JPH11302271A - Production of maleic anhydride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing maleic anhydride in a high yield when a >=4C aliphatic hydrocarbon is oxidized in a vapor phase in the presence of a vanadium-phosphorus-based catalyst to produce maleic anhydride. SOLUTION: In this method for producing maleic anhydride by bringing a raw material gas containing a >=4C aliphatic hydrocarbon and molecular oxygen into contact with a vanadium-phosphorus-based catalyst, nitrogen and an inert gas such as helium or neon having >=800 (10<-4> Wm<-1> K<-1> ) coefficient of thermal conductivity at 700 K are made to exist in the raw material gas. In this case, the total concentration of the nitrogen gas and the inert gas is 60-94.5 vol.% and the ratio of the nitrogen gas to the inert gas (the molar ratio of the nitrogen gas/the inert gas) is 0.05/1 to 1/1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing maleic anhydride. More specifically, the present invention relates to an improved method for producing maleic anhydride by subjecting a raw material gas containing an aliphatic hydrocarbon having 4 or more carbon atoms and molecular oxygen to catalytic gas phase oxidation with a vanadium-phosphorus catalyst. is there.

[0002]

2. Description of the Related Art It is well known to produce maleic anhydride by subjecting an aliphatic hydrocarbon having 4 or more carbon atoms, such as n-butane, to gas phase oxidation in the presence of a vanadium-phosphorus catalyst. Many patents have been proposed for the vanadium-phosphorus catalyst to be used, reaction conditions, and the like.

With respect to the oxidation reaction itself, for example, n-
A source gas containing butane and molecular oxygen is brought into contact with a vanadium-phosphorus catalyst to selectively oxidize n-butane to maleic anhydride (see, for example, JP-A-50-35088, JP-B-4-4969, JP-A-5
-115783, JP-B-6-39470, JP-A-9
-3053, JP-A-7-171398, JP-A-7-171
227544, JP-A-7-31883, etc.).

[0004] However, such methods do not provide satisfactory conversion and selectivity.

[0005]

It is a matter of course that increasing the yield of the desired maleic anhydride is industrially advantageous, such as cost reduction, and further improving the yield of maleic anhydride. Has been an ongoing research theme for researchers in this technical field.

Accordingly, it is an object of the present invention to provide an improved method for producing maleic anhydride.

Another object of the present invention is to provide a method for producing maleic anhydride in a higher yield by subjecting an aliphatic hydrocarbon having 4 or more carbon atoms to gas-phase oxidation in the presence of a vanadium-phosphorus catalyst to produce maleic anhydride. It is an object of the present invention to provide a method capable of producing maleic anhydride.

[0008]

Accordingly, the above objects are attained by the following (1) to (6).

(1) A method for producing maleic anhydride by bringing a raw material gas containing an aliphatic hydrocarbon having 4 or more carbon atoms and molecular oxygen into contact with a vanadium-phosphorus catalyst in a gas phase. A method for producing maleic anhydride, wherein nitrogen and an inert gas having a thermal conductivity of 800 (10 ⁻⁴ Wm ⁻¹ K ⁻¹ ) or more at 700 K are present therein.

(2) The method according to (1), wherein the total concentration of the nitrogen gas and the inert gas in the raw material gas is 60 to 94.5% by volume.

(3) The ratio of nitrogen gas to the inert gas (the molar ratio of nitrogen gas / inert gas) is 0.05 / 1 to 1
The method according to the above (1) or (2), wherein the ratio is / 1.

(4) The method according to any one of (1) to (3) above, wherein the inert gas is at least one inert gas selected from the group consisting of helium and neon.

(5) The method according to any one of (1) to (4), wherein the inert gas is helium.

(6) The method according to any one of (1) to (5), wherein the aliphatic hydrocarbon having 4 or more carbon atoms is n-butane.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is characterized by an aliphatic hydrocarbon having 4 or more carbon atoms, molecular oxygen, nitrogen and 700K.
In this method, a source gas containing an inert gas having a thermal conductivity of 800 (10 ⁻⁴ Wm ⁻¹ K ⁻¹ ) or more is brought into contact with a vanadium-phosphorus catalyst. This vanadium-phosphorus catalyst is basically divanadyl pyrophosphate (VO) ₂ P ₂ O
_Although it has a composition of ₇ , but is not particularly limited, its catalyst composition, the atomic ratio of vanadium to phosphorus, the structure of divanadyl pyrophosphate (for example, forms such as α, β and γ type), The activation method and the like may be appropriately changed, and any of those generally used for the production of maleic anhydride or known to be usable can be used. Therefore, the vanadium-phosphorus catalyst used in the present invention may contain various metals for the purpose of accelerating the reaction and the like, and may be used by being supported on a carrier such as silica or alumina.

