TW593259B - Production of aromatic carboxylic acids - Google Patents

Abstract

A process for the production of an aromatic carboxylic acid comprising contacting in the presence of a catalyst, within a continuous flow reactor, one or more precursors of the aromatic carboxylic acid with an oxidant, such contact being effected with said precursor(s) and the oxidant in an aqueous solvent comprising water under supercritical conditions or near supercritical conditions close to the supercritical point such that said one or more precursors, oxidant and aqueous solvent constitute a substantially single homogeneous phase in the reaction zone, wherein the contact of at least part of said precursor with said oxidant is contemporaneous with contact of said catalyst with at least part of said oxidant.

Description

593259 A7 B7 V. US Provisional Patent Application for Invention Description (1) This application claims the priority benefit of No. 60 / 219,388 filed on July 19, 2000. The present invention The present invention relates to a method for producing an aromatic polyacid such as terephthalic acid, isophthalic acid, trimellitic acid, I dicarboxylic acid and benzoic acid. As an example, terephthalic acid is an important intermediate product for the manufacture of polyester polymers, which is typically used in fiber manufacturing and bottle manufacturing. Current state-of-the-art technologies for the production of terephthalic acid include the use of paraxylene feeds in lower (eg, c2-c6) month anti-monokidic acids, usually oxygen molecules in acetic acid, which are commonly combined, such as for Accelerator dissolution of heavy metals catalyzes liquid-phase oxidation under the radio system. Acetic acid is used especially as a solvent because it is quite resistant to oxidation and increases the activity of the catalytic pathway. The reaction is carried out in a vessel under high temperature and pressure conditions, typically between 6 and 30 absolute bars, and terephthalic acid is typically produced in high yields, such as at least 95%. However, the terephthalic acid obtained by ^^ is not purified enough to be used directly in the production of polyisocyanate, because it contains a part of the oxidation intermediates of terephthalic acid as the main impurity, especially 4-sided benzene blankets (心 cba), and a variety of different precursors and colored f. In the traditional method used to make terbium terephthalic acid, most of fen terephthalic acid tends to precipitate when it is formed in the reaction process, although it is low in bath agents under widely implemented conditions. Due to its solubility limitation, 4-CB A tends to co-precipitate with terephthalic acid. This rather crude terephthalic acid therefore needs to be further improved -4-593259 A7 B7 V. Description of the invention (2) One step processing to ensure the acceptable quality of terephthalic acid in advanced polyester manufacturing. This further treatment typically involves dissolving impure terephthalic acid in water at high temperature to make a solution that is hydrogenated in the presence of a suitable catalyst, such as a carbon-supported precious metal catalyst. This hydrogenation step converts 4-CBA to p-toluic acid, and various colored systems present in the relatively impure terephthalic acid are converted to colorless products. This purified terephthalic acid is then removed from the solution by a series of crystallization, solid-liquid separation and drying steps. Because p-toluic acid is more soluble in water than terephthalic acid, the former tends to remain in an aqueous mother liquor after crystallization and solid-liquid separation. A method involving the production of crude terephthalic acid and its subsequent purification by hydrogenation is disclosed, for example, in EP-A-0498591 and EP-A-0502628. In the continuous process described in WO-A-98 / 38 150, it uses a relatively high solvent / precursor ratio, so that essentially all aromatic carboxylic acids produced can be maintained in solution, thereby Co-precipitation of reaction intermediates during the reaction is minimized. As a result, compared with the conventional method, the intermediate product can still be reacted to the desired aromatic carboxylic acid, and the reaction rate of the intermediate product is also increased. By operating the oxidation reaction in this manner, it is possible to reduce the extent to which the aromatic carboxylic acid is contaminated by any aldehydes produced by the intermediates in the reaction process. For example, as mentioned above, in the case of making terephthalic acid by liquid-phase oxidation reaction of p-xylene or other precursors, the reaction produces the production of 4-carboxybenzaldehyde as an intermediate product. Co-precipitation of 4-CBA and terephthalic acid can be largely avoided, because terephthalic acid is not allowed to precipitate during the reaction, at least not to any significant extent. In addition, the paper size required to achieve this -5- applies to the Chinese National Standard (CNS) A4 specifications (210 X 297 mm) 593259 A7 _B7 _._ V. Description of the invention (3) The conditions tend to lead to, for example, 4 -Significant oxidation of intermediate products of CBA to desired end products. Although the method described in WO-A-98 / 38150 proposes a more cost-effective improvement than conventional techniques, it also includes the use of a large number of organic solvents. Although an organic solvent such as acetic acid is particularly used in this oxidation method for the reasons described above, it is desirable to minimize the amount thereof in some cases. This organic solvent is quite expensive and may require recovery and recycling due to environmental constraints. In addition, some organic solvents may be lost due to combustion during the oxidation reaction. Another problem with the use of acetic acid is its flammability when mixed with air or oxygen under the typical reaction conditions of this system. Another problem with the use of conventional solvents such as acetic acid is the low solubility of the oxidizing agent component therein. Therefore, when an oxygen molecule is used as an oxidant, the oxygen molecule mainly exists as a discontinuous bubble in the reaction medium, and only a small part of the oxygen molecule is dissolved in the solvent. To the extent of the reaction between the precursor and the oxygen molecules produced by the diffusion of oxygen molecules from the bubble to the entire liquid, the reaction rate is limited by the low solubility of the oxygen molecules in the solvent.

Holliday RL. Et al. (J. Supercritical Fluids 12, Vol. 1998, pp. 255-260) describe an aromatic compound specifically synthesized from alkyl aromatic hydrocarbons in a reaction medium using oxygen molecules as sub-critical water as an oxidant. Batch carboxylic acid batch method. As it approaches its critical point (374 ° C and 220.9 absolute bar), the dielectric constant of water dramatically decreases from a room temperature 约 of about 80C2 / NM2 to 之 of 5C2 / NM2, which allows it to dissolve organic molecules. As a result, water then acts as an organic solvent so that hydrocarbons such as toluene can be completely dissolved in or near supercritical water. Oxygen molecules are also highly soluble in the sub- and super-pro -6- This paper size applies the Chinese National Standard (CNS) A4 specification (210 X 297 mm) binding

Circles of water. The method described by Holhday et al. Was performed in a sealed autoclave as a batch reaction. The present invention (the purpose is to provide-an alternative and improved continuous process for the production of, for example, aromatic citric acid which is terephthalic acid, in which essentially all of the w group carboxylic acids, i.e. intermediates and precursors, are produced during the reaction The middle system is still maintained in solution 'and the need to use organic substances, such as aliphatic mono-chinic acid as a horse solvent, is removed. A further object of the present invention is to provide an alternative and continuous method for the preparation of aromatic acids Manufacturing, in which all reactants and products are maintained in common during the reaction process. The present invention further (the purpose is to provide _ a method with good selectivity and high yield) for borrowing or super Oxidation of precursors in critical water to produce aromatic carboxylic acids. Oral people now devise a method to overcome one or more of the problems encountered by previous people using supercritical water. 1 Summary According to the present invention, it provides _ A method for the production of aromatic leptin, the second is to contact-or more aromatic, hydrating, and contacting with an oxidant in a continuous flow reactor in the presence of acetic acid, this contact is the former Body and oxygen The agent is fed in an aqueous solvent containing water under supercritical conditions or near supercritical conditions near the supercritical point, so that one or more precursors, oxidants and aqueous solvents can form the essence in the reaction zone. The above-mentioned single homogeneous phase, wherein the contact of at least 1M of the knife w 4 with the side oxidant is in contact with the catalyst and the at least part of the oxidant. Maintained in the wave, rule + run ', and then the aromatic acid is removed from the reaction medium

