DE1168889B - Process for the preparation of terephthalic acid - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Cl .: C 07 c;

Number:
File number:
Registration date:
Display day:

C07b

German KL: 12 ο -14

M 45383 IVb / 12 ο
May 21, 1960
April 30, 1964

Terephthalic acid has already been made from other benzene carboxylic acids. Either Potassium or thallium salts of benzenecarboxylic acids containing at least three carboxyl groups contained, or mixtures thereof, heated to temperatures above about 300 ° C. From the implementation mixture could then terephthalic acid by adding solvents or by acidification or their salts are obtained. The heating also took place under pressure and in the presence of carbon dioxide. Metal oxides, especially iron oxides, were used as catalysts Ceria or manganese dioxide is used. The process could also be carried out in the fluidized bed will.

According to another known process, alkali salts of Benzoic acid in a mixture with the alkali salts of benzene polycarboxylic acids, which have more than two carboxyl groups contained in the molecule, processed in the same way. This occurred in the fluidized bed or agglomerations in the rotary kiln, which one tried to remove by adding solid substances such as sand, To prevent coke grit or metal shavings. Terephthalic acid is also produced by heating salts of phthalic acid, ζ. B. alkali or thallium salts, to temperatures between about 400 and 350 ° C under normal pressure or elevated pressure in the presence of carbon dioxide and using Catalysts have been produced. The melting occurred at temperatures of about 350 ° C Phthalates, the reaction mixture then again to the extent that terephthalate was formed, froze. This process had the disadvantage that the melting of the reaction mixture and the subsequent formation of stone-like Product could not be avoided, so that the implementation known for the first-mentioned process were not applicable to the reaction. For this reason, the implementation of salts was the Phthalic acid to terephthalic acid salts either carried on electrically heated belts, or it the starting mixture was pressed through externally heated pipes. This way of working was cumbersome, required long reaction times and still led to low yields.

A process is also known, a reaction of 400 kg / h of dipotassium terephthalate with a catalyst in a fluidized bed initially made up of 30 kg of dipotassium terephthalate to terephthalate to effect. However, as has been found, these throughput figures can be used in practical operation Process for the production of terephthalic acid

Applicant:

Metallgesellschaft Aktiengesellschaft,
Frankfurt / M., Reuterweg 14

Named as inventor:

Dr.-Ing. Wilhelm Herbert, Frankfurt / M.,
Dr.-Ing. Oskar Dorschner,
Bad Homburg vd Höhe

not maintained over a long period of time, because after about 5 to 10 minutes as a result of grain enlargement the fluidization comes to a standstill due to agglomeration.

The invention now shows a way of doing this known, but so far practically not in a continuous way To make operational feasible procedures useful for practical purposes. Essentially this is achieved by the fact that the proportion of terephthalate in the fluidized bed during the the entire duration of the treatment is kept above a certain minimum value. This minimum value is 70% and is preferably between 70 and 80%. An additional mechanical Stirring makes it possible to set the proportion of terephthalate to the lower limit of 70% with certainty keep. If you are working without mechanical agitation, it is advisable to slightly reduce the proportion of terephthalate higher, d. H. between 70 and 80%.

Because the achievable throughput depends on the content of the starting materials in the fluidized bed is approximately proportional, it is useful to determine the proportion of the starting materials in the solids content of the To keep the fluidized bed as high as possible in any case, but according to the invention the critical Limit of about 30% should not be exceeded.

According to the invention, the alkali metal salts of other benzene carboxylic acids than terephthalic acid, z. B. from alkali salts of phthalic acid and / or isophthalic acid existing starting material together with the catalyst in a fluidized bed under normal or elevated pressure of, for. B. 10 to 50 atm and there in intimate mixture with the stated amounts of alkali salts of terephthalic acid as it is a direct product of the process.

409 587/499

3 4

As a result, agglomerations of the fine particles of the eddy material are discharged and according to known ones

or granular starting materials to disruptive lumps, processes, e.g. B. by acidification from this the ter-

Approaches or similar structures prevented. obtained from phthalic acid. After the discharge

If sticking is avoided, this 10% will again be 10 ⁰ Zo phthalate in the

the advantage of a thoroughly even heating 5 reaction device introduced. Kick it

achieved, which is the prerequisite for a change of difficulties by sticking the individual

formation with high yield. In addition, particles of that located in the device

If there is no need for the product to be used, this can be done safely in all cases

driving to subject to a comminution, which for avoiding that the reaction temperature in

further processing is unavoidable. io of the device before the entry of the new batch

