JPH0479698B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a catalyst having high activity and high selectivity that is used when producing maleic anhydride through gas phase oxidation of hydrocarbons having 4 or more carbon atoms, particularly butane, butenes, and butadiene. A composition containing vanadium, phosphorus, and oxygen contains butane,
It is well known that it is an effective catalyst for producing maleic anhydride by oxidizing butenes, butadiene, and even _C5 to _C10 hydrocarbons, and various proposals have been made regarding methods for producing this catalyst. being done. Additionally, there have been many proposals for attempts to improve the activity of catalysts using various additives. Typical additive elements include alkali metals, zinc, titanium, zirconium, manganese, tungsten, chromium,
Examples include iron, lanthanum, cerium, tin, nickel, cadmium, copper, niobium, and cobalt. According to the studies conducted by the present inventors, alkaline earth metals are as effective as the above-mentioned additive elements; however, regarding attempts to use alkaline earth metal elements in vanadium-phosphorus composite oxide catalysts, Several reports have been made so far. For example, US Pat. No. 3,899,516 and US Pat. No. 4,220,595 propose catalysts for producing maleic acid comprising vanadium, phosphorus, and alkaline earth metal elements. According to the examples, this catalyst is obtained by adding calcium phosphate and titanium oxide to a mixed solution of vanadyl oxalate in formamide and water, then adding and mixing phosphoric acid, followed by drying and calcining. According to the inventor's knowledge, in such a catalyst manufacturing method, vanadium exists as an amorphous vanadium-phosphorus composite oxide,
Although it shows activity against olefinic substrates, it has significantly low activity against saturated hydrocarbons such as butane. In the example used in the oxidation of butane in US Pat. No. 3,899,516, the butane conversion rate was 0.51% and the maleic acid selectivity was 56%, but such low conversion rates are extremely inappropriate as an industrial catalyst. british patent
No. 1481446 proposes a method for producing a vanadium-phosphorus oxide catalyst that is also effective for the gas-phase oxidation of butane. According to the example, vanadium pentoxide and orthophosphoric acid are reduced and dissolved in concentrated hydrochloric acid, and then magnesium chloride is added and dissolved, followed by drying, followed by adding water, molding, drying, and firing. It is active against all of butane, butene-1, and butadiene, and the yield of maleic anhydride from butane reaches 42.5% with a catalyst having a composition of V ₁ P _1.05 Mg _0.05 . As a result of additional tests conducted by the present inventor, it was found that the composition obtained in the drying process exhibited an X-ray diffraction pattern similar to that shown in Table 1. It was also found that the so-called catalyst composition after calcination showed an X-ray diffraction pattern similar to that shown in Table 2. In addition, in Special Publication No. 57-24349, vanadium, phosphorus and beryllium, strontium, barium,
Furthermore, they have proposed a catalyst characterized by containing thallium and iron. According to the examples, the catalyst is obtained by dissolving an oxalic acid solution of ammonium metavanadate, phosphoric acid, and further adding barium hydroxide, impregnating it into an α-alumina carrier, and drying and calcining. Although a yield of maleic anhydride from butane of 38% has been achieved using a catalyst with a composition of V ₁ P _3.54 Ba _1.02 , this yield is significantly lower than the same yield from butene and butadiene. Vanadium is converted to vanadium via an oxalic acid complex.
It is converted into a composite oxide containing phosphorus and barium, which is presumed to have a structure similar to that of U.S. Patent No. 3,899,516 based on X-ray diffraction. It is clear that they are essentially different from each other. JP-A-52-46386 describes a method for producing maleic anhydride from butane using a multicomponent catalyst containing vanadium and phosphorus; This is carried out using oxalic acid in an aqueous medium, and then various metal salts are added, dried and calcined to obtain a catalyst, but in Example 7 of the same patent, Nb,
Cu, Mo, Ni, Co, Cr, U, and Mg were added to achieve a yield of 47% maleic anhydride from butane. It is clear that the yield in this reaction is considerably inferior to the catalyst performance of the present invention described later, but this is because the active component does not contain the crystalline composition (first component) according to the present invention. That's all. JP-A No. 54-13483 proposes a method of producing the crystalline vanadium phosphate compound used in the present invention by using vanadium pentoxide as a raw material and reacting it with reduced phosphoric acid using an inorganic reducing agent.
Metal powder was used as the reducing agent, including tungsten, molybdenum, magnesium,
We present aluminum, nickel, and also V-P-
U-X-O (X: Ta, Ce, Cr, Mn, Co, Cu,
We propose catalysts with the following compositions: Hf, Zr, Th, Sb, Fe, Bi, W, Mo, alkali metal elements, alkaline earth metal elements). There are no examples of reduction of vanadium pentoxide with magnesium, and V-P-U
There are no examples of the use of alkaline earth metal elements in catalysts with the -X-O composition, and their effects are unknown.
In any case, a compound in an oxidized state of the metal used as a reducing agent is mixed in the crystalline active ingredient. This is because the crystalline active ingredient used in the present invention is essentially composed of vanadium and phosphorus, and the alkaline earth metal element, unlike the crystalline active ingredient, is composed of amorphous phosphorus-vanadium complex oxide and silica. It can be clearly identified in that it is contained in the containing layer. Special publication
56-141840 also uses Ti, Ni, Fe, Li,
Although a method of adding Mg is proposed, the existing form of the added component is the same as in the above-mentioned JP-A-54-13483. The present inventors have discovered that the catalytic activity is improved by adding an alkaline earth metal component to the amorphous portion of the catalyst composition rather than to the crystalline vanadium-phosphorus composite acid compound that is the catalytic active component. The invention has been achieved. That is, the present invention contains a crystalline composite oxide containing vanadium and phosphorus as a first component and exhibiting an X-ray diffraction spectrum shown in Table 1 or Table 2 below, an aqueous solution containing vanadyl phosphate as a second component, The gist is a method for producing a catalyst composition, which comprises mixing at least one compound selected from magnesium, calcium, strontium, and barium as a third component and a silica-based catalyst carrier as a fourth component, and then drying the mixture. It is something to do.

【table】

[Table] The present invention will be explained in more detail below. The present invention is characterized by the use of a crystalline composite oxide containing vanadium and phosphorus that exhibits the X-ray diffraction pattern shown in Table 1 or Table 2 as an active ingredient. The diffraction pattern shown in Table 2 has already been reported by E. Bordes and P. Courtine as (VO) ₂ P ₂ O ₇ (J. Catal. 57 ,
236-252 (1979)). Next, the diffraction pattern shown in Table 1 has already been
95990 or JP-A-146287, JP-A-54-
It is the same substance as the crystalline vanadium-phosphorus composite oxide described in 161594, etc., and can be converted into another crystalline oxide shown in Table 2 by firing it at high temperature, so its precursor is It can be considered as a substance. The following methods are known as methods for producing precursors. 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 in which the soluble vanadium-phosphorus complex produced after reacting with phosphoric acid is precipitated by adding water.
-95990), a pentavalent vanadium compound such as vanadium pentoxide and phosphoric acid are reacted in an aqueous medium in the presence of a reducing agent such as hydrazine hydrochloride or hydroxylamine hydrochloride, and concentrated or evaporated to dryness. Method for obtaining crystals by solidifying
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. Pat. 4283288) etc. are known. By any of the above methods, the composite oxide precursor (Table 1), which is the first component, can be obtained. In the present invention, it is preferable that the first component, the crystalline phosphorus-vanadium composite oxide, has substantially 100% purity, and for this purpose, a precursor having substantially 100% purity is also produced. There is a need to. For this purpose, it is particularly preferable to manufacture by the method shown below. That is, it is produced by dissolving vanadium pentoxide in an aqueous medium to form a homogeneous solution in the presence of phosphoric acid and an inorganic reducing agent, and then hydrothermally treating this solution at a temperature in the range of 110°C to 250°C. As the inorganic reducing agent, hydrazine (usually commercially available as an aqueous solution of hydrazine hydrate) or its phosphate, and hydroxylamine or its phosphate are preferred. Other inorganic acid salts, such as hydrochloride, can also be used, but they leave halogen ions behind, which is disadvantageous in terms of the reactor material, and is not preferred industrially. Water is generally used as the aqueous medium. Alcohol, carboxylic acid, ethers, if desired
A hydrophilic organic solvent such as ketones may be used in combination, but since the rate of reduction of vanadium is reduced, the amount used should be 50% by weight or less in the aqueous medium. Although the P/V atomic ratio of the target product, vanadium-phosphorous crystalline oxide, is 1, it is preferable to add phosphoric acid in an amount usually in the range of 0.8 to 1.5.
