CN100582067C - Method of recovering unreacted alkylbenzene in process of preparing aromatic carboxyl acid - Google Patents
Method of recovering unreacted alkylbenzene in process of preparing aromatic carboxyl acid Download PDFInfo
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- CN100582067C CN100582067C CN200510095961A CN200510095961A CN100582067C CN 100582067 C CN100582067 C CN 100582067C CN 200510095961 A CN200510095961 A CN 200510095961A CN 200510095961 A CN200510095961 A CN 200510095961A CN 100582067 C CN100582067 C CN 100582067C
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Abstract
The invention discloses a non-reacted dialkyl benzene recycling method from boiled distilled acetate dehydrating tower, which comprises the following steps: adopting iso-butyl acetate as entrainer; controlling the entrainer area at 94-100 deg.c; separating the distilled liquid from bottom of liquid reserving groove; recycling organic distilled phase to entrainer area.
Description
Technical field
The present invention relates to retrieve in the comfortable acetate solvate, under the existence of heavy metal catalyst, make alkylbenzene in liquid phase, adopt the oxidizing reaction of molecularity carrier of oxygen to make the method for the unreacted alkylbenzene of aromatic carboxylic acid operation, at length say, relate to from recovery system and reclaim, be used to again method from the unreacted alkylbenzene of alkylbenzene oxidizing reaction as reaction solvent acetic acid.
Technical background
Make dimethylbenzene or m-xylene with acetic acid be solvent in the presence of heavy metal catalyst, adopt the molecularity carrier of oxygen to carry out liquid-phase oxidation, the method for making terephthalic acid or m-phthalic acid is suitability for industrialized production generally.
The manufacture method of these aromatic dicarboxylic acids, carry out in the reaction process of liquid-phase oxidation at dialkyl benzene as p-Xylol or m-xylene, in order to remove reaction heat, unreacted dialkyl benzene is discharged from reactor with the acetic acid steam as reaction solvent with the reactor off-gas of discharging.And this waste gas of being discharged and steam are in the heat recycle process that is cooled with condensation, and most unreacted dialkyl benzene is recycled to reaction process with solvent acetic acid and is recovered.But special public clear 39-8818 communique (patent documentation 1) is just known the unreacted dialkyl benzene of minute quantity very early and is sneaked into solvent recovering system with the acetic acid as reaction solvent, is condensed into the overhead fraction that reclaims the dehydration distillation tower that acetic acid uses with the toluene of by-product etc. and separates, reclaims.
In addition, special public clear 62-41219 communique (patent documentation 2) and spy open flat 11-171820 communique (patent documentation 3) and also know aforementioned dehydration distillation tower refining, that the recovery acetate solvate is used, the Azotropic distillation method of the isobutyl acetate of use of employing entrainer and water formation azeotropic constituent, N-BUTYL ACETATE etc., unreacted dialkyl benzene is also sneaked in the overhead fraction with to this overhead fraction and is carried out stripping and separate the method for removing.
In addition, special table 2001-508024 communique (patent documentation 4), proposed by from the azeotropic zone of reclaiming the azeotropic distillation column that this acetic acid uses, extracting the hydrocarbon cut of p-Xylol etc., this cut is carried out stripping, separate hydrocarbons cut and entrainer, the entrainer that reclaims is recycled to the method in the azeotropic zone of aforementioned distillation tower, reclaims the entrainer of being carried secretly when removing dealkylation.
Secondly, Te Biaoping 10-504556 communique (patent documentation 5), proposed the raw material of the oxidizing reaction precursor substance (dialkyl benzene) that contains the p-Xylol of supplying with azeotropic distillation column etc. is imported azeotropic zone (position of the top of close azeotropic region lower limit), the method of taking out precursor substance near the position (this imports the field of position) this importing position, further, preferably import the zone of position at this raw material, also the method for taking out precursor substance from the position that imports the top, position promptly concerns the method for taking out as the reacting precursor material of hydrocarbon from the qualification position with base feed importing position.
In addition, the spy opens and has proposed from the highly different inlets more than 2 in the 2002-326001 communique (patent documentation 6) azeotropic distillation column base feed (distillation object), especially by extracting as middle runnings, mainly be the method for extracting the mixture of water and aromatic hydrocarbons (p-Xylol) composition from being positioned near the stage casing of this distillation tower below the high raw material supplying section of water concentration.
The scheme that extract in these stage casings is all the extracting position from the aromatic hydrocarbons (reacting precursor material) of azeotropic distillation column, as near the field the preferred azeotropic zone lower limit (entrainer concentration-0.1 weight %), particularly extract cut in the patent documentation 6 and be mainly the mixture that water and aromatic hydrocarbons are formed, near the some position of lower limit that preferably should the zone.Yet, present situation is: this lower limit region in this azeotropic distillation column is to form to change the most tangible zone of distilling period, small thermal distortion (variations of feed rate, heat supplied, quantity of reflux, quantity of distillate, down-off etc.) in the tower etc., the composition that extracts in the middle of the capital makes changes greatly, not only can not extract alkylbenzene, and even not distillate fully with stable concentration.
Therefore, distillate changes the extraction of confinement under the tangible azeotropic from this composition, and the composition that particularly contains alkylbenzene changes the separation balance in the Distallation systm is impacted, and has influence on the original fractionation performance of dehydration distillation tower.
In addition, adopting the different base feed of acetic acid content that reclaims from each position of making this technology of aromatic dicarboxylic acid to reclaim the dehydration distillation tower of component distillation of acetic acid, near the lower limit of azeotropic zone position base feed, perhaps, contain the alkylbenzene cut near the extraction of the position this lower limit, also have, containing position base feed (containing acetic acid water) above the cut extracting position etc. near this, these all strengthen distillation running in non-efficient to the extraction that contains the alkylbenzene cut.
[patent documentation 1] special public clear 39-8818 communique
[patent documentation 2] special public clear 62-41219 communique
[patent documentation 3] spy opens flat 11-171820 communique
[patent documentation 4] special table 2001-508024 communique
The flat 10-504556 communique of [patent documentation 5] special table
[patent documentation 6] spy opens the 2002-326001 communique
Summary of the invention
In the terephthalic acid of industrial operation and the manufacturing processed of m-phthalic acid, acetic acid recovery system as reaction solvent, not only from the phlegma of the heat recycle process of aforementioned oxidizing reaction, and the acetic acid fluid of being collected by numerous parts in the manufacturing process that contains all is transported to the acetic acid recovery system.Purpose is distillation processing or direct as the dehydration distillation tower in the raw material supplying recovery system, reclaims the acetic acid that dehydration reaches lower concentration (2-8wt%) as the effluent liquid at the bottom of the tower, distillates the branch discharge as cat head simultaneously and contains acetic acid 1000ppm or lower water.At this moment, in order to reduce the cost of erection of distillation tower, and suppress the distillatory energy consumption, developed recently uses the azeotropic distn of entrainer such as isobutyl acetate.
