CN1169421A - Method for separation of crude ester in dimethyl terepthalate - Google Patents
Method for separation of crude ester in dimethyl terepthalate Download PDFInfo
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- CN1169421A CN1169421A CN 97101064 CN97101064A CN1169421A CN 1169421 A CN1169421 A CN 1169421A CN 97101064 CN97101064 CN 97101064 CN 97101064 A CN97101064 A CN 97101064A CN 1169421 A CN1169421 A CN 1169421A
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Abstract
The present invention relates to a method for separation of crude ester in dimethyl terepthalate, the main process for preparing crude ester comprises oxidizing para-xylene (p-x) and methyl para-toluate (p-TE), esterifying the oxidized mixture from DMT preparing process with methanol, obtaining rich p-TE fraction and high-boil remains fraction, the crude ester separation is in a separation unit equipped with a separation wall tower, or a distillation tower having front tower, or a distillation tower having rear tower. Furthermore, the invention also relates to a process preparing DMT, wherein the crude ester separation is in a separation unit equipped with a separation wall tower, or a distillation tower having front tower, or a distillation tower having rear tower.
Description
The present invention relates to a kind of separation method of so-called thick ester, the process of mainly producing of this thick ester is, the catalyzed oxidation of p-Xylol (p-X) and methyl p toluate (p-TE), to carrying out esterification with methyl alcohol, become rich p-TE cut, thick DMT cut and high boiling point residual fraction subsequently from the reaction product in the oxidation step of the preparation process of dimethyl terephthalate (DMT) (DMT); Also relate to the relevant therewith method for preparing dimethyl terephthalate (DMT) (DMT).
Known present Witten (prestige is stepped on) DMT method mainly comprises following process steps:
The oxidation of-p-Xylol (p-X) and methyl p toluate (p-TE) comprises also that usually downstream exhaust gas purifies,
-carry out esterification to coming autoxidizable reaction product with methyl alcohol,
-so-called thick the ester (thick DMT) that will generate is separated into a kind of rich p-TE cut, traditionally it is circulated to oxidation, a kind of thick DMT cut, it contains the above DMT of 85wt% usually, and a kind of high boiling point residual fraction, if it is carried out suitable comprehensive treating process, for example carry out downstream methyl alcohol alcoholysis or pyrolysis, then also comprise catalyst recovery subsequently
-thick DMT cut is purified, for example wash, recrystallization and distillation, (see＜dimethyl terephthalate (DMT), Ullmann, the 22nd volume, the 4th edition, 529～533 pages; EP 0 464 046B1; DE-OS 40 26 733).By DMT,, can also prepare the terephthalic acid of suitable grade by specific hydrolysis promptly by cut that is rich in DMT especially or high purity DMT.
The oxidation of the mixture of p-Xylol (p-X) and methyl p toluate (p-TE or pT ester) normally utilizes the oxygen in the atmosphere, finishes in the presence of the heavy metal catalyst in liquid phase (DE-PS 20 10 137), under the absolute pressure condition of about 140 ℃～180 ℃ temperature and about 4～8 crust.The reaction mixture that this oxidation stage generates mainly contains terephthalic acid monomethyl ester (MMT), paratolunitrile (p-TA) and terephthalic acid (TA), they or be dissolved or suspended among the p-TE, then, depress extremely and carry out esterification in about 250 ℃～280 ℃ temperature and 20～25 crust with methyl alcohol.At separating unit, below also claim in the distillation of thick ester that the thick ester of generation is separated into p-TE cut, thick DMT cut and high boiling point by distillment and contains the catalyst residue cut.The p-TE cut turns back to oxidation, and thick DMT cut is converted into the product of required quality by purification phase subsequently.Derive from thick ester distillatory residual fraction and can stand methyl alcohol alcoholysis or pyrolysis, the valuable product that generates in this process is circulated in the process and goes.
In the Witten-DMT method, the flashing chamber system is adopted in thick ester distillation traditionally, referring to Fig. 1 and 2 Tower Systems, referring to Fig. 2, carries out.3 Tower Systems (DE-OS 30 11 858) were also disclosed.Yet in this type systematic, disadvantage is that except rich p-TE cut, thick DMT cut also must steam through cat head, thereby causes higher energy expenditure.And in the system that mentions in the above, because the overstand at the bottom of tower impels to generate a great deal of undesirable by product, the generation of this by product greatly reduces productive rate.Moreover flashing chamber system and 2 towers or 3 Tower Systems also are the important factors of costs such as DMT plant construction, running and maintenance.
