JPS609491B2 - Anthraquinone production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for producing anthraquinone from naphthalene.

It is already known that asothraquinone can be prepared by oxidizing anthracene with chromic acid or dichromate [see FIAT Final Report N
o. 1313 Vol. 2, p. 19).

This process requires an expensive oxidizing agent, is difficult to carry out continuously, and has a starting material (anthracene) which is obtained virtually only from mineral coal and is therefore available in limited amounts.
use. Therefore, more recently attempts have been made to produce anthraquinone from new raw materials. According to current methods, naphthalene obtained from both coal and natural oil is used as starting material.

In this process, naphthoquinone is first produced by oxygen oxidation of naphthalene, and then the naphthoquinone is reacted with butadiene in a Diels-Alder reaction to produce the tetrahydride. Anthraquinone is produced by producing anthraquinone and finally oxidative dehydrogenation of the latter with oxygen. Phthalic anhydride is obtained as a by-product. A method of this type is described, for example, in DE 22 45 555 A1. In order to carry out the process industrially on a large scale, it is necessary that the process be carried out continuously, that as few separation and purification steps as possible are necessary, and that the losses of the product and the pollution of the environment are as low as possible. It is necessary to design the process in such a way that as much of the product stream obtained in the process as possible can be recycled.

Furthermore, the formation of deposits, for example in the form of tars or crystalline precipitates, must be substantially avoided. The reason is that otherwise the operation would have to be interrupted due to blockage. The aim of the process according to the invention is to provide a process of a type that allows an industrially and economically advantageous process for the production of anthraquinone from naphthalene.

Now, according to the present invention, naphthalene is oxidized with a gas containing oxygen and inerts in the presence of a vanadium-containing catalyst, and in the {B' cooling system, from the reaction product obtained from the separating a liquid product containing naphthoquinone, phthalic anhydride and naphthalene from a cycle gas containing essentially oxygen, naphthalene, carbon dioxide and inert substances; is reacted with excess butadiene, thus obtaining a liquid product containing essentially tetrahydroanthraquinone, phthalic anhydride and naphthalene,
the product from 'C} into a distillation system consisting of a column and a boiler having a sludge section and a stripping section, the stripping section and/or the boiler being of such construction as to prevent rapid flow of the feed mixture; supplying an oxygen-containing gas to the lower part of the distillation system, removing a naphthalene-containing gas from the column section of the distillation system, and removing a liquid mixture containing essentially anthraquinone, phthalic anhydride, and naphthalene from the boiler; The naphthalene obtained at the top of the column is cooled and partially liquefied, and the naphthalene obtained at the top of the column is cooled and partially liquefied. ) and 'F} separates the mixture essentially containing phthalic anhydride at the top and the crude anthraquinone at the bottom. , ■ Impurities with a boiling point lower than phthalic anhydride are optionally separated at the top together with phthalic anhydride, and phthalic anhydride is separated together with impurities with a boiling point lower than phthalic anhydride at the bottom of the column. ,'F
to another column in which substantially pure phthalic anhydride is separated overhead and phthalic anhydride rich in high-boiling impurities is separated at the bottom; (G
), fresh oxygen-containing gas is fed to the process reactor and/or plate, and fresh naphthalene is fed to the process [
B}1 and fresh butadiene to step 1, and maintaining the following circulation system: 'a - Step' Separate the oxygen-containing cycle gas from BI, separate a portion from time to time to naphthalene, and After removing a partial stream from the system, it is circulated directly to the seed, and the remainder of the recycled gas from process 'B) is recycled to the process {
The naphthalene-containing gas from step [8} is circulated to the process leg, and the naphthalene-containing gas from step {c' is circulated to step ■, 'd}.
Recirculating the naphthalene from step {E) to step ■ and/or process leg; [e} separating excess butadiene from the product from step [q] and recycling to the feed product of step {e};
f} recycling the liquefied naphthalene from the process pan to the feed product of step 'C} or upstream of the process pan C};
(h) some of the impure phthalic anhydride from step (G) is recycled to the process pan or upstream of step {D'; H
) is recycled to the feed product of step (C'); (i) the bottom product from step (H) is recycled to the feed of step (C');
A method for producing anthraquinone, which circulates upstream of gong, has been discovered.

The present invention relates to the combination of ~(H) of the device and the circulatory system 'a}~
Regarding these connections according to (i).

When carrying out the process according to the invention, a gas mixture containing molecular oxygen and circulated under pressure through the two reaction steps is used for the oxidation of naphthalene to naphthoquinone and phthalic anhydride and for the oxidative dehydrogenation of tetrahydroanthraquinone. can. This circulating gas must exceed the total pressure in the system of approximately 3 bar. The absolute pressure of the reaction is 3-1
It may be 0 bar. Distribution of the recycle gas between the two oxidation stages can be effected by conventional control means depending on the oxygen requirements of the two stages.

In addition to oxygen and naphthalene, the cycle gas contains various other components such as water vapor, carbon dioxide, carbon monoxide, nitrogen and other inert substances. A small stream of this gas can be separated from the system, for example through a scrubber, so that the amount of inert components is not too large. Gases separated from the system can be rendered harmless by conventional combustion or by catalytic combustion, for example over a palladium catalyst. Advantageously, the naphthalene in the cycle gas is maintained in an amount of 1 to 10% by volume. Naphthalene oxidation is then carried out using excess naphthalene, unreacted naphthalene from this step is recycled into the cycle gas, and fresh naphthalene is added in an amount corresponding to the chemical consumption. For the oxidation of naphthalene, it is advantageous to add small amounts of sulfur compounds, such as sulfur dioxide, to the feed gas.

In the method of the invention, high boiling reactants and reaction products,
For example, naphthalene, phthalic anhydride and naphthoquinone are
They are not initially separated and are fed together to the subsequent reaction step after the oxidation of the naphthalene. The reactor used to carry out the oxidation of naphthalene may be a conventional tubular reactor comprising a tube of 2 to 12 skins in length, preferably 3 to 8 skins in length.

The gas mixture has a flow rate of 0.5 to 5 skins/sec and a residence time of 1 to 9
can pass through the tubular reactor in seconds. The heat from the highly exothermic reaction is
For example, it can be removed by using a secondary cooler and using a salt melt. The reaction gas is heated to the required reaction temperature, e.g.
For heating from 0 to 450 °C, a gas/gas heat exchanger can be installed upstream of the reactor. The tubes in the tubular reactor may be only partially filled with catalyst, and the remaining portion of the tube may be filled with inert material as a preheating zone. The reaction gases leaving the naphthalene oxidation reactor are not adequately liquefied by direct cooling.

The reason is that tar-like products can be formed in this case by secondary reactions. Therefore, the reaction gases are first cooled to at most 280° C. in conventional coolers, e.g. Cool to below the fog point of phthalic anhydride. The cooling system suitably operates with a high liquid circulation system, bringing the already cooled multiple liquid reaction products into intimate contact with the hot or precooled reaction gas. The heat extracted from the reaction gas can then be removed through a heat exchanger located in the liquid circulation system. The deposits on the surface of this heat exchanger raise the temperature of the cold soot to 80~80°C.
It has been discovered that when set in the range of 150q○, protection can be achieved for a long period of time, for example for several weeks. The gas leaving this condensed system may still contain small proportions of reaction products, especially naphthoquinone.

They are therefore suitably subjected to countercurrent washing with naphthalene. The fresh naphthalene required for the entire process is advantageously introduced into this washing system and enters the oxidation reactor via various circulation systems. Steam can also be added to the feed product to the oxidation reactor.

Furthermore, it is advantageous to add sulfur compounds, such as sulfur dioxide, to the feed gas in such an amount that the feed gas contains, for example, 1 to 60 sulfur compounds. The products required for further processing to anthraquinone are separated from the liquid circulation of the condensate system. The combination of a condensing system and downwash with naphthalene will be referred to as a quench system in connection with the following. The liquid product containing essentially naphthoquinone, phthalic anhydride, and naphthalene and separated from the quench system is reacted with butadiene to produce tetrahydroanthraquinone.

Since butadiene is very susceptible to polymerization, blockages should generally be expected, especially in the reactor immediately after the butadiene feed point. Additionally, a proportion of low volatility retentate may be formed as a side reaction of this reaction. These disadvantages can be avoided by carrying out the Diels-Alder reaction as follows. Excess amount per mole of naphthoquinone, e.g. 2-2
0 molar amount of butadiene, 90-200°C, preferably 9
Temperature of 0-1300C, 10-300 minutes, preferably 5
The feed mixture is further diluted with the naphthoquinone-containing naphthalene using a reactor inline time of 0 to 100 minutes and, inter alia, in the mixing conduit. The naphthoquinone-containing naphthalene and/or phthalic anhydride suitable for this dilution can be obtained at any other point in the overall process of anthraquinone production. For example, naphthoquinone-containing naphthalenes are separated at the top of a column in which the oxidative dehydrogenation of tetrahydroanthraquinone to anthraquinone occurs and the remaining naphthalene is separated. The Diels-Alder reactor may, as is known per se, be of the construction of a delay tube or a kettle cascade or a combination thereof.

The reaction pressure of this reactor is 5-50 bar, for example 10-3
It is 0 bar. Unreacted butadiene is then separated from the product leaving the Diels-Alder reactor.

This can be done, for example, by heating or by applying a vacuum. The butadiene separated in this way is recycled back to the reactor through a suitable single-stage or multi-stage compressor. If small amounts of naphthoquinone are always present, polymerization reactions during circulation can be prevented. The butadiene consumed during the reaction is replaced by a supply of fresh butadiene. Since commercially available butadiene always contains a certain proportion of other hydrocarbons, such as butane and butene, it is advantageous to continuously or discontinuously separate a substream from the recycled butadiene. A mixture which is present and substantially free of butadiene and consists essentially of naphthalene, phthalic anhydride and tetrahydrophanethraquinone is subjected to oxidative dehydrogenation.

This oxidative dehydrogenation is carried out under a pressure of 1 to 20 bar, preferably 5 to 20 bar, and at a temperature at which the naphthalene evaporates. Oxidative dehydrogenation is carried out in a distillation system. In this system, the heat of reaction can be used to evaporate naphthalene. As already mentioned, a partial stream of the oxygen-containing cycle gas can be introduced into this distillation system and the oxygen contained in this partial stream can be used to carry out the oxidative dehydrogenation of tetrahydroanthraquinone to anthraquinone. However, it is also possible to feed the oxidative dehydrogenation with a fresh gas containing, for example, 1 to 2% by volume of oxygen and nitrogen and/or other inert substrates. The residence time of this reaction is 15-120 minutes, preferably 30-60 minutes. The distillation system consists of a column and a boiler having a rectification section and a stripping section, the stripping section and/or the boiler being of such construction that the above-mentioned residence times are obtained. For this purpose, e.g. foam bell trays with overflow weirs, valve trays,
A sheep tray or drip tray can be installed in the stripping section of the tower. However, a boiler consisting of several chambers may also be used. Preferably a reaction cascade is used as boiler. The naphthalene, which still contains a small proportion of naphthoquinone, is passed into the column section of the column. Some of this naphthalene is condensed and recycled upstream of the Diels-Alder reactor. A further portion of the naphthalene is recycled to the naphthalene oxidation together with the recycle gas that has passed through the precondensing column and/or together with fresh gas. Distillation boilers essentially contain anthraquinone,
A product consisting of phthalic anhydride and naphthalene is obtained. The liquid product from the boiler of the distillation system is first fed to the column where naphthalene is obtained essentially overhead and also contains essentially phthalic anhydride and anthraquinone and in some cases still small amounts of naphthalene. A liquid mixture is obtained at the bottom of the column.

This column is preferably carried out under vacuum. The product obtained in the column section is recycled to the naphthalene oxidation after optional condensation and evaporation in the presence of the overhead product or a portion thereof from the above-mentioned distillation system. The naphthalene obtained at the top may also or exclusively be recycled to the quenching system. The bottom product obtained from the column which partially or completely separates the naphthalene and which contains anthraquinone, phthalic anhydride and in some cases small amounts of naphthalene and a proportion of high-boiling products is fed to a further column. and separate phthalic anhydride and naphthalene, if present. The column may be of conventional construction and is suitably operated under vacuum. Crude phthalic anhydride is separated from the top, optionally together with residual naphthalene. According to the invention, a portion of the crude phthalic anhydride thus obtained is recycled to the distillation system. This circulation can take place not only directly to the column, but also completely or partially to the boiler at any time. - Circulation may also be carried out upstream of the distillation system.
No crude anthraquinone is obtained at the bottom of this column. The crude phthalic anhydride obtained in the column section of this column and not recycled is purified in the following manner: The crude phthalic anhydride is fed to a column which is preferably operated under vacuum.

This tower may be a normal Kazuto tower. From the top of the column, the low-boiling product is taken off at any time together with naphthalene and phthalic anhydride. This column product is recycled to the process, suitably to the Diels-Alder reaction stream. In order to obtain substantially pure phthalic anhydride from the bottom of this column, the remainder of the quinone,
Among these, it is necessary to remove naphthoquinone. In order to obtain substantially pure phthalic anhydride, the bottom product from the column which separates naphthalene and low-boiling by-products from phthalic anhydride is optionally fed to a further column through a separate device.

This column provides substantially pure phthalic anhydride as overhead product. The bottom product from this column is recycled to oxidative dehydrogenation. Any low-boiling compounds that may still be present may be separated in the upstream column and fed to the overhead product by separation of the low-boiling products from the phthalic anhydride, or substantially pure phthalic anhydride may be delivered at the end. is separated as a side stream in the upper part of the column and in this case also the overhead product from the last column containing low-boiling compounds is added to the overhead product from said column.

The purification of the crude anthraquinone obtained with the process according to the invention is not a subject of the invention.

This can also be done by distillation. Essentially many evaporator configurations are possible for this distillation, with thin film evaporators being preferred. The anthraquinone is separated from this distiller as a gas, preferably under normal pressure or under slightly reduced pressure, while the high-boiling impurities are obtained essentially in solid form and removed from the system using a suitable discharge device, for example a discharge screw. . The gaseous anthraquinone can be fed to a distiller for further purification. Preference is given to using a thin-film evaporator equipped with a simmering fitting of conventional construction, in which the anthraquinone is purified under reflux and separated off in liquid form as overhead product. Some of the anthraquinone can be recycled to the column to separate phthalic anhydride and anthraquinone.

Residual anthraquinone can be separated from the residue at the bottom of the evaporator by sublimation or extraction. An industrial example of the method according to the present invention will be explained using the drawings.

1-5% by volume of naphthalene, 1-10% by volume of oxygen, 1-12% by volume of water vapor, 0-12% by volume of carbon dioxide, 0-3% by volume of carbon monoxide and 100% of an inert substance, e.g. nitrogen.
The gas mixture containing the remaining percent to give is fed through conduit 10 to tubular reactor 1 under a pressure of 2 to 10 bar.

The tubular reactor 1 contains tubes having a length of 3 to 12 and a diameter of 20 to 5 tubes and filled in whole or in part with a vanadium-containing catalyst arranged as a fixed bed. During the oxidation, the temperature is maintained between 250 and 500 oo using a salt melt. The gas mixture flows through the tubular reactor at a speed of 0.6-5 m/s (based on empty tube). The gas exiting the tubular reactor is optionally precooled with an evaporative cooler to a temperature above 280 oo and then fed through conduit 11 to liner system 2 .
The rapid cooling system 2 consists of two stages. In the first stage, the gas fed through line 11 is quenched and at a temperature below 200 qo, preferably below 15,000 qo, a liquid mixture containing essentially naphthalene, naphthoquinone and anhydrous naphthalene is separated from the bottom of the quencher through line 16. do. The uncondensed portion of the gas supplied in conduit 11 exits the top of the quencher at a temperature below 150 oo. These gases are fed to a scrubber where they are scrubbed in countercurrent flow with the naphthalene. The scrubber is supplied via conduit 12 with the fresh naphthalene required for the entire process. Gas 13 leaving the scrubber is distributed into two streams 41 and 15. A portion of stream 41 is removed from the system through conduit 40. Preferably, the naphthalene present in the four streams is separated off, for example by cooling or washing. This recovered naphthalene is preferably added to the feed naphthalene 12. The portion of the gas stream 41 that has not been separated from the system is fed to the tubular reactor 1 through conduits 14 and 10. The liquid product 16 separated from the quenching system 2 is passed through conduits 17 and 18 to the reactor 3 after addition of naphthalene 36 recycled from the column 6.
supply to.

Therefore, naphthoquinone is reacted with butadiene in a Diels-Alder reaction to produce tetrahydroanthraquinone. Fresh butadiene is added through conduits 43, 20, 19 and 18, and optionally naphthoquinone-containing naphthalene from the top of the distillation system through conduit 30 and conduit 22.
The excess butadiene separated off after the Diels-Alder reaction is added to this butadiene. This reactor 3 may have the structure of a tubular reactor. In this reactor, naphthoquinone is converted to tetrahydroanthraquinone in a laminar flow at a residence time of 0.1 to 5 hours, a temperature of 60 to 200°C, a pressure of 3 to 120 bar and in the presence of at least 3 moles of butadiene per mole of naphthoquinone. Transform. The reactor may have a kettle cascade configuration. The product mixture leaving reactor 3 is separated through conduit 21, excess butadiene is separated off, for example by reduced pressure, and fed back to the feed product through conduit 22. The remaining product stream 23 is fed via line 24 to the reaction of the tetrahydroanthraquinoso with oxygen in the distillation system 4; a partial stream 25 can optionally be fed to the column 6. The distillation system for the complete or partial separation of naphthalene from the mixture present after the Diels-Alder reaction and the simultaneous conversion of tetrahydroanthraquinone to anthraquinone consists of a column and a boiler having a stripping section and a distillation section, The stripping section may include an enclosure that prevents rapid flow of the feed mixture 24 and/or the boiler may be in the form of a classroom.