The phosphoric acid concentration in the aqueous medium is between 5 and 50% by weight, preferably between 5 and 35% by weight. If the concentration of phosphoric acid in the aqueous medium is too high, vanadium pentoxide may react with the phosphoric acid before it is reduced, and the viscosity of the solution increases significantly, making handling difficult. Moreover, if this concentration is too low, the reaction vessel may become too large, which may cause problems. The amount of the inorganic reducing agent used is the stoichiometric amount required to reduce pentavalent vanadium to tetravalent vanadium, and is usually used in a range of 95 to 120% of the stoichiometric amount. The solution obtained in the above manner is then placed in a substantially sealed container to prevent evaporation of water.
Hydrothermal treatment is carried out at a temperature of 110°C to 250°C, preferably 120°C to 180°C. The hydrothermal treatment is preferably carried out for about 0.5 to 200 hours. When the hydrothermal treatment is carried out in this manner, a slurry containing fine gray-blue crystals is produced. This crystal is the target vanadium-phosphorous oxide and can be obtained by evaporating the slurry to dryness or directly filtering it from the slurry. In the present invention, oxides with finer particle sizes can be obtained than in conventional methods. Furthermore, an activity promoting component may be added to the first component of the present invention. Activity-promoting ingredients include iron, chromium,
Examples include compounds such as aluminum, titanium, calcium, magnesium, manganese, cobalt, and nickel. These compounds are not particularly limited as long as they are soluble in the solution obtained in the present invention, but preferably inorganic acid salts such as chlorides, sulfates, nitrates, and carbonates, and organic hydrochloric acids such as acetic acid and oxalic acid. can be mentioned. In the case of titanium, the use of peroxides is also possible. The timing of addition is preferably before hydrothermal treatment. The amount added should be adjusted to a range of 0.01 to 0.4 mol of metal per mol of vanadium element, and more preferably 0.02 to 0.2 mol. The above-mentioned metal components may be one kind or a mixture of two or more kinds if desired. When such an activity-promoting component is added, the positions of the X-ray diffraction spectra of the ultimately obtained precursor and first component composite oxide may be slightly shifted, but the range is within ±0.2°. be.
(See JP-A-56-69207 and JP-A-57-111218.) When the precursor thus obtained is fired under the conditions described below, it becomes a crystalline oxide having the peaks shown in Table 2. The second component in the present invention is an aqueous solution containing tetravalent vanadium and pentavalent phosphorus, and it is preferable that at least a portion of the vanadium is present as vanadyl phosphate. This component is preferably one that normally changes to an amorphous phosphorus-vanadium composite oxide by X-rays in a dry state. The method for producing the aqueous solution as the second component is shown below, but is not particularly limited. Generally, it is obtained by adding and dissolving a reducing agent and vanadium pentoxide in an aqueous solution containing phosphoric acid. The molar ratio of elemental phosphorus to elemental vanadium 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 1.2 or less in molar ratio of oxalic acid to vanadium element, preferably
It ranges from 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 so that the molar ratio of oxalic acid to vanadium element is 1.7 or less and preferably 0.7 or more to contain vanadyl phosphate and oxalic acid. This is a method of making an aqueous solution. 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 be present per 1 atom of vanadium. 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. Although this second component has significantly lower activity than the first component, it has a large effect of dispersing the first component into the catalyst, and is particularly effective in masking pores of 100 Å or less that are harmful to selective catalysts. and can improve the activity of the entire catalyst. The alkaline earth metal compounds as the third component according to the present invention include compounds of magnesium, calcium, strontium, and barium, excluding beryllium, and strongly reducing compounds such as these metals, hydrides, and borohydrides. Not suitable for use. Most preferred are divalent compounds of elements such as oxides, hydroxides, silicates, carbonates, bicarbonates, chlorides, nitrates, sulfates, phosphates, acetic acids,
Examples include organic acid salts such as oxalic acid, and organic compounds/complexes such as acetylacetonate. These can be added as solid compounds or in the form of solutions or slurries in an aqueous medium. The timing of adding this third component is not limited, but when mixing the first component with the second component and the fourth component,