Accumulate in and contain the acetic acid fluid in the acetate solvate recovery system, be not only the part of the phlegma of the generation steam that flows out from reactor, and be the drainage water that is contained in the absorption tower (high-pressure absorber) that the composition that contains acetic acid etc. in this condensed waste gas absorbed by water, step-down-cooling through resultant of reaction, part from the phlegma of the effusive generation steams such as partial crystallization groove that make the crystallization slaking that generates aromatic dicarboxylic acid, the part of the reaction mother liquor from generate the crystallization slurry behind the separating aromatic dicarboxylic acid crystallizates is again from the effusive generation steam of the moisture eliminator of this separating aromatic dicarboxylic acid crystallizates, absorption from the eliminating oxygen of Crystallization Separation device and each storage tank etc. with the drainage water on the absorption tower (low pressure absorption tower) that contains acetate component in the waste gas in each operation such as sealed gas etc.Therefore, the acetic acid that contains in these fluids and the content of water differ widely respectively (acetic acid content: number wt%～90wt%), contain dialkyl benzene as the oxidizing reaction unreacted reactant simultaneously and be the alkylbenzene of main component and by-product methyl acetate etc.
In addition, because oxidizing reaction development of technology in recent years, the content of unreacted dialkyl benzene is respectively a small amount of, is several 100ppm to the maximum.And as the ritalin of by product according to the part that reclaims acetic acid difference, content is the scope of 0.1～1.5wt%.
As previously discussed, a large amount of water-containing acetic acid (or containing acetic acid water) of collecting from the each several part of aromatic dicarboxylic acid manufacturing process is dewatered, reclaim the azeotropic distillation column of acetic acid, compare with the capacity that reclaims acetic acid, the influx of the unreacted dialkyl benzene of p-Xylol etc. is a minute quantity, can not guarantee quantitative property to the feed rate of distillation tower and the hold-up in tower simultaneously.
Therefore, even as extract in the distillation tower stage casing of the high concentration of hydrocarbon extracted precursor substance (dialkyl benzene) cut of above-mentioned patent documentation 5 and patent documentation 6 propositions, also difficulty is stably extracted this concentration cut continuously, also must carry out the processing of stripping etc. to the hydrocarbon precursor substance that extract to reclaim, entrainer is carried out separating treatment.
This method, the inflow of alkylbenzenes such as dialkyl benzene is the unreacted reactant of oxidizing reaction, and is the progressively inflow slightly of a plurality of positions from above-mentioned inflow acetic acid, the assurance and the control that do not solve influx.Because from distillation tower, extract quantitatively, so can not realize that dialkyl benzene obtains break-even running in distillation tower.
In addition, in the above-mentioned motion, in order to improve the concentration ratio of aromatic hydrocarbons (alkylbenzene) and entrainer, though near the extraction the lower limit in component distillation territory as target, but the variation of the small dynamic in the azeotropic distillation column causes that all the position (column plate) of this time confinement is mobile, more is difficult to stable concentration and extracts alkylbenzene.
In addition, since with respect to the influx of alkylbenzene increase in the accumulation hold-up of each column plate of distillation tower (if alkylbenzene be high density bigger), balance (particularly becoming the situation of lower concentration) the estimation difficulty that needs could recover the destructive composition distillation tower in for a long time carries out the extraction of concentration stabilize.
Therefore, the method that the inventor reclaims unreacted dialkyl benzene, utilizes with stable concentration the evaporation of the acetic acid that adopts component distillation is studied the following method of having invented with great concentration with regard to the parsing in the distillation tower etc.
The present invention is with regard to the component distillation of acetic acid-water-isobutyl acetate, adopt the numerical evaluation of the system that imports p-Xylol consistently on a small quantity to carry out the simulation of multicomponent system distillatory, infer that this component distillation system p-Xylol in the distillation territory is concentrated to high density (about 70 weight %) with the reduction of entrainer concentration, in addition, utilize the minute differences of theoretical tray, nearly all become water, the concentration of p-Xylol reduces, and distillates p-Xylol hardly.
Therefore, as stablizing the preferred territory that takes out after this p-Xylol concentration that is concentrated, infer that temperature range is about 94 ℃～about 100 ℃ in the tower, and the scope of the concentration ratio of p-Xylol and entrainer is about 0.5～about 6, preferably about 1.0～about 4.
In addition, at this moment, the preferred entrainer that exists to a certain degree infers that the concentration of extracting the entrainer in the organic phase is about 15 weight % or higher, preferably about 20 weight % or higher.
According to these result, find the component distillation of acetate solvate recovery system in the aromatic dicarboxylic acid manufacturing process, not following confinement (entrainer concentration-0.1wt%) from the azeotropic zone, and directly do not extract the unreacted dialkyl benzene of p-Xylol etc. continuously, but the concentration ratio of waiting until unreacted dialkyl benzene and entrainer in azeotropic distillation column is trapped in the above-mentioned scope, and after confirming that this accumulates concentration ratio, still make the cut that accumulates that remains on this concentration ratio in this system by extracting off and on, can be used as high density, stable distillate reclaims dialkyl benzene.
Find that promptly unreacted dialkyl benzene is the cut that accumulates in the azeotropic field of azeotropic distillation column, do not extract this cut and remain to and accumulate the aimed concn ratio that enters in this territory, extract the method for this cut that accumulates off and on.
As mentioned above, the present invention makes in the acetate solvate recovery system of aromatic dicarboxylic acid, use isobutyl acetate to reclaim the method for unreacted dialkyl benzene as the azeotropic distillation column of entrainer during acetic acid dehydration, it is characterized in that, distillate in the azeotropic zone of this azeotropic distillation column the cut that 94～100 ℃ of temperature ranges contain alkylbenzene and be sent to the distillate storage tank, after isolating water from the bottom of this distillate storage tank, the limit is recycled in the aforementioned azeotropic zone organic phase cut on the top of distillate storage tank, the limit makes the organic phase cut accumulate in that the concentration ratio up to alkylbenzene and entrainer reaches target zone in the aforementioned azeotropic distillation column, carry out off and on from aforementioned distillate storage tank, extracting the intermittence that this organic phase cut that accumulates is discharged to system outside and extract, and with the dialkyl benzene of stable concentration recovery high density.
