium compound having a substantially tetravalent valence and phosphate ions. Even when this solution is dried and calcined, it only changes to an amorphous composite oxide based on X-rays, and is clearly distinguishable from the crystalline oxide obtained in the first or second step. It has been found that it not only has activity as an oxidation catalyst by itself, but is also a significantly effective component in improving the mechanical properties of a catalyst, especially a fluidized bed catalyst. One of the preferred forms of this solution is a stabilized vanadyl phosphate aqueous solution, for example,
An aqueous solution shown in 30049 can be used. That is, a vanadium compound having a pentavalent valence such as vanadium pentoxide is reacted with a reducing agent such as hydrazine hydrate, phosphorous acid, oxalic acid, or lactic acid in an acidic aqueous solution of phosphoric acid to form a tetravalent valence state. It can be obtained by reducing it to , and further adding or leaving oxalic acid to stabilize it. The fourth step of the present invention is a catalytic step using a spray drying method. The precursor obtained in the first step or the fired product obtained in the second step is used as a powder. The finer the particle size of the powder, the better the catalytic activity and mechanical properties of the catalyst. Therefore, it is better to pulverize the slurry in advance using a known method when preparing the slurry, or to pulverize and mix in a wet method after preparing the slurry. In particular, the latter is industrially more advantageous. This powder component will be referred to as the first component of the catalyst. Even when the catalyst is prepared in the form of a precursor, it can be converted to the fired product obtained in the second step by spray drying and firing, so in practice both can be considered to be the same product. Next, the solution obtained in the third step changes into an amorphous composite oxide solid during spray drying and calcination, which will be referred to as the second component of the catalyst.
Contains the powder of the first component, the solution containing tetravalent vanadium and phosphate ions obtained in the third step which becomes the second component, and the silica which becomes the carrier component of the catalyst (third component) as a colloidal solution. A catalyst suitable for a fluidized bed reaction is produced by mixing silica sol and converting it into a sufficiently homogeneous slurry using a known wet grinder if necessary, followed by spray drying. The weight fraction of the first component, second component, and third component is preferably (10-70):(10-60):(10-40). Machines that can be used for the purpose of wet grinding and slurry homogenization include, for example, ball mills, rod mills, stirring mills, sand grinders, ultra homo mixers, ultra taraxes, ultrasonic mills, high pressure mills and the like. The slurry thus prepared is then spray dried into spherical solid particles. The conditions for spray drying are usually that the inlet temperature of the drying gas is 160 to 350.
℃, and the outlet temperature should be between 100 and 350℃. In addition, by adjusting the liquid supply amount and disk rotation speed, the average particle diameter of solid particles obtained by spray drying was adjusted to 30.
It should be in the range of ~100 microns. A more preferred range of average particle size is 40 to 70 microns. The solid particles obtained as described above are further calcined to form catalyst composition particles. Firing is usually 400
It is carried out at ~700°C, preferably 450-600°C.
As the firing atmosphere, nitrogen, rare gas, air, a mixture thereof, and air containing organic substances such as butane and butenes can be used. The catalyst particles obtained by the method of the present invention have excellent fluidity, strength and activity, and are suitable as a catalyst for producing maleic anhydride by oxidizing a hydrocarbon having 4 carbon atoms, particularly n-butane. Further, the catalyst particles obtained in the present invention can be further molded by a known method such as tablet molding and used as a fixed bed reaction catalyst. 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 1 (Production example of catalyst precursor in the first step-1) 2 liters of isobutanol was mixed with a stirrer, a thermometer,
The mixture was charged into a 3-liter four-necked flask equipped with a reflux condenser, and 121.3 g of vanadium pentoxide and 159.7 g of 98% orthophosphoric acid were added thereto and heated with stirring. A reflux state was reached in 1.5 hours (liquid temperature 105°C), but the slurry gradually changed from yellow-green to pale blue. During this time, the water-isobutanol mixture was distilled off from time to time, and the total amount collected was about 100 g. After refluxing for 10 hours, heating was stopped, the mixture was allowed to cool, and the mixture was filtered under reduced pressure. The cake was further washed with isobutanol and then dried at 150°C under a stream of nitrogen. The X-ray diffraction pattern of this powder matched that shown in Table-1. Example 2 (Production example of catalyst precursor in the first step-2) 2.5 liters of isobutanol, 227.4 g of vanadium pentoxide, and 299.4 g of 98% orthophosphoric acid were charged into the same reaction vessel as used in Example-1. Other than that,
A pale blue catalyst precursor was obtained in exactly the same manner. According to the elemental analysis results of the obtained precursor, P/V
The atomic ratio shows 1.04, which is approximately (V ₂ O ₄ ) (P ₂ O ₅ )
It was found that it is expressed by the composition formula (2H ₂ O).
About 3 kg of the precursor was synthesized by repeating Example-2. Example 3 (Example-1 of Calcining the Catalyst Precursor in the Second Step) The catalyst precursor obtained in Example-2 was placed in an unglazed container 2 with an internal volume of 1 liter in a Matsufuru furnace in which the atmosphere inside the furnace could be controlled. 500g each was added to each pot and fired. After nitrogen was supplied into the furnace and it was confirmed that the nitrogen was completely replaced, the temperature was started to increase, and the temperature was maintained at 500°C for 2 hours. Next, air was gradually introduced and heating was continued for 1 hour, and then allowed to cool. The X-ray diffraction pattern of the fired powder matched that shown in Table-2. Example 4 (Production example of the second component solution in the third step - 1) 7.715 Kg of 85% phosphoric acid and 6.680 Kg of oxalic acid (H ₂ C ₂ O ₄ 2H ₂ O) were added to 6.5 Kg of demineralized water, The mixture was heated to 80°C and dissolved while stirring. Next, add 4.817 kg of vanadium pentoxide little by little while being careful not to foam.
After dissolving, it was allowed to cool. Add water to make total volume 22.86
Kg. This solution has a P/V atomic ratio of 1.264 and contains 0.5 gmol of oxalic acid per gram atom of vanadium. Moreover, this solution was stable and did not cause solid precipitation even after being stored at room temperature for one month. Example 5 (Production example of catalyst in the fourth step)
1) Mix 0.80Kg of the catalyst precursor obtained in Example-2, 2.285Kg of the solution obtained in Example-4, and 2.857Kg of 20% silica sol solution, and wet-grind for 30 minutes using a sand grinder filled with 1mmφ ceramic beads. Grinding and mixing were carried out. The resulting homogeneous slurry was sprayed in a spray dryer, and the dry weight solids concentration of the slurry was 38.5.
%, drying gas inlet temperature 210℃, outlet temperature 130℃
It was warm at ℃. The average particle diameter of the obtained particles is 61 μm
The sphericity was good. Put 100g of this powder into a 1 inch diameter quartz firing tube and make it fluid.
It was air-calcined at 350°C for 1 hour, then nitrogen-calcined at 500°C for 2 hours, and the particle size range of 25-88 μm was sieved to obtain Catalyst-1 for fluidized bed reaction test. A part of this catalyst-1 was made into a 7mm tablet using a tablet-forming machine.
The product was molded to a thickness of φ x 2 mm, further crushed and sieved into 14 to 24 meshes to obtain catalyst 2 for fixed bed reaction test. The composition of the catalyst was first component/second component/third component (carrier) = 35/40/25 (weight ratio), and the overall P/V atomic ratio was 1.16. Example 6 (Production example of catalyst in the fourth step)
2) 0.72Kg of fired product of catalyst precursor obtained in Example-3
A fluidized bed reaction test catalyst-3 and a fixed bed reaction test catalyst-4 were obtained in the same manner as in Example 5 except for the following conditions. Comparative Example 1 Second component of the catalyst according to the invention, namely Example-4
A catalyst containing tetravalent vanadium and phosphate ion obtained without using a solution was manufactured. Using the same sand glider as used in Examples 5 and 6, 0.75 kg of the catalyst precursor obtained in Example 2, 1.50 kg of 20% silica sol aqueous solution, and 0.40 kg of demineralized water were used.
Treated for 30 minutes. The solid concentration of the slurry on a dry weight basis was 38.5%, and the resulting homogeneous slurry was sprayed using a spray dryer under the same conditions as in Example-5. Comparative catalyst-5 for fluidized bed reaction test and comparative catalyst-6 for fixed bed reaction test were obtained through similar calcination treatment. The composition of the catalyst was first component/third component (carrier) = 70/30 (weight ratio). Comparative Example 2 0.70Kg of fired product of catalyst precursor obtained in Example-3
Comparative catalyst-7 (for fluidized bed reaction test) and comparative catalyst-
8 (for fixed bed reaction test) was obtained. Example 7 (Measurement of Mechanical Strength of Catalysts) Catalysts 1, 3, 5 and 7 were subjected to a catalyst strength test. The strength was determined by colliding catalyst particles against a metal plate at high speed in a fluid state, measuring the crushing loss rate within 2 hours, and displaying the result as an index of mechanical strength. The stronger the catalyst, the smaller this value. The results are shown in Table 4.

