JPH0819115B2 - Method for producing maleic anhydride - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing maleic anhydride. More specifically, the present invention relates to the use of a highly active and highly selective catalyst in a method for producing maleic anhydride by catalytically oxidizing a hydrocarbon in the gas phase in the presence of a vanadium-phosphorus catalyst.

[Conventional technology]

A technique for producing maleic anhydride by subjecting a saturated or unsaturated straight-chain hydrocarbon having 4 carbon atoms to gas-phase oxidation is well known, and many catalysts have been proposed in the past. It is becoming more and more important to consider improvements to improve the rate.

In general, complex oxides containing vanadium and phosphorus have long been used as catalysts for this reaction, but when the substrate is a saturated linear hydrocarbon having 4 carbon atoms, that is, n-butane, Crystalline divanadyl pyrophosphate ((VO) ₂ P ₂ O ₇ ) showing an X-ray diffraction peak is specifically highly active. However, in this case as well, due to volatilization of the phosphorus component,
It is not easy to maintain high activity, and addition of a wide range of modifying components has been studied for the purpose of further improving activity and selectivity. For example, in Japanese Examined Patent Publication No. 53-43,929, in addition to phosphorus and vanadium, a catalyst system in which iron, nickel, boron, silver, cadmium and barium, and chromium are added is also disclosed.
57-45,253 proposes a catalyst system in which cobalt, nickel, and cadmium are added to phosphorus and vanadium. Furthermore, in U.S. Pat.No. 4,151,116, a catalyst system in which a wide variety of metal salt solutions are post-impregnated and supported on a phosphorus-vanadium complex oxide, including magnesium, zinc, cobalt, iron, manganese, nickel, indium and copper, is provided. It is claimed to have excellent performance. Further, in JP-A-58-150,437, it is claimed that silicon, and indium, antimony, and a modifying component consisting of tantalum are brought into contact with vanadium and then reacted with phosphorus, which is more than a case where the modifying component is added as a simple mixture. Research has been aimed at improving the effect of modification by devising the addition method.

[Problems to be solved by the invention]

However, these methods cause elution of the catalytically active component, destruction of the shape, chemical destabilization, etc. when the modifying component is used. Therefore, it was found that there are many drawbacks when the catalyst production is considered on an industrial scale.

In particular, according to the study of the present inventors, in the phosphorus-vanadium composite oxide clearly having the crystal structure of vanadyl pyrophosphate, when various metal components are supported or added, in many cases,
Since only the combustion activity is emphasized, the target yield of maleic anhydride tends to decrease even if the activity is improved and the reaction can be performed at a relatively low temperature. Therefore, in such a case, it is customary that not only the quality of the modifying component but also the addition amount and the addition method need to be devised.

[Problems to be solved by the invention]

The present inventors have developed a catalyst having remarkably high performance in a reaction for producing maleic anhydride by vapor phase oxidation of an unsaturated or saturated hydrocarbon having 4 carbon atoms such as butane, butene, butadiene, etc. By carrying out the reaction at a relatively low reaction temperature, avoiding the risk of spontaneous combustion, and as a result of intensive studies to improve the yield of the desired product, the present invention has been achieved. Is.

That is, according to the present invention, when producing a maleic anhydride by vapor-phase oxidizing a hydrocarbon having 4 carbon atoms, the active components in the reaction system mainly consist of vanadium, phosphorus and oxygen, and at least a part of them is pyrophosphoric acid. Divanadyl ((VO) ₂ P ₂ O ₇ )
A composite oxide having the structure of, wherein indium and nickel are added to the composite oxide as active modifying components,
It is a gist of a method for producing maleic anhydride, which is characterized in that a catalyst formed by adding one or more elements selected from the group consisting of cobalt and copper is present.

 The present invention will be described in detail below.

In the present invention, when producing a maleic anhydride by vapor-phase oxidizing a hydrocarbon having 4 carbon atoms, the active components in the reaction system mainly consist of vanadium, phosphorus and oxygen, at least a part of which is divanadyl pyrophosphate ( (VO) ₂ P ₂ O ₇ )
A composite oxide having the structure of, wherein indium and nickel are added to the composite oxide as active modifying components,
A catalyst containing one or more elements selected from the group consisting of cobalt and copper is present.

Various methods have been proposed as a method for producing a composite oxide composed of vanadium, phosphorus and oxygen (hereinafter referred to as “VP composite oxide”) that constitutes the catalyst used in the present invention.

