BE724040A - - Google Patents

Description

  

   <Desc / Clms Page number 1>
 



  "METHOD AND APPARATUS FOR THE PREPARATION OF ACID
TEREPHTHALIC "
The present invention relates to an apparatus and process for the preparation of terephthalic acid from a p-dialkyl-benzene or an intermediate oxidation product thereof. More particularly, the invention relates to an apparatus in which p-dialkyl-benzene or its intermediate oxidation product, as a raw material, is oxidized with molecular oxygen in a liquid reaction medium and in the presence of a. heavy metal oxidation catalyst, to form terephthalic acid and the invention also relates to an industrial process for the preparation of high purity terephthalic acid using this apparatus in high yields and stable operation.

 <Desc / Clms Page number 2>

 



   Previously, the preparation of terephthalic acid by oxidation of a p-dialkoylbenzene or its intermediate oxidation product (the latter will hereinafter be referred to collectively as "p-dialkoylbenzene") with molecular oxygen. in a liquid reaction medium and in the presence of a heavy metal oxidation catalyst has been the subject of great industrial concern and a large number of modifications have been proposed in this regard.

   Among the examples of the prior art are: (1) the process in which the oxidation is carried out in the presence of an organic acid salt of a heavy metal such as cobalt or manganese acetate , as well as a bromine compound such as ammonium bromide, as described in U.S. Patent No. 2,833,816; (2) the process in which the reaction is carried out in the presence of an organic acid salt of cobalt and a methylenic ketone such as methyl ethyl ketone, as disclosed in U.S. Patent No. 2,853,514 ;

   (3) the process in which the reaction is carried out in the presence of an organic acid salt of cobalt and an aliphatic aldehyde such as acetaldehyde, as described in US Pat. No. 2,673,217; (4) the process in which the oxidation is carried out in the presence of a compound of cobalt and paraldehyde, as described in UK Patent No. 1,043,426 (5) the process in which an organic acid salt of cobalt as a catalyst, a process in which ozone (03) is additionally employed as a reaction initiator, as described in US Pat. No. 2,992,271;

   (6) the process in which the oxidation is carried out in the presence of cobalt acetate and hydrobromic acid, as described in US Pat. No. 3,139,452 i (7) the process in which. The oxidation is carried out in the presence of a large amount of a cobalt compound, as described in U.S. Patent No. 3,334,145

 <Desc / Clms Page number 3>

 (8) the process in which the oxidation is carried out in the presence of a compound of cobalt and of compounds such as scandium, yttrium, lanthanum, neodymium, gadolinium, thorium, zirconium, .hafnium, etc., as described in US Pat. No. 3,299,125 and (9) a process for oxidizing a mixture of p-xylene and p-toluic acid in the presence, for example, of acetate manganese,

   as described in French patent No. 1,262,259.



   In all of the above processes (1) to (9), as liquid reaction media, lower aliphatic monocarboxylic acids are employed, especially those of 2-4 carbon atoms, for example acetic acid. Among the other processes in which different compounds are used as liquid reaction media, there is (10) the process in which gamma-butyrolactono is used, as described in German Patent No. 1,100,015 (11) the process wherein organic nitriles such as benzonitrile are used, as described in German Patent No. 1,117,099;

     (12) the process in which cyclic carbonate such as ethylene carbonate, propylene carbonate, etc. is used, as described in German Patent No. 1,132,115 and (13) the process in which is used benzoates such as methyl benzoate, as described in German Patent No. 1,144,708,., The various procedures listed above have a common characteristic in that terephthalic acid is prepared by oxidation of p-dialkylbenzene with molecular oxygen in a liquid reaction medium and in the presence of a heavy metal oxidation catalyst.



   The object of the present invention is to provide an apparatus and method useful for the preparation of terephthalic acid from a p-dialkoyl-benzene, just as

 <Desc / Clms Page number 4>

 in the above processes, this apparatus and process enables stable and continuous operation, high molecular oxygen utilization ratio, as well as the preparation of high purity terephthalic acid in high yields. ,
Other objects and advantages of the invention will emerge from the following description.
According to the invention, the above objects and advantages are essentially achieved by an apparatus for preparing terephthalic acid from p-dialkoylbenzene or an intermediate oxidation product of the latter,

   this apparatus comprising a reactor the bottom of which tapers downwards, this reactor being provided with a gas discharge pipe at its upper part, with an outlet for the reaction product at its lower part and with a feed line for raw material at a suitable intermediate point, a gas injector supplying molecular oxygen or a gas containing molecular oxygen and opening into the lower part of the reactor, a draft tube with an open top and bottom, placed above the gas injector, as well as a gas distributor intended to disperse molecular oxygen or a gas containing molecular oxygen inside the reactor, this distributor being placed above and at a suitable distance from the draw tube,

   the reactor being further equipped with a heating and / or cooling element to maintain the reaction materials being reacted at the predetermined reaction temperature,
 EMI4.1
 p-dialkoylbanWno or its intermodial oxidation product, the liquid reaction medium and the catalyst being thus supplied through the material feed line, while at least part of the molecular oxygen or gas containing molecular oxygen is supplied by

 <Desc / Clms Page number 5>

   'gas injector,, The invention will be described below in more detail with reference to the accompanying drawings which facilitate understanding.



   In the accompanying drawings, figure 1 is a vertical section showing the basic structure of the apparatus which is the object of the invention; figures 2a, 2b, 3a, 3b and 4a, 4b illustrate some examples of the dispenser to be attached to the interior of the apparatus according to the invention, the flowers bearing the suffix a being plan views taken in the direction of line 1-1 of FIG. 1, while the figures bear- both the suffix b are cross sections taken each along the line indicated in the corresponding figure bearing the suffix a;

   Figures 5, 6 and 7 show other embodiments of dispensers of a different type from those shown in Figures 2a, b - 4a, b, the relationship of Figures "a" and "b" being the same as that shown above, except for Figure 5c which shows a somewhat modified structure of the embodiment shown in Figure 5b;

   Figures 8 and 9 each show a further embodiment of the apparatus according to the invention and Figure 10 is a diagram showing the general sequence of steps of a whole operating system for the preparation of terephthalic acid using the same. apparatus according to the invention, as well as for recovering the desired product from the reaction liquid, the volatile reaction material and the reaction medium being recovered from the exhaust gas,
In the accompanying drawings, the same parts are

 <Desc / Clms Page number 6>

 designated by the same reference numbers,
Figure 1 is a vertical section showing the basic structure of the apparatus according to the invention in this figure, the numeral 1 denotes a closed type reactor with a conical bottom 2.

   At the top of the reactor 1, a gas evacuation pipe 3 is provided and, at an optional location on the conical bottom 2, an outlet for the reactive product is provided. Similarly, the first gas injector 6 is provided. attached to the lower end (or near it) of the conical bottom 2. On the side of the reactor 1, a material feed line 5 is attached, through which the reaction material, o est-à- ie a mixture of a p-dial-coylbenzene 'of a catalyst and of a liquid reaction medium, is fed into the reactor 1.

   The reference number 11 indicates the level of the reaction liquid in the reactor,
Molecular oxygen or the gas containing molecular oxygen (the latter will be referred to collectively hereinafter as "gas containing molecular oxygen") to be brought into contact with the material. reaction above to oxidize the p-dialkylbenzene therein, is blown directly into the reaction liquid from the bottom of the reactor 1, through the first gas injector 6.

   The gas passes through the open-top and bottom-open draft tube 7, this tube being provided above the open end of the first gas injector 6, then the gas rises in countercurrent and in contact with the reaction liquid. , while it is uniformly dispersed in the reactor 1 by a distributor 8 comprising several passages 9 for the gas containing molecular oxygen, as well as for the reaction liquid. Finally, the gas reaches the gas phase 12 at the top of the reactor 1 and is discharged through the gas discharge line-%

 <Desc / Clms Page number 7>

 while the gas phase 12 is maintained at the predetermined pressure level at the hub of a pressure sensing element 13.

   Reference numerals J ', 4', 5 'and 6' each indicate a valve which may be of the ordinary type or a regulating valve which can operate continuously.



   In order to maintain the reaction liquid in the reactor at a predetermined temperature, heating and / or cooling devices 10a and 10b are provided respectively inside and outside the reactor 1. These heating and / or cooling devices are provided. The coolers can be designed as one communicating system or as two different systems. However, normally, for ease of operation, it is desirable to connect them.



   Likewise, a temperature detector 14 is provided in the reactor 1 so that the reaction liquid contained in the reactor remains at constant temperature. The location of the temperature sensor 14 is not critical, as long as it is located higher than the distributor of the reactor 1. However, it is normally desirable to provide this sensor more or less in the central part. of reactor 1.



   The mine carried out by the process of the invention will be described below in more detail using the apparatus illustrated in FIG. 1.



   When carrying out the process of the invention using the apparatus of FIG. 1, the following raw materials are first charged to the reactor through the material feed line 5:
 EMI7.1
 (a) p-dialkoyibenzene, (b) aliphatic monocarboxylic acid of 2 - 4 carbon atoms (liquid reaction medium) and (c) a heavy metal oxidation catalyst,

 <Desc / Clms Page number 8>

 then the valve 6 'of the first gas injector 6 at the bottom of the reactor 1 is opened to charge the gas containing molecular oxygen at an appropriate pressure. At the start of the reaction, the heat of reaction is rapidly formed.

   Therefore, it is desirable to initially charge, into the reactor, a liquid mixture of the above liquid reaction medium and the catalyst only or a reaction liquid with a low concentration of coylbenzene pdial, then to charge the gas containing l. molecular oxygen by the first gas injector 6 'after which the system is heated by means of the heating and / or cooling devices 10a and 10b. When the temperature reaches the predetermined reaction temperature between 80 and 150 ° C, the reaction material containing p-dialkoylbenzene at the predetermined concentration is charged through line 5 to continue the reaction.



