TW557293B - Method for increasing oxidation reactor production capacity - Google Patents

Abstract

The present invention relates to a method for increasing the production capacity of a conventional oxidation reactor for catalytic liquid phase oxidation of paraxylene by staging the oxidation reaction into a first high pressure and high solvent ratio reaction zone followed by the conventional reactor.

Description

557293

U.S. Patent Application No. 09 / 481,811 related to patentees was filed in January, Shantou, and the application was called 'U.S. Patent Application No. 09 / 757,455, issued on January 2001. Shen Ye, U.S. Patent Application No. 09 / 757,458 filed an application on January 10, 2010, and the foregoing are currently under trial. 1Background, the present invention relates to a method for increasing the manufacturing capacity of a commercial oxidation reactor. More specifically, the present invention is a method to eliminate the bottleneck of the type of commercial reactor system used for the production of p-w-formic acid (catalytic liquid-phase oxidation reaction) for the production of H-benzene. Almost all terephthalic acid is commercially available. Scale-made from p-xylene catalytic degradation and air oxidation reactions. Commercial methods use acetic acid as a solvent and-or multiple polyvalent heavy metals as catalysts. Lead and M are the most commonly used heavy metal catalysts, and bromine is used as the catalyst. Renewable source of free radicals. Vinegar I, Lithium (Molecular Oxygen), p-xylene, and catalyst are fed continuously to maintain A 175C, 225 C, 1000-30kPa (ie, 10%). -3 atmospheres) reverse mixing oxidation reactor. The feed acetic acid: p-xylene ratio is substantially lower than 5: i. The amount of more gas added to the reactor is lower than the complete conversion of p-xylene to p-xylene. Benzene methyl sulfide is used to minimize the formation of unwanted by-products (such as colored formations). This oxidation reaction is an exothermic reaction that evaporates the acetic acid solvent to remove heat from the reactor. Related steam Condensation and most of the condensate is back to the reactor Some condensate is drained to control the water concentration in the system (per mole of para-xylene which forms terephthalic acid will form two moles of water). This reaction is 30 minutes to 2 hours, depending on the method Vision Oxygen-4- This paper size applies to Chinese National Standard (CNS) A4 specification (210X297 public love) 557293 A7 _ B7 V. Description of the invention (2) Operating conditions of the reactor (such as temperature, catalyst concentration and residence time Depending on the solvent and precursors may be decomposed in large quantities, this will increase the cost of operating this method. The effluent of the emulsification reactor (ie, the reaction product) is a slurry of crude p-benzene-formic acid (TA) crystals in acetic acid. Although there are also p-toluene and p-toluic acid and undesired colored formations, the main impurity of crude TA is 4-carboxybenzaldehyde (4-CBA), which is incompletely oxidized. _Xylene. According to established methods, the crude terephthalic acid crystals are further processed (eg, purified by post-oxidation and / or hydrogenation reactions) and recovered (eg, by filtration, washing, and drying). ^ The method of the present invention The ability of the system, that is, eliminating the "bottleneck" of the reaction system, while providing a reliable and affordable method, increases the production yield of the conventional terephthalic acid method by 100%. According to the present invention, the utilization The first reaction zone (that is, the first reactor) and the subsequent second reaction zone (that is, the existing conventional reactor) enable the oxidation reaction to be effectively carried out in stages to achieve the purpose of eliminating bottlenecks. SUMMARY OF THE INVENTION The present invention is a method for improving the production capacity of a catalytic liquid-phase oxidation reaction for p-xylene I oxidation reactor. The first reaction zone (or the first reactor) is located upstream of a conventional reactor, The sequential steps for completing this method are to feed the reactants including an appropriate solvent (which is acetic acid) to the first reaction zone where the pressure is increased, wherein the solvent ratio (ie, acetic acid: p-xylene mass ratio) and oxygen consumption control After leaving any terephthalic acid formed in solution, the resulting reaction medium is fed to a second (ie, conventional) oxidation reaction zone. This method includes: -5- 557293 A7 ^ _B7 V. Description of the invention (3) (a) Form a feed stream containing acetic acid and an oxidation reaction catalyst at a pressure range of at least about 2,000 kPa up to 20,000 (B) the feed stream is oxidized; (c) the (1) oxygen-containing feed stream and (2) para-xylene are introduced to the first reaction zone continuously and simultaneously to form a reaction medium, wherein the solvent : Mass ratio of p-xylene from 10-20: 1; (d) limiting the oxygen consumption of the reaction medium in the first reaction zone to the complete conversion of p-xylene to p-phthalic acid Less than 50% of the aerobic amount; and 0) introducing the reaction medium to the second reaction zone and simultaneously reducing the pressure of the reaction medium to a range of 1,000 kPa to less than 2,000 kPa. The terephthalic acid obtained from the second reaction zone is basically a slurry of terephthalic acid crystals, which can be further treated and recovered according to any convenient method. From the standpoint of economy and process operability, the preferred acetic acid: p-xylene mass ratio is 13-16: 1. The oxygen consumption in the first reaction zone is limited to 500 / of the amount of oxygen required to completely convert the para-xylene present to terephthalic acid. The following is to prevent a large amount of TA formation and solid precipitation. The oxygen consumption is preferably 30-40% of the amount of oxygen required to completely convert the existing para-xylene into p-phthalic acid. Control oxygen consumption in the first reaction zone by one or more of the following methods: ⑴ maintain the oxygen supply within a predetermined range; (H) maintain the catalyst concentration within a predetermined range; (iii) The residence time in one reaction zone (defined as the reactor liquid volume divided by the reactor feed rate) is limited to less than about 6 minutes, preferably less than 4 minutes; and (iv) optionally removed from the reaction zone Heat to make the -6- This paper size applies the Chinese National Standard (CNS) A4 specification (21〇X 297 mm) 557293