[Table] Example 8 (Measurement of catalyst activity by fluidized bed reaction test) Each of the catalysts shown in Table 5 was placed in a fluidized bed reactor with an inner diameter of 17 mm.
Add 20ml (particle size 44-116μm) and add 3% n-butane.
Air containing GHSV of 500 was introduced into the reactor and reacted. 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 results are shown in Table-5.

[Table] Example 9 (Measurement of catalytic activity by fixed bed reaction test) A hard glass tube microreactor with an outer diameter of 6 mm was filled with 0.5 ml each of catalysts 2, 4, 6, and 8, and n-
Air containing 1.5% butane was introduced into the reactor at a GHSV of 2000 and reacted. The entire amount of the product was led from the reactor to a heat-retaining gas sampler, and directly analyzed and quantified by gas chromatography. The reaction results are shown in Table-6.

【table】

Claims (1)

[Claims] 1 Tetravalent vanadium and pentavalent vanadium obtained by reacting a pentavalent vanadium compound and a pentavalent phosphorus compound in an organic solvent capable of reducing pentavalent vanadium to a tetravalent state as the first component. A slurry is prepared by mixing a crystalline composite oxide containing phosphorus, an aqueous solution containing tetravalent vanadium and phosphorus as a second component, and silica sol as a third component, and spray-drying the slurry. A method for producing a catalyst composition suitable for producing maleic anhydride by oxidizing a hydrocarbon having 4 carbon atoms, characterized by: