Method for the production of terephthalic acid and installation for its implementation

 

(57) Abstract:

Oxidation of p-xylene for the production of terephthalic acid is performed with the use of pure or nearly pure oxygen and evaporative cooling. When using the desirable working conditions reduced the generation of side projects and waste, increasing recycling of oxygen and eliminates the necessity of application in the reactor heat exchange surfaces in direct contact. Disclosed is also a plant for the production of terephthalic acid, which contains mechanical cooling means indirect contact, impellere means for maintaining in the reactor recirculating fluid flow; injection box for oxygen injection box, outlet means for removing gas phase and pipeline tool for extracting terephthalic acid. 2 C. and 18 h.p. f-crystals, 4 Il.

The invention relates to a method for the production of terephthalic acid and installation for its implementation.

In the usual method of obtaining terephthalic acid, based on the use of air or enriched air in the reactor with stirrer serves liquid p-xylene together with monobasic aliphatic into is usually from 1 to 10 weight. including solvent on the volume of the reagent (1:1 to 10:1).

The reaction catalyze a heavy metal or a mixture of heavy metals, mainly cobalt and manganese, in the form of acetate salts. In addition, as the initiator typically use bromine in the form banowati acid.

The reactor is supported at the operating temperature between 170 and 225oC. the Working pressure is usually between 7 and 21 kg/cm2(100 and 300 lb-ft2). In the lower part of the reactor bubbled compressed or enriched air, usually with oxygen content between 21 and 28%. Oxygen from air is dissolved in the liquid phase and interacts with p-xylene to obtain the desired product of terephthalic acid.

Thus also the formation of intermediate oxidation products and by-products of oxidation in amounts depending on the reaction conditions. When the residence time of the material in the installation equal to 1 h, the degree of conversion of p-xylene is typically around 99%, the yield of the desired terephthalic product is more than 96%.

The most important intermediate product of oxidation for the production of terephthalic acid (TPA) is a 4-carboxybenzene (4-CBA), to the camping junk. He acts as an agent breaking the circuit at the subsequent polymerization reactions, which convert TRA in its most important end products, i.e., polyester fibers and polyethylene terephthalate resin. Observed that, for a given residence time, the degree of conversion of 4-CBA TPA increases with temperature. Therefore, with increasing operating temperature, the concentration of 4-CBA TPA decreases, and thus, the quality of TRA at elevated temperatures is improved.

On the other hand, with increasing temperature also increases the loss of raw materials with undesirable side products.

The acidic proton of the solvent and p-xylene to a lesser extent interact to obtain carbon dioxide, carbon monoxide, methyl bromide and methyl acetate, all of which are substances that are sensitive to the environment. So as to obtain terephthalic acid, which would be consistent with applicable quality standards, it is necessary to maintain a high reaction temperature, loss of acetic acid and, accordingly, the receiving side of gases is usually a significant factor from the point of view of the economic process as a whole.

In such known processes podalonia, which is somewhat above the operating pressure of the reactor. Air bubbles dispersed in the reactor and circulated through the mass of liquid reagent and solvent, using a mixing device. When oxygen is dissolved and interacts with p-xylene, the concentration of oxygen in the air bubbles is reduced.

Residual air bubbles are released from the liquid phase and is collected in the gas space in the upper part of the reactor, forming a homogeneous gas phase. This exhaust gas should be removed to provide space for fresh air, it is necessary to maintain the delay of supply of adequate quantity of gas in the reactor to facilitate desirable to transfer oxygen from the air into the liquid phase.

To avoid the possibility of fire or explosion, the oxygen concentration in the gas space in the upper part of the reactor should be maintained below the Flammability limit. For practical working purposes, the oxygen concentration should be maintained less than 8% to 9% by volume. More typically, the concentration of oxygen in the gas space of the support below 5% by volume to provide a security boundary below the limit volplane the bubbles should be below 5% to ensure that to the average oxygen concentration in the gas which is collected in the upper space of the reactor was nonflammable.

The oxygen concentration in the gas space is a function of the speed at which the reactor serves the air or enriched air, and the flow rate of oxygen from air by reaction with p-xylene. The reaction rate and hence the rate of production of TPA per unit volume of the reactor increases with temperature, pressure, oxygen concentration in the gas phase, the concentration of p-xylene concentration of the promoter and the concentration of the catalyst. As the concentration of dissolved oxygen in the liquid phase, and, consequently, the rate of interaction of oxygen is proportional to the concentration of oxygen in the gas phase, for a given number of reaction conditions, the limiting oxygen concentration in the upper space of the reactor 5% effectively limits the rate of interaction of oxygen.

It is obvious that the air or referred enriched air, usually containing from 21% to 28% oxygen, and installation design to obtain TRA require optimization of temperature, pressure, dosage of catalyst, the feed rate of air, the reaction volume and Obradovic per unit of reaction volume and improves the purity of the product, but it also leads to loss of output and the solvent and the formation of by-products due to the pereokislenie.

Recently as oxidant in the production process TRA suggests the use of oxygen or nearly pure oxygen. This method of production TRA, based on the oxygen, usually carried out in a standard reaction vessel using cooling devices direct contact, such as cooling coils to remove heat of reaction from the vessel and maintain the desired operating temperature. Such receiving TRA, based on the use of oxygen carried out in a reactor adapted to mitigate the potential for fire or explosion, should be performed at operating conditions that serve to minimize the amount of undesirable by-products present in the terephthalic acid and the amount of exhaust gases which are treated as part of the whole production process.

In commercial practice, other desirable processes for the production of terephthalic acid, based on the use of oxygen, as in traditional production processes TRA, based on the use of air disadvantageous OYA solid product. In the reaction mixture presidets TRA and the solid reaction product TRA easily condense on any cold surface. In the cooling coils typically used for direct cooling of the reactor to the desired operating temperature, quickly covered solid TRA and lose much of the ability to heat transfer. This leads to a premature stop of the production process TRA, which significantly increases the cost of the entire process associated with the production of terephthalic acid.

As the production of TPA is highly significant commercial process, in this area there is a genuine need for improved method and device for producing TPA. In particular, the loss of a significant amount of time in the production of TRA due to the above problems with heat transfer must be overcome in order to increase the overall efficiency of the method and installation for obtaining TRA. As the production processes TRA, based on the use of oxygen, are particularly desirable, such improvement in this area requires appropriate processes applicable for the production of TPA, based on the use of kidstv TRA, based on the application of the air.

Therefore, the aim of the invention is the provision of an improved method and plant for producing terephthalic acid.

Another objective of the invention is the provision of an improved method for the production of TPA, based on the use of oxygen, and installation.

Another objective of the invention is the provision of a method and installation for the production of TPA, eliminating the need for a premature stop the process due to the loss of the ability to heat transfer and cooling efficiency in the deposition of TRA.

Having in mind these and other objectives, the invention will be further described in more detail, with its new features separately shown in the attached claims.

The oxidation reaction to obtain terephthalic acid was carried out using instead of air oxygen, the method of gas-liquid mixing and installation, increasing oxygen consumption and providing evaporative cooling to remove the heat of reaction, which eliminates the need to use in the reactor coolant direct contact.

In Fig. 1 presents Tory in the way of evaporative cooling of the invention; in Fig. 2 is a graph of concentration of the intermediate product 4-CBA in the solid and suspension products of the oxidation of p-xylene pure oxygen as a function of temperature in the method of evaporative cooling of the invention; Fig. 3 is a schematic side view of a reactor in which the oxidation of p-xylene with oxygen, representing the desired variant of the invention; Fig. 4 is a schematic side view of the conventional design of the reactor, which can be used in the processes of evaporative cooling of the invention to use instead of air of oxygen for oxidation of p-xylene.

Objectives of the invention are achieved through the production of desirable terephthalic acid when used instead of air oxygen in a way that enables the use of evaporative cooling, especially when the beneficial uses of a modified, highly desirable way in which to apply the reactor liquid oxidation (LOR) and install. Although TRA receive in the solid phase, the invention allows to avoid in practice working problems associated with the conventional use of the heat transfer surfaces of cooling to remove the heat of the oxidation reaction, zmeegolov etc.

Thus, the safe and effective use of pure or nearly pure oxygen for the oxidation of p-xylene can suitably be carried out with the use of evaporative cooling to remove the heat of reaction generated during the oxidation reaction.

The process LOR and system that use in the practice of the invention, provide an opportunity to apply instead of air oxygen at the desired operating conditions that serve to minimize the amount of undesirable by-products present in the terephthalic acid, and the elimination of potential fire or explosion.

In addition, minimize the amount of exhaust gases being processed.

Moreover, the invention can be performed at low temperatures and/or pressures than those usually used in the traditional methods based on the use of air, when it reaches the receipt of an equivalent amount of TRA. Adverse reactions that consumed the solvent and the reagent and which receive product gases are suppressed in moderate operating temperature conditions normally used in the practice of the invention.

In sposobiacych without noticeable loss of oxygen in the upper gas phase.

In practice, in the embodiment of the invention shown in Fig. 3, oxygen is substantially consumed during the first passage through a combination of helical impeller with downward pressure/exhaust pipe located within the reactor, and "reach out" cells referenced below. As a result of their use and the modified configuration setup used in desirable embodiments of the invention, recycling of oxygen and other gas bubbles through an exhaust pipe to minimize. One of the important advantages of the approach to a modified system LOR is that because the gas-liquid reaction mixture is pumped from the exhaust pipe located near the bottom of the reactor, with high speeds, consequently, forms a jet which entrains the surrounding fluid on the outer surface of the exhaust pipe and collides with the bottom part of the reaction vessel, whereby in the reactor mixture in the bottom of the reactor are provided "stretching" of the cell.

This "stretching" of the cell essentially capture the dispersed gas phase up until it is completely used up or cholesterol in the critical bubble diameter, with up to which hidcote gives a very high efficiency of oxygen use even with just one pass through the impeller, located in the chimney.

The process conditions for the oxidation of organic compounds in the modified system LOR the invention are typically in the range used in the commercial practice of the methods of oxidation, based on the use of air.

The main significant difference is that for a given reaction mixture and the operating temperature operating pressure of the reactor will be lower in the method based on the use of oxygen, compared with the method based on the use of air.

It should be noted that the optimal process conditions, such as operating temperature and concentration of catalyst, can be different for the oxidation of p-xylene based on the use of oxygen for the oxidation of p-xylene based on the use of air. The efficiency of the method based on the use of air is determined by the relative benefit from the influence of high temperature on the reaction rate and degree of conversion compared to the increased loss of product selectivity and yield with increasing working temperature conditions. This loss of selectivity with increasing loss of solvent and/or reagent is for scout to have a similar effect on the reaction rate, as well as selectivity. It was found that the method based on the use of evaporative cooling, which is practiced in accordance with the invention, the degree of reaction product and the reaction rate increases with increasing operating temperature, but losses of solvent from the reaction temperature was not observed.

When referring to Fig. 1 the behavior of acetic acid used as solvent, it is illustrated as a function of temperature and refers to the oxidation of p-xylene to terephthalic acid in the method of the invention using evaporative cooling. Specialists in this field it is clear that the interaction of acetic acid, which solvent is undesirable, and it was found that it is negligible at normal reaction temperatures in the range from 180 to 200oC.

These data were taken in the reactor LOR capacity of 3.3 liters, modified in accordance with the invention.

The inner diameter of the reactor amounted to 12.7 cm (5 inches), and both impeller with a diameter of 5.08 cm (2 inches) and 7.62 cm (3 inches) were located inside the exhaust pipe and used them when the rotation speed of 1000 rpm, the aforementioned exhaust pipe rasaleela. Used catalysts the reactions were cobalt and manganese in the form of acetate salts, which are used in appropriate concentrations from 200 to 2000 hours/million and from 500 to 3000 hours/million Bromine in the form of hydrogen bromide was used as an indicator when the concentration in the feed mixture in the range from 400 to 3000 hours/million

Fig. 2 represents the concentration of 4-CBA in the solid and suspension products of the oxidation of p-xylene pure oxygen as a function of temperature in the method of the invention using evaporative cooling. You can see that both in suspension and in the solid product, undesirable concentration of 4-CBA is reduced when the temperature rises to the desired temperature conditions of the invention.

Therefore, for a method of obtaining TRA, based on the use of oxygen and evaporative cooling, the quality of the product increases with temperature, but it was found that the loss of solvent are insensitive to temperature rise in a desirable range used in the practice of the invention.

Fig. 3 represents a modified system LOR suitable for use in accordance with the invention for the oxidation of p-xylene clean air Jordan 1 has mass organic fluid 2 from the surface of the section of gas-liquid 3 and the upper gas phase 4, located in the upper part of the reactor. Production fluid return from the reactor 1 through line 5. And LOR, in the reactor in the center is hollow exhaust pipe 6 with the open end 7 at the top and open end 8 in its lower part. In the hollow exhaust pipe 6 located impeller means 9. Such impeller means 9 are screw impeller means with a downward pressure, adapted to facilitate the downward flow of the liquid stream at high speed from the said mass of liquid 2 into a hollow exhaust pipe 6, education turbulent "stretching" of the cell B and the upward flow of said liquid therefrom into the gap between the side wall of the reaction vessel and the outer surface of the hollow exhaust pipe 6 above referred to "reach out" cells B. Impeller means 9 typically includes impeller means 10 for radial flow and optionally the lower reflective walls 11 to facilitate the desired recirculation of fluid flow in the reactor 1. The corresponding drive shaft 12, which is directed upward from the reactor 1, is intended for connection to respective drive means 13 used for impeller means 9.