For example, JP-B-53-39,037, JP-A-50-35,088,
53-91,110, JP-A-56-91,845, JP-A-56-168,837 and US Pat. No. 4,283,288, etc., by the reaction of a vanadium compound and a phosphorus compound in an organic solvent.
51-95,990 and JP-A-58-151313, a crystalline precursor is produced by a reaction in an aqueous solution, and then this is added to an inert gas such as nitrogen or a butane-air mixed gas or to a low oxygen concentration with nitrogen or carbon dioxide. It is manufactured by firing in an atmosphere such as air that may be diluted with a gas or an inert gas. It is known that this crystalline precursor gives the following characteristic X-ray diffraction peak.

2θ (± 0.2 °) = 15.6 °, 19.7 °, 24.3 °, 27.1 °, 2
8.8 °, 30.5 °, 32.2 °, 33.7 ° This crystalline precursor compound has recently been subjected to X-ray structural analysis and is VO (HPO ₄ ) .0.5H ₂ O or (VO) ₂ H ₄ P ₂ O ₉ . It turns out.

(CC Torardi, JC Calabrese, Inorg. Chem., 23 , 1310
('84) Jack W. Johnson, David C. Johnston, Allan J. Jacobson
and John F. Brody, J. Am. Chem. Soc., 106 , 8123 ('8
4)] There are various types of VP-based composite oxides, which are roughly classified into crystalline ones and amorphous ones. The selection depends on the level of the required catalytic activity, specifically the selection of the starting hydrocarbon, and when a low-reactivity saturated hydrocarbon, that is, butane, is used as the starting material, a crystalline one with a high catalytic activity is used. Is preferably used.

The VP composite oxide of the method of the present invention has at least a part of the structure of divanadyl pyrophosphate ((VO) ₂ P ₂ O ₇ ), which is X-ray diffraction (Cu-Kα anticathode). Is characterized by the following characteristic diffraction line.

2θ (± 0.2 °) = 142 °, 15.7 °, 18.5 °, 23.0 °, 2
8.4 °, 30.0 °, 33.7 °, 36.8 ° In the method of the present invention, in addition to the crystalline complex oxide described above as the VP-based complex oxide, a complex oxide that is X-ray amorphous is added as a main component or It may be contained as an accessory component. This amorphous complex oxide can be produced, for example, by evaporating an aqueous solution containing vanadium hydrochloride or vanadium oxalate and phosphoric acid to dryness, and then, if necessary, firing in the same manner as the crystalline vanadium pyrophosphate. Although possible, a method of evaporating the stabilized vanadium phosphate solution to dryness is often advantageous, for example, as shown in JP-A-58-151,312.

Furthermore, in the method of the present invention, the catalyst component may be supported on various carriers that can be used industrially. For example, various carriers such as alumina, silica, diatomaceous earth, zirconia, zeolite, silicon carbide and pumice can be used. But,
In general, siliceous carriers such as silica and silica sol are preferred, and silica sol is particularly preferred when used as a fluidized bed catalyst.

Further, in the method of the present invention, one or more elements selected from the group consisting of indium and nickel, cobalt and copper are added as an active modifying component to the catalyst of the VP composite oxide.

Among the above-mentioned addition of the active modifying component, the combination of indium-nickel is particularly preferable.

Regarding the amount of addition of the activity-modifying component, the atomic ratio of vanadium and phosphorus is preferably in the following range, including vanadium and phosphorus. (X represents one or more elements selected from the group consisting of Ni, Co and Cu.) V: P: In: X = 1: 1.0 to 2.0: 0.001 to 0.2: 0.001 to 0.2 As a raw material compound for the active modifying component Can employ various forms of compounds that can be industrially used. For example, oxides of indium, nickel, cobalt and copper, hydroxides, halides, molybdates, sulfides, mineral salts such as sulfuric acid, nitric acid, phosphoric acid, formate salts, acetic acid, citric acid, oxalic acid, etc. The salts of organic acids are used. A compound with an alcohol such as isopropanol can also be used if necessary.

The raw material compound of the activity modifying component may be added to any of the above-mentioned crystalline VP-based complex oxide, an aqueous solution containing vanadium and phosphorus, or a mixture thereof.