In addition, the present invention is characterized in that in aforementioned unreacted dialkyl benzene recovery method the target zone of the concentration ratio of aforesaid alkyl benzene and entrainer is about 0.5 weight ratio～about 6 weight ratios, preferably about 1.0 weight ratios～about 4 weight ratios.
In addition, the present invention is characterized in that in aforementioned unreacted dialkyl benzene recovery method the concentration of the aforementioned entrainer in the aforementioned organic phase cut that reclaims is about 15 weight % or higher off and on, preferably about 20 weight % or higher from aforementioned distillate storage tank.
In addition, the present invention is characterized in that in aforementioned unreacted dialkyl benzene recovery method, the limit makes aforementioned organic phase cut be recycled to aforementioned azeotropic zone, when the limit accumulates in the aforementioned azeotropic distillation column, confirms the concentration ratio of aforesaid alkyl benzene and entrainer.
In addition, the present invention is in the solvent acetic acid recovery system of making in the aromatic dicarboxylic acid, use isobutyl acetate to reclaim the method for unreacted dialkyl benzene as the azeotropic distillation column of entrainer during acetic acid dehydration, it is characterized in that distillating and contain the alkylbenzene cut and be sent to the distillate storage tank from the azeotropic zone of this azeotropic distillation column, after isolating water from the bottom of this distillate storage tank, the limit makes the organic phase cut on distillate storage tank top be recycled to that the limit accumulates in the aforementioned azeotropic distillation column organic phase cut in the aforementioned azeotropic zone, confirm the concentration ratio of alkylbenzene and entrainer in this organic phase cut that accumulates, the alkylbenzene that extracts this affirmation off and on from aforementioned distillate storage tank and the concentration ratio of entrainer are that the organic phase cut of about 0.5 weight ratio～about 6 weight ratios is discharged into the extraction at intermittence system outside, and with the dialkyl benzene of stable concentration recovery high density.
In addition, the present invention is characterized in that in aforementioned unreacted dialkyl benzene recovery method, and the alkylbenzene cut that contains that distillates 94～100 ℃ of temperature ranges in the aforementioned azeotropic zone is sent to aforementioned distillate storage tank and circulates.
In addition, the present invention is characterized in that in aforementioned unreacted dialkyl benzene recovery method the concentration of the aforementioned entrainer in the aforementioned organic phase cut that reclaims is about 15 weight % or higher off and on, preferably about 20 weight % or higher from aforementioned distillate storage tank.
In addition, the present invention is characterized in that in aforementioned unreacted dialkyl benzene recovery method, the dialkyl benzene cut that contains that will reclaim is used in the manufacturing aromatic dicarboxylic acid again from aforementioned distillate storage tank.
If adopt the present invention to reclaim off and on from the method for the effusive alkylbenzene in azeotropic zone of azeotropic distillation column with stable concentration, because the distillation characteristics in the distillation tower is not caused variation, go out the stability that moisture in the acetic acid and cat head distillate the acetic acid mixed volume in the water so improve tower bottom flow as the distillation purpose, and can stably reclaim the cut that suppresses the high density alkylbenzene that entrainer carries secretly.Become about 0.5 weight ratio～about 6 weight ratios if especially reclaim the alkylbenzene of cut and the concentration ratio of entrainer, then the acetic acid content that cat head is distillated in the water becomes lower concentration, suppresses the loss of acetic acid, the processing load of reduction draining.
And, can be in oxidizing reaction utilize the dialkyl benzene that reclaims again, reaction is not exerted an influence and helps to improve product yield.
In addition, the isobutyl acetate as entrainer that the present invention uses is because by sneaking into the effect that has in the oxidizing reaction as reaction promotor, so exist with stable amount even preferably sneak into also.Therefore, exist the utilizing again of recovery alkylbenzene of stable quantity isobutyl acetate that the influence of oxidizing reaction is stablized, can directly (not handle) again and utilize.
In addition,, also can carry out the separation, refining of distillation method etc. quantitatively, suppress sneaking into again of isobutyl acetate and utilize in order further to improve the concentration of dialkyl benzene.
More than, according to the present invention, making in the aromatic dicarboxylic acid can high density and stably extract the unreacted dialkyl benzene that concentrates in the solvent recuperation operation and reclaim, and can make to utilize in the dicarboxylic acid operation at this again and reclaim alkylbenzene.And, do not cause variation to forming in the distillation characteristics of azeotropic distillation column and the system, form stablely as the dehydration of the acetic acid of distillation target and make, can become low acetic acid content and discharge cat head and distillate water.
The simple declaration of accompanying drawing
Fig. 1 is in the component distillation of expression acetic acid-water of the present invention-isobutyl acetate, forms the figure that distributes in the distillation tower according to the multicomponent system distillatory analog result that imports p-Xylol system employing numerical evaluation consistently on a small quantity.
Fig. 2 is in the component distillation of expression acetic acid-water of the present invention-isobutyl acetate, according to the figure of composition in the distillation tower of multicomponent system distillatory analog result with the relation of the weight ratio of p-Xylol/isobutyl acetate.
Fig. 3 is in the component distillation of expression acetic acid-water of the present invention-isobutyl acetate, the figure that is inclined to according to the weight ratio of temperature and p-Xylol/isobutyl acetate in the distillation tower of multicomponent system distillatory analog result.
Fig. 4 is that the acetic acid dehydration of component distillation of the present invention and the schema that dialkyl benzene reclaims an embodiment of usefulness are adopted in expression.
Fig. 5 is the schema that an embodiment of the acetic acid dehydration of component distillation of the present invention and the operation that dialkyl benzene reclaims usefulness is adopted in expression.
