CN106167451B - The method of meta-xylene and ethylbenzene multistep cooxidation production aromatic carboxylic acids - Google Patents
The method of meta-xylene and ethylbenzene multistep cooxidation production aromatic carboxylic acids Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
- C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
- C07C51/255—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting
- C07C51/265—Preparation 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
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
- C07C51/43—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/04—Purification; Separation; Use of additives by distillation
Abstract
The invention discloses a kind of methods of meta-xylene and ethylbenzene multistep cooxidation production aromatic carboxylic acids, the following steps are included: the paraxylene raffinate containing paraxylene, meta-xylene, ortho-xylene and ethylbenzene is carried out rectifying by (1) removes ortho-xylene, the mixture A containing meta-xylene and ethylbenzene is obtained；(2) mixture A is subjected to multistep oxidation and generates the mixture B containing M-phthalic acid and benzoic acid, M-phthalic acid crude product is gone out by Crystallization Separation, crystalline mother solution obtains benzoic acid by being concentrated by evaporation；(3) acetic acid and distilled water is respectively adopted to wash M-phthalic acid crude product, smart M-phthalic acid is obtained after dry.Each step and each unit operation all simple possibles of production process of the present invention, while being discharged without organic wastewater, it is a kind of economic and environment-friendly new process.
Description
Technical field
The present invention relates to a kind of production method of aromatic carboxylic acids more particularly to a kind of meta-xylenes and ethylbenzene multistep cooxidation
The method for producing aromatic carboxylic acids.
Background technique
Smart M-phthalic acid (PIA) is the raw material of polyester resin, is mainly used for polyester bottle slice, fiber, unsaturated-resin, low
The preparation of melt polyester product.The production method of PIA is to obtain thick isophthalic by liquid phase oxidation for raw material with meta-xylene (MX)
Dioctyl phthalate (CIA), the latter remove the trace impurity in product by hydrofinishing again, obtain polymer grade PIA.In Review literature
(Process EconomicsProgram Report 9E, Terephthalic Acid and Dimethyl
Terephthalate, SRI Consulting, Menlo Park, California, 94025, January 1997.) in detail
The method for describing various oxidations and purification, document (He Zuoyun, meta-xylene and M-phthalic acid production technology, synthesis
Fiber industry, the 2nd phase of volume 23,41~45,2000.) further supplemented with domestic progress.Due to the producer of PIA
Method is similar to the technique of p-phthalic acid (PTA) at many aspects, and production scale is less than PTA again, therefore some public affairs both at home and abroad
Department is usually by the PIA that changes the line of production after small-sized PTA plant modification.
Meta-xylene is the raw material of PIA, and the method overwhelming majority for obtaining MX at present is using mixed xylenes as raw material.Mesh
It is preceding to produce the main production process that mixed xylenes is mixed xylenes by raw material of petroleum.Crude oil obtains after atmospheric and vacuum distillation
Naphtha cut, the fraction are sent into reformer unit and generate a large amount of aromatic hydrocarbons, reformate be re-fed into Aromatics Extractive Project unit aromatics separation with
Non-aromatics, then by the heavy aromatics of benzene, toluene and 9 or more carbon in rectifying and separating aromatic hydrocarbons, 8 aromatic hydrocarbons mixture of carbon finally obtained
In contain meta-xylene (MX), paraxylene (PX), 4 kinds of ortho-xylene (OX), ethylbenzene (EB) ingredients, substantially content and physical
Matter is as shown in table 1.
Table 1 is using reformate as the 8 aromatic hydrocarbons each component content of carbon and physical property of waste
| Component | MX | PX | OX | EB |
| Content (%) | 45% | 20% | 20% | 15% |
| Boiling point (DEG C) | 139.1 | 138.4 | 144.4 | 136.2 |
| Fusing point (DEG C) | -47.8 | 13.2 | -25.2 | -95.0 |
It can be seen that the boiling point of 4 kinds of components is very close, other than ortho-xylene, other three kinds of substances are all difficult to pass through
Rectifying separation.Although the fusing point of 4 kinds of aromatic hydrocarbons has marked difference, can theoretically be separated by cryogenic crystallization, but the system exists
Multiple multi-component eutectic points, it is difficult to which, by Crystallization Separation, this all has been reported that in many monographs and document.Therefore, work at present
It is main in industry that MX raw material is still obtained using adsorbing separation.
MX is adsorbed using adsorption separating method with high selectivity, then MX is eluted using desorbing agent, this method is available
The MX of high-purity (MX > 99.5%).Patent CN200980125280.6, CN200610164101.8 individually discloses the special of MX
With adsorbent elements and adsorption conditions, patent CN200810100400.4 discloses the structure and absorbing process of MX adsorbent equipment.
(Zhao Yuzhang, Yang Jian, dimethylbenzene adsorbing separation-isomerization group technology produce between high-purity for patent CN98102372.X and document
Dimethylbenzene, petrochemical industry, the 1st phase of volume 29,32~36,2000.) then disclose the technique of vapor phase method adsorbing separation MX a kind of.
Absorption method is the meta-xylene production method of current industrializing implementation, its advantage is that the MX product purity obtained is high, to original
The wide adaptability of material.But absorption method operating process is complicated, needs the adsorbent using a large amount of valuableness, while also needing with special de-
Attached dose of desorption MX, the mixture desorbed pass through multiple tracks rectification step recycling strippant again and purify MX product.Therefore, it uses
Absorption method preparation MX is at high cost, and gained MX is expensive, limits the popularization and application in its market.