Alternatively, it may be added to the slurry containing the first component after hydrothermal treatment of the first component, or it may be added when producing the second component. The amount of the third component added is in the range of 0.0002 to 0.2, preferably 0.002 to 0.1 in atomic ratio to vanadium. As the silica-based carrier of the fourth component according to the present invention, silica gel, hydrogel, aerosil, etc. obtained in advance as an oxide solid can be used, but diatomaceous earth, which is a natural silicate mineral, and silica alumina containing aluminum can be used. , clay minerals, zeolites, etc. may also be used. When producing a fluidized bed catalyst, which is a more preferred form of use of the catalyst of the present invention, at least a part of the carrier component should be in the form of a solution such as colloidal silica (silica sol). The first to fourth components described above are mixed, dried, and fired to form a catalyst. The first component is used as a precursor, or the precursor is calcined at 300 to 700°C in butane or air that may contain butene, or in an inert gas atmosphere such as nitrogen or argon. The composite oxide having the X-ray diffraction spectrum shown in FIG. 1 may be prepared and then mixed with other components. The mixing ratio of the first and second components is preferably determined so that the ratio of phosphorus atoms to vanadium atoms (P/V) in the final catalyst composition is in the range of 0.8 to 1.5. The weight ratio of the first component, second component, and fourth component is first component: second component (dry weight): fourth component = 1:0.1 to 7:0.05 to 4, preferably 1:0.5 to 4:0.5. It is better to set it to ~2. When making a fixed bed catalyst by appropriately mixing the four components within the above range, the dried solid or semi-dry paste can be molded before or after calcination to form a fixed bed catalyst. use. When the silica carrier as the fourth component is in the form of bulk particles or molded particles, a homogeneous mixed slurry of the first, second, and third components can be coated on the carrier. In the case of a catalyst used in a fluidized bed reaction, which is a more preferred embodiment of the present invention, the first component, second component, third component, and fourth component consisting of an aqueous colloidal silica solution are mixed homogeneously and the slurry is sprayed. Convert to highly spherical particles by drying method. In this case, it is particularly preferable that the solid of the first component be pulverized into fine particles, and it is preferably pulverized to have an average particle size of usually 5 μm or less, more preferably 1 μm or less. This pulverization can be carried out using known dry or wet pulverizers, but industrially it is more efficient to process the slurry obtained by mixing the four components using a continuous wet pulverizer. . The particle size of the fluidized catalyst is 20~250μ, the average particle size is 40~
It is best to keep the thickness within a range of about 80μ, and this can be achieved by setting the spray drying conditions. Calcination of the catalyst is
The process is carried out in a gas atmosphere such as air, nitrogen, helium, steam, carbon dioxide, etc. using various industrially usable kilns such as a matzuru kiln, a kiln kiln, and a fluidized kiln. The gas atmosphere may be in a flowing state. The firing temperature is preferably in the range of 300 to 700°C, more preferably in the range of 450 to 650°C. The catalyst obtained as described above can be effectively used for producing maleic anhydride by oxidizing hydrocarbons having 4 or more carbon atoms. As a hydrocarbon, n-
Butane, n-butene, isobutene, butadiene, etc. can be used alone or in combination. The present invention will be explained below with reference to Examples. Example 1 (Synthesis of first component precursor) 24.6 kg of water and 14.165 kg of 85% phosphoric acid were mixed in a jacketed container with a capacity of 100 and glass lined, and 1.73 kg of 85% hydrazine hydrate solution was added.
Stir and mix. Then vanadium pentoxide 10.635Kg
was added while being careful not to generate bubbles to obtain a uniform blue solution. After that, the temperature of the heating medium was increased, and after confirming that bubble generation had stopped, the container was sealed and the temperature was increased until the liquid temperature reached 140°C. The time required to raise the temperature was approximately 1.5 hours.
Heating was further continued at this temperature for 10 hours to complete the hydrothermal synthesis. When a small amount of the slurry was passed through and the pale blue precipitate was subjected to X-ray diffraction measurement, the results were as follows:
It was found that it shows a line spectrum. The compositional formula of the solid is roughly (V ₂ O ₄ ) (P ₂ O ₅ ) as a result of elemental analysis.