For example, a salt or a salt mixture of phthalic acid or isophthalic acid or is lowered to about below the melting temperature of the phthalates. During and after the introduction of a salt mixture of both acids, to which the catalyst of the batch is first added an intimate mixing, in a mixture with the product of the freshly added goods with the in the Vorneuen process or with one or more goods already present in the direction carried out and the same or different kind of obtained salts thereupon the temperature gradually increased to the reaction terephthalic acid at a reaction temperature of temperature of about 400 to 440 ° C and treated about 380 to 440 ° C. This mixture conversion of the goods is brought to an end before a component is given up in the following briefly with a new batch of reaction. Are designated during the product. The proportion of fresh phthalate 20 entrained dust losses of phthalate to fear in the mixture with the reaction product should only be th, this can be prevented by being so great that the gas velocity in the fluidized bed during the reaction to about a melting phthalate of the submitted reac - Fifth of the normal size is reduced and is only completely absorbed after the product is tioned, so that no incrustations or adhesions occur again after the fresh goods have been completely smuggled in. 25 is brought to the old height.
As useful has z. B. a mixture of 5 to During the whirling operation, a fine 30% phthalate and 95 to 70% reaction product dust, which are expelled from the device with the gas. The amount of appropriate phthalate is carried. This fine dust can, before it is added to the fluidized bed, depending on the intensity of the device, again to a greater degree of mixing, which is pre-agglomerated for the fluidized bed if seen in good time. A freshly stirred phthalate can also be introduced into the fluidized bed. The phthalate facility will be used. The agitator has melted and is binding the dust. In addition to mixing, it is useful if the fresh phthalate is continuous or effective, so that there is slight caking of the short time intervals of 1 to 10 minutes with particles moving in the fluidized bed, which are not dispensed.

need to be closed, very completely destroyed. Another way to remove the phthalate without interference

disturbs. tion of the whirling process by gluing into the

In the procedure according to the invention to bring reaction equipment consists in that the individual grains of terephthalate are sticky through the intermediary of two fluidized beds connected one behind the other acting products to larger cores 40 is working. In the first fluidized bed that will agglomerated, but after or during the phthalate with the intended amount of reaction hardening as the process progresses already product at temperatures of 250 to 350 ° C, due to the well-known mill effect of the vortex - advantageously mixed at 300 ° C without layer can be comminuted again to such an extent that a noticeable reaction occurs. That their ability to fluidize is maintained, 45 well-mixed material is now from the first whirlwind the solids content of the fluidized bed brought into the second, in which at 380 to 440 ° C layer does not exceed 30%. the chemical rearrangement initiated and terminated

The implementation takes place as with the known ones.

Process in a carbon dioxide or inert gas in order to ensure an intimate and rapid mixing of the atmosphere, with the flow velocity of the reaction product and the freshly introduced Gekeit of the gas passed through the fluidized bed after mixing in the fluidized bed, it is advantageous to the pressure with which the fluidized bed operated is directed to the gas flow rate on the wall will. For example, under normal pressure and keep the reaction vessel larger than in the at 400 ° C a flow rate of about the middle of the same. This is the tendency of the 10 to 50 cm / second, based on the free transverse vortex particles, to migrate to the wall, counter-cut, maintain. At a pressure of about knitted and a whirling from the outside to the inside er-30 atü becomes the effective one, but also aims at the.

Free cross-section related flow rate for the method according to the invention can

speed decreased to about 2 to 15 cm / second. known catalysts are used, such as

The mixture of fresh phthalate and reac- 60 Cadium and zinc compounds, z. B. Oxides, ChIo-

tion product can be manufactured before it is turned into ride or carbonates. As salts of dicarboxylic acids,

the reaction vessel is given, or it can in particular the phthalic acid and isophthalic

also be worked in such a way that the phthalate in the acid, come mainly alkali salts, especially

correspondingly large z. B. ten times the amount of reactants the potassium salts in question,

tion product is introduced, which is already 65 To further explain the invention, the

in the fluidized state at reaction temperature in the drawings. In the A b b. 1 to 5 are different

Fluidized bed device is located. After termination of devices that are not subject to the protection

of the reaction will in the latter case again be 10% on the right, schematically and for example

that are suitable for practicing the invention.

Fig. 1 shows a schematic of the arrangement of a fluidized bed reaction apparatus and the associated one Furnishing.