It is all as copolyesters ingredient and p-phthalic acid (PTA) one in most cases as the PIA of polyester raw material
It rises and uses.For example, the copolyesters as bottle chip level, PIA only accounts for the 2~3% of PTA, in low-melting point polyester PIA also only account for 20~
40%.Therefore, some patents in order to avoid separation MX problem, obtained using the method for mixed xylenes cooxidation PIA with
The mixed dicarboxylic acid product of PTA is to reduce the cost for preparing PIA.Patent CN200610154821.6 is proposed first to mix diformazan
Benzene is that raw material carries out liquid phase cooxidation, obtains the mixture of terephthalic acid (TPA), M-phthalic acid, phthalic acid, is recycled adjacent
Phthalic acid and to, significant difference of two kinds of carboxylic acids in solubility, obtains the mixture of PTA and PIA by Crystallization Separation,
Raw material as copolyesters.Similar scheme is repeatedly mentioned in subsequent patent.For example, patent CN201210014597.6
It proposes using the mixture of paraxylene (PX) and MX as raw material, addition part PX is aoxidized after being deployed into the composition of special ratios
And purification, produce the special raw material of various copolyesters.Patent CN200980109527.5 is proposed to contain mixed xylenes and ethylbenzene
C8 aronmatic be raw material, first by separation method appropriate remove C8 aronmatic in ethylbenzene, then by rectifying remove neighbour
Dimethylbenzene, remaining PX and MX mixture carry out liquid phase oxidation again and obtain PTA and PIA mix product.But the patent does not mention
Specific ethylbenzene separation method out, also without providing specific cooxidation condition.Ethylbenzene and paraxylene boiling point differ only by 1.8
DEG C, it is also very close in nature, it is difficult to separate.In view of this, patent CN200810022473.6 is proposed the carbon containing ethylbenzene
Eight aromatic hydrocarbons carry out the scheme of cooxidation, obtain the mixture of phenylacetic acid and three kinds of dicarboxylic acids.But it is general actually after ethylbenzene oxidation
Benzoic acid can be generated and be hardly produced phenylacetic acid, the scheme mentioned is difficult to carry out, and the mixed polycarboxylic acid purposes of generation also extremely has
Limit.Therefore, in order to obtain MX and PIA at low cost, it is necessary to look for another way, using new idea and method.
Summary of the invention
The present invention provides a kind of methods of meta-xylene and ethylbenzene multistep cooxidation production aromatic carboxylic acids, and this method can be low
Cost production meta-xylene recycles ortho-xylene (OX) simultaneously, and obtains M-phthalic acid by the oxidation of meta-xylene.
A method of producing paraxylene co-production meta-xylene, comprising: paraxylene (PX), meta-xylene will be contained
(MX), the 8 aromatic hydrocarbons mixture adsorbing separation of carbon of ortho-xylene (OX) and ethylbenzene (EB) goes out paraxylene, obtains containing to diformazan
Benzene, meta-xylene, ortho-xylene and ethylbenzene paraxylene raffinate, after part paraxylene raffinate carries out isomerization reaction
Merge with 8 aromatic hydrocarbons mixture of carbon；Another part paraxylene raffinate carries out rectifying and removes ortho-xylene, diformazan between being contained
The mixture of benzene and ethylbenzene.
The isomerization reaction is to convert the mixing containing paraxylene for meta-xylene, ortho-xylene and part ethylbenzene
Dimethylbenzene, while will partially be difficult to the ethylbenzene converted removing ethyl and removing.
A kind of method of meta-xylene and ethylbenzene multistep cooxidation production aromatic carboxylic acids, comprising the following steps:
(1) the paraxylene raffinate containing paraxylene, meta-xylene, ortho-xylene and ethylbenzene is subjected to rectifying removal
Ortho-xylene obtains the mixture A containing meta-xylene and ethylbenzene；
(2) mixture A is subjected to multistep oxidation and generates the mixture B containing M-phthalic acid and benzoic acid, pass through crystallization
M-phthalic acid crude product is isolated, crystalline mother solution obtains benzoic acid by being concentrated by evaporation；
(3) acetic acid and distilled water is respectively adopted to wash M-phthalic acid crude product, smart isophthalic two is obtained after dry
Formic acid.
In step (1):
Paraxylene raffinate is after adsorbing separation goes out paraxylene, contains meta-xylene, ortho-xylene, ethylbenzene and on a small quantity
8 aromatic hydrocarbons mixture of carbon of paraxylene.
In terms of mass percent concentration, less than 1%, meta-xylene content is paraxylene content in paraxylene raffinate
65~70%, ortho-xylene content is 20~30%, and ethyl-benzene level is 3~10%.Further, in paraxylene raffinate
For paraxylene content less than 1%, meta-xylene content is 65~69%, and ortho-xylene content is 25~28%, ethyl-benzene level 5
~8%.
The boiling point of OX differs 5.3 DEG C with MX, preferably, separating ortho-xylene, operating condition using rectifying column rectifying are as follows:
It being fed from rectifying column middle and lower part, theoretical cam curve is 70~120, and overhead reflux is than 10~20,139~141 DEG C of tower top temperature, tower
155~170 DEG C of bottom temperature.