Nomenclature
1 azeotropic distillation column
2 phlegma Receiving bins (two-phase divergence type)
3 distillate storage tanks (two-phase divergence type)
4,5 water coolers
11 raw material supplying pipelines
12 raw material supplying pipelines
13 raw material supplying pipelines
14 acetic acid recovery line
15 distillate water (water) vent line
16 backflow (organic phase) pipelines
17 backflow (water) pipelines
18 distillate circulation lines
19 distillate circulation lines
20 organic phase fetch pipeline
21 aqueous extraction pipelines
22 phlegma pipelines
23 control valves
24 controllers
25,28,30,32 valves
26 liquid level detectors
27 pumps
29,31,33 controllers
Embodiment
Utilize accompanying drawing that the recovery method of unreacted alkylbenzene and the embodiment of this system in the aromatic carboxylic acid manufacturing of the present invention are described.Moreover, the mimic condition is narrated later on.
Fig. 1 is in the component distillation of expression acetic acid-water of the present invention-isobutyl acetate, based on the figure of the composition distribution in the distillation tower of the multicomponent system distillatory analog result that imports p-Xylol system employing numerical evaluation consistently on a small quantity with the theoretical plate number relation of azeotropic distillation column.This Fig. 1 is that alkylbenzene (p-Xylol) accumulates in the temporary transient concentration map in the azeotropic distillation column, and the result that expression is accumulated gradually from the few concentration of alkylbenzene is expressed as the index that this accumulates degree to concentration ratio among Fig. 2.The azeotropic point of water and isobutyl acetate is water 16.5wt%, isobutyl acetate 83.5wt%, does not exist in the azeotropic zone of azeotropic distillation column 1 of alkylbenzene, estimates that all occasion water is that more than 10 wt%, isobutyl acetate are about 80wt%.Yet by there being alkylbenzene, water concentration reduces some, and water is about 5wt%, and alkylbenzene is about 70wt%, and the concentration of alkylbenzene almost is lowered into the relation of inverse ratio with the concentration of isobutyl acetate, almost be rendered as the relation of organic phase.
Fig. 2 is expression with distillation Simulation result of the present invention serves as to form in the distillation tower drawn of basis and figure that the theoretical plate number of the weight ratio of p-Xylol/isobutyl acetate and distillation tower concerns.This Fig. 2 amplifies theoretical plate number 20～44 column plates of distillation tower with scale, illustrates the ratio (wt%) of p-Xylol/isobutyl acetate (weight ratio) and water and isobutyl acetate.
Fig. 3 is expression with distillation Simulation result of the present invention is the figure that the theoretical plate number of the weight ratio tendency of temperature and p-Xylol/isobutyl acetate in the distillation tower drawn of basis and distillation tower concerns.This Fig. 3 uses scale to amplify theoretical plate number 20～44 column plates of distillation tower, illustrates temperature in p-Xylol/isobutyl acetate (weight ratio) and the azeotropic distillation column.
Fig. 4 is that the acetic acid dehydration of acetic acid-water of the present invention-acetic acid isobutyl vinegar component distillation and the schema that dialkyl benzene reclaims an embodiment of usefulness are adopted in expression.
But the unreacted dialkyl benzene running beginning during aromatic dicarboxylic acid is made is few in the acetic acid recovery process at first, and a lower concentration ground accumulates in azeotropic distillation column 1 system.Therefore use distillate circulation line 18 that the effusive distillate in component distillation intrasystem azeotropic zone is extracted in the distillate storage tank 3 of two-phase divergence type, use aqueous extraction pipeline 21 to discharge water phase separated from the bottom.And, use distillate circulation line 19 limits that the organic phase cuts in the distillate storage tank 3 are recycled in the above-mentioned component distillation system, the limit increases in the azeotropic distillation column 1 and the hold-up of the alkylbenzene cut in the distillate storage tank 3, the alkylbenzene in the use tester 40 mensuration distillate storage tanks 3 and the concentration ratio of entrainer, the target zone of the concentration ratio of this mensuration uses computer 24 constantly to control this circulation, make it as shown in Figures 2 and 3, reach about 0.5 weight ratio～about 6 weight ratios, preferred about 1.0 weight ratios～about 4 weight ratios.After the alkylbenzene in the distillate storage tank 3 and the concentration ratio of entrainer reach target zone, computer 24 is for example controlled control valve 23 and is stopped its circulation, after cutting off being connected of azeotropic distillation column 1 and distillate storage tank 3, for example open control valve 25 and extract distillate storage tank 3 interior organic phase cuts off and on from organic phase fetch pipeline 20 and reclaim.
In addition, extracting position apart from the azeotropic zone of azeotropic distillation column 1 is the zone (about the 31st block of column plate～41st block column plate of theoretical plate number) of 94～100 ℃ of temperature ranges of temperature in the tower shown in Figure 3, preferably distillation tower extracts column plate (position: for example the 34th block of column plate of theoretical plate number) and near position thereof from the distillate storage tank 3 of organic phase to the intrasystem circulation of component distillation, turns back to usually on the column plate that extracts column plate (for example the 35th block of column plate of theoretical plate number).In addition, owing to discharge to divide dried up 21 dissolving entrainers (isobutyl acetate) etc., so preferably similarly be recycled near the position of the interior extraction column plate of distillation tower with organic phase.Handle but also may be combined in the distillation tower base feed (for example 13).
In addition, in azeotropic distillation column 1 remains in operation, because the variation of the distillation characteristics of intrasystem balance destruction etc., even so continue in the circulation, also reduce sometimes alkylbenzene in distillation tower 1 and distillate storage tank 3 in concentration, even do not extract the organic phase cut in the distillate storage tank 3 this moment yet, and proceed from the circulation of the top organic phase of the discharge of the branch dried up 21 of the bottom of distillate storage tank 3 and distillate storage tank 3, use distillate circulation line 18,19 continue circulation, and (p-Xylol: PX) (isobutyl acetate: concentration ratio IBA) reaches about 0.5 weight ratio (the about 30wt% of the concentration of alkylbenzene) or higher, preferably reaches about 1.0 weight ratios (the about 50wt% of the concentration of alkylbenzene) or higher with entrainer up to alkylbenzene.
This is when adopting the water component distillation of isobutyl acetate, because alkylbenzene is trapped in the azeotropic zone of 94～100 ℃ of temperature, so adopt component distillation to reclaim in the dehydration tower 1 of acetate solvate during aromatic dicarboxylic acid is made, just realize distillating organic phase continue alkylbenzene that circulation forms accumulate with the azeotropic zone in composition stable.
