WO2009135384A1 - 一种精间苯二甲酸的制造方法 - Google Patents

一种精间苯二甲酸的制造方法 Download PDF

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Publication number
WO2009135384A1
WO2009135384A1 PCT/CN2009/000486 CN2009000486W WO2009135384A1 WO 2009135384 A1 WO2009135384 A1 WO 2009135384A1 CN 2009000486 W CN2009000486 W CN 2009000486W WO 2009135384 A1 WO2009135384 A1 WO 2009135384A1
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reactor
reaction
oxidation
water
solvent
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PCT/CN2009/000486
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English (en)
French (fr)
Inventor
周向进
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Zhou Xiangjin
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Publication of WO2009135384A1 publication Critical patent/WO2009135384A1/zh

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    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C51/00Preparation of carboxylic acids or their salts, halides or anhydrides
    • C07C51/16Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
    • C07C51/21Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
    • C07C51/255Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting
    • C07C51/265Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting having alkyl side chains which are oxidised to carboxyl groups

Definitions

  • the invention belongs to the field of petrochemical industry and is a new manufacturing method of petrochemical products.
  • Refined isophthalic acid meaning high purity isophthalic acid.
  • the refined isophthalic acid product is a polyester raw material.
  • Polyethylene isophthalate obtained by esterification and polycondensation of terephthalic acid with ethylene glycol is a low-ruthenium polyester having a melting point of 65 °C.
  • the refined isophthalic acid can be mixed with purified terephthalic acid (PTA) and esterified and polycondensed with ethylene glycol to produce a polyester resin for bottles.
  • PTA purified terephthalic acid
  • the low-melting point polyester resin with different melting points can be obtained by mixing the refined isophthalic acid (PIA) with the purified terephthalic acid (PTA) in different proportions, and then esterifying and polycondensing with ethylene glycol.
  • the mixture of purified isophthalic acid (PIA) and purified terephthalic acid (PTA) 1: 1 and then esterified with ethylene glycol, polycondensed polyethylene glycol phthalate has a melting point of 120 ° C .
  • the refined isophthalic acid products are currently produced only by Yanshan Petrochemical Company.
  • the main impurities in the products are 3-carboxybenzaldehyde (meta-carboxybenzaldehyde, 3-CBA) and 3-methylbenzoic acid (metamethylbenzene).
  • 3-CBA 3-carboxybenzaldehyde
  • 3-methylbenzoic acid metalamethylbenzene
  • Formic acid The content of 3-CBA in refined isophthalic acid (PIA) is generally less than 25 ppm, and the content of meta-methylbenzoic acid is less than 150 ppm.
  • the refined isophthalic acid is made of meta-xylene, and the oxygen in compressed air or other oxygen-containing gas (such as oxygen) is used as an auxiliary material, acetic acid is used as a solvent, and cobalt acetate is used.
  • Manganese acetate is used as a catalyst, and hydrobromic acid is used as a co-catalyst to carry out mixed oxidation reaction under relatively mild temperature conditions.
  • raw materials, target products, intermediate products, solvents, and the like are simultaneously present.
  • 3-CBA forms co-crystals with isophthalic acid, so that it is encapsulated inside the crystal grains and cannot be further oxidized.
  • the crude isophthalic acid is obtained by a process such as oxidation reaction, crystallization of isophthalic acid, separation, and drying.
  • the crude isophthalic acid contains a large amount of meta-carboxybenzaldehyde (3-CBA) and m-methylbenzoic acid impurities, which cannot be used as a qualified product, and must be removed by a purification process.
  • the refining process is such that crude isophthalic acid is dissolved in hot water under high temperature and high pressure conditions, sent to a hydrogenation reactor, and subjected to a hydrogenation reaction under the action of a palladium-carbon catalyst to form a meta-carboxybenzaldehyde (3- Reduction of CBA) to meta-methylbenzoic acid.
  • the solubility of m-methylbenzoic acid in water is much higher than that of isophthalic acid, and the separation of isophthalic acid and meta-methylbenzoic acid is basically achieved by recrystallization of aqueous solution of terephthalic acid.
  • Crystalline of isophthalic acid After centrifugation and filtration, a filter cake is obtained, which is dried, washed with water, centrifuged, filtered, and dried to obtain a purified isophthalic acid (PIA) product.
  • PIA isophthalic acid
  • the remaining meta-methylbenzoic acid and a small amount of isophthalic acid remaining in the aqueous solution are concentrated and dehydrated and returned to the oxidation reactor.
  • the hydrotreating process in the PIA production process consumes a large amount of heat energy, and its fuel power consumption accounts for about the total energy of the PIA production. More than half of the consumption.
  • the current oxidation reactors are mainly in two forms, one is a gas-liquid-solid three-phase stirred tank reactor; the other is a bubble column slurry reactor.
  • the liquid phase temperature of the oxidation reactor in the production of refined isophthalic acid (PIA) is generally controlled at 170 to 220 °C.
  • the organic solvent acetic acid and the target product isophthalic acid have a relatively long residence time in the reactor, and the xylene consumption and the solvent acetic acid consumption between the raw materials are relatively high.
  • the present invention seeks to reduce the temperature of the reaction environment in which the acetic acid solvent is located, and to shorten the residence time of the acetic acid and the target product isophthalic acid in the reactor, so that the xylene consumption and the solvent acetic acid consumption of the raw materials are relatively low.
  • meta-xylene to isophthalic acid is a series reaction, mainly through four reaction processes, one is from meta-xylene to meta-methylbenzaldehyde; the other is from meta-methyl Benzaldehyde to m-methylbenzoic acid; third is from meta-methylbenzoic acid to meta-carboxybenzaldehyde (3-CBA); fourth is from meta-carboxybenzaldehyde to isophthalic acid. All four oxidation reactions are irreversible.
  • the withdrawal of the oxidation reaction heat in the oxidation reactor is mainly carried out by flashing of the solvent acetic acid and water.
  • the flashed acetic acid and water enter the condensing system with the exhaust gas. After heat exchange, part of the condensate enters the reactor. Most of the acetic acid and water are recycled into their respective storage tanks. Part of the recovered acetic acid and water are added to the reactor.
  • the invention controls the reaction conditions through a newly designed reaction process, so that the liquid phase of the reactants is free of 3-CBA and meta-methylbenzoic acid when the isophthalic acid crystallizes, thereby simplifying the production process, reducing the production cost, and improving the product quality.
  • the quality of the isophthalic acid product produced by the method of the present invention exceeds the quality of the current PIA product, and the content of 3-CBA and meta-methylbenzoic acid can reach zero.
  • This product can be called spermatophthalic acid, and the English is sketched as PPIA.
  • This refined isophthalic acid (PPIA) product is more suitable as a polymer raw material for food packaging materials, beverage bottle materials, pharmaceutical packaging materials, and medical equipment because it has a very low formaldehyde content and is safer and more toxic. Superiority.
  • the consumption index of the meta-xylene raw material and the acetic acid solvent will be further reduced when the technique of the present invention is employed.
  • the invention adopts the technology of the invention to produce refined isophthalic acid, omitting the hydrofining process, saving equipment investment; reducing the combustion energy consumption by about 50%, and saving about 100% of the comprehensive energy consumption per ton of the refined isophthalic acid product (excluding raw materials) Kilograms of standard crude oil; avoid the use of expensive palladium-carbon catalysts; product quality is improved.
  • the present invention is in line with the current production process technology under the condition that the crude oil price is 110 USD/barrel and the exchange rate of RMB to US dollar is 7:1. Compared with the production cost of refined isophthalic acid, it can save 500 ⁇ 1000 yuan/ton. Summary of the invention
  • the novel production process of the invention comprises dioxane oxidation reaction, crystallization of isophthalic acid, separation, filtration and drying; (if necessary, adding acetic acid to the isophthalic acid crystal to remove cobalt, manganese ion catalyst, and then separating, Filtration, drying); Isophthalic acid crystals are washed, separated, filtered, dried, and composed of catalyst recovery, solvent recovery and tail gas treatment.
  • the first "drying" process for the purpose of removing the organic solvent acetic acid can be omitted.
  • the second "dry” process for removing the organic solvent acetic acid can be omitted.
  • the oxidation reaction uses meta-xylene as the main raw material, and oxygen or other oxygen-containing gas (such as oxygen) in compressed air or other oxygen-containing gas (such as oxygen) as auxiliary materials, acetic acid as the initial solvent, cobalt acetate and manganese acetate.
  • oxygen or other oxygen-containing gas such as oxygen
  • compressed air or other oxygen-containing gas such as oxygen
  • acetic acid as the initial solvent
  • cobalt acetate and manganese acetate acetic acid
  • cobalt acetate and manganese acetate cobalt acetate and manganese acetate.
  • hydrobromic acid is used as a co-catalyst, and the oxidation reaction is carried out under the temperature conditions varying with the reaction scheme.
  • Water is used as an auxiliary solvent in the later stage of the oxidation reaction.
  • the oxidation reaction is divided into two main regions, from meta-xylene to meta-methylbenzoic acid and from meta-methylbenzoic acid to isophthalic acid.
  • the temperature and pressure of the two zones may be different, or the temperature may be the same and the pressure is the same, depending on the choice of the reactor structure.
  • the new meta-xylene oxidation process is used to make the intermediate product obtained from the oxidation reaction crude isophthalic acid (crystal) free of the main impurities inevitable in the current production process: 3-carboxybenzaldehyde (3-CBA) and meta-position Methyl benzoic acid, omitting the "refined” production process established to eliminate these two impurities, reducing raw material consumption and acetic acid solvent consumption, reducing fuel power consumption, reducing water consumption, improving product quality, and avoiding the use of expensive palladium - Carbon catalysts, thereby saving production costs.
  • 3-carboxybenzaldehyde 3-carboxybenzaldehyde
  • Methyl benzoic acid omitting the "refined” production process established to eliminate these two impurities, reducing raw material consumption and acetic acid solvent consumption, reducing fuel power consumption, reducing water consumption, improving product quality, and avoiding the use of expensive palladium - Carbon catalysts, thereby saving production costs.
  • the desired state of the stream is such that the stream is formed in an upstream and downstream relationship in accordance with the various steps of the reaction from m-xylene to isophthalic acid.
  • the oxidation reaction in the stream is carried out in the order of the series reaction.
  • the present invention designs a reaction flow similar to a flat push flow or a plug flow or a partial reaction flow similar to a flat push flow or a plug flow, so that the internal liquid phase flow of the reactor exists in an upstream and downstream relationship.
  • the effective separation of the outlet region of the target oxidation product isophthalic acid and the xylene feed port region between the raw materials is not completely closed in space, but the materials in the two regions are not directly in the process of the reaction. Mix with each other.
  • the oxidation reaction proceeds substantially in the order from m-xylene to isophthalic acid series reaction, that is, the newly added raw material xylene entering the reactor does not enter the series reaction.
  • the oxime concentration region of isophthalic acid which is the target product of the oxidation reaction, is not mixed with xylene between the reaction raw materials.
  • the exit region of the final isophthalic acid solution is not mixed with the xylene and the various oxidation reaction intermediates between the reaction materials.
  • N2009/000486 The essence of this new oxidation reaction process is to carry out the four main reactions of the series oxidation reaction, that is, segmental oxidation, so that the corresponding reaction conditions can be separately controlled for the physical properties of the organic raw material phase in each reaction stage. .
  • the supplementary solvent is added in sections, the ratio of acetic acid to water in the mixed solvent is different according to different replenishing positions, and the ratio of water in the mixed solvent is from 0 to 100%;
  • the concentration of the solution is controlled in stages, the concentration of the reactant is 5 to 50%, and the typical reactant concentration is 28%;
  • This segmentation is not a categorical segmentation but a relative segmentation. That is: in the reactor, meta-xylene, m-methylbenzaldehyde, m-methylbenzoic acid, meta-carboxybenzaldehyde, isophthalic acid, etc. have obvious high concentration regions, and there is concentration between high concentration regions. In the transition zone, high concentration zones occur in the order of tandem oxidation reactions.
  • the main target oxidation product is meta-methylbenzoic acid, and only cobalt acetate and manganese citrate catalyst are added to the raw materials and solvent.
  • hydrobromic acid is added as a co-catalyst, and water is used as an auxiliary solvent.
  • This fractional oxidation reaction can be carried out between several reactors or within one reactor.
  • the present invention designs an oxidation reactor having an inner and outer chamber structure, and uses a built-in cylinder concentric with the reactor to divide the reactor into two chambers, inner and outer, the bottom of the cylinder and the bottom of the inner wall of the reactor. Connected, the upper side of the cylinder is submerged under the liquid material level, and the inner and outer chamber pants material is connected on the cylinder.
  • the mixed reaction materials include raw materials, solvents, catalysts, etc., which are fed from the bottom of the inner chamber, and the inner chamber materials are ascended, entering the outer chamber from the top of the liquid phase, and the outer material is descending.
  • the material is in a section similar to the flat flow, and the oxidation reaction proceeds substantially in the order of the series oxidation reaction.
  • the liquid reaction material forms an upstream and downstream relationship between the inner chamber and the outer chamber.
  • the chambers are in gas communication, facilitating the withdrawal of heat of reaction from the interior of the reactor by solvent flashing.
  • the feed port position can be placed at the bottom of the outer chamber and the discharge port position can be placed at the bottom of the inner chamber.
  • the present invention designs an oxidation reactor having an internal, intermediate and external three-chamber structure, and uses two built-in cylinders concentric with the reactor to divide the reactor into three chambers, one cylinder inside and outside, one cylinder
  • the bottom is connected to the bottom of the inner wall of the reactor, the upper side of the cylinder is submerged under the liquid level of the liquid material, the liquid material is connected on the upper side of the cylinder; the other side is suspended below the bottom, and is fixed on the inner side of the bottom of the reactor main body by the point support, the side surface is
  • the inner wall of the reactor or another cylinder forms a support for fixing.
  • the liquid phase is effectively separated on the cylinder, and the liquid material is connected under the cylinder.
  • the material is in a flow section that approximates the flat flow, and the oxidation reaction proceeds substantially in the order of the series oxidation reaction.
  • the liquid reaction materials form an upstream and downstream relationship in the inner chamber, the middle chamber and the outer chamber. Room gas Conversely, it facilitates the withdrawal of heat of reaction from the interior of the reactor by solvent flashing.
  • the feed port position can be placed at the bottom of the outer chamber and the discharge port position can be placed at the bottom of the inner chamber.
  • the present invention can also adopt three, four or even more built-in 4-chamber, 5-chamber, multi-chamber oxidation reactors with a concentric cylindrical chamber of the reactor, and the liquid materials are in the order of the cylinder size.
  • the upper part and the lower part of the cylinder are respectively connected with the adjacent chamber to effectively separate the raw material feed port and the reaction material discharge port, thereby effectively forming the upstream and downstream relationship of the liquid material flow; each chamber is in gas phase communication, which is favorable for solvent flashing from the reactor.
  • the reaction heat is withdrawn internally.
  • the invention designs a horizontal flat push flow oxidation reactor.
  • the material is in a process similar to the flat push flow, and the liquid reaction material forms an upstream and downstream relationship, and the oxidation reaction is basically in accordance with the series oxidation reaction.
  • the order is carried out.
  • the material is slowly propelled by the spiral propeller shaft, and the material flow direction is the same as that of the propulsion shaft, which is beneficial to the small amount of isophthalic acid crystals generated during the reaction being pushed to the high temperature section for dissolution, and the spiral propeller shaft can be dynamically divided.
  • the function is to reduce the convection between the low temperature section material and the high temperature section material due to the temperature difference.
  • the present invention designs a tower plug flow oxidation reactor in which the material is in a flow similar to that of the plug flow, and the oxidation reaction proceeds substantially in the order of the series oxidation reaction.
  • the present invention designs a combination of oxidation reactors in which multiple reactors are connected in series.
  • the reaction materials have an upstream and downstream relationship, and the local materials are in a flow similar to the flat flow, and the oxidation reaction is basically in series. The order of the oxidation reaction proceeds.
  • Compressed air or other oxygen-containing gas such as oxygen
  • compressed air or other oxygen-containing gas such as oxygen
  • annular air distributor An annular air distributor.
  • the total air flow is set based on the metaxylene flow rate and the reactor off-gas oxygen concentration to ensure that the exhaust gas exits the reactor off-gas cooler with an oxygen concentration of 3 to 4% or less.
  • Compressed air or other oxygen-containing gas can be supplied according to the liquid phase volume, or it can be supplied with uneven gas.
  • an annular air distributor is used to supply air from the bottom, and compressed air or other oxygen-containing gas (such as oxygen) can be designed to be supplied excessively.
  • the liquid phase oxygen concentration is relatively high, used for oxidizing meta-methylbenzoic acid, increasing the reaction rate from meta-methylbenzoic acid to 3-CBA, and the speed of the entire series oxidation reaction is thus accelerated, and the solvent consumption is thus reduced.
  • the production capacity per unit volume increases.
  • an oxidation reactor having an internal and external chamber structure
  • an external chamber unit liquid phase volume compressed air or other oxygen-containing gas for example, oxygen
  • oxygen-containing gas for example, oxygen
  • excess compressed air or other oxygen-containing gas such as oxygen
  • excess air is beneficial to increase the oxidation of the area. Should be speed.
  • excess air will not cause safety problems, because excess air only exists in the lower part of the outer chamber. When it reaches the middle part, excess air will enter the inner chamber through the braided grid, and will fully mix with the inner chamber liquid phase to participate in the internal chamber oxidation reaction. Therefore, the oxygen content in the exhaust gas is not increased because the oxygen in the compressed air or other oxygen-containing gas (such as oxygen) is not fully utilized, resulting in wasted resources of compressed air or other oxygen-containing gas (such as oxygen).
  • Controlling the flow of meta-xylene, compressed air or other oxygen-containing gas (such as oxygen) entering the oxidation reactor ensures that there is no meta-carboxybenzaldehyde (3-CBA) and no interstitial solution in the isophthalic acid solution discharged from the reactor.
  • Methyl benzoic acid Methyl benzoic acid.
  • the meta-carboxybenzaldehyde (3-CBA) and meta-methylbenzoic acid are completely oxidized to isophthalic acid before reaching the discharge port of the oxidation reactor.
  • an air distributor is used to supply gas at the bottom of the liquid phase.
  • two or more sets of air distributors may be provided, wherein the first group is left at the bottom and the other groups are spaced apart from the first group by a distance.
  • three or four sets of compressed air or other oxygen-containing gas (e.g., oxygen) distributors can be placed in the tower oxidation reactor.
  • the air distributor at the bottom can add a cross in the middle of the ring as an optimized air distributor.
  • Annular compressed air or other oxygen-containing gas (such as oxygen) distributors are centered around the reactor axis, and compressed air or other oxygen-containing gas (such as oxygen) vents are bored in all directions in the radial direction for air or other oxygen-containing gas.
  • the distribution of the body (eg oxygen) is more uniform.
  • a cross-shaped distributor can be added in the middle of the small annular distributor, and the cross is in the same plane as the ring.
  • the liquid level height in the low temperature oxidation region of the liquid phase is increased.
  • Compressed air entering the reactor from the bottom of the liquid phase or other oxygen-containing gas (such as oxygen) the liquid phase reaction material of the tail gas passing through the liquid phase before entering the reactor gas phase is between the fresh reaction materials just entering the oxidation reactor.
  • Toluene, acetic acid solvent, catalyst and auxiliary catalyst mixture under the same temperature and the same material concentration, for example, at a temperature of 130 ⁇ 210 ° C, a typical temperature of 160 , the material in this area is the most easily oxidized material, oxidation
  • the activation energy required for the reaction is relatively low, and it can react with the low concentration of oxygen remaining in the exhaust gas of compressed air or other oxygen-containing gas (such as oxygen), thereby reducing the oxygen content in the exhaust gas.
  • the tail oxygen content can be controlled from now 3 ⁇ 4% is reduced to 1 ⁇ 2%, or even lower, increasing the utilization of compressed air or other oxygen-containing gases (such as oxygen), the efficiency of air compressors is increased by 10% or even higher.
  • the oxidation reaction conditions are controlled in stages according to different oxidation reactors selected, and the oxidation reaction temperature is 130 ⁇ 210°C, 180 ⁇ 250, respectively. C and 210 to 350 ° C, the typical temperature range is 145 to 288 ° C.
  • the typical low temperature section temperature and pressure are 160 ⁇ and 0. 5 MPaG, respectively.
  • the typical medium temperature section temperature and pressure are 25 (TC and 5. OMPaG, respectively, and the typical high temperature section temperature and pressure are 288 ° C and 7.5 MPaG, respectively.
  • the oxidation reactor pressure corresponds to the saturated vapor pressure of the liquid phase material in the high temperature zone within the reactor.
  • Reactor pressure It is controlled by controlling the amount of intake air of compressed air or other oxygen-containing gas (e.g., oxygen) and the opening of the non-condensing gas outlet regulating valve of the reactor off-gas condensing system.
  • System control takes temperature as a priority and pressure as a secondary factor.
  • Pressure is an element of safety detection and control. For the case where different temperature regions exist in the same reactor, the pressure control is slightly higher than the saturated vapor pressure in the high temperature region, so that the high temperature region does not boil, and the material convection in the high temperature region and the low temperature region is not enhanced.
  • the temperature of the reactor discharge port area can be set at a higher position, for example: 400 to 500 °C. At this time, in the mixed solvent, there is no acetic acid and only water, and the oxidation reaction residence time is shorter.
  • the catalyst cobalt acetate, manganese acetate, and the auxiliary catalyst hydrobromic acid can be combined in various ratios, for example, 1: 1: 1, 1: 2: 3, or 1: 2. 5: 1, and the like.
  • the typical ratio is 1 : 1: 1.
  • the catalyst concentration total mass content of cobalt, manganese, and bromide ions
  • the catalyst concentration is in the range of 300 to 3000 ppm (catalyst/organic raw material phase + solvent), and the typical concentration is 1050 ppm.
  • a conventional catalyst addition method is to add three catalysts and catalyst auxiliaries together with a raw material, a solvent (including a recovered catalyst, a solvent), and to be added to an oxidation reactor.
  • the second is to control the concentration of the catalyst in the reaction material, and gradually reduce the concentration of the catalyst and the auxiliary agent according to each step of the series reaction to form a concentration gradient.
  • the initial catalyst concentration is 1050 ppm and the final reactant outlet catalyst concentration is 0 P pm, reducing catalyst consumption.
  • a typical catalyst concentration profile is from initial 1050 ppm to a final reactant outlet concentration of 600 ppm.
  • the initial solvent is acetic acid and the auxiliary solvent is water.
  • the proportion of acetic acid in the mixed solvent of acetic acid and water is gradually reduced, forming a gradient, and the proportion of water is gradually increased.
  • the proportion of acetic acid was reduced from 100% to 0%.
  • the proportion of water increased from 0% to 100%.
  • a typical solvent gradient is a stepwise reduction in the acetic acid ratio from the initial 95% to 20%.
  • a large amount of water is added to the reactor as a solvent for isophthalic acid and a solvent for 3-CBA and a solvent for m-methylbenzoic acid, so that the target product isophthalic acid obtained by the oxidation reaction can be sufficiently dissolved, and the intermediate product 3-
  • the CBA can also be sufficiently dissolved to be oxidized to isophthalic acid.
  • the solute is a liquid phase organic raw material phase, that is, a raw material and a product which are reacted in series from m-xylene to isophthalic acid. All of its intermediates, the solvent is a mixed solvent of acetic acid and water.
  • the control of the liquid phase concentration of the reactants has four forms depending on the structure of the selected oxidation reactor and the heat removal mode of the oxidation reaction heat.
  • the oxidation reactor is mainly used to remove heat by solvent flashing, so it is necessary to continuously add solvent to the reactor.
  • the composition of the liquid phase material is different, and the composition ratio of the mixed solvent added is also different.
  • the proportion of acetic acid in the mixed solvent added is 100 ⁇ 50%.
  • the proportion of acetic acid in the mixed solvent is also changed in gradient due to the continuous oxidation reaction of the liquid phase to produce by-product water, regardless of the solvent flashing factor.
  • the ratio of acetic acid in the added mixed solvent is 50 to 0% (when conditions are met, especially in the plug flow reactor, the solvent concentration in this region)
  • the ratio of acetic acid is gradually reduced from 50% to 0%, and the proportional gradient is distributed.
  • the typical mixed solvent acetic acid ratio is 20%.
  • the concentration of the solution in the discharge port area of the final oxidation reactor is high, and it is necessary to pay attention to the control concentration not exceeding the saturated solubility of the simple dicarboxylic acid.