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Take out. By using water under or near supercritical conditions, the desired aromatic carboxylic acid can be produced without using an aliphatic carboxylic acid such as acetic acid as the main solvent. This method is performed by forming a substantially homogeneous liquid phase between the reactants and the solvent. The components in question are mixed on a molecular level. This is the opposite of the existing method, in which oxygen molecules are present as discontinuous bubbles in a reaction medium such as acetic acid. For the extent of the reaction between, for example, a para-xylene precursor and oxygen molecules generated from the diffusion of oxygen molecules from bubbles to the entire liquid, the reaction rate of known methods is limited by the solubility of oxygen molecules in acetic acid, which Department, not high. Operating under supercritical or near supercritical conditions as a solvent operates to transform the kinetics of the reaction, as the k-degree of oxygen molecules in water increases significantly as its supercritical point approaches and exceeds. Furthermore, when the water solvent is in supercritical or near supercritical conditions, the reaction kinetics will be further increased by the temperature. The combination of high temperature, high concentration, and homogeneity means that the reaction to convert the precursor to an aromatic carboxylic acid can occur extremely quickly. It is the same as the traditional technology using a crystalline three-phase oxidation reactor, such as terephthalic acid. Comparison of residence time in the production of aromatic carboxylic acids. Under the conditions described herein according to the present invention, the intermediate aldehydes (such as 4-CBA in the example of terephthalic acid I) can be easily oxidized to the desired aromatic carboxylic acid, which can be decomposed in In a supercritical or near-supercritical liquid, the degree of contamination of the obtained aromatic carboxylic acid product with aldehyde intermediates can be significantly reduced. As mentioned above, in the conventional method of oxidizing p-toluene to terephthalic acid, terephthalic acid is only partially dissolved in an aliphatic carboxylic acid solvent,

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593259 A7 ___B7__ V. Description of the invention (6) and it will precipitate during the reaction; because the conversion of 4-CB A into terephthalic acid is relatively slow, 4-CBA is therefore in the reaction process and the subsequent p-benzene The dicarboxylic acid recovery process tends to co-precipitate with terephthalic acid. The method of the present invention is particularly advantageous because it essentially overcomes the problems of precursor autocatalytic destruction oxidation and catalyst consumption. In addition, the method of the present invention includes a short residence time and exhibits good selectivity for high yields and product formation. Detailed description of the invention In the method of the present invention, the pressure and temperature of the method are selected to ensure supercritical or near supercritical conditions. Therefore, the operating temperature is typically in the range from 300 ° to 48 ° C, more preferably from 330 ° to 450 ° C, and typically from about 350 ° C. Lower limit to 370 ° C to upper limit of about 370 ° to 420 ° C. The operating pressure is typically in the range of about 40 to 350 absolute bars, preferably 60 to 300 absolute bars, more preferably 220 to 280 absolute bars, and especially 250 to 270 absolute bars. "Approaching supercritical conditions" means that the reactants and the solvent constitute a substantially homogeneous homogeneous phase; in practice, this can be achieved at conditions below the critical temperature of water. According to a specific embodiment, the term "approaching supercritical "Critical condition" means that the solvent is at a temperature not exceeding 50 ° C, preferably not exceeding 35 ° C, and more preferably not exceeding 20 ° C, below the critical temperature of water at 220.9 absolute bar. A 'continuous flow reactor' refers to a reactor in which the feeding and mixing of reactants and the removal of products are performed simultaneously in a continuous manner, as opposed to a batch type reactor. For example, the reactor may be a plug flow reactor, although aspects of the invention defined herein are not limited to this particular type.-9- This paper size applies the Chinese National Standard (CNS) A4 specification (210 X 297 mm) 593259 A7 _B7 _._ V.-Description of Invention (7) continuous flow reactor. In the method of the present invention, essentially all of the aromatic carboxylic acid produced in the reaction, and in any case not less than 98% by weight of the aromatic carboxylic acid are maintained in the solution during the reaction until the solution leaves the oxidation reaction zone and is cooled. Will precipitate. By implementing the method in a continuous flow reactor, the residence time of the reaction is compatible with the conversion of the precursor to the desired aromatic carboxylic acid without significant degradation product manufacturing. The residence time of the reaction medium in the reaction zone usually does not exceed 10 minutes. However, in practice, the reaction is almost completed when the reactants are mixed. Therefore, the "retention time" of the reactants in the reaction zone is very short, usually on the order of 2 minutes or less. The residence time can be controlled so that the precursor can be quickly converted into the corresponding aromatic carboxylic acid, and its high efficiency is such that the aromatic carboxylic acid precipitated from the reaction medium after the reaction is complete contains a small amount of aldehyde in nature Intermediate products, such as no more than about 5000 ppm, and even as low as 1500 ppm, and in some cases no more than about 500 ppm, are produced as intermediate products during the reaction (for example, in 4-CBA in the formic acid production example). Typically, at least some aldehydes will be present after the reaction, and usually at least 5 ppm. A reactor system suitable for carrying out the method of the present invention can usually be configured as described below. There may be more than one reaction zone, connected or connected in parallel. For example, when multiple reaction zones are used in parallel, the reactants and solvents can form separate flow streams to pass through the reaction zone. If necessary, the product streams generated from this multiple reaction zone can be combined to form a single product stream. Response to using more than one -10- This paper size applies to China National Standard (CNS) A4 (210 X 297 mm) binding

Line 593259 A7 B7 V. Description of the invention (8) The conditions such as temperature conditions may be the same or different in each reactor. Each reactor can be operated adiabatically or isothermally. Isothermal or controlled temperature rise can be maintained by heat exchange to define a predetermined temperature distribution of the reaction in the reactor. In one embodiment of the invention, the heat of reaction is removed from the reaction by heat exchange with a heated fluid, which is based on conventional techniques known to those skilled in the art. In a specific embodiment, the heated flow system passes through one or more walled flow channels, and its external surface is exposed to the reaction medium in the reaction zone. For example, • The reactor can be designed like a shell and tube heat exchanger, and the reactants and solvents pass through the shell side, and the heated flow system passes through the tube side inside the shell side. However, I do not rule out the possibility of heat transfer in other ways, such as by passing the heated fluid through a sleeve configuration that at least partially surrounds the reaction zone. For example, the tube side in the shell-side design mentioned above may be such that the reactants and solvents flow through the tube side and the heated fluid passes through the shell side. The heated fluid may flow through the reaction zone in a reverse and / or co-directional relationship with the reaction medium flowing through the reaction zone. It is convenient to arrange the channels of the heated fluid to extend inside the reactor. It is advantageous to treat the heated fluid after heat exchange with the reaction medium to recover heat, machinery and / or electricity. The recovered power can be used in part for pressurized air or oxygen supplied to the process as an oxidant, such as driving a compressor suitable for this purpose. For example, the heat delivered to the heated fluid can be converted into machinery or electricity in a power recovery system. One method is to use a heated fluid to generate high-pressure steam, which can then be superheated and supplied to a steam turbine to obtain electricity -11-This paper size applies Chinese National Standard (CNS) A4 specifications (210 X 297 mm) 593259 A7 _B7___ V. Invention Description (9) Yes. Sufficient electricity can be obtained to export from the factory. The heated fluid conveniently contains water. The heated fluid can be preheated before passing through the reaction zone, and this preheating can be performed by heat exchange with the product stream from the oxidation reaction. The oxidant in the method of the present invention is preferably an oxygen molecule, such as air or oxygen-rich air, but preferably contains a gas containing oxygen as its main component, more preferably pure oxygen or oxygen dissolved in a liquid. Although not excluded from the scope of the present invention, the use of air is not advantageous because the high nitrogen content of the air will result in high compression costs and requires exhaust gas treatment equipment to properly handle large amounts of exhaust gas. On the other hand, pure oxygen or oxygen-enriched gases allow the use of smaller compressors and smaller tail gas treatment equipment. The use of oxygen molecules as oxidants in the method of the present invention is particularly advantageous because it is highly soluble in water in supercritical or near supercritical conditions. Therefore, at a certain point, the oxygen / water system will become a single homogeneous phase. In addition to the oxygen molecule, the oxidant may contain atomic oxygen from the compound, such as a liquid phase compound containing one or more oxygen atoms per molecule at room temperature. This compound is, for example, hydrogen peroxide, which can be used as a source of oxygen by the reaction or decomposition described by Lin Smith et al. (International Journal of Chemical Kinetics, Vol. 23, 1991, p. 971). The method of the present invention is performed in the presence of an oxidation catalyst. The catalyst may be a reaction medium containing a solvent and an aromatic carboxylic acid precursor or an anisotropic catalyst may be used. Catalysts, whether homogeneous or heterogeneous, typically contain one or more heavy metal compounds, such as starting and / or ballasting compounds, and optionally include an oxidation promoter. For example, the catalyst can have -12- this paper size applies to China National Standard (CNS) A4 specifications (210 X 297 mm) 593259