In addition, analog result as shown in Figure 1 shows, even the azeotropic zone in the Distallation systm, because the high density of dialkyl benzene distillates the scope in zone and is restricted, in addition because the change in concentration of azeotropic zone lower limit side is rapid, historical facts or anecdotes is executed steady concentration is extracted the position that distillates that should be noted that in the distillation tower 1 down.Therefore the temperature in the preferred distillation tower 1 is 94～100 ℃, and to have to a certain degree entrainer, the concentration of extracting the entrainer (isobutyl acetate) in the organic phase be about 15 weight % or higher, about 20 weight % or higher preferably.So the alkylbenzene that adopts method of the present invention to reclaim stable high density is the concentration ratio of alkylbenzene and entrainer is about 0.5 weight ratio～about 6 weight ratios, be preferably the azeotropic zone of the scope of about 1.0 weight ratios～4 weight ratios.
In addition, find out by Fig. 2 and Fig. 3, the occasion of the alkylbenzene of the expression azeotropic zone upper limit and about 0.5 weight ratio of concentration ratio of entrainer, being PX/IBA than a side's of curve flex point (the 38th block of column plate of theoretical plate number and the 39th block column plate between), is the stable point that the cat head acetate concentration is reduced to 0.03wt% shown in the table 1 (embodiment 1) as described later.
In addition, even alkylbenzene concentration is spissated field, the concentration ratio of alkylbenzene and entrainer is also near the lower limit in the azeotropic zone that surpasses about 6 weight ratios (about the 32nd block of column plate of theoretical plate number), as described later shown in the table 4 (reference example), water concentration raises sharp, acetate concentration is also high is about 10wt%, owing to cause the phase stability in the distillation tower and the reduction of fractionation performance, distillate so be difficult to stable composition.Therefore, about 6 weight ratios of concentration ratio of the lower limit in azeotropic zone selection alkylbenzene and entrainer or lower, preferably about 4 weight ratios or lower, the about 15wt% of the concentration of entrainer or higher in the organic phase, preferably about 20wt% or higher field.
In addition, reach the intermittent recovery of the organic phase cut in the distillate storage tank 3 of setting concentration ratio of alkylbenzene and entrainer, must cut off being connected of distillation tower 1 and distillate storage tank 3, for example cut off the circulating fluid of control valve 23 controls, the change in concentration of the alkylbenzene in the azeotropic zone of inhibition distillation tower 1.And, start circulation time again and do not carry out rapid extraction, and preferably begin to circulate from predetermined internal circulating load or lower amount from the azeotropic zone.
In addition, because the dissolving water under the recovered temperature and divide dried up effusive the distillating in the cut in azeotropic zone that be blended into, owing to adopt cooling system 4 to cool off the naturally cooling that reaches in storage tank 3 in advance by distillating cut, distillate storage tank 3 divide dried up (about 10wt% or lower) to be trapped in the bottom, so but must form the two-phase separated structures of the clarification mode of separable water in the bottom.This form can be vertical, horizontal any, but must can guarantee to separate the capacity of the time of repose of water in the distillate.
Therefore, though the capacity of this organic phase depends on the influx of unreacted dialkyl benzene and the concentration of recovery etc., so long as it is just passable to store the capacity of about at least about the 3 days cut of alkylbenzene influx balance.In addition, the extraction of this water phase separated is in order to ensure the stable circulation of organic phase, preferred automatically or manually do not utilize the control of aqueous phase interface.
Then, high density of extracting and the stable organic phase cut that contains dialkyl benzene are not handled and directly sneak in the modulation oxidizing reaction raw material can cycling and reutilization, but as the above-mentioned mixing that preferably has continuous and quantitative regulate reactivity worth and the resultant of reaction that makes it not have influence on oxidizing reaction.
Below, to Fig. 1～shown in Figure 3, the component distillation mimic condition of implementing in the acetic acid dehydrating tower of the present invention etc. describes.
Adopt the acetic acid dehydrating tower simulation hypothesis of component distillation of the present invention to utilize p xylene oxidation to react the actual operation of producing terephthalic acid, from isobutyl acetate is the different multiple acetic acid raw material (11,12,13) of a plurality of positions importing water content of the dehydration distillation tower 1 of entrainer, carries out as the mode that the tower bottom flow fluid reclaims according to the acetic acid 14 that dewaters.Moreover trace is sneaked into p-Xylol and ritalin in the various raw material acetic acid at this moment.
The equilibrium system of additional each composition of this simulation, and water-isobutyl acetate (azeotropic point: 87.4 ℃, H
2O:16.5wt%), water-p-Xylol (azeotropic point: 92 ℃, H
2O:45.1wt%), water-ritalin (azeotropic point: 56.5 ℃, H
2O:3.5wt%), acetic acid-p-Xylol (azeotropic point: 115 ℃, acetic acid: azeotropic characteristic 72.0wt%), implement by the calculating in order of multicomponent system.
During simulation impose a condition and the result as follows.
Raw material supplying to dehydration distillation tower 1 is divided into three kinds of supplies, 100 weight parts/time, wherein, (1) H
2The raw material 11 of O concentration 21 weight % be 58 weight parts/time, (2) H
2The raw material 12 of O concentration 46 weight % be 35 weight parts/time, (3) H
2The raw material 13 of O concentration 87 weight % be 7 weight parts/time, reclaim H
2Acetic acid 68 weight parts of O concentration 5 weight %/time as tower bottom flow fluid 14.In addition, the condensation overhead vapours is carried out two and is separated in phlegma Receiving bin 2, from distillate water discharge pipe line 15 discharge water 32 weight parts that contain acetate concentration 0.3 weight %/time.In addition, contain p-Xylol 170 ppm by weight in the base feed 11 consistently, ritalin 0.07 weight %, contain p-Xylol 230 ppm by weight in the base feed 12 consistently, ritalin 1.2 weight %, contain p-Xylol 70 ppm by weight in the base feed 13 consistently, distillation tower is supplied with the position of column plate, according to being equivalent to the water concentration same concentrations column plate feed of Ta Nei and various base feeds, the isobutyl acetate of overhead condensation liquid Receiving bin 2 be the organic phase 16 of main component 200 weight parts/time and 12 weight parts of water 17/time be back to the cat head of distillation tower 1 setting determine.
The result, during 45 blocks of column plates of the theoretical plate number of azeotropic distillation column 1, in 0.35 weight part/time ratio distillate from the 33rd block of column plate of theoretical plate number that accumulates p-Xylol concentration, 0.026 weight part/time take out be discharged to outside the system after, by remaining the 34th column plate place of theoretical plate number that be recycled to, can make p-Xylol be concentrated to about 70wt%, simultaneously, infer that the composition of calculating as shown in Figure 1 distributes.Moreover, do not illustrate the composition of ritalin.