Preferably, the boiler consists of a kettle cascade or chambers arranged on top of each other. If a kettle cascade is used, this may be upstream of the column. In this case, the oxidative dehydrogenation of the tetrahydranethraquinone takes place essentially outside the column, and only the separation of the naphthalene is required. In this case, the heat generated during oxidative dehydrogenation is removed by evaporation of the naphthalene. Oxygen required for the conversion of tetrahydroanthraquinone to anthraquinone is obtained by rapid cooling system 2.
Conduits 15 and 4 in the form of a portion of the gas (circulating gas) leaving the
5 to the lower region of the stripping section or to the boiler of column 4. Additionally or exclusively, it is also possible to supply fresh gas, for example an oxygen/nitrogen mixture, to the distillation system 4' via conduits 46 and 45. Distillation system 4 has temperature 1
00 to 30,000 and pressures of 1 to 20 bar. All or a portion of the naphthalene introduced with the feed product 24 and the unreacted portion of the further introduced gas 15 and the gas containing impurities with a lower boiling point than phthalic anhydride and by-products, such as naphthoquinone, are transferred to the top of the distillation system 4. through conduit 29. A portion of the naphthalene and naphthoquinone contained in stream 29 is separated off, for example by condensation, and optionally recycled through line 30 to the butadiene 20 and 43 used in the Diels-Alder reaction. The portion not separated from stream 29 is recycled to oxidation reactor 1 through conduits 31, 9 and 10. The liquid mixture essentially containing anthraquinone, phthalic anhydride and, in some cases, naphthalene formed is separated from the boiler of distillation system 4 via conduit 27. Anthraquinone-containing stream 2
7 is fed to column 5 where crude phthalic anhydride is obtained at the top 33 and crude anthraquinone is obtained at the bottom 32. Column 5 is operated under vacuum, for example between 100 and 900 mbar. The crude anthraquinone 32 obtained at the bottom of column 5 may contain high-boiling impurities and by-products which can be removed by further purification, for example by distillation. The overhead product from column 5 consisting of crude phthalic anhydride 33 is divided and a portion thereof is passed through conduit 34.
and 28 to distillation system 4, and the remainder is fed to column 6 through conduits 35 and 26. A conventional vacuum column is installed upstream of column 5 to separate off the remaining naphthalene.

The overhead product is evaporated into the recycle gas system and recycled to the naphthalene oxidation system 1 and/or the quenching system 2. The overhead product 35 from column 5 is fed to column 6. Tower 6 has a temperature of 200-3
00qo and can be operated under vacuum. The compounds having a lower boiling point than phthalic anhydride and introduced together with the feed stream 26, in particular naphthalene, are obtained together with a certain amount of phthalic anhydride in the column section of column 6 and are passed through line 36 to the feed of reactor 3. recycled to the product. Phthalic anhydride is obtained at the bottom of column 6, which still contains small amounts of impurities. This phthalic anhydride is fed through conduit 37 to a further column where substantially pure phthalic anhydride is separated as overhead product 38, while also containing anthraquinone and other impurities in addition to phthalic anhydride. A wet bottom product 44 is separated. The bottom product from column 7 is passed through conduits 44, 39 and 28 to column 4 and/or
or circulated to the device 3 through conduits 44, 42, 20, 19 and 18. Conduit 8 and optional conduit 4 for compensating the oxygen consumed in the feed products 1 and 2 fed to the entire system.
6, fresh naphthalene through conduit 12, and fresh butadiene through conduit 20.

The products separated from the total system are crude anthraquinone through conduit 32, substantially pure phthalic anhydride through conduit 38, and a portion of the recycle gas through conduit 40. All other product streams can be recycled. Some of the process techniques for the series of reactions can be performed using known methods. Despite the fact that, for example, a tubular reactor is a preferred embodiment, it is essentially also possible to use other reaction systems, for example fluidized beds or moving beds, for the oxidation of naphthalene. While the cooling and quenching systems described are certainly examples of preferred uses, improved constructions may also be useful.

A delay tube (d
Although an elaytube is preferably used, the reaction may essentially be carried out in other apparatuses, such as a flywheel. The oxidative dehydrogenation of tetrahydroanthraquinone is suitably carried out in a cassava column, although bubble columns or other reactors are also convenient. The columns for processing the subsequent reaction products may be of customary construction, for example sieve tray columns, bubble bell columns, packed columns or bulb tray columns. Stainless steel and C steel with coatings on their surfaces have been found to be suitable materials for the devices and conduits used in the present invention.

Coatings that can be used are, for example, plastics or enamels. When using uncoated C steel,
The formation of high-boiling products and deposits increases rapidly. The process of the invention makes it possible to produce anthraquinone from naphthalene in a continuous process and surprisingly allows the formation of by-products and deposits to be greatly suppressed.

Moreover, with the circulation system of the present invention, substantially all of the product stream except the final product obtained in the process can be reused. Product losses and environmental pollution are kept low in this way. Anthraquinone can be used as a starting material for the production of dyes [see cf. UI1mannsEncy
clopadieder enterprise chnischenChem
ie, Volume 3, pages 662 onwards, 3rd edition (1953)],
The phthalic anhydride formed as a by-product can be used as a starting material for the production of plasticizers and many other chemical syntheses [see cf. mlmannS EnCyC1padie
der niSchenChemie. 3rd edition (1967), from page 556 onwards.

The following examples illustrate the method according to the invention in more detail, but without limiting it. EXAMPLE The oxidation of naphthalene to naphthoquinone was carried out in the gas phase using molecular oxygen in a tubular reactor of conventional construction and cooled with a salt melt through a secondary cooling cycle.

The reactor had a tube count of 48, 6 in length and 32.8 in. willow tube. The test catalyst charge was approximately 3.5 cm high and corresponded to a total catalyst volume of 145 cm. The catalyst consisted essentially of vanadium pentoxide, silica and potassium sulfate. The pressure at the inlet of the reactor is 6 bar, and the temperature of the salt melt is 330 oo.
Met. Naphthalene approximately 2.5% by volume, oxygen approximately 6% by volume
A gas stream of 300 degrees/hour (standard conditions) containing about 6% by volume of water vapor was passed over the catalyst. The gas stream could contain, among other things, nitrogen and CO2, as well as small amounts of CO and other gaseous components, in addition to these components. In the reaction, oxygen is added to about 50
% converted. The reaction gas was fed into a conventional tubular reactor at 2800
0 (evaporative cooling) and then contacted with the liquid reaction product in a quench system. At this stage, the gaseous product was fed in countercurrent to the liquid reaction product. The bottom temperature of the quenching machine is 1
2000, and the recycle stream of liquid reaction product to the quench top was passed through a cooler with a lacrimal fluid of 10000. The exiting gas had a temperature of approximately 105 Qo. In order to separate the reaction products contained in the gas according to its partial pressure, the gas was subjected to washing with fresh naphthalene before being recycled to the oxidation reactor. For this cleaning, use approximately 20k9/ml of fresh naphthalene.
provided time. The gas coming out of the top of the washing machine is about 3% oxygen.
and about 0.5% naphthalene. This was circulated through the reactor using a blower. In order to dehydrogenate the tetrahydroanthraquinone, a portion of this gas stream was fed to a reaction stage installed for this purpose and left at the top located in this reaction section. This gas was fed together with naphthalene such that the total stream in the oxidation reactor for the oxidation of naphthalene to naphthoquinone contained about 2.5% by volume of naphthalene by adjusting the condensation temperature in the column. The consumed oxygen was fed into the system in the form of air, and by appropriate switching the oxygen content in the oxidative dehydrogenation stage of tetrahydroanthraquinone to anthraquinone was approximately 8.5% by volume. Inert gases contained in the gas, especially nitrogen and gaseous by-products formed, especially day 20, C
02 and a portion of CO must be taken from the two total gas cycles. This was done by separating the appropriate sub-streams which were removed from the process. That is, the two gas cycles were of closed type. In order to maintain the oxidation of naphthalene to naphthoquinone, it was necessary to continuously feed water vapor into the circulation gas stream of the oxidation reactor so that the abovementioned 6% by volume value was obtained. Furthermore, a small amount of sulfur compound, preferably S02, was added continuously or discontinuously to the naphthalene-containing gas to be oxidized such that the content of sulfur compound was between 5 and 5Q. The washed and condensed liquid reaction products were separated together from the quench system. The base was about 75k9/hr and contained about 10% naphthoquinone, 7-10% phthalic anhydride as a by-product and excess naphthalene. This crude reaction product was fed directly to the Thiels-Alder reaction with butadiene without any treatment. The reactor used was a three-chamber Takashi kettle with a downflow delay tube capable of heating to temperatures of 100-150 qo. The reaction was carried out at 120 qo. Butadiene was added in excess, especially in an amount of 10-12 kg/h.

The reaction was carried out at a pressure of 20 bar and a residence time of approximately 90 minutes. After the reaction, the mixture was placed in a container and excess butadiene was removed. This butadiene was compressed again to 20 bar in the compressor and reused in the Diels-Alder reactor, the consumed butadiene being replenished by the introduction of fresh butadiene. When circulating the butadiene, a small amount of the crude product from the Diels-Alder reactor was added at one or more points in the conduit. The product from the Diels-Alder reactor is subjected to a third reaction stage without further intermediate treatment,
That is, it was supplied to the oxidative dehydrogenation of tetrahydroanthraquinone to anthraquinone.