  • the oxidation reactor mainly adopts a method of discharging a high temperature and low concentration solution in a large amount at the discharge port to remove heat.
  • a bubble column oxidation reactor the withdrawal heat and temperature balance of the internal reaction of the reactor, and a method of adding a low-temperature solvent to the system, and the temperature of the liquid phase material is stabilized by the heat absorption of the solvent.
  • the concentration of the liquid phase material gradually decreases in the direction of the series reaction.
  • the reaction temperature is lowered in each reaction stage of the reactor, so the temperature is relatively increased, the reaction speed caused by the decrease of the reactant concentration is lowered, the reaction speed is appropriately increased, and the reaction time caused by the shortening of the residence time of the reaction material is compensated. insufficient.
  • a large amount of low-concentration reaction product is discharged from the discharge port into the crystallizer to be flashed, and the heat is recovered to remove the solvent to increase the concentration, and the isophthalic acid is crystallized.
  • add a flash tank between the crystallizer and the reactor which is specially used for solution concentration and heat recovery with heat exchanger. Or before entering the crystallizer, the solution is heat exchanged through the heat exchanger to recover heat, and then the crystallizer is flashed.
  • This method of heat removal is the same as the heat of oxidation that can be recovered by means of flash evaporation and heat removal from the internal solvent of the oxidation reactor. Due to the relatively high temperature at the end of the oxidation reaction, the heat recovered by this method can be used to generate high levels of steam.
  • a method of heat exchange and heat removal by the built-in coil may be employed.
  • the cooling medium flows inside the coil. Since the solubility of isophthalic acid in the solution is temperature sensitive, the cooling coil should not be placed in the high concentration zone of isophthalic acid. If it is to be placed in the high concentration zone of isophthalic acid, the inside of the coil is The difference between the temperature of the medium and the temperature of the solution outside the coil should not be too large, and the external temperature of the coil should not be lower than the concentration of the solution in the region of the reactor as the temperature corresponding to the concentration of the saturated solution. Otherwise, isophthalic acid crystals are formed on the outer surface of the coil.
  • the outer wall of the tower oxidation reactor is wrapped around the tube, and heat is removed by heat transfer using a cooling medium. (4) Mixed use of the above three types of heat removal measures.
  • the oxidation reaction uses meta-xylene as the main raw material, and oxygen or other oxygen-containing gas in compressed air or other oxygen-containing gas (such as oxygen) is used as an auxiliary material, acetic acid is used as the initial solvent, and cobalt acetate and manganese acetate are used as catalysts. Hydrobromic acid is used as a co-catalyst, and water is used as an auxiliary solvent in the later stage of the oxidation reaction.
  • the "organic raw material” or “organic raw material phase” of the present invention means the sum of metaxylene and isophthalic acid and various oxidation reaction intermediates from meta-xylene to isophthalic acid.
  • the reaction temperature is divided into sections of about 130 to 210 ° C and about 180 to 250 ° C, and 210 to 350 ° C, and segmentation control. 0 ⁇
  • the oxidation reaction pressure of the present invention is 0. 5 ⁇ 14. 0MPaG or so.
  • the typical low temperature temperature and pressure are 160 ⁇ and 0.5 MPaG, respectively; the typical medium temperature temperature and pressure are 250 ° C and 5. OMPaG, respectively; the typical high temperature temperature and pressure are 288 ⁇ and 7.5 MPaG, respectively.
  • the temperature is controlled by flashing into the top heat exchanger (condenser) of the reactor, the amount of solvent and water, the reflux of the condensate, the flashing of the crystallizer acetic acid solvent and the water solvent, the temperature of the water and acetic acid that is replenished into the reactor.
  • the reactor pressure is controlled by controlling the amount of compressed air or other oxygen-containing gas (e.g., oxygen) and the opening of the non-condensing outlet regulating valve of the reactor exhaust condensing system. Temperature is the first factor and the pressure is set to match the temperature requirements.
  • oxygen oxygen
  • the m-xylene is mixed with the solvent acetic acid, the catalyst cobalt acetate, the manganese acetate, the auxiliary catalyst hydrobromic acid, and then added to the low temperature section of the oxidation reactor, and oxidized at a temperature of 130 to 210 ° C to mainly form meta-methylbenzoic acid.
  • the temperature balance at this stage uses two methods, one is solvent flashing, and the heat is removed from the condenser at the top of the reactor; the other method is to add a mixed solvent of low-temperature acetic acid and a small amount of water to the reactor. By raising the temperature of the solvent, the heat of reaction is absorbed and the temperature of the reactor is balanced.
  • water is added to the liquid phase of the reactor as a supplementary solvent to control the concentration of isophthalic acid in the solution not to exceed the saturation solubility, and to increase the reaction temperature.
  • Increasing the liquid phase temperature of the reactants and increasing the content of the solvent water are effective measures for increasing the solubility and dissolution of the phthalic acid in the liquid phase of the reactor.
  • the temperature in this zone can be controlled at 210 to 350 ° C, and the preferred temperature range is 246 to 288 ° C.
  • the reaction temperature is 180 to 240 ° C, and the content of water in the solvent is 6 to 50%.
  • the concentration of m-methylbenzoic acid is 1 to 0.1%, the reaction temperature is 250 to 288 ° C, and the content of water in the solvent is 50 to 100%.
  • the reaction temperature rises to 250 to 288 ° C
  • the corresponding saturated solubility of isophthalic acid in aqueous solution is about 3 to 50%
  • high temperature conditions make it possible to increase the concentration of the organic raw material solution (low temperature conditions may Will precipitate crystals). Therefore, in the case of high temperature and high organic material concentration, the proportion of acetic acid in the mixed solvent can be further reduced, the proportion of water in the mixed solvent can be increased, and the concentration of the catalyst and the auxiliary catalyst can be further reduced. Even so, the oxidation reaction can proceed smoothly because increasing the temperature increases the oxidation reaction capacity of the organic raw material.
  • the typical ratio of water in the solvent is 80%; the typical ratio of cobalt to manganese bromine is cobalt: manganese: bromine is 1: 1:1, typical ion concentration (mass ratio) is 600ppn typical isophthalic acid
  • the formic acid concentration isophthalic acid/isophthalic acid + water + acetic acid
  • the typical temperature is 288 °C.
  • the target product of the oxidation reaction isophthalic acid
  • isophthalic acid is effectively separated from m-xylene and other intermediates to avoid the presence of 3-CBA and meta-methylbenzoic acid in the material during the crystallization of isophthalic acid.
  • the loss of raw materials caused by excessive oxidation of the reaction product isophthalic acid due to a long residence time is reduced.
  • the isophthalic acid solution obtained from the oxidation reactor is sent to the crystallizer, and the isophthalic acid is crystallized only in the crystallizer, and a relatively pure isophthalic acid solid is obtained in the crystallizer.
  • the reactor discharge port is preferably located at the bottom of the reactor or at the lower side of the reactor to facilitate the discharge of the crystalline solids from the reactor.
  • the ratio of acetic acid to water varies with the temperature of the reactor zone, and the saturation solubility of isophthalic acid in the mixed solvent of acetic acid and water is also different.
  • the liquidus temperature is 250 to 288 ° C, it is safe to control the concentration of isophthalic acid between 2 and 45%, and the solution does not easily form accidental crystallization.
  • the better temperature and concentration control are: temperature is 286 ⁇ 288°C, and concentration of isophthalic acid solution is 30%.
  • Part of the heat of reaction is withdrawn from the interior of the reactor by flashing of solvent and water, and the condenser at the top of the reactor exchanges heat to recover heat.
  • Part of the heat of reaction is withdrawn by flash evaporation from the crystallization system, and the flashed solvent recovers heat through the heat exchanger.
  • the low temperature water enters the reactor to take heat, and the high temperature water enters the crystallizer to flash, so that heat can be withdrawn.
  • the solvent flash heat removal ratio inside the reactor is greater than the crystallizer solvent flash heat removal, such as an oxidation reactor combination.
  • the solvent solvent flash heat removal ratio is greater than the solvent flash heat removal inside the reactor, such as the tower oxidation reaction similar to the plug flow process.
  • the oxidation reaction step is exemplified by an oxidation reactor having internal, intermediate and external chamber structures:
  • the ratio of the internal and external three-chamber liquid phase volume is within: Medium: Outside 1: 2: 3. Air distributors are provided at the bottoms of the inner, middle and outer chambers. After the raw materials, solvent, and catalyst are mixed, they are fed from the bottom of the inner chamber.
  • the reaction temperature is controlled so that the oxidation reaction is mainly caused by the oxidation of m-xylene to m-methylbenzaldehyde and meta-methylbenzaldehyde to m-methylbenzoic acid.
  • internal temperature conditions such as 155 to 160 ° C
  • the oxidation of m-methylbenzoic acid to meta-carboxybenzaldehyde (3-CBA) is more difficult, especially in the absence of the cocatalyst hydrobromic acid.
  • the temperature balance of the inner chamber is supplemented by adding 30 ⁇ low temperature acetic acid and water mixed solvent to the inner chamber.
  • the inner chamber liquid material and the middle chamber liquid phase are connected in the upper portion of the small cylinder.
  • Auxiliary catalyst hydrobromic acid is added to the middle of the liquid phase with the auxiliary solvent water, a large amount of meta-methylbenzoic acid is oxidized to 3-CBA and 3-CBA is oxidized to isophthalic acid in the middle and outer chambers.
  • the lower part is carried out. Oxidation of a small amount of meta-xylene to meta-methylbenzaldehyde and oxidation of m-methylbenzaldehyde to meta-methylbenzoic acid occur in the lower part of the middle chamber, and the upper part of the outer chamber is actually saturated oxidation of isophthalic acid. Zone, completely eliminate 3-CBA and meta-methylbenzoic acid.
  • the concentration of the organic raw material phase in the middle and outer chambers is lower than the initial feed concentration, and the ratio of water in the solvent is high, so the oxidation reaction rate is stably controlled despite the high temperature.
  • the temperature in the middle and outer chambers is controlled at 288 °C.
  • the heat of reaction between the middle and outer chambers is withdrawn by solvent flashing.
  • the flashed solvent is condensed in a heat exchanger at the top of the reactor to recover heat. Most of the condensate is recovered and sent to a storage tank of acetic acid and water.
  • the reaction material discharge port is arranged in the upper part of the outer chamber, and the final reaction product isophthalic acid solution is discharged from the discharge port and sent to the crystallization system.
  • the reaction speed of the reactor with the inner, middle and outer three-chamber structure of the present invention is accelerated under the premise of the same reactor volume, the overall residence time of the material is shortened, the yield is increased, and the organic raw materials and organic solvents are used. Reduced consumption, reduced fuel and power consumption.
  • crystallization - In the crystallizer, by cooling under reduced pressure, water and acetic acid solvent are continuously flashed, the concentration of isophthalic acid increases and the saturation solubility coefficient decreases with decreasing temperature, and isophthalic acid continuously precipitates from the solution, and the crystal grains gradually increase.
  • the crystallizer is equipped with a stirrer to make the grain size relatively uniform. Since there is no meta-carboxybenzaldehyde (3-CBA) and m-methylbenzoic acid in the solution, the isophthalic acid crystals do not contain meta-carboxybenzaldehyde (3-CBA) and meta-methylbenzoic acid. Impurity.
  • the temperature difference of each stage of the crystallizer is 20 ⁇ 58 °C, and the better temperature difference is 21 ⁇ 38 °C.
  • the final crystallizer temperature is 100 ⁇ 180 °C. The increase in the number of crystal stages is beneficial for recovering high-temperature heat and increasing the grade of by-product steam.
  • the water and acetic acid recovered by the crystallization system enter the reuse system of water and acetic acid, respectively.
  • the isophthalic acid crystals are separated by centrifugation, filtered, dried (without residual acetic acid solvent), then washed with water to remove water-soluble impurities, and then centrifuged, filtered, and dried to obtain a purified isophthalic acid product (PIA) or Refined isophthalic acid product (PPIA).
  • PIA isophthalic acid product
  • PPIA Refined isophthalic acid product
  • the first "drying" step for removing vinegar may be omitted.
  • an oxidation reactor structure or a combination of reactors capable of separating the meta-xylene between the raw materials and the oxidation reaction target product isophthalic acid to establish a staged oxidation or an oxidation process in the order of series reaction, such that xylene is intercalated from the raw material.
  • the reaction material forms an upstream and downstream relationship.
  • acetic acid as initial solvent
  • water as auxiliary solvent
  • cobalt acetate and manganese acetate as catalyst
  • hydrobromic acid as auxiliary catalyst
  • the oxidation reactor or the oxidation reactor is combined, blown into compressed air or other oxygen-containing gas (for example, oxygen) or an oxygen-containing gas, and reacted at a temperature of 130 to 350 ° C for 15 to 150 minutes to obtain an isophthalic acid solution.
  • oxygen-containing gas for example, oxygen
  • the pressure of the reactor is 0. 5 ⁇ 14MPaG.
  • the isophthalic acid solution is cooled by a heat exchanger (recovering heat), concentrated in a flash tank (recovering heat), multi-stage crystallization (recovering heat), separated, filtered, washed, separated, filtered, and dried to obtain a refined benzene.
  • a heat exchanger recovery heat
  • concentrated in a flash tank recovery heat
  • multi-stage crystallization recovery heat
  • the atomic ratio of the total concentration of cobalt and manganese ions to the atomic ratio of bromide ions is 0. 5 ⁇ 2 .
  • An oxidation reactor having an inner and outer chamber structure, wherein the reactor is divided into inner and outer chambers by a cylinder coaxial with the reactor, and the inner and outer chambers are connected at the top of the cylinder, and the cylinder is at the bottom of the outer chamber.
  • the material outlet is effectively separated from the raw material inlet at the bottom of the inner chamber, and the supply volume of the compressed air or other oxygen-containing gas (for example, oxygen) in the liquid phase of the inner and outer chambers is the same; the annular air distributor is used; and the annular water distributor is used.
  • the unit liquid phase volume compressed air or other oxygen containing gas (e.g., oxygen) in the outer chamber is supplied in greater than the inner chamber, and excess compressed air or other oxygen containing gas (e.g., oxygen) enters the inner chamber through the braided grid.
  • oxygen oxygen
  • the inner chamber uses a tree-shaped water distributor.
  • the tree-shaped water distributor is mainly composed of trunks and branches, and the inside of the trunk branches is a passage of water, and the branches are provided with water holes.
  • the trunk can be designed as a tube that takes heat from the liquid reaction material and preheats the water in the trunk.
  • Oxidation reactor with internal, intermediate and external three-chamber structure using two built-in cylinders concentric with the reactor to separate the reactor into three chambers inside and outside, the middle chamber and the outer chamber liquid phase in the large cylinder
  • the lower side of the outer chamber is effectively separated from the upper liquid phase of the middle chamber;
  • the upper part of the middle chamber is connected to the upper part of the inner chamber on the small cylinder, and the lower part of the middle chamber is effectively separated from the raw material inlet of the lower part of the inner chamber;
  • the material outlet is effectively separated from the raw material inlet in the lower part of the inner chamber; an annular air distributor is used; and an annular water distributor is used.
  • the inner chamber uses a tree-shaped water distributor.
  • a horizontal oxidation reactor with a flat flow reaction process in which one end of the reactor feeds and the other end discharges. The liquid phase of the terminal liquid phase and the feed end of the raw material cannot be arbitrarily mixed. From the feed port of the reactor raw material to the discharge port of the reaction material, the oxidation reaction is basically carried out in the order of the series oxidation reaction.
  • a spiral sheet propulsion shaft is used to dynamically divide the liquid phase of the reaction material.
  • the tower oxidation reactor having a reaction flow similar to that of the plug flow is a tower reactor having a long diameter ratio of 6 to 30, and the inner section is provided with annular compressed air or other oxygen-containing gas (for example, oxygen) distributor and ring. Influent distributor. Upper coffin, lower discharge.
  • oxygen-containing gas for example, oxygen
  • a tree-shaped water distributor is used.
  • the combination of two or more reactors in series with the oxidation reactor can make the oxidation reaction material form an upstream and downstream relationship, which is in an approximate flat flow state.
  • Two conventional oxidation reactors can implement a staged oxidation reaction process. More than three conventional oxidation reactors allow the oxidation reaction material to be in a state of approximately flat flow.
  • the use of an "oxidation reactor with internal and external chamber structure" or a “oxidation reactor with internal, intermediate and external three-chamber structure" combined with a conventional oxidation reactor can make the oxidation reaction material close to The flow state is flat, and the process of segmental oxidation is realized.
  • any two "oxidation reactors with internal and external chamber structure”, or “oxidation reactor with internal, intermediate and external three-chamber structure”, or “tower plug flow oxidation reactor”, or “horizontal flat push" The combination of the flow oxidation reactor can well make the oxidation reaction material in an approximate flat flow state, and realize the process of segmental oxidation.
  • a tower oxidation reactor with an approximate plug flow is combined with an oxidation reactor having an internal and external chamber structure; two tower oxidation reactor combinations with approximate plug flow. and many more.
  • the reaction conditions of the first oxidation reactor can therefore be more moderate, lowering the reaction temperature and reducing the consumption of the acetic acid solvent.
  • the product obtained in the first oxidation reactor is mainly m-methylbenzoic acid, a small amount of crystals of isophthalic acid and a trace amount of 3-carboxybenzaldehyde, and a small amount of meta-xylene.
  • the product of the first oxidation reactor is subjected to evaporation, crystallization, separation, and filtration to obtain meta-methylbenzoic acid and a small amount of crystals of isophthalic acid, and a cobalt and manganese catalyst remaining in the material and residual acetic acid having a content of about 10%.
  • the filter cake is beaten with water as an auxiliary solvent, and the slurry is sent to a high temperature and high pressure reactor by a high speed pump.
  • the m-methylbenzoic acid has a high solubility in water and is substantially dissolved in the slurry.
  • the crystal of isophthalic acid is quickly dissolved, and a small amount of meta-carboxybenzaldehyde contained in the crystal is quickly oxidized to isophthalic acid.
  • Formic acid The meta-methylbenzoic acid is also completely oxidized to isophthalic acid in the second oxidation reactor.
  • the second oxidation reactor discharges a solution of isophthalic acid.
  • the solvent is mainly water, and a small amount of acetic acid is present.
  • the concentration of acetic acid is 0 to 25%, the typical concentration is 15%, and the concentration of isophthalic acid is 5 to 50. %, typical concentration is 30 ° /. .
  • the residence time of the target product isophthalic acid under the oxidation reaction condition is reduced, and the consumption of meta-xylene is reduced.
  • a temperature gradient from low to high is formed from upstream to downstream of the reaction material, wherein: the high concentration region from meta-xylene to meta-methylbenzoic acid is a low temperature region, and the reaction temperature is 130 to 210 ° C, which lowers the reaction temperature and reduces
  • the residence time of the acetic acid solvent under high temperature conditions reduces acetic acid consumption.
  • the intermediate transition zone is a medium temperature zone and the reaction temperature is 180 to 288 °C.
  • the region from the high concentration region of meta-methylbenzoic acid to the isophthalic acid solution is a high temperature region, and the reaction temperature is 210 to 350 °C. Increase the temperature in the high temperature zone and increase the solubility of the solution.
  • the water content forms a gradient from low to high, and the proportion of the auxiliary solvent water in the mixed solvent increases from the initial 0% to the reactor discharge port to 100%.
  • An annular water distributor is used.
  • a tree-shaped water distributor can be employed in an oxidation reactor inner chamber having an inner and outer chamber structure, an oxidation reactor inner chamber having an inner and outer three-chamber structure, and a tower plug flow oxidation reactor.
  • the water flow direction of the trunk of the tree-shaped water distributor flows along the upstream and downstream directions of the reaction material from the upstream to the downstream, on the one hand, the heat is taken off from the upstream, and on the other hand, the temperature of the water supply to the downstream is preheated.
  • a method of simultaneously adding a catalyst of cobalt acetate, manganese acetate and a cocatalyst hydrobromic acid is adopted; the oxidation reaction of the internal and external chamber structure, the internal and external three-chamber structure oxidation reaction.
  • the combination of the oxidation reactors in which the multiple reactors are connected in series is a method of adding a catalyst of cobalt acetate, manganese acetate, and then adding a cocatalyst hydrobromic acid.
  • a weak oxidation reaction zone is placed on top of the liquid phase of the tower oxidation reactor.
  • the so-called weak oxidation reaction is to use the residual oxygen in the exhaust gas to carry out the oxidation reaction.
  • the oxygen in the exhaust gas is fully absorbed for the effective oxidation reaction, and the tail oxygen content is further reduced.
  • a small amount of auxiliary solvent water is gradually added before the position where a large amount of m-methylbenzoic acid is generated inside the oxidation reactor, and the liquidus temperature is raised.
  • the solvent acetic acid and the auxiliary solvent water, the catalyst, and the auxiliary catalyst are all recycled.
  • auxiliary solvent water, and a catalyst may be added to the additional acetic acid solvent.
  • the temperature from the meta-methylbenzoic acid to the 3-CBA reaction zone can also be appropriately increased to increase the overall reaction rate of the series oxidation at a temperature of 210 to 350 °C.
  • the temperature in the lowest temperature region of the oxidation reactor is 130 ⁇ 160 °C, and the temperature in the highest temperature region reaches 250 ⁇ 350. C, the temperature forms a gradient from low to high.
  • the solvent water added to the liquid phase material in the oxidation reactor may be heated by means of heat exchange in a tube, and the water inside the tube is passed through, and the outlet of the tube is a position where water is added to the liquid phase of the reactor as an auxiliary solvent.
  • the inlet end face of the tube is closed, and the horizontal pipe is used for water supply.
  • the tube is buried upstream of the liquid phase flow of the reactant, and the outside is the reactant liquid phase material, and heat is taken from the reaction heat of the upstream material to the downstream material. Water supply.
  • the mixture of the oxidation reaction raw materials, the solvent and the catalyst, and the auxiliary agent may adopt a preheating feed method, and adopt a method of heat exchange feeding in the reactor to take the higher temperature region downstream of the reaction material flow. After the heat is preheated, the mixture is discharged into the reactor liquid phase to obtain the temperature conditions required for the reaction.
  • a flat push flow or a plug flow oxidation reactor or an oxidation reactor zone is constructed, so that the liquid phase organic raw material phase of the reaction material forms an upstream and downstream relationship, and the final oxidation reaction target product isophthalic acid is effectively combined with the original
  • the di-terpene xylene and the intermediate product meta-methylbenzaldehyde, m-methylbenzoic acid, 3-CBA separation may be combined with an oxidation reactor having a special structure and an oxidation reactor in which a plurality of reactors are connected in series.
  • Oxidation reactor structure and oxidation reactor combination
  • An oxidation reactor having an internal and external chamber structure.
  • the oxidation reaction employs an oxidation reactor having an internal and external chamber structure.
  • the inner and outer chambers are separated by a built-in cylinder concentric with the oxidation reactor, and the bottom of the cylinder is connected to the inner wall of the bottom of the oxidation reactor body.
  • the gap between the outer side of the cylinder and the inner wall of the reactor body is the outer chamber, and the inner side of the cylinder is the inner chamber of the reactor.
  • the cylinder's twist is lower than the standard level of the reactor design, ensuring that the liquid phase materials in the inner and outer chambers are connected in the upper part of the reactor during normal production.
  • the outer side of the cylinder can be fixed by means of point support with the inner wall of the reactor body.
  • the supply of compressed air or other oxygen-containing gas (such as oxygen) or other oxygen-containing gas (such as oxygen) in the inner and outer chambers may be uniform. It is also possible to design the unit liquid phase volume compressed air or other oxygen-containing gas (e.g., oxygen) or other oxygen-containing gas (e.g., oxygen) supplied to the outer chamber to be larger than the inner chamber.
  • the liquid phase volume of the inner and outer chambers may be the same, or the outer chamber may be larger than the inner chamber, for example, the ratio of the outer chamber to the inner chamber volume is 2: 1, 3: 1, 4: 1, and the like.
  • compressed air or other oxygen-containing gas such as oxygen
  • other oxygen-containing gas such as oxygen
  • a braided grille is like a louver that is bent into a circular louver. The difference is that the width and angle of the leaf that extends into the outer chamber are different from those that extend into the inner chamber.
  • the topmost leaf that protrudes into the outer chamber is connected to the upper half of the cylinder (the leaf does not penetrate the inner chamber, only half of the leaves), the leaves are inclined downwards, and the angle of inclination is the axis of the reactor (ie, the vertical line) At an angle of 45 degrees, the leaf surface approximates a portion of the canopy, and the edge of the leaf reaches the position of the outer chamber cavity near the inner third of the loop.
