WO1999033802A1

WO1999033802A1 - Method for isolating carbazole and production of 9,10-dihydroanthracene from raw anthracene

Info

Publication number: WO1999033802A1
Application number: PCT/EP1998/008218
Authority: WO
Inventors: Peter Heymanns; Kurt Schalapski; Edgar Fuhrmann; Jörg Talbiersky
Original assignee: Celanese Chemicals Europe Gmbh; Rütgers Vft Ag
Priority date: 1997-12-23
Filing date: 1998-12-15
Publication date: 1999-07-08
Also published as: DE19757530C2; ZA9811724B; DE19757530A1

Abstract

The present invention makes it possible to isolate carbazole and to produce simultaneously 9,10-dihydroanthracene from raw anthracene containing anthracene, carbazole, and phenanthrene. The method comprises a suspension crystallisation stage for the raw anthracene whereby enriched raw anthracene is formed, hydrogenated after separation and subsequently undergoes solvent crystallisation. The crystallised product thus obtained contains at least 90 % carbazole.

Description

Process for the isolation of carbazole and production of 9, 10-dihydroanthracene from crude anthracene

The present invention relates to a process for isolating carbazole and to producing 9, 10-dihydroanthracene from crude anthracene, comprising the partial hydrogenation of enriched crude anthracene and a subsequent solvent crystallization of the hydrogenation product of the enriched crude anthracene.

In technical coal tar distillation, in addition to light oil, medium oil, heavy oil and pitch, the so-called anthracene oil is obtained in the boiling range of 270-400 ° C. This crude anthracene oil is cooled and the crystal mass which separates out is separated off by filtration or centrifugation. In this way two crude products are obtained, the crude anthracene and the filtered or centrifuged anthracene oil. In addition to anthracene, crude anthracene mainly contains carbazole, phenanthrene and fluorene.

Carbazole is used in the manufacture of various dyes, insecticides and vinyl carbazole. Also of industrial importance is a partial hydrogenation product of anthracene, 9, 10-dihydroanthracene, which serves as a starting material for the production of anthraquinone. There is therefore increased interest in obtaining these two substances, carbazole and 9, 10-dihydroanthraquinone.

Obtaining carbazole from crude anthracene via a crystallization step presents problems, since carbazole and anthracene always crystallize out together in a certain ratio to one another. Extractive processes for separating carbazole from anthracene oils are known from the literature.

In Koks, Smola, Gaz (1986), 31 (4), 65-7, it is described that crude anthracene is first separated from the anthracene oil and then this anthracene oil is separated to obtain carbazole and anthracene. The crude anthracene is separated from the anthracene oil by a crystallization step using methanol and hydrocarbons in the form of paraffins, aromatic alkyl hydrocarbons and naphthenes as solvents. The crude anthracene crystals formed during the crystallization can be separated from the mother liquor by conventional separation methods such as filtering or centrifuging. The crude anthracene is then extracted with N-methylpyrrolidone and optionally 10% water in two stages at temperatures so low that only a little anthracene dissolves in the N-methylpyrrolidone, while the other components of the crude anthracene, especially carbazole and phenanthrene, with the N- Form methylpyrrolidone complexes and can be separated. The carbazole can be obtained from the extractant in two ways. On the one hand, a carbazole / phenanthrene fraction can first be separated off by adding water, from which crude carbazole is subsequently extracted with pyrolytic oil as the extractant and finally recrystallized. Secondly, the N-methylpyrrolidone can first be driven off from the N-methylpyrrolidone extract and the distillation residue can then be subjected to a fractional crystallization from pyrolytic oil in order to separate carbazole and phenanthrene. The main disadvantage of this multi-stage process is its complexity. Since the carbazole content in the crude anthracene used for the extraction is also relatively low and is, for example, only 10% by weight large quantities of solvents are required in the various extraction steps, which reduces the economic attractiveness of the process.