Fig. - Christ.automatic extending portion at its upper end to facilitate the flow of flow of the mixture bubbles of gas-liquid into the chamber of the suction for the downward passage of it.

In modelirovanie system LOR the invention conically evaporating part of these located on the upper end of the hollow exhaust pipe 6, but the configuration mentioned conically widening part is completely different from the conically widening part of the said patent, and it is used for the opposite purpose, consisting in reducing the number of gas bubbles involved down in a hollow exhaust pipe 6.

Thus, a vertically elongated conically widening portion 6A of the hollow exhaust pipe 6 extends up above her, usually cylindrical, the lower part 6b, which are the impeller means 9. The increase in diameter in the top mentioned conically widening part 6a serves to minimize liquid flow A through the top of the hollow exhaust pipe 6, through which noticeably decreases the portion of the gas bubbles rising in the reactor beyond the mentioned hollow exhaust pipe 6, which are fond of down in the impeller means 9 with a downward flow of the reacting liquid in the hollow exhaust pipe 6. For this purpose a vertically elongated conically expanding the upper portion 6a extends in the vertical direction by a distance of from 0 to 200%, STW 9 and which is generally cylindrical, instead of a conical shape. The diameter at the top of the exhaust pipe, i.e., larger diameter at the top of the upper part 6a, appropriately defined to minimize the downward velocity of the fluid through the top of the exhaust pipe, for example, in certain embodiments from 45,72 cm/s (1.5 ft/s). It is clear that despite the fact that the sizes of the upper part 6a of the exhaust pipe 6 is changed depending on all conditions of the invention, generally between the upper part 6a and the walls of the reaction vessel there is a gap of from 0.5 to 4.0 times the diameter of the exhaust pipe. In some cases, the enlarged diameter of the upper part 6a will be from 1.5 to 3.0 times the diameter of the hollow portion 6b. In some embodiments, the enlarged diameter at the top of the upper part 6a will be from 40 to 80% of the internal diameter or width of the reactor 1, preferably from 50 to 60%. For special use factors determining the size of the exhaust pipe 6 and the upper part 6a are the geometry and the speed of rotation of the impeller means. High speed fluid pumped down through the impeller means will typically be in the range from 1.5 (5) 1.8 (6) 2.4 m/s (8 ft/s) or higher, for example, to create a high-turbulence "put the key expanding part 6a of the hollow exhaust pipe 6 to facilitate the downward flow of liquid to the impeller means 9 also optionally include a reflective walls 6'.

The result of the rapid flow of incoming oxygen at injectioni in the hollow exhaust pipe 6 and to minimize the downward flow of liquid through the top of the exhaust pipe, the combination of the invention a modified impeller LOR/chimney effectively reduces the amount of recirculating gas flowing downward in the exhaust pipe. Bubbles of gas passing upwards into the liquid flow type B in the reactor outside in the lower part 6b of the hollow pipe, mainly contain volatile organic chemicals (VOC's), reactive solvent, water vapor and by-products such as CO and CO2while there are very minor amounts of dissolved oxygen. Evaporation of volatile organic varieties provides evaporative cooling required to remove the heat of reaction desired organic chemical process of oxidation. You can see that the gas bubbles rising in the reactor 1, in particular near the top of the upper part 6a of the hollow exhaust pipe 6 and in the area above the exhaust pipe to the surface of the section of gas-liquid 3, contain very little, i.e. essentially not contain oxygen so that the oxygen concentration in the upper gas phase 4 was Hildren 2 near the top of the upper part 6a of the hollow exhaust pipe 6 and the fluid mass 2 above the upper part 6a is thus, in essence, a relatively fixed area less turbulence, similar to that provided in the method and system LOR patent Litz et al.

It is clear that during the oxidation of the gases removed from the top of the gas phase 4 through the removal of gases 14. It should be noted that for the purposes of the invention the lower pressurewise part 6b of the hollow exhaust pipe 6 preferably positioned in the lower part of the reactor 1, as shown in Fig. 3, preferably near the lower part of the above-mentioned reactor in order to provide a collision between a mixture of gas bubbles, the liquid discharged from the bottom of the reaction vessel 1, and the bottom of the reaction vessel.