Under the operating conditions described above, the mixture A of the OX content MX less than 0.3% and EB is obtained from the top of the distillation column,
Middle MX content is greater than 90%, EB content less than 10%, as the original for further producing smart M-phthalic acid (PIA) and benzoic acid
Material；Rectifying tower bottom obtains the heavy distillat of OX content > 85%, and heavy distillat can be sent into isomerization unit and be converted into mixed xylenes
Merge with 8 aromatic hydrocarbons mixture of carbon for adsorbing PX processed, can also further rectifying high-purity OX product.
In step (2):
It is always a technical difficult point that EB is separated from 8 aromatic hydrocarbons of carbon.Only poor 3 DEG C of the boiling point of EB and MX, it is difficult to rectifying
Cutting.Although the two different melting points are larger, can theoretically be separated with cryogenic crystallization, the characteristics of Crystallization Separation is that yield is lower,
There is quite a few MX to be still difficult to recycle in mother liquor, cryogenic separation higher cost.
Mixture A containing MX and EB is carried out multistep cooxidation by the present invention, preferably, when oxidation mixture A, with vinegar
Acid is solvent, and cobalt salt, manganese salt, hydrogen bromide are catalyst, and oxidant is oxygen-containing gas.
Preferably, the cobalt salt is cobalt acetate, manganese salt is manganese acetate.
Preferably, oxygen-containing gas is air.
Preferably, the operating condition of main oxidation are as follows: temperature is 180~210 DEG C, and pressure is 1.0~1.5MPa, with solvent
The mean residence time meter reaction time be 45~90 minutes, the weight ratio for feeding acetic acid and meta-xylene is 2~4: 1, with original
Sub- densimeter catalyst concn are as follows: Co is 200~500ppm, and Mn is 200~500ppm, and Br is 400~1000ppm.
Under above-mentioned oxidizing condition, two methyl on MX are successively oxidized to corresponding alcohol, aldehyde, acid, between being finally translated into
Phthalic acid (IA), MX conversion ratio are greater than 98%, and the yield of coarse isophthalic acid is greater than 94%.
It is had shown that through research, the ethyl on ethylbenzene is more active, and under above-mentioned oxidizing condition, ethyl can be by gradually oxidation transformation
At mono carboxylic, ethylbenzene is converted into benzoic acid (BA), and EB conversion ratio is greater than 99%, BA yield and is greater than 96%.
Solubility of the benzoic acid of generation in acetic acid solvent is very big, and the two constitutes dicarboxylic acids cosolvent, this total
Solvent has facilitation to the oxidation of alkylaromatic hydrocarbon, can speed up oxidation reaction.Therefore, the generation of benzoic acid is a kind of advantageous
In the factor of meta-xylene and ethylbenzene oxidation.On the other hand, the solubility due to benzoic acid in solvent acetic acid and water is much big
In M-phthalic acid, both oxidation products are easy for making M-phthalic acid be enriched in solid phase and benzoic acid by Crystallization Separation
It is enriched in liquid phase, to obtain two kinds of acid products respectively.
Subsequent multistep oxidation is carried out to the reaction solution after main oxidation, by a small amount of reactant not converted completely and intermediate production
Object depth degree is oxidized to product.
By multistep oxidation can by main oxidation after reactant in reaction solution and intermediate product be completely converted into product isophthalic
Dioctyl phthalate and benzoic acid are refined without repeated hydrogenation.Through studying, this is feasible, because of the isophthalic diformazan that oxidation generates
Solubility of the acid in acetic acid solvent is also bigger, and under oxidizing condition appropriate, reactant, intermediary and product all dissolve
In a solvent, without or rarely solid be precipitated, this allow for the unreacted reactant dissolved in liquid phase can be aoxidized by multistep it is several
It is completely converted into final product, becomes impurity without being wrapping in solid.
It should be noted that multistep oxidation technology was also once suggested in the past, produce for p xylene oxidation to benzene
The process of dioctyl phthalate, such as patent US4877900, US 4772748, JP 59-93029 are just proposed early in the 1980's using 3
The oxidation of~4 steps converts polymer grade terephthalic acid (TPA) without hydrofinishing step for PX；Patent US2002/0183546A1,
The scheme that CN02810929.5 also discloses its two-step oxidation before more than ten years prepares medium purity TPA, the present inventor
The method of heating and oxidation step by step is proposed in patent CN201210238659.1 before the several years.But these multisteps or multistage
One common feature of oxidation technology is that the oxidizing condition of subsequent step is all more harsher than first step oxidizing condition, for example,
The temperature of second oxidation will be 40~60 DEG C higher than the first step, the high 1~3MP of pressure.This is because generated in oxidation process one
Solubility of a little intermediaries such as p -carboxybenzaldehyde (4-CBA) and foreign pigment and product terephthalic acid in acetic acid is all very
Small, it is solid that cocrystallization, which is precipitated, immediately after generation, and the impurity wrapped up in solid can only ooze out solid at higher temperatures
Body enters liquid phase and is oxidized.However for meta-xylene oxidation, then situation is significantly different, and the intermediary and product of reaction dissolve
Degree is big, main oxidation and few solids in the liquid phase of secondary oxidation step, thus by multistep oxidation is easy will be in liquid phase
Between object be totally converted.Therefore, the multistep method for oxidation that the present invention uses is substantially distinguished from the scheme proposed in the past, is exactly main oxidation
Later secondary or three times oxidation step all aoxidize the temperature, pressure condition more mitigated using than main, are more convenient for implementing in this way,
Equipment investment and the consumption of raw material are reduced simultaneously.
