CS198264B2 - Method of producing dimethyl terephthalate - Google Patents

Abstract

Dimethyl terephthalate is prepd. by (i) oxidn. of p-xylene and recycled p-Me tolulate with air-O2; (ii) esterification of aromatic carboxylic acids with MeOH and (iii) dimethyl terephthalate separation and purification by distn. and crystallisation. Polycyclic cpds. contg. methylene-oxy-carbonyl bridges -CH2-OC=O, esp. p-xylyl-p-tolulate, (I) and its derivs., are separated after esterification step and recycled, entirely or partly, to oxidn. of p-xylene and p-Me toluate and/or oxidised separately at 120-250 degrees C under =25 atmos. press., in the presence of standard oxidn. catalysts, e.g. organic Co, Mn- and/or Ni salts. Selectivity of dimethyl terephthalate prepn. can be increased by 1-3 mol %.

Description

SUMMARY OF THE INVENTION The present invention relates to a process for the production of dimethylene terephthalate utilizing polycyclic compounds having mercylene oxycarbonyl bridges, in particular to p-xylethyl p-toluic acid derivatives of p-xylene esters which are formed according to known processes for producing dimethylethyl tthalate.

Processes for the preparation of dimetyl-containing hitherto consists of steps such as oxidation of p-xylene and methyl ester of p-toluic acid with air oxygen, aromatic carboxylic acid triethyls, which are obtained in the oxidation process, methanol, extraction and purification of the dimethyl dimethyl tertilate obtained. vacuum depilation and crystallization from methanol. Polycyclic compounds, among them compounds with methyleneoxycarbonyl lime which are formed in said processes, are waste products and are removed from the process as residues after de-distillation of methyl esters of aromatic carboxylic acid, mainly p-toluic acid and terephthalic acid esters. During the distillation of the aromatic carboxylic acid methyl esters obtained in the sterilization step, a minimal and random amount of about 0 to 20 percent of the mono-mono-polycyclic compounds passes into the deilate, which is the crude dimethyl terephthalate, from which it is recycled after the purification steps and the oxidation process. methyl ester of p-toluic acid.

Recent results in the improvement of the process for the production of dimethyl ethyl ether are based on the conversion of the waste residue after depilation of the aromatic and carboxylic acid methyl esters into p-toluic acid and dimethyl ether ethyl ester by heat treatment (US Pat. No. 3,914,287 /. or this residue with methanol / DE pat. Nos. 2,244,662 and 2,427,875]. These results, namely the improvement of the p-xylene consumption factor, are very good when compared to the conversion of polycyclic anhydride compounds, but on the other hand the conversion of polycyclic compounds with methyleneoxycarbonyl bridges to meetyleeter of p-toluic acid and dimethyl dimethyl etherate is not preferred. The remaining part of these compounds yields tarry polycyclic aromatic compounds, which are waste products.

In the research process for the manufacture of dimethyl terephthalate it has been found that the oxidation of p-xylene and ^{MFH yl} ^ <^ ^alkyl i9t ^ERU 8el ^{IOI p} - ^t °] ^ ew ^{_u> bf} from ^oytrdu to ^U sing h ^yp cat ^^ a ^ r ^ ^sf ori ^ ^ ^ vi vitnokUUriú ranož px ^{y1y1 alkyl} ester Selin ^yp -holuová ^п г Ьо j ^ d ^ ^ ^ IVa SAH-AI. aldehyde, carboxylic acid or ester SKU ^p IOU and meeУylrnoxykarbooylové mmshky -CH2-O-CO-.

^After xdeη ^ο χίΐ. ^ka ci ^{ah hese} ec ^ ^ од ^{010 b} y ^LZ proline OCR ^to áváo ^s oaleze ^{o1, e-EC on} LMI easily and in a high yield of around 80 to 90 of hmoinoitoích nxi.duúi atmospheric oxygen in příioo ° ^o t ⁱ from ^{oamych o} xi ^{dacecy ka} ta ^^ dr ^ ^o apr. ^to both ^ ^{о н} ^ ^сУ, omnganatýc ^y and ^oi l ^e toAt ^c У with ^a divided ^{ma8hOých огЬо tion (TAT} U ^{on ky} sel ^IOU p ^{- tl} Luo ^{ou to} Yssel ^and nu terephthalic ^ sheep ^and montmdhjflester acid tereftalcvé. '

At the same time it was found that mnnlssví policyklických compounds oeehjilenoxykarbooy - ^mm st ^{alkyl which form Bey} e ^{m oxidation of} p ^ ykou and oeeh ^ ester to ^y 8eli ^oi p - t ^o lu ^lv s ^{are zoačoé characterized} AC ^{and OEZ m} ^ ^oLZ TV ^{and I hese} c ^sloučeoin of des ^ lččním of ^the HKU after Dees ^^ ^ ^ ^y ^ eel I ^ ^1! 51 ^{гг й} aromatic carboxylic Selim to ^y / called crude ester /. This means that during distillation, the cyclic compounds are subjected to conversion as a result of the higher temperature used. This fact gives them ^ i ^ ls separaěních further research methods to 1ylesteru px ^{y y} p selioi holuové and derivatives thereof ^{here so} as ^to podatadě ^with IL ^{i i]} dec ^ice T ^e c ^h a ^^^ ο ^1st and can ^be incorporated into the oxidation process.

if the de-crosslinking of the crude esters is

J ^edoo du ^Cha battery ^ag ^ i ^ ¹¹¹ ^ destilačoíhi residue meehhlesttrů aromatic carboxylic kyselio neregenerivala fully methyleooxykarbonylovýmí polycyclic compounds with bridges. Tests of crude ester deficiency against expectations have shown that at relatively low temperatures of 23 to 245 ° C under a vacuum of 5.33 to 6.67 kPa, and at a minimum reflux / about 10 percent by weight based on and colony packing, it is possible to dequitiloilt qua p -tolic acid xylyl ester and its derivatives together with mono-hydroxyl methyl esters, i.e. the methyl ester of p-toluic acid, di-ethyl terephthalate and its isomers, i.e., di-mehlsophthalate and di-dihehloothophthalate, of the polycyclic-type radical.

Similarly, good results were obtained when the distillation residue of the aromatic carboxylic acid mehehl esters was vacuum distilled with the introduction of liquid β-holuic acid and dimethylene chloride chew as reflux.

The decomposition of p-xylyl ester of p-toluic acid and its derivatives can also be reduced by the use of flash distillation. of the aroootic carboxylic acid ethers. The decoction obtained from the displacement column contains about 20% of the total methyl ester of di-ethyl ether and di-ethyl-ethyl acetate, and 80% of polycyclic aromatic compounds.

This decocation under vacuum deflection, when the top temperature of the column is not greater than 255 ° C and at a vacuum of 6.67 kPa, alkylates the delatlate containing p-toluic acid p-toluate and its derivatives in an amount of about 90% by weight. with respect to the starting onions, and also the oococlockic methyl esters.

The object of the present invention is that the copolymers of olealene-oxycarbonyl-CH 2 O-C 0 O, especially p-xyllyl β-dl-p-xyl ester, and its derivatives are esterified after the esterification step. They are either recycled to the oxidation process of p-xylene and ol-p-holic acid ester or individually oxidized by an aerated pail at a temperature of 120 to 250 ° C and at a pressure of 2.5 MPa in the presence of organic cobalt, manganese and nickel salts.

The process according to the invention is carried out by carefully separating the p-xylyl ester of p-debulic acid and its ester derivatives together with the methyl ester of p-toluic acid and dihydroxyphthalate by depilation from the crude esters or distillation residue of the crude esters containing large amounts of diethyl ether. A mixture of mono-olefinic olefins containing p-xylyl ester of p-toluic acid and its derivatives is obtained, which is further separated in a known manner by vacuum distillation into the p-toluic acid m-hexyl ester fraction and the crude di-ethyltheyl ester from which impurities can be treated. Piperidine and its derivatives, by crystallization from methanol.

Meéhanol removed from oeehanolického solution obtained krystallzacl dloeehylleteftalátu, said solution contains in addition to p-xylilesteru acid pilin and derivatives thereof have isomers dioeehhitteeftalátu, i.e. dlmefhyllíoftal <carboxylate and dlmefhylolthoftalá t oeehhlester ^ ί ^ Η ^{oy оГ} 1 ^ ^у ^ ^1] ^ ^г 1 t ^e r acid ¹ ·. ^{P 1} - ^yl foro ^b enzoové, ttioetliylesUr ^{io alkyl} sel e ^rm it ^and then ^j1s rnoďsvi di ^m efh lthtrf ^{Y and L, and} the Isooery .. (Нти ^ ^e ditnetliyl НмакаШи ^and 8 ^ter. ÍúmIHuiré acidified ^{to about 01} ^ 8 t ^t r ^ ^l ш her portions of ^ o ^ nt in ^akuovo ^^ u ^ ^and residuals, Uwy containing mainly p-xylylester ptoluic acid and its derivatives, methyl p-toluic acid, methyl p-formyl-and DMT is recycled to the oxidation process of p-xylene and methyl p-toluate.

The mixture obtained by removal of methanol can be oxidized by air oxygen in a separate reactor at a temperature of 120 to 200 ° C and at elevated pressure in the presence of known oxidation catalysts, preferably organic salts of cobalt, manganese and nickel or mixtures thereof. After oxidation, the aromatic carboxylic acid mixture is esterified in a known manner with methanol to obtain dimethyl terephthalate and methyl p-toluate,

The complete separation of p-xylyl ester of p-toluic acid and its derivatives and their recycling to the oxidation process results in an increase in selectivity of the process for the production of dimethyl terephthalate by about 1 to 3 mol percent depending on the method used in dimethyl terephthalate.

The invention described herein ensures good selectivity of the process for the production of dimethyl terephthalate, even when a different charge is given to the process equipment, or the process equipment is failing, since it enables to recycle intermediates which have hitherto been considered waste products for incineration or special treatment, where large losses of p-toluic acid ρ-xylyl ester and its derivatives occurred.

Example 1

Crude esters, which are obtained in the manufacture of dimethyl terephthalate, and which contain:

p-xylene methyl benzoate methyl p-toluic acid methyl ester p-formylbenzoic acid methyl ester other compounds having a lower boiling point than dimethylterephthalate dimethylterephthalate dimethylisophthalate dimethylorthophthalate trimellitic acid trimethyl ester p-xylyl ester of p-toluic acid and its polycyclic compound anhydride compounds, which have a higher boiling point than dimethyl terephthalate have been treated by distillation, in particular by vacuum distillation.

It is distilled on a system of two acid-resistant industrial columns

0.2 OF weight 2.3 OF % by weight 32 of % by weight 2 of weight 0.2 of weight 50 of % by weight 6 of hmo tnos tnich 1 of weight 0.5 of weight 2 of weight 3 of weight 0.8 of weight

steel. The first column with a diameter of 2.6 m and a height of 6.9 m has 6 top-level trays and a second column with a diameter of 3.0 m and a height

28.0 m has 30 hat floors. The distillation system is equipped with evaporators, coolers and feed pumps.

Working conditions of the first column: column return flow temperature at the top of the column temperature at the bottom of the column pressure at the top of the column

Working conditions of the second column: temperature at the top of the column temperature at the bottom of the column

By weight relative to the quantity supplied,

249 ° C

200 ° C,

15.07 kPa.

240 ° C

235 ° C, top column pressure 6.67 kPa,

The above parameters ensure decocation from the second column in the form of crude dimethyl terephthalate with the following composition:

p-toluic acid methyl ester p-formylbenzoic acid methyl ester dimethyl terephthalate dimethyl isophthalate dimethyl orthophthalate tri trimethyl heptide

0.1 <7 weight 2.6 OF weight 83.6 of masanos tnich 8.1 of weight 1.1 of weight 0.9 of weight

p-toluic acid p-xylyl ester and its cyclic anhydride-type derivatives compounds having a boiling point higher than dimethyl tetrophthalate

The dimethylthetamine thus obtained

2.6

0.5

0.5. Methanol is removed from the filtrate, dibutyl acetate is obtained, and a pure residue is obtained having the following composition:

p-xylene 1,8 OF h ^ Onno tního οο ^ ιτ168ter of p-olenic acid 21.0 OF hmoShOStních benzoic acid oethyletter 1.7 OF weight weight P-formylbutyric acid 2.4 OF ym ^ onosnho other compounds which lower the temperature boiling than dioethyldetetholate 0.9 OF Iocouc ^ tního dioethyllttetfalát ' 23.8 OF hmoSnostního The dihydroxide salt and the substance 28.4 OF Iogouc ^ tního dioethyllsehySphalate 3.8 OF hmoSnostníht heioetУylt8tte heioellisic acid 3.1 OF Iocohetic o-holuic acid 1-xylyl ether and its ester derivatives 9.7 OF hmoSnos tního polycyclic anhydride compounds type 1, 7 OF weight other higher boiling compounds, than dioethyllttettatah 1.7 OF УmoShnsSniУo

air oxygen together with p-xylene in a 3 L mass reactor, which is provided

The residue thus obtained was oxidized by a ratio of 1.4: 1,

The process is carried out in a laboratory batch heating mantle, bubbler and cooling system, which separates the unreacted crude material for encapsulation.

Temperature and pressure are maintained through automatic control systems. When the oxidation process is carried out in lithium cobalt, lithium, and non-flammable salts of the fatty acids for 9 hours, the acid value of the semioxidated silica is 160 mg KOH / g,

After the oxidation process, the composition of the reaction mixture is as follows:

p-xylene 14.5 z hmosnostního oetУyle8tte benzoic acid 1.7 Z hmosnostního brooms of o-tslusve acid ester 8.3 Z hrnounotního p-phthroylbenzoic acid methyl ester a, 4 From Insect Sites other compounds having a temperature boiling lower than dioethyllhtettalate 0.2 Z УmoONOSTУo dioethyllhtettaláh 13.5 From the mortal. dioethyllssState 16.3 Z lincounotního d ioethyllseУySphalate 1.5 From У ^ с ^ ot ^ <^ other hioetilissic acid ester 1.4 Z hmoSNOSTУs o-toluic acid 0.5 Z insSnostního polycyclic anhydride compounds type 0.9 Z hmosnostního compounds having a higher boiling point than dioethyllttettaláh 0.8 Z hmoSNOSTУs p-toluic acid 25.1 Z hmoSNOSTУs ttetftaAsalic acid 2.9 From gross weight oysnoothyletser 12.0 From hmoShosSn £ ch

The degree of conversion of the p-xylyl ester of p-toluic acid and its derivatives is, as calculated from the balance of the oxidation process, above 90% by weight, calculated with respect to the final number of products such as p-oic acid, acid. hetetphthalic and moonooththalic acid, giving selectivity greater than 100 mooprocent, concludes that these acids also arise from the p-xylyl ester of l-tslusic acid and its derivatives, if the o-holic acid ester and its derivatives If they are considered as reactants in the oxidation process, the selectivity obtained is about 97 mol%, which corresponds to the ββΐΐ ^ίίϋϋϋε obtained for the oxidation of the pure reactants, namely p-xylene and methyl p-toluic acid. For identification and determination of the quantity of p-toluyl p-toluate. and its derivatives are used by gas chromatography and tactile spectroscopy.