  • the middle blade has the same width as the upper blade in the outer chamber, but the angle of downward tilt is 22 degrees.
  • the width of the intermediate blade extending into the inner chamber portion is the same as the width of the portion extending into the outer chamber, but is inclined upward, and the angle of inclination is 10 degrees (angle with the vertical line).
  • the lower blade is connected to the lower half of the cylinder, and only half of the blade extends into the inner chamber, the width and inclination angle being the same as the portion of the intermediate blade extending into the inner chamber.
  • the connection between the upper and lower parts of the cylinder can be achieved by providing a vertical reinforcing rib on the inside of the cylinder.
  • the leaves in the middle of the braid are also fixed to the ribs and fixed in the form of point supports to the upper and lower parts of the cylinder.
  • the height (distance) of the middle blade to the upper and lower parts of the cylinder is the same, which is one-fifth of the width of the half blade.
  • One or two annular compressed air or other oxygen-containing gas (such as oxygen) or other oxygen-containing gas (such as oxygen) distributor is arranged at the bottom of the outer chamber of the reactor to supply the compressed air or other oxygen-containing gas required for the reaction to the outer chamber. (such as oxygen) or other oxygen-containing gases (such as oxygen).
  • the volume of the outer chamber is equivalent to twice, three or four times the volume of the inner chamber.
  • the average volume of compressed air or other oxygen-containing gas (such as oxygen) or other oxygen-containing gas (such as oxygen) in the liquid phase material volume of the reactor outer chamber unit is greater than the average compressed air volume of the liquid phase material volume in the reactor unit or other
  • an oxygen-containing gas (such as oxygen) or other oxygen-containing gas (such as oxygen) is supplied, that is, when the supply of compressed air or other oxygen-containing gas (such as oxygen) in the outer chamber is excessive, excess compressed air or Other oxygen-containing gases (such as oxygen) diffuse into the inner chamber through the braided grid at the waist of the inner and outer chamber baffles (cylinders), and a small amount of liquid material in the outer chamber follows compressed air or other oxygen-containing gas (such as oxygen).
  • Entrained enters the inner chamber, and the material in the inner chamber does not enter the outer chamber through the braided grid.
  • compressed air or other oxygen-containing gas (such as oxygen) is supplied in excess and exceeds the upper limit limit of 4%.
  • the exhaust gas oxygen content control standard is 3 to 4%.
  • the supply of compressed air in the inner and outer chambers or other oxygen-containing gas is separately controlled, and the oxygen content in the inner and outer chambers is separately detected, and the braided grid on the cylinder separating the inner and outer chambers can be omitted.
  • oxygen-containing gas for example, oxygen
  • the annular distributor was used to supply water to the reactor from the middle and upper portions of the outer chamber of the reactor, and a cocatalyst was added at a water supply temperature of 180 °C. Ensure that the isophthalic acid formed by the reaction is completely dissolved in the water and acetic acid complex solvent.
  • the temperature in the lower part of the chamber can reach 246 ⁇ 350 °C.
  • the preferred temperature at the lower portion of the outer chamber is 288 °C.
  • the temperature at the bottom of the inner chamber is 130 to 180 Torr, and the temperature is preferably 160 ° C.
  • the upper temperature of the inner chamber is 210 to 288 ° C, and the temperature is preferably 288 ° C.
  • An annular water distributor was used to supply water to the upper part of the inner chamber at a water temperature of 30 ° C.
  • the annular distributor was used to supplement the middle portion of the inner chamber with acetic acid at a temperature of 30 ° C.
  • the logistics situation is: in the inner chamber, using a ring air distributor to blow compressed air or other oxygen-containing gas (such as oxygen) from the bottom, the fresh raw materials entering the reactor containing m-xylene, acetic acid, catalyst, etc. also enter from the bottom of the inner chamber. After a mixed reaction, enter the outer chamber from the upper part. The water and carbon dioxide generated by the reaction diffuse upward. In the outer chamber, the liquid material moves from top to bottom, and compressed air or other oxygen-containing gas (such as oxygen) diffuses from bottom to top, and the generated water and carbon dioxide diffuse upward.
  • compressed air or other oxygen-containing gas such as oxygen
  • a tree-shaped water distributor is used in the reactor interior instead of the annular water distributor to supply water to the inner chamber.
  • the flow of auxiliary solvent water in the trunk trunk is from bottom to top.
  • the final reaction product isophthalic acid
  • a mixed solvent of water and acetic acid discharged from the bottom of the outer chamber, and sent to the crystallization system for crystallization.
  • annular compressed air or other oxygen-containing gas e.g., oxygen
  • Two or more annular compressed air or other oxygen-containing gas (such as oxygen) distributors are arranged in the inner chamber of the reactor, the distributor is centered on the reactor axis, and a cross-shaped distributor can be added in the middle of the small annular distributor.
  • the rings are in the same plane.
  • the small annular distributor is located closer to the bottom of the reactor, and the medium annular distributor (which is larger in the inner chamber) is positioned slightly above the small distributor.
  • the large distributor is placed in the outer chamber.
  • the air distributor compresses the air or other oxygen-containing gas (such as oxygen) to open the hole downwards.
  • the opening direction is at an angle of 30 degrees to the vertical line, and is alternately staggered along the left and right directions of the ring line to make the air distribution more uniform.
  • the flow from top to bottom is basically a flat flow process, and the oxidation reaction is basically carried out in the order of the series oxidation reaction.
  • the oxidation reaction is basically carried out in the order of the series oxidation reaction.
  • all the reactions from meta-xylene to p-methylbenzaldehyde and the reaction from meta-methylbenzaldehyde to meta-methylbenzoic acid are completed in the middle of the outer chamber of the oxidation reactor.
  • the reaction from m-methylbenzoic acid to 3-CBA is completed in the middle of the outer chamber of the reactor, and the reaction from 3-CBA to isophthalic acid is completed in the lower part of the middle.
  • the lower part of the outer chamber maintains a short system equilibrium - ripening to remove residual 3-CBA and meta-methylbenzoic acid.
  • the oxidation reactor of the inner and outer chamber structure can ensure that the liquid phase material in the normal operation has no metaxylene, no meta-methylbenzaldehyde, no meta-methylbenzoic acid, no 3-CBA. , only isophthalic acid and solvent acetic acid, auxiliary solvent water, catalysts and additives, and a small amount of other impurities.
  • the ratio of water (water/water + acetic acid) in the mixed solvent of the discharge port is 50% to 100%, typical The ratio is 80%.
  • the initially charged acetic acid solvent is continuously flashed out of the reactor, and the replenished water solvent continuously enters the reactor.
  • This process is actually a process in which water is replaced by acetic acid, which creates conditions for the system to increase the temperature.
  • the liquid phase discharge port temperature should not exceed the design temperature, for example 288 ⁇ .
  • the amount of isophthalic acid that can be dissolved by the aqueous solvent at this temperature is almost 50% (by weight).
  • Increasing the flow rate of water increases the ability to remove heat and increases the amount of isophthalic acid that the aqueous solution carries to the crystallizer to achieve heat and material balance. As the flow rate of water increases, the actual concentration of the isophthalic acid solution at the discharge port is much lower than the saturated solubility at that temperature.
  • the internal room water supply temperature is 5 ⁇ 150°C, the typical water supply temperature is 30°C ; the external room water supply temperature is 20 ⁇ 250 ⁇ , and the typical water supply temperature is 180°C.
  • the concentration of the isophthalic acid solution in the outer chamber water and acetic acid as a mixed solvent is 0.1 to 35%, and the typical concentration is 30%.
  • the recovered catalyst is added to the water supply system storage tank to ensure the catalyst concentration in the oxidation reactor system.
  • the corresponding catalyst concentration (total content) is 0 to 5000 ppm, a typical concentration is 1050 ppm, and a typical ratio is cobalt: manganese-bromine is 1: 1:1.
  • the catalyst and the auxiliary catalyst are uniformly dispersed in the mixed solvent.
  • the proportion of water in the mixed solvent is 50 to 100%, and the typical ratio is 80 °/. .
  • the oxidation rate of the organic raw material phase is controlled and reasonable, and the consumption indexes of acetic acid and meta-xylene are lowered.
  • the internal chamber temperature is controlled at 130 ⁇ 210 ⁇ , the typical temperature is 16CTC; the upper chamber temperature is controlled at 246 ⁇ 350V, the typical temperature is 288°C, and the typical reactor pressure is 7.5MPaG.
  • the temperature in the discharge port area of the reactor can be set at a higher position, for example: 400 ⁇ 500 °C. At this time, in the mixed solvent, there is no acetic acid and only water, and the oxidation reaction residence time is shorter.
  • the oxidation reactor having an internal and external chamber structure may itself be a column reactor having a relatively long aspect ratio, and has an aspect ratio of 1. 0 to 20, and a typical aspect ratio of 6.
  • this tower-shaped oxidation reactor can be designed in the shape of a water tower to increase the liquid gas at the top of the liquid phase.
  • the area of the interface increases the area of liquid phase evaporation.
  • Oxidation reactor with internal, intermediate and external three-chamber structure.
  • two oxidation chambers are divided into inner, middle and outer chambers by using two internal cylinders concentric with the oxidation reactor.
  • the bottom of the small cylinder is connected to the bottom inner wall of the oxidation reactor body, and the upper portion is submerged below the design level.
  • a small cylinder separates the inner and middle chambers of the oxidation reactor.
  • the bottom of the large cylinder is suspended, the upper part is higher than the design liquid level, and the inner and outer sides are respectively fixed on the small cylinder and the side inner wall of the reactor main body, and are fixed at the bottom of the reactor main body by point support at the bottom.
  • a large cylinder separates the chamber from the outer chamber.
  • the three chambers of the inner, middle and outer chambers are in gas phase communication, and the liquid phase volume is the same (calculated by the volume of the liquid phase which is completely divided by the extension of the cylinder surface).
  • the inner, middle and outer chambers are each provided with compressed air or other oxygen-containing gas (e.g., oxygen) distributor at the bottom.
  • the annular compressed air or other oxygen-containing gas (e.g., oxygen) distributors in the outer and middle chambers are located slightly above the height of the bottom of the large cylinder to avoid uneven air supply to the two chambers.
  • the upper and lower positions of the large and small cylinders may be exchanged, i.e., the large cylinder is suspended, and the lower side of the small cylinder is connected to the bottom of the inner wall of the reactor body.
  • the three chambers have the same liquid phase volume, and the compressed air or other oxygen-containing gas (e.g., oxygen) supply flow is the same.
  • oxygen-containing gas e.g., oxygen
  • the liquid phase volume ratio of the inner and outer three chambers may be 1: 2: 2, or 1: 2: 3.
  • the liquid phase flow situation is: m-xylene, acetic acid, catalyst, etc. are mixed from the bottom of the inner chamber of the reactor, and the inner chamber material is ascended, reaching the upper portion and entering the middle chamber from the upper side of the small cylinder.
  • the middle chamber material descends, reaching the bottom and entering the outer chamber from the lower side of the large cylinder.
  • the material in the outer chamber is ascended, and the material that has been reacted is discharged from the upper portion of the outer chamber.
  • a ring distributor to slowly supply water from the lower and middle portions of the reactor outer chamber; using a ring distributor to supply water from the upper and middle portions of the reactor to the reactor, adding a cocatalyst hydrobromic acid; using a distributor from the reactor chamber
  • the middle and upper parts supply water to the reactor and the ratio of acetic acid, water and acetic acid is 20:80 to 100:0, and the typical ratio is 50:50.
  • the reaction temperature is balanced, and on the one hand, the organic raw material solution is diluted to prepare for raising the temperature.
  • the internal solvent replenishment solvent temperature is 20 ⁇ 150 ⁇ , the typical water supply temperature is 3 (TC ; the medium room water supply temperature is 20 ⁇ 200°C, the typical water supply temperature is 120°C ; the external room water supply temperature is 20 ⁇ 250°C, the typical water supply temperature It is 180 ° C.
  • the internal chamber temperature is controlled at 145 ⁇ 210 ° C, the typical temperature is 16 (TC ; the middle chamber temperature is controlled at 180 ⁇ 288 ° C, the typical temperature is 250 ⁇ ; the upper chamber temperature is controlled at 246 ⁇ 350 ° C 5MPaG ⁇
  • the typical temperature is 288 ° C, the reactor pressure is 7. 5MPaG.
  • the inner-circle mixed solvent distributor can be replaced by a tree-shaped water distributor, and the main trunk flow direction is from bottom to top, that is, heat preheating is taken from the upstream to increase the temperature of the mixed solvent for downstream.
  • the bottom of the middle chamber and the outer chamber are all high temperature regions, so even if the isophthalic acid crystals formed by rapid oxidation in the upper portion of the middle chamber appear, they will be dissolved in the process of descending with the liquid material.
  • the flow is changed accordingly, the arrangement of the air distributor, and the setting position of the water distributor are also changed accordingly.
  • the raw material is fed from the upper part of the inner chamber, and enters the middle chamber from the lower part through the mixing reaction.
  • the middle chamber material goes up, enters the outer chamber from the upper part, and the outer chamber material descends, and discharges from the bottom bottom.
  • Compressed air or other oxygen-containing gases still enter the lower part of each chamber.
  • the temperature control of each chamber is changed according to the order of the logistics.
  • the oxidation reactor itself can also be a column reactor having a relatively long aspect ratio, the aspect ratio of which is 1. 5 to 20, and the typical aspect ratio is 6.
  • the tower-shaped oxidation reactor can be designed in the shape of a water tower to increase the area of the gas-liquid interface at the top of the liquid phase and increase the liquid phase evaporation area.
  • a built-in cylinder immersed in the liquid phase is further disposed in the outer chamber, and the outer chamber is divided into two, and the cylinder is connected to the bottom of the reactor main body.
  • the material entering the outer chamber from the middle chamber is ascended again and then discharged downward from the bottom of the reactor side.
  • This optimization scheme actually transforms the three-chamber oxidation reactor into a four-chamber oxidation reactor with air distributors in all four chambers.
  • One end of the reactor feeds the other end of the reactor.
  • the bottom of the reactor is provided with a series of straight tubular compressed air or other oxygen-containing gas (such as oxygen) distributor and several rows of water supply distributors.
  • This reactor is similar to a flat push flow reactor.
  • a spiral sheet propulsion shaft can be arranged in the reactor to slowly advance the material along the flow direction of the liquid material.
  • the spiral sheet propulsion shaft does not need to be in contact with the inner wall of the reactor, and the advancement of the material is only symbolic, and the main purpose is Dynamic chambering is carried out inside the reactor to reduce the disordered fluidity of the liquid phase material, and to ensure that the oxidation reaction of the liquid phase material proceeds in the order of flow direction from the meta-xylene to the isophthalic acid series oxidation reaction.
  • the upper part of the reactor is in gas phase communication, part of the acetic acid solvent and water are evaporated, carbon dioxide, nitrogen and the like are volatilized, and then enter the gas phase condensation heat exchange system to recover heat, and heat is removed from the reactor.
  • the gas phase outlet is disposed at the upper portion of the discharge end, and the condensate is sent to a storage tank for recovering acetic acid and water.
  • Acetic acid and water were added upstream of the reactor stream using a distributor, and water was added to the midstream and downstream to ensure that the isophthalic acid and 3-CBA formed by the reaction were completely dissolved in a mixed solvent of water and acetic acid.
  • the temperature at the inlet end of the reactor i.e., the oxidation of meta-xylene to m-methylbenzoic acid, is controlled by the addition of a mixed solvent of low-temperature acetic acid and water.
  • the temperature in this region is 145 to 210 ° C, preferably 16 CTC. As the water content increases, the temperature can be gradually increased, but the reaction should not be controlled too much. When the water content does not reach 50%, the temperature does not exceed 250 °C.
  • the middle temperature is controlled at 180 to 288 ° C, and the typical temperature is 250 ° C.
  • the spiral plate advancement shaft can be eliminated and the reactor structure can be simplified.
  • the tower plug flow oxidation reactor is a tower reactor with a relatively long aspect ratio, and the long diameter ratio is 6 to 30, and the typical long diameter ratio is 20.
  • the reactor is internally sectioned with annular compressed air or other oxygen-containing gas (e.g., oxygen) distributor and annular inlet distributor. Nitrogen and carbon dioxide generated by the reaction, organic exhaust gas, and the like are volatilized from the upper portion of the reactor, cooled or treated by a heat exchanger. A small amount of acetic acid solvent and water are volatilized into the condensing system.
  • the reaction heat is withdrawn from the crystallizer by a large amount of solvent, heat is recovered by heat exchange, or heat is exchanged through the heat exchanger before entering the crystallizer to recover heat.
  • the reaction temperature in the corresponding region can be continuously increased to withstand the tendency of the reaction rate to decrease due to a decrease in the concentration of the reactant.
  • the outlet temperature can reach 246 ⁇ 350 °C, and the typical temperature is 288 °C.
  • the initial temperature of the mixture of the raw material m-xylene, the solvent acetic acid, the catalyst, and the auxiliary catalyst enters the reactor at 130 to 210 ° C, and the typical temperature is 160 ° C.
  • the reactor pressure was 7.5 MPaG.
  • the temperature of the reactants is kept stable, and the organic raw materials of the reactants are diluted to achieve a balance between the reaction temperature, the reaction heat, the reaction rate, and the water flow rate.
  • the concentration of the organic raw materials of the reactants is gradually decreased, and the reaction temperature is gradually increased to strengthen the reaction conditions, and the reaction rate is maintained and stabilized.
  • a tree-shaped water distributor is used to supply water into the tower, and the main stream of the trunk flows in a direction from top to bottom, that is, heat is taken from the upstream of the liquid phase of the reactant, and the downstream solution is diluted.
  • Winding the tube on the outer wall of the reactor, using a cooling medium to heat exchange is an effective heat removal measure.
  • a heat exchange coil is arranged inside the reactor, and the flow of the cooling medium in the coil flows from the upstream to the downstream along the flow of the reaction material.
  • the surface temperature of the coil immersed in the isophthalic acid solution area cannot be lower than the liquid phase concentration in the area as the temperature corresponding to the saturated solubility, avoiding the formation of isophthalic acid crystal on the outer surface of the coil.
  • the coil does not enter the concentration zone of isophthalic acid, which still relies on the addition of low temperature water to balance the temperature.
  • the addition of low temperature water may result in localized formation in the liquid phase, so the present invention reserves sufficient ripening zone at the bottom of the column to allow small crystalline particles to be redissolved.
  • the temperature of the dendritic water distributor in the high concentration region of the isophthalic acid solution cannot be lower than the concentration corresponding to the saturated solubility (crystallization precipitation temperature).
  • the added water solvent is the water recovered after the flash heat exchange of the crystallizer, containing the catalyst and auxiliary for recycling.
  • Catalyst typical catalyst concentration is 900 ppm, typical cobalt: manganese: bromine ratio is 1: 1:1.
  • the raw materials, solvent, catalyst including recovery solvent and recovery catalyst
  • compressed air or other oxygen-containing gas such as oxygen
  • the material runs from top to bottom and is discharged from the lower part of the reactor by liquid level control.
  • the material stream is approximately a plug flow from top to bottom inside the reactor.
  • Compressed air or other oxygen-containing gases (such as oxygen) and the carbon dioxide generated by the reaction will carry a small amount of liquid material upwards, increasing the residence time of a small amount of isophthalic acid inside the reactor, but will not affect the overall situation.
  • the reaction control is also controlled by controlling the feed rate of m-xylene, acetic acid feed, compressed air or other oxygen-containing gas (such as oxygen) and the feed rate of water to control the temperature balance in the reactor and the organic raw materials of the reactants.
  • the reaction is completed in the lower part of the reactor. Taking into account the heat balance, by adding water, the purpose of smooth heat recovery is achieved.
  • Typical temperature control is: The liquidus top temperature is controlled at 160 ⁇ , the intermediate temperature is controlled at 250 °C, and the bottom temperature is controlled at 288 °C. From the low temperature end to the high temperature end, the liquid water content gradually increases, forming a gradient. From top to bottom, the temperature gradually rises to form a gradient, and the liquid water content gradually increases to form a gradient.
  • the oxidation conditions of the first oxidation reactor are controlled to make the temperature more moderate.
  • the reactor temperature is 130 to 210 ° C, or even 130 to 150 ° C, and the typical temperature is 160 ⁇ ; only cobalt acetate, manganese acetate catalyst is added, and no hydrobromic acid auxiliary catalyst is added. Under this condition, the reaction from meta-methylbenzoic acid to 3-CBA is difficult.
  • the heat removal method of this reactor is similar to the current isothermal recovery process of isophthalic acid and terephthalic acid oxidation reactors, using a solvent flashing heat removal method.
  • the liquid material adopts a single logistics method from top to bottom, which makes the liquid material flow relatively stable.
  • the grounding is carried out in the order of the series oxidation reaction.
  • the key to the process conditions is:
  • the temperature of the second oxidation reactor is 246 ⁇ 350 °C, and the typical temperature is 288 ⁇ . At this temperature, the saturated solubility of isophthalic acid is about 50%, the control concentration is 20 to 35%, and the typical controlled concentration is 30%.
  • the discharge port is placed at the opposite corner of the feed port below the reactor.
  • the reactor is deheated using a solvent flash heat removal method.
  • the oxidation reaction material is delivered from the first oxidation reactor to the second oxidation reactor by means of a high pressure pump.
  • Auxiliary catalyst hydrobromic acid is added to the second oxidation reactor.
  • the final oxidation reactor temperature is controlled at 246 to 350 ° C, with a typical temperature of 288 ° C.
  • the third oxidation reactor (and the final oxidation reactor) employs a solvent flash heat removal method.
  • This multi-reactor tandem oxidation reactor combination can also be combined with "oxidation reactors having internal and external chamber structures" and "oxidation reactors having internal, intermediate and external three-chamber structures". That way, there are two reactors that can be combined.
  • a conventional oxidation reactor and an oxidation reactor having an internal and external chamber structure are combined: a conventional oxidation reactor for low temperature oxidation, the reaction temperature is 130 to 210 ° C, or even 130 to: 150 ° C, and the typical temperature is 160 ⁇ ; only cobalt acetate, manganese acetate catalyst, no hydrobromic acid auxiliary catalyst.
  • the method of heat removal using solvent flashing The reaction residence time is 20 to 150 minutes, and the typical residence time is 60 minutes.
  • the main product in the reaction mixture slurry is meta-methylbenzoic acid.
  • the reacted material is fed into an internal chamber of an oxidation reactor having an inner and outer chamber structure, and the bottom is fed.
  • the inner chamber material is ascending and the outer chamber material is descending.
  • the material is flashed in the inner chamber and replenished with water, and the acetic acid solvent is replaced one by one.
  • the reactor temperature is controlled to be 246 to 350 ° C and the typical temperature is 288 ° C.
  • the oxidation reaction uses meta-xylene as the main raw material, oxygen in compressed air or other oxygen-containing gas (such as oxygen) as auxiliary material, acetic acid as the initial solvent, cobalt acetate and manganese acetate as the catalyst, and hydrobromic acid as the auxiliary. catalyst.
  • Water is used as an auxiliary solvent in the later stage of the oxidation reaction.
  • water is added as a supplementary solvent from the high-level position of the high concentration of meta-methylbenzoic acid and meta-methylbenzoic acid, and it is required to be in the liquid phase material of the 3-CBA to isophthalic acid oxidation reaction zone.
  • Adding enough water as an auxiliary solvent for isophthalic acid appropriately increasing the reaction temperature, increasing the solubility parameter of isophthalic acid in water and acetic acid mixed solvent, so that the isophthalic acid formed by the reaction is completely dissolved in the solvent.
  • the temperature from the meta-methylbenzoic acid to the 3-CBA reaction zone can also be suitably increased, for example, 288 Torr, to increase the reaction rate of the series oxidation reaction.
  • Water as a solvent may be gradually added to the meta-methylbenzoic acid to the 3-CBA oxidation reaction zone, or may be added to the reaction zone before the formation of the meta-methylbenzoic acid. From the meta-xylene to the isophthalic acid reaction process, the water content is gradually increased to form a gradient of water in the solvent of 0 to 100%. In practice, it is feasible to control the gradient of water in the solvent of 5 to 95%.
  • a typical isophthalic acid solution concentration is 30%, and a typical water ratio in a mixed solvent is 80%.
  • the typical temperature is 288 ⁇ and the reactor pressure is 7.5 MPaG.
  • the solvent ice added to the liquid phase material in the oxidation reactor can be heated by means of heat exchange in a tube, and the inside of the tube is passed through water, and the outlet of the tube is a position where water is added to the liquid phase of the reactor as an auxiliary solvent, and the tube is placed.