The amount was approximately 80k9/h and the product contained 6-7% of tetrahydroanthraquinone and 6-7% of phthalic anhydride, as well as small amounts of impurities and a small amount of excess naphthalene. The oxidative dehydrogenation reactor had a structure as a rice cracker tower. The tower had a diameter of 30 ribs and a height of 8.7 mm. A valve tray was installed in the stripping section of the column. The feed product was fed from the bottom of the column. The bottom of the column was a three-stage chamber cascade, each chamber arranged on top of the other. In addition, about 12 k9/h of phthalic anhydride from the downstream column for the separation of phthalic anhydride and anthraquinone was also recycled to the stripping castle. The above-mentioned circulating gas (standard condition) was supplied to the bottom of the tower. The composition of the gas is approximately 8.5% oxygen and 0 naphthalene.
．． 5% by volume, plus the above-mentioned inert gas component. This column is operated at an internal pressure of 5-7 bar and a bottom temperature of 200-2.
It was operated with 2000. Oxidative dehydrogenation of tetrahydroanthraquinone occurred virtually quantitatively. In the column, the crude naphthalene was rectified and substantially separated from phthalic anhydride. At the top of the column, the temperature of the condenser was adjusted such that the gas passing through the column was desirably saturated with naphthalene, e.g. 3-5% by volume, and a sufficient portion was at reflux. Approximately 60 k9/h of crude product was separated from the top chamber of the three-stage chamber cascade.

The product contained about 10-20% anthraquinone, 30-50% naphthalene, about 5% high boiling residuals, and about 1% unknown by-products. The phthalic anhydride portion was the remaining percentage of 100%. In the downflow column, the reaction product from the cascade contained almost no naphthalene under vacuum.

Meanwhile, the naphthalene from this column was recycled in gaseous form through the evaporator back into the cycle gas stream of the naphthalene oxidation. In total, about 42 kg/hour of naphthalene was fed to the oxidation reactor for oxidizing naphthalene. The reaction mixture was fed to a scrubber column operated under 40 m Hg to separate crude phthalic anhydride as the column product and crude anthraquinone as the bottom product.

This column was of conventional construction and was a packed column. Because of the high temperature required, the bottom of the column was heated electrically. The bottom temperature of the tower is 28
It was 0q0. Crude phthalic anhydride was separated from the top of the column. An oil ring pump was used to create a vacuum. The amount of phthalic anhydride separated was approximately 22 k9/hr. Approximately 12 k9/hr of this amount was pumped back to a system for oxidative dehydrogenation of tetrahydroanthraquinone, as described above. Anthraquinone approx. 6k9/hr and high boiling by-products approx. 1
．． A product containing 5k9/h was obtained from the bottom of the column. This bottom product was fed to a conventional thin film evaporator. A coolable discharge screw was installed to smoothly discharge the high-quality byproducts. High-boiling products were obtained in solid or liquid form and removed from the process. Residual anthraquinone was separated from the mixture separated from this step by sublimation or extraction with xylene and subsequent crystallization. The thin film evaporator was operated under normal pressure to evaporate anthraquinone and release it as a gas. The device was electrically heated to achieve a high temperature of approximately 45,000 °C. A sludge column filled with packings and having a length of 1 m was installed on the thin film evaporator. The anthraquinone was purified under reflux in a rectification column according to known methods. The anthraquinone then exited the system first as a liquid, crystallized in a downflow cooling screw, and was removed. That is, the synthesis and purification of anthraquinone was completed. The crude phthalic anhydride obtained as by-product was now free of any remaining impurities.

Crude phthalic anhydride was fed to a column of conventional construction. The tower is 15
It was operated under a pressure of Qiu Cape Hg. More specifically, unknown low-boiling impurities were separated from the top of this column and recycled to the process stream of the Diels-Alder reaction. The bottom product from this column, which contains in addition to phthalic anhydride small amounts of unknown by-products, is fed to a further column where the phthalic anhydride is separated off as overhead product. This phthalic anhydride is now colorless. If necessary, further purification can be carried out by known methods. That is, the separation of the by-product, ie, phthalic anhydride, was completed. Alternatively, the crude phthalic anhydride can be purified by known methods by heat treatment, reaction with sulfur or treatment with sulfuric acid/boric acid or a combination thereof.

Ultra-rectification is also possible. Crude phthalic anhydride was separated from the bottom of the column in an amount of about 1 kg and recycled to the column for the oxidative dehydrogenation of tetrahydrophanethraquinone.

All cycles are therefore closed.

Namely, the following raw materials are used in the process: naphthalene, oxygen (
air), water vapor and butadiene. In addition to the actual reaction products, two streams were withdrawn from the process: a substream from the gas cycle and a bottom product from the thin film evaporator containing high-boiling components.

[Brief explanation of drawings]

The drawings show process diagrams for carrying out a specific example of the method of the invention. 1... Tubular reactor or oxidation system, 2... Rapid line system, 3... Reactor, 4... Distillation system or column, 5, 6, 7... ...Tower, 8, 9, 10, 11,
14, 17, 18, 19, 20, 21, 22, 28, 3
0, 31, 34, 37, 39, 42, 43, 45, 46
Conduit, 12 Conduit or feed naphthalene, 13 Gas, 15 Stream or conduit, 16 Conduit or liquid product, 23 Product stream, 24... conduit or feed mixture, 25
. . . partial stream, 26 . . . conduit or feed stream, 27 . . . conduit or anthraquinone-containing stream, 2
9,40...conduit or stream, 32...bottom or crude anthraquinone, 33...column top or crude phthalic anhydride, 35...conduit or top formation 36... Naphthalene, 38... Top product, 41... Stream, 44... Bottom product or stream.