One example is described in, for example, JP-A-59-13.
As described in No. 2938, the diffraction angle 2θ is 10.7 in the X-ray diffraction spectrum (Cu-Ka against the cathode).
°, 13.1 °, 21.4 °, 24.6 °, 28.4 °
And a vanadium-phosphorus-based oxide catalyst intermediate characterized by having a major peak at 29.5 °, such a catalyst comprising: (a) a vanadium compound such as vanadium pentoxide and a phosphorus compound in an aqueous medium; For example, orthophosphoric acid and hydrazine as a reducing agent are mixed under conditions such that the atomic ratio of phosphorus to vanadium is in the range of 0.7 to 1.25: 1 and the valence of vanadium is in the range of 3.9 to 4.4. Reacting to precipitate the catalyst intermediate composition,
(B) then removing the precipitate from the aqueous catalyst body, (c)
The obtained precipitate is dissolved in an organic catalyst in the presence of a phosphorus compound.
Heat treatment at a temperature of ~ 200 ° C to obtain a catalyst precursor, (d)
The precursor is removed from the organic medium, and (e) the steps of baking the precursor at a temperature of 250 to 550 ° C. are performed in each step, and the atomic ratio of phosphorus to vanadium is 1 to 1.25. A catalyst having a composition of 1.

As described in JP-A-10-167711, an X-ray diffraction spectrum (Cu-
Kα), the diffraction angle 2θ (± 0.2 °) is 18.5.
°, 23.0 °, 28.4 °, 29.9 ° and 43.
It has a main peak of 1 ° and a diffraction angle of 2θ (± 0.2
°) = There are vanadium-phosphorus oxides in which the peak intensity ratios at 23.0 ° and 28.4 ° are within the following ranges.

0.3 ≦ I (23.0) / I (28.4)
≤0.7 where I (23.0) and I (28.4)
Are diffraction angles 2θ (± 0.2 °) = 23.0 °, respectively.
And a peak intensity of 28.4 °.

Preferably, 0.35 ≦ I (23.
0) / I (28.4) ≦ 0.65, more preferably 0.4 ≦ I (23.0) / I (28.4) ≦ 0.6
It is. Vanadium / phosphorus (atomic ratio) is 1/0.
9 to 1 / 1.2, preferably 1 / 0.95 to 1 / 1.1.
It is.

Representative examples of the aliphatic hydrocarbon having 4 or more carbon atoms, preferably 4 to 8 carbon atoms include, for example, n-butane,
Mention may be made of 1-butene, 2-butene, butadiene and mixtures thereof. Usually, n-butane is used. The n-butane may contain a small amount of propane, pentenes and the like, and general industrial n-butane can be used.

At 700K, 800 (10 ^-4 Wm ^-1 K)
^-1 ) As an inert gas having the above thermal conductivity (hereinafter simply referred to as an inert gas), for example, helium (2800
(10 ^-4 Wm ^-1 K ^-1 )), neon (880 (10 ^-4 Wm ^-1 Km ^-1 ))
^-1 K ^-1 )) and the like, alone or in the form of a mixture, and helium is particularly preferred.

The total concentration of nitrogen and inert gas in the raw material gas is usually 60 to 94.5% by volume, preferably 75 to 90% by volume. The ratio of nitrogen and inert gas (nitrogen / inert gas (molar ratio)) is usually 0.05 /
1-1 / 1, preferably 0.05 / 1 to 0.6 /
It is one.

The concentration of the aliphatic hydrocarbon having 4 or more carbon atoms in the raw material gas is, for example, usually 0.5 to 10% by volume, preferably 1 to 5% by volume in the case of n-butane. . The molecular oxygen concentration in the source gas is usually 5 to 30% by volume, preferably 10 to 25% by volume. In addition, as a supply source of molecular oxygen,
Air is used.