The residue from the distillation of methanol from the filtrate resulting from crystallization having the composition given in Example 1 is oxidized in the laboratory reactor described in Example 1.

The oxygenation process is carried out in the presence of a catalytic system consisting of acetate, cobalt acetate and mixtures obtained in the oxidation process by oxidation of p-xylene with air oxygen. The amount and composition of the catalyst system is selected so that the cobalt concentration is % of the ion content, calculated relative to the charge, was 0.08%, the manganese ion concentration 0 _to 04% by weight, and that the reaction mixture from the oxidation p-xyle, which is added as catalyst activator, was 0%. 5% by weight. The process is carried out for 9 hours, at a temperature of 165 ° C and a pressure of 0.6 MPa. This gives a reaction mixture of the following composition:

p-xylene methyl ester of benzoic acid, p-toluic acid, other compounds having a lower boiling point than dimethylsulphephthalate or dimethylsulphate dimethyl ester p-toluic acid β-toluic acid orthophthalic acid with its terpentrylic acid and its polycyclic anhydride derivatives other compounds with a higher boiling point than p-toluic acid terephthyric acid terephthyl Terephthalic acid

The viscosity of the produced acids, specifically in traces

1.6% thick

9.5% of the total

2.3% УооГпоot

0.8% Ую ^ о o

23.5 7 Утоимto

8.0% hrnoHio axial

3.5 From Утотс! Tai

3.0% w / w

0.8% h 2 O 4

1.5% colloquial

2.0% Уто ^ ш ^!

15.0% УоошозГо ^ У

2? 5% Уто ^ т

6.0% by weight of the p-toluic acid, tetrophthalic acid and methyl meththalic acid ratios calculated with respect to the converted t -toluic acid, p-toluic acid ester and its derivatives is 96.5 то ^ ю prices ta.

Example 1 a d 3

The meta-alcohol residue from the filtrate originating from the crystallizers having the composition of Example 1 is continuously fed together with the methyl ester of p-toluic acid to industrial reactors, to which p-xylso and the catalyst in the form of an aqueous solution of cobuatoateyo, maiggnatyo and 0Lks1ottéyo. H. The minor fractions of the reactants and the individual components of the ttlyzatore are as follows:

I díl. p-xylene

1.2 parts of p-thioic acid methyl ester

0.3 part residue after d <e; by filtration of the filtrate resulting from crystallization

1.75. 10 4 4 parts of the ions

8.8. 106 parts of mahogany ions. 10 ~ 6 parts of acidic ions.

Everything was oxidized in a continuous manner in three stainless steel reactors, each having a working capacity of 60-3, which already contain a recycle mixture from earlier tests. The reactors pass the low-pressure steam generator incorporated in them, serving as a heat sink from the oxidation reaction. The reactors are equipped with a vapor com- plex, a waste gas cooler, a septator and a charcoal for the removal of p-gas from the waste gases.

From the calculation of the oxidation process production, the selectivity of the reaction is 96.8 m @ -1 to 188264 cent, which is the same result as in the identical oxidation test of a mixture of p-xylene and methyl p-toluate containing 0, 8 Of higher boiling point weight compounds; than dimethyl terephthalate.

Example d

The distillation residue of the crude esters remaining in clade 1 has the following composition:

p-toluic acid methyl ester other compounds having a lower boiling point than dimethyl terephthalate formylbenzoic acid methyl ester dimethyl terephthalate isomers dimethyl terephthalate trimellitic acid trimethyl p-toluyl ester and its derivatives polymers of the cyclic anhydride type compound other compounds having a higher boiling point than d ime In the distillation system described in this composition, a vacuum reflux is obtained at the following operating temperature at the bottom of the column.