: Any type used in the body ’s nocturnal phase oxidation in the aliphatic chitosan solvent, such as the aromatic chitosan which is the precursor of terephthalic acid, such as the desert of the bell, the acid of the chain @@ or Chain ㈣ @ Purpose (usually, for example, chain acetic acid @ ⑶ C4 of acetate). In addition to / and other materials, other heavy metal compounds, such as rhenium, iron, iron, 4 meshes, such as rare earth metals such as hafnium, knots, donors and / or nickel can also be used. Advantageously, the catalyst system may include subbromide (2). The oxidation catalyst may alternatively or additionally include one or more precious metals or compounds thereof, such as platinum and / or compounds thereof, such as in highly segmented form or in the form of a metal. When it is used as an oxidation accelerator, it can be elemental stream, material desert (for example, ·, Secret, KBr, NhBO and / or organic bromide (for example, bromobenzene, benzyl bromide, (Acetic acid, bromoacetic acid bromide, tetrabromoethane, ethylene di-desert, etc.). In addition, the oxidation promoter may contain ketones such as methyl ethyl copper, or aldehydes such as ethyl ether. When the catalyst is in a heterogeneous form, it can be appropriately located in the reaction zone to ensure contact between the continuously flowing reaction medium and the catalyst. In this example, the 'catalyst can be supported and / or forcedly fixed in the reaction zone to Ensure this contact does not unduly restrict the flow cross-section. For example, a heterogeneous catalyst can be coated or applied to a stationary element (such as an element forming an open network structure) in the reaction zone to make the reaction The mass flows through it. As the reactants pass through the reaction zone, this stationary element can additionally be used to improve its mixing. In addition, the catalyst can be in the form of moving spheres, particles, precision separation, metal sponges, etc. The provided device can be limited in the reaction zone if necessary, so that catalyst balls and other materials can flow through the reactor during operation. 13- This paper size applies to China National Standard (CNS) A4 specification (210 × 297 mm) 593259 A7 B7 V. Description of the invention (11) Suspended or immersed in the reaction medium of the reaction zone. The use of any of these forms of heterogeneous catalysts can confer the advantage of limiting the catalytic effect in a well-defined area 'to allow the reaction medium to pass In the region, further oxidation occurs at a reduced rate or can be greatly suppressed. The support used for the oxidation catalyst may be less catalytically active or even inert to the oxidation reaction. The support may be porous and typically has The surface area of the pore area is at least 25 m2 / g to 25 m2 / g, for example from 50 m2 / g Per gram to 200 square meters per gram, and having a surface area of about 80 square meters per gram to about 150 square meters per gram is preferred. Under normal conditions, the catalyst support material should be essentially corrosion resistant and essential. Antioxidant. The carrier component of the oxidation catalyst may be a purified or composite material. The latter is, for example, used to apply desired chemical or physical properties to the catalyst. In a preferred embodiment, the catalyst carrier material contains zirconia. The oxidation reaction is initiated by heating and pressurizing the reactants and then placing the heated and pressurized reactants together. This can be performed in many different ways such that one or two reactants reach supercritical or near Supercritical condition 1 or later is mixed with the water solvent, and the mixing is performed in a manner that maintains the reactants isolated from each other before being placed in the reaction zone. In the continuous method of the present invention, the configuration of the reactor system When the agent is in contact with at least part, and preferably substantially all oxidants, the contact of the oxygen agent with at least part, and preferably substantially all precursors, is in the reactor system. Do the same at the same point. "In the first / the only examples, after the aqueous solvent has been heated and the pressure has obtained a supercritical or near supercritical state, the oxidant is mixed with the aqueous solvent,

