JPS6128456A - Catalyst for preparing pyromellitic anhydride - Google Patents

Abstract

PURPOSE:To obtain a catalyst for preparing pyromellitic anhydride, by supporting catalystically active components such as vanadium, tin, titanium, phosphorus, niobium, alkali metal oxide or antimony by an inert carrier. CONSTITUTION:As a catalyst for peparting pyromellitic anhydride by the catalyst gaseous phase oxidation of durene or tetraalkyl benzene, 1-20pts.wt. of a vanadium component as V2O5, 99-80pts.wt. of a tin component and/or a titanium component as SnO2+TiO2, 0.02-10pts. by wt. of the sum of both components of a phosphorus component as P2O5, 0.01-5pts.wt. of a niobium component as Nb2O5, 0-1.2pts.wt. of potassium as oxide and 0-10pts.wt of an antimony component as Sb2O5 are supported by an inert carrier. This catalyst prepares pyromellitic acid at high yield in a region low in a special speed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention produces pyromellitic acid or anhydride by catalytic gas phase oxidation of Durene or tetraalkylbenzene containing an alkyl group having a vertical prime number of 4 or less with air or molecular oxygen-containing gas. The present invention provides a catalyst suitable for producing pyromellitic acid.

BACKGROUND ART Various methods have been proposed for producing pyromellitic acid or pyromellitic anhydride, including liquid phase oxidation of tetraalkylbenzene containing duurene, liquid phase nitric acid oxidation, catalytic gas phase oxidation, and hydrolysis of dicyano terephthalate. Catalytic gas phase oxidation is one of the most promising processes with various industrial advantages, although many proposals have been made to date, with very unsatisfactory results in terms of yield and conditions of use. give. In particular, the conditions for using the catalyst are as follows:
The disadvantage in industrial use is that the volume ratio is very low at 5 to 0.33 and the space velocity of the reactant gas is very high. Even under the oxidation conditions described in the examples of Japanese Patent Publication No. 52-3931, etc., the ratio of durene/air is approximately lθ~20 f/NM” (0,1
5 to 0.33% by volume), the concentration of Duurene in the raw material gas is low, and the space velocity of the raw material gas is also 8.000 to 15.000.
Hr-”, which is very high.

Problems to be Solved by the Present Invention As mentioned above, under process conditions in which the oxidized substance is at a low concentration in the raw material gas and the space velocity of the raw material gas is high, one of the problems is that air or molecular Furthermore, the sensible heat carried away from the reactor of the oxygen-containing gas cannot be covered by the heat of the oxidation reaction of such a dilute Duurene, and therefore the oxidation reactor cannot stand on its own, requiring external heating. At first glance, a high space velocity seems to be industrially advantageous, but in industrial implementation of oxidation reactions, the height of the catalyst packed bed is substantially required to be 1 meter or more, preferably 1.5 meters or more. Under such a high space velocity, the linear velocity of the gas within the reaction tube is high, resulting in an abnormally high pressure loss in the catalyst layer, which is disadvantageous.

That is, catalytic oxidation at high space velocities and low concentrations is not economical, as it requires an increase in the amount of steam or electricity for the turbine or motor to drive the blower or compressor, and also increases the energy of the heating source. That's not to say there isn't.

Therefore, the object of the present invention is to achieve a space velocity of 2000 to 6.0OO.
In a relatively low Hr-” region, the amount of tetraalkylbenzene/air or molecular oxygen-containing gas is higher than that of conventional methods.
It is an object of the present invention to provide a catalyst for producing pyromellitic anhydride and/or pyromellitic acid in high yield under conditions of ˜60y/NM''.

Means for Solving the Problems In order to solve these problems, the present inventors, Hiro and others, investigated improvements to various catalysts and found that the combination of vanadium pentoxide (VzOs) and tin dioxide (SnOz) Niobium pentachloride (Nb20s) and phosphorus pentoxide (
The object of the present invention is to provide a catalyst in which an inert carrier supports a catalytically active substance consisting of a l component selected from the group consisting of PzOs), potassium, cesium, rubidium, and thallium, and an oxide (MeO2) of a higher oxidation level. I found that it fits.

Furthermore, it has been found that even if a part of SnO2+TiO2 is replaced with TtOi, the object of the present invention can be achieved as much as or even better than the V@Os/SnO2-based catalyst.