   The normally preferred composition for the raw material is as follows (a) per 1 part by weight of p-dialkoylbenzene, (b) 0.5-20, in particular 1-10 parts by weight of the aliphatic monocarboxylic acid and (c) per gram molecule of p-dialkylbenzene, a heavy metal catalyst in an amount corresponding to 1 x 10-5 to 2.0, preferably 1 x 10-3 to 1.0 gram atom of the metal heavy.



   Therefore, the gas containing molecular oxygen, charged by the first gas injector 6, passes through the draw tube 7 and there creates an upward effect of air establishing a current of circulation of the liquid concomitantly. holding the reaction product in the lower part 2 of the reactor 1, inside and outside the draft tube 7. The gas containing molecular oxygen passes through the passages 9 in the distributor 8 for ascend

 <Desc / Clms Page number 9>

 through the main reaction zone 1a formed above the distributor 8 in the reactor 1, while it is uniformly dispersed.

   In the main reaction zone 1a, the gas comes into intimate contact and countercurrent with 1a. liquid reaction material continuously charged through the material feed line 5 and oxidizes the p-dialkylbenzene. Likewise, the exhaust gas is discharged through line 3 at a rate controlled so as to also regulate the pressure in the gas phase portion 12 to a predetermined level.

   On the other hand, the solid terephthalic acid formed in the reaction zone descends it with the descending current of the reaction liquid through the passages 9 of the distributor 8, as well as with the intermediate oxidation products such as, for example, p-toluic acid (APT), 4-carboxybenzaldehyde (4-CBA), etc., to arrive in the lower part 2 of the reactor 1 where the products enter the aforementioned circulating stream. As a result, the intermediate oxidation products are further oxidized with the gas containing molecular oxygen and are converted to terephthalic acid, while the solid terephthalic acid is sufficiently suspended in the reaction medium. nel liquid Bous the action of the circulating current.

   Therefore, the terephthalic acid can be withdrawn outside the reaction system through the outlet 4 without forming deposits and scales on the walls of the lower part 2.



  Terephthalic acid can be withdrawn continuously or intermittently,
In addition, using the apparatus of the invention as described above, the molecular oxygen-containing gas charged from below is uniformly dispersed throughout the main reaction zone below. action of distributor 8, so that it does not form

 <Desc / Clms Page number 10>

 no dead space in the main reaction zone 1a.



  Likewise, in the lower part 2 of the reactor 1: the reaction liquid and the product form a good circulation current as a result of the air rising effect of the gas containing molecular oxygen charged by the first injector of gas 6 in the draw tube 7. This circulating current, as well as the conical structure of the lower part 2 contribute to eliminating the dead spaces in this zone.



   Consequently, during the implementation of the process according to the invention with an apparatus of this type, the gas containing molecular oxygen, charged by the first gas injector 6, is used very efficiently in the entire zone of the reactor. 1 and it is brought into intimate contact with the reaction liquid. Therefore, according to the invention, terephthalic acid of high purity and in high yields can be obtained.

   In addition, as a result of the dispersing and stirring effect of the molecular oxygen-containing gas throughout the reactor zone 1, the reaction product is prevented from depositing on the interior walls of the reactor in the main reaction zone. - blade the or on the surface of the heating and / or cooling devices 10a and 10b, Likewise, in the lower part 2 of the reactor 1, the regularly circulating current effectively prevents the deposition of the liquid reaction product and the formation scales of the latter on the walls of the reactor.



   In addition, it has been found that, in carrying out the process of the invention, the losses of unreacted p-dialkylbenzene which is discharged outside the reaction system can be reduced. with the exhaust gas, while a brief passage of the p-dialkoylbenzene and the intermediate oxidation products can be prevented.

 <Desc / Clms Page number 11>

 diaries above, so as to maintain their residence time at a predetermined value, when @ / L is 1 / 4-1 / 3, L being the distance between the inlet of the first gas injector 6a for the supply gas containing molecular oxygen in the reaction liquid and the level of reaction liquid 11 in reactor 1,,

  sucking the distance enter the inlet of the material feed line 5 to charge the starting mixture, consisting of p-dialkylbenzene, aliphatic monocarboxylic acid of 2 - 4 carbon atoms and catalyst d heavy metal oxidation in the reactor and reaction liquid level 11.



   When the gas containing molecular oxygen passes through the reactor 1, the volatile component of the reaction liquid evaporates into the gas and an equilibrium of the volatile component is established between the gas phase and the liquid phase. Hence, part of the p-dialkylbenzene is entrained by the gas containing molecular oxygen and it is discharged from the reaction system. This is why the higher the concentration of p-dialkoylbenzene in the reaction liquid, the greater the quantity of p-dialkoylbenzene entrained by the gas containing molecular oxygen, i.e. the quantity of p-dialkoylbenzene. to be used effectively in the reaction, is reduced.

   Similarly when the feed inlet of the starting mixture is so close to the outlet of the reaction product, there is more frequently a short passage of the p-dialkoylbenzene and its intermediate oxidation products, so well. that unreacted material or intermediate oxidation products remain as residues.

   Therefore, the conversion into terephthalic acid, based on the p-dialkylbenzene feed, becomes disadvantageously low. On the other hand, the above drawbacks can be eliminated by

 <Desc / Clms Page number 12>

 charging the starting reaction liquid at a rate at which the # / L ratio is 1 / 4-1.3, as shown above, and the oxidation reaction of p-dialkoylbenzene can be better completed,
In addition, when practicing the invention, it is preferable to control the total amount of molecular oxygen or molecular oxygen-containing gas to be charged to the reactor so that its surface mass velocity at through the reaction liquid, in the main reaction zone of reactor 1 (without creating paths)

   or 0.8-20 cm3 / cm2.sec., preferably 0.9-10 cm3 / cm2.sec.



   In the following description, the speed or flow rate specified above for the gas containing molecular oxygen will be referred to simply as "surface gas velocity". According to the present invention, the rate of scale growth of the reaction product is effectively reduced on the walls of the reactor 1 in the main reaction zone 1a, as well as on the tubular walls of the heating and / or cooling devices 10a and 10b and high purity terephthalic acid can be obtained with better yield by adjusting the gas superficial velocity as above, When the gas superficial velocity is less than the lower limit of the range specified above ,

   the rate of scale growth increases rapidly and the resistance to heat transfer increases, making it difficult to control the temperature. Likewise, if the surface velocity of the gas increases excessively, as a rule, the retention of the reaction liquid in the reactor 1 decreases, which denies zero. This is desirable, since this reduces the effective usable capacity of the reactor. Therefore, the upper limit

 <Desc / Clms Page number 13>

 The higher gas surface velocity is preferably 20 cm3 / cm2.sec, especially 10 cm3 / cm2.sec, from the point of view of ease of actual operation and also from the point of view of economy.



   . Various embodiments of dispensers useful for practicing the invention will be described below.



   As shown in Figures 2a and 2b, the distributor may consist of a plate 8 with a diameter equal to the internal diameter of the reactor 1 and comprising a large number of basages9 in the form of holes made right through,
Likewise, as shown in Figures 3a and 3b, parts other than the passages of the perforated plate 8 (shown in Figures 2a and 2b) may protrude upward.

   In this embodiment, the solid reaction product accumulating on the perforated plate 8 easily slides along the inclined planes of the projections and passes through the passages 9 into the lower part 2 of the reactor 1,
Likewise, the distributor 8 may consist of a conical plate 41 and numerous inclined plates 42 concentrically surrounding the plate 41, as shown in Figures 4a and 4b,
Therefore, the shape and structure of the distributor are not critical, as long as they allow the passage and the upward dispersion of the gas containing molecular oxygen and furthermore, they allow the passage of the reaction liquid. containing the solid reaction product, 'Therefore, in the dispensers illustrated in the drawings,

   the cross section of the passage is not limited to a circle, but it can be a triangle, ellipse, rectangle, etc. Likewise, in order to improve

 <Desc / Clms Page number 14>

 dispersion of the gas containing molecular oxygen in the main reaction zone 1a, the cross sections of the passages 9 can be varied;

   for example, as regards the plate 8 of figures 2a and 2b, the areas can be reduced in the central part and widened as one approaches the circumference,
Likewise, the diatributor useful for the invention may be of the type illustrated in FIGS. 5a, b - 7a, b, these distributors being able not only to pass and disperse the gas containing molecular oxygen upwards, while making also pass the reaction liquid containing the solid reaction product, but they themselves can also feed the gas containing molecular oxygen into the reactor.



   For example, in the embodiments illustrated in Figures 5a, b - 7a, b, the distributor 8 is intended to supply the predetermined amount of the gas containing molecular oxygen into the reaction zone - the main one with the first gas injector 6 provided at the base of the reactor 1. Obviously, it is preferable to control the total amount of the gas supply to the main reaction zone 1a from the distributor and the gas injector, in order to obtain the gas surface velocity specified above.



   In the distributor illustrated in Figures 5a and 5b, the gas containing molecular oxygen is supplied to the chamber 52 constituting the main body of the distributor 8, from the second gas injector 51, and then it is blown downwards. through the numerous perforations 53 in the reaction liquid contained in reactor 1, the gas combines with the gas containing molecular oxygen supplied from the bottom of reactor 1 and it

 <Desc / Clms Page number 15>

 is dispersed in the main reaction zone 1a through the passages 9. Likewise, the reaction liquid containing the solid reaction product in the main reaction zone descends it to the bottom 2 of the reactor 1 through the passages 9.



   The dispenser 8 may have the structure shown in Figure 5c, in which the lower surface of the chamber 52 forms numerous downward protrusions 54, the inclined sides of these protrusions having a large number of perforations 53 to ensure the path of the gas containing molecular oxygen through the reaction liquid. In this case, preferably, the perforations are made on the inclined planes of the projections 54, so that their directions are at least inclined downwards with respect to the horizontal plane. In this way, the obstruction of the perforations 53 by the scales of the solid reaction product can be prevented.



