JP3334296B2 - Method for producing unsaturated carboxylic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an unsaturated carboxylic acid by subjecting an alkane to a gas phase catalytic oxidation reaction. The invention particularly relates to a method suitable for producing acrylic acid and methacrylic acid by gas phase catalytic oxidation of propane and isobutane, respectively.

[0002]

2. Description of the Related Art Unsaturated carboxylic acids such as acrylic acid and methacrylic acid are industrially important as raw materials for various synthetic resins, paints and plasticizers. As a method for producing acrylic acid, methacrylic acid or the like, a method in which an olefin such as propylene or isobutene is contact-reacted with oxygen in the gas phase at a high temperature in the presence of a catalyst is conventionally known as the most general method.

On the other hand, due to the price difference between propane and propylene, or the price difference between isobutane and isobutene, a lower alkane such as propane or isobutane is used as a starting material, and gas phase contact is carried out in the presence of a catalyst. There is increasing interest in developing a method for producing acrylic acid and methacrylic acid in a single step by an oxidation reaction. As an example of a catalyst for producing acrylic acid by performing a gas phase catalytic oxidation reaction of propane, Mo-Sb-PO catalyst (European Patent No. 00)
No. 10902), a VP-Te-O-based catalyst (Journ
al of Catalysis, vol. 101, p
389 (1986)), Bi-Mo-O based catalyst and V
A -P-Te-O-based catalyst (JP-A-3-170445) is known. On the other hand, as an example of a catalyst for producing methacrylic acid in a single step by subjecting isobutane to a gas phase catalytic oxidation reaction, P- Mo-O based catalyst (Japanese Patent Application Laid-Open No. 63-14 / 1988)
No. 5249) is known.

[0004]

However, none of the methods using these catalysts has a satisfactory yield of the desired unsaturated carboxylic acid or the reaction system is complicated. Has the disadvantage of

[0005]

The present inventors have conducted various studies on a method for producing an unsaturated carboxylic acid using an alkane such as propane or isobutane as a raw material.
In the presence of a catalyst containing a composite metal oxide composed of vanadium, tellurium and a certain metal, the above-mentioned problems have been solved by subjecting an alkane such as propane or isobutane to a gas-phase catalytic oxidation reaction. The inventors have found that the desired unsaturated carboxylic acids such as acrylic acid and methacrylic acid can be produced in high yield, and have reached the present invention.

That is, the gist of the present invention is that Mo, V, Te,
O and X (X is niobium, tantalum, tungsten,
Titanium, aluminum, zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel,
Palladium, platinum, antimony, bismuth, boron, one or more elements selected from the group consisting of indium and cerium) as essential components, and the proportion of each essential component to the total of the above essential components excluding oxygen is The following formula

[0007]

[Number 2] _{0.25 <r Mo <0.98 0.003 <} r V <0.5 0.003 <r Te <0.5 0.003 <r X <0.5

(Where r _Mo , r _V , r _Te and r _X are
Mo with respect to the sum of the above essential components excluding oxygen,
(Representing the mole fraction of V, Te and X) in a gas phase catalytic oxidation reaction of an alkane in the presence of a catalyst containing a composite metal oxide.

Hereinafter, the present invention will be described in detail. The composite metal oxide used as a catalyst component in the present invention is Mo,
V, Te, O and X (X is niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium,
Nickel, palladium, platinum, antimony, bismuth,
One or more elements selected from the group consisting of boron, indium and cerium). Among the above elements X, niobium, tantalum, tungsten and titanium are preferable, and niobium is particularly preferable.

The proportion of each essential component to the total of the above essential components excluding oxygen is given by the following formula:

[0011]

[Number 3] _{0.25 <r Mo <0.98 0.003 <} r V <0.5 0.003 <r Te <0.5 0.003 <r X <0.5

(Where r _Mo , r _V , r _Te and r _X are
M to the sum of the above essential components excluding oxygen
o, V, Te, and X). For example, the empirical formula of the composite metal oxide is M
_{o a V b Te c X (} 1) d X (2) e O n ( however, X
(1) and X (2) both represent an element belonging to the above element X).

[0013]

R _Mo = a / (a + b + c + d + e) r _V = b / (a + b + c + d + e) r _Te = c / (a + b + c + d + e) r _X = (d + e) / (a + b + c + d + e)

## EQU1 ## Among these molar ratios, the following formulas are particularly preferable.

[0015]

[Number 5] _{0.35 <r Mo <0.87 0.045 <} r V <0.37 0.020 <r Te <0.27 0.005 <r X <0.35

The range is preferred. Further, the composite metal oxide preferably has a specific crystal structure.
Specifically, as a pattern of an X-ray diffraction peak (using Cu-Kα ray as an X-ray source) of the composite metal oxide, the following five main diffraction peaks at a specific diffraction angle 2θ are observed. It is.