According to a preferred embodiment of the present invention, the first reaction zone is a plug flow reactor. The so-called "plug flow reactor" is defined as an elongated or tubular reaction zone. In the reaction zone, a tube or duct will rapidly and fully mix radially. However, the present invention is not limited to any The flow-shaped reaction zone is similar to the reactor structure. According to the alternative implementation of the present invention μ, the first reactor can be a reverse, a reversed wire, meaning a highly mixed reactor stirrer or bubble tube reactor. All reactions The type of reactor is characterized in that in the first reaction zone according to the present invention, the oxygen supplied to it is essentially pure oxygen. The first reaction zone is further characterized by acetic acid; the mass ratio of p-xylene is quite high, at 10- 20: i range and the pressure is quite high, such as: at least 2,000 kPa up to 20,000 kPa. The operating pressure of the first reactor is selected so that no vapor phase exists in the first reaction zone, that is, The first reaction zone is non-boiling. If necessary, the first reaction zone is cooled to control the temperature of the reaction medium leaving the first reaction zone to less than about 21 ° C. This method is suitable for oxidation reaction catalysts. The system exists to carry out this The system can be homogeneous or heterogeneous. Usually a homogeneous catalyst is used and is selected from one or more heavy metal compounds, such as: Ming, Zhong and / or knot compounds. In addition, the catalyst usually also includes oxidation reaction promoters, such as: Bromine. During the implementation of the method, most of the catalyst metal and the oxidation reaction accelerator remain in the solution. After the product is recovered, the catalyst metal and the oxidation reaction accelerator are recovered and recycled with the new catalyst solution for replenishment. The feed stream of each reaction zone contains typical oxidation reaction catalyst components (such as: Co, Mn, Br), but the catalyst concentration is about 1/5 to 1/3 of the recycled mother liquor recovered from the product. After that, the solvent is evaporated And the output from the tower hall of the second reaction zone-8-This paper size applies to China National Standard (CNS) A4 (210 X 297 mm)

Binding

557293 A7 ___ B7____ 5. Description of the invention (6) When the solvent is removed, the catalyst concentration is increased to a more conventional catalyst concentration. The total catalyst metal concentration in the first reaction zone is basically in the range of 150 to 1,000 ppm (weight / weight), while the catalyst metal concentration in the second reaction zone is basically in the range of 500 to 3,000 ρρπι (Weight / weight) range. When using Co and Mn metal catalyst systems, the total catalyst metal concentration in the first reaction zone should be controlled above about 200 ppm (weight / weight) to obtain satisfactory catalyst selectivity and activity. . However, it is preferred that the total metal concentration in the first reaction zone be higher than about 250 ppm (weight / weight). This emulsification reaction is exothermic. Depending on the solvent ratio and oxygen consumption of the first reactor, the reaction heat will raise the temperature of the first reaction medium to above 2 ° C without using a device to cool the reactor. It is desirable to keep the outlet temperature of the first reactor below 2 10 ° C to minimize acetic acid combustion. Therefore, the first reaction zone may include a cooling coil or some other internal or external device to remove heat from the reactor (and reaction medium) to control the temperature of the reaction medium outlet below 210 ° C. Controlling the temperature, catalyst concentration and residence time of the reaction medium, and maintaining the rate of oxygen supply to the first reaction zone within a predetermined range, allows the operator to control the oxygen consumption in the reaction medium to completely convert para-xylene Less than 50% of the required oxygen amount for τA. It is strictly required to prevent solid TA from being deposited on any cooling surface of the first reaction zone. The formation of TA is restricted by limiting the consumption of oxygen, and also by maintaining a high acetic acid: para-xylene ratio in the reaction medium to prevent the deposition of butadiene, and by selecting an appropriate coolant (such as boiling water) and a cooling device to avoid Cold spots are formed anywhere in the reaction medium. -9 -