Preferably, the present invention uses two-step oxidation, but be not restricted to that two-step oxidation.
Preferably, the operating condition of secondary oxidation are as follows: temperature is 170~207 DEG C, and pressure is 0.8~1.4MPa, with molten
The mean residence time meter reaction time of agent is 45~90 minutes, and the weight ratio for feeding acetic acid and meta-xylene is 2~4: 1, with
Atomic concentration meter catalyst concn are as follows: Co is 200~500ppm, and Mn is 200~500ppm, and Br is 400~1000ppm.
The operating condition of secondary oxidation is more relatively mild than the operating condition of main oxidation, and temperature is 3~10 DEG C low, pressure low 0.1
~0.2MPa.
After two-step oxidation, solid content < 5% in slurry, the concentration < of carboxyl benzaldehyde (3-CBA) between impurity
40ppm。
After above-mentioned two-step oxidation, MX and EB have been oxidized completely, and representative intermediary 3-CBA is in mother liquor
Concentration have been reduced to the level of trace.
Oxidation reactor can be bubble tower, gas-liquid agitation kettle and other kinds of gas-liquid contact and reaction unit.
Crystalline element decompression cooling is sent into containing the mixture B of M-phthalic acid and benzoic acid in the part for reacting output, with
Solid IA is precipitated.
Preferably, using multistage crystallizer when crystallization, crystallizer decompression step by step coolings at different levels are to be precipitated M-phthalic acid.
Purpose using multistage crystallization is to control the degree of supersaturation of crystallizers at different levels to be conducive to growing up for crystal.
Preferably, being passed through oxygen-containing gas in the first crystallizer for reactant and intermediate product remaining in mixture B
Deep oxidation.
Oxygen-containing gas is passed through in the first crystallizer makes reactant and intermediate product deep oxidation remaining in mixture B,
So that the M-phthalic acid being precipitated reaches polymer grade requirement.
The temperature of afterbody crystallizer decides the rate of recovery of solid product.For the crystallization process of M-phthalic acid,
The pressure of afterbody crystallizer will generally vacuumize to form negative pressure to reduce temperature, and IA product is precipitated in crystallization to the maximum extent.
Preferably, the operating condition of afterbody crystallizer are as follows: pressure be -0.05~-0.08MPa, temperature be 80~
100 DEG C, solid holdup is 36~40% in obtained slurry of solids.
The solid holdup is the ratio of the quality and slurry of solids gross mass of solid in slurry of solids.
Since solubility of the benzoic acid in acetic acid is far longer than M-phthalic acid, the precipitation of product M-phthalic acid is solid
Body, product benzoic acid are still enriched in the liquid phase, can separate both products by solid-liquor separation.
The output slurry of above-mentioned afterbody crystallizer is sent into liquid/solid separation unit, passes through filtering, centrifugation or other liquid
Solid separation method obtains M-phthalic acid filter cake and the oxidation mother liquor containing benzoic acid.A part of oxidation mother liquor directly returns to oxidation
Reactor, another part oxidation mother liquor are sent into benzoic acid separative unit and evaporate solvent acetic acid, obtain solid benzoic acid product.
Mass ratio of the extraction for separating total oxidation mother liquor shared by the stream stock A of benzoic acid is 15~95% in oxidation mother liquor, extraction stream
The ratio of stock A is higher, and the concentration of benzoic acid is lower in oxidation mother liquor, the benzoic acid carried secretly in M-phthalic acid cake solids
It is lower.The crude benzol formic acid purity that oxidation mother liquor evaporates is 95~98%, can pass through further rectification under vacuum or recrystallization
Obtain the product of higher purity.The solvent acetic acid evaporated from benzoic acid separative unit is all sent to subsequent pickling unit conduct
The pickling cleaning solution of M-phthalic acid filter cake.
The heat and water that main oxidation reactor and secondary oxidation reactor generate remove reactor by the evaporation of solvent, by
Oxidized tail gas carrier enters solvent dehydration tower, and function is mainly the water deviating from reaction and generating.
The top that solvent dehydration tower can be directly installed on main oxidation reactor is connected with reactor, can also be independent
It is external.
The amount of the oxidized tail gas of secondary oxidation reactor is much smaller than the oxidized tail gas of main oxidation reactor, and pressure is lower, can
Will not coagulate tail gas after can also individually condensing and be sent directly into tail gas treating unit with solvent dehydration tower is sent into after compressor boost
Purified treatment.
The dehydration acetate partial reflux of solvent dehydration tower tower bottom enters main oxidation reactor, and part extraction is used as step (3)
The cleaning solution of middle pickling.
The vapor of tower top tail gas containing inertia enters condenser, and condensate liquid about 1/3 flows back into solvent dehydration as recirculation water
Tower, about 2/3 extraction is as the washing water washed in step (3).
Incoagulable gas in condenser discharges after being sent into tail gas treating unit purification.
Condenser uses multi-stage condensing mode generally in order to generate different grades of steam to recycle the heat of tail gas.
In step (3):
In the M-phthalic acid filter cake obtained by liquid/solid separation unit containing 10~30% oxidation mother liquor, in oxidation mother liquor
Contain benzoic acid and other trace impurities, it is necessary to be removed.
M-phthalic acid filter cake is sent to pickling unit, to remove the oxidation mother liquor carried secretly in M-phthalic acid filter cake.