When promoting completely different types of gas flow is desirable in the practice of the invention, in contrast to the process gas-liquid mixing, described in the patent Litz et al., reflective partitions corresponding guiding reflective walls 34 used in the system Litz for directing a mixture of gas bubbles-liquid to the top of the hollow chamber of the suction 29, not used in the practice of the invention.

In the invention, however, use the small horizontal reflective partitions, i.e., the disk 15, raspolojennye partitions are used to prevent absorption of gas by vortex effects from the top of the gas phase along the drive shaft 12.

As mentioned above, for oxidation of p-xylene in the invention use a pure or nearly pure oxygen, thus to remove the heat of reaction generated by the oxidation reaction, used evaporative cooling. For this purpose greatly enhance the mass transfer of oxygen from the gas phase into the liquid phase in order to increase the overall reaction rate in comparison with the oxidation reactions based on the use of air. The practice of the invention enables high speed flow of oxygen in order to obtain a very high efficiency of oxygen use, i.e., at least 75% and preferably 90% or higher on first injectioni pure or nearly pure oxygen directly into a hollow exhaust pipe 6, which has been here described. Such use of pure oxygen in combination with the configuration of the hollow exhaust pipe 6, which is described above, minimizes recirculation of gas bubbles through the exhaust pipe 6, allows advantageous use of evaporative cooling and prevents cavitation in the impeller means 9, which prevents or interferes with the desired recirculation of liquid reagent and tear and quickly the th cooling in the invention in the reactor 1 add pure or nearly pure oxygen, it is preferable in the point of high turbulence within the hollow exhaust pipe 6, than anywhere else in the weight of the organic liquid 2. Despite the fact that the addition of oxygen can be accomplished in any suitable point of high turbulence in the hollow exhaust pipe 6 or below it, for example through line injection box 16 straight in its lower part 6b directly above the impeller means 9, it is desirable and convenient to inject oxygen into the system through line injection 17 to a point in the lower part 6b below the helical impeller means 9, and, if used, lower impeller means 10 for radial flow, for example postoloprty turbine, or a point in the lower part 6b between the helical impeller means 9, and, if used, impeller means 10 for radial flow.

It is clear that these points of high turbulence and injection of incoming oxygen in such a point of high turbulence are important for the desired rapid consumption of oxygen. High initial oxygen concentration in the gas phase at the point of injection is used to increase the rate of mass transfer of oxygen in this area of the liquid reagent, which otherwise will obednitsa oxygen in Fig. 3, it can be understood that the nitrogen or other inert purge gas can flow in the upper gas phase 4, mainly through the line 18 to inert small quantities of unreacted oxygen that can be produced in the upper gas phase. In this regard it should be noted that the configuration of the exhaust pipe is a good pump, which provides the above-mentioned "reach out" cells, which trap undissolved oxygen, which achieves the high efficiency of oxygen and limits the amount of nitrogen or other inert gas for purging required in the upper gas phase, compared to the variant shown in Fig. 4, which will be disclosed below. "Reach out" cells form a very significant part of the region of turbulent flow through the impeller means.

In the production process TRA from the reaction mixture to evaporate a significant amount of organic material and water. The exhaust gases are preferably cooled in preferred embodiments of the invention the condensate return to the reactor. Part of the waste stream optionally is removed for gas analysis of carbon dioxide and oxygen. Efficiency to the

That is less than 1% of the oxygen fed to the reactor, remove the unreacted form.

The corresponding benefit through the use of oxygen in accordance with the practice of the invention instead of the air in the traditional manufacturing methods TRA is observed in the range of suitable operating conditions, and optimal working conditions for the method of the invention based on the use of oxygen, are usually more favorable than the conditions that are suitable for the practice of traditional method based on the use of air. The ratio of solvent : reagent is in the practice of the invention from 1 : 1 to 8 : 1 by weight/volume.

The catalyst for the desired oxidation reaction is a mixture of cobalt and manganese, preferably as the acetate salts. The dosage of the catalyst is between 500 and 3000 hours/million, while the ratio of cobalt to manganese is from 0.1 to 10 : 1, preferably about 3 : 1 by weight. As the initiator of the use of bromine, which is suitably added in the form of hydrogen bromide (HBr). Dosage of bromine is between 0.1 : 1 and 1 : 1 by weight relative to the total dosage of catalyst, preferably about 0.3 : 1. The residence time of the liquid in the reactor soybeans between 7 (100) and 13.9 kg/cm2(200 pounds/inch2).