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And before mixing with the aqueous solvent, it is appropriately pressurized and a teaching oxidizing agent is added if necessary. The front system is pressurized and heated if necessary. In the case of a method using a homogeneous catalyst, the catalyst component is pressurized and heated if necessary. The precursor, the like, and the oxidant / mixture are then contacted simultaneously. In the example using a heterogeneous catalyst method, the 'precursor' and the oxidant / solvent mixture are contacted in the presence of a catalyst. In the second specific embodiment of the present invention, after the aqueous solvent has been heated and pressurization has obtained a supercritical or near supercritical state, the pre-system is mixed with the aqueous solvent, and before mixing with the aqueous solvent, the pressure is appropriately increased and If necessary, heat the precursor. In one arrangement, the homogeneous catalyst component is contacted with the aqueous solvent simultaneously with the contact of the precursor and the aqueous solvent after pressurization and optional heating. In an alternative configuration, the heterogeneous catalyst is used as described and is limited to the reaction zone. The oxidant after being pressurized and if necessary heated is mixed with the aqueous solvent after it has been heated and pressurized to obtain a supercritical or near supercritical state. In the case of a method using a homogeneous catalyst, the oxidant / aqueous solvent mixture is then contacted with a mixture containing a precursor, a catalyst, and an aqueous solvent. In the case of a method using a heterogeneous catalyst, the oxidant / aqueous solvent mixture is in a reaction zone, i.e. in the presence of a heterogeneous catalyst, and is contacted with a mixture containing a precursor and an aqueous solvent. The contact of the various streams can be carried out by separate feeding methods of the feeding device, where the feeds are combined to form a single uniform liquid phase to react the oxidant with the precursor. Feed combining devices may, for example, have gamma, T, X or other configurations to allow separate feeds in a single flow channel forming a continuous flow reactor, or in some cases forming two or more continuous flow reactors -15- " This paper size applies to China National Standard (CNS) A4 specifications (210 X 297 mm) 593259 A7 B7 V. · Description of the invention (13 Merging in the flow channel. Flowing materials combined with feed may sometimes have Or a tubular configuration area without dynamic or static mixing elements. In a preferred embodiment, the use of an in-line or static mixer to ensure rapid mixing and uniformity is advantageous, such as increasing the solubility of the oxidant in an aqueous solvent. A single phase is formed. The oxidant feed and the precursor feed can be placed at a single point or contacted at a single point or in multiple stages, so that at least one or two parts of the feed Feed in a gradual manner, such as through multiple injection points, relative to the direction of flow through the reactor. For example, one feed can pass along a continuous flow channel and the other feed is elongated in the continuous flow channel Feed their towels at a number of points on the top so that the reaction proceeds progressively. The feed passing along the continuous flow channel may include an aqueous solvent, which can be fed at multiple locations as feed. Similarly, € The addition of chemical agents, especially homogeneous catalysts, can be performed in a progressive manner, such as via multiple injection points, relative to the direction of flow through the reactor. In specific embodiments, the% chemical agents are in two or more Feed into the reaction at this position. This position is conveniently placed relative to the full flow of solvent and reactants passing through the oxidation zone, so that the oxidant is at the starting position and at least another position downstream of the starting position Feed into the reaction. After passing through the continuous flow reactor, the reaction mixture is a solution containing aromatic carboxylic acids. Contrary to traditional methods, essentially all aromatic carboxylic acids produced in the reaction are at this stage. Solution. The solution may also contain certain catalysts (if used), and a relatively small amount such as intermediate product-16-This paper size applies to China National Standard (CNS) A4 (210X297 mm) 59 3259 A7 _B7 _._ 5. Description of the invention (16) The second stream is mixed at the beginning or in front of reactor 2 and the mixture passes through the reactor. In Figure 2B, the 02 / water stream is injected in multiple steps in a progressive manner. It was added to the reactor at a point. After leaving the reactor, the stream was cooled and depressurized in the back pressure regulator 3. The product was entrained in the cooling water stream. Corresponding to Figures 2C and 2D, the catalyst was already out of phase The form of catalyst exists in the reactor. Referring to FIG. 3, the feed ingredients containing water, para-xylene and oxygen molecular gas are pressurized to operating pressure and are continuously supplied from individual sources 10, 12 and 14 via preheater 16 Where the ingredients are heated to a temperature of 300 ° to 480 ° C, more preferably 330 ° to 450 ° C, and typically a lower limit from about 350 ° to 370 ° C to about 370 ° to 420 ° C The upper limit is that the pressure and temperature are selected to obtain supercritical or near supercritical conditions. The portion of the heat used to preheat the feed ingredients can come from the exothermic heat generated during the subsequent reaction between the terephthalic acid precursor (i.e., paraxylene in this embodiment) and the oxidant. The heat from other sources may be, for example, in the form of high pressure steam and / or heating may be performed by directly heating the heated water stream. The heat of reaction can be removed in any suitable manner, such as by heat exchange between the reacted liquid and a heated fluid such as water. For example, the heated fluid may be arranged to exchange heat in a reverse and / or co-directional manner with reactants and solvents passing through the reaction zone. The passage of the heated fluid through the reaction zone may be outside the reaction zone and / or may extend through the reaction zone inside. This internally extending flow channel may be, for example, parallel and / or transverse to the general direction of the reactant / solvent flow through the reaction zone. For example, the heated fluid may traverse the reaction zone by passing through one or more coils located inside the reactor. The reaction can include recovering power through a suitable power recovery system such as a full wheel; for example, a heated fluid such as water can be used to produce -19-This paper size applies Chinese National Standard (CNS) A4 specifications (210 X 297 mm) 593259 A7 _ B7 _._ V. Description of the invention (17) For example, high-pressure saturated steam at a temperature and pressure of 300 ° C / 100 absolute bar, which can then be superheated by external heat and fed into a high-efficiency condensing steam turbine for recovery power. In this way, the reactor can be maintained at the optimum temperature and effective energy efficiency can be achieved. In an alternative method, the reactor can be operated at absolute pressure and a suitably high flow rate of water flowing through the reactor can be used to limit the temperature rise in the reaction zone during operation. If desired, a combination of the two methods can be used, i.e. the reaction enthalpy is recovered via the heated fluid and the combined water flows through the reactor at an appropriate water flow rate. After the feed ingredients are heated, the oxygen system is mixed with water. As a result of preheating and pressurization, the results will be in supercritical or near supercritical conditions and can therefore dissolve the feed. In the specific embodiment in FIG. 3, oxygen and water are mixed in a premixer 18A. The precursor is also mixed with water in a premixer 18B. Of course, the precursor can also be separately premixed with water before entering the preheater 16. The pre-mixer (or pre-mixer of each reactant and water pre-mixing system) can have various forms such as Y, L or T element, double T configuration or static mixer, as shown in Figure 4A , 4B, 4C, 4D and 5, respectively. In Figures 4A to 4D and 5, the reference symbol A refers to the preheated water supplied to the premixer, B refers to the reactants (p-xylene or oxygen) and P refers to the resulting mixture stream. In the double-T configuration of FIG. 4D, the two-mixture stream system generates P1 and P2. These can be passed through separate continuous flow reactors or combined into a single stream and then passed to a single continuous flow reactor. X-component configurations can also be used, as known to those skilled in the art. It can be understood that in addition to pre-mixing one or two reactants with water before feeding into the reaction zone, the reactants and water can be separately fed into the reaction zone and the Chinese national standard (CNS ) A4 size (210 X 297 mm) binding

Line 593259 A7 _ B7 _._ V. Description of the invention (18) The reaction zone is mixed with the help of some form of mixing configuration (such as a static mixer), so that essentially all the components are mixed in the reaction Happened in the district. When a homogeneous catalyst is used in the reaction, the catalyst is added as a solution from source 19 to the precursor in a premixed oxygen / water stream while entering the reactor or at the beginning of the reactor (ie, Figure 1A). (Shown) is added to the premixed oxygen / water stream. After preheating and premixing, the feed ingredients are combined in reaction zone 20 to form a single homogeneous liquid phase, where the reactants are placed together. The reaction zone 20 may be in the form of a tubular plug flow reactor composed of a simple mixer configuration, such as a length of duct, which is combined with the flow rate of the combined reactants to provide an appropriate reaction time for Toluene is converted to terephthalic acid with high conversion and low 4-CBA content. When the reaction system is carried out in the presence of a heterogeneous catalyst system (ie shown in Figure 1B), the catalyst system can be distributed lengthwise in the flow direction and can be expanded with the reaction zone so that when supercritical or near supercritical liquid flows over the catalyst When the system occupies the duct area, the reaction rate can be greatly reduced to suppress the generation of degradation products.

The reactants may be '' injected '' upstream of the reactor 20 to combine. In addition, it can inject one reactant at multiple points along the length of the reactor into a stream containing another reactant in a gradual manner to combine. One method of implementing a multi-injection configuration is shown in the continuous flow reactor of Fig. 6, where the reactor is constructed by a conduit P. In a specific embodiment where the premixed oxygen / water stream is added to the premixed precursor / water stream (as shown in FIG. 2D), the premixed paraxylene / supercritical or near supercritical water stream W is supplied To Catheter P -21-This paper size applies to Chinese National Standard (CNS) A4 (210X 297 mm) 593259

4 ^ 游 尾 *. For the method of making the material phase catalyst, the water stream w should also contain d '. In the method using a heterogeneous catalyst, the catalyst should exist in the guide gp (internal loop. The stream is passed through the reactor duct p and along the duct p The length of the series & separated, pre-heated and compressed oxygen dissolved in supercritical or near supercritical water is supplied here through the injection channel ME to produce an aqueous solution containing supercritical or near supercritical water. The acid (product {S. In this way, it must be used to complete the para: Oxidation of toluene to terephthalic acid. The oxygen is injected in a gradual manner, the purpose is to control the oxidation and make side reactions. Minimal combustion with possible paraxylene, terephthalic acid or terephthalic acid intermediates.