Based on these result, form in the distillation tower of expression in the distillation tower and the weight ratio relation of p-Xylol/isobutyl acetate be Fig. 2, the p-Xylol/isobutyl acetate weight in the expression distillation tower when in the tower temperature be Fig. 3.
Therefore, sneak into the p-Xylol of trace in the dehydration tower of acetic acid employing component distillation, estimation can be accumulated the high density of the about 70 weight % of p-Xylol in distillation tower 1.And, estimate that the concentration ratio of p-Xylol and isobutyl acetate is 0.5 weight or higher, being preferably 1.0 weight or higher temperature range is 94～100 ℃.
But will be stably take out p-Xylol, even the said temperature scope from distillating the stability of composition, estimates to contain at least in the organic phase isobutyl acetate 15 weight % or higher as entrainer, preferred about 20 weight % or higher from the dehydration tower 1 of reality.
Below, adopt Fig. 4 and Fig. 5 that the recovery method of unreacted alkylbenzene in the aromatic carboxylic acid manufacturing of the present invention and the embodiment that has of this system are described.
Embodiment 1
In the acetic acid recovery system in the terephthalic acid manufacturing process, use the azeotropic distillation column 1 of column plate type (80 blocks of column plates of number of actual plates), adopt and use isobutyl acetate to dewater as the azeotropic distn Dichlorodiphenyl Acetate of entrainer, the process step that adopts Fig. 4 to represent reclaims acetic acid, extracts the cut that contains p-Xylol and reclaims.Fig. 5 represents the operating process in the acetic acid recovery system of the present invention.
It is by making the about 20 weight % of water concentration, the about 46 weight % that terephthalic acid is collected supposition that charging constitutes, and the acetic acid recovery line 11,12,13 of about 88 weight %, be connected with the 7th block of column plate of number of actual plates (the 4th block of column plate of theoretical plate number), the 15th block of column plate of number of actual plates (the 9th block of column plate of theoretical plate number) and the 36th block of column plate of number of actual plates (the 22nd block of column plate of theoretical plate number) at the bottom of the tower of distance distillation tower 1 respectively, carry out feed.Then, entry into service (S51), begin to extract steam (S52) from cat head.The overhead vapours of this extraction is after water cooler 5 coolings, the phlegma that the liquid pipeline 22 that is condensed is carried is separated in phlegma Receiving bin (two-phase divergence type groove) 2, entrainer (isobutyl acetate) is that the organic phase of main component is through refluxing (organic phase) pipeline 16, controller 29 by-pass valve controls 28, flow by about 20000kg/hr makes down the water of phase through (water) pipeline 17 that refluxes, controller 31 by-pass valve controls 30 are back to cat head by the flow of about 1200kg/hr.In addition, through the acetic acid of acetic acid recovery line 14 in the ratio of about 5700kg/hr recycle-water concentration 5～8 weight % at the bottom of the tower of distillation tower 1, make aqueous portion in the overhead condensation liquid Receiving bin 2 through distillating water (water) vent line 15 simultaneously, control part 33 by-pass valve controls 32 turn round in the ratio discharge of about 3000kg/hr.
The water of result through distillating water (water) vent line 15 and discharging from the bottom of phlegma receiver 2 contains acetic acid 0.03 weight % or lower, isobutyl acetate 0.4～1 weight %, ritalin 1～3 weight %, and p-Xylol is 0.1 weight % or lower.Therefore, water is imported simple and easy distillation tower (do not have diagram), heat up in a steamer isobutyl acetate, ritalin respectively individually, remove and contain organic water and discharge after as liquid waste disposal.And utilize again from the phlegma Receiving bin 2 that the isobutyl acetate that above-mentioned simple and easy distillation tower reclaims is recycled to above-mentioned overhead vapours.
In addition, the azeotropic zone from the 57th block of column plate of number of actual plates (being equivalent to the 34th block of column plate of theoretical plate number) of 96～98 ℃ of the temperature of expression distillation tower 1 is extracted into distillate storage tank 3 (S53) to distillate.That is, adopt the distillate (liquid phase portion) that distillates the 57th block of column plate of number of actual plates in the ratio of about 15kg/hr, be cooled to about 50 ℃ by water cooler 4 after, the about 1.5m of importing content amount
3(overflow organic phase capacity 0.7m
3But) in the isolating horizontal distillate storage tank 3 of two-phase after, use pump 27 that the method that overflow organic phase cut is back to the 58th block of column plate of number of actual plates (about the 35th block of column plate of theoretical plate number) of distillation tower 1 is carried out (S55) by the tank level control of liquid level detector 26.Use tester 40 limits to measure the concentration ratio of the hydrocarbon concentration that contains p-Xylol (p-Xylol content 95wt% or higher alkylbenzene concentration: claim PX concentration) and the concentration (concentration of isobutyl acetate: claim IBA concentration) of entrainer in this overflow organic phase cut, for example controller 24 is controlled like that by following, promptly, proceed to utilize the distillate circulation line 18 of distillation tower 1 (the 57th block of column plate of number of actual plates)-storage tank 3-distillation tower 1 (the 58th block of column plate of number of actual plates), 19 circulation, (PX concentration is about 36wt% to reach about 0.6 weight ratio up to this concentration ratio, IBA concentration is equivalent to about 60wt%).As shown in table 1, surpass 36wt% from entry into service PX concentration the 17th day the time, the concentration ratio of PX/IBA surpasses about 0.6, so controller 24 is for example controlled by-pass valve control 23 and is cut off the circulation discrepancy that (stopping) leading to above-mentioned distillate storage tank 3, carrying out organic phase by the distillate organic phase cut in 25 pairs of storage tanks that accumulated of by-pass valve control 3 extracts, discharge off and on from pipeline 20, be recovered in as high PX concentration solution and reclaim in the liquid Receiving bin (not having diagram).In addition, in above-mentioned continuation circulation, be extracted in the isolating water 21 in separator tank bottom of storage tank 3, in time discharge, be blended in the raw material 13 of the 36th block of column plate of number of actual plates of supplying with distillation tower 1 (S54).