   In the distributor illustrated in Figures 6a and 6b, two concentric cylindrical pipes 61 and 62 are connected by two second gas injectors 51 and 51 ', the gas containing molecular oxygen is supplied by the second gas injectors 51 and 51 ', it passes through the hollow connecting conduits 63 to arrive in the conduits 61 and 62, then it travels downwards through the numerous perforations 53 made on the lower surfaces of the conduits 61 and 62, Likewise, the spaces surrounded by the four connecting pipes 63 and the two concentric pipes 61 and 62, as well as the interior space of the pipe 62, form the passages 9 playing the same role as the passages 9 of the embodiment of FIGS. 5a and 5b.



   Figures 7a and 7b show yet another embodiment of the dispenser capable of providing it.

 <Desc / Clms Page number 16>

 even the supply of gas containing molecular oxygen; in these figures, the reference numeral 1 'designates the side wall of the reactor 1. The distributor is made up of several hollow pipes 7a, 7b, 7c and 7d which are introduced horizontally from the side to the interior. laughter of the reactor 1, each of the conduits having numerous perforations 53 on its lower surface.

   The molecular oxygen-containing gas is fed from the second gas injector 51 into the hollow lines 7a, 7b, 7c and 7d, it travels down into the reaction liquid through the perforations 53 and it is dispersed for s 'rise in the main reaction zone 1a via the passages 9 made between the hollow pipes 7a, 7b, 7c and 7d, as well as between these pipes and the side wall 1' of the reactor 1, The role of the passages 9 is the same as that of the equivalent passages of the embodiments of Figures 5a, b and 6a, b.



   The mode of supplying the gas to the reactor 1, when the distributor is of the type comprising one or more., Sieurs seconda gas injectors and being able to ensure itself the supply of gas containing molecular oxygen. as shown in figures 5a, b to 7a, b, is not critical, provided that the total quantity of gas charged from the first gas injector 6 to the bottom 2 of the reactor 1 and that supplied by the second gas injector gas 51 through distributor 8 in reactor 1 ensure the aforementioned superficial gas velocity and that the gas containing molecular oxygen, supplied by the first gas injector,

   can form a smoothly circulating stream of the reaction liquid containing the reaction product in the lower part 2 of the reactor 3. In other words, the quantitative ratio of the gas supplied by the gas injectors 6 and 51 is not critical. , provided that the

 <Desc / Clms Page number 17>

 above are met. However, it is preferred that the supply of gas from the first gas injector be effected at a rate at which the surface velocity of the gas in the main reaction zone 1a is 0.015 - 20. , 0 cm3 / cm2.sec .. for the reasons given above.

   In addition, it is obviously recommendable that the gas containing molecular oxygen, supplied by the second gas injector through the distributor 8 and combined with the gas coming from the first gas injector, is dispersed in the zone. main reaction as uniformly as possible.



   The shape and dimensions of the draw tube 7 provided above the inlet 6a of the first gas injector 6 at the bottom 2 of the reactor 1 are not critical, provided that this tube is hollow, its top and its bottom are open and its inside diameter and height are sufficient to form a smoothly flowing stream of reaction liquid and reaction product through the tube in the lower part 2 of the reactor Normally, the inside diameter will not exceed one third of that of reactor 1, but it will also not be less than 1 cm, and preferably the height is 1-20 times the inner diameter.



   Likewise, the locations of the draw tube 7 and of the first gas injector 6 are not critical, as long as they are located near the lower end of the lower part 2 of the reactor 1, however, in order to to improve the circulation of the reaction liquid, they will be located as close as possible to the lower end, at least as far as the mechanical design allows,
As indicated above, the shape of the draft tube 7 is not critical, as long as it allows

 <Desc / Clms Page number 18>

 the passage of gas containing molecular oxygen, to play the role described above.

   For example, one can use perpendicular pipes not bent in the axial direction and having triangular, square or circular cross sections, cylindrical tubes being however most often used, because they can be obtained more easily,
Likewise, the lower part 2 of the reactor 1, on which the draft tube 7 is provided, can be a horizontal flat surface, a conical surface, a conical surface consisting of a spherical plane, etc., or it can also be consisting of several of these planes or of a pyramidal face partially substituted by a curved or horizontal plane.



   However, in order to prevent the deposition and braking of the solid particles on the plane, it is preferable to adopt the structure not causing any inclination of the circulating stream of the reaction liquid.



     Therefore, when using a tapered face, the vertical angle extending upward at the bottom of the reactor should normally not exceed 120, preferably 90. The lower limit of the vertical angle is is not critical, but it is however restricted by the technical design factor, so normally this angle is at least 15, preferably 30, especially 45.



   Figures 8 and 9 show still other embodiments for the implementation of the present invention. '
In FIG. 8, a branch 81, the upper end of which opens into the bottom 2 of the reactor 1 and the lower end of which is closed, is fixed to the extreme lower end of the bottom 2. The solid reaction product

 <Desc / Clms Page number 19>

 collected at the bottom 2 of reactor 1 descends into branch 81 to be withdrawn from the outlet for the reaction product provided in, the lower part of branch 81 with the reaction liquid, in the form of a slurry having an even higher solids content .



   In addition, when an inlet pipe 82 is attached at a suitable location around the lower end of the branch 81 and, through this pipe, a liquid reaction medium or an aqueous solution thereof is supplied to the latter. branch 81, the solid reaction product is again washed and rinsed in branch 81, since both the reaction liquid descending therein with the solid reaction product is replaced by the new reaction medium loaded by the feed line 82. Therefore, the impurity content of the terephthalic acid to be removed from the reactor can be reduced, and the purity of this terephthalic acid can be significantly improved.

   the above device is useful for reducing losses of valuable materials such as catalyst and intermediate reaction products. A still further advantage is that the conversion to terephthalic acid can be significantly improved, since the intermediate reaction products return to reactor 1 after the further washing, to be further oxidized there.



   Furthermore, the mounting position of the branch 81 is not necessarily the extreme lower end of the bottom 2 of the reactor 1, but it can be located at any place in the vicinity of this same end Do, the branch can be directed perpendicular or somewhat inclined.



   The preferred capacity of this branch is corner is between 1 / 100- 1/10 of that of reactor 1, its diameter

 <Desc / Clms Page number 20>

 interior not exceeding half that of the reactor and it is, at least, 5 cm, while the length is equal, at least, to two times the internal diameter of this branch, without exceeding half of the depth of the liquid reaction (L) in reactor 1.



   The amount of rinsing liquid to be charged into branch 81 from inlet pipe 82, which can be mounted anywhere on this branch, but below half of its height , is determined in consideration of the impurity content of the terephthalic acid to be removed, the economics of the apparatus and process, and other technical considerations.

   The impurity content of terephthalic acid is in turn determined by such factors as the amount of solids coming from the inlet line 82. Therefore, the impurity content of the terephthalic acid can be reduced before can be removed from the reactor and the purity of terephthalic acid can be substantially improved. Moreover, the above device is useful for reducing losses of valuable materials such as catalyst and intermediate reaction products, Do more , yet another advantage lies in the fact that the transformation into terephthalic acid can be markedly improved, given that the intermediate reaction products return to reactor 1 following the new washing to be further oxidized therein,
Otherwise,

   the mounting position of the bran., che 81 is not necessarily the extreme lower end of the bottom 2 of the reactor 1, but it can be located at any location close to the end. Likewise, this branch can be directed perpendicularly or somewhat inclined.



   The preferred capacity of this branch is com-

 <Desc / Clms Page number 21>

 taken between 1/100 - 1/10 of that of reactor 1, its internal diameter not exceeding: more than half that of said reactor and it is, at least, 5 cm, while the length is'. equal, at least, to twice the internal diameter of the branch, without exceeding half of the depth of the reaction liquid (L) in reactor 1
The amount of rinsing liquid to be charged into branch 81 from supply line 82, which can be mounted anywhere on this branch, but below half its height , is determined in consideration of the impurity content of the terephthalic acid to be removed,

   economics of the apparatus and process and other technical considerations. The impurity content of terephthalic acid is in turn determined by factors such as the amount of solid reaction product to be treated, the operating system (e.g. continuous or intermittent system), the capacity of reactor 1, the the concentration of terephthalic acid in the slurry to be removed, the liquid substitution efficiency in branch 81 and the particle size of the terephthalic acid therein. Normally, the appropriate amount of rinse aid is 5 times that of the mother liquor of the slurry to be removed.



   The vertical level order of the outlet 4 for the reaction product and the inlet line 82 in the lower half of the branch 81 is not critical.



   Likewise, the liquid reaction medium provided for the rinsing and to be supplied into branch 81 from the inlet pipe 82 is preferably of an identical type to that supplied into the reactor 1 via the supply pipe. of material 5 or it can

 <Desc / Clms Page number 22>

 be an aqueous solution. In the latter case, the suitable water content is 50% or less, preferably 20%, especially 10% or less.



   Likewise, as the liquid reaction medium or as an aqueous solution thereof, to be supplied from the supply line 82 to the branch 81, some or all of the condensing liquid obtained by condensing the condensable component can be employed. with the exhaust gas discharged through the exhaust pipe 3 attached to the upper part of the reactor 1.



   Consequently, very favorable results are obtained by providing the branch 81 at the lower part of the bottom 2 of the reactor 1 and by providing an inlet pipe 82 to bring the rinsing liquid reaction medium into the branch 81.



   The temperature prevailing inside branch 81 during the rinsing operation is not critical. However, with a certain speed of withdrawal of the slurry mixture out of the branch 81 and with a later speed of supplying the rinsing liquid to this branch, a large temperature distribution interval is established in this branch 81, this being the case. which can cause scales to adhere to the inner walls of this branch or to the adjacent walls of the discharge valve and the inlet pipe 82. Accordingly, it is desirable to pre-adjust the temperature of the pipe. rinsing liquid to be brought through line 82 to approximately the same level as that of the reaction liquid, for example 80-150 C, by means of a preheater, etc.