Referring now to FIG. 3, after the reaction reaches a desired level, the supercritical or near supercritical system is passed through the heat exchanger 22, and the heat exchange liquid system is circulated through the closed circuit 24 to recover heat for use in the preheater 16. One solution (not shown) of terephthalic acid solution cooling after reaction involves the use of a heat exchanger network to cool the substream to a subcritical temperature, such as a grade of 30 (rc to maintain the terephthalic acid product at In solution and thereby avoiding the danger of contaminating the heat exchange surface, a column of flash crystallizers (similar to those traditionally used for purification of terephthalic acid by hydrogenation) is used to cool and precipitate the terephthalic acid product. The liquid after the cold part is then supplied to the product recovery zone 26, where terephthalic acid is precipitated from the solution. Any suitable product recovery method known to those skilled in the art can be used. Product recovery zone 26 It may contain one or more stages of sufficient cooling or evaporation to crystallize the terephthalic acid into a terephthalic acid crystal slurry in an aqueous mother liquor. When the product recovery zone 26 contains one or more flash boiling evaporation crystallizers, it comes from the crystallizer The generated flash boiling stream can be -22- This paper size applies to China National Standard (CNS) A4 (210 X 297 mm) binding

Line 593259 A7 _ B7 _._ V. Description of the invention (2Q) Indirectly via a traditional heat exchanger or by injecting flashes directly into the water and / or para-xylene to be fed into the reactor for pre-treatment The water and para-xylene streams that are hot into the reactor. The slurry obtained after crystallization can be used for solid-liquid separation using, for example, a filtration device operating under high pressure, normal pressure or low pressure conditions with or without washing equipment, such as the previously published international patent application number WO -A-93 / 24440 and WO-A-94 / 17982 (the disclosures of which are incorporated herein by reference). Therefore, for example, an integrated solids separation and water washing unit may include a belt filter unit, a rotating cylindrical filter unit operated on the side of the slurry, or a drum filter unit (for example, formed by several slurry receiving chambers). BHS-Fest pressure filter drum, in which the mother liquor is removed from the filter cake by water under the pressure of water supplied to the receiving chamber). After filtration of the slurry, the obtained terephthalic acid can be used directly in the manufacture of polyesters, for example for packaging, such as bottles or fibers. It can likewise be dried. If it is not at atmospheric pressure, the filter cake of terephthalic acid can be sent to a low-pressure area (for example, atmospheric pressure) for drying by a suitable pressure reducing device, such as a closed funnel device, a rotary valve, an impact type pump, and a screw feed. The device is, for example, a progressive feeding device of the progressive cavity pump type for pumping high solids cooling pastes. The separation temperature and the degree of washing required are related to the amount of impurities produced in the reaction, the device for obtaining the product and the required product specifications. Although in general, it is desirable to make sufficiently purified terephthalic acid so that no further purification is necessary (e.g., by oxidation and / or hydrogenation of an aqueous solution of terephthalic acid to convert 4-CB A to p-benzene Dicarboxylic acid or methyl benzoic acid, as the case may be), but we do not rule out oxygen in para-xylene supercritical or near supercritical water-23- This paper is in accordance with China National Standard (CNS) A4 (210 X 297 mm) 593259 A7 B7 V. Description of the invention (21) Possibility of performing this purification after chemical conversion. After the aromatic carboxylic acid product is recovered, at least part of the aqueous mother liquor (including dissolved catalyst components if homogeneous catalysis is used in the oxidation reaction) can be recovered for reuse in the oxidation reaction, such as with fresh water and / or reaction物 incorporating. However, if the recovered mother liquor contains a catalyst component, it should not be added to the 02 / water stream before the precursor is added. The recovered amount is usually the main part of obtaining the mother liquor, and in order to reduce the fixed concentration of by-products in the process, an exhaust stream is taken out. The exhaust stream can be processed to obtain its catalyst and organic components. 7, in this embodiment, liquid oxygen (line 30), liquid para-xylene (line 32), and water (line 34) are supplied to the mixing unit 36. The supplied oxygen and para-xylene are pressurized via pumps 38, 38A and heated to higher temperatures, for example, by high-pressure steam in heat exchangers 40, 40A. The mixing unit 36 is configured to mix the reactants with water to produce a second stream 42, 44 where one stream contains a water / para-xylene mixture and the other stream contains oxygen dissolved in water, which is fed continuously in the form of a conduit In the flow reactor 46, the streams are mixed therein by, for example, a static mixing device not shown in a duct to initiate the reaction. FIG. 7 mainly illustrates the configuration of a system using a heterogeneous catalyst. A method using a heterogeneous catalyst for this, described herein as a porous medium, a fixed bed, or other solid catalyst configuration, may be included in the flow volume of the reactor 46. For methods using a homogeneous catalyst, a catalyst in the form of an aqueous solution can be added to the para-xylene / water stream 42 immediately before entering the reactor, or it can be used, for example, as a static mixer, at the beginning of the reactor or immediately before entering the reactor. Or similar devices are quickly mixed to merge with streams 42 and 44. -24- This paper size is in accordance with Chinese National Standard (CNS) A4 (210 X 297 mm) 593259 A7 _B7__ V. Description of the invention (23) Use any device suitable for this purpose, and according to the pressure after the final crystallization stage Arrange to operate under elevated pressure conditions or atmospheric pressure. As mentioned earlier, solid-liquid separation can be performed using integrated solids separation and water washing equipment, such as a rotating cylindrical filter unit containing a belt filter unit or a slurry side operation, or a drum filter Unit (for example, a BHS-Fest pressure filter drum formed by several slurry receiving chambers, in which the mother liquor is removed from the filter cake by water under the pressure of the water supplied to the receiving chamber). In Fig. 7, the obtained terephthalic acid crystal system is supplied via line 64 to a dryer (not shown) or to direct production of polyester. When solid-liquid separation is carried out under elevated pressure conditions, it is convenient to use a suitable device to reduce the atmospheric pressure before sending the crystals to a drying device (for example, International Patent Application No. WO-A-95 / 19355 or the United States Disclosed in Patent No. 5470473). The mother liquid from the solid-liquid separation is obtained via line 66, pressurized by pump 68 and recycled to the mixer via heat exchanger 70, line 72, heat exchanger 50, line 74, start / fine-tune heater 76, and line 34 Unit 36. Therefore, under steady-state operating conditions, the recovered mother liquor can serve as a source of water to be supplied to reactor 46 and as a carrier for catalyst recycling to the process, especially when the oxidation process uses a homogeneous catalyst system. The mixing unit 36 is configured so that when the recovery mother liquor may contain a catalyst, that is, a homogeneous catalyst, the recovery mother liquor is mixed with the para-xylene stream instead of the oxidant stream, because the catalyst should be added with the oxidant simultaneously with the precursor occur. Therefore, when the recovered mother liquor contains a catalyst, the mixing unit is configured so that the oxidant stream 30 can be mixed with fresh water from the pipe 35. Because water is generated during the reaction, water needs to be discharged from the system. This can be -26- This paper size applies Chinese National Standard (CNS) A4 specifications (210 X 297 mm) 593259 A7 __ —_ B7 V. · Description of the invention (24 ') In several ways; for example, emissions can be The latter may be more advantageous as it is removed via line 78 or from a suitable flash condensate (as will be described in conjunction with the energy recovery system described below), as compared to the discharge of mother liquor obtained via line 66, Is less polluted by organic matter. However, the obtained emissions can be treated by emissions, such as aerobic and / or anaerobic treatment. In the heat exchanger 7G, the temperature of the mother liquor is increased by about 30 to 10 by heat exchange with the crystallizer vessel I vapor from one or more crystallization stages, such as the highest pressure and temperature of the first stage. 〇. 〇. After being passed through the heat exchanger 70, the glitter Buddha (line 79) can be returned to the product recovery area in the form of condensate for use as a terephthalate filter for washing solid-liquid separation. Cake I wash water. In the heat exchanger 50, as a result of the heat exchange with the high-temperature product stream 48 of the tap reactor ，, the temperature of the mother liquor is further increased, for example, by about 100 to 200 r. In this way, the product stream is Z-cooled and the temperature of the mother liquor recycle stream is greatly increased. Fine-tuning / initial heater 76 is needed to raise the temperature of the mother liquor recycle stream to supercritical or near supercritical conditions. Under stable operating conditions of the method, liftability may be optional because the mother liquor can be supercritical or near supercritical after passing through the heat exchanger 50. Under steady state conditions, the heater 76 is therefore not necessary and can be used purely for initial operation, which initially uses pressurized water from a source rather than a mother liquor. In this embodiment, the aqueous solvent is supercritical or near supercritical before being mixed with one or two reactants. It is understood, however, that an increase in temperature to ensure that the desired supercritical or near-supercritical conditions can be performed before, during, and / or after the mixing stage. In the specific embodiment of FIG. 7, which is generated during the reaction between the precursor and oxygen -27- This paper size applies the Chinese National Standard (CNS) A4 specification (210 X 297 mm) " --- 593259 A7 _B7__ V.