557293 A7 __ _ B7 V. Explanation of the invention (7) When leaving the first reaction zone, when it enters the existing conventional oxidation reactor, the pressure of the reaction medium is reduced at the same time. This reactor is basically a 'stirring: tank reactor or bubble tube reactor. The pressure can be conveniently reduced by passing the reaction medium through one or more pressure reducing valves located around the reactor. Best results are obtained when the reaction medium is rapidly dispersed after entering the second reactor. Rapid dispersion can be achieved using a method known to disperse a para-xylene-containing feed in a conventional reactor. For example, in a stirred tank reactor, this involves injecting the reaction medium into the reactor below the liquid line and near the discharge of the stirring impeller. In bubble column reactors, the reaction medium can be rapidly dispersed by injecting it near the air feed. Referring now to the drawings, FIG. 1 is a simplified diagram of a preferred embodiment of the present invention. This method is performed by first forming a feed 10 comprising acetic acid, water and an oxidation reaction catalyst. In practice, the feed stream contains a mixture containing tritium recycled acetic acid, recycled mother liquor, and catalyst, line U, (ii) reactor condensate from the second reactor 'line 12, and (1) unused acetic acid Supplement, line 13. The mixed feed stream contains typical catalyst components (e.g., Co, Mn, Br) (a typical dilution concentration form used in a single conventional oxidation reactor). As appropriate (but not without ) 'Make some catalyst-containing mother liquor (official line 11) from another part of the method directly into the second reactor 20 to control the catalyst concentration in the first reaction zone. Based on the temperature of each component, the temperature of the mixed feed stream is usually from 130 ° C to 160 ° C. It is found that the temperature is from 130 ° C to 160. (: The oxidation reaction is triggered within the range -10- This paper is suitable for financial @ @ 家 料(⑽) M size (don't read x 297)

557293 A7 ____B7 5. The effect of the invention description (8) is satisfactory. The pressure of the mixed feed stream 10 is increased to at least about 2,000 kPa due to a suitable pump 14, but typically exceeds this pressure. The pressure selected ensures that all gaseous oxygen introduced through the line will dissolve in the feed core before the first reactor 3 shown, and the mixed feed stream with 'aerobic dissolution therein' will be fed through line 3 1 The para-xylene simultaneously and continuously entered the plug flow reactor 30, which initiated the reaction. Para-xylene can optionally be a premix with an acetic acid solvent and this mixture is fed via line 31. It is generally desirable to introduce all para-xylene into the first reactor 30, and depending on the condition, let a fraction of para-xylene feed directly into the second reactor 20, which is also within the scope of the present invention. . When a part of the para-xylene feed directly enters the second reactor 20, the solvent in the reaction medium in the first reactor is obtained. The mass ratio of para-xylene will vary with the amount of para-xylene that bypasses the first reactor. -The xylene ratio is increased, therefore, this ratio is in the range of 80: 1 to 100: 1 or higher. The oxygen molecules are dissolved in the mixed feed stream using any convenient on-line mixing device 33 so that the dissolved oxygen concentration in the mixed feed stream is as high as 30% (weight / weight I). The mixing device 33 may be a lined nozzle for exhausting oxygen into the feed stream. A wired static mixer (not shown) can also be located upstream of the first reactor 30 to facilitate mixing. According to the present invention, it is also possible to introduce oxygen in batches, that is, to introduce oxygen at the first reaction zone 30 I ', at a position in the spring. By injecting oxygen in batches, the local maximum oxygen concentration can be reduced, which also reduces the reactor operating pressure. Reducing the operating pressure of the reactor can reduce the cost of the reactor, oxygen compressor and related equipment. The residence time of the reaction medium in the plug flow reaction zone 30 is quite short, that is, -11-this paper is suitable for financial standards @ 家 standard (CNS) grid (21QX 297 public love) — 557293