Therefore, the purpose of this invention is to provide a kind of method of separating thick ester from DMT technology, it can reduce the energy expenditure of process, thereby also can further increase economic efficiency.
The purpose that is proposed reaches according to the disclosed content of claims of the present invention.
Have now found that, if thick ester is separated in a kind of distillation tower that is provided with partition wall that comprises, for easy meter also is called dividing wall column, perhaps comprise the distillation tower of tower before a kind of having or have in the separating unit of distillation tower of back tower and carry out that then DMT technology can obtain sizable saving on energy expenditure.
Comprise the Tower System of the distillation tower that is provided with partition wall and comprise the tower of additional stand-by still, its principle is known, and its general mode of operation can be referring to: ENC (＜European chemical news 〉) 2～8, October, (1995), p.26, " the energy-conservation situation of BASF AG aspect distillation "; Chem.Eng.Res.Des. (research of＜chemical engineering and design 〉), (1993) 71 (3), p.307, " control of dividing wall column "; United States Patent (USP) 2,471,134; Chem.Eng.Res.Des., volume A: the Institute of Chemical Engineers proceedings, September (1993) pp.639～644, " by the heat transfer of partition wall "; Chem.Eng.Res.Des., volume A: the Institute of Chemical Engineers proceedings, March (1992) pp.118～132, " design and optimization of full thermocouple connection distillation tower ".
The special superiority of the inventive method is mainly derived from such fact: thick DMT cut can take out from side line, and no longer needs through cat head.As a result, compare, can obtain sizable energy saving, do not change the otherwise quality of thick DMT simultaneously with known thick ester distillating method.And the residence time of valuable product at the bottom of thermal tower shortens, and this point is to realize by product is under the comparatively gentle condition, thereby has reduced the generation that productive rate is had the useless by product of negative impact.
Therefore, the present invention relates to a kind of separation method of so-called thick ester, the main process that this thick ester generates is: the catalyzed oxidation of p-Xylol (p-X) and methyl p toluate (p-TE), subsequently to carrying out esterification with methyl alcohol from the reaction product in the oxidation step of the preparation process of dimethyl terephthalate (DMT) (DMT), become and be rich in the p-TE cut, thick DMT cut and high boiling point residual fraction, this method is included in the lock out operation that carries out this thick ester in a kind of separating unit, this unit comprises a kind of dividing wall column, the distillation tower of tower before perhaps a kind of comprising, perhaps a kind of distillation tower that comprises the back tower.
In the method for the invention, the separation of thick ester is normally at 100～280 ℃, preferably carries out under the absolute pressure of 130～260 ℃ temperature and 50～500 millibars (mbar).
In order to make separating unit of the present invention reach good especially separation efficiency, the pressure that reduces simultaneously total system as far as possible falls, preferably, can be at this dividing wall column or the distillation tower of tower or back tower before comprising, and/or among preceding tower or back tower, so-called structure bag is set.
Preferably, in the method for the invention, thick being separated in a kind of single Tower System of ester carried out; Comprise also that wherein those have suitably equipped the separating unit of the distillation tower with the additional preceding tower that connects or back tower.
Fig. 3 represents to be used for the slightly skeleton diagram of a preferred embodiment of the isolating separating unit of the present invention of ester of DMT technology, and its structure is a kind of dividing wall column that side line is extracted out that has.Favourable way is that thick ester is at first joined in the corresponding dividing wall column through the partition wall side line.From the top of dividing wall column, will extract out than the easier ebullient p-TE of DMT cut, and be circulated to oxidation.Advantageously, the separation wall energy in the dividing wall column prevents that high boiling component and heavy metal catalyst in the residual fraction from entering into thick DMT cut.This thick DMT cut is normally extracted out through side line and is left this dividing wall column, and it extracts the height place of optimum seeking site at partition wall out.The high boiling point residual fraction shifts out from the bottom of dividing wall column usually.
According to the present invention, upstream or downstream at distillation tower suitably connect a kind of stand-by still, tower or back tower before also can being called can prevent that equally component in the residual fraction above-mentioned from going among entering into the thick DMT cut that thick ester separates, referring to the accompanying drawing 4 and 5 of this paper.