-Invention description (25) The reaction heat is removed at least in part by heat exchange with a heated fluid, preferably water, by means of a loop 80 or a series of generally parallel tubes (such as shell and tube) Tubes in the heat exchanger design) and so on to pass inside the reactor 46. The water used is pressurized and heated to a temperature high enough so that on the external surface of the conduit 80 that guides the water to the reactor, it may cause localization of the reaction medium, such as the precipitation of components of terephthalic acid Cooling can be avoided. The water system used for this purpose comes from an energy recovery system58. Therefore, in FIG. 7, the high-pressure and high-temperature water system is supplied to the heat exchanger 52 via the pipe 82, which is here cooled by the product stream passing through the heat exchanger 50. Water is then passed through line 8 3 to pass through conduit 80 to subsequently generate high pressure, high temperature steam for feeding into energy recovery system 58 through line 84. The energy recovery system 58 is also supplied as one or more stages of flashing steam. This is described by line 88. This steam can be used, for example, to preheat water supplied to the heat transfer pipe 80 via line 82. The condensate from the steam feed treatment supplied to the energy recovery system 58 can be sent to the product recovery zone via line 90 for washing, for example, a terephthalic acid filter cake manufactured in a solid-liquid separation. If necessary, the water discharge 92 can be taken out from the line 90, which has the advantage that removing the discharge at this point will have less pollution than the discharger taking out the mother liquor through the line 78. In FIG. 7 (which, as mentioned, is mainly used to explain the method of using a heterogeneous catalyst opposite to the homogeneous phase), the reactant system shown in the mother liquid and the product stream in the heat exchanger 50 is heat-exchanged and fed. In the recovered mother liquor. In one modification, the reactants can be mixed with the mother liquor recycle stream upstream of the heat exchange of the product stream. At the place where the two reactants are mixed with the mother liquor circulating stream, the latter is -28. The streams are separately mixed with the reactants so that the reactants are kept isolated from each other before being put together for reaction. It will be understood that the specific embodiment of FIG. 7 can be modified in the manner indicated in FIG. 6 by feeding one or two reactants at multiple injection points along the flow path of the reaction medium to make one or two Each reactant was gradually fed into the reaction. In the energy recovery system 58, various heat recovery methods are performed to improve the energy efficiency of the method. For example, high-pressure steam produced by water passing through conduit 80 may be superheated in a heating furnace supplying flammable fuel and the superheated steam may then pass through one or more steam condensation turbine sections to obtain power. Part of the high-pressure vapor can be transferred for preheating the reactants (heat exchangers 40, 40A, and 40B) or for preheating the stream 82, which is necessary for high thermal efficiency of the system. The condensate recovered from the turbine section and the heat exchangers 40, 40A and 40B can then pass through a series of heating stages to preheat the water for circulation to the reactor 46 via the heat exchanger 52 to form a make-up water that can be added if necessary Closed loop. The heating stage typically contains a series of heat exchangers, whereby the temperature of the circulating water flowing back to the reactor 46 can be gradually increased. In some heating stages, the heating fluid may consist of flashing vapors at different pressures and temperatures from different stages of the crystallization train. In other heating stages, the heating fluid may be a combustion gas from a heating furnace chimney, which is related to a heating furnace for superheating the high-pressure steam supplied through line 84. The embodiment of FIG. 7 uses pure oxygen as the oxidant in essence. Fig. 8 illustrates a specific embodiment similar to that of Fig. 7, but using compressed air (which may be rich in oxygen) as the oxidant. The specific embodiment of FIG. 8 is generally similar to that of FIG. 7, and those parts with the same functions are shown in the two figures with the same number. -29- This paper size applies to the Chinese National Standard (CNS) A4 specification (210 X 297 male) (Centi) 593259 A7 _____ B7_ V. Description of the invention (27) The description of the invention will not be further described unless necessary. As shown, the air supply 100 is supplied via an air compressor 102. As a result of the use of air, a large amount of nitrogen is fed into the method, so it must be appropriately treated in this example. Lower temperatures condense more water than the embodiment of FIG. 7 to reduce the water content of the top product. As shown in Fig. 7, the temperature of the product stream passing through the heat exchangers 50 and 52 is controlled so that the precipitation of product 4 occurs only in the quenching chamber 103. The top product stream is supplied to the gas turbine Π0 via a line 104, a thermal parent converter 106, and a fuel heater 108. The Ding Shao product stream passes through the heat exchanger 106 in order to transfer heat to the mother liquor circulation stream and further discharge water, which can be sent to the product recovery zone 62 via line 12 for use as washing water, for example. For energy efficiency reasons, it is desirable to heat the gaseous top product stream to homogeneous / isolated before feeding into the turbine 110. This is the reason for heating the top product stream by the heater 108. It may have more than one turbine stage, in which case the top product stream upstream of each turbine stage will be heated to an elevated temperature. Line 114 depicts the top product stream leaving the turbine 110 at low pressure and temperature. When the oxidation process results in the formation of components such as carbon monoxide which are undesirable for reasons such as erosion and / or environmental reasons, the top product stream must be treated to reduce / remove this before or after passing through the full turbine 110 and / or venting ingredient. This treatment may include subjecting the overhead product stream to catalytic combustion and / or washing with a suitable reagent such as an alkaline scrubbing solution. The turbine 1 can be mechanically combined with an air compressor so that the latter is driven by the turbine base. In the specific embodiment of FIG. 8, the water system leaves the system through the top product stream. -30- This paper size applies Chinese National Standard (CNS) A4 specifications (210X 297 mm) 593259 A7 B7 V. Description of the invention (3Q) area Downstream from the reactor, a temperature gradient of about 100 ° C here occurs over a length of about 5 cm before the zone of the mixer used to add the NaOH solution, and stainless steel is used for other components. All corrosion-prone conduits are protected. Before each test, the unit was subjected to a hydrostatic test of cooling and heating with pure water (5-10 ml per minute). Once the operating temperature was reached, 〇2 was fed and pumping of para-xylene, MnBr2 and NaOH was started. Typically, the experiment runs for 4-5 hours. The product is usually collected and analyzed during the subsequent 30-60 minutes. The weighing part of the product solution containing sodium terephthalate is acidified with 2N HC1 (in addition, H2S044HN03 can also be used) to precipitate TA and other ingredients. TA is filtered using a Buckner funnel, washed with cold water, air-dried on a dry silicone gel, and weighed. Purity is mainly checked by HPLC. The yield of collected solid product is calculated as the percentage of total paraxylene pumped into the unit to convert to TA. The results in Table 1 show that the high selectivity of the oxidation of para-xylene to terephthalic acid (TA) can be achieved according to the conditions, mixing and concentration of each reactant. Yield is highly sensitive to a range of variables, including paraxylene: 〇2, reactor residence time, paraxylene: catalyst and reactor temperature. The paraxylene oxidation intermediates were analyzed to be 4-carboxybenzaldehyde (4-CBA) and p-toluic acid (p-Tol). In addition, by-products were also measured, including 2,6 dicarboxy 9-fluorenone (DCF), isophthalic acid (IPA), benzoic acid (BA), benzene 1, 2, 4 tricarboxylic acid (TMA), 2 2,4,5-tricarboxydiphenyl (BPTC), biphenyl acid, 4,4 · -dicarboxybenzophenone (DCBBP), 2,6 dicarboxy 9-one ketone, 2,6 dicarboxy anthracene , 2,6 dicarboxyfluorene and 2,6 dicarboxyanthracene. -33- This paper size is in accordance with Chinese National Standard (CNS) A4 specification (210 X 297 mm) 593259 A7 _B7 _._ V. Description of the invention (31) HPLC analysis is performed by injecting the obtained solution directly into the tube. Use a gradient of solvent acetonitrile (16.7%) and buffer (83.3 to 60% and back to 83.3%). The raw material buffer was prepared by dissolving 15 g of anhydrous sodium acetate in 250 ml of deionized water before adding acetic acid (50%, 100 ml). Before dilution to 500 ml, adjust pH to 3.9 ± 0.01 with 5% acetic acid. The diluted buffer was prepared by diluting 30 ml of the raw material buffer with deionized water to 500 ml. The injection volume containing the needle wash is 1 ml. A Waters Xterra reversible phase tube maintained at 40 ° C was used. Use a flow rate of 0.7 ml / min and run for 14 minutes. A 230 micron UV detector is used to analyze the wave peaks. Example 1 Using 100 volumes of hydrogen peroxide, a diluted raw material solution was prepared using 56 ml of peroxide and 760 ml of ultrapure water (18.3 million ohm impedance). The diluted catalyst raw material solution was prepared by dissolving manganese bromide in ultrapure water to a Br concentration of 5000 ppm w / w. Para-xylene is separated and undiluted. The raw solution of sodium hydroxide (0.5M) was prepared for feeding downstream of the reactor, but before the back pressure regulator. Deionized water is pumped separately through the preheater, mixing element, reactor, caustic mixer, cooler, and back pressure regulator at a rate to control the final residence time through the reactor to 65 seconds. The residence time is defined as the volume of the tubular reactors, lines, and fittings between the mixing elements divided by the volume flow. The first is used to mix the reactants to start the reaction and the second is used to add sodium hydroxide to inhibit the reaction. Volume flow is measured based on the physical properties of water under mixed conditions, as published by the American Institute of International Standards and Technology -34- This paper size applies to China National Standard (CNS) Α4 size (210 X 297 mm) binding

