DE1112506B - Process for the production of potassium terephthalate by thermal rearrangement of the dipotassium salts of phthalic or isophthalic acid or their mixtures - Google Patents

Description

Terephthalic acid is a sought-after basic raw material for the production of valuable polyester fibers, which is why their production is constantly increasing. The terephthalic acid or its methyl ester can be different Because of what the oxidation of p-xylene in the liquid phase and S the isomerization of potassium phthalate can be carried out industrially. The isomerization of alkali salts aromatic o-dicarboxylic acids to the p-derivatives is already known. However, this method is for the production of terephthalic acid only for some time because of the considerable technical difficulties Time has been realized industrially.

The thermal rearrangement takes place at greater speed only above the melting point of potassium phthalate, resulting in solid potassium terephthalate, which has an unsatisfactory thermal conductivity has and so makes it difficult to heat the reaction mass quickly. If you work in a thicker shift, it is a longer one Heating time and a major drop in temperature in the reaction mixture for complete reaction of the starting materials necessary. However, this has a considerable thermal decomposition of the reaction mixture and result in a decrease in the yield of the end product. So you have to get the reaction in these cases perform under the pressure of carbon dioxide. Bake with this procedure In addition, the substances are usually firmly together, so that their removal from the reaction vessel is difficult prepares.

Attempts have been made to overcome this difficulty by keeping dipotassium phthalate inside a pressure vessel is heated in a fluidized bed, which is a considerable part of the filling the container Dipotassium terephthalate is formed by streams of preheated material introduced tangentially into the filling Carbon dioxide is kept in vortex motion. In this fluidized bed is made by means of a screw Slowly add the well-predried dipotassium phthalate to a storage container, which in small amounts Catalyst is admixed, introduced. The dipotassium terephthalate used to form the fluidized bed is present in a much larger amount than the introduced one throughout the process Dipotassium phthalate. For this reason, the pressure vessel must be relatively large in size own. In addition, considerable forces are required to move the dipotassium terephthalate through the carbon dioxide streams get in vortex motion. That in the filling of the pressure vessel with dipotassium terephthalate Introduced carbon dioxide escapes from manufacturing processes

of potassium terephthalate by thermal

Rearrangement of the dipotassium salts of the phthal

or isophthalic acid or mixtures thereof

Applicant:

Jaroslav Beranek,

Drahomir Sokol, Pardubice,

Dr.-Ing. Josef Ratusky and Frantisek Sorm,

Prague (Czechoslovakia)

Representative: Dipl.-Ing. A. Spreer, patent attorney,
Göttingen, Groner Str. 37

Jaroslav Beranek, Drahomir Sokol, Pardubice,
Dr.-Ing. Josef Ratusky and Frantisek Sorm,

Prague (Czechoslovakia),
have been named as inventors

the filling upwards and is returned to the filling after it has been heated again, it moves So they are constantly in a cycle.

It has now been found that, while avoiding the disadvantages described, dipotassium terephthalate in significantly improved space-time yield is obtained if the powdered potassium salts of the phthal or isophthalic acid or mixtures thereof with the aid of a carbon dioxide stream that has a temperature has below the melting point of the potassium phthalate, through tangential feed lines in a cyclone Introduced formed reaction vessel, in the simultaneously heated to 500 to 800 ° C carbon dioxide flows in through other tangential feed lines. This completes the isomerization, before the particles come into contact with the walls of the reaction vessel.

You can adjust the temperature by changing the rate of supply of carbon dioxide in the first and control the second feed system in order to achieve a temperature of 400 to 600 ° C in the reaction space. The shape of the reaction vessel has been chosen so that the potassium phthalate particles in the React gas flow completely before it goes to the walls

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come from the reaction vessel. In this case the residence time of the particles is less than 5 seconds. It has been proven experimentally that the reaction time mentioned allows for quantitative reaction the starting materials is completely sufficient, due to the high reaction temperature and the small dimension of the particles. That is why it is possible even under normal pressure of carbon dioxide to work, d. that is, the device is relatively simple. One can use the powdery reaction product from the reaction vessel through a special tangential discharge into a storage vessel for potassium terephthalate lead, the carbon dioxide through another tangential line to the pump and to is passed on to a heat exchanger. It is also possible to separate the potassium terephthalate particles of the carbon dioxide stream only in one or more downstream of the reaction vessel Perform separation cyclones.