The fluidized material is located in the device 1. The gas passes through the grate 2 in the device 1, flows through it from bottom to top and reaches a dust separator 3, which z. B. is designed as a cyclone. In the gas heater 4, the gas is reheated to the reaction temperature and conveyed back into the device by the fan 5. The fresh material is brought into the device through the lock 1 and taken out through the discharge lock 7 after the reaction time has elapsed. The dust accumulated in the dust separator is either conveyed back through the line 8 into the device 1 or passes through the line 9 directly into the discharge lock 7 Reaction temperature, e.g. B. at 250 to 350 ° C, before the batch entry of the fresh material, the gas stream exiting the device, after passing through the dust separator 3, is not passed through the gas heater 4, but through the cooler 10, in which it for example, is cooled from 400 to 300 ° C. The device 1 is now kept running at 300 ° C. until a fresh material charge has been completely introduced and has mixed with the reaction product located in the fluidized bed. The cycle gas is then passed through the gas heater 4 again and heated there to 400 ° C. while the cooler 10 remains switched off.

It has proven to be advantageous for the reaction device to be designed as an upwardly widening conically Train shaft. The conical widening reduces the flow velocity of the gas increasingly upwards, so that the fine fractions of the fluidized material in the upper part of the Device held in suspension and not removed with the gas flow. Will go up in the Reaction device with fresh material introduced, it begins to melt as it falls, takes here the fine dust that has accumulated in the upper part of the device with down and agglomerates it into larger particles. To avoid the softening and sticking of the fresh food in the To avoid sluice, the sluice, preferably the lower part of the same, will go into the device leads, chilled.

A b b. 2 and 2a show a rotating grate arranged in the fluidized bed device, with the finished one Reaction product can be discharged. In the device, the gas passes through the conical one Rust in the fluidized bed. The middle part of this grate is designed as a rotating grate 11, the can be moved by means of a gear drive 12 and a motor 13. The discharge of the reaction material can be done either continuously or in batches through this grate. The discharge lock is closed pressure-tight by two cones 14 and 15. By opening the cone 14 that runs Goods conveyed out of the fluidized bed by the rotating grate 11 into the lock. The cone 14 is now closed again and cone 15 after releasing the pressure in the lock, opened and the reaction mixture is again drained from the lock for further processing on terephthalic acid.

The conical design of the grate has the advantage that larger particles that agglomerate of the eddy material or larger lumps caused by malfunctions during operation can accumulate in the middle of the grate and through the rotating grate, if necessary after shredding, can be discharged, ίο To support the shredding of coarser particles the rotating grate 11 can also be provided with an agitator 16, which then also has the Can discharge fluidized material if the entire fluidized bed sintered together due to a malfunction should be.

An overflow pipe 17 is built into the reaction device 1 'according to FIG. 3 and ends just above the grate 2'. By means of a sleeve 18 that can be moved up and down, the space between the lower end of the overflow pipe 17 and the grate 1 'can be enlarged and reduced, depending on whether fine reaction material that has accumulated in the upper part of the reactor is to be withdrawn or, however, preferably the coarser reaction material which is located above the grate 2 '. If the cuff 18 is pushed up, the opening 19 of the grate is free and allows the coarse reaction material to pass through the closing cone 14 'into the lock T. If the cuff is pushed down, fine vortex material from the upper part of the device is preferred deducted.

Fig. 4 shows another embodiment of the reaction device for continuous input and Discharge of the reaction material. The lower part of the device 51 is cylindrical and has a small diameter, so that a high gas flow rate in the cylindrical part prevails. This lower part is followed by a cone at the top, which extends towards its upper end expanded evenly to three times the diameter. The device 51 contains an overflow pipe 20, which leads to the upper part of the device and, distributed along its length, several holes 52 contains. A second overflow pipe 21 ends at the upper end of the cylindrical part and leads together with the overflow pipe 20 in the discharge lock 22. The slide 23 and 24 allow the Complete overflow pipes against the discharge lock 22. The entry lock 25 for the fresh goods is arranged laterally. From here it will Fresh goods are continuously brought into the device 51 by means of a screw 26. The cycle gas is from the top of the device 51 through the fan 27 via a gas heater 28 and the lines 29 conveyed into the device 51. Shortly before entering the device 51 is through the line 30 a part of the circulating gas is branched off from the line 29 and via the cooler 31 into the discharge the screw 26 promoted. This arrangement is used to feed the fresh product coming from the screw 26 with the cooled gas into the device 51 and thereby avoid premature heating and softening of the fresh food. The fresh material that comes from the screw 26 into the device is caused by the high gas flow rate, which prevails in the cylindrical lower part of the device, very quickly in

conveyed the conical part of the device and immediately with that located in the device 51 Reaction well mixed. The arrangement prevents the fresh goods from sticking together prematurely.

The slide 23 and 24 make it possible to selectively fine-grain reaction material from the upper part of the device or coarse-grained material from the lower part of the cone or material from both parts of the device deduct.