[0017]

X-ray grating plane diffraction angle 2θ (± 0.3 °) Median interval (Å) Relative intensity 22.1 ° 4.02 100 28.2 ° 3.16 20-150 36.2 ° 2. 485 5-60 45.2 ° 2.00 2-40 50.0 ° 1.82 2-40

The X-ray diffraction peak intensity may deviate depending on the measurement conditions of each crystal. The relative intensity when the peak intensity at 2θ = 22.1 ° is 100 is usually in the above range. In general, 2θ = 22.1 ° and 28.2
° peak intensity is large. However, as long as the above five diffraction peaks are recognized, even if there are peaks other than the five diffraction peaks, the basic crystal structure does not change,
It can be suitably used in the present invention.

The method for preparing the above composite metal oxide is as follows. For example, a composite metal oxide M in which the element X is Nb
When preparing _{o a V b Te c Nb x} O n, to an aqueous solution containing a predetermined amount of ammonium metavanadate salt, an aqueous solution of telluric acid, an aqueous solution of ammonium niobium oxalate salt and a solution or slurry of ammonium paramolybdate salt The metal elements are sequentially added at a ratio such that an atomic ratio of each metal element becomes a predetermined ratio, and dried by an evaporation to dryness method, a spray drying method, a vacuum drying method, and the like.
It is fired at a temperature of 50 to 700 ° C, preferably 400 to 650 ° C, usually for 0.5 to 30 hours, preferably for 1 to 10 hours to obtain a target composite metal oxide.

The above calcination can be carried out in an oxygen atmosphere, but it is preferable to carry out the calcination in the substantial absence of oxygen. Specifically, it is performed in an atmosphere of an inert gas such as nitrogen, argon, and helium, or in a vacuum.
It should be noted that the raw materials of the composite metal oxide are not limited to those described above, and may be, for example, MoO ₃ , V ₂ O ₅ ,
Oxides such as ₂ O ₃ , TeO ₂ , Nb ₂ O ₅ , MoCl
₅ , halides or oxyhalides such as VCl ₄ , VOCl ₃ , NbCl ₅ , Mo (OC
_{2 H 5) 5, Nb (} OC 2 H 5) 5, VO (OC
₂ H _{5) 3,} an alkoxide such as molybdenum acetylacetonate, an organometallic compound, or the like can be used widely.

The composite metal oxide thus obtained has excellent catalytic activity as it is, but a more active catalyst can be obtained by pulverizing the composite metal oxide. The above-mentioned pulverization method is not particularly limited, and a known general method is employed. Examples of the dry pulverization method include a method using an airflow pulverizer that causes pulverization by collision of coarse particles under a high-speed airflow.In addition, in addition to mechanical pulverization, a small-scale mortar or the like is used. A method of pulverizing by using can also be adopted.

As a wet pulverization method in which water or an organic solvent is added to the above-mentioned composite metal oxide in a wet state, a method using a usual cylindrical rotary type medium pulverizer, a medium stirring type pulverizer or the like is carried out. The cylindrical rotary medium pulverizer is a wet pulverizer that rotates a container containing a pulverizing medium, and includes a ball mill, a load mill, and the like. The medium stirring type pulverizer refers to a wet type pulverizer in which a pulverizing medium contained in a container is stirred by a stirrer, and includes a screw rotary type, a disk rotary type and the like.

The conditions of the pulverization may be appropriately set in accordance with the properties of the above-mentioned composite metal oxide, the viscosity and the concentration of the solvent used in the case of wet pulverization, and the optimum conditions of the pulverizing apparatus. It is preferable to pulverize the catalyst precursor until the average particle diameter is usually 20 μm or less, particularly 5 μm or less. This is because remarkable improvement in catalyst performance is recognized by pulverizing to such a range.

In some cases, it is possible to further increase the activity as a catalyst by adding a solvent to the above-mentioned once-crushed catalyst precursor to form a solution or slurry and then drying it again. It is. The concentration of the solution or slurry is not particularly limited, and is adjusted to a solution or slurry in which the total amount of the pulverized raw material compounds of the catalyst precursor is usually 10 to 60% by weight. Next, this solution or slurry is spray-dried, freeze-dried, evaporated to dryness, vacuum-dried, etc.
Preferably, it is dried by a spray drying method. The same drying may be performed when wet pulverization is performed.