Claims (1)

[Claims] 1 (A) oxidizing naphthalene with a gas containing oxygen and an inert substance in the presence of a vanadium-containing catalyst; (B)
In the cooler, from the reaction product obtained from (A), a liquid product containing essentially naphthoquinone, phthalic anhydride and naphthalene and a liquid product containing essentially oxygen, naphthalene,
carbon dioxide and the cycle gas containing inerts are separated and (C) the liquid product from (B) is reacted with excess butadiene, thus essentially producing tetrahydroanthraquinone, phthalic anhydride and obtaining a liquid product containing naphthalene, (D) consisting of a column having a rectifying section and a stripping section and a boiler, the stripping section and/or the boiler being of such construction as to prevent rapid flow-through of the feed mixture; A distillation system is fed with the product from (C), an oxygen-containing gas is fed into the lower part of the distillation system, and a naphthalene-containing gas is removed from the top of the distillation system, essentially containing anthraquinone, phthalic anhydride and The liquid mixture containing naphthalene is removed from the boiler, the naphthalene obtained at the top of the column is cooled and partially liquefied, and (E)
feeding the liquid mixture from (D) to a column which separates naphthalene at the top and a mixture containing essentially phthalic anhydride and anthraquinone at the bottom; The liquid mixture from (E) is fed to a column which separates at the top the mixture containing phthalic anhydride and the crude anthraquinone at the bottom; The overhead product from (F) is fed to another column which separates the acid together with the top and the phthalic anhydride together with impurities with a higher boiling point than the phthalic anhydride at the bottom; H) Feeding the bottom product from (G) to another column which separates substantially pure phthalic anhydride at the top and phthalic anhydride rich in high-boiling impurities at the bottom. and the new oxygen-containing gas is added to step (A) and/or
or (D), fresh naphthalene to step (B) and fresh butadiene to step (C), and the following circulation system: (a) oxygen-containing cycle gas from step (B); separated and a portion is recycled directly to (A) after optionally separating the naphthalene and removing a partial stream from the system, and the remainder of the recycled gas from step (B) is passed through step (D) to step (A). (b) circulating the naphthalene-containing gas from step (B) to step (A); and (c) circulating the naphthalene-containing gas from step (D).
) is recycled to step (A), and the naphthalene-containing gas from (
d) Transferring the naphthalene from step (E) to step (A) and/or
or recycled to step (B); (e) separating excess butadiene from the product from step (C) and recycling to the feed product of step (C); and (f) liquefying the product from step (D). (g) recycling some of the impure phthalic anhydride from step (F) to step (D) or upstream of step (D); (h) a portion of the overhead product and/or bottom product from step (G) and/or a portion of the overhead product from step (H) into the feed product of step (C); (i)
A process for producing anthraquinone, comprising recycling the bottom product from step (H) upstream to step (D). 2 Naphthalene 1-5% by volume, oxygen 1-10% by volume, water vapor 1-12% by volume, carbon dioxide 0-12% by volume, carbon monoxide 0-3% by volume, sulfur dioxide 5-50 ppm and nitrogen 100%. 2. A method according to claim 1, wherein in (A) a gas mixture containing the remaining percentage of . 3 In step (A), the gas mixture is flowed at a flow rate of 0.5 to 5 m.
3. The method according to claim 1 or 2, which uses a reaction tube which is passed through the tube at a rate of 1 to 9 seconds and a residence time of 1 to 9 seconds. 4. The method according to any one of claims 1 to 3, wherein step (A) is carried out at a temperature of 280 to 450°C. 5. In step (B) a quencher is used, which has a high liquid circulation, from which the liquid product is withdrawn at a temperature below 150 °C, and downstream there is a gas scrubber that countercurrently scrubs the circulating gas with naphthalene. A method according to any one of claims 1 to 4. 6 Using 2 to 20 mol of butadiene per mol of naphthoquinone in step (C), carrying out the reaction at a temperature of 90 to 200 °C, a residence time of 10 to 300 minutes, and a pressure of 5 to 50 bar, the naphthoquinone-containing naphthalene and/or phthalic anhydride The method according to any one of claims 1 to 5, which is carried out by adding an acid. 7 In step (D), a distillation system consisting of a column and a boiler having a rectification section and a stripping section is used, and the stripping section and/or boiler has a total residence time of 1
7. A process according to claim 1, wherein the distillation system is operated at a pressure of 1 to 20 bar and at a temperature at which the naphthalene evaporates.