The regenerated solvent acetic acid that pickling cleaning solution a part of pickling unit uses benzoic acid separative unit to evaporate, one
Divide the dehydration acetate using solvent dehydration tower tower bottom, pickling cleaning solution and the butt quality ratio of M-phthalic acid filter cake are 1~3:
1。
Pickling mother liquor after pickling returns to main oxidation reactor and makees solvent, and the M-phthalic acid solid after pickling is sent to washing
Unit.
The equipment of pickling unit can use currently used wash mill, such as be beaten tank, filter, countercurrent washing tower,
Belt spray washing device, etc. can be single-stage washing, multi-stage countercurrent washing can also be used to improve efficiency, wherein liquid
Gu countercurrent washing is most efficient mode of washing, the adverse current that can be introduced in patent CN201010241238.5 referring to inventor is washed
Wash apparatus and method for.
The oxidation mother liquor carried secretly in M-phthalic acid solid after pickling most (95~99.5%) is removed,
But there is still a need for further remove so that product reaches polymer grade requirement for remaining micro benzoic acid and acetic acid in filter cake.For this purpose,
Also need a water-washing step.
The M-phthalic acid solid that pickling unit exports is sent to washing unit, is produced using solvent dehydration tower overhead condenser
Raw distilled water is washed again, and the butt quality ratio of distilled water used and M-phthalic acid solid is 1~3: 1.
The equipment and technology for washing unit can also use the device and process similar with pickling unit, be not repeated to chat
It states.
Washing mother liquor after washing is all sent into recirculation water of the solvent dehydration top of tower as solvent dehydration tower.
If being sent to washing unit again after the M-phthalic acid solid drying after pickling, the washing mother liquor for washing unit contains
Acid amount is extremely low, and solvent dehydration tower top is sent into after can merging with the recirculation water of condenser；And if M-phthalic acid after pickling
Solid is sent to washing unit without dry in a manner of filter cake, then washing mother liquor contains a small amount of acetic acid, and two strands of phegmas are with regard to suitable
It is individually sent into solvent dehydration tower, the reflux inlet for washing mother liquor in this case should lower than the phegma of condenser 2
~5 blocks of column plates, the specific backwash deployment for washing mother liquor are easy to be determined according to its acid concentration in solvent dehydration Deethanizer design.
It is smart M-phthalic acid product, major impurity 3- in the product after M-phthalic acid solid drying after washing
CBA content < 20ppm, benzoic acid content < 20ppm, terephthaldehyde's acid content < 1% meet the matter of most polyester products
Amount requires.
If further increasing the ratio of the oxidation mother liquor Extract for separating benzoic acid, increase pickling and washing solvent
Dosage improves the efficiency of multi-stage countercurrent washing, then impurity content can also further decrease in product.
Compared with prior art, the invention has the benefit that
(1) present invention only separates OX by rectifying from paraxylene (PX) raffinate and just obtains rich in meta-xylene simultaneously
Oxidic raw materials containing a small amount of ethylbenzene avoid expensive MX adsorption separating method, then are washed just by two step cooxidation and two steps
The fine terephthalic acid products for meeting production of polyester requirement are obtained, it is severe to eliminate condition for the benzoic acid product of by-product technical grade
M-phthalic acid and benzoic acid product can be mass produced in the hydrofinishing step at quarter in inexpensive manner, realize PX production
The higher value application of the raffinate generated in the process；
(2) method provided by the invention is used, it is per ton to contain meta-xylene 91.5%, ethylbenzene 7.5%, paraxylene 1.0%
Material liquid about 1.4 tons of essence M-phthalic acids (PIA) and 0.085 ton of benzoic acid can be obtained by two-step oxidation and the washing of two steps
(BA), 3-CBA content < 20ppm in gained PIA, benzoic acid content < 20ppm, terephthalic acid (TPA) about 1%, benzoic acid product is pure
Degree > 98%, the yield and purity of product are relatively high；
(3) each step of production process of the present invention and each unit operation all simple possibles, while being discharged without organic wastewater, it is
A kind of economic and environment-friendly new process.
Detailed description of the invention
Fig. 1 is the flow chart that the present invention produces meta-xylene and ethylbenzene by raw material of 8 aromatic hydrocarbons of carbon；
Fig. 2 is the flow chart that the present invention produces smart M-phthalic acid and benzoic acid using meta-xylene and ethylbenzene as raw material.
Specific embodiment
Present invention is further described in detail with reference to the accompanying drawings and examples, it should be pointed out that reality as described below
It applies example to be intended to convenient for the understanding of the present invention, and does not play any restriction effect to it.
1, the production of meta-xylene
As shown in Figure 1, a typical PX process units, produces aromatic hydrocarbons and absorption method from carbon using naphtha reforming process
PX is separated in 8 aromatic hydrocarbons, main flow includes adsorbing separation and two modules of isomerization.8 aromatic hydrocarbons of carbon containing composition shown in table 1 is mixed
It closes after object S100 is mixed with the equiulbrium flow stock S104 that isomerization unit exports and is sent into PX absorbing unit U101 together, through adsorbing separation
The PX product that purity is 99.5% is obtained afterwards, and by stream stock S101 output system, raffinate S102 is sent into isomerization reactor U102
The equilibrium composition S104 containing PX is converted by raw material S102, while removing part ethylbenzene, then adsorbs and divides after being mixed with raw material S100
It from PX, loops back and forth like this, until raw material conversion is complete.MX in order to obtain, the present invention draw one from PX raffinate S102
Point, it is labeled as S105, is separated off by rectifying and obtains the stream stock S107 rich in MX after OX.