Further, the catalyst which has been dried or pulverized as described above may be finally used as a catalyst.
The heat treatment may be performed for about 0 hours. The composite metal oxide thus obtained is used alone as a solid catalyst, but may be used as a catalyst with a suitable carrier, for example, silica, alumina, titania, aluminon silicate, diatomaceous earth, zirconia, or the like. it can. Further, it is molded into an appropriate shape and particle size according to the scale and system of the reaction. The method of the present invention is to produce an unsaturated carboxylic acid by subjecting an alkane to a gas-phase catalytic oxidation reaction in the presence of a catalyst containing the above-mentioned composite metal oxide.

In the present invention, the alkane as the raw material has 3 or more carbon atoms, and lower alkane, particularly propane and isobutane are preferred. According to the method of the present invention, unsaturated carboxylic acids such as α, β-unsaturated carboxylic acids can be obtained from these alkanes in high yield. For example, when propane or isobutane is used as a raw material, acrylic acid or methacrylic acid can be obtained in high yield.

Although the details of the mechanism of the oxidation reaction in the present invention are not clear, the oxidation reaction is carried out by oxygen atoms present in the composite metal oxide or molecular oxygen present in the supply gas. When molecular oxygen is present in the feed gas, the molecular oxygen may be pure oxygen gas, but since purity is not particularly required, it is generally economical to use an oxygen-containing gas such as air. As a supply gas, a mixed gas of a raw material alkane and an oxygen-containing gas is usually used, but the raw material alkane and the oxygen-containing gas may be alternately supplied to the reaction system.

It is also possible to carry out a gas phase contact reaction using only an alkane containing substantially no molecular oxygen as a supply gas. In such a case, a method is preferable in which a part of the catalyst is appropriately extracted from the reaction zone, the catalyst is sent to an oxidation regenerator, and after regeneration, the catalyst is resupplied to the reaction zone. As a method for regenerating the catalyst, for example, an oxidizing gas such as oxygen, air, or nitric oxide is usually supplied to the catalyst in the regenerator in a range of 300 to 600.
And a method of circulating at about ° C.

The present invention will be described in more detail in the case where propane is used as a raw material alkane and air is used as an oxygen source. The reaction system may be a fixed bed, a fluidized bed, or the like. However, since the reaction is an exothermic reaction, the fluidized bed system is easier to control the reaction temperature. The proportion of air supplied to the reaction is important with respect to the selectivity of the acrylic acid to be produced, and is usually not more than 25 times the amount of propane, especially 0.1 mol.
The range of 2 to 18 mole times indicates high acrylic acid selectivity. This reaction is usually carried out under atmospheric pressure, but can also be carried out under low pressure or low pressure. For other alkanes such as isobutane, the composition of the feed gas is selected according to the conditions for propane.

In the method of the present invention, the reaction temperature is usually 3
The temperature is about 00 to 480 ° C, preferably about 350 to 440 ° C, so that unsaturated carboxylic acids can be produced in a higher yield than conventional techniques. The gas space velocity SV in the gas phase reaction is usually 100～10,000Hr ^-1, preferably in the range of 300~2,000hr ^-1. Note that an inert gas such as nitrogen, argon, or helium can be used as a diluent gas for adjusting the space velocity and the oxygen partial pressure.

When propane is oxidized by the method of the present invention, carbon monoxide, carbon dioxide, acetic acid and the like are produced as by-products in addition to acrylic acid, but the amount of the produced is extremely small. In the method of the present invention, an unsaturated aldehyde may be produced depending on the reaction conditions. For example, when propane is used as a raw material, acrolein can be produced, and when isobutane is used as a raw material, methacrolein can be produced. In this case, these unsaturated aldehydes are subjected to the gas-phase catalytic oxidation reaction again using the composite metal oxide-containing catalyst used in the present invention, or to the gas-phase catalytic oxidation reaction using a known unsaturated aldehyde oxidation reaction catalyst. It can be converted to the desired unsaturated carboxylic acid.

[0032]

EXAMPLES Hereinafter, specific embodiments of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples unless it exceeds the gist thereof. The conversion rate (%) of propane, the selectivity (%) of acrylic acid, and the yield (%) of acrylic acid in the following Examples are respectively represented by the following formulas.