Further, to the catalyst of the present invention, various secondary modifying components such as iron, zirconium, magnesium, calcium and zinc may be added, if necessary.

When used in the reaction, the catalyst composition obtained by the above-mentioned procedure is usually calcined and activated at a temperature of 300 to 700 ° C, preferably 350 to 620 ° C.

As a firing atmosphere, air or an inert gas such as nitrogen, carbon dioxide or helium, or low oxygen air diluted with these can be used. It is also possible to employ a method in which the reaction gas is fired with air containing butane or butene at a concentration of about 0.05 to 2% for activation. For the calcination, various known devices such as a pine furnace, a tunnel furnace, a rotary kiln, a fluidized bed calcination furnace, etc. can be used, but the gas flow is passed so as to continuously remove the water generated by the temperature rise out of the system. It is preferably carried out below.

The raw material used in the method of the present invention is a hydrocarbon having 4 carbon atoms, preferably a linear hydrocarbon having 4 carbon atoms. Specific examples include n-butane, 1-butene, 2-butene, butadiene and mixtures thereof. Maleic anhydride is produced, albeit in a lower yield, from an aliphatic hydrocarbon having 4 carbon atoms and a side chain, such as isobutane or isobutylene. The most economically advantageous feedstocks are n-butane and butenes, usually as C ₄ cuts obtained by separation from natural gas or by naphtha cracking or FCC reactions and, if desired, butadiene. It is used as the remaining mixture after extraction of isobutylene. In these cases, usually C ₃ or C ₅
The hydrocarbons mentioned above are also mixed as impurities, but there is no particular problem.

In the method of the present invention, these hydrocarbons form maleic anhydride which is catalytically oxidized in the gas phase in the presence of the vanadium-phosphorus catalyst. A molecular oxygen-containing gas, usually air, is used as the oxidant. The raw material hydrocarbon is usually 0.1 to 8% (vol) as the concentration in the air, and more preferably 1.
In the range of 0 to 4.5%, the catalyst layer is introduced simultaneously with air or individually to be oxidized. The reaction temperature is usually 300 to 550.
° C., more preferably in the range of 350 to 500 ° C., the reaction pressure is usually normal pressure on, and more preferably in the range of 0.1 to 10 / cm ^2G.

In oxidizing a substrate having low reactivity such as butane, a carrier component such as a VP-based complex oxide raw material solution and silica sol and an active modifying component are mixed and spray-dried as a uniform slurry. The activity can be enhanced by using a catalyst for a fluidized bed reaction close to a sphere. The combined use of a crystalline and an amorphous VP-based composite oxide is often extremely effective in stabilizing the activity of the resulting fluidized bed catalyst and improving its mechanical strength.

In the gas-phase oxidation reaction of a substrate having low reactivity such as butane, a catalyst having sufficiently high activity is desired even if the reaction temperature is lowered. In the method of the present invention, crystalline divanadyl pyrophosphate effective for this oxidation reaction is desired. By allowing a composition having a structure and a specific activity-modifying component to coexist, the activity can be further enhanced and a high selectivity can be obtained. Generally, as a catalyst for industrial use, it is desirable to use a fluidized bed catalyst for the control of heat generation in the case of a gas phase oxidation reaction having a strong heat generation, but the active modification component in the present invention contains crystalline divanadyl pyrophosphate. It also has the effect of imparting sufficiently high performance to the fluidized bed catalyst system.

〔Example〕

Next, the embodiments of the present invention will be described more specifically with reference to Examples, but the present invention is not limited to the following Examples without departing from the gist thereof.

Catalyst Production Example-1 (A) Production of crystalline oxide precursor: Table A below: Table A X-ray diffraction peaks (cathode: Cu-Kα) 2θ (± 0.2 °) 15.7 ° 19.6 ° 24.2 ° 27.1 A crystalline oxide precursor having an X-ray diffraction peak at 28.8 ° and 30.4 ° was prepared as follows.