The composition of the PX raffinate S105 of extraction is as follows:
MX 67%, OX 27.5%, EB 5%, PX 0.5%.
The S105 of above-mentioned composition is sent into rectifying column U103, removes ortho-xylene OX, rectifying column condition is:
Theoretical cam curve 100, feed tray position are the 65th piece (from top to bottom sequence), 158 DEG C of feeding temperature, tower top
Reflux ratio 16,167.8 DEG C of column bottom temperature, 139.2 DEG C of tower top temperature, tower top pressure is normal pressure.
Under the above conditions, charging S105 per ton can get 0.70 ton of overhead fraction S107,0.3 ton of tower bottom distillate S106,
The composition of two kinds of fractions is respectively as follows:
S107:MX 91.5%, EB 7.5%, PX 0.7%, OX 0.3%
S106:MX 10.6%, EB0.01%, PX 0.1%, OX 89.3%
Obtained stream stock S107 is rich in MX, while containing a small amount of EB and trace P X and OX, and the raw material as cooxidation is sent into
Oxidation unit.
2, multistep cooxidation
It is added material liquid S107 obtained by the above method as the feeding flow stock S200A of oxidation reactor U201 in Fig. 2
The reactor, while the also catalyst S200B and circulating mother liquor S200C (predominantly acetic acid) being added.Simultaneously be blown into air into
Row liquid phase oxidation.Main oxidation reactor is a bubbling column reactor without mixing, and condition is listed in table 2.
The main oxidation reactor U201 operating condition of table 2
MX/HAc indicates the mass ratio of MX and acetic acid (HAc) in feeding flow stock S200 in table, and pressure is tower top gauge pressure, solution
Residence time=volume of mixture/solvent acetic acid flow, tail gas oxygen concentration refer to the butt concentration of oxygen in S210.
Under the above conditions, the reaction result of reactor U201 is listed in table 3.
The main oxidation reactor U201 reaction result of table 3
3-CBA refers to carboxyl benzaldehyde between main reaction intermediates in table, it is all to need to remove together with foreign pigment
Major impurity.The stream stock S201 of output, simultaneously there are also complete raw material and intermediate product is not aoxidized on a small quantity, is sent into two rich in IA
Secondary oxidation reactor U202, the reactor are a gas-liquid agitation kettles, and reaction condition is listed in table 4, and oxidation results are listed in table 5.
4 secondary oxidation reactor U202 operating condition of table
5 secondary oxidation reactor U202 reaction result of table
Crystalline element U203 uses three-level crystallizer, solvent is evaporated under reduced pressure step by step, while solid IA is precipitated, wherein the first knot
Brilliant device is passed through a small amount of air supplement oxidation, and oxidation reactor U202 is failed to the liquid phase reactor object deep conversion of conversion.Three-level knot
The condition and result of brilliant device are listed in table 6.
6 three-level crystallizer U203 condition of table and result
The slurry of crystallizer U203 output is sent into liquid/solid separation unit U204, by vacuum filter by oxidation mother liquor and solid
IA separation, obtains M-phthalic acid filter cake S204A, which contains oxidation mother liquor 15%, containing 4.5% benzoic acid and its in mother liquor
Its trace impurity is sent into pickling unit U206 washing.
The mother liquor of liquid/solid separation unit U204 output is divided into two strands, and it is anti-that 50% mother liquor S204B is recirculated directly back to oxidation
Device U201 is answered, benzoic acid separative unit U205 is sent in the other half mother liquor S204C extraction, in the unit, by the solvent in mother liquor
Acetic acid evaporation, acetic acid S205 are sent into pickling unit U206 and are used as washing lotion, and the benzoic acid molten liquid of concentration further passes through vacuum fine
It evaporates and is purified to 98% or higher purity, discharged after a small amount of higher boiling Slag recovering catalyst at rectifying column bottom.In extraction 50%
Under conditions of mother liquid evaporation separates benzoic acid, the concentration that can control liquid phase benzoic acid in oxidation reactor is no more than 5%.
3, pickling, washing
The filter cake S204A of the water capacity 15% of liquid/solid separation unit U204 output is sent into pickling unit U206, with clean
Acetic acid solvent is washed to remove the impurity content in the reduction solid product of the mother liquor in filter cake.There are two come for washing lotion acetic acid
Source: a part is the solvent S205 of benzoic acid separative unit U205 evaporation, in addition secondary oxidation reactor U202 and three-level crystallization
The acetic acid of device tower top evaporation, the mass ratio about 1: 1 of this part acetic acid amount and dry basis；Second part is the vinegar that flows back from dehydrating tower
A part of S208C is drawn in sour S208B, the mass ratio about 0.5: 1 of this part acetic acid amount and dry basis.The heat exchange of two parts acetic acid
It cools down and temperature is adjusted to about 120 DEG C after recovering energy, be then fed into scrubbing tower and filter cake counter current contacting is washed.Scrubbing tower is one
The vertical mixing liquid that a inventor introduced in patent CN201010241238.5 is solid counter-flow moving bed, and filter cake adds from tower top
Enter, bottom discharge, washing lotion is added from tower lower part, and top discharge is further cooled to 90 DEG C of a small amount of solids that precipitation is recovered by filtration
After be sent into main oxidation reactor U201.After carrying out countercurrent washing to solid using the acetic acid of 1.5 times of weight, the mother that is carried secretly in filter cake
99.5% or more liquid is replaced by fresh acetic acid, and filter cake is dried, after removing most of acetic acid, remaining benzoic acid in solid
Concentration still has about 300ppm, and acetic acid remains 60ppm, also needs further to wash the remaining benzoic acid of removing and acetic acid.