   In the embodiment shown in Figure 9, on an apparatus substantially identical to that illustrated in Figure 1, there is provided a temperature control system for maintaining the reaction liquid

 <Desc / Clms Page number 23>

 in the reactor at the predetermined reaction temperature.



   The construction and mode of operation of the temperature control system are as follows:
Referring to Figure 9, water is introduced into the heating and cooling jacket 10b mounted outside the reactor 1, as well as into the heat transfer tubes 10a, through line 94, to at the predetermined water level in the main upper manifold 92 serving to separate vapor from liquid and also to maintain a constant liquid level. The heat transfer tubes 10a are introduced perpendicularly into the reactor 1.

   In the lower main manifold 93, steam is introduced through line 98. When the reaction liquid is heated, the water vapor remaining unconsumed after heating the reaction liquid in the jacket 10b and the tubes 10a, is separated. in a liquid phase and a vapor phase in line 92 and, during the cooling period to remove the heat of reaction, the water vapor formed by evaporation of the water in the chimney 10b and thei tubos 10a as a result of the heat of reaction is similarly separated into a vapor phase and a liquid phase in manifold 92.

   The water vapor formed is introduced, through line 99, into steam drum 91, in which the entrained liquid particles are further separated. The water vapor is then discharged through line 100.



  The entrained liquid particles and the water brought into the steam drum 91 via the line 94 returning to the sealer 92 via the line 98.



   Likewise, so that the jacket 10b and the heat transfer tubes 10a always remain filled with water, the liquid level of the manifold 92 is kept constant.

 <Desc / Clms Page number 24>

 When the level rises, the excess water is brought to the steam drum 91 through line 97. The water contained in line 92 goes down, through line 96, into line 93 and enters the jacket 10b. and the heat transfer tubes 10a.

   In this way, a natural circulation is obtained. The reference numerals 101 and 102 respectively denote the connection of the pipe 93 to the jacket and that of the pipe 92 to the latter,
When this temperature control system is provided, at the start of the operation, water is charged up to the level of vapor / liquid separation of the pipe 92 and water vapor at a higher temperature. to that of the reaction is introduced into this water through the lower pipe 98, in order to heat the reaction liquid contained in the reactor to the predetermined reaction temperature.

   When this temperature is reached the reaction material is fed into the reactor at a rate at which the level of liquid 11 is kept constant and the corresponding amount of reaction product is withdrawn from outlet 4 continuously or intermittently.



   Since the reaction is exothermic, it may be necessary to remove excess heat as the reaction proceeds. In this case, the valve 100 'provided on the line 100 is controlled to modify the pressure of the water vapor in the drum 91. Then, the water vapor supplied by the line 98 is cooled to its saturation point and , due to the phenomenon of latent heat of evaporation, the excess heat is removed in the process of forming water vapor. Therefore, the transfer from heating to cooling is carried out in a very regular manner. and the variations in temperature are very quickly brought down to a constant level.

   Normally, the water vapor can be constantly

 <Desc / Clms Page number 25>

 supplied through line 98 without exerting any adverse effect on the temperature control, but from an economic point of view it is preferable to control the quantity of steam
 EMI25.1
 .'1, water by means of a valve.



     -Likewise, when the reaction passes from cooling to heating or vice versa during the normal state, following one or the other external disturbance (for example an error in pumping the liquid containing the p-dialkylbenzene), the pressure in drum 91 rises or falls according to individual conditions to cause steam heating or cooling: by the latent heat of evaporation of the water, so that the reaction temperature is kept exactly constant.



   Obviously, the above temperature control system can be implemented using an appropriate liquid and vapors thereof (other than water and water vapor) depending on the reaction temperature chosen.



   Consequently, the temperature control system illustrated in FIG. 9 can be used to carry out the method of the invention in a regular and continuous manner at a predetermined and constant temperature level,
This method can be implemented satisfactorily with a simple apparatus according to the invention, but it is also possible to combine several apparatuses of this type in series. In other words, the reaction liquid containing solid terephthalic acid withdrawn from the outlet at the bottom of the first reactor can be fed directly into the material feed line of the second reactor, to be there again. subjected to a reaction to form terephthalic acid according to

 <Desc / Clms Page number 26>

 invention.

   This operation can be repeated several times and thus, high yields of high purity terephthalic acid can be obtained.



   In order to recover terephthalic acid from the reaction mixture obtained according to the invention, any known means of solid / liquid separation can be applied.



    Thus, by conventional means such as filtration, centrifugal filtration and centrifugal sedimentation, the mother liquor and terephthalic acid can be separated in the reaction mixture. Preferably, the operating temperature for the separation of terephthalic acid is between 50 ° C. and the boiling point of the liquid reaction medium under normal pressure.

   The crude terephthalic acid thus recovered can be used as it is or it can be further purified,
Heretofore, the details of the invention have been described with reference to Figures 1 to 9 but, in order to better understand the invention further, Figure 10 illustrates, in diagram form, an example of the entire operating system of the process according to the invention,
In Fig. 10 the flow will first be explained with reference to the reaction product, Each predetermined amount of p-dialkoylbenzene, liquid reaction medium (acetic acid in this specific case) and a metal catalyst. heavy (in this specific example, cobalt acetate), is supplied respectively through pipes 103,

   104 and 105 in the raw material preparation tank 106 from where the starting mixture is fed continuously into the reactor 1 at a predetermined rate. In reactor 1, a gas containing molecular oxygen (air, in this specific example) is supplied from a gas reservoir 141, through the lower part of this reactor, through the first injector.

 <Desc / Clms Page number 27>

 6 and the second gas injector 51. In this way, the reaction materials and the air are brought into intimate contact in the reactor 1, as has been described with reference to FIGS. 1 to 9, for carry out the envisaged oxidation reaction under the predetermined reaction conditions.



   The reaction product, transformed into a slurry and withdrawn through the outlet 4 provided in the lower part of the reactor 1, is separated from the mother liquor contained in the reaction product at the solid / liquid separator 107 and the solid component, i.e. ie the crude terephthalic acid, enters the washing vessel 110, via line 108, to be washed there with acetic acid, The acid in turn is sent to another solid / liquid separator 113, via line 111, to be separated there from the washing product, then the solid and cleaned terephthalic acid is sent to a dryer 116, via line 114, then it is dried, withdrawn via line 117 and possibly further refined.



   The oxidation filtrate and the washing filtrate, each separated in the solid / liquid separators 107 and 113, are brought to a distillation column 122, respectively through lines 109 and 115. The acetic acid and the acetate of The cobalt used as catalyst are recovered from the pipe 132 attached to the lower part of the distillation column 122, then they are recycled, through the pipe 133, into the aforementioned tank 106 where the raw material is prepared. From a lower part of the distillation column 122, the acetic acid or that containing water is recovered by the line 136 in the form of vapor which is cooled and condensed in the condenser 138, to be recycled in the washing container 110 via line 139.



   Likewise, the vapors of acetic acid, which

 <Desc / Clms Page number 28>

   which contain water and which are withdrawn from dryer 116 through line 118, are cooled and condensed in refrigerant 119 and are recycled in the same manner to washing vessel 110 through line 120,
At the bottom of the distillation column 122, there is provided a reheating boiler 135 and part of the acetic acid withdrawn via line 132 is sent to this reheating boiler 135 via line 134 to be again evaporated there and recycled in the distillation column 122,
Likewise,

     p-dialkoylbenzene and water in vapor form are sent from the top of distillation column 122 to condenser 124 via line 123, to be cooled and condensed there,
The water and the p-dialkoylbenzene thus condensed are sent from the condenser 124 to a settling tank 126 via the line 125 and, in this settling tank, the p-dialkoylbenzene is separated from the water in the form of two different phases, The p-dialkoylbenzene is recycled, via line 127, into the tank 106 for preparing the raw material,
According to the present invention, p-dialkoylbenzene is hardly contained in the oxidation filtrate and thus the amount of p-dialkoylbenzene to be separated in settling tank 126 is very small.

   so that it practically does not affect the yield of terephthalic acid. However, p-dialkoylbenzene can be recovered further to be used effectively.



   The water constituting the lower phase of the settling tank 126 is evacuated outside the reaction system through line 131.



   As indicated above, in reactor 1, the oxidation envisaged is continued under the conditions

 <Desc / Clms Page number 29>

 predetermined reactions and, after the reaction, the exhaust gas is sent to the reflux condenser 142 through line 3.
 EMI29.1
 



  1 In the if12 reflux refrigeration the stripping gas is cooled, while the p-dixileoylbeiizèilo and part of the acetic acid entrained by the gas are condensed. Exhaust gas is sent to refrigerant 144 through line 143. Hence, the p-dialkylbenzene and acetic acid remaining in the gas are further condensed in refrigerant 144 and the gas is sent to a gas separator. liquid 146 through line 145, while the condensation products are separated. The remaining gas enters the lower part of an absorption column 149 through column 148.

   At the upper part of this absorption column 149, a part of the water separated in the settling tank 126 is supplied through line 130, so that the exhaust gas supplied through line 148 is brought into contact with. the water coming from the IJO line, thus causing the acetic acid from the gas to be absorbed into the water. If the exhaust gas still contains p-dialkoylbenzene, a further absorption device can be provided so that the p-dialkoylbonzene can be absorbed, for example, in acetic acid or an aqueous solution of the latter, before being sent to the abovementioned absorption column 149.

   The exhaust gas is discharged to the atmosphere through the top of the absorption column 149 and the residue is supplied to the distillation column 122 through the line 151.



   Likewise, the p-dialkylbenzene and acetic acid condensed in the reflux condenser 142 return through line 3 to be recycled to the reactor 1. The condensation product comprising the p-dialkoylbonzene and acetic acid formed in the condenser 144. enter the

 <Desc / Clms Page number 30>

 gas / liquid separator 146 via line 145, while the condensation product is separated from the exhaust gas and returned to reactor 1.



     By using the apparatus of the present invention in the series of the operating system described above, high purity terephthalic acid can be continuously obtained in high yield, consuming little acetic acid and recycling the acid very efficiently. oata.- lyser.