A glass-lined pressure-resistant container with a volume of 100 l and a jacket, deionized water 38.0 kg, 85% phosphoric acid 21.83 kg, 80%
2.85 kg of a hydrazine hydrate solution was charged, and then 16.40 kg of vanadium pentoxide powder was added and dissolved little by little while stirring while paying attention to foaming. During this period, in order to suppress the temperature rise due to heat generation and keep the liquid temperature at 60 to 80 ° C., the heat medium was circulated in the jacket to remove heat. The addition of vanadium pentoxide was completed in about 4 hours, and a blue vanadyl phosphate solution was obtained. To this, 1.0 kg of seed crystals was added, and then a heating medium at 160 ° C. was circulated in the jacket for heating. The liquid temperature was raised to 140 ° C. in 2 hours, and hydrothermal treatment was carried out for 10 hours as it was. During this time, the pressure was about 0.24 MPa (gauge pressure). After cooling to 90 ° C., 10.3 kg of demineralized water was added to adjust the solid concentration in the slurry to about 35%, and the mixture was extracted.

When X-ray diffraction measurement of the solid in this slurry was carried out, it was found that the main diffraction peaks shown in Table A were exhibited, and it was confirmed to be a pure crystalline oxide. When the particle size distribution of the solid in the slurry was examined by the Coulter counter method, the average particle size was 0.7 μm. The oxide slurry was dried using a spray dryer to obtain 29.8 kg of a pale blue oxide powder of oxide. The P / V atomic ratio of the charged standard of the oxide slurry is 1.05, but the precursor of the crystalline oxide obtained by overwashing is substantially (VO) ₂ H ₄ P ₂ O _{9 in} the composition formula. Confirmed that it is represented.

(B) Production of crystalline oxide: The precursor obtained in (A) above was fired, and the following Table B: Table B X-ray diffraction peaks (anticathode: Cu-Kα) 2θ (± 0.2 °) 14.2 ° 15.7 A crystalline oxide having an X-ray diffraction peak at 18.5 ° 23.0 ° 28.4 ° 30.0 ° 33.7 ° 36.8 ° was produced.

In a pine-furnace having a capacity of 500 liters, 10 kg of the precursor obtained in the above (A) was placed in 10 porcelain dishes having a capacity of 2 liters and arranged side by side, and the inside of the furnace was sufficiently replaced with nitrogen gas and then heated to 550 Heated at ° C for 2 hours. Next, air was gradually introduced into the furnace, the mixture was heated for another 1 hour, and then allowed to cool.

As a result of X-ray diffraction measurement, the powder after firing showed no peaks other than the diffraction peaks shown in Table B, and it was confirmed that the powder was a highly pure crystalline oxide. The proportion of pentavalent vanadium in all vanadium atoms was measured by a redox method, and it was 23.4%. That is, at least a part of vanadium in (VO) ₂ P ₂ O ₇ can absorb oxygen while maintaining its crystal structure and assume a pentavalent valence state.

(C) Production of vanadyl phosphate solution: A vanadyl phosphate solution was produced as a raw material for the amorphous vanadium-phosphorus complex oxide.

2.956 kg of 85% phosphoric acid was dissolved in 3.0 kg of demineralized water, 2.55 kg of oxalic acid (H ₂ C ₂ O ₄ .2H ₂ O) was further added, and dissolved by heating. The liquid was heated to 80 ° C., 1.842 kg of vanadium pentoxide was added little by little while paying attention to foaming, dissolved, and then heated in a boiling state for 10 minutes to complete the reduction. Allow the liquid to cool,
Demineralized water was added to adjust the total amount to 10.00 kg. P of this solution
/ V atomic ratio is 1.2666, oxide _{(V 2 0 4 + P 2} 0 5) concentration of 35.0%
Is.

(D) Production of catalyst: Catalyst-1 8.95 g of the calcined powder produced in the above (B), 27.97 g of the vanadyl phosphate solution produced in the above (C), and 30.19 g of 20% concentration silica sol were mixed to obtain was chloride indium ^{_{(Incl 3 · 4H 2 O)}} 0.499g and acetic acid nickel _{(Ni (CH 3 COO) 2} · 4H 2 O) 0.424g added as active modifying component in the slurry, 30 minutes mixing at high speed homogenizer Then, a sufficiently uniform slurry was obtained. This was dropped onto a hot plate heated to 180 ° C and dried, and then this solid was calcined at 300 ° C for 20 minutes in an air stream, and further heated to 570 ° C under a nitrogen stream for 25 minutes.
Bake for minutes. 6 mm of the obtained solid using a tablet molding machine
Pelletized to a thickness of φ × 2 mm, further crushed and sieved to 24-40 mesh to obtain a catalyst for use. This catalyst is V _1.0 P
_1.16 In _0.015 Ni has an atomic ratio composition of _0.015 .