Fig. 5 shows the structure of a two-stage fluidized bed device. On the device 41 is a tube cooler 32 is attached, which leads to the fluidized bed 33. The fresh goods come out of the lock 45 by the screw conveyor 46 into the first fluidized bed 33. Here it is at about 300 ° C with swirling Mixed reaction product. In the upper third of the part 33 opens the overflow pipe 34, through which the excess of the fluidized material, which is created by the supply of fresh material, down into the second ao Fluidized bed 43 of device 41 arrives. Here the reaction is carried out at around 400 ° C. Of the Excess fluidized material goes through the overflow (terephthalate) to be adhered to, as was stated in the exemplary embodiment of the known method the mixture ratio actually present in this embodiment is calculated, namely as follows:

Before the start of the experiment, this mixing ratio is 0 because there are only 30 kg of terephthalate in the reactor are present, and 0 kg of phthalate. At the end of the first minute there are 400: 60 = 6.67 kg of phthalate in the reactor before. But that is not yet the relationship that occurs in the steady state. This will rather, it is determined by the average life of the phthalate in the mixture. As far as it is For the purposes of the present invention is considered, experience has shown that this service life is at least 6 minutes, because the fresh food remains molten for at least 6 minutes, and that is the criterion that is important for the feasibility of the procedure.

After 6 minutes, there are also 6 · 6.7 = 40 kg of phthalate in addition to the 30 kg of terephthalate, which a mixing ratio of phthalate to terephthalate = 40: 30 = 1.33: 1 or a percentage of the eddy material from 40:70 = 57.1%

tube 35 via a screw conveyor 36 into the discharge lock 37, from which it corresponds periodically withdrawn as phthalate.

will. A partial flow of the circulating gas flows from part 33 of device 41 via fan 48 and the heater 44 through the line 49 to the grate 42.

Another partial flow of the cycle gas comes from the upper part of the fluidized bed 43 via the line 47 and merges with the gas flowing from the first fluidized bed 33 in front of the fan 48.

Via line 38, a further partial flow of the circulating gas is passed through a nozzle 39 into the riser pipe 40, which is arranged in the lower part of the fluidized bed, and through the cooler 32 into the upper fluidized bed 33 headed. Through the opening at the lower end of the riser pipe 40, part of the fluidized material is removed from the lower fluidized bed with promoted upwards to be used in fluidized bed 33 as a diluent for the fresh

good that comes out of the auger 46 to serve. The method of the present invention is as follows explained in more detail on the basis of the exemplary embodiments. Of these, Embodiment 1 relates to that

at the beginning mentioned known method, which is not 45 at the upper end with a gas outlet and a

for the continuous execution of the own feed for the vortex material was provided. Farther pressure and temperature measuring devices and an electric heater were installed.

The device was charged with preheated carbon dioxide and by means of electrical heating brought to the desired temperature. then

The experimental conditions were as follows:

Eddy material made of dipotassium

terephthalate and

Dipotassium phthalate approximately 50 to 70 grams per batch

Mixing ratio ... 5: 5 to 5: 1

Catalyst 2% cadmium oxide

Grain about 0.5 mm

Pressure 12 at

Carrier gas 2 to 3 m ³ CO ₂ / h

Temperature 410-415 ^C C

Time per batch 15 minutes

A cylindrical pressure vessel was used as the reaction device, at the lower end, as in fluidized bed devices usual, with a porous inflow base and a feed for the carrier gas,

net, and Examples 2 to 4 the process according to the invention.

example 1

From the exemplary embodiment of the description of the known method, the following technical ones were available Data available:

Original (terephthalate) 30 kg

Fresh food addition (phthalate) ... 400 kg / h

Grain size 0.5 to 3 mm

Catalyst 2% CdO

Carrier gas 2200 m ³ CO ₂ / h

Pressure 12 at

Temperature about 410 ° C

the prepared mixture was introduced via a pressure lock and exposed to the reaction conditions for 15 minutes.

The solids content of the starting materials was kept slightly lower than in the description of the known method, namely to 50% instead of 57.1. Nevertheless, the reaction product was completely together after just 15 minutes. baked and had to be knocked out of the device.

It was made in a laboratory scale, with strict adherence to these specifications worked on a scale of 1: 1000. It was a matter of course batch operation necessary.

Above all, about the mixing ratio of fresh goods (phthalate) to the fully reacted product

Example 2

In a further series of tests, the proportion of the solids content of the starting material was as much as possible the same conditions as in Example 1 gradually reduced from 50 to 16.7%. The results of the

10

Individual tests are listed under a to d in the next bed with a content of the solids content of the summarized in the table below. It can be seen that a fluidized bed of 30% achieved useful results that even without mechanical agitation of the vortex can be.