The oxidation reaction conditions in the present invention are not particularly limited, and are generally employed or employed in the production of maleic anhydride, except that nitrogen and an inert rare gas coexist in the raw material gas. The oxidation reaction can be performed under conditions known to be possible.

The reaction system may be either a fixed bed system or a fluidized bed system.
The reaction temperature is usually from 300 to 550 ° C, preferably from 300 to 450 ° C. The reaction pressure may be normal pressure or pressurization, but it is usually preferable to carry out the reaction at normal pressure. Further, the space velocity (STP) is usually 500 to 1
000 hr ^-1 , preferably 1,000 to 5,
000 hr ^-1 .

[0026]

The present invention will be described below more specifically with reference to examples and comparative examples. The conversion, selectivity and yield in the examples and comparative examples are defined as follows.

Conversion (mol%) = (mol number of reacted n-butane / mol number of supplied n-butane) × 100 Selectivity (mol%) = (mol number of maleic anhydride formed / reacted) n-butane moles) × 100 yield (mol%) = (moles of maleic anhydride generated /
Preparation of Catalyst (Catalyst-I) 400 g of vanadium pentoxide (V ₂ O ₅ ) was suspended in 4000 ml of benzyl alcohol, and the suspension was kept at 120 ° C. with stirring and reduced for 5 hours. 435.4 g of 99% orthophosphoric acid was dissolved in 1000 ml of benzyl alcohol to prepare a phosphoric acid solution. A phosphoric acid solution is added to the reduced vanadium solution, and the mixture is heated and maintained at 120 ° C.
Upon stirring for 0 hours, a deep blue precipitate was formed. After allowing the reaction solution slurry to cool, the formed precipitate was separated, washed with acetone, and dried at 140 ° C. for 12 hours. Then, it was molded to a length of 5 mm and a diameter of 5 mm. The molded body was calcined at 480 ° C for 4 hours in an air stream to obtain Catalyst-I.

(Catalyst-II) isobutyl alcohol 400
400 g of vanadium pentoxide (V ₂ O ₅ ) was suspended in 0 ml, and the suspension was kept at 105 ° C. with stirring and reduced for 10 hours.
435.4 g of 99% orthophosphoric acid was dissolved in 1000 ml of isobutyl alcohol to prepare a phosphoric acid solution. Add a phosphoric acid solution to the reduced vanadium solution, and add
, And stirred for 10 hours to produce a deep blue precipitate. After allowing the reaction solution slurry to cool, the formed precipitate was separated and washed with acetone.
Dried for hours. Then, it was molded to a length of 5 mm and a diameter of 5 mm. The molded body was calcined at 500 ° C. for 4 hours in an air stream to obtain Catalyst-II.

(Catalyst-III) 85 to 5000 ml of distilled water
After adding 3500 g of orthophosphoric acid and heating and maintaining the temperature at 80 ° C., 400 g of vanadium pentoxide (V ₂ O ₅ ) was added. Heating and refluxing for 12 hours with stirring produced a yellow precipitate. The formed precipitate was separated, washed with acetone, and dried at room temperature. 4000 dried products
The mixture was added to ml of 2-butyl alcohol, heated at 80 ° C. and stirred for 12 hours to produce a blue precipitate. After allowing the reaction solution slurry to cool, the formed precipitate was separated, washed with acetone, and dried at 140 ° C. for 12 hours. Then, it was molded to a length of 5 mm and a diameter of 5 mm. The molded body was calcined at 500 ° C. for 4 hours in an air stream to obtain Catalyst-III.

(Catalyst-IV) 85% in 5000 ml of distilled water
507 g of orthophosphoric acid and 310 hydroxylamine hydrochloride
g, heated and maintained at 80 ° C. 400 g of vanadium pentoxide (V ₂ O ₅ ) was added little by little while paying attention to foaming. When heated and refluxed for 12 hours while stirring, a dark blue precipitate was formed. After allowing the reaction solution slurry to cool, the formed precipitate was separated and washed with acetone.
Dry at 0 ° C. for 12 hours. Then, length 5mm, diameter 5
mm. The molded body was calcined at 520 ° C. for 4 hours in an air stream to obtain Catalyst-IV.