In addition, the above-mentioned VzOs/SnOx system or v! It has also been found that by adding an appropriate amount of S b z Os to the 0@/S n 02 /T i O2-based catalyst, the catalyst can operate more effectively in a lower temperature range.

To describe the catalyst of the present invention in more detail, (1)
The vanadium component is V2O, 1 to 20 parts by weight, preferably 1 to 10 parts by weight, and the tin component or the tin and titanium components are 99 to 8 as SnO2+TiO2+Tt02.
0 parts by weight, preferably 99 to 90 parts by weight, the phosphorus component is 0 as P*Os relative to the total of 100 parts by weight of the above components.
．． 02 to 10 parts by weight of the niobium component, 0.01 to 5 parts by weight as N b 20 s, and 0 to 1.0 parts of at least one component selected from the group consisting of potassium, cesium, rubidium, and thallium as an oxide. For the production of pyromellitic anhydride by catalytic gas phase oxidation of durene or tetraalkylbenzene, comprising a catalytically active material containing 2 parts by weight and 0 to 10 parts by weight of an antimony component in the form of S b x Os, supported on an inert carrier. catalyst, and (2) the weight ratio of tin component and titanium component is Tie, /
The above (which is characterized in that S nOz = 4 or less)
1) Identified as the catalyst described above.

In addition, the present inventors have discovered that the above 0VzOs
5no2 or vxOs-Sn02/T
In a multicomponent catalyst in which the above promoter is added to the tOz system, V2O1i and SnO2 or T[02/Sn
The catalyst obtained by adding 0.1 to 10 parts by weight, especially 0.5 to 5 parts by weight of S b 20 s to 100 parts by weight in total of 02 has a 20 to 30
It was discovered that the optimum reaction temperature can be lowered in °C, and a catalyst that is advantageous in terms of catalyst life has been completed.

Raw materials such as nitrates, carbonates, sulfates, and organic acid salts of each element constituting the catalyst are prepared, which are oxidised by heating and converted into their respective oxides. However, 5no2 is produced by baking tin salts such as sulfates, nitrates, and carbonates at an appropriate temperature.
It is preferable to use nO2+TiO2 powder as the starting material.

Particularly preferably, stannous sulfate is heated at 600 to 900°C.
The average particle size obtained by firing for ~10 hours is 0.01~1 micron, the specific surface area is 5~100 m''/f, especially 8~6
o? F+2/l SnO2 is used as catalyst raw material. It is preferable that TiOz is also made from anatase-type TtO* powder obtained by heat-treating a titanium compound in advance as a starting material, and particularly preferably, it is obtained by dissolving ilmenite in sulfuric acid and introducing heated steam into the solution to precipitate it. The average particle size obtained by firing hydrous titanium oxide at a temperature of 600 to 900°C for 2 to 10 hours is substantially 0.4 to 0.7 microns,
Is the specific surface area 5-100? FI”/l% especially 10
~60 m''/f porous anatase TtOz powder is used.

Any ordinary inert carrier can be used as the carrier, but preferably, the apparent porosity is 5 to 50, and the specific surface area is 57F! 2/ f or less, especially 1m27?
The following aluminum content is 10% by weight or more, especially 3
Below weight ratio, SiC content is 50 weight board, especially 8
An inorganic porous carrier of 0% by weight or more is used, and the shape of the carrier is not particularly limited, and may be a sphere, a ring,
Cylindrical, conical, or poudre-shaped, with an average outer diameter of 3 to 15 mm.
A material of about m is used as appropriate.

The method of supporting the catalytically active substance on the carrier is carried out by a conventionally known method, such as a spraying method, an impregnation method, etc., but it is preferable to apply a catalyst liquid or a catalyst to a carrier heated to a temperature of 150 to 250°C. The catalytically active substance is supported by spraying the slurry liquid.

3 to 3 for the apparent volume of 1000C of the catalytically active material carrier
50f1, preferably 5 to 15F is supported. The catalyst thus obtained is calcined under air flow at a temperature of 300 to 650°C, preferably 400 to 600°C, for 1 to 10 hours, preferably 2 to 6 hours.