It should be noted that the optimum operating conditions for a particular variant of the invention is largely determined by the efficiency suitable for this option. As mentioned above, the increase of the working temperature leads to loss of solvent and improves the quality of the product. This temperature effect on these two parameters can be seen from the data shown in Fig. 1 and 2. Fig. 1 shows the effect of operating temperature on the combustion of acetic acid. Fig. 2 shows the effect of operating temperature on the concentration of 4-CBA in the product. As noted above, when the level of 4-CBA increases, the quality of the product deteriorates. Based on the data shown in Fig. 1 and 2, the preferred operating temperature for the practice of the invention is approximately 180oC, with the preferred operating pressure is between 9 (130) and 10.4 kg/cm2(150 pounds/inch2). Thus, in the practice of the invention can be used milder operating conditions than those typically used in the practice of the traditional method of production of terephthalic acid, based on the use of air.

In practice, the explanatory var for the main components of the oxidation reaction were such as indicated below, however, the threads provided on the fluid in the number of 45.4 kg/min (100 lb/min). The source liquid is introduced into the reactor, contains the remaining 9.08 kg (20 lb) p-xylene, 31.8 kg (70) acetic acid, 4.5 kg (10) water, 0.01 kg (0,22) acetate cobalt, 0.036 kg (0,08) of manganese acetate and 0,009 kg (0,02) Hydrobromic acid. The oxygen supply in the amount of 8.4 kg (18.5 lb) provides a flow of liquid product containing 31,33 kg (69) acetic acid, 13,8 kg (30,5) of terephthalic acid, 7,95 kg (17,5) water, 0.01 kg (0,22) acetate cobalt, 0.036 kg (0,08) of manganese acetate, 0,009 kg (0,02) Hydrobromic acid and 0.036 kg (0,08) xylene. For a product used 0,908 kg (2 lb) of nitrogen, while the exhaust gas contained 0,908 kg (2) nitrogen 0,55 kg (1,2) carbon dioxide, 0,272 kg (0,60) carbon monoxide and 0.1 kg (0,23) oxygen. It is reported that the unsolicited receipt of acetate in the traditional mode of production TRA, based on the use of air, corresponding to approximately 0.18 to/to 45.4 kg (0,4/100 pounds) received TPA. In the method based on the use of oxygen, which is represented in the description and the claims, the amount of acetate can be very significantly reduced, while the test data indicate that the number p is the shadow.

The amount of carbon monoxide and carbon dioxide may also be reduced in the practice of the invention to a value of approximately of the order. In the practice of the invention can also expect a similar decrease the amount of junk that is sensitive to the environment, a by-product of methyl bromide.

It should be noted that in less preferred embodiments, the substitution of oxygen for air in the oxidation of organic chemicals such as hydrocarbons, can be implemented in conventional reaction vessels, for example, to remove the exothermic heat of oxidation reaction by means of evaporative cooling. In Fig. 4 reactor 20 containing a mass of liquid reagent 21, together with the surface section of gas-liquid 22 and the upper gas phase 23, contains oxygen, is injected down the line 24. Tools mixing 25 driven drive shaft 26 and the motor transmission 27 is used for dispersion of oxygen in the form of bubbles 28 in the body of liquid reagent 21. Nitrogen and other inert venting gas is introduced into the upper gas phase 23 through line 29, and the ventilating gas is removed therefrom through line 30.

If the reaction OKISLENIYa removed from the reaction mixture by means of evaporative cooling. When such conditions are realized many of the benefits observed when processing based on the use of oxygen, i.e., increased reaction rate, reducing the waste stream, reduced formation of by-products. Although the flow types are different in such systems, which are shown in Fig. 4, however, no oxygen is captured in the "stretching" of the cell, such that advantageously formed in option LOR Fig. 3, and a large part of undissolved oxygen escapes into the upper gas phase. Consequently, the installation of Fig. 4 is less effective than option Fig. 3, and requires a larger amount of nitrogen or other inert gas for safety purposes.

Thus, to avoid problems associated with hazardous concentrations of oxygen in the upper gas phase 23 in such processes in the reactor, the upper gas phase 23 should skip a large amount of nitrogen or other inert gas venting to avoid problems associated with the presence of excess oxygen in the gas phase.

The additional cost of nitrogen or other gas may render this option uneconomical, from a practical point of view.

Many of the new Fig. 3, will be implemented in practice less preferred variant of Fig. 4, i.e., quicker response times, reduced waste stream, reduced formation of by-products. In addition to the large flow of nitrogen or other inert gas in the upper part of the gas space, the efficiency of oxygen use in the embodiment of Fig. 4 is much lower than for variants of the invention of Fig. 3, or variants of the patent Litz, because there is no ensure recirculation of unreacted oxygen, i.e., "pulling" cell variant of Fig. 3.