   As the raw material for the preparation of terephthalic acid, to which the apparatus and method of the invention are applicable, p-dial-coylbenzenes such as p-xylone, p-cymene and intermediate oxidation products of p-dialkylbenzenes such as p-toluic acid, 4-carboxybonzaldehyde, and the like. or a mixture thereof, the preferred product being p-xylene.



   As the molecular oxygen or as a gas containing molecular oxygen for the oxidation of the above raw materials, there can be employed pure oxygen or mixtures of oxygen with inert gases such as nitrogen, nitrogen. argon, carbon dioxide, etc., air being the gas most readily obtainable for this purpose,
According to the invention, the oxidation of the above-mentioned raw materials with the gas containing molecular oxygen is carried out in a liquid reaction medium.

   As the liquid reaction medium, use is preferably made of aliphatic monocarboxylic acids of 2 to 4 carbon atoms such as acetic acid, propionic acid and butyric acid, acetic acid being most preferred.
The oxidation is also carried out in the presence of a heavy metal catalyst according to the invention.

   As the heavy metal catalyst, compounds of

 <Desc / Clms Page number 31>

 cobalt, manganese, silver, molybdenum, niobium, etc., in particular salts of organic acids such as acetates of these metals, compounds of cobalt, manganese, etc. may also contain small amounts of other metal compounds such as scodium, yttrium, lanthanum, neodymium, gadolinium, thorium, zirconium, hafnium, etc. compounds.

   According to the invention, the oxidation reaction can be activated by using at the same time activating or initiating agents such as bromine compounds, for example ammonium bromide, a methylene ketone, an aldehyde. , ozone (03), etc., with the above metal compound catalyst.



   In the above description, the particularly preferred catalysts are those cobalt compounds which are soluble in the above solvents of aliphatic monocarboxylic acids of 2-4 carbon atoms, for example the organic diacid salts of cobalt such as. cobalt acetate.



   When carrying out the process of the invention, the reaction temperature is not critical as long as it allows the oxidation of the p-dialkylbenzene in the aliphatic monocarboxylic acid solvent, in the presence of the catalyst. of heavy metal, with a gas containing molecular oxygen to form terephthalic acid, However, normally this temperature is in the range of 80-1500C, especially 90-140 C.



  At temperatures below the lower limit of the range specified above, terephthalic acid cannot be obtained in appreciably high yields, and at temperatures above the upper limit high yields cannot be expected and in addition combustion of the aliphatic monocarboxylic acid used as a solvent occurs, since

 <Desc / Clms Page number 32>

 that it is oxidized by the gas containing molecular oxygen,
The pressure prevailing inside the reactor can be between atmospheric pressure and 100 atmospheres, preferably between atmospheric pressure and 50 atmospheres,
During the implementation of the method of the invention,

   it is desirable to measure the concentration of molecular oxygen in the gas in the gas phase of the upper part of the reactor and to carry out the oxidation while diluting the gas in the gas phase with one or more inert gases or again by adjusting the feed rate of the gas containing molecular oxygen, so as to prevent the composition of the gas from becoming explosive, the operation thus being carried out under safe conditions,
According to the present invention, the transformation product from p-dialkylbenzene is essentially terephthalic acid or an intermediate oxidation product to be converted into terephthalic acid.



  Therefore, by recycling and oxidizing a mother liquor containing this intermediate oxidation product, terephthalic acid can be obtained in extremely high yield,
The invention will be described below with reference to the implementation examples which in no way limit the scope of the invention.



   In the examples, unless otherwise indicated, all the percentages and all the parts are by weight, Likewise, the yields of terephthalic acid are the yields in a single pass of the p-dialkoylbenzene charged to the reactor 1, these yields being expressed in moles percent.

 <Desc / Clms Page number 33>

 



  Examples 1- 7
A stainless steel pressure reactor having the structure shown in Figure 1 was employed, the details of this structure being as follows: The top of the reactor was connected to a condenser through a condenser. at reflux;

   the vertical angle of the bottom of the reactor was 60 and the reactor was fitted with a first single-nozzle gas injector, a draft tube located above, a gas distributor of the construction shown in Figure 4, which had been placed above the draw tube, a material supply line, 4 sample collection bundles distributed in the direction perpendicular to the the reaction column, so as to be able to take samples of the liquid retained in the column at different levels, as well as three looks provided to be able to observe the behavior of the reactor from the outside. The ratio of the inside diameter to the height of the column was 17.

   The position of the material feed line could vary 20 cm above the liquid level and so that the ratio Ó / L was 1/8, 1/4, 1/3, 1 / 2 and 3/4.



    L being the distance between the first injector of gaa, and the level of reaction liquid in the column, while Ó represents the distance between the level of reaction liquid and the material feed line,
In the above reactor, 144.7 parts of acetic acid and 22.3 parts of 4-molecule cobalt acetate (Co (OAc) 2.4H2O) were charged, and the air in the draft tube from the first gas injector at a flow rate giving a surface air velocity of 1.73 cm3 / cm2.sec.

   While maintaining the pressure inside the system (detected at the pressure sensing element 13 of figure 1) at the predetermined values indicated

 <Desc / Clms Page number 34>

 in Table 1, hot water was charged to the reactor jacket and the cooling tubes which were introduced perpendicularly into the reactor up to the level of gas / liquid separation; then, the system was heated by passing 3.0 kg / cm 2 of water vapor through the bottom of the jacket.

   When the internal temperature detected at the temperature sensor of FIG. 1 reached the values indicated in Table 1, a starting reaction mixture consisting of 11.75% p-xylene, 76.50% acetic acid and 11.75% cobalt acetate containing 4 water molecules (Co (OAc) 2.4H2o) at a rate of 20.9 parts per hour through the material feed line located at different levels, in order to vary the Ó / L ratio, as indicated in Table 1. At the same time, by leaving the part provided at the bottom of the reactor, the reaction product was continuously withdrawn. in an amount corresponding to that of the charged material, while the liquid level was kept constant in the reactor.

   About 40 hours after the start of the reaction, the reaction state was constant and the operation was continued under the conditions specified above. The results are also given in Table 1,

 <Desc / Clms Page number 35>

 Table 1
 EMI35.1
 
<tb> Conditions <SEP> of <SEP> the <SEP> reaction <SEP> Efficiency <SEP> in
<tb>
 
 EMI35.2
 tereph acid- Ex. Tomp.

   Acid pressure terepl) - nc OC (kg / cm2 {IL talic manom6- (moles ¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯) ¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯
 EMI35.3
 
<tb> 1 <SEP> 120 <SEP> 10 <SEP> 1/4 <SEP> 80.1
<tb>
<tb> 2 <SEP> "<SEP> 15 <SEP>" <SEP> 82.3
<tb>
<tb>
<tb> 3 <SEP> "<SEP> 20 <SEP>" <SEP> 84.8
<tb>
<tb>
<tb> 4 <SEP> "<SEP> 1/3 <SEP> 84.6
<tb>
<tb>
<tb> 5 <SEP> 130 <SEP> 10 <SEP> 1/4 <SEP> 80.3
<tb>
<tb>
<tb> 6 <SEP> "<SEP> 15 <SEP>" <SEP> 82.5
<tb>
<tb>
<tb> 7 <SEP> 20 <SEP> 84.7
<tb>
 Witnesses 1 4
An analogous reaction was carried out in the same manner as in Examples 1-7 at the reaction temperature of 120 ° C. and under a pressure of 20 kg / cm 2 gauge, the position of the material feed Ó / L variant as shown in Table 2, The results are shown in Table 2.



   Table 2
 EMI35.4
 
<tb> Control <SEP> Yield <SEP> in acid <SEP>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Terephthalic <SEP> Ó / L <SEP> indicator
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> nit <SEP> (moles <SEP>%)
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 1 <SEP> Greater <SEP> of <SEP> 20cm <SEP> 73,
<tb>
<tb>
<tb>
<tb>
<tb> at <SEP> level <SEP> of <SEP> li-
<tb>
<tb>
<tb>
<tb>
<tb> what
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 2 <SEP> 1/8 <SEP> 79.1
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 3 <SEP> 1/2 <SEP> 79.8
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 3/4 <SEP> 75.0
<tb>
 Examples 8- 14
The reaction described in the examples was repeated.

 <Desc / Clms Page number 36>

 1-7, with the exception that, as a gas distributor, the second gas injector with downward perforations has been used,

   air being fed into the draft tube from the first gas injector at a surface air velocity of 1.73 cm3 / cm2 sec., the remainder of the air being fed by the second gas injector to the -above the draw tube. The @ / L ratio was set to 1/4, while in each run the reaction pressure and temperature were varied as shown in Table 3.



  The results are shown in the same table,
Board *)
 EMI36.1
 
<tb> Conditions <SEP> of <SEP> the <SEP> Yield <SEP> Composition <SEP> of the <SEP> product
<tb>
<tb> reaction <SEP> in <SEP> acid <SEP> reactional <SEP> (%)
<tb>
<tb> Ex. <SEP> Pressure <SEP>! ## *** '<SEP> terephta- <SEP> Acid <SEP> téré- <SEP> 4-carboxy-
<tb>
 
 EMI36.2
 n Temp.