When potassium phthalate particles of various sizes are used, the particles move in the direction towards the walls at different velocities, with the largest particles at be driven fastest.

It can therefore also happen that the largest particles in the gas flow do not react completely can. If the number of such particles were considerable, they might stick to the Walls of the reaction vessel come. This disadvantage can be eliminated by removing the particles either on a movable layer of potassium terephthalate particles or the catalyst or of one Mixture of the two, which circulate on the walls of the reaction vessel, can impinge.

If you choose the shape of the reaction vessel accordingly, it is possible to form a to force such a layer from the particles of the reaction product and the catalyst present. The same result can be achieved by using either potassium terephthalate or from the catalyst used introduces particles or a mixture of both into the reaction space, see above that they reach the walls earlier than the potassium phthalate particles.

The advantage of the method according to the invention for the production of potassium terephthalate is in particular in that the residence time of all particles in the reaction zone with a homogeneous temperature distribution is the same and very short. Therefore you can use higher reaction temperatures, whereby the process of implementation is accelerated. Because very considerable throughput speeds are possible the performance of the device is substantial and the manufacture of the potassium terephthalate in continuous way possible.

example 1

A mixture of 750 m ^s / hour of carbon dioxide, which has been preheated to a temperature of 450 ° C., and 1250 kg / hour of pulverized potassium phthalate with a particle size less than, is fed into a ^{0.5 m 3} reaction vessel designed as a cyclone 1 mm and 37.5 kg of catalyst, so that the incoming reaction mixture has a temperature below the melting point of the potassium phthalate. ^{4000 m 3} / hour of carbon dioxide at 700 ° C flow in through other tangential feed lines.

The resulting potassium terephthalate is separated in separating cyclones, while the carbon dioxide is returned to the reaction chamber with a pump via a heat exchanger. Man receives in this way 1230 kg 88% potassium terephthalate per hour, which is then in a known Way can be worked up to terephthalic acid.

Example 2

The rearrangement of the potassium phthalate is carried out in a similar manner and in the same proportions carried out as in Example 1, with the only difference that the reaction vessel designed as a cyclone for the immediate separation of the potassium terephthalate is set up by carbon dioxide in the reaction chamber. This gives you 1190 kg of 90% more Potassium terephthalate per hour.

Example 3

The rearrangement is carried out in the same way as in Examples 1 and 2, only one uses Potassium isophthalate instead of potassium phthalate. In this case, 1220 kg or 1180 kg are obtained 88% potassium terephthalate per hour, depending on whether you are working according to Example 1 or Example 2.

Example 4

The reaction is carried out in the same way as in the previous examples, only goes one of a mixture of potassium phthalate, potassium isophthalate and potassium terephthalate in proportion 20:60:20 off. In this case you get ever Hour 1190 kg 86% potassium terephthalate.

Example 5

The rearrangement of potassium phthalate is carried out under the same conditions as in Example 1, only one passes through the second system of tangential feed lines at the same time as the stream of carbon dioxide 2600 kg / hour of powdered potassium terephthalate together with 100 kg / hour of catalyst a. The potassium terephthalate is separated from the carbon dioxide stream directly in the reaction space. Man in this case, 1190 kg of 89% potassium terephthalate are obtained per hour, calculated on the converted dipotassium phthalate.

The above-mentioned 2600 kg / hour of powdered potassium terephthalate are always in the Cycle.

Claims (3)

PATENT CLAIMS: 1. A process for the production of potassium terephthalate by thermal rearrangement of the dipotassium salts of phthalic or isophthalic acid or mixtures thereof, characterized in that the powdered salts are introduced with the aid of a carbon dioxide stream through tangential feed lines into a reaction vessel designed as a cyclone, in which at the same time to 500 Carbon dioxide heated to 800 ^° C. flows in through other tangential feed lines, discharges the powdery reaction product with the carbon dioxide stream from the reaction device and separates it either partially within the device or in a downstream device. 2. The method according to claim 1, characterized in that one with the aid of the carbon dioxide stream powder into the reaction vessel 5 6 Total potassium terephthalate or catalyst particles formed reaction vessel directly from the or brings in a mixture of the two. Carbon dioxide stream separates. 3. The method according to claim 1, characterized indicates that 85 to 95% of the powder is used. Fönnigen reaction product in the as Zyklon 5 German Patent No. 1028 577. © 109 677/220 8.61