Fig. 4 represents that another is used for the skeleton diagram of the preferred embodiment of the thick isolating separating unit of the present invention of ester of DMT technology, and its structure comprises a distillation tower and the additional preceding tower that is connected with thick DMT cut side line extraction.Advantageously, thick ester is at first joined in this preceding tower through side line go.
Fig. 5 represents that another is used for the skeleton diagram of the preferred embodiment of the thick isolating separating unit of the present invention of ester of DMT technology, and it is configured to comprise an additional distillation tower that connects the back tower, extracts out comprising a thick DMT cut side line.
Usually, the thick DMT cut that goes out from thick ester separation of produced will further be processed.Preferably, produce the dimethyl terephthalate (DMT) of higher degree at last, for example high purity DMT, and the terephthalic acid (TA) of producing respective quality, the hydrolysis of the DMT that for example PTA or PTA-p, the latter can be by the respective quality grades obtains easily.As for the further processing of this thick DMT cut, can carry out in the program of describing at the very start according to this paper.
Therefore, the invention still further relates to the preparation method of a kind of dimethyl terephthalate (DMT) (DMT), it mainly comprises following process steps,
The oxidation of-p-Xylol (p-x) and methyl p toluate (p-TE),
-will be from the reaction product methanol esterification of above-mentioned oxidation,
-so-called thick the ester that will generate is separated into rich p-TE cut, thick DMT cut and high boiling point residual fraction,
The purification of-thick DMT cut,
Desired as at least one item in claim 1～6, this process is included in carries out thick ester separation in a kind of separating unit, and described unit is equipped with a kind of dividing wall column or a kind of distillation tower that comprises preceding tower, perhaps a kind of distillation tower that comprises the back tower.
Being also advantageous in that of method of the present invention is starkly lower than suitable legacy system usually according to the capital investment of separating unit of the present invention.
Accompanying drawing 1 explanation
Fig. 1 represents to be known as thick ester distillatory skeleton diagram in the DMT technology of flashing chamber system:
-material stream-
1 thick ester from esterification
2 high boiling points that are sent to comprehensive treating process, contain the residual fraction of catalyzer
3 are sent to the p-TE cut cycling stream of oxidation
4 are sent to the thick DMT of further purification
-device composition-
5 flashing chambers
6 thick ester distillation towers
2 explanations of-accompanying drawing-
Fig. 2 represents to be known as thick ester distillatory skeleton diagram in the DMT technology of two Tower Systems:
-material stream-
1 thick ester from esterification
2 are sent to the p-TE cut cycling stream of oxidation
3 are sent to the thick DMT of further purification
4 high boiling points that are sent to comprehensive treating process, contain the residual fraction of catalyzer
-device composition-
5 p-TE distillation towers
6 thick DMT distillation towers
Accompanying drawing 3 explanations
Fig. 3 represents to be used for a kind of preferred embodiment skeleton diagram of the thick isolating separating unit of the present invention of ester of DMT technology, and its structure is the partition wall distillation tower that a band side line is extracted out:
-material stream-
1 thick ester from esterification
2 high boiling points that are sent to comprehensive treating process, contain the residual fraction of catalyzer
The 3 thick DMT cut side lines that are sent to further purification are extracted stream out
4 are sent to the p-TE cut cycling stream of oxidation
-device composition-
5 partition wall distillation towers
Accompanying drawing 4 explanations
Fig. 4 represents to be used for a kind of preferred embodiment skeleton diagram of the thick isolating separating unit of the present invention of ester of DMT technology, and its structure is the distillation tower and an additional preceding tower that is connected that a band side line is extracted out:
-material stream-
1 thick ester from esterification
2 high boiling points that are sent to comprehensive treating process, contain the residual fraction of catalyzer
The 3 thick DMT cut side lines that are sent to further purification are extracted stream out
4 are sent to the p-TE cut cycling stream of oxidation
-device composition-
5 thick ester distillation towers
Tower before 6
Accompanying drawing 5 explanations
Fig. 5 represents to be used for a kind of preferred embodiment skeleton diagram of the thick isolating separating unit of the present invention of ester of DMT technology, and its structure is the additional back tower that is connected of a distillation tower and a band side line extraction:
-material stream-
1 thick ester from esterification
2 high boiling points that are sent to comprehensive treating process, contain the residual fraction of catalyzer
The 3 thick DMT cut side lines that are sent to further purification are extracted stream out
4 are sent to the p-TE cut cycling stream of oxidation
-device composition-
5 thick ester distillation towers
6 back towers
The abbreviation connotation:
P-X: p-Xylol
P-TA: paratolunitrile
P-TE: methyl p toluate (pT-ester)
BME: methyl benzoate
HM-BME: hydroxymethyl-benzoic acid methyl esters
MM-BME: methoxyl methyl methyl benzoate
DMT: dimethyl terephthalate (DMT)
DMT-is ester (the thick ester stream of the DMT after the esterification) slightly=slightly
Thick DMT: the dimethyl terephthalate (DMT) cut after the thick ester distillation
High purity DMT: high purity terephthalic acid's dimethyl ester (high purity DMT intermediates or finished product)
DMO: dimethyl phthalate
DMI: dimethyl isophthalate
The heterogeneous mixture of DMP rutgers=DMT, DMO and DMI
MMT: terephthalic acid monomethyl ester
TA: terephthalic acid
MTA: moderate purity terephthalic acid
PTA: high purity terephthalic acid
PTA-p: pure terephthalic acid's (total content of MMT and p-TA＜50 ppm by weight)
TAS: terephthalaldehydic acid (4-CBA)
TAE: terephthalaldehydic acid methyl esters
Claims (7)
1. so-called slightly a kind of separation method of ester, the process of mainly producing of this thick ester is: the catalyzed oxidation of p-Xylol (p-x) and methyl p-methyl benzoate (p-TE), and subsequently will be from the reaction product methanol esterification of oxidation step in dimethyl terephthalate (DMT) (DMT) preparation process, obtain rich p-TE cut, thick DMT cut and high boiling point residual fraction, this method comprises, be equipped with a kind of dividing wall column or the distillation tower of tower before a kind of having, carrying out the separation of this thick ester in perhaps a kind of separating unit of the distillation tower that has a back tower.
2. as the desired method of claim 1, wherein the separation of this thick ester is to carry out under the condition of 100～280 ℃ temperature and 50～500mbar absolute pressure.
3. as the method for claim 1 or 2, wherein at this dividing wall column, perhaps the distillation tower of tower or back tower and/or in this preceding tower or this back tower before comprising is provided with the structure bag.
4. as at least one desired method in the claim 1～3, wherein should be circulated to oxidation operation by richness p-TE cut.
5. as at least one desired method in the claim 1～4, wherein this high boiling point residual fraction is fed to a kind of methyl alcohol alcoholysis or pyrogenic processes, and then is sent to a kind of operating unit that reclaims catalyzer.
6. as at least one desired method in the claim 1～5, wherein this thick DMT cut is further processed, produced the dimethyl terephthalate (DMT) and/or the terephthalic acid of higher degree.
7. method for preparing dimethyl terephthalate (DMT) (DMT), it mainly comprises following process steps,
The oxidation of-p-Xylol (p-x) and methyl p-methyl benzoate (p-TE),
-will be from the reaction product methanol esterification of above-mentioned oxidation step,
-so-called thick the ester that will generate is separated into rich p-TE cut, thick DMT cut and high boiling point residual fraction,
The purification of-thick DMT cut, desired as at least one item in claim 1～6, this method comprises, is being equipped with a kind of dividing wall column or the distillation tower of tower before a kind of having, and carries out the separation of this thick ester in perhaps a kind of separating unit of the distillation tower that has a back tower.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 97101064 CN1169421A (en) | 1996-05-07 | 1997-02-03 | Method for separation of crude ester in dimethyl terepthalate |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19618152.6 | 1996-05-07 | ||
| CN 97101064 CN1169421A (en) | 1996-05-07 | 1997-02-03 | Method for separation of crude ester in dimethyl terepthalate |
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| CN1169421A true CN1169421A (en) | 1998-01-07 |
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| CN 97101064 Pending CN1169421A (en) | 1996-05-07 | 1997-02-03 | Method for separation of crude ester in dimethyl terepthalate |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104797551A (en) * | 2012-09-28 | 2015-07-22 | 陶氏环球技术有限公司 | Process for the production of high purity glycol esters |
-
1997
- 1997-02-03 CN CN 97101064 patent/CN1169421A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104797551A (en) * | 2012-09-28 | 2015-07-22 | 陶氏环球技术有限公司 | Process for the production of high purity glycol esters |
| US9481629B2 (en) | 2012-09-28 | 2016-11-01 | Dow Global Technologies Llc | Process for the production of high purity glycol esters |
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