7' W-rene Also, since the reaction rate from tetraalkylbenzene to pyromellitic acid or pyromellitic anhydride is very fast,
When operating with a high proportion of molecular oxygen-containing gas, most of the reaction proceeds in the first half of the catalyst layer, resulting in a high hot spot (hot 5pot) in that region, reducing selectivity and at the same time increasing the catalyst's efficiency. Accelerate deterioration. For this reason, the reaction at that site can be prevented by conventionally known means such as diluting the first half of the catalyst layer with a carrier, reducing the amount of catalytically active material supported, increasing the particle size of the catalyst, or suppressing the catalytic activity. Catalysts can be used in such a way that the amount of heat is reduced and the temperature at the hot spot becomes less loud. Catalytic activity can be controlled by changing the vanadium content,
The alkali metal content and the phosphorus content can be changed, or the relative area of SnO2+TiO2 or Ti0z used can be changed as appropriate.

Functionality The catalyst thus obtained is used by being packed in a multitubular reaction tower surrounded by a heating medium such as a molten salt, and the temperature of the heating medium is 340 to 440°C, particularly 360 to 400°C. The reaction tube is maintained at a temperature of 15 to 40 mm, preferably 20 to 30 mm.

The catalyst is packed to a bed height of 1 to 3.5 meters, especially 1.5 to 3 meters, and is filled with a molecular oxygen-containing gas consisting of air or oxygen concentration of 10 to 21 volume parts and water vapor θ to 15 volume parts of inert gas. 20 to 6 of Duurene or tetraalkylbenzene.

t/NM” - mixed at a ratio of molecular oxygen-containing gas 120
Gas preheated to ~160°C at a space velocity of 2.000~6
,000 hours for catalytic oxidation.

Anhydrous pyromellit can be obtained with a yield of 1) 0 to 120% by weight. The effectiveness will be explained in more detail with examples.

Example 1 Stannous sulfate was thermally decomposed at 800°C for 4 hours to reduce the specific surface area to 1
Snow of 8 m''/l was obtained. This was air-pulverized to obtain Snow with an average particle size of 0.18 microns, which was used as a catalyst raw material.

Dissolve 200 f of oxalic acid in 6400 cc of water, and add 121.8 f of ammonium metavanadate to this.

Diammonium phosphate 15.35F, niobium chloride 19
．． 27 f and 5.249 g of cesium nitrate were added and thoroughly stirred. The above Sn0.18001F was added to this, and a catalyst slurry liquid was prepared using an emulsifier.

Average diameter 5 with apparent porosity 42% in externally heated rotary furnace
■, Pellet-like SiC self-sintering carrier with an average length of 6 pieces (specific surface area 0.4 m”/f) was put into 2000 pieces of 150~2
Preheated to 00°C. The above catalyst slurry was sprayed on this to support 180% of the catalytically active substance, and then 5% of the catalyst slurry was applied under air circulation.
The catalyst was calcined at a temperature of 50° C. for 6 hours to obtain a catalyst.

On the other hand, the amount of dibasic ammonium phosphate added was 27.63
Catalyst-B was prepared in the same manner as catalyst-A except that t was changed.

Internal diameter 251) immersed in a molten salt bath held at 410°C
1) Catalyst-B was first placed in an iron reaction tube with a length of 3.5 meters.
was packed to a height of 1.5 meters, and then the catalyst was packed above it to a height of 1.5 meters.

At the top of the reaction tube, the siderene/air ratio is 30f/NM.
The mixed gas is preheated to 140℃ and the space velocity is 4.000.
1) Pyromellitic anhydride was obtained in a yield of 3.4 weight tons.

Example 2 Dissolve 200 cc of hydrochloric acid in 5 oocc of water, and add 10 f1 of vanadium pentoxide, 1.6 cc of monoammonium phosphate,
2 F and 0.28 t of potassium sulfate were added and thoroughly stirred. To this, 42.74 t of stannous sulfate and 60 t of porous anatase type TtOx having an average particle diameter of 0.5 microns and a specific surface area of 20 m''/f were added, and a catalyst slurry liquid was prepared using an emulsifier.

The above catalyst slurry was placed in an evaporation dish that could be heated externally, with an apparent porosity of 48, a specific surface area of 0.3 m''/t, an aluminum content of 8% as AtzOs, and a Si
A spherical porous carrier having an average diameter of 6 m and having a C content of 75% and StO, ty% was added at 1000Ω, and while stirring the carrier, the catalytically active substance was concentrated and deposited at 160f, and then
It was baked at a temperature of 80° C. for 8 hours.