Examples 1 to 12 and Comparative Examples 1 to 12 Condition 1 10 g of each catalyst was charged into a flow reactor, and the n-butane concentration was 1.5% by volume, the oxygen concentration was 20% by volume, and the nitrogen concentration was 2%.
A mixed gas of 0 vol% and a helium concentration of 58.5 vol% was supplied at a space velocity of 1000 hr ^-1 and an activation treatment was performed at 480 ° C. for 12 hours. Gas phase oxidation was performed.

Condition 2 10 g of each catalyst was charged into a flow-type reactor, and an air-mixed gas having an n-butane concentration of 1.5% by volume was filled with a space velocity of 1000.
The resultant was supplied at a rate of hr ^-1 and an activation treatment was performed at 480 ° C. for 20 hours. Thereafter, an n-butane concentration of 1.5% by volume, an oxygen concentration of 20% by volume, a nitrogen concentration of 20% by volume and a helium concentration of 5%
Switch to a mixed gas of 8.5% by volume, space velocity 1000
The gas phase oxidation of n-butane was carried out at a reaction temperature which was supplied at hr ^-1 and showed the maximum yield.

Condition 3 10 g of each catalyst was charged into a flow reactor, and the n-butane concentration was 1.5% by volume, the oxygen concentration was 20% by volume, and the nitrogen concentration was 2%.
After supplying a mixed gas of 0 vol% and a neon concentration of 58.5 vol% at a space velocity of 1000 hr ^-1 and performing an activation treatment at 480 ° C. for 12 hours, at a reaction temperature showing the maximum yield,
Gas phase oxidation of n-butane was performed.

Condition 4 10 g of each catalyst was charged into a flow reactor, and the n-butane concentration was 1.5% by volume, the oxygen concentration was 20% by volume, and the nitrogen concentration was 2%.
A mixed gas of 0% by volume and an argon concentration of 58.5% by volume was supplied at a space velocity of 1000 hr ^-1 and an activation treatment was carried out at 480 ° C. for 12 hours. Gas phase oxidation was performed.

Condition 5 10 g of each catalyst was charged into a flow reactor, and the n-butane concentration was 1.5% by volume, the oxygen concentration was 20% by volume, and the nitrogen concentration was 2%.
After supplying a mixed gas of 0 vol% and a methane concentration of 58.5 vol% at a space velocity of 1000 hr ^-1 and performing an activation treatment at 480 ° C. for 12 hours, at a reaction temperature showing the maximum yield,
Gas phase oxidation of n-butane was performed.

Condition 6 10 g of each catalyst was charged into a flow-type reactor, and an air-mixed gas having an n-butane concentration of 1.5% by volume was filled with a space velocity of 1000.
After supplying at hr ^-1 and performing an activation treatment at 480 ° C. for 12 hours, n-butane was subjected to gas-phase oxidation at a reaction temperature showing the maximum yield.

Table 1 shows the test results.

[0038]

[Table 1]

[0039]

According to the present invention, nitrogen and 7
By coexisting with an inert gas having a thermal conductivity of 800 (10 ^-4 Wm ^-1 K ^-1 ) or more at 00K, the target maleic anhydride can be produced in high yield.

Claims (6)

[Claims] 1. An aliphatic hydrocarbon having 4 or more carbon atoms and a component thereof.
A raw material gas containing dendritic oxygen is converted to a vanadium-phosphorus-based catalyst.
In the method of producing maleic anhydride by contact in the gas phase
And 800 at nitrogen and 700K in the source gas.
(10^-FourWm ^-1K^-1) Inert gas with thermal conductivity above
Of maleic anhydride characterized by the presence of sulfuric acid
Method. 2. The total concentration of nitrogen gas and said inert gas in said source gas is 60 to 94.5% by volume.
The method described in. 3. The method according to claim 1, wherein the ratio of the nitrogen gas to the inert gas (molar ratio of nitrogen gas / inert gas) is 0.05 / 1 to 1/1. 4. The method according to claim 1, wherein the inert gas is at least one inert gas selected from the group consisting of helium and neon. 5. The method of claim 1, wherein said inert gas is helium.
The method according to any one of claims 4 to 4. 6. The method according to claim 1, wherein the aliphatic hydrocarbon having 4 or more carbon atoms is n-butane.