Thus, you need more oxygen, because a large part of the oxygen entering the reactor will be removed in unreacted form. Additional quantities of oxygen and nitrogen in the variant of Fig. 4, and associated costs make this option less desirable and, of course, uneconomical for various commercial applications in the production process, TRA.

Specialists in this field understand that in parts of the invention can be made various changes and modifications without deviating from the scope of the claims which are set forth in the attached claims. For example, there may be used the four carbon atoms. Although in the preferred embodiments of the invention it is advantageous to use essentially pure oxygen, in various embodiments of the invention can also be used other, almost pure, oxygen-enriched gases with much higher oxygen content than air, i.e., in the various embodiments of the invention may be used air, oxygen-enriched, having at least about 50%, preferably at least about 90%, and essentially 100% oxygen.

As can be seen from the explanatory options, pure oxygen or a gas enriched with oxygen, Inuktitut directly in the recirculated portion of the fluid mass at the point of injection box oxygen or points near the impeller means. For the purposes of this invention, the position next to the impeller means is one of the provisions in the field of turbulent flow through impeller means including an impeller sucking and production fields of flow rates. Field of turbulent flow also largely involves "stretching" of the cell, i.e., "pulling" of the cell B in Fig. 3, formed in the reaction vessel below the hollow exhaust pipe and impeller means.

From the consequently modify for use without cavitation, that allows the desired method of mixing gas and liquid and the setting in which use evaporative cooling.

The practice of the invention makes it possible not only to effectively distribute the process LOR and system for oxidation of p-xylene in solid product TRA, the use of pure or nearly pure oxygen in the practice of the invention enables to apply the reaction conditions, for example, to reduce the formation of unwanted by-products, reducing consumption of solvent and the amount of gas flowing in the reaction system, and generating the exhaust gas. A feature of the invention, consisting in the use of evaporative cooling, offers a significant and unexpected benefits at a significantly reduced flow rate of liquid reagent and solvent. By reducing the generation of by-product and waste while increasing the use of oxygen and providing a milder operating conditions, the invention provides a very desirable technical, economic benefits and benefits to the environment over conventional production methods TRA.

1. The method of obtaining terephthalic acid by liquid-phase oxidation of p-xylene in hoevenii to a temperature of 150 200oC and a pressure of 7 to 13.9 kg/cm2within 30 - 90 min, at present in the reactor section two phases: the upper gas phase and a lower liquid phase and removing from the top of the gas phase bubbles of evaporated organic material, water vapor and oxidizing gas without significant loss of oxygen when used in the recycling process reagents, wherein the process is carried out in a reactor equipped with impeller means, as the oxidizing gas using pure oxygen or a gas enriched with oxygen, and maintain a recirculation of the reaction mass by creating due to the impeller means of recirculating flow, which is directly Inuktitut oxidizing gas, while it Inuktitut at the point or points of injection box, located near the impeller means, created inside their field high turbulence turbulent flow of rapidly dispersing gas into a liquid in the form of small bubbles and rapid absorption of at least about 90% oxygen, the heat of reaction released during the oxidation of p-xylene is removed by evaporative cooling by evaporation of volatile compounds - organic material, water vapor and containing the, essentially aturbulent the liquid phase in the upper part of the reactor to the surface section of the gas and liquid phases in the upper gas phase, while the terephthalic acid is extracted from the reactor.

2. The method according to p. 1, characterized in that through the upper gas phase that receives small amounts of oxygen, miss inert gas.

3. The method according to p. 2, characterized in that the recirculated flow of the reaction mass supported by the impeller means located in the reactor, and input to a downstream discharge axial flow, with impeller means are upward drive shaft located therein a reflective walls to prevent absorption of gas from the upper gas phase along the drive shaft, and fluid flowing down through the impeller means of the downward discharge, has the speed to create a high-turbulence "reach out" cells, which trap undissolved oxygen and increase its dissolution.

4. The method according to p. 3, characterized in that the impeller means for the downward discharge axial flow located in the bottom portion located in the center of the hollow exhaust pipe, inviting pipe and upward from its outer side, when this hollow exhaust pipe has an enlarged conically expanding the upper portion extending upward in the vertical direction is not more than about 200% of the length of its lower part and the upper part has an enlarged upper diameter decreasing downward flow velocity of the liquid flowing through the top of the hollow exhaust pipe.