The solid S206A of pickling unit output is sent into the micro benzoic acid that washing unit U207 washes away remaining after dry,
The distilled water S209 that unit washing lotion uses dehydrating tower evaporator overhead condenser U209 to generate is washed, 2/3 feeding scrubbing tower is drawn it out
The lower part U207, with solid S206A counter current contacting.Washing unit U207 is also the solid adverse current of a liquid similar with pickling unit U206
The mass ratio of moving bed, washing water and solid still uses 1.5: 1, and the feeding temperature of cleaning solution is adjusted to 100 DEG C, adds from tower lower part
Enter top output, is then all sent into dehydrating tower as phegma S207.Solid is carried out using the distilled water of 1.5 times of weight inverse
After stream washing, filter cake is dried, and obtains smart M-phthalic acid solid product.The butt residual quantity about 15ppm of benzoic acid at this time,
The content of remaining component in solid are as follows: PIA99.3%, PTA0.7%, 3-CBA 20ppm.
The tail gas S201B exported at the top of main oxidation reactor is sent into the water that rectifying column U208 elimination reaction generates, rectifying column
The dehydration acetate S208B partial reflux of U208 tower bottom enters oxidation reactor, and part extraction is sent to acid as pickling washing lotion S208C
Wash unit；The vapor of tower top tail gas containing inertia enters condenser U209, and condensate liquid S209 partial reflux to dehydrating tower U208 is made
For recirculation water S209C, part extraction is sent into washing unit U207 as the washing water S209B of washing unit.In condenser U209
Incoagulable gas be sent into tail gas treating unit U210 purification after discharge.The parameter of solvent dehydration tower U208 are as follows: 60 pieces of theoretical towers
Version, 196 DEG C of column bottom temperature, 180 DEG C of tower top temperature, in rectifier column reflux liquid, overhead condensate reflux liquid S209C and washing mother liquor are returned
The ratio of flow liquid S207 is 1: 2, and acetic acid content < 50ppm in the fixed gas of discharge can pass through further condensing recovery.Secondary oxygen
It is less to change the top reactor U202 tail gas amount, is directly condensed using condenser, lime set merges with S208C is sent to pickling unit
U206, not solidifying tail gas are routed directly to Tail gas cleanup unit U210.
In the present embodiment, solvent dehydration tower is divided into two sections: one sections and is directly installed on main oxidation containing 5~15 blocks of theoretical trays
The top of reactor U201, is connected with bubble tower, collectively forms main oxidation unit U201, if the present inventor is previous special
Sharp CN200420107473.3, as CN200510048977.1 is introduced；Another section of rectifying column is individually external, contains 45~55
Block theoretical plate constitutes dehydrating tower unit U208.The dehydration that the tail gas and steam that main oxidation reactor U201 is generated pass through upper part
After section separate section acetic acid and the drop or particulate matter of tail gas entrainment, separate acetic acid and water into dehydrating tower U208, vapor with
Incoagulable gas enters condenser U209 from tower top and obtains distilled water S209, after incoagulability tail gas is sent into U210 Recovery Purifying pressure energy
It discharges, 1/3 flows back into U208 in condensed water U209, and 2/3 extraction is sent to mother liquor of the washing unit U207 as washing water, after washing
S207 returns to dehydrating tower U208 together with recirculation water S209C.The water-containing acetic acid S208B that dehydrating tower tower bottom generates extracts 0.5 times out admittedly
The liquid S208C of body S204A weight is sent into pickling unit U206 together with the acetic acid S205 that benzoic acid separator generates, acid
Mother liquor S206B after washing sends main oxidation reactor back to.In this way by the dehydrating tower U208 distilled water generated and fresh acetic acid
It is used for the washing of solid filter cake to the maximum extent, on the one hand reduce the impurity content of solid entrainment, on the one hand greatly
Reduce the discharge of organic wastewater.
In the present embodiment, per ton to pass through containing meta-xylene 91.5%, ethylbenzene 7.5%, the material liquid of paraxylene O.5%
Two-step oxidation and the washing of two steps can obtain about 1.4 tons of smart M-phthalic acids (PIA) and 0.085 ton of benzoic acid (BA), gained PIA
Middle 3-CBA content < 20ppm, benzoic acid content < 20ppm, terephthalic acid (TPA) < 1%, benzoic acid product purity > 98%.This
Each step and each unit operation all simple possibles of invention production process, while being discharged without organic wastewater, it is a kind of economic and environment-friendly
New process.
Technical solution of the present invention and beneficial effect is described in detail in embodiment described above, it should be understood that
Above is only a specific embodiment of the present invention, it is not intended to restrict the invention, it is all to be done in spirit of the invention
Any modification, supplementary, and equivalent replacement etc., should all be included in the protection scope of the present invention.