In addition, control according to controller 24, after the organic phase content of distillate storage tank 3 is discharged, in the ratio of about 10kg/hr begin to the importing of above-mentioned same distillate storage tank 3, begin circulation when the overflow organic phase of distillate storage tank 3 reaches again after setting liquid level, circulate according to the ratio of about 15kg/hr.Then, controller 24 waits for that accumulating the back alkylbenzene reaches high density (3～5 days) (S56) again, utilize tester 40 to carry out the mensuration (S57) of the concentration ratio of the PX/IBA at least in the distillate storage tank 3, the target of confirming concentration ratio was above about 0.6 o'clock, by-pass valve control 23 carries out round-robin and cuts off (stopping), to the reclaimer operation (S59) of distillate organic phase, by-pass valve control 25 as above-mentioned ground carry out off and on repeatedly.
The result, as shown in table 1 from entry into service after the 17th day, cut off circulation in per 3～5 days to distillate storage tank 3, if carry out the recovery of content off and on, confirm that then alkylbenzene is a high density (PX concentration: 35.45～37.5wt%), and can reclaim stable organic phase with the concentration ratio (PX/IBA=0.57～0.62 weight) of entrainer.
In addition, the p-Xylol liquid that contains that reclaims from distillate storage tank 3 is delivered to recovery liquid Receiving bin (not having diagram), ratio in 10kg/hr or lower (the about 0.5wt% of raw material p-Xylol or lower), have quantitative property ground with low uncertaintyly and directly import to the oxidizing reaction raw material regulating tank of terephthalic acid manufacturing process, supply with the utilization again of oxidizing reaction from this recovery liquid Receiving bin.
The acetic acid content that this moment, the separation through distillating water (water) vent line 15 and discharging from overhead condensation liquid Receiving bin 2 distillated the water is shown in the following table 1.Find out that by this result the acetic acid that the intermittently extracted cat head that contains alkylbenzene liquid distillates in the water is low levels (0.04wt% or lower) and stable.
Table 1 embodiment 1
Embodiment 2
Further proceed the running of the distillation tower of embodiment 1, simultaneously after the 50th day discharge content of embodiment 1, controller 24 starts circulation again, owing to not interrupting accumulating the hydrocarbon that contains p-Xylol so proceed distillation tower 1 (the 57th block of column plate of number of actual plates)-storage tank 3-: the circulation of distillation tower 1 (the 58th block of column plate of number of actual plates).Be concentrated to 55.91wt% from beginning to circulate in the 11st day PX concentration again, the concentration ratio of PX/IBA increases to 1.33.Moreover the temperature of the 57th block of column plate of number of actual plates of the distillation tower 1 of this moment is 98.6 ℃.
Then, controller 24 is controlled and is interrupted above-mentioned circulation similarly to Example 1, carries out the recovery of the distillate organic phase in the distillate storage tank 3.In addition, again similarly to Example 1, controller 24 starts circulation again, the affirmation aimed concn that makes PX concentration is that the affirmation target of the concentration ratio of about 56wt%, PX/IBA is about 1.33, circulate off and on similarly to Example 1 and interrupt, carry out repeatedly reclaiming the distillate organic phases from distillate storage tank 3.The recovery of content was carried out in cycling through of the distillate storage tank 3 that the result is as shown in table 2 in per 5 days～7 days, can make the hydrocarbon that contains p-Xylol with high density (55.67～56.98wt%), and reclaim afterwards at stable ratio (PX/IBA=1.30～1.37) with entrainer.Moreover the temperature of the 57th block of column plate of distillation tower therebetween is 97～99 ℃.
In addition, after the distillate that the 46th day reclaims in the storage tank 3, the circulation of starting distillation tower 1 (the 57th block of column plate of number of actual plates)-storage tank 3-distillation tower 1 (the 58th block of column plate of number of actual plates) again, it is 70wt% that continuation circulation according to target makes the PX concentration in the storage tank 3, the concentration ratio of PX/IBA is 2.5.As a result, (after the recirculation the 9th day) PX concentration was concentrated to 71.02wt% in the 55th day.
Similarly interrupt circulation with above-mentioned, reclaim the overhead product in the storage tank 3 after, start circulation more again after, be 70wt% with PX concentration, the concentration ratio 2.5 of PX/IBA circulates off and on as target and interrupts, and carries out the recovery of overhead product in the storage tank off and on repeatedly.As a result, shown in following table 2, can make hydrocarbon simmer down to 70.92wt%, the 71.32wt% that contains p-Xylol, and reclaim overhead product with the stable back of the ratio (PX/IBA=about 2.6) of entrainer every 7,8 days.Moreover the temperature of the 57th block of column plate of number of actual plates of the distillation tower 1 of this moment is 96-98 ℃.
In addition, the liquid that contains p-Xylol that reclaims from distillate storage tank 3 is delivered to this each liquid Receiving bin (not having diagram) that reclaims, by 6kg/hr or lower rate variable is few and have quantitative property ground directly to import to the oxidizing reaction raw material regulating tank (not having diagram) of terephthalic acid manufacturing process, supply with again and utilize.
In addition, similarly to Example 1, cat head distillated in the water 15 acetic acid content and be shown in the following table 2, be confirmed to be low levels and stable.
Table 2 embodiment 2
As mentioned above, adopt the embodiment of alkylbenzene absorption method of the present invention, can not disarray the intrasystem distillation characteristics of azeotropic distillation column, in addition, variation at distillation characteristics, also can wait for the high density accumulation of alkylbenzene in the distillate storage tank,, can stably take out the high density cut of alkylbenzene by reclaiming the organic phase cut off and on.
Promptly, even there is the period that does not distillate alkylbenzene according to the variation of the distillation characteristics of Distallation systm or minimizing of semi-invariant etc., but continue circulation confirms to be detained high density in the organic phase cut of distillate storage tank alkylbenzene, by reclaiming the organic phase cut off and on, can make to high density the concentration stabilization that reclaims the organic phase cut.
In addition, the embodiment that adopts alkylbenzene absorption method of the present invention as can be known, at isobutyl acetate is in the component distillation of entrainer, the so-called stable zone that distillates the high density alkylbenzene, the concentration ratio of preferably pressing alkylbenzene and entrainer is at 0.5 weight ratio or higher (the about 30wt% of alkylbenzene concentration or higher), about 6 weight ratios or lowlyer extract off and on, this temperature range is equivalent to 94～100 ℃.