  • the inlet end face is closed and water is supplied from the lateral tube.
  • the tube is buried upstream of the reactant liquid phase stream and the outside is the reactant liquid phase
  • the material is taken from the heat of reaction of the upstream material to dilute the liquid phase material downstream.
  • the oxidation reaction pressure of the present invention is about 0.5 to 8. OMPaG, and the reaction temperature is divided into about 130 to 210 ° C and about 180 to 250 ° C, and about 210 to 350 ° C, and the segmentation control.
  • the typical temperature and pressure of the low temperature section are respectively 16CTC and 0. 5MPaG ; the temperature and pressure of the typical medium temperature section are 25 (TC and 5. OMPaG; the temperature and pressure of the typical high temperature section are 288 ° C and 7. 5MPaG, respectively.
  • the amount of solvent and water that is flashed into the top condenser of the reactor By controlling the amount of solvent and water that is flashed into the top condenser of the reactor, the reflux of the condensate, the flashing of the crystallizer acetic acid solvent and the water solvent, the temperature and amount of water and acetic acid that are replenished into the reactor, compressed air Alternatively, the amount of other oxygen-containing gas (for example, oxygen), the amount of nitrogen and carbon dioxide, and the heat of reaction, such as heat of reaction, are integrated into the reactor.
  • oxygen-containing gas for example, oxygen
  • the amount of nitrogen and carbon dioxide the amount of nitrogen and carbon dioxide
  • the heat of reaction such as heat of reaction
  • the reactor pressure is controlled by controlling the amount of compressed air or other oxygen-containing gas (e.g., oxygen) and the opening of the non-condensing gas outlet regulator of the reactor off-gas condensing system.
  • Temperature is the first control element and the pressure parameters are set to match the temperature requirements.
  • the upper pressure limit is the first element of safety control.
  • the inlet pressure of the air compressor needs to be increased due to the increase of the reactor pressure.
  • an air compressor with an outlet head of 9.3 MPaG is used.
  • a tower oxidation reactor having a diameter of 4000 Torr and a height of 28,000 mm was used as the first oxidation reactor.
  • the meta-xylene was used as the starting material, acetic acid was used as the initial solvent, and cobalt acetate and manganese acetate were used as the catalyst.
  • the effective component of the catalyst was cobalt and manganese ion content (ion mass sum) was 700 ppm, and the ratio of cobalt to manganese was 1:1.
  • the initial raw material ratio (mass) was m-xylene: 30%, acetic acid: 64%, 7K: 6%.
  • the prepared raw materials and catalyst are fed from the upper end of the oxidation reactor, and the liquid phase material is descended.
  • the meta-xylene feed flow rate was 128 tons / hour.
  • the liquid phase material enters the reactor from the upper portion of the reactor, and the reaction product is discharged from the bottom.
  • the compressed air enters the reactor from the bottom side of the reactor in six ways.
  • the heat of reaction is withdrawn from the top of the reactor by solvent flashing.
  • the heat exchanger is used to recover heat.
  • the heat exchanger can be a condensation tower. After the condensate removes a small amount of acetic acid, some of the water is returned to the oxidation reactor.
  • the internal water content of the reactor is 6-20%, and the typical water content is 10%.
  • the oxygen content of the reactor tail gas is controlled to be less than 1-3%, ensuring the safety of the oxidation reactor and improving the utilization of compressed air.
  • the inlet pressure of the compressed air is 0. 5MPaG.
  • the internal pressure of the reactor is 0. 1- 0. 3MPaG.
  • temperature reflex 110-160 ° C, the typical temperature 'degree is 145 ° C. Since meta-methylbenzoic acid is relatively difficult to be oxidized, and there is no hydrobromic acid auxiliary catalyst inside the system, under this condition, meta-xylene is mainly oxidized to form meta-methylbenzoic acid, and a small amount of meta-position The benzoic acid will be oxidized to phthalic acid to form a crystalline precipitate.
  • the area near the discharge opening at the bottom of the reactor is substantially free of meta-xylene.
  • the bottom is discharged, and the material is concentrated by evaporation to remove acetic acid and water and a small amount of meta-xylene to obtain 68% of isophthalic acid, 17% of meta-xylene, 11% of acetic acid, and 4% of water. mixture.
  • the mixture is slurried with deionized water, and hydrobromic acid is added as a co-catalyst in the slurry according to the ratio of m-xylene content of 350 ppm (ion mass concentration), the first oxidation stage.
  • the added cobalt and manganese catalysts are still present and effective.
  • the slurry is fed to the upper end of the liquid phase of the second oxidation reactor using a high speed pump.
  • the second oxidation reactor adopts a tower oxidation reactor with a diameter of 4500 ⁇ and a height of 36,000 awake (it is also possible to use an oxidation reactor having an inner and outer chamber structure, or an oxidation reactor having an inner and outer three-chamber structure, or a horizontal flat push). Flow oxidation reactor). Oxygen is used as an auxiliary material (compressed air can also be used as an auxiliary material).
  • the second oxidation reactor has a liquidus temperature of 285-300 Torr and a typical temperature of 288 °C. Temperature is the first control element and pressure is the second control element.
  • the solvent is flashed and the vapor is withdrawn from the top of the reactor to remove the heat.
  • the solvent mixed with water and acetic acid is subjected to partial condensation at the condensation column at the top of the oxidation reactor, and water and acetic acid are separately introduced into the storage tank of water and acetic acid.
  • the sub-condensation tower heats the low-pressure vapor by heat exchange to recover heat.
  • the device In order to avoid the use of high-flow high-pressure air compressors, the device is empty.
  • the liquid oxygen supplied by the sub-device acts as a raw material for the oxidant.
  • the liquid oxygen is sent to the evaporator through a high pressure pump (or high speed pump), and the cold energy is recovered in the evaporator, and the vaporized oxygen is introduced from the bottom of the oxidation reactor.
  • the oxygen line enters from the upper part of the reactor and preheats the oxygen inside the line with the reaction material.
  • the oxygen distributor With a toroidal oxygen distributor, the oxygen distributor has three rings, and the diameters of the three rings are 2000 ⁇ , 3200 awake and 4000 awake, respectively.
  • a cross-distributor with a diameter of 2000 mm is added in the middle of the ring. Since the total amount of oxygen gas is relatively small compared to the use of compressed air, the reactor liquid phase is less disturbed by the upward influence of the gas, and the liquid phase material flow is relatively stable from the top to the bottom, which is equivalent to the plug flow, the upper raw material and The intermediate oxidation product does not settle quickly to the bottom. Also, due to the oxygen-passing portion, the water content in the liquid phase material is 61%, and the total organic phase is about 39%, so that no severe oxidation reaction occurs. Control the oxygen content of the reactor off-gas to less than 1-2%, ensuring the safety of the oxidation reactor and increasing oxygen utilization.
  • the annular oxygen distributor can be arranged in two or three layers to reduce the disturbance of the liquid phase material at the bottom of the reactor due to the introduction of the gas, so that the lower material is lowered closer to the plug flow.
  • the liquid phase material in the lower part of the reactor is exothermic due to the reaction, causing local heating (trend), water and acetic acid are vaporized, Ascending, water and acetic acid vapor reach the gas phase at the top of the reactor and then enter the sub-condensation tower to remove heat. This vapor rise process also disturbs the plug flow down the liquid material, but does not cause the top meta-methylbenzoic acid material to settle to the bottom quickly.
  • the isophthalic acid crystals in the slurry added from the top end of the oxidation reactor liquid phase will be dissolved quickly during the sedimentation process, and the contained 3-CBA is also quickly oxidized to isophthalic acid.
  • the oxygen inlet pressure is 8. 0MPaG.
  • the internal pressure of the reactor is 7. 3-7. 5MPaG.
  • the main components of the second oxidation reactor off-gas are small amounts of oxygen and carbon dioxide, carbon monoxide, and trace amounts of acetic acid and other organic components.
  • the pressure is 7.5 MPaG.
  • the isophthalic acid solution is out, wherein isophthalic acid accounts for 27%, acetic acid accounts for 11%, and water accounts for about 72%.
  • the isophthalic acid solution was sent to the first crystallizer where it was flashed and crystallized at 255 ° C, and about 19.5 percent of isophthalic acid precipitated to form crystals.
  • a rectification tower is used for heat exchange to recover steam waste heat, and acetic acid and water are initially separated. A little refined acetic acid is used to prepare the meta-xylene raw material as a solvent. Water is added to the deionized water added to the second oxidation reactor, and is added to the reactor to supplement the auxiliary solvent water, reduce the acetic acid concentration, and reduce the acetic acid consumption.
  • the remaining crystallized solution of the first crystallizer was sent to a second crystallizer, flashed and crystallized under conditions of 200 Torr, and approximately 7 percentage points of isophthalic acid crystallized out.
  • a rectification tower is used for heat exchange to recover the waste heat of the vapor, and the acetic acid and the water are initially separated. Crude acetic acid and water are fed to their respective storage tanks.
  • the remaining crystallized solution of the second crystallizer is sent to the third crystallizer, and is flashed and crystallized at 150 ° C, and about 0.8% of the isophthalic acid crystals are precipitated.
  • a rectification tower is used for heat exchange to recover the waste heat of the vapor, and the acetic acid and the water are initially separated. Crude acetic acid and water are fed to their respective storage tanks.
  • the remaining solution of the third crystallizer is filtered to remove solid impurities, a portion is sent to the mother liquor recovery treatment system, the catalyst is recovered, the dissolved impurities are removed, and the remaining mother liquor is used for meta-methylbenzoic acid beating.
  • the isophthalic acid crystal obtained by the crystallization system is washed with acetic acid (the cobalt, manganese, bromine catalyst and auxiliary catalyst are removed, and this step can also be omitted), separated, dried, washed, separated, and dried to obtain a purified isophthalic acid product.
  • the 3-CBA content is less than 10 ppm, and the meta-methylbenzoic acid content is less than 5 pp m .
  • the hourly production of refined isophthalic acid is 200 tons.
  • the consumption per unit of product was 652 kg / ton, and the energy consumption for burning was 99 kg of standard oil per ton.
  • Acetic acid consumption is 9 kg / ton.
  • the unit uses liquid oxygen supplied by the air separation unit as the oxidant source.
  • the liquid oxygen is sent to the evaporator through a high pressure pump (or high speed pump).
  • the vaporized oxygen is passed from the bottom to the oxidation reactor (the oxygen tube is high from the upper part of the reactor and enters the reactor.
  • the phase material is heated.
  • the annular oxygen distributor is used.
  • the oxygen distributor has three rings, and the diameters of the three rings are 2000 mm, 3200 mm and 4000 ⁇ , respectively. A cross-distributor with a diameter of 2000 mm is added in the middle of the ring.
  • the bottom liquid phase may be less disturbed by the upward influence of the gas, and the liquid phase material flow is relatively stable from top to bottom as much as possible, corresponding to the plug flow, the upper layer of raw materials and the middle.
  • the oxidation product does not settle quickly to the bottom.
  • the water content in the liquid phase material is 59%, and the total organic phase is about 41%, so that no severe oxidation reaction occurs.
  • the oxygen content of the reactor off-gas is controlled to be less than 1-2%, ensuring the safety of the oxidation reactor and increasing the oxygen utilization rate.
  • the annular oxygen distributor can be arranged in two or three layers to reduce the disturbance of the liquid phase material at the bottom of the reactor due to the introduction of the gas, so that the lower material is lowered closer to the plug flow.
  • the oxygen inlet pressure is 8. lMPaG.
  • the internal pressure of the reactor was 7.5 MPaG.
  • the temperature in the high temperature zone at the bottom of the reactor is still below the boiling point and no boiling occurs.
  • the oxidation reactor liquid phase temperature is divided into four sections of control -
  • the liquid material is more than 5 parts from top to bottom, the temperature is controlled at 130-180 ° C, and 160 ⁇ is better.
  • xylene is oxidized to meta-methylbenzaldehyde and meta-methylbenzaldehyde. Oxidation to meta-methylbenzoic acid is faster, and relatively mild temperature can reduce acetic acid consumption (oxidized to carbon dioxide or carbon monoxide).
  • the oxidation reaction heat in this region is mainly used for the temperature rise of the raw material xylene and the solvent acetic acid and water.
  • the mixed raw material of m-xylene and acetic acid, water and catalyst enters the liquid phase from the top of the liquid phase material.
  • This fresh raw material has a strong oxygen binding ability for robbing a small amount of oxygen remaining in the oxygen-containing gas.
  • this fresh mixed feedstock is passed 500 mm below the liquid level of the liquid feed.
  • the liquid material from the top to the bottom of 5 to 5 / 5 the temperature is controlled at 210-300 ⁇ , 288 °C is better.
  • This zone stabilizes the liquidus temperature by adding 100-20 CTC high temperature deionized water to suppress the tendency of the liquid phase material to rise due to the exothermic oxidation reaction.
  • the high temperature deionized water is sprayed from the side wall of the reactor into the liquid phase material, or the annular water distributor is used to spray water into the liquid phase material.
  • the deionized water nozzle or the annular water distributor adopts a two-stage alternating use method (or a two-part method) to precipitate and crystallize the isophthalic acid near the nozzle or crystallize on the annular water distributor. The crystals dissolve.
  • This region mainly completes the oxidation reaction from meta-methylbenzoic acid to isophthalic acid.
  • the main components of the oxidizing tail gas are small amounts of oxygen and carbon dioxide, carbon monoxide, and trace amounts of acetic acid and other organic components.
  • the pressure is 7.5 MPaG.
  • This process is different from the current meta-xylene oxidation process. There is no large amount of solvent flashing heat removal at the top of the reactor. The liquid phase of the reactor forms a gradient from top to bottom, and most of the heat of reaction is absorbed by heating the deionized water. , withdrawn by deionized water in the crystallizer flashing heat release. The vapor obtained by flashing recovers heat through the heat exchanger. Due to the absence of large amounts of nitrogen, the liquid phase flow of this process is relatively stable and closer to the plug flow.
  • cooling water can be added to the inside of the reactor.
  • Column heat exchangers from top to bottom can be placed inside the reactor.
  • the inside of the tube is passed into the deionized cooling water, the water temperature is 36 ° C, the flow direction of the water is from top to bottom, the outlet of the water inside the tube is dispersed at different heights of the liquid phase of the reactor, and the amount of water discharged at a position where the heat of reaction heat is large is large. Maintain stable reaction temperature in each zone.
  • the advantages of this scheme are as follows: 1. Take heat from the upper part to the lower part of the liquid material in turn, and maintain the gradient of the liquid material rising from top to bottom. 2.
  • the temperature difference prevents the isophthalic acid crystals from depositing on the heat exchanger tube wall.
  • the amount of water entering the deionized water was 133 tons/hour.
  • the first temperature control zone does not emit water, completely relies on the heat of the tube heat exchanger; the second temperature control zone is evenly dispersed from top to bottom.
  • the water (actual temperature is 200-280 ° C) dilutes the liquid phase material, absorbs the heat of reaction, and maintains the liquidus temperature at 288 ° C.
  • the location of the water outlet and the amount of water discharged depend on the number of openings in the tube at different locations, determined by 2-3 valves.
  • an isophthalic acid solution was obtained, in which isophthalic acid accounted for 17.5%, acetic acid accounted for 23.5%, and water accounted for 58.2%.
  • the isophthalic acid solution is sent to the first crystallizer, flashed and crystallized at 255 ° C, and about 10% of isophthalic acid precipitates to form crystals.
  • a rectification tower is used to recover the residual heat of the vapor, and the acetic acid and the water are initially separated. A little refined acetic acid is used to prepare the meta-xylene raw material as a solvent. Ice is used as the deionized cooling water in the third stage temperature control zone and is added to the reactor for temperature control or to the water storage tank.
  • the remaining solution of the first crystallizer crystals was sent to a second crystallizer, flashed and crystallized at 20 CTC, and about 7% of isophthalic acid crystals were precipitated.
  • a rectification tower is used for heat exchange to recover the waste heat of the vapor, and the acetic acid and the water are initially separated. A little refined acetic acid is used to prepare the meta-xylene raw material as a solvent. Water is used as the deionized cooling water in the third stage temperature control zone and is added to the reactor for temperature control or to the water storage tank.
  • the remaining solution of the second crystallizer crystals is sent to a third crystallizer, which is flashed and crystallized under conditions of 15 TC, and about 0.8% of isophthalic acid crystals are precipitated.
  • a rectification tower is used for heat exchange to recover the waste heat of the vapor, and the acetic acid and the water are initially separated. A little refined acetic acid is used to prepare the meta-xylene raw material as a solvent.
  • Water is used as the deionized cooling water for the third temperature control zone and is added to the reactor for temperature control or to a water storage tank.
  • the remaining solution of the third crystallizer is filtered to remove solid impurities, and a part is sent to the mother liquor recovery treatment system to recover the catalyst to remove the dissolved impurities, and the remaining mother liquor is used to oxidize the cooling medium of the liquid phase material inside the reactor, which is dehydrated from the cold water.
  • the isophthalic acid crystal obtained by the crystallization system is washed with acetic acid (the cobalt, manganese, bromine catalyst and auxiliary catalyst are removed, and this step can also be omitted), separated, dried, washed, separated, and dried to obtain a purified isophthalic acid product.
  • acetic acid the cobalt, manganese, bromine catalyst and auxiliary catalyst are removed, and this step can also be omitted
  • the hourly production of refined isophthalic acid is 120 tons; the consumption of meta-phthalic acid products per unit is 651. 5 kg / ton, the energy consumption for burning is 108 kg of standard oil / ton; the consumption of acetic acid is 18 kg / ton.
  • the oxidation reactor discharge is controlled by the liquid level into the first crystallizer.
  • the crystallization system is provided with 7 series crystallizers, and the crystallizer is provided with a stirrer.
  • the crystallization temperature was sequentially lowered, and the temperature difference of each crystallizer was 21 ° C, that is, the first crystallizer temperature was 267 ° C, the second crystallizer temperature was 246 ° C, and so on, and the seventh crystallizer temperature was 120 Torr. Uniform grain size distribution, average particle size of 120 microns, size matching Polyester industry requirements.
  • the flashed solvent is passed through a heat exchanger to recover heat, and the solvent acetic acid and solvent water are recycled.
  • the mother liquor after the final stage of crystallizer separation of the crystals removes the floating solid impurities and is sent to the solvent recovery and catalyst recovery system.
  • the crystallization system can have only 4 or 5 crystallizers, increasing the temperature difference between the individual crystallizers. It is also possible to appropriately increase the temperature of the last crystallizer, for example, to 160 °C.