Less than 6 minutes. The reactor 30 shown in Fig. 1 is a shell and tube design. The reaction medium passes through the tube, and a coolant (such as compressed water (PW)) is introduced into the shell side, where the water boils and is removed in the form of tritium / fly (S). A small amount of water scrubbing (boiler outgassing, BB) is used to control the accumulation of impurities / residues in the water system. The pressure and temperature of the water vapor produced by k were used to keep the temperature of the reaction medium leaving the first reactor 30 below 21 °. As described above, according to the control parameters of the present invention, it is possible to control the oxygen consumption of the reaction medium in the first reaction zone to less than 50% of the oxygen required for complete conversion of para-xylene to TA. Therefore, p-xylene is basically converted into TA intermediates in the first reactor 30, such as: p-tolualdehyde, p-toluic acid, and 'eg A. Under the aforementioned conditions and effective outlet temperature control, the first reactor will not produce any solid TA. Although π in Figure 1 is a shell and tube reactor design, the reactor 30 may be any suitable reactor design with optional heat removal and multiple oxygen injection equipment. For example, the reactor may be a multi-tube with oxygen injected upstream of the reaction medium in each tube. Alternatively, the reactor may be a single cooled or uncooled (adiabatic) stirred tank reactor in which oxygen is injected upstream and / or into the reactor. Alternatively, the reactor may be a series of cooled or uncooled stirred tank reactors in which oxygen is injected upstream and / or into the reactor. In another alternative, an inverse mixing reactor (such as a suction loop reactor) can be used, and oxygen is injected into the circuit and heat is removed from the circuit, as shown in Figure 2 of the accompanying drawings. As described in the embodiment shown in FIG. 1, the reaction medium leaving the plug-shaped flow of the first reactor 30 enters the second reactor via the line 19 (that is, oxidation-12-suitable paper country) a Domestic Standard (CNS) μ Specification (Ca 297 Public Love) 557293 A7 ___ B7 _______ V. Description of the Invention (1Q) Reaction Zone) 20, as shown, may be a conventional continuous stirred tank reaction of an existing method Device. At the same time, the dust force of the reaction medium is reduced to the range of 1,000 kPa to 2,000 kPa. The pressure can be conveniently reduced by passing the reaction medium through one or more pressure reducing valves or nozzles 2 located around the reactor 20, where the reaction medium is injected into the reactor at a low level. Disperse quickly in the liquid line and close to the impeller area. The process conditions of reactor 20 (ie, temperature, pressure, catalyst concentration, and residence time) are in the usual range, but the oxygen consumption is reduced to reduce the oxidation reaction intensity. An unused air or oxygen-containing gas feed (line 22a) is introduced and quickly dispersed in the reaction medium in the second reactor 20 by any convenient means. TA will precipitate in the reactor 20 to form a slurry, and can be recovered from the reactor system via the official line 23 using conventional methods. The reactor surplus steam from reactor 20 should contain some acetic acid and water, which are condensed via condenser 24, and most of the condensate is recycled (ie, reused) via line 12 to supplement the first reactor 3 0 feed stream. A portion of the acetic acid and water condensate stream (so-called derived water) is transferred to a solvent dehydration system to remove the reaction water. Optionally (but not shown), a portion of the condensate can be returned to the reactor 20, into the reactor head space via a re-distillation device, and / or via a separate feed line or through and away from the feed stream (line 19) Mix into the reaction zone. The present invention proposes a reliable and affordable method for performing TA oxidation in stages, whereby the production capacity of a conventional single-stage oxidation reactor found in many commercial operations of the p-phthalic acid process can be increased 100%. -13 ·

Claims (1)

098800 ABCD Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 557293 • A method for improving the production capacity of an oxidation reactor for a catalytic liquid-phase air oxidation reaction for the conversion of p-xylene to p-phthalic acid. The method s includes the steps of dividing the reaction into the following sequential steps : 0) A feed stream containing acetic acid and an oxidation catalyst is formed within an elevated pressure range of 2,000 up to 20,000 kPa; (b) the feed stream is oxidized; (c) continuously and simultaneously ( 1) An oxygen-containing feed stream, (p-para-xylene is led to the first reaction zone upstream of the conventional oxidation reactor to form a reaction medium ', where the mass ratio of acetic acid: para-xylene is from 10 -2: 0: 1 and the reaction product formed remains in solution; (d) limiting the oxygen consumption of the reaction medium in the first reaction zone to the oxygen required to completely convert p-xylene to p-phthalic acid Less than 50% of the amount; and (e) introducing the reaction medium into the conventional oxidation reactor and simultaneously reducing the pressure of the reaction medium to the range of 15000 kPa to 2,000 kPa. Method, wherein the first reaction zone is a plug flow Reactor or reverse mixing reactor. 3 The method according to item 2 of the patent application, further comprising the following steps: (a) evaporation of a part of the acetic acid present in the conventional oxidation reactor; (b) from the top of the reactor tower Remove the steam; (c) condense the steam; and (d) circulate part or all of the condensate to the feed stream. 4. If the method of the scope of claims 1 or 3 of the patent application, including a part of the- The xylene feed was diverted from the first reaction zone into the customary reactor. -14- This paper conforms to China National Standard (CNS) A4 (210 X 297 mm). 557293 A8 B8 C8 D8 6. The scope of the patent application is used to make the solvent in the reaction medium in the first reaction zone: p-xylene mass ratio as the p-xylene feed section bypassing the first reaction zone Increase and adjust to more than 25: 1 steps. Please read the notes on the back first and then 4% of this page I I I Order i I Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 5 This paper is sized to the Chinese National Standard (CNS) A4 (210 X 297 mm)