Line 593259 A7 B7 V. International Vapor Table of Invention Description (32). The back pressure regulator was set to control the reactor pressure at 250 bar. The heater was set to control the mixing element at 385 ° C and the reactor at 400 ° C. Each reactant was separately pumped to the mixing element as shown in FIG. 9. Paraxylene is fed into the reactor at a concentration of 0.58% w / w, oxygen is fed in a chemical amount close to the amount required for the oxidation of paraxylene to terephthalic acid, and the catalyst solution is fed into the mixing element to produce a reaction. Br concentration of 1632 ppm in the device. After reaching the stable setpoint conditions, samples were collected at intervals of 30 to 60 minutes and subsequently analyzed. This experiment was performed for 3.5 hours. The results showed that the solid yield of the collected samples varied between 26 and 3 7% w / w. The TA composition of each sample changed slightly and paraxylene oxidation intermediates could be found in each sample. The results are collated in Table 1. Example 2 An experiment was performed to test the effect of increasing the reactor residence time, as in Example 1, at a reactor temperature of 250 bar and 400 ° C, but using a reactor residence time of 130 seconds and a slightly increased oxygen flow rate. This results in a reduced yield of TA from 9.3 to 21.3% and poor selectivity. P-xylene oxidation intermediates are reduced and reaction by-products are reduced. Produces higher concentrations of benzoic acid. -35- This paper size is in accordance with Chinese National Standard (CNS) A4 specification (210 X 297 mm) 593259 A7 B7 V. Description of invention (33) Table 1 Experimental conditions and results + finishing experimental reactor conditions Feeding solid products results retention PT pX 〇2 Oxidation TA 4-CBA p-Tol BA Side time ++ + Chemical production rate min ec%% Ppm%%%%%% 1 1.09 250 400 0.58 87-93 1632 26-37 12.9- 8.0 -22.4 14.4- 1.4- 1.1-2.9 25.5 40.8 5.2 2 2.17 250 400 0.58 111 1632 13-30 9.3- 0-1.6 5.9- 4.9- 0-0.9 21.3 12.0 7.9 3 2.08 250 350 0.7 120 975 45-61 45.3- 3.2 6.58- 6.2- 0 61.2 17.6 9.8 4 12.8 250 300 0.58 149 537 0 0.1- 0 0 0 0.1 0.4 5 12.8 250 250 0.58 149 537 0 0-0.3 0 0-0.14 0 0.2-1.2 6 11.7 250 200 0.58 149 537 0 0 0 0-13.9 0 0-1.2 7 0.54 250 400 0.58 115 1632 71 51.9- 0 0-5.95 5.9- 0-1.6 63.8 11.8 8 2.42 250 300 0.58 45 1632 13-98 13.0- 8.5-11.5 35.4- 2.4- 4.30 .6 26.4 64.1 3.7 9 2.43 250 300 0.58 178 1632 42-81 71.6- 0 0 4.9 -0 81.8 7.1 10 0.3 250 400 0.58 120 1640 72-100 91.8- 0 0 5.8- 0 * 94.1 8.2 11 0.3 250 400 1.5 180 1640 69-95 92.1- 0 0 6.3- 0 * 93.8 8.0 12 0.15 250 400 1.5 180 1640 74-90 93.5- 0 0 4.7- 0 * 95.3 6.5 13 0.15 250 400 2 120 1640 79-85 93.9- 0 0 4.9- 0 * 95.1 6.1 ++ The concentration of p-xylene in the reactor + PX is all converted into TA Proportion of chemical amount * Temperature at the mixing element -36- This paper size applies Chinese National Standard (CNS) A4 specification (210 X 297 mm) 593259 A7 _B7__ V. Description of the invention (34) Example 3 Perform an experiment to test The temperature reduction was as in Example 1 at a reactor temperature of 250 bar, 3 50 ° C and a reactor residence time of 125 seconds. The slightly reduced catalyst concentration and increased oxygen amount of 975 ppm Br resulted in an important yield improvement for selectivity among TAs. Although subcritical conditions for water, these results show similar results to the supercritical ones in Example 1. Compared with Example 2, the by-product system was further reduced. Example 4 As in Example 3, experiments were performed at 250 bar and 300X: reactor temperature to evaluate the effect of subcritical temperature. Using 53.7 ppm Br to reduce the catalyst concentration and despite increasing the relative oxygen concentration and extending the reactor residence time to more than 11 minutes, no solid products were generated from the normal inspection of the sample. The analysis showed that only a small amount of para-xylene was converted. Example 5 An experiment was performed as in Example 4, but the reactor temperature was reduced to a temperature of 250 ° C and 250 bar. As in Example 4, no solid product was produced from normal inspection of the sample. The analysis results showed that only a small amount of para-xylene was converted. Example 6 An experiment was performed as in Example 5, but the reactor temperature was lowered to a temperature of 200 ° C and 250 bar. As in Examples 4 and 5, no solid product was generated from normal inspection of the sample. The analysis results showed that only a small amount of para-xylene was converted. Example 7 An experiment was conducted to investigate the effect of the residence time of the reactor. As in Example 1, the reactor temperature at 250 bar and 400 ° C and the estimated reactor residence time of 32 seconds-37- This paper standard is applicable to the Chinese National Standard (CNS ) A4 size (210 X 297 mm)