   (Icglcmo U lic Acid tere "4-carboxy-
 EMI36.3
 
<tb> (C) <SEP> manom- <SEP> ci * <SEP> (moles <SEP>%) <SEP> phthalic <SEP> benzalde-
<tb>
<tb>
<tb> triques <SEP> hyde
<tb>
<tb>
<tb>
<tb>
<tb> 8 <SEP> 120 <SEP> 10 <SEP> 0.3 <SEP> 81.3 <SEP> 84.3 <SEP> 1.85
<tb>
<tb>
<tb>
<tb>
<tb> 9 <SEP> "<SEP> 15 <SEP>" <SEP> 83.2 <SEP> 85.1 <SEP> 1.79
<tb>
<tb>
<tb>
<tb>
<tb> 10 <SEP> "<SEP> 20 <SEP>" <SEP> 85.2 <SEP> 86.1 <SEP> 1.79
<tb>
<tb>
<tb>
<tb>
<tb> 11 <SEP> "<SEP> 0.4 <SEP> 85.8 <SEP> 86.3 <SEP> 1.78
<tb>
<tb>
<tb>
<tb>
<tb> 12 <SEP> "<SEP> 0.8 <SEP> 84.9 <SEP> 85.8 <SEP> 1.76
<tb>
<tb>
<tb>
<tb>
<tb> 13 <SEP> "<SEP>" <SEP> 1.0 <SEP> 84.5 <SEP> 85.6 <SEP> 1.78
<tb>
<tb>
<tb>
<tb>
<tb> 14 <SEP> 130 <SEP> "<SEP> 0.3 <SEP> 85.4 <SEP> 86.2 <SEP> 1,

  81
<tb>
 * Surface velocity of the air to be brought into the
 EMI36.4
 column from the first gas injector (cm3 / cm2, aec,
During the operation, the dispersion of the air bubbles was observed by sight glasses provided on the reactor.



  In all of the examples the air dispersion was satisfied. health, as has been observed in all three
 EMI36.5
 (0.002ho, O, J59L. 0.892L) o Near the manholes, groups of air bubbles dispersed uniformly were observed
Likewise, during the process of Example 10, samples were taken of the liquid retained in

 <Desc / Clms Page number 37>

 the column through the four reactor sampling holes and the slurry concentrations of the samples were determined. The results are shown in Table 4.

   On the other hand, the positions of the records and August sample collection boots expressed from the measurement of the level of reaction liquid in the column with reference to the length L, which is the distance between the level of liquid and the first. gas injector *
Table 4
 EMI37.1
 
<tb> Position <SEP> of <SEP> the <SEP> Concentration
<tb>
<tb>
<tb> boot <SEP> from <SEP> do <SEP> the <SEP> porridge <SEP> Trailers
<tb>
<tb>
<tb>
<tb> direct debit:

   <SEP> (%)
<tb>
<tb>
<tb> dl <SEP> éelbatitil <SEP> Ions <SEP>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 0.217L <SEP> 8.6
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> o, 678L <SEP> 8.8
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 0.928L <SEP> 17.6 <SEP> second <SEP> injectour
<tb>
<tb>
<tb>
<tb> from <SEP> gas
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 1.00L <SEP> 18.2 <SEP> first <SEP> injector
<tb>
<tb>
<tb>
<tb> from <SEP> gas
<tb>
 
Therefore, below the second gas injector, no abrupt variation was observed in the concentration of the slurry and, in the area below the second gas injector, which was located above the gas tube. draw, the crude terephthalic acid particles were in uniform suspension.



  Witness
A similar reaction was carried out in the same manner as that described in Examples 8-14, with the exception that air was not supplied from the first gas injector, i.e. air was not blown into the draft tube, but air was supplied from the second gas injector above the draft tube at a superficial air velocity in the column

 <Desc / Clms Page number 38>

 of 1.73 cm3 / cm2.sec. at a reaction temperature of 120C and under a pressure of 20 kg / cm2 gauge, Lea results are shown in Table 5.



   Table 5
 EMI38.1
 
<tb> Position <SEP> of <SEP> the <SEP> Concentration
<tb>
<tb> boot <SEP> of <SEP> of <SEP> the <SEP> porridge <SEP> Noticed
<tb>
<tb>
<tb> direct debit <SEP> (%)
<tb>
<tb>
<tb> samples
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 0.217L <SEP> 8.7
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> o, 678L <SEP> 8.8
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 0,928L <SEP> 12,2 <SEP> second <SEP> injector
<tb>
<tb>
<tb> from <SEP> gas
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> # <SEP> 1.00L <SEP> 18.1 <SEP> first <SEP> injector
<tb>
<tb>
<tb> from <SEP> gas
<tb>
 
Therefore, in the area below the second gas injector, a sudden change in the concentration of the slurry was observed, the area becoming, so to speak, a dead space. Therefore, in this area ,

   there was no contact between the crude terephthalic acid particles and air and, two weeks after the start of the reaction, the outlet of the reaction product was obstructed by the deposit of the product. It was therefore impossible to achieve a stable operation for a prolonged period, Witness 6
Witness 3 was repeated, with the exception that air was not drawn in from the second gas injector but from the first gas injector, below the draft tube, air was brought in. Air at a superficial velocity of 1.73 cm3 / cm2. The obtained yield of terephthalic acid was 75.2 mole%.



   During the operation, the dieper- sion of the air bubbles was observed through the sight glasses provided on the reactor,

 <Desc / Clms Page number 39>

 In the vicinity of the 0.0024L and 0.359L manholes, the state of dispersion was satisfactory and groups of bubbles evenly distributed were observed. However, around the 0.892L manholes, few bubbles were observed and the vertical bubble dispersion along the reactor was uneven.



  Examples 15 - 21 Examples 8-14 were repeated with the following changes made thereto the reaction temperature was 120 ° C: the pressure was 20 kg / cm 2 gauge; the position of the material feed line, t / L, was 1/4; the surface velocity of air supplied by the first gas injector was 0.3 cm3 / cm2.second;

   the rest of the air was supplied by the second gas injector so that the total quantity of air had the surface velocity shown in Table 6 below. The results are also shown in the same table,

 <Desc / Clms Page number 40>

   Table 6
 EMI40.1
 
<tb> Composition <SEP> of <SEP> proCharge <SEP> of <SEP> material <SEP> Conditions <SEP> of <SEP> the <SEP> reaction <SEP> Speed <SEP> of <SEP> Rate <SEP > of <SEP> produc- <SEP> Yield <SEP> in <SEP> reaction product <SEP>
<tb> Growth <SEP> Acid <SEP> <SEP> Acid <SEP> Tere- <SEP> (%)

  
<tb> Terephthalic <SEP> <SEP> <SEP> acetate <SEP> terephthalic <SEP> phthalic
<tb> n <SEP> acetic <SEP> cobalt <SEP> to <SEP> 4 <SEP> of <SEP> lionide <SEP> ficialle <SEP> of air <SEP> paties / hour <SEP> moles <SEP >% <SEP> Tere <SEP> acid <SEP> 4-carboxyacetic <SEP> of <SEP> liquid <SEP> ficial <SEP> of air <SEP> mm <SEP> hour <SEP> phthalic <SEP> benzaldeeparted <SEP> molecules <SEP> parts <SEP> h <SEP> cm3 <SEP> cm2.

   <SEP> sec.
<tb> of water <SEP> hyde
<tb> (parts)
<tb> 15 <SEP> 155.1 <SEP> 24, o <SEP> 22.5 <SEP> o, 80 <SEP> o, oo45 <SEP> 3.37 <SEP> 81.3 <SEP> 84 , 3 <SEP> 1.83
<tb> 16 <SEP> 153.4 <SEP> 23.6 <SEP> 22.1 <SEP> 1.04 <SEP> o, oo41 <SEP> 3.35 <SEP> 82.4 <SEP> 84.7 <SEP> 1.81
<tb> 17 <SEP> 150.8 <SEP> 23.2 <SEP> 21.7 <SEP> 1.27 <SEP> 0.0022 <SEP> 3.21 <SEP> 80.2 <SEP> 83 , 7 <SEP> 1.80 <SEP>, <SEP>
<tb>
<tb> 18 <SEP> 148.2 <SEP> 22.8 <SEP> 21.3 <SEP> 1.50 <SEP> 0.0022 <SEP> 3.32 <SEP> 84.4 <SEP> 85 , 6 <SEP> 1.77
<tb> 19 <SEP> 144.7 <SEP> 22.3 <SEP> 20.9 <SEP> 1.73 <SEP> 0.0022 <SEP> 3.28 <SEP> 85.2 <SEP> 86 , 1 <SEP> 1.79 ....
<tb>



  20 <SEP> 128.2 <SEP> 19.7 <SEP> 18.7 <SEP> 3.00 <SEP> 0.0022 <SEP> 2.92 <SEP> 84.6 <SEP> 85.7 < SEP> 1.78 ...
<tb>



  21 <SEP> 70.8 <SEP> 10.9 <SEP> 10.2 <SEP> 7.00 <SEP> 0.0022 <SEP> 1.53 <SEP> 83.1 <SEP> 85.1 < SEP> 1.74,
<tb>
 

 <Desc / Clms Page number 41>

 Witnesses 7-8
The same reaction was carried out in a manner analogous to that in Examples 15-21, with the exception that the experimental conditions were varied as shown in Table 7 below. The results are also shown in the same table.

 <Desc / Clms Page number 42>

 



    Board
 EMI42.1
 
<tb> Composition <SEP> of <SEP> proCharge <SEP> of <SEP> material <SEP> Conditions <SEP> of <SEP> the <SEP> reaction <SEP> Speed <SEP> of <SEP> Rate <SEP > of <SEP> produc- <SEP> Yield <SEP> in <SEP> reaction product <SEP>
<tb> T- <SEP> growth <SEP> acid <SEP> <SEP> acid <SEP> tere- <SEP> quit <SEP> react
<tb> less <SEP> Acid <SEP> Acetate <SEP> of <SEP> of <SEP> scale- <SEP> terephthalic <SEP> phthalic
<tb> n <SEP> Acid <SEP> cobalt <SEP> to <SEP> 4 <SEP> Power supply <SEP> Speed <SEP> super- <SEP> the <SEP> parts / hour <SEP> moles% <SEP > Tere-4-carboxy- acid <SEP>
<tb>
 
 EMI42.2
 acetic molecules of air ficial liquid (mrt1 / hour) bzz phthalic benzalde-
 EMI42.3
 
<tb> (parts) <SEP> of water <SEP> (parts / h) <SEP> (cm3 / cm2.sec.) <SEP> hyde
<tb> (parts)
<tb>
 
 EMI42.4
 7 15995 24,

  5 23.0 0.56 0.0510 2.39 5693 7392 2 ,. : 156.9 24.1 22.6 0.70 0.0190 2.51 6o, l 7592 2 '' ::; 1

 <Desc / Clms Page number 43>

 During the tests, it became difficult to control the temperature due to the adhesion of the scales, and it was impossible to perform stable operation for a prolonged period.