Fluidized bed experiments for the isomerization of dipotassium phthalate

Serial
No. protocol
No. pressure
at Tem
temperature
⁰ C Reak
tion time
Minutes carrier
gas
mVh Deployed
product
amount, g
Phthalate
+ Tere-
phthalate Mix
relationship
Dipotassium
terephthalate
to phthalate percent
salary
of the vortex
good
of phthalate Test results
and remarks 1
a
b
d 294
291
292
295
296 12th
12th
12th
12th
12th 415
410
412
412
410 15th
15th
15th
15th
15th 2.0
3.0
2.5
2.0
2.8 78
79
68
60
50 5: 5
5: 4
5: 3
5: 2
5: 1 50
44.4
37.5
28.57
16.6 Reaction product
completely baked,
must be knocked out
will
Reaction product
totally together
glued
Reaction product
baked
Reaction product
easily together
baked, grain structure
still recognizable
Product well done
responds, the grainy one
Condition of the material
remained completely intact

Example 3

10 kg of starting mixture, consisting of 9.5 kg of potassium phthalate and 0.5 kg of cadium carbonate, in one Grains from 0.1 to 0.5 mm are mixed with 90 kg of reaction product, which is essentially a mixture represents of potassium terephthalate and catalyst, through a lock in a known per se Introduced fluidized bed device, which is kept under a carbon dioxide pressure of 30 at and in which already contains 100 kg of hot reaction material. In the device, the mixture is 30 minutes whirled at 400 ° C. The carbon dioxide that is released at this temperature before entering the fluidized bed has been heated, flows through the fluidized bed at a rate of 8 cm / second. then 100 kg of the fluidized material are drawn off through a lock and cooled. Then 90 kg of the chilled goods mixed with fresh starting goods. The rest of 10 kg is discharged as production and worked up in a known manner.

Example 4

55

In a fluidized bed device in which there are 900 kg of hot reaction product and the under a carbon dioxide pressure of 30 atmospheres, 100 kg of potassium phthalate are introduced through a lock, which contains 5% cadmium carbonate. The flow velocity of the carbon dioxide is 11 cm / second. The batch is vortexed in the device for 30 minutes. Then 100 kg of reaction product withdrawn, cooled and from the cooled material by acidification according to known methods Obtained terephthalic acid. The yield of terephthalic acid is 56 kg, corresponding to 88% the theory.

After each withdrawal of the finished product in the specified amount, 100 kg of the starting mixture are added introduced into the device and processed the new batch in the manner described.

In all embodiments of the method, the material in the device retained a good granular quality Nature. The grain size increased noticeably during the treatment of the goods. Approach formation and incrustations in the apparatus did not occur in the apparatus during normal operation.

Claims (7)

Patent claims: 1. Process for producing terephthalic acid by heating the alkali salts of others Benzene carboxylic acids as terephthalic acid or mixtures thereof in admixture with alkali salts of terephthalic acid under normal or elevated pressure in the presence of carbon dioxide and / or inert gases in a fluidized bed, that of an alkali salt of terephthalic acid and rearrangement catalysts is formed, characterized in that the proportion of the starting materials in the fluidized bed, the may additionally contain a mechanical stirring device, sized at 5 to 30 percent by weight. 2. The method according to claim 1, characterized in that in batches or in continuous operation works. 3. Process according to claims 1 and 2, characterized in that the gas velocity in a fluidized bed at 30 at carbon dioxide pressure and a temperature of 380 to 440 ° C to 2 to 15 cm / second or at normal Pressure and a temperature of 380 to ■ ". ··" -> 409 587/499 loading 400 ° C at 10 to 50 cm / second, respectively
moved to the free cross-section, adjusts. 4. Process according to Claims 1 to 3, characterized in that mixtures a grain size of 0.1 to 0.5 mm is introduced into the fluidized bed. 5. Process according to claims 1 to 4, characterized in that before the respective Introducing a new batch of phthalate and catalyst the temperature in the fluidized bed below the melting temperature of the Phthalate lowers and upon completion of mixing with the contents of the reaction device brings back to reaction temperature. IO 6. Process according to claims 1 to 5, characterized in that during the Introducing the new batch into the fluidized bed, the gas velocity to about a third one-sixth, appropriately one-fifth, of their normal size. 7. The method according to claims 1 to 6, characterized in that the gas flow dimensioned larger on the walls of the reaction device than in the middle of the fluidized bed. Considered publications:
German patent specification No. 1028 577. For this purpose Ϊ sheet of drawings 409 587/499 4.64 © Bundesdruckerei Berlin