[0033]

## EQU00006 ## Conversion of propane (%) = (moles of propane consumed / moles of supplied propane) .times.100 Selectivity of acrylic acid (%) = (moles of acrylic acid produced / moles of propane consumed) × 100 Acrylic acid yield (%) = (mol number of acrylic acid produced /
Number of moles of propane supplied) x 100

[0034] was prepared composite metal oxide having a first embodiment empirical formula _{Mo 1 V 0.3 Te 0.23 Nb 0.12} O n as follows. 325 ml of warm water
Was dissolved in 15.7 g of ammonium metavanadate, and 23.6 g of telluric acid and 78.9 g of ammonium paramolybdate were sequentially added thereto to prepare a uniform aqueous solution.
Further, 117.5 g of an aqueous niobium ammonium oxalate solution having a niobium concentration of 0.456 mol / kg was mixed to prepare a slurry. The slurry was subjected to a heat treatment to remove water and obtain a solid. This solid was molded into 5 mmφ × 3 mmL using a tablet molding machine, and then crushed.
The mixture was sieved to 6 to 28 mesh and calcined at 600 ° C. for 2 hours in a nitrogen stream.

The composite metal oxide thus obtained was subjected to powder X-ray diffraction measurement (using Cu-Kα ray). As a result, the diffraction angle 2θ was 22.1 ° (100),
8.2 ° (57.3), 36.2 ° (16.9), 4
A major diffraction peak was observed at 5.1 ° (15.2) and 50.0 ° (10.1) (the number in parentheses is 2θ =
The relative peak intensity when the peak intensity at 22.1 ° is 100 is shown). 0.37 g of the composite metal oxide thus obtained was charged into a reactor, the reaction temperature was 400 ° C., the space velocity was SV1,734 hr ⁻¹ , and propane: air = 1: 15.
, And a gas phase contact reaction was carried out. The results are shown in Table 1.

Example 2 A reactor was charged with 0.37 g of the composite metal oxide obtained in Example 1, and the reaction temperature was 380 ° C. and the space velocity was SV1,734 hr.
⁻¹ , propane: air: nitrogen = 1: 7.5: 7.5 gas was supplied at a molar ratio to perform a gas phase contact reaction. The results are shown in Table 1.

Example 3 30 g of the composite metal oxide obtained in Example 1 was ground in a mortar, and 0.6 g of bismuth hydroxide was further added and mixed. This mixture was molded into a size of 5 mmφ × 3 mmL using a tablet molding machine, pulverized, sieved to 16 to 28 mesh, and calcined at 550 ° C. for 2 hours in a nitrogen stream. 0.37 g of the catalyst thus obtained was charged into a reactor, and the reaction temperature was 380 ° C.
Space velocity SV1,854 hr ^-1 , propane: air = 1:
A gas was supplied at a molar ratio of 15 to perform a gas phase contact reaction. The results are shown in Table 1.

[0038]

[Table 3]

[0039]

According to the method of the present invention, the desired unsaturated carboxylic acid can be produced in a high yield from the alkane as a raw material by a one-step method.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-170445 (JP, A) JP-A-4-59738 (JP, A) JP-A-4-59739 (JP, A) JP-A-4-59739 128247 (JP, A) JP-B-43-24645 (JP, B1) JP-B-43-24644 (JP, B1) JP-B-47-44203 (JP, B1) JP-B-45-5247 (JP, B1) JP-B-45-37306 (JP, B1) (58) Field surveyed (Int. Cl. ⁷ , DB name) C07C 57/05

Claims (3)

(57) [Claims] 1. Mo, V, Te, O and X (X is niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, antimony, (Indicating one or more elements selected from the group consisting of bismuth, boron, indium and cerium) as an essential component, and the proportion of each essential component to the total of the above essential components excluding oxygen is represented by the following formula: 0.25 <r _Mo <0.98 0.003 <r _V <0.5 0.003 <r _Te <0.5 0.003 <r _X <0.5 (provided that r _Mo , r _V , r _Te and r _X are the presence of a catalyst containing a mixed metal oxide satisfying Mo, represents V, and the molar fraction of Te and X) to the total of the essential components, respectively, except for oxygen, gas phase alkanes Method for producing an unsaturated carboxylic acid, characterized in that to touch the oxidation reaction. 2. The composite metal oxide has an X-ray diffraction line (Cu-
The method for producing an unsaturated carboxylic acid according to claim 1, wherein an X-ray diffraction peak is shown at a diffraction angle 2θ shown in the following table in the case of using a Kα ray). [Table 1] 3. The method for producing an unsaturated carboxylic acid according to claim 1, wherein a catalyst produced by a method including a step of pulverizing the composite metal oxide is used.