  Examples 22- 25
Example 19 was repeated, with the exception that the position of the material feed line 'IL was 1/3'. The results are shown in Table 8 below.

 <Desc / Clms Page number 44>

 



    Table 8
 EMI44.1
 
<tb> Composition <SEP> of <SEP> proCharge <SEP> of <SEP> material <SEP> Conditions <SEP> of <SEP> the <SEP> reaction <SEP> Speed <SEP> of <SEP> Rate <SEP > of <SEP> produc- <SEP> Yield <SEP> in <SEP> reaction product <SEP>
<tb> growth <SEP> acid <SEP> <SEP> acida <SEP> téré- <SEP> (%)
<tb>
 
 EMI44.2
 ###########, ##########
 EMI44.3
 
<tb> n <SEP> Acid <SEP> cobalt <SEP> to <SEP> 4 <SEP> Power supply <SEP> Speed <SEP> super- <SEP> the <SEP> (parts / hour) <SEP> (moles <SEP>%) <SEP> Acid <SEP> ter- <SEP> 4-carboxyacetic <SEP> molecules <SEP> of <SEP> liquid <SEP> ficial <SEP> of air <SEP> (mm / hour) <SEP> phthalic <SEP> benzalde-
<tb> (parts) <SEP> molecules <SEP> (parts / h) <SEP> (cm3 / cm2.sec.)

   <SEP> hyde
<tb>
 
 EMI44.4
 ¯¯¯¯¯¯¯¯¯¯¯¯ (parts) ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
 EMI44.5
 
<tb> 22 <SEP> 153.4 <SEP> 23.6 <SEP> 22.1 <SEP> 1.04 <SEP> 0.0042 <SEP> 3.34 <SEP> 82.1 <SEP> 84 , 6 <SEP> 1.82 <SEP>. <SEP>
<tb>



  23 <SEP> 148.2 <SEP> 22.8 <SEP> 21.3 <SEP> 1.50 <SEP> 0.0022 <SEP> 3.29 <SEP> 84.0 <SEP> 85.6 < SEP> 1.77.
<tb>



  24 <SEP> 128.2 <SEP> 19.7 <SEP> 18.7 <SEP> 3.00 <SEP> 0.0022 <SEP> 2.91 <SEP> 84.3 <SEP> 85.8 < SEP> 1.79
<tb>
 

 <Desc / Clms Page number 45>

 Example 26
The example was repeated19. with the exception that, as a feed of initial material, a mixture consisting of 130.0 parts of acetic acid, of 4.73 parts of cobalt acetate with 4 molecules of water was charged.
 EMI45.1
 (CQ (OAc2,111i20 and 11.47 parts of methyl ethyl ketono, while, as raw material, a mixture consisting of 11.9% by weight of p-xylene, of 77.2% by weight was charged). weight of a-ketic acid, 2.8% by weight of cobalt acetate with 4 water molecules and 8,

  1% by weight of methyl ethyl ketone, Likewise, the reaction temperature was set to 135 C.



  The roundness of terephthalic acid was 82.4 mole%.



  Examples 27 and 28
Example 19 was repeated, with the exception that, as the gas containing molecular oxygen, air containing 0.5% by volume of ozone was employed and the reaction temperature was varied as iiidi - as in Table 9 below, The results are shown in the same table,
Table 9
 EMI45.2
 
<tb> Ex.

   <SEP> Temperature <SEP> do <SEP> Efficiency <SEP> in acid <SEP>
<tb> n <SEP> the <SEP> terephthalic <SEP> reaction
<tb> (C) <SEP> (moles <SEP>%)
<tb>
<tb> 27 <SEP> 105 <SEP> 80.5
<tb>
<tb> 28 <SEP> 120 <SEP> 85.2
<tb>
 Example 29
Example 19 was repeated with the exception that, as the initial liquid feed, a liquid mixture consisting of 133.4 parts of acetic acid, 4.24 parts of cobalt acetate to 4 was charged. molecules of water and 10.23 parts of acetaldehyde and, as material

 <Desc / Clms Page number 46>

   First, a mixture of 10.84% by weight of p-xylene, 80.4% by weight of acetic alcohol, 2% by weight was charged to the reactor.

  56% by weight of cobalt acetate containing 4 molecules of water (Co (OAc) 2.4H2O) and 6.2% by weight of acetaldehyde. By carrying out the reaction at 115 ° C., a yield of 82.8 mole% of terephthalic acid was obtained, Example 30
Example 19 was repeated with the exception that, as the starting material feed, a liquid mixture consisting of 123.7 parts of acetic acid, 4.75 parts of 4-molecule cobalt acetate was charged. of water and 0.48 part of zirconium acetate (ZrO (OAc) 2.nH2O) and, as raw material, a liquid mixture consisting of 12.86% by weight of p -xylene, 83.61% by weight of acetic acid, 3,

  21% by weight of cobalt acetate containing 4 molecules of water and 0.32% by weight of zirconium acetate. By carrying out the reaction under a pressure of 10 kg / cm2 gauge, a yield was obtained of 85.2 mole% of terephthalic acid.



  Example 31
Example 19 was repeated, with the exception that acetic acid was replaced by propionic acid. The yield of terephthalic acid obtained was 83.2 mole%.



  Examples 32- 34
A reactor of the type illustrated in FIG. 7 was used, at the bottom of which was fixed a cylindrical branch. This branch had an internal diameter equal to one third of that of the reactor and a length equal to five times that of the internal diameter. As the starting material, a mixture consisting of 128.2 parts of acetic acid and 19.7 parts of 4-molecular-water cobalt acetate was charged, and through the first gas injector was supplied.

 <Desc / Clms Page number 47>

 air at a surface velocity in the reactor of 0.3 cm3 / cm2 sec.

   The remainder of the air was supplied by the second gas injector at a rate giving the total quantity of air in the column a superficial velocity of 3.0 cm3 cm2, aec, At a reaction temperature of 120 ° C. and at a pressure of 10 kg / cm2 sec., a raw material of the composition given in the same table was charged at a rate specified in Table 10 through the material feed line located at Ó / L of 1/4.



   At the same time, by means of a preheater, part of the condensate liquid of the reactor exhaust gas was preheated to 110 ° C., which was condensed in the refrigerant connected to the top of the reactor, and then brought this part to the lower part of the branch as a flushing liquid at the rate shown in Table 10. The remainder of the condensation liquid was refluxed into the upper part of the reactor. Subsequently, the substitution of the liquid due to the rinsing was carried out in this branch and, through the lower part thereof, the contents of the reactor were discharged intermittently in the quantities corresponding to those of the feed. of matter.



   Under the above reaction conditions, the reaction reached a constant state after about 40 hours, and through the outlet of the reaction product provided in the branch, the reaction product was regularly withdrawn in an amount corresponding to that of the initial liquid mixture. tial, which was concentrated to a solids content of about 45%.



   During the continuous reaction process, under the above conditions, the composition of the reaction liquid in the reactor was approximately as follows: p-xylene and its oxidation product, calculated as p-xylene / acid. acetic / cobalt acetate, corresponded to 20: 130: 20.

 <Desc / Clms Page number 48>

 



  Table 10 also indicates the yields of terephthalic acid, the composition of the reaction products, as well as the amounts of cobalt acetate containing 4 water molecules, contained in the crude terephthalic acid obtained by separating and drying the reaction products.



   The catalyst contents indicated in Table 10 are the parts of catalyst contained in 100 parts of crude terephthalic acid, calculated as cobalt acetate with 4 water molecules,

 <Desc / Clms Page number 49>

   Table 10
 EMI49.1
 
<tb> Composition <SEP> of the <SEP> liquid <SEP> Composition <SEP> of the <SEP> produced
<tb> reaction <SEP> Feed <SEP> Feed <SEP> Yield <SEP> in <SEP> reaction <SEP> Content <SEP> in <SEP> cataen <SEP> weight) <SEP> of <SEP> liquid < SEP> of <SEP> liquid <SEP> acid <SEP> téré- <SEP> (% <SEP> in <SEP> weight) <SEP> lyser <SEP> (parts /
<tb> Acetate <SEP> of <SEP> (parts / h) <SEP> of <SEP> rinse <SEP> phthalic <SEP> 100 <SEP> parts
<tb>
 
 EMI49.2
 p-xylene Acid coba (parts / b) (moles Acid tere- 4-çartoxy- of tere acid ...

   
 EMI49.3
 
<tb> p-xylene <SEP> acetic <SEP> cobalt <SEP> to <SEP> 4 <SEP> parts / n <SEP> moles <SEP>% <SEP> Acid <SEP> tere-4-carboxy- < SEP> acid <SEP> tere-
<tb> ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯d'eau <SEP> ¯¯¯¯¯¯¯¯¯¯ <SEP> hyde
<tb> 32 <SEP> 36.7 <SEP> 56.8 <SEP> 6.5 <SEP> 4.59 <SEP> 4.20 <SEP> 87.9 <SEP> 87.3 <SEP> 1 , 80 <SEP> $ 2.17
<tb>
 
 EMI49.4
 33 371l 5 +. 2 8.7 tso 3.18 85.2 86.1 1.81 3.21. ; 34, 1 51 95 11.4 ka87 2, la 84.0 85.6 1183 3.81 t * **, ¯¯ *. * -'- "- ##### '## --- L #####.-. - .........-.... # ...- - .. ".... #### .., ¯¯ - ### # ¯¯¯¯ W ** '. **.