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593259 A7 _B7__ V.-Description of the invention (35) Time. With an oxidative amount greater than that required for the full conversion of para-xylene, an increase in the yield of solid products and a relative increase in the selectivity of TA are obtained due to the decrease in 4-CBA, p-Tol, and by-products produced . The increase in BA production seems to follow the increase in TA selectivity. Example 8 An experiment was conducted to investigate the effects of reactor residence time, oxidative metering, and catalyst concentration. As in Example 4, the reactor temperature (changed between 296 and 324 ° C) at 250 bar, 300 ° C, and about 145 seconds Reactor retention time. Use reduced oxygen and subcritical temperatures for water. A catalyst concentration of 1632 ppm Br was used to improve the degree of reaction, but a low conversion rate and equal selectivity to TA were obtained. The analysis found all oxidation intermediates and by-products, showing that sufficient catalyst in the reactor must be maintained to promote the selective oxidation of xylene. Example 9 An experiment was performed to determine the effect of oxidative metering, as in Example 8, at a reactor temperature of 250 bar, 300 ° C and a reactor residence time of about 145 seconds. The use of significantly higher oxygen concentrations than those required for the full conversion of para-xylene to TA. The mixing element was maintained at 378 ° C, but the reactor temperature was subcritical for water. A catalyst concentration of 1632 ppm Br was used. Analysis of the products showed good selectivity to TA and no para-xylene oxidation intermediates or by-products were found. The significant concentration of benzoic acid is the only other component found in the solid product. The results illustrate the need to maintain the oxidative metrology of all p-xylene oxidation. Example 10 An experiment was performed, as in Example 1, at a reactor temperature of 250 bar and 400 ° C, and a reduced reactor residence time estimated to be about 20 seconds. Reduced Retention of the Reactor-38- This paper size is in accordance with Chinese National Standard (CNS) A4 (210 X 297 mm) 593259 A7 _B7 _._ V. Description of the invention (36) Time is by using a shorter length of catheter, and Non-coiled heated tubing to achieve. An oxygen concentration greater than that required for the total conversion of para-xylene to TA was used and a catalyst concentration of 1640 ppm Br was used. Analysis of the product showed good selectivity to TA and no para-xylene oxidation intermediates or by-products were found. High concentrations of benzoic acid corresponding to the selective loss of TA are present in the solid product. Compared with Example 9, the results show that with a short reactor residence time, a small amount of oxygen excess is needed to produce high TA yield and selectivity. Example 11 An experiment was performed, as in Example 10, at a reactor of 250 bar and 400 ° C. Increased paraxylene concentration and a high stoichiometric excess of oxygen are fed into the mixing element. A catalyst concentration of 1640 ppm Br was used. The isolated sample was collected for 15 minutes and analysis of the product showed similar selectivity to TA and no paraxylene oxidation intermediates or by-products. Benzoic acid was again the only other component found, but in a smaller amount compared to Example 10. Example 12 An experiment was performed, as in Example 10, at a reactor temperature of 250 bar and 400 ° C, and an estimated reactor residence time of about 10 seconds. A shorter reactor residence time is achieved by using an increased reactant flow rate. Analysis of the products showed high selectivity for TA. Compared to Example 10, a slightly lower benzoic acid concentration was found in the solid product, probably due to the lower reactor residence time. No para-xylene oxidation intermediates or other by-products were measured in the solid product. Example 13 Due to the limitation of the reactor temperature control due to the highly exothermic reaction, the paper size is based on the Chinese National Standard (CNS) A4 specification (210X 297 mm)

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Claims (1)

State 259 A8 B8 C8 D8 τ ^ 'ί ^ ο H i) C J'k Nian Nai e No. 4 patent application case application, ~ 1 profit scope replacement (December 1992) Patent scope of application • One for = A method for producing a group carboxylic acid, which comprises contacting one or more aromatic carboxylic acid precursors with an oxidant in a continuous flow reactor in the presence of a catalyst, and the contact is that the precursor and the oxidant are contained in a supercritical condition Or near the supercritical point in an aqueous solvent of water under near supercritical conditions, so that the one or more precursors, oxidants and aqueous solvents can form a substantially homogeneous homogeneous phase in the anti-j zone, at least part of which The contact of the 'J body with the oxidant for the month is simultaneous with the contact of the catalyst with the at least part of the oxidant. 2. The method according to item 1 of the scope of patent application, wherein the contact of the precursor in the reaction zone is very rapid, defined as the retention time of the reactor volume divided by the reactant volume flow rate under operating conditions is less than 4 minutes. 3. The method according to item 2 of the scope of patent application, wherein essentially all the aromatic carboxylic acids produced are maintained in solution during the reaction. 4. The method according to item 3 of the scope of patent application, wherein after the reaction, the aromatic carboxylic acid is precipitated from the reaction medium and contains not more than 5000 ppm by weight of aldehyde produced during the reaction. 5. The method according to item 4 of the patent application, wherein the reaction heat is removed from the reaction by heat exchange with a heated fluid. 6. The method according to item 5 of the scope of the patent application, wherein the heated flow system passes at least partially surrounding one or more flow channels of the reaction zone. Ί · A method according to item 5 of the scope of the patent application, wherein the heated flow system passes through one or more flow channels having heat exchange walls, and its external surface is exposed to the reaction medium in the reaction zone. 8. The method according to item 7 of the scope of patent application, in which the heat flow system and the flow through the paper are suitable for national g (CNS) A4 specifications (21〇 \ 297 public directors) 593259 The medium in the reaction zone passes through the reaction zone in the opposite direction and / or in the same direction. 9. = The method of claim 8 in which the heated fluid is treated after heat exchange with the reaction to obtain heat, machinery, and / or electricity. 10. A method according to item 9 of the patent application, wherein the heated flow system contains water and / or steam. 11. A method according to claim W, wherein the oxidant is fed into the reaction at two or more locations. 12. The method according to item 4 of the scope of patent application, wherein the precipitate is separated from the mother liquor. 13. The method according to item 12 of the scope of patent application, wherein at least part of the mother liquor is recycled to the reaction zone. 14. The method according to item 13 of the scope of patent application, wherein the mother liquor is heat exchanged with the product stream from the reaction zone for preheating before being recycled back to the reaction zone. 15. The method according to item 丨 of the patent application, wherein the oxidation reaction is performed in more than one reaction zone. 16. The method according to item 2 of the patent application, wherein the oxidation reaction is performed in more than one reaction zone. -2- This paper size applies to China National Standard (CNS) A4 (210X297 mm) 593259 Patent Application No. 090117721 Chinese Graphical Replacement Page (December 1992) Revised 12 · 24 jE Year Q Supplement I