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Description

一种精间茏二甲酸的制造方法 技术领域
本发明属于石油化工领域, 是一种石油化工产品的新的制造方法。
背景技术
精间苯二甲酸(英文缩写 PIA), 意思是高纯度间苯二甲酸。 精间苯二甲酸产品 是一种聚酯原料。精间苯二甲酸与乙二醇酯化、缩聚得到的聚间苯二甲酸乙二醇酯是 一种低瑢点聚酯, 熔点是 65°C。 精间苯二甲酸可以与精对苯二甲酸(PTA)混合与乙 二醇酯化和縮聚生产瓶用聚酯树脂。 按照不同比例将精间苯二甲酸 (PIA) 与精对苯 二甲酸(PTA)混合, 再与乙二醇酯化、缩聚, 可以得到不同熔点的低熔点聚酯树脂。 其中, 精间苯二甲酸(PIA) 与精对苯二甲酸(PTA) 1: 1 混合, 再与乙二醇酯化、 缩聚得到的聚混合苯二甲酸乙二醇酯的熔点为 120°C。
精间苯二甲酸产品现在国内只有燕山石化公司生产, 其产品中的主要杂质是 3- 羧基苯甲醛(间位羧基苯甲醛, 3-CBA)和 3-甲基苯甲酸(间位甲基苯甲酸)。 精间 苯二甲酸 (PIA) 中 3- CBA含量一般小于 25ppm, 间位甲基苯甲酸含量小于 150ppm。
现有的生产工艺中, 精间苯二甲酸(PIA) 以间二甲苯为原料, 以压缩空气或者 其它含氧气体(例如氧气)中的氧气为辅助原料, 以醋酸为溶剂, 以醋酸钴、醋酸锰 为催化剂, 以氢溴酸为辅助催化剂, 在相对温和的温度条件下进行混合氧化反应。在 氧化反应器液相反应物料中, 原料、 目标产物、 中间产物、溶剂等同时存在。 间苯二 甲酸在氧化反应器内形成结晶时, 3-CBA与间苯二甲酸形成共结晶, 从而被包裹在晶 粒内部无法被进一步氧化。
经过氧化反应、 间苯二甲酸结晶、 分离、干燥等工序, 得到粗间苯二甲酸。粗间 苯二甲酸中含有大量的间位羧基苯甲醛(3-CBA) 和间位甲基苯甲酸杂质, 不能作为 合格产品被正常应用, 必须经过精制工序除去杂质。
精制工序是这样的:粗间苯二甲酸在高温高压条件下用热水溶解,送入加氢反应 器, 在钯-碳催化剂的作用下进行加氢反应, 将间位羧基苯甲醛(3- CBA)还原为间位 甲基苯甲酸。间位甲基苯甲酸在水中的溶解度比间苯二甲酸高很多,通过水溶液中间 苯二甲酸的再结晶,基本实现间苯二甲酸与间位甲基苯甲酸的分离。间苯二甲酸结晶 经过离心分离、 过滤,得到滤饼, 再经过干燥、 水洗、 离心分离、 过滤、 干燥, 得到 精间苯二甲酸 (PIA) 产品。 水溶液中剩余的间位甲基苯甲酸和少量间苯二甲酸经过 提浓、 脱水之后返回氧化反应器。
PIA生产过程中加氢精制工序消耗大量热能,其燃料动力能耗约占 PIA生产总能 耗的一半以上。
现在的氧化反应器主要有两种形式,一是气液固三相搅拌釜反应器;二是鼓泡塔 浆料反应器。精间苯二甲酸(PIA)生产工艺中氧化反应器液相温度一般控制在 170〜 220°C。 有机溶剂醋酸和目标产品间苯二甲酸在反应器内停留时间比较长, 原料间二 甲苯消耗和溶剂醋酸消耗相对比较高。本发明则设法降低醋酸溶剂所处的反应环境温 度,缩短醋酸和目标产品间苯二甲酸在反应器内的停留时间,所以原料间二甲苯消耗 和溶剂醋酸消耗相对比较低。
在氧化反应温度 170〜220°C的条件下, 间苯二甲酸在醋酸溶液中的饱和溶解度 只有 0. 1〜0. 8%左右。
已有的研究表明,从间二甲苯到间苯二甲酸的氧化反应是串联反应,主要经历四 个反应过程,一是从间二甲苯到间位甲基苯甲醛;二是从间位甲基苯甲醛到间位甲基 苯甲酸; 三是从间位甲基苯甲酸到间位羧基苯甲醛(3- CBA); 四是从间位羧基苯甲醛 到间苯二甲酸。 四种氧化反应均是不可逆反应。
现有的 PIA、 PTA生产工艺中, 氧化反应器中氧化反应热的撤出主要采用的是溶 剂醋酸和水的闪蒸。 闪蒸的醋酸和水随尾气进入冷凝系统, 经过换热, 部分凝液进入 反应器,大部分醋酸和水被回收进入各自储罐,部分回收的醋酸和水被补加进入反应 器
本发明通过新设计的反应流程,控制反应条件,使得间苯二甲酸结晶时反应物液 相没有 3-CBA和间位甲基苯甲酸, 从而简化了生产工艺, 降低生产成本,提髙产品质
S o
采用本发明方法生产的间苯二甲酸产品质量超过现在的 PIA产品质量, 其中 3-CBA和间位甲基苯甲酸的含量可以达到零。 这种产品可以称为精精间苯二甲酸, 英 文速写为 PPIA。 这种精精间苯二甲酸(PPIA) 产品更适合作为食品包装材料、 饮料 瓶材料、 医药包装材料, 以及医疗器材的聚合物原料, 因为它的甲醛基含量极低, 具 有更安全无毒害的优越性。
如果对产品质量进行让步放行, 即按照现在 PIA的产品质量标准组织生产,则采 用本发明的技术时, 间二甲苯原料和醋酸溶剂的消耗指标将进一歩降低。
采用本发明技术生产精间苯二甲酸, 省略了加氢精制工序, 设备投资节省; 燃 动能耗降低约 50%, 平均每吨精间苯二甲酸产品节约综合能耗(不含原料)约 100公 斤标准原油; 避免使用昂贵的钯 -碳催化剂; 产品质量提高。 综合前面述及的间二甲 苯原料消耗降低, 醋酸溶剂消耗降低的因素, 预计在原油价格 110美元 /桶、 人民币 兑换美元的汇率为 7比 1的条件下,本发明与现在的生产工艺技术相比,精间苯二甲 酸生产成本可以节约 500〜1000元 /吨。 发明内容
本发明新的生产工艺 ώ间二甲苯氧化反应、 间苯二甲酸结晶、 分离、 过滤、 干 燥; (必要时, 增加对间苯二甲酸晶体的醋酸洗涤除去钴、 锰离子催化剂, 再经过分 离、 过滤、 干燥); 间苯二甲酸晶体水洗、 分离、 过滤、 干燥, 以及催化剂回收、 溶 剂回收和尾气处理几个主要部分组成。作为优化方案,可以省略以脱除有机溶剂醋酸 为目的的第一次"干燥"工序。作为优化方案, 可以省略以脱除有机溶剂醋酸为目的 的第二次 "千燥"工序。
氧化反应以间二甲苯为主要原料, 以压缩空气或者其它含氧气体(例如氧气) 中的氧气或者其它含氧气体(例如氧气)为辅助原料, 以醋酸为初始溶剂, 以醋酸钴、 醋酸锰为催化剂, 以氢溴酸为辅助催化剂,在随反应流程变化的温度条件下进行氧化 反应。 氧化反应后期以水作为辅助溶剂。
氧化反应分为从间二甲苯到间位甲基苯甲酸和从间位甲基苯甲酸到间苯二甲酸 两个主要区域。 两个区域的温度、 压力可以各不相同, 也可以温度不同而压力相同, 具体情况取决于对反应器结构的选择。
1、 本发明的目的:
釆用新的间二甲苯氧化工艺, 使氧化反应得到的中间产品粗间苯二甲酸(结晶 体) 中不含现在生产工艺不可避免的主要杂质: 3-羧基苯甲醛 (3- CBA)和间位甲基苯 甲酸, 省略为了消除这两种杂质而设立的 "精制 "生产工序, 降低原料消耗和醋酸溶 剂消耗, 降低燃料动力能源消耗, 减少水的消耗, 提高产品质量, 避免使用昂贵的钯 -碳催化剂, 从而节约生产成本。 对于建设新的 ΡΙΑ生产装置, 则可以节约大笔 "精 制"投资成本。
2、 氧化反应流程:
根据本发明的目的, 理想的物流状态是按照从间二甲苯到间苯二甲酸串联反应 的各个歩骤, 使物流形成上下游关系, 物流中氧化反应按照串联反应的顺序进行。
在设计具体反应流程时, 本发明设计了近似于平推流或者活塞流的反应流程或 者局部的近似于平推流或者活塞流的反应流程,使反应器内部液相物流存在上下游关 系,实现了目标氧化产物间苯二甲酸所在的出料口区域与原料间二甲苯进料口区域的 有效分隔,这种分隔不是在空间上完全封闭,而是在反应过程中两个区域的物料无法 直接相互混合。在近似的平推流或者活塞流流程段,氧化反应基本上按照从间二甲苯 到间苯二甲酸串联反应的先后次序进行,即新添加进入反应器的原料间二甲苯不会进 入串联反应的末段参加反应。氧化反应目标产物间苯二甲酸的髙浓度区域不会与反应 原料间二甲苯混合。最终间苯二甲酸溶液的出口区域不会与反应原料间二甲苯以及各 种氧化反应中间产物混合。 N2009/000486 这种新的氧化反应流程的实质是将串联氧化反应的四个主要反应分段进行, 即 分段氧化,从而可以针对各个反应阶段的有机原料相的物理性质分别控制相应的反应 条件。
( 1 )、 分段控制温度, 温度梯度为 130〜35(TC ;
(2)、 分段补充溶剂, 混合溶剂中醋酸和水的比例根据不同补充位置而不同, 水在混合溶剂中的比例从 0〜 100%;
(3)、 分段控制溶液浓度, 反应物浓度为 5〜50%, 典型的反应物浓度为 28%;
(4)、 分段送入压缩空气或者其它含氧气体 (例如氧气);
(5)、 分段添加不同催化剂, 或辅助催化剂。
这种分段不是截然分段, 而是相对分段。 即: 在反应器中, 间二甲苯、 间位甲 基苯甲醛、间位甲基苯甲酸、间位羧基苯甲醛、间苯二甲酸等存在明显的高浓度区域, 高浓度区域之间存在浓度过渡区, 高浓度区域依串联氧化反应的次序出现。
在低温氧化段, 主要目标氧化产物是间位甲基苯甲酸, 只在原料和溶剂中添加 醋酸钴、酉§酸锰催化剂。在开始氧化第二个甲基的反应器或者反应器区域, 也就是在 间位甲基苯甲酸髙浓度区域, 添加氢溴酸作辅助催化剂, 以水作为辅助溶剂。
这种分段氧化反应流程可以在几个反应器之间实现, 也可以在一个反应器内部 实现。
3、 氧化反应器及其结构:
( 1 )、 本发明设计了具有内、 外室结构的氧化反应器, 采用一个内置的与反应 器同轴心的圆筒将反应器分隔成内外两个室, 圆筒底部与反应器内壁底部连接, 圆筒 上边浸没在液相物料液位下面, 内外室裤相物料在圆筒上边通联。混合的反应物料包 括原料、溶剂、 催化剂等从内室底部进料, 内室物料上行, 从液相顶部进入外室, 外 室物料下行。在这个反应器的外室, 物料处在近似于平推流的流程段,氧化反应基本 按照串联氧化反应的次序进行。液相反应物料在内室与外室形成上下游关系。各室气 相相通, 有利于通过溶剂闪蒸从反应器内部撤出反应热。作为替代方案,进料口位置 可以设置在外室底部, 出料口位置设置在内室底部。
(2)、 本发明设计了具有内、 中、 外三室结构的氧化反应器, 釆用两个内置的 与反应器同轴心的圆筒将反应器分隔成内中外三个室,一个圆筒底部与反应器内壁底 部连接, 圆筒上边浸没在液相物料液位下面, 液相物料在圆筒上边通联; 另一个圆筒 下边悬空, 依靠点支撑固定在反应器主体的底部内侧,侧面与反应器内壁或者另外一 个圆筒形成支撑加以固定。圆筒上边将液相液面有效分隔,液相物料在圆筒下边通联。 在这个反应器的中室和外室,物料处在近似于平推流的流程段,氧化反应基本按照串 联氧化反应的次序进行。液相反应物料在内室、 中室和外室形成上下游关系。各室气 相相通, 有利于通过溶剂闪蒸从反应器内部撤出反应热。作为替代方案,进料口位置 可以设置在外室底部, 出料口位置设置在内室底部。
(3)、本发明还可以采用 3个、 4个乃至更多内置的与反应器同轴心圆筒分室的 4室、 5室、 多室氧化反应器, 液相物料依照圆筒大小的次序分别从圆筒上部和下部 与临近的室通联,有效分隔原料进料口与反应物料出料口,有效形成液相物料流上下 游关系; 各室气相相通, 有利于通过溶剂闪蒸从反应器内部撤出反应热。
(4)、 本发明设计了卧式平推流氧化反应器, 在这个反应器内部, 物料处在近 似于平推流的流程,液相反应物料形成上下游关系,氧化反应基本按照串联氧化反应 的次序进行。采用薄片螺旋推进轴缓慢推进物料,物料流动方向与推进轴推进方向相 同,有利于反应过程中产生的少量间苯二甲酸晶体被推送到高温段溶解, 同时薄片螺 旋推进轴可以起到动态分室的作用,降低低温段物料与高温段物料因为温差而产生的 相互之间的对流。
( 5 )、 本发明设计了塔式活塞流氧化反应器, 在这个反应器内部, 物料处在近 似于活塞流的流程, 氧化反应基本按照串联氧化反应的次序进行。
(6)、 本发明设计了采用多反应器串联的氧化反应器组合, 在这个反应器组合 内部, 反应物料存在上下游关系, 局部物料处在近似于平推流的流程,氧化反应基本 按照串联氧化反应的次序进行。
4、 压缩空气或者其它含氧气体(例如氧气)供给量:
压缩空气或者其它含氧气体 (例如氧气) 分多股进入反应器, 或者使用环形空 气分布器送入压缩空气或者其它含氧气体 (例如氧气)。 总的空气流量根据间二甲苯 流量及反应器尾气氧浓度设定, 以保证尾气排出反应器尾气冷却器时氧浓度为 3〜4% 或者更低。
压缩空气或者其它含氧气体(例如氧气) 供应, 可以按照液相容积均勾供气, 也可以不均勾供气。
在具有内、 外室结构的氧化反应器外室, 当出料口设在外室底部时, 采用环形 空气分布器从底部供气,可以设计压縮空气或者其它含氧气体(例如氧气)供给过量, 使液相氧气浓度比较高, 用于氧化间位甲基苯甲酸, 提高从间位甲基苯甲酸到 3-CBA 的反应速度, 整个串联氧化反应的速度因此加快, 溶剂消耗因此降低。单位容积的生 产能力增加。
作为优化方案, 具有内、 外室结构的氧化反应器, 外室单位液相容积压缩空气 或者其它含氧气体(例如氧气)的供应量超过反应器液相体积平均压缩空气或者其它 含氧气体(例如氧气)供应量, 这样做有三个考虑, 一是过量供应压缩空气或者其它 含氧气体(例如氧气)满足外室氧化需要。二是过量的空气有利于提高该区域氧化反 应速度。三是过量空气不会造成安全问题, 因为过量空气只存在于外室下部, 到达中 部,则过量的空气会经过鳃状栅进入内室,与内室液相充分混合,参与内室氧化反应, 从而不会因为这部分压缩空气或者其它含氧气体(例如氧气)中的氧气没有得到充分 应用而增加尾气中氧的含量,造成压缩空气或者其它含氧气体(例如氧气)资源浪费。
控制进入氧化反应器的间二甲苯、 压缩空气或者其它含氧气体 (例如氧气) 的 流量, 可以确保从反应器排出的间苯二甲酸溶液中没有间位羧基苯甲醛 (3- CBA)和间 位甲基苯甲酸。 间位羧基苯甲醛 (3-CBA)和间位甲基苯甲酸在到达氧化反应器出料口 区域之前被完全氧化为间苯二甲酸。
对于塔式氧化反应器, 在液相底部利用空气分布器供气。 作为优化方案, 可以 设置两组或者两组以上的空气分布器,其中第一组留在底部,其它组与第一组间隔一 段距离设置。依次类推,可以在塔式氧化反应器内设置三组或者四组压缩空气或者其 它含氧气体(例如氧气)分布器。其中底部的空气分布器可以在环形中间增加十字形, 作为优化的空气分布器。
环形压缩空气或者其它含氧气体 (例如氧气) 分布器以反应器轴心为中心, 压 缩空气或者其它含氧气体(例如氧气)出气孔分别向径向各个方向幵孔, 以便空气或 者其它含氧气体(例如氧气)分布更加均匀。小的环形分布器中间可以加设十字形分 布器, 十字与圆环在同一平面。
5、 尾氧利用技术:
以采用单台塔式氧化反应器为例, 增加液相顶部低温氧化区域的液位高度。 从 液相底部进入反应器的压縮空气或者其它含氧气体 (例如氧气), 其尾气在出液相进 入反应器气相之前经过的液相反应物料是刚进入氧化反应器的新鲜反应原料间二甲 苯、 醋酸溶剂、 催化剂和辅助催化剂混合物料, 在温度相同物料浓度相同的条件下, 例如在温度 130〜210°C,典型温度 160Ό条件下,这个区域的物料是最容易被氧化的 物料,氧化反应需要的活化能比较低,可以跟压缩空气或者其它含氧气体(例如氧气) 尾气中残留的浓度很低的氧气发生反应,从而降低尾气中氧气的含量,尾氧含量可以 从现在控制的 3〜4%降低到 1〜2%, 甚至更低, 提高压缩空气或者其它含氧气体 (例 如氧气) 的利用率, 空气压缩机的效率提高 10%, 甚至更高。
6、 反应温度和压力:
本发明根据选用的不同氧化反应器, 分段控制氧化反应条件, 氧化反应温度分 别为 130〜210°C, 180〜250。C和 210〜350°C, 典型温度区间是 145〜288°C。 典型的 低温段温度和压力分别是 160Ό和 0. 5MPaG, 典型的中温段温度和压力分别是 25(TC 和 5. OMPaG, 典型的高温段温度和压力分别是 288°C和 7. 5MPaG。
氧化反应器压力对应于反应器内高温区域液相物料的饱和蒸汽压。 反应器压力 通过控制压缩空气或者其它含氧气体(例如氧气)进气量和反应器尾气冷凝系统不凝 气出口调节阀的开度加以控制。系统控制以温度为优先要素, 压力为次要因素。压力 作为安全检测和控制要素。对于同一反应器内部存在不同温度区域的情况,压力控制 略高于高温区域的饱和蒸汽压,使得高温区域不至于沸腾,避免强化高温区域与低温 区域的物料对流。
与现在的生产工艺相比, 虽然局部反应温度会很高, 但是这个区域的水含量也 很高, 所以不会造成剧烈的氧化反应发生。通过平衡水含量和温度提升的幅度, 达到 控制反应速度的目的, 同时减少副反应, 降低醋酸溶剂的消耗。
作为替代方案,反应器出料口区域的温度可以设定在更高的位置,例如: 400〜 500°C。 此时, 混合溶剂中没有醋酸只有水, 氧化反应停留时间更短。
7、 催化剂:
催化剂醋酸钴、醋酸锰、辅助催化剂氢溴酸可以按照多种比例进行组合,例如 1 : 1: 1、 1: 2: 3, 或者 1 : 2. 5 : 1 , 等等。 典型的比例是 1 : 1: 1。 催化剂浓度 (钴、 锰、 溴离子总质量含量)范围是 300〜3000ppm (催化剂 /有机原料相 +溶剂), 典型浓 度是 1050ppm。常规的催化剂添加方法是将三种催化剂和催化剂助剂与原料、溶剂(包 括回收的催化剂、 溶剂)一起混合添加进入氧化反应器。
作为优化方案有两个做法:
一是在间二甲苯氧化到间位甲基苯甲酸的反应区间只添加醋酸钴、 醋酸锰催化 剂, 在开始氧化第二个甲基时添加氢溴酸作为辅助催化剂;
二是控制反应物料中催化剂的浓度,按照串联反应的各个歩骤逐步降低催化剂、 助剂浓度, 形成浓度梯度。 例如, 初始催化剂浓度为 1050ppm, 最终反应物出口催化 剂浓度为 0Ppm, 降低催化剂消耗。 典型的催化剂浓度分布是从初始 1050ppm到最终 反应物出口浓度为 600ppm。
8、 溶剂:
初始溶剂是醋酸, 辅助溶剂是水。 随着串联氧化反应的流程, 醋酸在醋酸与水 组成的混合溶剂中的比例逐歩降低, 形成梯度, 水的比例逐歩增加。溶剂中, 醋酸的 比例从 100%逐歩降低到 0%。水的比例从 0%逐歩增加到 100%。典型的溶剂梯度是醋酸 比例从初始的 95%逐步降低到 20%。
向反应器添加大量的水作为间苯二甲酸的溶剂和 3- CBA的溶剂以及间位甲基苯 甲酸的溶剂, 使得氧化反应得到的目标产品间苯二甲酸能够被充分溶解, 中间产物 3-CBA也能够充分被溶解, 以便被进一歩氧化为间苯二甲酸。
9、 反应物浓度:
溶质是液相有机原料相, 即从间二甲苯到间苯二甲酸串联反应的原料、 产物及 其所有中间产物,溶剂是醋酸和水组成的混合溶剂。反应物液相浓度的控制根据选择 的氧化反应器结构不同、 氧化反应热的撤热方式不同有四种形式。
( 1 )、 氧化反应器主要采用溶剂闪蒸的方法撤热, 则需要不断向反应器补充添 加溶剂。液相物料组成不同的区域, 添加的混合溶剂的组成比例也不同。在间二甲苯 到生成间位甲基苯甲酸区间, 补充添加的混合溶剂中醋酸比例是 100〜50% (有条件 时, 尤其是在平推流反应器中, 这段区域的添加溶剂浓度是醋酸比例从 100%逐歩降 低到 50%, 比例梯度分布), 典型的混合溶剂醋酸比例是 95%。即使是添加单一比例的 混合溶剂, 由于液相不断发生氧化反应产生副产物水, 不考虑溶剂闪蒸的因素, 混合 溶剂中醋酸的比例也是梯度变化的。从间位甲基苯甲酸到间苯二甲酸区间,补充添加 的混合溶剂中醋酸的比例是 50〜0% (有条件时, 尤其是在平推流反应器中, 这段区 域的添加溶剂浓度是醋酸比例从 50%逐步降低到 0%, 比例梯度分布), 典型的混合溶 剂醋酸比例是 20%。
由于主要采用氧化反应器内部溶剂闪蒸的方法撤热, 这种情况下最终氧化反应 器出料口区域溶液的浓度较高, 需要注意控制浓度不超过简本二甲酸的饱和溶解度。
(2 )、 氧化反应器主要采用出料口大量排出高温低浓度溶液的方法撤热。 如鼓 泡塔式氧化反应器,反应器内部反应热的撤出和温度平衡,釆用向系统添加低温溶剂 的方法, 通过溶剂升温吸热, 稳定液相物料的温度。采用这个方法, 液相物料沿串联 反应的方向浓度逐步降低。 比照上节(1 ), 本反应器各反应阶段因为浓度降低, 所以 温度相对提高,抵御反应物浓度降低引起的反应速度降低的趋势,适当增加反应速度, 弥补反应物料停留时间缩短造成的反应时间不足。大量低浓度反应产物从出料口出料 进入结晶器闪蒸, 回收热能脱出溶剂提高浓度, 结晶析出间苯二甲酸。必要时在结晶 器和反应器之间再增加一个闪蒸罐, 专门用于溶液浓缩,配合换热器回收热量。或者 在进入结晶器之前, 溶液先经过换热器换热回收热能, 然后再去结晶器闪蒸。
这种撤热方法, 对比依靠氧化反应器内部溶剂闪蒸撤热的方法, 可以回收的氧 化反应热量是相同的。由于氧化反应末端温度比较高,这种方法回收的热量可以用于 产生高等级的蒸汽。
(3)、 对于塔式氧化反应器, 除了采用上节(2)所述的撤热方法之外, 还可以 采用内置盘管换热撤热的方法。盘管内部流动冷却介质。由于间苯二甲酸在溶液中的 溶解度对温度敏感,所以这种冷却盘管不要设置在间苯二甲酸的高浓度区,如果要设 置到间苯二甲酸高浓度区,则这段盘管内部介质的温度与盘管外溶液的温度差别不能 太大, 盘管外表温度不能低于反应器该区域溶液浓度作为饱和溶液浓度所对应的温 度。 否则会在盘管外表面形成间苯二甲酸结晶。
作为辅助的撤热措施, 在塔式氧化反应器外壁缠管, 使用冷却介质换热撤热。 ( 4)、 上述三种撤热措施的混合使用。
10、 实施本发明的步骤:
( 1 )、 原料:
氧化反应以间二甲苯为主要原料, 以压縮空气或者其它含氧气体(例如氧气) 中的氧气或者其它含氧气体为辅助原料, 以醋酸为初始溶剂, 以醋酸钴、醋酸锰为催 化剂, 以氢溴酸为辅助催化剂, 氧化反应后期以水作为辅助溶剂。
本发明 "有机原料"或者 "有机原料相"是指间二甲苯和间苯二甲酸以及从间 二甲苯到间苯二甲酸的各种氧化反应中间产物的总和。
( 2)、 氧化反应步骤:
反应温度分段分别为 130〜210°C左右和 180〜250°C左右, 以及 210〜350°C左 右, 分段控制。本发明氧化反应压力为 0. 5〜14. 0MPaG左右。典型的低温段温度和压 力分别是 160Ό和 0. 5MPaG;典型的中温段温度和压力分别是 250°C和 5. OMPaG;典型 的高温段温度和压力分别是 288Ό和 7. 5MPaG。 温度通过控制闪蒸进入反应器顶部换 热器(冷凝器)的溶剂和水的量、凝液回流量、结晶器醋酸溶剂和水溶剂闪蒸撤热量、 补充进入反应器的水和醋酸的温度与量、压縮空气或者其它含氧气体(例如氧气)的 进气量、氮气和二氧化碳的排出量, 间苯二甲酸溶液从出料口出料带出反应器内的热 量, 以及反应热等进出反应器的全部热量综合平衡来实现。