It turns out that it can be written as (2H ₂ O). This slurry was intimately mixed and spray dried to obtain a pale blue precursor powder used as the first component. Example 2 (Calcination of the first component) 10 kg of the precursor powder obtained in Example-1 was divided into 2-volume porcelain containers in a 500-capacity Matsufuru furnace, and
Fired. The firing atmosphere was such that the inside of the furnace was purged with nitrogen before the temperature was raised, the temperature was raised under a nitrogen stream, and heat treatment was performed at 550°C for 2 hours. Then, air was gradually introduced and the mixture was fired for an additional hour. The obtained powder exhibited a pale yellowish brown color, and as a result of X-ray diffraction, it was found that the X-ray spectrum completely matched the X-ray spectrum shown in Table 2. When the valence of vanadium was measured by redox titration, V ⁵⁺ /ΣV (ratio of pentavalent vanadium to total vanadium) was 23.4%. Example 3 (Production of vanadium phosphate solution as second component) 3.50 Kg (30.357 mol) of 85% phosphoric acid and 3.025 Kg (24 mol) of oxalic acid (H ₂ C ₂ O ₄ 2H ₂ O) in 5.0 Kg of demineralized water.
was added, heated to 80°C, and dissolved with stirring. This includes 2.182Kg (12.0mol) of vanadium pentoxide.
was added little by little and dissolved while being careful not to foam. After this was left to cool, water was added to adjust the concentration so that the total amount was 11.85 kg. The P/V atomic ratio in this solution is 1.265, and the oxide concentration (the proportion of the weight remaining after drying the solution and calcining it at 500° C. in a nitrogen stream) is 35 wt%. Example 4 (Production of catalyst composition) 0.340 kg of the first component obtained in Example-2, Example-
Mix 1.114 kg of the second component solution obtained in step 3, a solution obtained by diluting 0.675 kg of 40% concentration colloidal silica solution with 2.911 kg of demineralized water, and 10 g of various alkaline earth element compounds to be added as the third component. It was thoroughly homogenized using a continuous wet mill. This was then spray-dried to obtain spherical particles with an average particle size of about 60 μm. 60 g of these particles were fired in a flowing state under a nitrogen stream using a quartz tube firing furnace. The firing conditions were 600°C and 3 hours. (Catalyst-1, 2, 3, 4, 5) The P/V atomic ratio in the catalyst is 1.16, and the atomic ratio of alkaline earth elements to vanadium is in the range of 0.039 to 0.013. Example 5 (Production of catalyst 6) First component precursor powder obtained in Example-1 0.379
Kg, second component solution obtained in Example-3 1.114Kg, 40
% concentration colloidal silica sol solution 0.675Kg
A solution diluted with 2.911 kg of demineralized water and 10 g of calcium hydroxide were mixed, sufficiently homogenized using a continuous wet grinder, and then spray-dried and calcined under the same conditions as Example 4 to obtain catalyst 6. Obtained. Comparative Example (Production of Comparative Catalyst) A comparative catalyst was produced in the same manner as in Example 4, except that 10 g of the alkaline earth metal element compound was not added. Reaction example Fluidized catalyst 5 obtained in Examples 4, 5 and comparative example
Grind the g with a porcelain mortar and use a tablet molding machine to form 5mmφ×
After forming into pellets of 3 mmH, they were crushed to obtain particles with a particle size range of 14 to 24 meshes (JIS standard). 1ml
A hard glass micro reactor with a diameter of 6 mm was filled with the catalyst, and a 1.5% n-butane/air mixed gas was passed through the reactor to cause a reaction at GHSV=2000. The product was passed through a heated gas sampler and directly analyzed and quantified using a gas chromatograph. The reaction results are shown in Table-3.

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【table】

Claims (1)

[Claims] 1 Contains vanadium and phosphorus as the first component,
A crystalline composite oxide exhibiting the X-ray diffraction spectrum shown in Table 1 or Table 2 below, an aqueous solution containing vanadyl phosphate as the second component, and a third component selected from magnesium, calcium, strontium, and barium. At least one compound and a silica-based catalyst carrier as a fourth component are mixed and then dried.
A method for producing a catalyst composition suitable for producing maleic anhydride by oxidizing the above hydrocarbons. [Table] [Table]