Claims (9)
1. a kind of method of meta-xylene and ethylbenzene multistep cooxidation production aromatic carboxylic acids, which comprises the following steps:
(1) the paraxylene raffinate containing paraxylene, meta-xylene, ortho-xylene and ethylbenzene is subjected to rectifying removal neighbour two
Toluene obtains the mixture A containing meta-xylene and ethylbenzene；
In the mixture A, meta-xylene content is greater than 90%, and less than 0.3%, ethyl-benzene level is less than ortho-xylene content
10%；
(2) mixture A is subjected to multistep oxidation and generates the mixture B containing M-phthalic acid and benzoic acid, pass through Crystallization Separation
M-phthalic acid crude product out, crystalline mother solution obtain benzoic acid by being concentrated by evaporation；
The operating condition of main oxidation are as follows: temperature is 180~210 DEG C, and pressure is 1.0~1.5MPa, when with the average stop of solvent
Between the meter reaction time be 45~90 minutes, the weight ratio for feeding acetic acid and meta-xylene is 2~4:1, is catalyzed in terms of atomic concentration
Agent concentration are as follows: Co is 200~500ppm, and Mn is 200~500ppm, and Br is 400~1000ppm；
Compared with main oxidation, the oxidation step after main oxidation is using the reaction condition more mitigated；
(3) acetic acid and distilled water is respectively adopted to wash M-phthalic acid crude product, smart M-phthalic acid is obtained after dry.
2. the method for production aromatic carboxylic acids according to claim 1, which is characterized in that right in terms of mass percent concentration
Paraxylene content is less than 1% in dimethylbenzene raffinate, and meta-xylene content is 65~70%, and ortho-xylene content is 20~
30%, ethyl-benzene level is 3~10%.
3. the method for production aromatic carboxylic acids according to claim 1, which is characterized in that in step (1), using rectifying column essence
Fraction is from ortho-xylene, operating condition are as follows: feeds from rectifying column middle and lower part, theoretical cam curve is 70~120, and overhead reflux is than 10
~20,139~141 DEG C of tower top temperature, 155~170 DEG C of column bottom temperature.
4. the method for production aromatic carboxylic acids according to claim 1, which is characterized in that when oxidation mixture A, be with acetic acid
Solvent, cobalt salt, manganese salt, hydrogen bromide are catalyst, and oxidant is oxygen-containing gas.
5. it is according to claim 1 production aromatic carboxylic acids method, which is characterized in that in step (2), by mixture A into
Row two-step oxidation generates the mixture B containing M-phthalic acid and benzoic acid.
6. the method for production aromatic carboxylic acids according to claim 5, which is characterized in that the operating condition of secondary oxidation are as follows:
Temperature is 170~207 DEG C, and pressure is 0.8~1.4MPa, and the reaction time is 45~90 points in terms of the mean residence time of solvent
Clock, the weight ratio for feeding acetic acid and meta-xylene is 2~4:1, the catalyst concn in terms of atomic concentration are as follows: Co is 200~
500ppm, Mn are 200~500ppm, and Br is 400~1000ppm.
7. the method for production aromatic carboxylic acids according to claim 1, which is characterized in that in step (2), using more when crystallization
Grade crystallizer, the operating condition of afterbody crystallizer are as follows: pressure is -0.05~-0.08MPa, and temperature is 80~100 DEG C, is obtained
To slurry of solids in solid holdup be 36~40%.
8. the method for production aromatic carboxylic acids according to claim 1, which is characterized in that in step (2), oxidation reaction is produced
Raw oxidized tail gas is sent into the water that solvent dehydration tower rectifying elimination reaction generates, and the dehydration acetate part of solvent dehydration tower tower bottom is returned
Stream enters oxidation reactor, cleaning solution of the part extraction as pickling in step (3)；The vapor of tower top tail gas containing inertia enters
Condenser, partial condensation liquid flow back into solvent dehydration tower as recirculation water, and another part condensate liquid is as washing in step (3)
Washing water, washing mother liquor are back to solvent dehydration tower as recirculation water again.
9. the method for production aromatic carboxylic acids according to claim 1, which is characterized in that in step (2), crystalline mother solution evaporation
When being concentrated and separated benzoic acid, cleaning solution of the recovered solvent acetic acid as pickling in step (3), pickling mother liquor reflux to oxygen are evaporated
Change reactor as solvent.
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| CN108003006A (en) * | 2017-11-17 | 2018-05-08 | 杭州多向流化学科技有限公司 | A kind of method that terephthalic acid (TPA) and M-phthalic acid are produced using C8 aronmatic as raw material |
| CN108046971A (en) * | 2017-11-17 | 2018-05-18 | 杭州多向流化学科技有限公司 | Using mixed xylenes as raw material aromatics separation and the method for preparing M-phthalic acid |
| CN109251139B (en) * | 2018-11-02 | 2021-06-25 | 中国石油天然气集团有限公司 | PIA production method and production system adopting deep oxidation |
| CN109865493A (en) * | 2019-01-31 | 2019-06-11 | 浙江大学 | A kind of twin drum bubble column reaction unit and reaction process for p xylene oxidation |
| CN111569454B (en) * | 2020-03-31 | 2021-07-09 | 南京延长反应技术研究院有限公司 | Built-in micro-interface oxidation system and method for preparing terephthalic acid from p-xylene |
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| CN1512976A (en) * | 2001-06-04 | 2004-07-14 | �Ϻ���ͨ��ѧ | Two stage oxidation process for production of aromatic dicarboxylic acids |
| CN1962598A (en) * | 2006-11-23 | 2007-05-16 | 浙江大学 | Method for producing benzene dicarboxylic acid by mixed dimethylbenzene cooxidation |
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