反应器压力通过控制压缩空气或者其它含氧气体 (例如氧气)进气量和反应器 尾气冷凝系统不凝气出口调节阀的开度加以控制。温度是第一要素,压力配合温度要 求而设定。
间二甲苯与溶剂醋酸、 催化剂醋酸钴、 醋酸锰、 辅助催化剂氢溴酸混合后添加 到氧化反应器低温段, 在 130〜210°C温度条件下氧化, 主要生成间位甲基苯甲酸。
这个阶段的温度的平衡釆用两种方法, 一种是溶剂闪蒸, 经过反应器顶端的冷 凝器换热撤热; 另一种方法是向反应器添加低温醋酸和少量水构成的混合溶剂,通过 溶剂温度上升, 吸收反应热, 平衡反应器温度。
在间位甲基苯甲酸被氧化为间苯二甲酸的反应阶段, 向反应器液相添加水作为 补充溶剂,以控制间苯二甲酸在溶液中的浓度不超过饱和溶解度,同时提高反应温度, 遏制因为反应物浓度降低而引起的反应速度下降的趋势。提高反应物液相温度和增加 溶剂水的含量,是增加反应器液相间苯二甲酸溶解度和溶解量的有效措施。这个区域 的温度可以控制在 210〜350°C, 较好的温度区间为 246〜288°C。
为了撤出反应热, 必要时向反应器添加大量的水, 使得反应器区域温度不会继 续上升,该区域间苯二甲酸在溶液中的浓度可能远远低于饱和溶解度,有机原料氧化 反应的难度会增加。为了使得反应得以顺利进行, 则需要提高反应温度,使得温度的 提升与浓度的降低对反应速度的影响达到一个平衡。 例如间位甲基苯甲酸浓度为
25〜1%, 反应温度为 180〜240°C,水在溶剂中的含量为 6〜50%。间位甲基苯甲酸浓度 为 1〜0. 1%, 反应温度为 250〜288°C, 水在溶剂中的含量为 50〜100%。 反应温度提 髙, 有机原料浓度不变或者也提高时, 则反应速度提高。
另一方面, 当反应温度上升到 250〜288°C时, 间苯二甲酸在水溶液中对应的饱 和溶解度约为 3〜50%, 高温条件使得提高有机原料溶液的浓度成为可能(低温条件 下可能会析出结晶)。 所以在高温、 高有机原料浓度的情况下, 可以进一步降低混合 溶剂中醋酸的比例,增加混合溶剂中水的比例;进一步降低催化剂和辅助催化剂的浓 度。 即便如此,氧化反应仍然可以顺利进行, 因为提高温度增加了有机原料的氧化反 应能力。
在高温氧化区域,水在溶剂中的典型比例是 80%;催化剂钴锰溴的典型比例是钴: 锰: 溴为 1 : 1: 1 , 典型离子浓度(质量比)是 600ppn 典型的间苯二甲酸浓度(间 苯二甲酸 /间苯二甲酸 +水 +醋酸) 是 20%; 典型温度是 288°C。
从反应器结构设计着手, 将氧化反应的目标产物间苯二甲酸与间二甲苯和其它 中间产物有效分隔,避免间苯二甲酸结晶时物料中存在 3- CBA和间位甲基苯甲酸,也 减少反应生成物间苯二甲酸因停留时间较长而被过度氧化造成的原料损失。
从氧化反应器得到的间苯二甲酸溶液送往结晶器, 间苯二甲酸只在结晶器结晶, 在结晶器得到相对纯净的间苯二甲酸固体。
进入结晶器的氧化反应物料中, 没有间二甲苯、 没有间位甲基苯甲醛、 没有间 位甲基苯甲酸、 没有间位羧基苯甲醛 (3- CBA) , 它们在离开氧化反应器之前已经完全 被氧化成间苯二甲酸。
从生产工艺的优化出发, 在有效形成液相反应物料上下游流程的情况下, 通过 控制反应条件,在氧化反应器内部反应物物流末端形成间苯二甲酸固体结晶也是可以 的。形成间苯二甲酸结晶时,该局部区域不能存在 3- CBA和间位甲基苯甲酸的原则不 变; 间苯二甲酸结晶体离开反应器的出口区不含 3- CBA和间位甲基苯甲酸的原则不 变。此种情况, 反应器出料口设在反应器底部或者侧面下部为好, 以便于结晶固体排 出反应器。
随着反应器区域温度的不同, 醋酸和水的比例不同, 间苯二甲酸在醋酸和水混 合溶剂中的饱和溶解度也不同。 当液相温度为 250〜288°C时, 控制间苯二甲酸的浓 度在 2〜45%之间是安全的, 溶液不容易形成意外结晶。 比较好的温度与浓度控制是: 温度为 286〜288°C, 间苯二甲酸溶液浓度为 30%。在氧化反应器各项反应条件控制稳 定的前提下,可以设计间苯二甲酸在氧化反应器内部浓度达到饱和溶解度,并且不断 析出间苯二甲酸结晶。 部分反应热在反应器内部通过溶剂和水的闪蒸撤出, 在反应器顶部的冷凝器换 热, 回收热量。部分反应热通过结晶系统溶剂闪蒸撤出, 闪蒸的溶剂通过换热器回收 热量。为了平衡这种反应热撤出的需要, 需要大量不断地向反应器内添加水溶剂。必 要时,需要在补充溶剂水时添加被水溶剂带出反应器的回收利用的催化剂,避免溶液 被稀释得不能进行氧化反应。低温水进入反应器取热, 高温水进入结晶器闪蒸, 从而 可以撤出热量。
选择不同的氧化反应器, 两种撤热方式撤出的热量比例不同。 有时反应器内部 溶剂闪蒸撤热比例大于结晶器溶剂闪蒸撤热,例如氧化反应器组合。有时结晶器溶剂 闪蒸撤热比例大于反应器内部溶剂闪蒸撤热,例如近似于活塞流流程的塔式氧化反应 翁。
以具有内、 中、 外室结构的氧化反应器为例陈述氧化反应的步骤:
内中外三室液相容积的比例是内: 中: 外为 1: 2: 3。 内、 中、 外三室底部分别 设置空气分布器。 原料、 溶剂、 催化剂混合后, 从内室底部进料。
在反应器内室, 控制反应温度, 使得氧化反应的内容主要是间二甲苯氧化为间 位甲基苯甲醛和间位甲基苯甲醛氧化为间位甲基苯甲酸。 在内室温度条件下, 例如 155〜160°C时, 间位甲基苯甲酸氧化为间位羧基苯甲醛 (3- CBA) 的难度较大, 尤其 是在缺少辅助催化剂氢溴酸的条件下。 内室的温度平衡采用向内室补充添加 30Ό低 温醋酸和水混合溶剂的方法。内室液相物料与中室液相在小圆筒上部通联。辅助催化 剂氢溴酸随辅助溶剂水添加在中室液相上部, 大量的间位甲基苯甲酸氧化为 3- CBA 和 3-CBA氧化为间苯二甲酸的反应在中室和外室液相下部进行。少量的间二甲苯到间 位甲基苯甲醛的氧化反应和间位甲基苯甲醛到间位甲基苯甲酸的氧化反应发生在中 室下部,外室上部实际是间苯二甲酸的饱和氧化区域,彻底消除 3- CBA和间位甲基苯 甲酸。 中室和外室有机原料相的浓度比初始投料浓度低, 而且溶剂中水的比例高, 所 以尽管温度高, 但是氧化反应速度稳定受控。 中室和外室的温度控制在 288°C。 中室 和外室的反应热通过溶剂闪蒸撤出, 闪蒸的溶剂进入反应器顶端的换热器冷凝, 回收 热量,大部分凝液回收分别送往醋酸和水的储罐。由于外室上部容积占全反应器液相 的比例较小,所以与原 PIA生产工艺相比, 间苯二甲酸在氧化反应器液相的停留时间 缩短,被过度氧化成二氧化碳增加原料间二甲苯消耗的机会减少。反应物料出料口设 在外室上部, 最终反应产物间苯二甲酸溶液从出料口出料, 送往结晶系统。
与原来的 PIA生产技术相比, 在反应器容积相同的前提下, 采用本发明内、 中、 外三室结构的反应器的反应速度加快,物料总体停留时间缩短,产量增加,有机原料、 有机溶剂消耗降低, 燃料和动力消耗降低。
(3)、 结晶- 在结晶器, 通过减压降温, 水和醋酸溶剂不断闪蒸, 间苯二甲酸浓度增加而饱 和溶解度系数随温度降低而降低, 间苯二甲酸不断从溶液中析出, 晶粒缓慢增大。结 晶器设置搅拌器, 使得晶粒尺寸相对均匀。 由于溶液中没有间位羧基苯甲醛 (3- CBA) 和间位甲基苯甲酸, 所以间苯二甲酸结晶体中不会含有间位羧基苯甲醛 (3-CBA)和间 位甲基苯甲酸两项杂质。
经过多级结晶逐歩降温, 例如 3〜7级结晶, 绝大部分间苯二甲酸固体与溶剂和 催化剂以及其它杂质分离。每级结晶器温差 20〜58°C,较好的温度级差为 21〜38°C。 终级结晶器温度 100〜180°C。 结晶级数增加, 有利于回收高温热量, 提高副产蒸汽 的等级。
氧化反应产生的部分热量通过闪蒸于尾气中的醋酸溶剂和水带走。 与现有工艺 不同的地方是,对应于个别氧化反应器结构,有更多反应热通过溶剂在结晶器内的闪 蒸被撤出。
结晶系统回收的水和醋酸分别进入水和醋酸的回用系统。
(4)、 其它步骤:
间苯二甲酸结晶经过离心分离、 过滤、 干燥(脱出残留的醋酸溶剂), 然后经过 水洗,脱除水溶性杂质,再经过离心分离、过滤、干燥,得到精间苯二甲酸产品(PIA) 或者精精间苯二甲酸产品 (PPIA)。
或者, 对于低浓度间苯二甲酸溶液, 由于醋酸在溶剂中的比例很低, 以脱除醋 酸为目的的第一次 "干燥"工序可以省略。
11、 本发明的技术优势:
( 1 )、 降低间二甲苯原料消耗;
(2)、 降低醋酸溶剂消耗;
(3 )、 降低燃料动力能源消耗;
(4)、 减少水的消耗;
(5)、 减少催化剂和辅助催化剂的消耗;
(6)、 避免使用昂贵的钯 -碳催化剂;
( 7 )、 降低尾气中氧气的含量, 提高压縮空气或者其它含氧气体 (例如氧气) 的利用率;
(8)、 提高产品质量。
其中, 提高产品质量并不是本发明的主要目的。
12、 本发明的技术特点:
( 1 )、 控制氧化反应条件, 配合结晶系统, 使得氧化反应的目标产物间苯二甲 酸在结晶成固体的时刻, 该结晶区域反应体系物料中的间二甲苯、 间位甲基苯甲醛、 间位甲基苯甲酸、 3-羧基苯甲醛 (3- CBA)都已经被氧化成间苯二甲酸, 所以结晶得 到的中间产品粗间苯二甲酸中没有 3-羧基苯甲醛(3-CBA)和 ί 位甲基苯甲酸两项杂 质。
采用具有能够分隔原料间二甲苯和氧化反应目标产物间苯二甲酸的氧化反应器 结构或者反应器组合,建立分段氧化或者基本按照串联反应次序氧化的流程和反应条 件, 使得从原料间二甲苯到产物间苯二甲酸, 反应物料形成上下游关系。
以间二甲苯为原料, 以醋酸为初始溶剂, 水为辅助溶剂, 采用醋酸钴、 醋酸锰 为催化剂, 氢溴酸为辅助催化剂, 将原料、溶剂和辅助溶剂、催化剂和辅助催化剂混 合后添加到氧化反应器或者氧化反应器组合, 吹入压縮空气或者其它含氧气体(例如 氧气)或者含氧气体, 在 130〜350°C温度下反应 15〜150min, 得到间苯二甲酸溶液。 反应器压力为 0. 5〜14MPaG。
间苯二甲酸溶液经过换热器冷却 (回收热量)、 闪蒸罐浓缩(回收热量)、 多级 结晶 (回收热量)、 分离、 过滤、 水洗、 分离、 过滤、 干燥工序, 得到精间苯二甲酸
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初始反应物料中催化剂钴、 锰、 溴三种离子的总质量浓度为 300〜3000ppm, 钴 锰原子比为 30〜0. 3, 钴锰离子总浓度与溴离子的原子比例为 0. 5〜2. 5。
(2)、 采用下列氧化反应器或者氧化反应器组合:
①、 具有内、 外室结构的氧化反应器, 釆用内置的与反应器同轴心的圆筒将反 应器分隔成内外室, 内外室液相在圆筒顶部通联, 圆筒将外室底部物料出口与内室底 部原料进口有效分隔,内外室单位液相容积的压缩空气或者其它含氧气体 (例如氧气 ) 供给量相同; 采用环形空气分布器; 采用环形水分布器。
或者, 外室的单位液相容积压缩空气或者其它含氧气体(例如氧气)供给量大 于内室, 过量的压缩空气或者其它含氧气体(例如氧气) 经过鳃状栅进入内室。
或者, 内室采用树形水分布器。
树形水分布器主要由树干和树枝组成, 树干树枝内部均为水的通道, 树枝设出 水孔。 为了换热的需要, 树干可以设计成列管, 从液相反应物料中取热, 预热树干中 间的水。
②、 具有内、 中、 外三室结构的氧化反应器, 采用两个内置的与反应器同轴心 的圆筒将反应器分隔成内中外三个室, 中室和外室液相在大圆筒下边通联,外室上部 液相与中室上部液相有效分隔; 中室上部与内室上部在小圆筒上边通联, 中室下部与 内室下部原料进口有效分隔;外室上部反应器液相物料出口与内室下部原料进口有效 分隔; 采用环形空气分布器; 采用环形水分布器。
或者, 内室采用树形水分布器。 ③、 具有平推流反应流程的卧式氧化反应器, 反应器一端进料, 另一端出料。 终端液相与原料进料端液相物料无法任意混合,从反应器原料进料口到反应物料出料 口, 氧化反应基本按照串联氧化反应的次序进行。
作为优化措施, 采用螺旋薄片推进轴对反应物料液相进行动态分室。
④、 具有近似于活塞流反应流程的塔式氧化反应器是一长径比例为 6〜30的塔 式反应器, 内部分段设置环形压缩空气或者其它含氧气体(例如氧气)分布器和环形 进水分布器。 上部迸料, 下部出料。
或者, 采用树形水分布器。
⑤、 采用两个或者三个以上反应器串联的氧化反应器组合, 可以使得氧化反应 物料形成上下游关系,处于近似的平推流状态。两个常规氧化反应器可以实现分段氧 化反应工艺流程。三个以上常规氧化反应器可以使得氧化反应物料处于近似平推流的 状态。 采用一个 "具有内、 外室结构的氧化反应器", 或者一个 "具有内、 中、 外三 室结构的氧化反应器"与一个常规氧化反应器组合,可以很好地使得氧化反应物料处 于近似的平推流状态, 实现分段氧化的工艺流程。采用任意两个 "具有内、外室结构 的氧化反应器", 或者 "具有内、 中、 外三室结构的氧化反应器", 或者"塔式活塞流 氧化反应器", 或者 "卧式平推流氧化反应器"组合, 可以很好地使得氧化反应物料 处于近似的平推流状态, 实现分段氧化的工艺流程。例如: 一台具有近似活塞流的塔 式氧化反应器与一台具有内外室结构的氧化反应器组合;两台具有近似活塞流的塔式 氧化反应器组合。 等等。
第一氧化反应器的反应条件因此可以更加缓和, 降低反应温度, 降低醋酸溶剂 的消耗。第一氧化反应器得到的产物以间位甲基苯甲酸为主,少量的间苯二甲酸晶体 以及微量 3-羧基苯甲醛, 和少量间二甲苯。 第一氧化反应器的产物经过蒸发、 结晶、 分离、过滤, 得到间位甲基苯甲酸和少量间苯二甲酸晶体以及保留在物料中的钴、锰 催化剂和残留的含量约 10%的醋酸。 采用水作辅助溶剂对滤饼打浆, 采用高速泵将浆 料送入高温高压反应器。间位甲基苯甲酸在水中的溶解度很高,在浆料中基本上处于 溶解状态。浆料在进入高温高压的塔式或者具有内外室结构的第二氧化反应器后, 间 苯二甲酸晶体很快被溶解,晶体中包含的少量间位羧基苯甲醛很快被氧化成间苯二甲 酸。间位甲基苯甲酸也在第二氧化反应器被全部氧化成间苯二甲酸。第二氧化反应器 出料为间苯二甲酸的溶液, 溶剂以水为主, 存在少量醋酸, 醋酸的浓度为 0〜25%, 典型浓度为 15%, 间苯二甲酸的浓度为 5〜50%, 典型浓度为 30°/。。
⑥、 在(1 )和(2)所述的氧化反应器结构基础上, 采用 3个、 4个乃至更多内 置的与反应器同轴心的圆筒分室的 4室、 5室、 多室氧化反应器, 液相物料依照圆筒 大小的次序分别从圆筒上部和下部与临近的室通联,有效分隔原料进口与反应物料出 口, 有效形成物料流上下游关系; 各室气相相通, 有利于通过溶剂闪蒸从反应器内部 撤出反应热。
(3)、 由于实现了分段氧化, 以及基本实现了按照串联反应的次序进行氧化反 应, 因此可以控制氧化反应器或者氧化反应器组合内部不同区域的温度范围。
减少目标产物间苯二甲酸在氧化反应条件下的停留时间,降低间二甲苯的消耗。 从反应物料上游到下游形成从低到高的温度梯度, 其中: 从间二甲苯到间位甲 基苯甲酸的高浓度区为低温区域, 反应温度为 130〜210°C, 降低反应温度, 减少醋 酸溶剂在高温条件下的停留时间, 降低醋酸消耗。
中间过渡区间为中温区, 反应温度为 180〜288°C。
从间位甲基苯甲酸的高浓度区到间苯二甲酸溶液的区域为高温区域, 反应温度 为 210〜350°C。 提高高温区温度, 增加溶液的溶解度。
(4)、 向氧化反应器适当的区域添加水作为辅助溶剂, 逐步降低醋酸在混合溶 剂中的比例, 降低反应物有机原料相在反应物液相的浓度, 从而降低氧化反应活性, 使得氧化反应速度在反应物液相温度提高的情况下受控平稳, 减少醋酸溶剂的消耗、 增加间苯二甲酸在溶剂中的溶解度。尤其是在氧化反应的高温区域,增加混合溶剂中 水的比例和降低反应物料的浓度对控制反应速度、降低醋酸消耗、避免间苯二甲酸被 过度氧化有重要意义。间苯二甲酸被过度氧化成二氧化碳,会增加间二甲苯原料的消 耗。
从反应物料上游到下游, 水的含量由低到高形成梯度, 辅助溶剂水在混合溶剂 中的比例从初始的 0%到反应器出料口时增加到 100%。
采用环形水分布器。
作为优化方案, 在具有内外室结构的氧化反应器内室、 具有内中外三室结构的 氧化反应器内室, 以及塔式活塞流氧化反应器可以采用树形水分布器。
树形水分布器的树干水流方向是沿反应物料上下游方向, 从上游向下游流动, 一方面从上游取热撤热, 另一方面预热向下游供水的温度。
(5 )、 分段添加催化剂和辅助催化剂。
针对卧式平推流氧化反应器、 塔式活塞流氧化反应器, 采用同时添加催化剂醋 酸钴、醋酸锰和辅助催化剂氢溴酸的方法; 针对内外室结构氧化反应器、 内中外三室 结构氧化反应器、多反应器串联的氧化反应器组合, 采用先添加催化剂醋酸钴、醋酸 锰, 后添加辅助催化剂氢溴酸的方法。
(6 )、 在塔式氧化反应器液相顶部设置一个弱氧化反应区域。 所谓弱氧化反应 就是利用尾气中残余的氧气进行氧化反应,在尾气离开液相进入反应器气相之前,充 分吸收尾气中的氧气用于有效的氧化反应, 进一歩降低尾氧含量。 ( 7 )、 在氧化反应器内部大量生成间位甲基苯甲酸的位置前即开始少量逐步添 加辅助溶剂水,提高液相温度。在大量生成 3- CBA和间苯二甲酸的氧化反应区域液相 物料中添加更多的水作为间苯二甲酸和 3-CBA的辅助溶剂,进一步提高反应温度,增 加间苯二甲酸在水和醋酸混合溶剂中的溶解度参数, 使得反应生成的间苯二甲酸和 3 - CBA完全溶解在溶剂中。提高反应温度也弥补了 ώ于液相物料中增加水的含量, 反 应物有机原料相在溶液中浓度降低引起的氧化反应速度降低的趋势。
溶剂醋酸和辅助溶剂水、 催化剂、 辅助催化剂均循环使用。
在低温氧化区, 补充添加的醋酸溶剂中可以添加适量辅助溶剂水, 以及催化剂。 越接近上游, 补充的混合溶剂中醋酸比例越高, 混合溶剂中醋酸的比例是 100〜50%。
从间位甲基苯甲酸到 3- CBA反应区域的温度也可以适当提高, 提高串联氧化的 整体反应速度, 温度为 210〜350°C。
氧化反应器最低温度区域温度为 130〜160°C,最高温度区域温度达到 250〜350 。C , 温度从低到高形成梯度。
( 8 )、 添加到氧化反应器内部液相物料中的溶剂水, 可以采用列管换热的方式 加热, 列管内部通水, 列管出口是向反应器液相添加水作为辅助溶剂的位置, 列管的 进水端端面封闭, 采用横管向列管供水, 列管埋在反应物液相物流的上游, 外侧为反 应物液相物料, 从上游物料反应热中取热, 向下游物料供水。
(9 )、 氧化反应原料、 溶剂和催化剂、 助剂的混合物料可以采用预热进料的措 施,采用反应器内设列管换热进料的方法, 从反应物料流下游较高温度区域取热, 预 热后混合物料出列管进入反应器液相即具备反应所要求的温度条件。
具体实施方式
为了实现本发明的目的, 建造平推流或者活塞流氧化反应器或者氧化反应器区 域,使反应物料液相有机原料相形成上下游关系,有效地将最终氧化反应目标产物间 苯二甲酸与原枓间二甲苯以及中间产物间位甲基苯甲醛、 间位甲基苯甲酸、 3-CBA分 隔, 可以采用具有特殊结构的氧化反应器和多台反应器串联的氧化反应器组合。
1、 氧化反应器结构和氧化反应器组合:
①、 具有内、 外室结构的氧化反应器。
氧化反应采用具有内、 外室结构的氧化反应器。 内、 外室的分隔, 釆用一个与 氧化反应器同轴心的内置圆筒, 圆筒的底部与氧化反应器主体底部的内壁相连。圆筒 外侧与反应器主体内壁之间的空隙为外室, 圆筒内侧为反应器内室。 圆筒的髙度, 比 反应器设计的标准液位低, 保证正常生产过程中, 内、外室液相物料在反应器上部通 联。圆筒外侧可以与反应器主体内壁采用点支撑的方法加以固定。内外室压缩空气或 者其它含氧气体(例如氧气)或者其它含氧气体(例如氧气)的供应量可以是均匀的, 也可以设计成外室的单位液相容积压缩空气或者其它含氧气体(例如氧气)或者其它 含氧气体(例如氧气)供应量大于内室。 内外室液相容积可以相同, 也可以外室大于 内室, 例如外室与内室容积的比为 2: 1, 3: 1, 4: 1等等。
为了适应外室的单位液相容积压缩空气或者其它含氧气体(例如氧气)或者其 它含氧气体(例如氧气)供应量大于内室的单位液相容积压缩空气或者其它含氧气体 (例如氧气)或者其它含氧气体(例如氧气)供应量的要求, 可以在圆筒的腰部设鳃 状栅,收集外室过量的压縮空气或者其它含氧气体(例如氧气)或者其它含氧气体(例 如氧气)并扩散到内室。鳃状栅好比是弯成环形的百叶窗的百叶, 不同的是伸入外室 的叶子宽度和倾斜的角度与伸入内室的不同。伸入外室的最上边的一片叶子与圆筒上 半部分相连(这片叶子没有深入内室的部分, 只是半片叶子), 叶子向下倾斜, 倾斜 的角度为与反应器轴线 (即垂线)成 45度夹角, 叶面近似于伞面的一部分, 叶子的 边缘到达外室空腔靠近内侧三分之一环线的位置。中间的叶片,在外室的宽度与上面 的叶片相同, 只是向下倾斜的角度为 22度。 中间叶片伸入内室部分的宽度与伸入外 室部分的宽度相同, 但是向上倾斜, 倾斜的角度是 10度(与垂线的夹角)。下边的叶 片与圆筒下半部分相连,只有半片叶片伸入内室,宽度和倾斜角度都与中间叶片伸入 内室的部分相同。圆筒上下两部分的连接,可以采用在圆筒内侧设置垂直方向加强筋 的方法实现。鳃状栅中间的叶子也固定在加强筋上,并且以点支撑的形式与圆筒上下 两部分固定。 中间叶片到圆筒上下两部分的高度(距离)相同, 为半片叶片宽度的五 分之一。
在反应器外室底部设一个或者两个环形压缩空气或者其它含氧气体(例如氧气) 或者其它含氧气体(例如氧气)分布器, 向外室供应反应所需要的压缩空气或者其它 含氧气体 (例如氧气) 或者其它含氧气体(例如氧气)。 外室的容积相当于内室的两 倍、三倍或者四倍。当反应器外室单位液相物料容积的平均压缩空气或者其它含氧气 体(例如氧气)或者其它含氧气体(例如氧气)供给量大于反应器内室单位液相物料 容积的平均压缩空气或者其它含氧气体 (例如氧气)或者其它含氧气体(例如氧气) 供给量时, 即相对于内室, 外室的压缩空气或者其它含氧气体(例如氧气)供给量过 量时, 多余的压缩空气或者其它含氧气体(例如氧气)通过内、外室隔板(圆筒)腰 部的鳃状栅扩散到内室,少量外室的液相物料随压缩空气或者其它含氧气体(例如氧 气) (被夹带)进入内室, 而内室的物料却不会通过这个鳃状栅进入外室。 还有少量 过量压縮空气或者其它含氧气体(例如氧气)从外室上部液相扩散进入与外室通联的 内室液相,积极参与氧化反应,使得氧化反应器尾气的氧含量不会因为外室底部压缩 空气或者其它含氧气体 (例如氧气)供给过量而超过 4%的上限限制标准。 尾气氧含 量控制标准为 3〜4%。 作为优化方案, 实行内外室压缩空气或者其它含氧气体(例如氧气)供给量分 别控制、 内外室尾氧含量分别检测, 则可以省略分隔内外室的圆筒上的鳃状栅。