In activity modifying components used in catalyst -2～4 catalyst -1, to change the amount of indium chloride as shown in Table 1, also cobalt acetate _{(CO (CH 3 COO) 2} · 4H 2 O) and copper acetate (Cu (CH ₃ COO)
₂ · 4H ₂ O), except that was used in amounts shown in Table 1. The catalyst -1
Catalysts-2, 3 and 4 were produced by the same procedure as in.

Comparative catalyst-1 Comparative catalyst-1 was produced by the same procedure as catalyst-1, except that indium chloride and nickel acetate were not added.

Examples 1 to 4 and Comparative Example 1 According to a fixed bed reaction test, catalysts 1 to 4 (Examples 1 to 1)
4) and the activity of comparative catalyst-1 were measured. Outer diameter for reaction
A 6 mm small tubular reactor was used. 4 ml of each catalyst was filled in each and the reaction was carried out under the condition of GHSV 2,000 using 2% butane / air mixed gas. The results of analyzing the product are shown in Table 1. The reaction results are compared at the temperature at which the maximum yield of maleic anhydride is obtained.

Example 5 and Comparative Example 2 Catalyst-1 and Comparative Catalyst-1 were charged into the same reactors used in Example-1, respectively, and 600 hours while controlling the temperature to maintain 95% butane conversion. The reaction was performed under the same reaction conditions as in Example 1 except that the life test of Example 1 was performed.

 The reaction results are shown in Table 1.

As is clear from Table 1, in Examples 1 to 5, the catalytic activity was high, and compared with Comparative Examples 1 and 2, 10
Since the reaction can be carried out at a low temperature of up to -20 ° C, it is very effective in improving safety and it is clear that the target maleic anhydride yield is high.

Example-6 and Comparative Example-3 A fluidized bed catalyst having the same composition as Catalyst-1 and Comparative Catalyst-1 was prepared as follows.

Using a rotary kiln, the spray-dried powder of the crystalline precursor prepared in (A) of Production Example-1 of the above catalyst was 8%.
Firing was performed under an air flow diluted with oxygen concentration to produce 8.95 kg of a crystalline oxide having the X-ray diffraction peak shown in Table-B.
In addition, 22.3 kg of a vanadyl phosphate solution having an oxide concentration of 43.9% was prepared in the same step as in (C) of Production Example-1 of the catalyst.
20% with the obtained crystalline oxide and vanadyl phosphate solution
Was mixed with 31.2 kg of silica sol, and 0.5 kg of indium chloride dissolved in 0.6 kg of water and 0.4 kg of nickel acetate dissolved in 1.7 kg of water were added, and the mixture was sufficiently mixed and pulverized by a wet pulverizer. This slurry was sprayed with a spray dryer to give an average particle size of 65
After obtaining a dry powder of μm, it was calcined in a kiln to prepare a fluidized bed catalyst (catalyst-5).

A fluidized bed catalyst of Comparative Catalyst-2 was prepared in the same manner as Catalyst-5 except that the modifying component was not added. In addition,
The firing conditions in the above kiln were two steps: firing at 350 ° C. in an air stream and firing at 600 ° C. in a nitrogen stream.

Using 25 g of these catalysts, the oxidation reaction of n-butane was carried out in a small fluidized bed reactor made of hard glass. The reaction results for butane concentration 2% and GHSV700 are as follows.

[Effect of the Invention] According to the present invention, maleic anhydride can be produced by gas phase oxidation of a hydrocarbon having 4 carbon atoms using a highly active and highly selective catalyst.

In particular, the performance can be further improved in a fluidized bed reaction suitable for controlling high reaction heat.

The present invention achieves a lower reaction temperature, resulting in improved economy and reduced risk of explosion.

Claims (2)

[Claims] 1. When producing a maleic anhydride by vapor-phase oxidizing a hydrocarbon having 4 carbon atoms, the active component mainly consists of vanadium, phosphorus and oxygen in the reaction system, and at least a part thereof is divanadyl pyrophosphate. A composite oxide having a structure of ((VO) ₂ P ₂ O ₇ ), further comprising one or more elements selected from the group consisting of indium, nickel, cobalt and copper as an active modifying component in the composite oxide. A method for producing maleic anhydride, characterized by comprising the presence of a catalyst as described above. 2. A method for producing maleic anhydride according to claim 1, wherein the active modifying component is composed of indium and nickel.