The catalyst prepared in this manner was packed into a reaction tube with an inner diameter of 20 m+ maintained at 405°C to a bed height of 2.5 m, and a mixed gas having a Duurene/air ratio of 40 f/NM was charged at a space velocity of 3. ,000Hr-” 1) 2
．． Pyromellitic anhydride was obtained with a yield of 1% by weight.

Example 3 Melon #120F was dissolved in 6400C1m of water, and VIOs 55.7f, NbCl1) 56.1
? , diammonium phosphate (9.02 f%), rubidium sulfate (7.21 P), thallium sulfate (2.33 f), and powdered antimony oxide (SbzOs) (55.7 y) were added and thoroughly stirred. To this were added SnO2+TiO2930F obtained in the same manner as in Example 1 and TtO, 870f obtained in the same manner as in Example 2, and an emulsifier was used to prepare a catalyst slurry.

Apparent porosity 40, average outer diameter 7 in an externally heated rotary furnace
m1 average inner diameter 4 m, average length 7 scales, its composition is magnesium oxide (MgO) x O%, Sing 20 and 5
2.000 CC of a porous ring-shaped carrier made of 70% iC (all percentages by weight) was placed and preheated to 150 to 200°C. The above slurry was sprinkled on this, and 15% of the catalytically active material was added.
Catalyst-C was obtained by supporting 0 and calcining it at a temperature of 500° C. for 4 hours under air flow.

On the other hand, catalyst -0 was obtained in the same manner as in the case of catalyst -0, except that rubidium nitrate and thallium sulfate were added little.

I.D. 25- immersed in a molten salt bath held at 380°C.
1. First, 1 portion of catalyst-D was added to a 3.5 meter long iron reaction tube.
A bed height of 1 meter was then filled with Catalyst-C above it to a bed height of 1 meter.

Durene/molecular oxygen-containing gas (oxygen i) is introduced from the top of the reaction tube.
o%, water vapor 10%, N2 balance) ratio is 40f/
NM" mixed gas at a space velocity of 3.500 Hr-1
1) Pyromellitic anhydride was obtained in a yield of 7.3% by weight.

Effects of the Invention As shown in Examples 1 to 3, the conventional catalyst has a very low ratio of durene/molecular oxygen-containing gas (including air) of 10 to 2 ot/NM'' under its usage conditions, and is a very dilute coating. The oxide concentration was 20~20 for the catalyst of the present invention.
It maintains its activity effectively in a very high concentration range of 40 f/NM'.

The space velocity is also lower than that of conventional catalysts at 3,000 to 4,000 Hr-1, and the energy required for air preheating and blowing energy in industrial use of the catalyst is significantly reduced.

Of course, using the catalyst of the present invention for 5,000 to 8,000 Hr-1
Needless to say, it is possible to use it at such a spatial velocity.

However, if the space velocity is 3,000 to 4,000 Hr −
1, the space-time yield (S, T, Y,) of pyromellitic acid or pyromellitic anhydride is 120 to 175 f/
It is clear that in L-Cat-Hr, the ratio of durene/molecular oxygen-containing gas is high, so that a rather high level is maintained compared to conventional catalysts.

Claims (2)

[Claims] (1) The vanadium component is 1 to 20 parts by weight as V_2O_5, and the tin component or the tin and titanium components are SnO_
99 to 80 parts by weight as 2+TiO_2, and 0 phosphorus component as P_2O_5 for the total 100 parts by weight of the above components.
．． 02 to 10 parts by weight, the niobium component is 0.01 to 5 parts by weight as Nb_2O_5, and at least one selected from the group consisting of potassium, cesium, rubidium, and thallium.
Catalytic gas-phase oxidation of durene or tetraalkylbenzene in which a catalytically active material containing 0 to 1.2 parts by weight of a seed component as an oxide and 0 to 10 parts by weight of an antimony component as Sb_2O_3 is supported on an inert carrier. catalyst for the production of pyromellitic anhydride. (2) The weight ratio of tin component and titanium component is TiO_2/S
The catalyst according to claim (1), characterized in that nO_2 = 4 or less.