使用环形分布器从反应器外室中部和上部向反应器供水, 添加辅助催化剂, 供 水温度为 180°C。确保反应生成的间苯二甲酸完全溶解在水和醋酸综合溶剂之中。 外 室下部温度可以达到 246〜350°C。 外室下部较好的温度是 288°C。 内室底部温度为 130〜180Ό, 较好的温度是 160°C ; 内室上部温度为 210〜288°C, 较好的温度是 288 °C。 采用环形水分布器向内室上部供水, 水温 30°C, 采用环形分布器向内室中部补 充醋酸, 醋酸温度 30°C。
物流情况是:在内室,使用环形空气分布器从底部吹入压缩空气或者其它含氧气 体 (例如氧气), 进入反应器的新鲜原料含间二甲苯、 醋酸、 催化剂等也从内室底部 进入,经过混合反应, 从上部进入外室。反应生成的水、二氧化碳向上扩散。在外室, 液相物料从上往下移动, 压缩空气或者其它含氧气体(例如氧气)从下往上扩散, 反 应生成的水、 二氧化碳向上扩散。
作为优化方案, 在反应器内室使用树形水分布器替代环形水分布器, 向内室供 水。 辅助溶剂水在树干干流的流向是从下往上。
最终反应生成物间苯二甲酸溶解在水和醋酸构成的混合溶剂中, 从外室底部排 出, 送往结晶系统结晶。
反应器外室设置一组或者两组环形压缩空气或者其它含氧气体(例如氧气) 分 布器。反应器内室设置两组或者更多环形压缩空气或者其它含氧气体(例如氧气)分 布器, 分布器以反应器轴心为中心, 小环形分布器中间可以加设十字形分布器, 十字 与圆环在同一平面。小环形分布器位置更接近反应器底部, 中等环形分布器(在内室 属于较大分布器)设置位置略高于小分布器。大分布器设置在外室。空气分布器压缩 空气或者其它含氧气体(例如氧气)出气孔向下开孔, 开孔方向与垂线成 30度夹角, 沿环线左右两个方向依次间隔交错, 以便空气分布更加均匀。
在外室, 从上到下的流程基本上是平推流流程, 氧化反应基本上按照串联氧化 反应的先后次序进行。通过控制合理的进料速度,在氧化反应器外室的中部以上完成 全部从间二甲苯到对甲基苯甲醛的反应以及从间位甲基苯甲醛到间位甲基苯甲酸的 反应,在反应器外室中部完成从间位甲基苯甲酸到 3-CBA的反应, 中间偏下部完成从 3 - CBA到间苯二甲酸的反应。 外室下部维持短时间的系统平衡——熟化, 以扫除残余 的 3- CBA和间位甲基苯甲酸。所以这个内、外室结构的氧化反应器可以确保正常操作 时液相物料从反应器出料中没有间二甲苯、没有间位甲基苯甲醛、没有间位甲基苯甲 酸、 没有 3- CBA, 只有间苯二甲酸和溶剂醋酸、 辅助溶剂水、 催化剂和助剂, 以及少 量其他杂质。 此时出料口混合溶剂中水的比例 (水 /水 +醋酸)为 50%〜100%, 典型的 比例是 80%。
初始投料的醋酸溶剂不断闪蒸撤出反应器, 补充的水溶剂不断进入反应器, 这 个过程实际上是水置换醋酸的过程, 为系统提高温度创造了条件。
反应器内室撤热有两种方法, 一是采用盘管加热大流量水, 供外室补充水溶剂 用途;二是采用分布器直接向内室中间偏上部位供水,使得间二甲苯氧化反应得以进 行,但是反应温度不要太高,不要超过 250°C。水在溶液中的比例至少在 40%以上(在 溶剂中的比例超过 50%),温度才可以达到 250°C。此时内室底部间二甲苯氧化的主要 区域温度控制 145〜210°C, 以 160°C为好。另外由于内室顶部与外室顶部相通, 内室 顶部也能发生溶剂蒸发撤热。
外室撤热有两个途径, 一是依靠溶剂闪蒸撤热, 闪蒸的溶剂换热后, 凝液回收 分别送往醋酸和水的储罐;二是增加进入外室的供水量,使得液相出料口温度不要超 过设计温度,例如 288Ό。此温度条件下水溶剂可以溶解的间苯二甲酸量差不多是 50% (重量分数)。 增加水的流量就可以增加撤热能力, 增加水溶液带往结晶器的间苯二 甲酸的量, 达到热量和物料平衡。由于水的流量增加, 出料口间苯二甲酸溶液的实际 浓度比该温度下的饱和溶解度低很多。
这种情况使得第一结晶器往往只发生溶剂因为减温减压而闪蒸, 间苯二甲酸浓 度提高,但是不出现结晶或者只出现少量结晶。大量溶剂在结晶器的闪蒸实际是反应 热撤出的途径之一。
内室供水温度为 5〜150°C,典型供水温度为 30°C ;外室供水温度为 20〜250Ό, 典型供水温度为 180°C。
外室水和醋酸作为混合溶剂的间苯二甲酸溶液浓度为 0. 1〜35%, 典型浓度为 30%。 向供水系统储罐添加回收的催化剂, 保证氧化反应器系统内催化剂浓度。 相应 的催化剂浓度(总含量)为 0〜5000ppm,典型浓度为 1050ppm, 典型的比例是钴:锰- 溴为 1 : 1: 1。 催化剂和辅助催化剂均匀地分散在混合溶剂中。
在反应器出口, 混合溶剂中水的比例为 50〜100%, 典型比例为 80°/。。 从而保证 了有机原料相的氧化速度可控、 合理, 醋酸和间二甲苯原料消耗指标降低。
内室温度控制在 130〜210Ό,典型温度为 16CTC ;外室上部温度控制在 246〜350 V , 典型温度是 288°C, 典型反应器压力为 7. 5MPaG。
作为替代方案,反应器出料口区域的温度可以设定在更高的位置,例如: 400~ 500°C。 此时, 混合溶剂中没有醋酸只有水, 氧化反应停留时间更短。
具有内外室结构的氧化反应器本身也可以是一个长径比比较高的塔型反应器, 其长径比是 1. 0〜20, 典型的长径比是 6。
作为优化方案, 这种塔形氧化反应器可以设计成水塔形状, 增加液相顶部气液 界面的面积, 增加液相蒸发面积。
②、 具有内、 中、 外三室结构的氧化反应器。
在具有内外室结构氧化反应器的基础上, 采用两个与氧化反应器同轴心的内置 圆筒, 将氧化反应器分隔成内、 中、外三个室。 小圆筒的底部与氧化反应器主体的底 部内壁相连, 上部浸没在设计液位下面。小圆筒分隔氧化反应器的内室与中室。大圆 筒底部悬空,上部高出设计液位, 内外侧分别固定在小圆筒和反应器主体的侧面内壁 上, 同时在底部以点支撑的方法固定在反应器主体的底部。大圆筒分隔反应器中室与 外室。 内、 中、外三室的气相相通, 液相容积相同(以圆筒面上下延伸所完全分割的 液相容积计算)。 内、 中、 外三个室分别在底部设置压缩空气或者其它含氧气体 (例 如氧气)分布器。外室和中室的环形压缩空气或者其它含氧气体(例如氧气)分布器 的位置略高于大圆筒底部的高度, 避免两室供气不匀。
作为替代方案, 大小圆筒上下的位置可以交换, 即大圆筒悬空, 小圆筒下边与 反应器主体内壁的底部相连。
三个室的液相容积相同, 压缩空气或者其它含氧气体 (例如氧气) 供应流量相 同。
作为优化方案, 内中外三室的液相容积比可以为 1 : 2: 2, 或者 1 : 2: 3。 液相物流情况是: 间二甲苯、醋酸、 催化剂等经过混合从反应器内室底部进入, 内室物料上行, 到达上部从小圆筒上边进入中室。 中室物料下行, 到达底部从大圆筒 下边进入外室。 外室物料上行, 反应完成的物料从外室上部出料。
使用环形分布器从反应器外室下部和中部向反应器缓慢供水; 使用环形分布器 从反应器中室上部和中部向反应器供水,添加辅助催化剂氢溴酸;使用分布器从反应 器内室中部和上部向反应器供水和醋酸, 水和醋酸的比例为 20: 80到 100: 0, 典型 比例是 50: 50。 一方面平衡反应温度, 一方面稀释有机原料溶液, 为提升温度做准 备。 内室补充溶剂温度为 20〜150Ό, 典型供水温度 3(TC ; 中室供水温度为 20〜200 。C, 典型供水温度为 120°C ; 外室供水温度为 20〜250°C, 典型供水温度为 180°C。 内室温度控制在 145〜210°C, 典型温度为 16(TC ; 中室温度控制在 180〜288°C, 典 型温度为 250Ό ; 外室上部温度控制在 246〜350°C, 典型温度是 288°C, 反应器压力 为 7. 5MPaG。
作为优化方案, 内室环形混合溶剂分布器可以釆用树形水分布器替代, 树干干 流方向为从下往上, 即从上游取热预热, 提高供下游的混合溶剂的温度。
ώ于中室和外室底部都是高温区域, 所以即使中室上部有快速氧化生成的间苯 二甲酸结晶出现, 也会在随液相物料下行的过程中被溶解。
在氧化反应器出口, 以水和醋酸作为混合溶剂的间苯二甲酸溶液浓度为 0. 1〜 35%, 典型浓度为 20%; 相应的催化剂浓度 (总含量) 为 0〜3000ppra, 典型浓度为 1050ppm, 典型的钴: 锰: 溴比例为 1 : 1: 1。 混合溶剂中水的比例为 60〜100%, 典 型比例为 80°/。。供水系统储罐添加回收的催化剂,保证氧化反应器系统内催化剂浓度。
作为替代方案, 大、 小圆筒上下位置和固定的形式相互交换之后, 物流作相应 的变更, 空气分布器的设置形式, 以及水分布器的设置位置也作相应变更。原料从内 室上部进料, 经过混合反应从下部进入中室, 中室物料上行, 从上部进入外室, 外室 物料下行, 从侧面底部出料。压缩空气或者其它含氧气体(例如氧气)仍然从各室下 部进入。 各室温度控制依照物流次序作相应变更。
氧化反应器本身也可以是一个长径比比较高的塔型反应器, 其长径比是 1. 5〜 20, 典型的长径比是 6。
作为优化方案, 这种塔形氧化反应器可以设计成水塔形状, 增加液相顶部气液 界面的面积, 增加液相蒸发面积。
作为优化方案, 在外室再设置一个浸没在液相的内置圆筒, 将外室一分为二, 圆筒与反应器主体底部相连。从中室进入外室的物料上行后再次下行,从反应器侧面 底部出料。这个优化方案实际是将三室氧化反应器转变成了四室氧化反应器, 四个室 都设空气分布器。
③、 卧式平推流氧化反应器。
反应器一端进料另一端出料, 反应器底部设数排直管状压缩空气或者其它含氧 气体(例如氧气)分布器和数排供水分布器。这个反应器近似于平推流反应器。作为 优化的方案,可以在反应器内设螺旋薄片推进轴,缓慢沿液相物料流动方向推进物料, 螺旋薄片推进轴与反应器内壁不需要接触,对物料的推进只是象征性的,主要目的是 对反应器内部进行动态分室, 降低液相物料的无序流动性,保证液相物料的氧化反应 沿物流方向基本按照从间二甲苯到间苯二甲酸串联氧化反应的次序进行。
反应器上部气相相通, 部分醋酸溶剂和水蒸发, 二氧化碳、 氮气等挥发, 然后 一起进入气相冷凝换热系统回收热量, 从反应器撤热。 气相出口设置在出料端上部, 冷凝液分别送往回收醋酸和水的储罐。
大量反应热通过结晶器溶剂闪蒸撤出, 经过热交换回收热量。
使用分布器向反应器物料流的上游添加醋酸和水, 向中游和下游添加水, 确保 反应生成的间苯二甲酸和 3-CBA完全溶解在水和醋酸构成的混合溶剂之中。反应器入 口端,即间二甲苯氧化为间位甲基苯甲酸的主要区域温度控制通过添加低温醋酸和水 的混合溶剂来实现,这个区域的温度为 145〜210°C, 以 16CTC为好。随着水含量的增 加, 温度可以逐步增加, 但是要控制反应不能太剧烈, 水含量未达到 50%时, 温度不 超过 250°C。 中段温度控制在 180〜288°C, 典型温度是 250'C。 反应器末端温度控制 在 245〜350°C, 典型温度是 288°C。 反应器压力为 7. 5MPaG。
反应器内部物料出料口区域间苯二甲酸溶液中没有 3-CBA, 没有间位甲基苯甲 酸。
作为替代方案, 适当增加反应器长度, 可以取消螺旋簿片推进轴, 简化反应器 结构。
④、 塔式活塞流氧化反应器
塔式活塞流氧化反应器为一长径比比较高的塔式反应器,长径比例为 6〜30,典 型的长径比例为 20。 反应器内部分段设置环形压缩空气或者其它含氧气体(例如氧 气)分布器和环形进水分布器。氮气和反应生成的二氧化碳、有机废气等从反应器上 部挥发, 经过换热器冷却后处理或者除去。少量醋酸溶剂和水挥发进入冷凝系统。反 应热通过大量溶剂在结晶器闪蒸撤出,经过换热回收热量,或者在进入结晶器之前首 先经过换热器换热, 回收热量。随着溶剂水的不断加入, 相应区域的反应温度也可以 不断提高,抵御因为反应物浓度降低带来的反应速度下降的趋势。出料口温度可以达 到 246〜350°C, 典型温度是 288°C。 由原料间二甲苯、溶剂醋酸、催化剂、辅助催化 剂构成的混合物料进入反应器的初始温度是 130〜210°C,典型温度是 160°C。反应器 压力为 7. 5MPaG。
通过控制进水的量, 保持反应物温度稳定, 稀释反应物有机原料, 达到反应温 度、反应热量与反应速度和水流量的平衡。沿液相物流方向, 反应物有机原料浓度逐 步降低, 反应温度逐步提高, 以强化反应条件, 维持反应速度受控、 稳定。
作为优化方案, 采用树形水分布器向塔内供水, 树干干流水流方向为从上向下 流动, 即从反应物液相上游取热, 稀释下游溶液。
作为补充的撤热措施, 方案之一: 在反应器外壁缠管, 使用冷却介质换热是一 项有效的撤热措施。
作为补充的撤热措施, 方案之二, 在反应器内部设换热盘管, 盘管内冷却介质 流向顺着反应物料流向从上游向下游流动。这里有两个注意事项:一是盘管浸没在间 苯二甲酸溶液区域的表面温度不能低于该区域液相浓度作为饱和溶解度所对应的温 度,避免在盘管外表面形成间苯二甲酸结晶;二是盘管不进入间苯二甲酸髙浓度区域, 该区域仍然依靠添加低温水平衡温度。
添加低温水, 可能会在液相形成局部结品, 所以本发明在塔底部预留足够的熟 化区域, 让小的结晶颗粒重新被溶解。
树形水分布器在间苯二甲酸溶液高浓度区域的温度也不能低于该浓度作为饱和 溶解度对应的温度 (结晶析出温度)。
添加的水溶剂为结晶器闪蒸换热之后回收的水, 含有循环使用的催化剂和辅助 催化剂, 典型催化剂浓度为 900ppm, 典型的钴: 锰: 溴的比例为 1 : 1: 1。
原料、 溶剂、 催化剂 (包括回收溶剂和回收催化剂)经过混合后进入反应器上 部,使用环形空气分布器分别从底部和四分之一高度的中部吹入压缩空气或者其它含 氧气体 (例如氧气)。 反应器内部, 物料从上往下运行, 通过液位控制从反应器下部 出料。物料流在反应器内部近似为从上到下的活塞流。压缩空气或者其它含氧气体 (例 如氧气)和反应生成的二氧化碳上行会夹带少量液相物料上行,增加少量间苯二甲酸 在反应器内部的停留时间, 但是不会影响大局。
反应控制同样是通过控制间二甲苯、 醋酸进料量排出量、 压缩空气或者其它含 氧气体(例如氧气)进气速度以及水的进料量, 达到控制反应器内温度平衡、反应物 有机原料相在反应器中下部反应完成。兼顾到热量平衡,通过补充进水, 达到顺利撤 热的目的。
典型的温度控制是: 液相顶部温度控制在 160Ό,中间温度控制在 250°C, 底部 温度控制在 288°C。从低温端到高温端,液相水含量逐步增加, 形成梯度。从上到下, 温度逐渐升高形成梯度, 液相水含量逐渐增加形成梯度。
⑤、 多反应器串联式氧化反应器组合。
采用两个以上的氧化反应器尤其以三个以上的反应器串联效果最好。 除第一个 氧化反应器之外, 其它反应器均采用无搅拌反应。 控制第一氧化反应器的氧化条件, 使得温度更加缓和。 例如, 反应器温度为 130〜210°C, 甚至 130〜150°C, 典型温度 为 160Ό ; 只添加醋酸钴、 醋酸锰催化剂, 不添加氢溴酸辅助催化剂。 这个条件下, 从间位甲基苯甲酸向 3- CBA的反应比较困难。这个反应器的撤热方法,与现在的间苯 二甲酸和对苯二甲酸氧化反应器撤热方法相似, 采用溶剂闪蒸的撤热办法。
从第二个反应器开始, 液相物料均采用从上到下的单一物流方式, 使得液相物 料流动相对稳定, 物料的组成中逐渐没有间二甲苯、 间位甲基苯甲醛, 氧化反应相应 地按照串联氧化反应的次序进行。 工艺条件的关键是: 第二个氧化反应器的温度为 246〜350°C,典型温度为 288 Ό。在这个温度条件下,间苯二甲酸的饱和溶解度为 50% 左右, 控制浓度 20〜35%, 典型控制浓度为 30%。 出料口设置在反应器下方进料口对 角的位置。 反应器撤热采用溶剂闪蒸撤热的方法。
氧化反应的物料从第一氧化反应器到第二氧化反应器采用高压泵输送的办法实 现。 辅助催化剂氢溴酸添加在第二氧化反应器。
使用环形或者树形水分布器向第二和第三氧化反应器供水, 逐步置换溶剂闪蒸 过程中脱除的醋酸, 降低醋酸在溶剂中的比例, 同时确保反应生成的间苯二甲酸完全 溶解在水和醋酸构成的综合溶剂之中。 最终氧化反应器温度控制在 246〜350°C, 典 型温度为 288°C。 最终氧化反应器出口物料中没有该串联氧化反应的中间产物, 只有 间苯二甲酸以及溶剂、 催化剂、助剂等。第三氧化反应器(以及最终氧化反应器)采 用溶剂闪蒸撤热方法。
这种多反应器串联式氧化反应器组合也可以结合采用 "具有内、 外室结构的氧 化反应器", 以及 "具有内、 中、 外三室结构的氧化反应器"。那样, 有两只反应器进 行组合就可以了。例如,采用一台常规氧化反应器和一台具有内外室结构的氧化反应 器组合: 常规氧化反应器进行低温氧化, 反应温度在 130〜210°C, 乃至 130〜: 150°C, 典型温度为 160Ό ; 只添加醋酸钴、 醋酸锰催化剂, 不添加氢溴酸辅助催化剂。 采用 溶剂闪蒸的撤热方法。 反应停留时间 20〜150分钟, 典型停留时间 60分钟。 反应混 合浆料中主要产物是间位甲基苯甲酸。反应后的物料送入具有内外室结构的氧化反应 器内室, 底部进料。 内室物料上行, 外室物料下行。 物料在内室经过溶剂闪蒸和补充 水, 逐歩置换醋酸溶剂。 该反应器温度控制为 246〜350°C, 典型温度为 288°C。
多反应器串联式氧化反应器组合, 可以有很多种组合方式。
2、 原料组成:
氧化反应以间二甲苯为主要原料, 以压缩空气或者其它含氧气体 (例如氧气) 中的氧气为辅助原料, 以醋酸为初始溶剂, 以醋酸钴、醋酸锰为催化剂, 以氢溴酸为 辅助催化剂。 氧化反应后期以水作为辅助溶剂。
3、 添加水作为辅助溶剂。
在氧化反应器内部, 从大量产生间位甲基苯甲酸以及间位甲基苯甲酸高浓度的 前后位置添加水作为补充溶剂,在 3-CBA到间苯二甲酸氧化反应区域液相物料中要添 加足够的水作为间苯二甲酸的辅助溶剂,适当提高反应温度,增加间苯二甲酸在水和 醋酸混合溶剂中的溶解度参数, 使得反应生成的间苯二甲酸完全溶解在溶剂中。
提高反应温度抵御了由于液相物料中增加水的含量, 反应物有机原料相在溶液 中浓度降低引起的氧化反应速度降低的趋势,甚至适当提高氧化反应的速度。从间位 甲基苯甲酸到 3- CBA反应区域的温度也可以适当提高, 例如 288Ό, 提高串联氧化反 应的反应速度。
作为溶剂的水可以逐步添加到间位甲基苯甲酸到 3-CBA氧化反应区域, 也可以 添加到生成间位甲基苯甲酸之前的反应区域。从间二甲苯到间苯二甲酸反应流程的各 个阶段, 水的含量逐渐增加, 形成溶剂中水含量为 0〜100%的梯度。 实际操作中, 控 制溶剂中水含量为 5〜95%的梯度, 是可行的。典型的间苯二甲酸溶液浓度是 30%, 混 合溶剂中典型的水的比例是 80%。 典型温度为 288Ό , 反应器压力为 7. 5MPaG。
添加到氧化反应器内部液相物料中的溶剂氷, 可以采用列管换热的方式加热, 列管内部通水,列管出口是向反应器液相添加水作为辅助溶剂的位置,列管的进水端 端面封闭, 从横向向列管供水。列管埋在反应物液相物流的上游,外侧为反应物液相 物料, 从上游物料反应热中取热, 稀释下游的液相物料。
4、 氧化反应温度、 压力。
本发明氧化反应压力为 0. 5~8. OMPaG左右,反应温度分段分别为 130〜210°C左 右和 180~250°C左右, 以及 210〜350°C左右, 分段控制。 典型的低温段温度和压力 分别是 16CTC和 0. 5MPaG;典型的中温段温度和压力分别是 25(TC和 5. OMPaG;典型的 高温段温度和压力分别是 288°C和 7. 5MPaG。 温度通过控制闪蒸进入反应器顶部冷凝 器的溶剂和水的量、凝液回流量、结晶器醋酸溶剂和水溶剂闪蒸撤热量、补充进入反 应器的水和醋酸的温度与量、压縮空气或者其它含氧气体(例如氧气)的进气量、氮 气和二氧化碳的排出量, 以及反应热等进出反应器的热量综合平衡来实现。
反应器压力通过控制压縮空气或者其它含氧气体 (例如氧气) 进气量和反应器 尾气冷凝系统不凝气出口调节阀的开度加以控制。温度是第一控制要素,压力参数配 合温度要求而设定。 压力上限是安全控制第一要素。
5、 压缩空气或者其它含氧气体(例如氧气) - 例如, 当间二甲苯的添加流量为 12吨 /小时, 压缩空气或者其它含氧气体(例 如氧气) 的添加量为 41. 57吨 /小时。
空气压缩机的进气压力因为反应器压力增加相应需要提高, 为满足 7. 5MPaG的 反应压力, 采用出气口压头为 9. 3MPaG的空气压缩机。
6、 典型氧化反应实施例:
( 1 )、 以两台氧化反应器组合为例: 其中第一氧化反应器采用具有近似活塞流 反应流程的塔式氧化反应器, 以压缩空气为辅助原料;第二氧化反应器釆用具有近似 活塞流反应流程的塔式氧化反应器, 以氧气为辅助原料。 '
采用一台直径 4000瞧、 高度 28000mm的塔式氧化反应器作为第一氧化反应器。 以间二甲苯为原料, 以醋酸为初始溶剂, 以醋酸钴、醋酸锰为催化剂, 催化剂有效成 分钴、 锰离子含量 (离子质量加和) 为 700ppm, 钴、 锰的比例为 1 : 1。 初始原料投 料比例 (质量)为间二甲苯: 30%, 醋酸: 64%, 7K: 6%。 配制好的原料和催化剂从氧 化反应器上端进料, 液相物料下行。 间二甲苯进料流量 128吨 /小时。
液相物料从反应器上部进入反应器,反应生成物从底部出料。压缩空气分六路从 反应器底部侧面进入反应器。反应热从反应器顶部采用溶剂闪蒸的方法撤出,采用换 热器回收热量, 换热器可以是一座冷凝塔, 凝液除去少量醋酸之后, 部分水返回氧化 反应器。 反应器内部水含量为 6-20%, 典型水含量为 10%。 控制反应器尾气含氧量小 于 1-3%, 确保氧化反应器安全, 也提髙压缩空气利用率。