 <Desc / Clms Page number 50>

 



  Examples 35 - 36
Example 34 was repeated with the following modifications as a rinsing liquid, acetic acid or an aqueous solution of acetic acid of the type specified in Table 11 was charged at 2.10 parts per hour and, as raw material, we loaded into the reactor. a flow rate of 3.83 parts / hour, a mixture consisting of 57.4% by weight of p-xylene, 24.8% by weight of acetic acid and 17.8% by weight of acetate. cobalt with 4 water molecules.

   The results are shown in Table 11 below,
Table 11
 EMI50.1
 
<tb> <SEP> content in <SEP> Yield <SEP> Composition <SEP> of <SEP> product <SEP> catalyst
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> acid <SEP> ac- <SEP> in <SEP> acid <SEP> reaction <SEP> catalyst
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Ex. <SEP> tick <SEP> of <SEP> of <SEP> lique <SEP> (% <SEP> in <SEP> weight) <SEP> 100 <SEP> parts <SEP>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> n <SEP> liquid <SEP> of <SEP> lique <SEP> 4-carboxy- <SEP> of acid <SEP> t-
<tb>
 
 EMI50.2
 rinsing (moles Tere acid ..

   beuzaldÓ- tu0 shore tarties (moles Acid téré- betizalde- replitaliquo
 EMI50.3
 
<tb> phthalic <SEP> hyde <SEP> raw)
<tb> 35 <SEP> 100 <SEP> 84.4 <SEP> 85.6 <SEP> 1.83 <SEP> 3.84
<tb>
 
 EMI50.4
 36 90 84.1 85.4 1.83 J.81 Example 37
Example 20 was repeated at the reaction pressure of 10 kg / cm 2 gauge and recycling the catalyst and liquid medium according to the scheme of Figure 10.



   In other words, the raw material of the reaction was continuously fed into the reactor and the corresponding amounts of the contents of the reactor were continuously withdrawn from the outlet of the reaction product provided at the bottom of the reactor, while maintaining a level of. constant liquid, The crude terephthalic acid and the oxidative filtrate were separated from the reaction product by centrifugal separation at 80 C, The crude terephthalic acid was washed for 20 minutes 80 C with acetic acid

 <Desc / Clms Page number 51>

 with a water content of 10%, and then separated into washed terephthalic acid and washing filtrate by centrifugal separation at 80 ° C. The terephthalic acid thus washed was further dried in a dryer,

   
Since the oxidation and wash filtrates contained water which had formed by the oxidation reaction, in addition to acetic acid used as a solvent, cobalt acetate used as a catalyst. and intermediate oxidation products such as p-to- acid
 EMI51.1
 Fluid, 4-carboxybenzaldehydo, etc., water, in an amount corresponding to that formed by the reaction, was removed by distillation under reduced pressure of 250 mm Hg.

   The remaining filtrates were recycled for use in the reaction and washing. In this way, the middle fraction liquid of the distillation column was prepared, as well as the liquid mixture to be used for washing with acetic acid. containing 10% by weight of water which was recovered in the dryer,
In addition, through the bottom of the distillation column, the bottoms fraction which was dehydrated to a water toner of about 3.5 moles H2O / CO atom was continuously removed. P-xylene and acetic acid were changed at the bottom so that the composition of the latter was identical to the glue of the raw material employed in Example 20 and the composition was recycled to the reactor.



   Likewise, the exhaust gas, which was condensed in the reflux condenser and the refrigerant, and further separated from the condensation products by a gas / liquid separator, was subjected to backflow. high pressure gas absorption operations. Then, p-oxylene and acetic acid contained in the exhaust gas were recovered with acetic acid and water respectively

 <Desc / Clms Page number 52>

 the distillate from the distillation column,
In other words, the distillation tower consisted of two columns.

   The exhaust gas separated from the condensation products was introduced at the bottom of the first column and through the top of the first absorption column acetic acid was introduced in a concentration of almost 100%. The bottom fraction containing p-xylene was absorbed by acetic acid in the first column and was fed to the raw material preparation tank.

   The gas discharged from the first absorption column was introduced to the bottom of the second absorption column, while a portion of the distillation column from the still, which was essentially water, was added. fed from the top of this column, the bottom fraction from the second column, which contained acetic acid absorbed by the water, was fed to the distillation column with the above-mentioned oxidation and washing filtrates . The exhaust gas from the second column was discharged as is into the atmosphere.



   The operation was continued for a month under the above conditions. Table 12 below shows the quantities of dry terephthalic acid obtained from the p-xylene feed and the acetic acid added to the system to compensate for the ports,
Table 12
 EMI52.1
 
<tb> Power <SEP> from <SEP> outside <SEP> Evacuation <SEP> to <SEP> outside <SEP> of
<tb>
<tb>
<tb>
<tb> of the <SEP> systemē¯¯¯¯¯¯¯¯¯ <SEP> ¯¯¯¯¯¯¯¯¯¯systemē¯¯¯¯¯¯¯
<tb>
<tb>
<tb>
<tb> Substance <SEP> Quantity <SEP> Substance <SEP> Quantity
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Substance <SEP> (parts / maize) <SEP> Substance <SEP> (parts / month)
<tb>
<tb>
<tb>
<tb>
<tb> p-xylene <SEP> 1582 <SEP> acid <SEP> terried- <SEP> 2430
<tb>
<tb>
<tb> phthalic
<tb>
<tb>
<tb> sec
<tb>
<tb>
<tb>
<tb>
<tb> <SEP> acetic acid <SEP> 51,

  2
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> acetate <SEP> of <SEP> co- <SEP> - <SEP>
<tb>
<tb>
<tb>
<tb> balt <SEP> to <SEP> 4 <SEP> mo-
<tb>
<tb>
<tb>
<tb> <SEP> lecules of water
<tb>
 

 <Desc / Clms Page number 53>

   Meanwhile, the loss of cobalt acetate was practically nil.

 

Claims (1)

R E V E N D I C A T I O N S 1, Apparatus for the manufacture of terephthalic acid from p-dialkylbenzene or an oxidation intermediate oxidation product, characterized in that it comprises a reactor whose bottom decreases towards at the bottom, this reactor comprising a gas discharge pipe in its upper part, an outlet for the reaction product in the lower part, as well as a raw material feed pipe in a suitable intermediate position, a gas injector for supplying molecular oxygen or a gas containing molecular oxygen and opening into the lower part of the reactor, a draft tube with open top and bottom placed above the gas injector, as well as a gas distributor for dispersing molecular oxygen or the gas containing molecular oxygen in the reactor, this distributor being located above and at an appropriate distance from the draft tube, the reactor being also provided with a heating and / or cooling device to maintain the reaction material in the reactor at the predetermined reaction temperature, the p-dialkoylbonzene or its intermediate oxidation product, the liquid reaction medium and the catalyst thus being charged through the material feed line, while at least part of the molecular oxygen or molecular oxygen-containing gas is supplied through the gas injector. 2. Apparatus according to claim 1, characterized in that the gas distributor comprises a second gas injector having numerous perforations for <Desc / Clms Page number 54> supplying molecular oxygen or the gas containing molecular oxygen to the reactor. 3. Apparatus according to claim 2, characterized in that the numerous perforations are open downwards, 4. Apparatus according to claim 1, characterized in that a tubular section, the bottom of which is closed and the top of which opens into the reactor, is formed in the lower part of the reactor, this tubular section comprising an outlet for the reactor. reaction product and an inlet for the liquid reaction medium in its lower part. 5. A process for preparing terephthalic acid from p-dialkoylbenzene or an intermediate oxidation product thereof, which process comprises reacting a p-dialkylbenzene or its intermediate oxidation product with Molecular oxygen or a gas containing molecular oxygen in an aliphatic monocarboxylic acid solvent of 2 to 4 carbon atoms is present in a heavy metal catalyst, this process being characterized by what; (1) the molecular oxygen or the gas containing molecular oxygen is supplied by the first gas injector provided in the conical lower part of the reactor, into the reaction liquid contained in the latter; (2) the molecular oxygen or the gas containing molecular oxygen is dispersed in the reaction liquid by means of a draw tube provided above the open mouth of the first gas injector, as well as by means of a distributor provided above and away from the draw tube; (3) the reaction material is fed into the reactor at a rate such that I / L is 1/4 - 1/3, L representing <Desc / Clms Page number 55> the distance from the inlet of the first injector for supplying molecular oxygen or a gas containing molecular oxygen into the reaction liquid at the surface level of the reaction liquid in reactor 1, / representing the distance between the feed inlet of material for charging the starting mixture comprising p-dialkoylbenzene or its intermediate oxidation product, the aliphatic monocarboxylic acid of 2 to 4 carbon atoms and the oxidation catalyst of a heavy metal, in the reactor, and the level of reaction liquid therein; (4) a temperature control system, attached to the reactor, is operated to heat and / or cool the reaction liquid, in order to regulate the temperature of the reaction mixture in the reactor to a predetermined level between 80 and 1500C and (5) the pressure prevailing inside the reactor is adjusted to be situated between atmospheric pressure and 100 atmospheres. 6. Process according to claim 5, characterized in that a part of the molecular oxygen or of the gas containing molecular oxygen is supplied to the reaction liquid contained in the reactor, through the lower part of the reactor body. , while the other part of the molecular oxygen or gas containing molecular oxygen is brought into the reaction liquid from a second gas injector with many perforations and located above and away from the draw-off tube, also serving as a distributor, so as to disperse the molecular oxygen or the gas containing molecular oxygen in the reaction liquid, 7. Process according to Claim 5, characterized in that acetic acid is used as solvent. <Desc / Clms Page number 56> and, as a catalyst for the oxidation of a heavy metal, a cobalt compound soluble in acetic acid. 8. A method according to claims 5 to 7, characterized in that the amount of molecular oxygen or gas containing molecular oxygen to be charged into the reactor is set between 0.8 and 20 cm3 / cm2.sec. , preferably between 0.9 - 10 cm3 / cm2.sec., these values being expressed by the superficial speed of the gas in the reaction liquid contained in the reactor,