The object of the present invention is to provide a new and more efficient process which makes it possible to provide both carbazole and 9, 10-dihydroanthracene from crude anthracene in a simple manner with high selectivity and, at the same time, good overall yield.

This object is achieved by a process for isolating carbazole and producing 9, 10-dihydroanthracene from crude anthracene which contains anthracene, carbazole and phenanthrene, comprehensively

(1) the use of the raw anthracene together with a residual oil from the pure naphthalene production in a suspension crystallization to form a crystal material from enriched raw anthracene, (2) separation of this crystal material from enriched raw anthracene from the mother liquor,

(3) partial hydrogenation of the separated crystal material from step (2) in the presence of a sulfur-resistant catalyst to give a hydrogenation product and

(4) working up the hydrogenation product from step (3) by solvent crystallization to form a second crystal product which contains at least 90% carbazole.

The crude anthracene used in the process according to the invention usually originates from the working up of carbo-derived crude tar and contains anthracene, carbazole and phenanthrene and optionally fluorene. Preference is raw anthracene, which contains 20-50% by weight, in particular 30-40% by weight, anthracene, 10-40% by weight, preferably 20-30% by weight. and in particular 20-25% by weight of carbazole, 15-30% by weight, in particular 20-30% by weight of phenanthrene and 0-15% by weight, in particular 3-6% by weight of fluorene. The crude anthracene may also contain methylfluorenes, methylphenanthrenes, methylanthracenes.

In addition, small amounts of sulfur, e.g. in the form of diphenylene sulfide, usually in the range from 1000 to 5000 ppm, corresponding to 0.1 to 0.5%.

The residual oil from pure naphthalene production used in the suspension crystallization together with the crude anthracene is referred to as so-called naphthalene drip oil and preferably contains 30-60% by weight, in particular 40-50% by weight, naphthalene, 10-30% by weight, in particular 20-30 % By weight, methylindene, 1-10% by weight. , in particular 1-5% by weight, methylnaphthalene and 1-10% by weight, in particular 4-8% by weight, indene.

The suspension crystallization of the crude anthracene together with the residual oil of the pure naphthalene production according to step 1 of the process according to the invention is carried out by first heating the residual oil of the pure naphthalene production in a stirred vessel to a temperature of 100-180 ° C., then adding the raw anthracene and at the temperature of 100 - Stirring 180 ° C until the raw anthracene has dissolved. The solution is then cooled to a temperature of 50-100.degree. C., preferably 60-90.degree. C. over a period of 3-6 hours, the enriched crude anthracene crystallizing out as crystal material.

The resulting from the suspension crystallization

According to step (2) of the process according to the invention, crystal material is removed from the mother liquor, i.e. the supernatant

Solution separated. This separation is usually carried out in a centrifuge, which is preferably heated. The separated mother liquor can be used as a mixing component for the production of technical aromatic oils without further treatment.

The isolated crystal contains essentially carbazole and anthracene. For the successful further course of the overall process, it is crucial that the proportion of all other components contained in the crude anthracene, such as phenanthrene, fluorene, methylfluorenes, methylphenanthrene and methylanthracenes, is considerably reduced by the suspension crystallization. The crystal material of the suspension crystallization is therefore also referred to as enriched raw anthracene. The crystal of enriched crude anthracene preferably contains 35-60% by weight, preferably 50-60% by weight and in particular 50-55% by weight of anthracene, 15-40% by weight, preferably 30-40% by weight. and in particular 30-35% by weight of carbazole, 1-25% by weight, preferably 1-10% by weight and in particular 1-5% by weight of phenanthrene and 1-8% by weight, preferably 1-5% by weight and in particular 1-3% by weight fluorene. This means that the enriched raw anthracene can consist of up to 95% carbazole and anthracene. The carbazole yield of the suspension crystallization is 65-75%, based on the carbazole in the crude anthracene.