压缩空气的进口压力为 0. 5MPaG。 反应器内部压力为 0. 1- 0. 3MPaG。 反应温度 110-160°C, 典型温 '度为 145°C。 由于间位甲基苯甲酸进一歩被氧化的难度相对较大, 而且系统内部没有氢溴酸辅助催化剂,所以在这个条件下间二甲苯主要被氧化生成间 位甲基苯甲酸,少量间位甲基苯甲酸会进一歩氧化成家苯二甲酸,形成结晶沉淀下來。
反应器底部出料口附近区域基本上没有间二甲苯。底部出料,物料经过蒸发提浓, 脱除醋酸和水以及少量的间二甲苯, 得到含间苯二甲酸为 68%、 含间二甲苯为 17%、 含醋酸为 11%、 含水为 4%的混合物。 按照 1 : 2. 5的比例, 将混合物与脱离子水配成 浆料打浆, 在浆料中按照间二甲苯含量 350ppm (离子质量浓度) 的比例添加氢溴酸 作为辅助催化剂, 第一氧化阶段添加的钴、锰催化剂仍然存在并且有效。采用高速泵 将浆料送入第二氧化反应器液相上端。
第二氧化反应器采用一台直径 4500匪, 高 36000醒的塔式氧化反应器(也可以 采用具有内外室结构的氧化反应器,或者具有内中外三室结构的氧化反应器,或者卧 式平推流氧化反应器)。采用氧气作为辅助原料(也可以采用压缩空气作为辅助原料)。
第二氧化反应器液相温度为 285- 300Ό , 典型温度为 288°C。 温度为第一控制要 素,压力为第二控制要素。采用溶剂闪蒸,蒸气从反应器顶部离开反应器的方法撤热, 水和醋酸混合的溶剂在氧化反应器顶端的冷凝塔经过分凝,水和醋酸分别进入水和醋 酸的储罐。分凝塔通过换热加热低压蒸气回收热量。部分冷凝水和醋酸返回氧化反应 器, 维持反应器内部溶剂相醋酸与水的比例为 1 : 4到 1: 99, 典型比例为 3: 17c 为了避免使用大流量高压空气压缩机,本装置使用空分装置提供的液体氧气作为 氧化剂原料。液氧经过高压泵(或者高速泵)送入蒸发器, 在蒸发器回收利用冷量资 源, 气化的氧气从氧化反应器底部通入。氧气管线从反应器上部进入, 利用反应物料 预热管道内部氧气。采用环形氧气分布器, 氧气分布器为三个环形, 三个环的直径分 别为 2000匪、 3200醒 和 4000醒。 直径 2000mm的圆环中间加十字分布器。 由于氧气 气体总量相对采用压縮空气为较少,可以使得反应器液相受到气体上行影响的扰动较 小,液相物料流程从上往下相对比较稳定, 相当于活塞流,上层的原料和中间氧化产 物不会快速沉降到底部。 又由于通入氧气的部位, 液相物料中水的含量达到 61%, 有 机相总和约为 39%, 所以不会出现发生剧烈氧化反应的情况。控制反应器尾气含氧量 小于 1-2%, 确保氧化反应器安全, 也提高氧气利用率。
作为优化方案,可以分两层或者三层设置环形氧气分布器,减少反应器底部液相 物料因为通入气体而产生的扰动, 使得下部物料下降更接近活塞流。
反应器中下部液相物料因为反应放热, 引起局部升温(趋势), 水和醋酸被气化、 上升, 水和醋酸蒸气到达反应器顶部气相,再进入分凝塔撤出热量。这个蒸气上升的 过程也会对液相物料下行的活塞流造成扰动,但是不会造成顶部含间位甲基苯甲酸的 物料快速沉降到底部。从氧化反应器液相顶端添加的浆料中的间苯二甲酸结晶体将在 沉降过程中很快被溶解, 其中包含的 3-CBA也很快被氧化为间苯二甲酸。
氧气的进口压力为 8. 0MPaG。 反应器内部压力为 7. 3-7. 5MPaG。
第二氧化反应器尾气的主要成分是少量氧气和二氧化碳、一氧化碳, 以及微量醋 酸和其它有机成分。 压力为 7. 5MPaG。
从第二氧化反应器底部出料口出来的是间苯二甲酸溶液, 其中间苯二甲酸占 27%, 醋酸占 11%, 水约占 72%。 间苯二甲酸溶液送往第一结晶器, 在 255°C闪蒸和结 晶, 大约 19. 5个百分点的间苯二甲酸析出形成晶体。 结晶器顶部设精馏塔换热回收 蒸气余热, 同时将醋酸和水初步分离。 醋酸稍加精制用于调配间二甲苯原料做溶剂, 水作为添加到第二氧化反应器的脱离子水,加入反应器, 用于补充辅助溶剂水, 降低 醋酸浓度, 减少醋酸消耗。
第一结晶器结晶剩佘的溶液送往第二结晶器, 在 200Ό条件下闪蒸和结晶, 大约 7个百分点的间苯二甲酸结晶析出。 结晶器顶部设精馏塔换热回收蒸气余热, 同时将 醋酸和水初步分离。 粗醋酸和水分别送入各自的储罐。
第二结晶器结晶剩佘的溶液送往第三结晶器, 在 150°C条件下闪蒸和结晶, 大约 0. 8个百分点的间苯二甲酸结晶析出。 结晶器顶部设精馏塔换热回收蒸气余热, 同时 将醋酸和水初步分离。 粗醋酸和水分别送入各自的储罐。
第三结晶器剩余溶液经过过滤除去固体杂质,一部分送往母液回收处理系统, 回 收催化剂, 除去溶解性杂质, 其余母液用于间位甲基苯甲酸打浆。
结晶系统得到的间苯二甲酸晶体经过醋酸洗涤(除去钴、锰、溴催化剂和辅助催 化剂, 这个工序也可以省略)、 分离、 干燥、 水洗、 分离、 干燥, 得到精间苯二甲酸 产品, 其 3-CBA含量小于 10ppm, 间位甲基苯甲酸含量小于 5ppm
精间苯二甲酸小时产量为 200吨。单位产品消耗间二甲苯为 652公斤 /吨, 燃动 能耗 99公斤标油 /吨。 醋酸消耗 9公斤 /吨。
(2)、 以一台塔式氧化反应器、 采用氧气作为辅助原料为例- 釆用一台直径 4500mm, 高 38000蘭的塔式氧化反应器, 以间二甲苯为原料, 以 醋酸为初始溶剂, 以醋酸钴、醋酸锰为催化剂, 以氢溴酸为辅助催化剂, 催化剂和辅 助催化剂有效成分钴、 锰、 溴的离子含量(离子质量加和) 为 900ppm, 钴、 锰、 溴 的比例为 1 : 1: 1。 初始原料投料比例 (质量) 为间二甲苯: 28%, 醋酸: 64%, 水: 8%。 配制好的原料和催化剂从氧化反应器上端进料, 液相物料下行。
为了避免使用大流量高压空气压缩机, 本装置使用空分装置提供的液体氧气作 为氧化剂原料。液氧经过高压泵(或者高速泵)送入蒸发器, 在蒸发器回收利用冷量 资源后, 气化的氧气从底部通入氧化反应器(氧气管高从反应器上部进入反应器,经 过液相物料加热), 采用环形氧气分布器, 氧气分布器为三个环形, 三个环的直径分 别为 2000mm、 3200mm和 4000誦。 直径 2000mm的圆环中间加十字分布器。 由于氧气 气体总量相对于压缩空气较少,可以使得底部液相受到气体上行影响的扰动较小,尽 量使得液相物料流程从上往下相对比较稳定,相当于活塞流,上层的原料和中间氧化 产物不会快速沉降到底部。 又由于通入氧气的部位, 液相物料中水的含量达到 59%, 有机相总和约为 41%, 所以不会出现发生剧烈氧化反应的情况。 随着含氧气体上行, 液相含水率下降,但是含氧气体中氧气的浓度也逐歩降低。控制反应器尾气含氧量小 于 1-2%, 确保氧化反应器安全, 也提高氧气利用率。
作为优化方案, 可以分两层或者三层设置环形氧气分布器, 减少反应器底部液 相物料因为通入气体而产生的扰动, 使得下部物料下降更接近活塞流。
氧气的进口压力为 8. lMPaG。 反应器内部压力为 7. 5MPaG。使得反应器底部高温 区的温度仍然低于沸点, 不会产生沸腾现象。
氧化反应器液相温度分为四段控制-
1 )、液相物料从上往下 5分之 1处以上,温度控制在 130-180°C, 以 160Ό为好, 此时间二甲苯氧化为间位甲基苯甲醛和间位甲基苯甲醛氧化为间位甲基苯甲酸的速 度比较快, 温度相对温和可以减少醋酸的消耗 (被氧化成二氧化碳或者一氧化碳)。 这个区域的氧化反应热主要用于原料间二甲苯和溶剂醋酸以及水升温。间二甲苯和醋 酸、水、催化剂的混合原料从液相物料的顶部进入液相, 这种新鲜的原料具有很强的 氧气结合能力,用于抢夺含氧气体中剩余的少量氧气。作为替代方案是将这种新鲜的 混合原料通入液相物料液面以下 500mm处。
2 )、 液相物料从上往下 5分之 1到 5分之 2处, 温度控制在 160- 246 °C, 以 200 V为好。 这个区间采用添加少量 20-45Ό脱离子冷水的办法控制温度进一歩升高(作 为替代方案, 可以添加 45°C 以上 150°C以下的脱离子水作为冷却剂) 。计算间二甲 苯和醋酸进料量, 以及脱离子冷水的进水量, 控制液相物料总含水率在 20-30%区间。
由于控制 (减少)氧气的进气量, 可以控制液相物料氧化反应的完成进度位置 下移, 所以以上两个区域的温度不会失去控制而无节制上升。
由于这两个区域氧化反应的条件苛刻度低, 少量氧气也会被有机物料所抢夺, 产生氧化反应, 所以反应器顶部氧化尾气的含氧率小于 1%。
3 )、液相物料从上往下 5分之 2到 5分之 4处, 温度控制在 210- 300Ό , 以 288 °C为好。这个区域通过添加 100- 20CTC高温脱离子水来稳定液相温度, 遏制因为氧化 反应放热使得液相物料温度升高的趋势。 高温脱离子水从反应器侧壁喷入液相物料, 或者釆用环形水分布器将水喷入液相物料。脱离子水喷嘴或者环形水分布器采取一用 一备两组交替使用的方法(或者一用两备的方法), 使得沉降和结晶在喷嘴附近或者 结晶在环形水分布器上的间苯二甲酸晶体溶解。
这个区域主要完成从间位甲基苯甲酸到间苯二甲酸的氧化反应。
4)、液相物料从上往下 5分之 4处到底部, 温度控制在 285- 30(TC, 以 288°C为 好。 实际控制在 288- 289°C区间。 这个区域从上到下设置 4个温度捡测点, 第二检测 点温度允许比第一检测点温度高 0. 1 °C, 第三检测点温度要求与第二检测点温度相 同。当这个区域温度有上升趋势时,通过增加氧气供给量, 或者降低间二甲苯原料进 料速度,使得氧化反应完成进度上移,确保这个区域反应物有机原料相全部被氧化成 间苯二甲酸, 没有 3- CBA和间位甲基苯甲酸。
氧化尾气的主要成分是少量氧气和二氧化碳、 一氧化碳, 以及微量醋酸和其它 有机成分。 压力为 7. 5MPaG。
这个工艺与现在的间二甲苯氧化工艺不同,没有反应器顶部大量溶剂闪蒸撤热, 反应器液相从上到下温度由低到高形成梯度, 大部分反应热通过加热脱离子水被吸 收, 通过脱离子水在结晶器闪蒸放热而撤出。 闪蒸得到的蒸气通过换热器回收热量。 由于没有大量氮气, 这个方法液相物流流动相对稳定, 更加接近于活塞流。
重要说明: 作为优化和替代方案, 替代所有环形水分布器和反应器侧壁水喷嘴 向反应器内部添加冷却水的方法,可以在反应器内部设置从上往下的列管换热器,列 管内部通入脱离子冷却水, 水温 36°C, 水的流向为从上往下, 列管内部水的出口分 散在反应器液相不同的高度,反应热放热量大的位置出水量大,维持各区反应温度稳 定。这个方案的好处是: ①、依次从液相物料的上部到下部取热, 维持液相物料从上 到下温度逐歩升高的梯度; ②、降低列管出水口与出水口位置液相物料的温度差, 避 免间苯二甲酸结晶沉积在换热器管壁。 列管进脱离子水量为 133吨 /小时。 其中第一 温度控制区不出水,完全依赖列管换热器取热;第二温度控制区从上到下均匀分散出 水 48吨 /小时, 依靠换热器取热和低温水中和稀释液相物料, 吸收反应热;第三温度 控制区均匀分散出水 85吨 /小时, 依靠换热器取热, 并且最终依靠相对低温的水(实 际温度为 200- 280°C )稀释液相物料, 吸收反应热, 维持液相温度在 288°C 。 出水位 置和出水量依靠列管在不同位置的开口数量, 通过 2-3个阀门确定。
从氧化反应器底部出料口出来的是间苯二甲酸溶液, 其中间苯二甲酸占 17. 5%, 醋酸占 23. 5%, 水占 58. 2%。 间苯二甲酸溶液送往第一结晶器, 在 255°C闪蒸和结晶, 大约 10个百分点的间苯二甲酸析出形成晶体。 结晶器顶部设精馏塔换热回收蒸气余 热, 同时将醋酸和水初步分离。醋酸稍加精制用于调配间二甲苯原料做溶剂。氷作为 第三段温度控制区的脱离子冷却水, 加入反应器, 用于控制温度, 或者送入水储罐。
第一结晶器结晶剩余的溶液送往第二结晶器,在 20CTC条件下闪蒸和结晶,大约 7个百分点的间苯二甲酸结晶析出。结晶器顶部设精馏塔换热回收蒸气余热, 同时将 醋酸和水初步分离。醋酸稍加精制用于调配间二甲苯原料做溶剂。水作为第三段温度 控制区的脱离子冷却水, 加入反应器, 用于控制温度, 或者送入水储罐。
第二结晶器结晶剩余的溶液送往第三结晶器,在 15 TC条件下闪蒸和结晶,大约 0. 8个百分点的间苯二甲酸结晶析出。 结晶器顶部设精馏塔换热回收蒸气余热, 同时 将醋酸和水初步分离。醋酸稍加精制用于调配间二甲苯原料做溶剂。水作为第三段温 度控制区的脱离子冷却水, 加入反应器, 用于控制温度, 或者送入水储罐。
第三结晶器剩余溶液经过过滤除去固体杂质, 一部分送往母液回收处理系统, 回收催化剂, 除去溶解性杂质,其余母液用于氧化反应器内部液相物料的冷却介质一 一脱离子冷水。
结晶系统得到的间苯二甲酸晶体经过醋酸洗涤 (除去钴、 锰、 溴催化剂和辅助 催化剂, 这个工序也可以省略)、 分离、 干燥、 水洗、 分离、 干燥, 得到精间苯二甲 酸产品, 其 3-CBA含量和间位甲基苯甲酸含量均小于 15pPm。
精间苯二甲酸小时产量为 120吨;单位精间苯二甲酸产品消耗间二甲苯为 651. 5 公斤 /吨, 燃动能耗 108公斤标油 /吨; 醋酸消耗 18公斤 /吨。
7、 典型的结晶系统实施例:
氧化反应器出料通过液位控制进入第一结晶器。
结晶系统设 7个串联结晶器, 结晶器设置搅拌器。 结晶温度依次降低, 每个结 晶器温度差为 21 °C, 即第一结晶器温度为 267°C, 第二结晶器温度为 246 °C, 依次类 推, 第七结晶器温度为 120Ό。 晶粒尺寸分布均匀, 平均粒度为 120微米, 大小符合 聚酯工业要求。
闪蒸的溶剂经过换热器回收热量, 溶剂醋酸和溶剂水回收使用。 最后一级结晶 器分离结晶体之后的母液经去除漂浮的固体杂质, 送溶剂回收和催化剂回收系统。
作为优化方案, 结晶系统可以只设 4个或者 5个结晶器, 增加各个结晶器之间 的温度差。 也可以适当提高最末一个结晶器的温度, 例如提高到 160°C。

Claims

权 利 要 求 书
1、 本发明一种精间苯二甲酸的制造方法, 其技术特征是:
控制氧化反应条件, 配合结晶系统, 使得氧化反应的目标产物间苯二甲酸在结 晶成固体的时刻, 该结晶区域反应体系物料中的间二甲苯、间位甲基苯甲醛、间位甲 基苯甲酸、 3-羧基苯甲醛 (3-CBA) 都已经被氧化成间苯二甲酸, 所以结晶得到的中 间产品粗间苯二甲酸中没有 3-羧基苯甲醛(3 - CBA) 和间位甲基苯甲酸两项杂质; 采用具有能够分隔原料间二甲苯和氧化反应目标产物间苯二甲酸的氧化反应器 结构,如:具有内、外室结构的氧化反应器、具有内、 中、外三室结构的氧化反应器、 卧式平推流氧化反应器、塔式活塞流氧化反应器, 以及多反应器串联的氧化反应器组 合, 使得从原料间二甲苯到产物间苯二甲酸, 反应物料形成上下游关系;
以间二甲苯为原料, 以醋酸为初始溶剂, 水为辅助溶剂, 采用醋酸钴、 醋酸锰 为催'化剂, 氢溴酸为辅助催化剂, 将原料、溶剂和辅助溶剂、催化剂和辅助催化剂混 合后添加到氧化反应器或者氧化反应器组合,吹入压缩空气或者其它含氧气体(例如 氧气)或者含氧气体,在 130〜350'C温度下反应 15〜150min,得到间苯二甲酸溶液; 间苯二甲酸溶液经过换热器冷却、 闪蒸罐浓缩、 多级结晶、 分离、 过滤、 水洗、 分离、 过滤、 干燥工序, 得到精间苯二甲酸产品;
催化剂钴、锰、 溴三种离子的总质量浓度为 300〜3000ppm, 钴锰原子比为 30〜 0. 3, 钴锰离子总浓度与溴离子的原子比例为 0. 5〜2. 5。
2、根据权利要求 1所述的精间苯二甲酸的制造方法, 其特征在于采用下列氧化 反应器或者氧化反应器组合:
( 1 )、 具有内、 外室结构的氧化反应器, 采用内置的与反应器同轴心的圆筒将 反应器分隔成内外室, 内外室液相在圆筒顶部通联,外室底部物料出口与内室底部原 料进口有效分隔, 内外室单位液相容积的压缩空气或者其它含氧气体 (例如氧气)供 给量相同; 采用环形空气分布器; 釆用环形水分布器;
或者, 外室的单位液相容积压缩空气或者其它含氧气体(例如氧气)供给量大 于内室, 过量的压缩空气或者其它含氧气体(例如氧气) 经过鳃状栅进入内室; 或者, 内室采用树形水分布器;
(2)、 具有内、 中、 外三室结构的氧化反应器, 釆用两个内置的与反应器同轴 心的圆筒将反应器分隔成内中外三个室, 中室和外室液相在大圆筒下边通联,外室上 部液相与中室上部液相有效分隔; 中室上部与内室上部在小圆筒上边通联, 中室下部 与内室下部原料进口区有效分隔;外室上部反应器液相物料出口与内室下部原料进口 区有效分隔; 采用环形空气分布器; 采用环形水分布器; 或者, 内室采用树形水分布器;
作为替换方案, 大、 小圆筒上下位置交换, 改变内中外三室物流的流程, 即中 室和外室在大圆筒上边通联,中室和内室小圆筒下边通联,进入反应器的原料、溶剂、 催化剂等从内室上部进料;
( 3 )、 具有平推流反应流程的卧式氧化反应器, 反应终端液相与原料进口液相 物料无法任意混合,从反应器原料进口到反应物料出口,氧化反应基本按照串联氧化 反应的次序进行;
作为优化方案, 釆用螺旋薄片推进轴对反应物液相进行动态分室;
(4)、 具有近似于活塞流反应流程的塔式氧化反应器为一长径比例为 6〜30的 塔式反应器, 内部分段设置压缩空气或者其它含氧气体(例如氧气)分布器和环形进 水分布器;
或者, 采用树形水分布器;
作为补充的反应热撤热方案之一, 在反应器外壁缠管, 使用冷却介质换热是一 项有效的撤热措施;
作为补充的反应热撤热方案之二, 在反应器内部设换热盘管, 盘管内冷却介质 流向顺着反应物料流向, 从上游向下游流动;
( 5 )、 采用两个或者三个以上反应器串联的氧化反应器组合, 使得氧化反应物 料形成上下游关系, 处于近似的平推流状态;
采用三个及三个以上常规氧化反应器串联组合;
采用一个常规氧化反应器与一个"具有内、 外室结构的氧化反应器", 或者与一 个 "具有内、 中、 外室结构的氧化反应器" 组合, 或者一个 "塔式活塞流氧化反应 器"组合;
釆用两个 "具有内、 外室结构的氧化反应器"或者 "塔式活塞流氧化反应器" 的任意组合;
(6)、 根据权利要求 2的 (1 )和 (2)所述的氧化反应器结构, 其特征在于采 用 3个、 4个乃至更多与反应器同轴心圆筒分室的四室、 五室、 多室氧化反应器, 液 相物料依照圆筒大小的次序分别从圆筒上部和下部与临近的室通联,有效分隔原料进 口与反应物料出口,有效形成物料流上下游关系; 各室气相相通, 有利于通过溶剂闪 蒸从反应器内部撤出反应热。
3、 根据权利要求 1、 2所述的精间苯二甲酸的制造方法, 其特征在 f控制氧化 反应器内部不同区域的温度范围,实现分段氧化,减少目标产物间苯二甲酸在氧化反 应条件下的停留时间, 降低间二甲苯的消耗, 氧化反应的温度范围是 130〜350°C, 压力范围是 0. 5〜14MPaG; 从反应物料上游到下游形成从低到高的温度梯度, 其中: 从间二甲苯到间位甲 基苯甲酸的高浓度区为低温区域, 反应温度为 130~21(TC , 降低反应温度, 减少醋 酸溶剂在高温条件下的停留时间, 降低醋酸消耗;
中间过渡区间为中温区, 反应温度为 180〜288 C ;
从间位甲基苯甲酸的高浓度区到间苯二甲酸溶液的区域为高温区域, 反应温度 为 210〜350°C。
4、 根据权利要求 1、 2、 3所述的精间苯二甲酸的制造方法, 其特征在于向氧化 反应器适当的区域添加水作为辅助溶剂,逐步降低醋酸在混合溶剂中的比例, 降低反 应物有机原料相在反应物液相的浓度,从而降低氧化反应活性,使得氧化反应速度在 反应物液相温度提髙的情况下受控平稳,减少醋酸溶剂的消耗、增加间苯二甲酸在溶 剂中的溶解度;
在氧化反应器内部大量生成间位甲基苯甲酸的位置开始少量逐步添加辅助水溶 剂,提高液相温度,在大量生成 3- CBA和间苯二甲酸的氧化反应区域液相物料中添加 更多的水作为间苯二甲酸和 3-CBA的溶剂,适当提高反应温度,增加间苯二甲酸在水 和醋酸混合溶剂中的溶解度参数,使得反应生成的间苯二甲酸和 3-CBA完全溶解在溶 剂中,在溶解状态下, 3- CBA很容易被氧化为间苯二甲酸;
提高反应温度也遏制了由于液相物料中增加水的含量, 反应物有机原料相在溶 液中浓度降低引起的氧化反应速度降低的趋势;
作为溶剂的水可以逐步添加到间位甲基苯甲酸到 3- CBA氧化反应区域, 也可以 添加到间位甲基苯甲酸高浓度区域之前的反应区域;
辅助溶剂水中可以添加适量醋酸, 以及催化剂和辅助催化剂;
醋酸溶剂、 溶剂水、 催化剂、 辅助催化剂循环使用;
从反应物料上游到下游, 水的含量由低到高形成梯度, 辅助溶剂水在混合溶剂 中的比例从初始的 0%到反应器出料口时增加到 100%;
采用环形水分布器;
在具有内外室结构的氧化反应器内室、具有内中外三室结构的氧化反应器内室, 以及塔式活塞流氧化反应器可以采用树形水分布器;
树形水分布器的树干水流方向是沿反应物料上下游方向, 从上游向下游流动, 一方面从上游取热撤热, 另一方面预热向下游供水的温度。
5、 根据权利要求 1、 2、 3、 4所述的精间苯二甲酸的制造方法, 其特征在于分 段添加催化剂和辅助催化剂;
针对卧式平推流氧化反应器、 塔式活塞流氧化反应器, 采用同时添加催化剂醋 酸钴、 醋酸锰和辅助催化剂氢溴酸的方法; 针对内外室结构氧化反应器、 内中外三室结构氧化反应器、 多反应器串联的氧 化反应器组合,采用先添加催化剂醋酸钴、醋酸锰,后添加辅助催化剂氢溴酸的方法。
6、 根据权利要求 1、 2、 3、 4所述的精间苯二甲酸的制造方法, 其特征是在塔 式氧化反应器液相顶部设置一个弱氧化反应区域,在尾气进入反应器气相之前,充分 吸收尾气中的氧气用于有效的氧化反应, 降低尾氧含量。
7、 根据权利要求 1、 4所述的精间苯二甲酸的制造方法, 其特征在于添加到氧 化反应器内部液相物料中的溶剂水, 可以采用列管换热的方式加热, 列管内部通水, 列管出口是向反应器液相添加水作为辅助溶剂的位置,列管埋在反应物液相物流的上 游, 外侧为反应物液相物料, 从上游物料反应热中取热。
8、 根据权利要求 1所述的精间苯二甲酸的制造方法, 其特征在于氧化反应原料 与溶剂的混合物可以采用预热进料的措施,釆用反应器内设列管换热进料的方法,从 反应物料流下游取热, 预热后原料出列管进入反应器反应体系。
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