5. The method according to p. 4, characterized in that the oxygen injection box is a hollow exhaust pipe below the impeller means for the downward discharge axial flow.

6. The method according to p. 5, characterized in that the impeller means for radial flow are located in the hollow exhaust pipe below the impeller means for the downward discharge axial flow, at this point injection box oxygen is located between the impeller means for the downward discharge axial flow impeller and means for radial flow.

7. The method according to p. 5, characterized in that the impeller means for radial flow are located in the hollow exhaust pipe below the impeller means for the downward discharge at this point injection box oxygen is lower impeller means for radial flow.

9. The method according to p. 2, characterized in that the mass of liquid maintained at the boiling point of the reaction mixture without an excess of gaseous oxygen present in it.

10. The method according to p. 4, characterized in that the enlarged conical widening of the upper part of a hollow exhaust pipe extends up to a distance of approximately 100 - 150% of the length of its bottom.

11. The method according to p. 1, characterized in that the solvent comprises acetic acid, the ratio of solvent to the reagent p-xylene is about 1 : 1 to 8 : 1 weight of the solvent to the volume of the reagent.

12. The method according to p. 11, characterized in that the catalyst comprises a mixture of cobalt and manganese salts, taken in amounts of 500 to 3000 hours 1 million relative to the volume of the liquid reaction mixture, and the mass ratio of cobalt catalyst to the manganese catalyst is from 0.1 : 1.0 to 10 : 1 by weight.

13. Installation for the production of terephthalic acid by oxidation of p-xylene present in the mass of liquid without appreciable loss of oxygen in the upper gas phase containing the reactor to contain the fluid mass containing p-xylene, organic solvent, catalyst and initiator-bromo, n is a mechanical cooling means indirect contact; impeller means for maintaining in the reactor recirculating fluid flow; injection box for injection box of pure oxygen or gas rich in oxygen, directly into the mass of liquid outlet means for removing bubbles - evaporated organic material and water vapor from the top of the gas phase and pipeline tool for extracting terephthalic acid from the reactor, characterized in that it further comprises means of injection box for injection box of pure oxygen or gas rich in oxygen, directly into the liquid mass, as when injectioni pure oxygen or a gas enriched with oxygen at the point or points of injection box about the aforementioned impeller means within the field of turbulent flow, made these impeller means so quickly dispersing the oxygen in the liquid in the form of small bubbles for quick consumption when injectioni in the liquid, the heat of reaction due to the oxidation of organic chemicals is removed by evaporative cooling by evaporation of volatile organic material and water present in the mass of the liquid, the bubbles evaporated Otsa up to the specified weight of liquid through the relatively stationary essentially aturbulent zone in the upper part of the reactor to the surface and section of gas - liquid and at the top of the gas phase; the pipeline to extract terephthalic acid from the reactor, through which oxygen and oxidized organic chemicals can be mixed under conditions conducive to the rapid consumption of oxygen and the evaporation of organic material and water, containing only a small number of bubbles of oxygen flowing into the upper gas phase.

14. Installation according to p. 13, characterized in that it contains a pipeline for passing inert gas through the upper gas phase.

15. Installation according to p. 13, characterized in that it further comprises impeller means for the downward discharge axial flow, located in the reaction vessel, and upward drive shaft located therein a reflective walls to prevent the ingress of gas from the upper gas phase along the drive shaft in the fluid flowing in the impeller means.

16. Installation according to p. 15, characterized in that it includes located essentially in the center of the hollow exhaust pipe, which contains the impeller means for nicholassta with the to recirculating stream was sent down in the hollow exhaust pipe and upward from its outer side, with a hollow exhaust pipe has an enlarged conically expanding the upper portion extending upward in the vertical direction is not more than about 200% of the length from its lower part and the upper part has an enlarged upper diameter, reducing the downward velocity of the liquid flowing through the top of the hollow exhaust pipe.

17. Installation according to p. 16, characterized in that the point of injection box oxygen is lower impeller means for the downward discharge axial flow.

18. Installation under item 17, characterized in that the impeller for radial flow is below the impeller means for the downward discharge axial flow, at this point injection box oxygen is located between the impeller means for the downward discharge axial flow impeller and means for radial flow.

19. Installation under item 17, characterized in that it includes impeller means for radial flow, located in the hollow exhaust pipe below the impeller means for the downward discharge at this point injection box oxygen na increased, conically widening the upper part of the hollow exhaust pipe extends up to a distance of 100 to 150% of the length of its bottom.

 

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