In addition, absorption method according to alkylbenzene of the present invention, do not limit raw material supplying position to azeotropic distillation column, the method that can adopt common supply to be equivalent to the concentration raw material of the position of distillation concentration in the component distillation system is carried out, and, by the concentration of alkylbenzene in the stable system, the acetic acid content that the discovery cat head distillates in the water (bottom of overhead condensation liquid is divided dried up) is also stable.In addition, if the recovery concentration stabilize of this alkylbenzene at high density (about 30 weight % or higher), the tendency of further raising fractionation performance is then arranged, reducing acetic acid content also is accessory effect.
This estimation is by intermittently extracting the organic phase cut, keep the alkylbenzene concentration in the Distallation systm, can suppress intrasystem composition and change, stablizing the cause of the original fractionation performance of distillation tower.
In addition, contain 95wt% or higher unreacted dialkyl benzene in the isolating alkylbenzene of the solvent recovering system from the aromatic dicarboxylic acid manufacturing, other composition is the by product that takes off alkyl of toluene etc.
Therefore, during aromatic dicarboxylic acid is made in the recovery system of solvent acetic acid, will from adopt isobutyl acetate be entrainer component distillation the dehydration tower middle and high concentration and stably extract the unreacted dialkyl benzene, then must distillate and contain the alkylbenzene cut and temporarily exist the storage tank from this dehydration and azeotropic zone, after removing water phase separated, not only organic phase is recycled to this zone but also confirms that alkylbenzene concentration reaches more than the aimed concn, extracts off and on.And should confirm that aimed concn was by about 0.5 weight of concentration ratio or higher (the about 30 weight % or higher of alkylbenzene concentration) with alkylbenzene and entrainer (isobutyl acetate), preferred about 1.0 weight or higher (the about 50 weight % or higher of alkylbenzene concentration) as target, can more stably extract.
In addition, when the concentration ratio that alkylbenzene and entrainer be described surpasses about 6 weight ratios, the organic phase cut in the distillate few (the water ratio is many), and also the acetic acid content increase in the organic phase etc. becomes reclaimer operation and forms unsettled principal element with recovery liquid.
Comparative example
Comparative example is in azeotropic distillation column similarly to Example 1, the 57th block of column plate from distillation tower 1 do not extract, but after the cut sample of the 57th block of column plate by taking out distillation tower 1 confirms that PX concentration reaches about 36wt%, ratio in 6kg/hr is cooled off and extraction continuously quantitatively from the 57th block of column plate, accumulates in distillate storage tank and the mode that reclaims in the liquid Receiving bin.After confirming PX concentration like this, extract from the 57th block of column plate simply continuously, materials (before importing above-mentioned storage tank) after extracting the cut cooling in per 4 days during this, measure the result of the composition of organic phase part, for following table 3 expression up to 36 days composition.
Then, press 15kg/hr, 8kg/hr, 4kg/hr changes extraction rate, measure the per 4 days organic phase of above-mentioned same extraction cut and form.Measurement result is shown in after 40 days of following table 3.Temperature of the 57th block of column plate of distillation tower is 95～98 ℃ during this.
These result illustrates when extracting continuously from as a comparative example azeotropic distillation column is simple, and the composition that extracts the organic phase of cut changes greatly, unstable.And, though illustrate that the acetic acid content of the branch of overhead condensation liquid in dried up is about 0.7wt% or lower lower concentration, unstable.
In addition, the distillate that is extracted into continuously in the storage tank does not quantitatively circulate respectively, after temporarily being trapped in storage tank and reclaiming in the liquid Receiving bin, because the concentration instability of alkylbenzene, handles so be mixed into after this off-test in the base feed of azeotropic distillation column.
Table 3 comparative example 1
Reference example
Reference example is the situation of the test portion of the 54th block of column plate of number of actual plates (about the 32nd block of column plate of theoretical plate number) cut of getting distillation tower in embodiment 2, the ratio of the organic phase of the cut test portion cooling back (about 30 ℃) of this taking-up and the compositional analysis of this test portion be the results are shown in table 4.Moreover the temperature of the 54th block of column plate around here is 98～102 ℃.
The days of operation of materialsing was taken a sample from the beginning in the 8th day of embodiment 2 in per 4 days.The 54th sample water ratio height that column plate is got, the sampling amount instability of organic phase also has when can not get organic phase fully simultaneously.Though and get the PX concentration height of organic phase but acetate concentration also high (concentration 5wt% or higher in the organic phase), the operation after distillating must be noted that (corrodibility).
Table 4 reference example
Claims (5)
1. the recovery method of unreacted alkylbenzene in the manufacturing aromatic dicarboxylic acid, it is characterized in that, be in the recovery system of solvent acetic acid in making aromatic dicarboxylic acid, use isobutyl acetate to reclaim the method for unreacted dialkyl benzene as the azeotropic distillation column of entrainer during acetic acid dehydration, wherein, distillate from the azeotropic zone of this azeotropic distillation column and to contain the alkylbenzene cut and be sent to the distillate storage tank, after isolating water from the bottom of this distillate storage tank, the limit is recycled in the aforementioned azeotropic zone organic phase cut on distillate storage tank top, the limit accumulates in the aforementioned azeotropic distillation column organic phase cut, carry out the affirmation of the concentration ratio of alkylbenzene and entrainer in this organic phase cut that accumulates, reclaim the alkylbenzene of this affirmation from aforementioned distillate storage tank discontinuous ground and the concentration ratio of entrainer is the organic phase cut of 0.5 weight ratio～6 weight ratios.
2. the recovery method of unreacted alkylbenzene in the described manufacturing aromatic dicarboxylic acid of claim 1, it is characterized in that, the cut that contains alkylbenzene that distillates 94～100 ℃ of temperature ranges in the azeotropic zone of aforementioned azeotropic distillation column is sent to aforementioned distillate storage tank, circulates.
3. the recovery method of unreacted alkylbenzene in claim 1 or the 2 described manufacturing aromatic dicarboxylic acids is characterized in that the concentration of the aforementioned entrainer in the aforementioned organic phase cut that reclaims is 15 weight % or higher off and on from aforementioned distillate storage tank.
4. the recovery method of unreacted alkylbenzene in claim 1 or the 2 described manufacturing aromatic dicarboxylic acids is characterized in that, utilizes the cut that contains dialkyl benzene that reclaims again in making aromatic dicarboxylic acid from aforementioned distillate storage tank.
5. the recovery method of unreacted alkylbenzene in the described manufacturing aromatic dicarboxylic acid of claim 3 is characterized in that, utilizes the cut that contains dialkyl benzene that reclaims again in making aromatic dicarboxylic acid from aforementioned distillate storage tank.
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