This residue is distilled on a laboratory column

i, 5 OF weight 0.5 OF weight 1, 8 OF weight 19.5 OF weight 3.5 OF weight 2,0 OF material with you 25 OF % by weight 40 of masanos tnich 6.2 of weight

conditions of the first column:

235 ° C

5,33 к Pa

From weight to fill.

glass filling and the efficiency of 4 theoretic floors.

The temperature at the center of the column is 256 ° C, the vacuum is 5.33 kPa, the return flow is 12% by weight relative to the packing. 50 parts by weight of distillate relative to the filling were obtained. The distillate has the following composition:

p-toluic acid methyl ester other compound with lower boiling point than dimethyl terephthalate formylbenzoic acid methyl ester dimethyl terephthalate dimethyl terephthalate trimethyl trimethyl ester trimethyl p-toluic acid ester and its polycyclic anhydride-type derivatives, other compounds having higher boiling point than dimethyl terephthalate

3.2 OF weight 1, o OF masanos tni 2.5 of material with the dark 40 of % by weight 7 of masanos tnich 3.6 of hmo t no s tní 33.7 of weight 5 of massive ch

The distillate was crystallized twice from methanol, at weight ratios by weight of distillate and 2 parts by weight of methanol.

All is dissolved at the boiling point of the solvent, then a portion of dimethyl terephthalate is crystallized at 40 ° C. After distilling off the solvent from the methanolic solution, the residue had the following composition:

methyl ester of p-toluic acid other compounds having a lower boiling point than dimethyl ester of formylbenzoic acid methyl ester dimethyl terephthalate isomers of dimethyl terephthalate trimellitic acid trimethyl ester of p-toluic acid ester and its anhydride-type polyeylic compounds.

other compounds having a higher boiling point than dimethyl terephthalate

From weight

1.5% by weight 3.8 OF weight 7.7 OF weight 10.5 /O weight 5.5 of weight 51.8 of weight 6.2 weight 8.0 of hmo t n o c h

This residue was oxidized in portions in a small 200 ml laboratory reactor equipped with air supply, steam extraction, waste gas collection, heating mantle and vapor condensate. Oxidation in the presence of cobalt, manganese and nickel salts of mutant acids, for 10 hours, at 165 ° C, gave a reaction selectivity of 92.5 mol%, with a degree of conversion of the polylyl ester to less than toluene. and its derivatives about 40%.

Similarly, the selectivity of the oxidation of the p-toluic acid swabs was 94 p < t &gt;

Claims (3)

CLAIMS 1. A process for the production of dimethoxytettalate by catalytic oxidation of β-oleic acid and circulating β-tolylic acid meth ester by an air crust at elevated temperature and pressure, aromatic carboitic acid methaool, separation and purification. eStylt ^ ^ te ^ ^s: distillation and krуss.jIízici terephthalate, vyznoluiící in that after polycyclic compound with methyl thylenoitkarbotylovými MDSTk -C.H2 ~ 0-C-0, especially p "iytylesttr ptoluic acid and derivatives thereof, with after the esterification stage, the recycle to the oxidation process with p-ol and methyl p-toluic acid ester or individually with air acid is used. At a temperature of 120 to 250 ° C and at a pressure of 2.5 MPa in the presence of organic salts , manganese and nickel, 2. The method according to item 1, vyΣηοου ^^! 2. The method of claim 1, wherein the polycyclic compounds with methylcarbonyl chains are separated from mixtures of polycyclic compounds formed in the production process of the methyl ester, separating the p-xyls of the p-toluic acid ester and its derivatives together with dimethhltertaphthalase or distillation thereof from the crude ester ester residue. 3. Process according to claims 1 and 2, vyznoauujcí in that R ^on the compound with lycyk.lické methylenkarboiy 1ovými mmstky margin-network, together with the compounds contained in the raw dimethy1ttrsftalatu in r.imthanolu krylSalizaci during, and after separation of methanol and, optionally, The isomers of dimethyl phthalate are sparged to the oxidation stage of p-illene and p-toluic acid methyl ester.