The crystal material separated from enriched crude anthracene separated in step (2) is subjected in step (3) to a partial hydrogenation in the presence of sulfur-resistant hydrogenation catalysts.

Preferred sulfur-resistant hydrogenation catalysts are sulfide-activated catalysts which, in addition to oxides of metals from group VIII of the periodic table, contain tungsten or molybdenum oxide. These catalysts are preferably on a support material such as aluminum oxide, silica or mixtures thereof applied. Furthermore, the catalyst can contain basic promoter oxides, which are selected from groups IA, IIA, the lanthanides and the actinides of the periodic table. Sulfidated Co / Mo, Ni / Mo or Ni / W catalysts are particularly suitable. The sulfidation of the catalysts before use in the hydrogenation is preferably carried out using dimethyl disulfide. The sulfided catalyst is usually used as a fixed bed in the subsequent hydrogenation experiments.

Suitable catalysts are described, for example, in US Pat. No. 4,720,477, EP-A-0 389 119, EP-A-0 082 726 and EP-A-0 046 634. The disclosure of these catalysts in the cited documents is hereby specifically referred to ("incorporation by reference").

The hydrogenation of the enriched crude anthracene can be carried out continuously or batchwise. Work is preferably carried out batchwise. For this purpose, the enriched crude anthracene is placed in a reaction vessel, for example a stirred autoclave, mixed with the suspended form of the sulfided catalyst and the mixture is melted while heating to 170-220 ° C., preferably 190-210 ° C. The sulfidated hydrogenation catalyst is used in an amount of 5-10%, based on the entire reaction mixture. The hydrogenation is carried out at a reaction temperature of 150-300 ° C., preferably 240-290 ° C. and a reaction pressure of 40-100 bar, preferably 50-70 bar hydrogen and a reaction time of 2-8 h, preferably 4-5 h .

In this partial hydrogenation, the anthracene portion of the crude anthracene is selectively and largely completely hydrogenated to 9, 10-dihydroanthracene, while the carbazole portion of the crude anthracene remains unchanged. The hydrogenation product of the enriched crude anthracene from step (3) is worked up in step (4) by solvent crystallization. For this purpose, the hydrogenation product is dissolved in an aromatic solvent, preferably by raising the temperature to 70-130 ° C. BTX aromatics (benzene / toluene / xylene) are preferably used as aromatic solvents. The solution obtained is then cooled to a temperature of 0-30 ° C. with stirring. The second crystal material formed in the solvent crystallization is separated off by filtration, optionally with a subsequent washing step, and dried. The selectivity of this solvent crystallization with respect to the carbazole is excellent. The crystal contains at least 90% by weight, preferably at least 95% by weight and in particular at least 96% by weight of carbazole.

For the overall process there is a carbazole yield of 63-72%, based on the carbazole in the crude anthracene used.

Only by connecting steps (1) to (4) in series in the process according to the invention is it possible to isolate the carbazole in the yields mentioned. The suspension crystallization is characterized in that the substances contained in addition to carbazole and anthracene in the raw anthracene and also referred to as ballast components are removed in a targeted manner, with a simultaneous increase in the carbazole and anthracene content in the enriched raw anthracene. Since at least some of the ballast components would be accessible for hydrogenation, their absence or only a low concentration in the enriched crude anthracene means that a smaller amount of hydrogen is required in the hydrogenation. At the same time, a higher mass throughput of the target compound carbazole can be achieved in the hydrogenation. Both Effects make a positive contribution to the economy of the overall process.

Accordingly, the subsequent solvent crystallization is only so excellent because the hydrogenation product of the enriched crude anthracene which occurs contains, apart from carbazole and 9, 10-dihydroanthracene, only small amounts of other hydrogenated or non-hydrogenated dietary fibers which could negatively influence the quality of the crystallization.

Examples;

I suspension crystallization of crude anthracene with naphthalene dropping oil

1000 g of naphthalene drip oil of the composition given in Table la are placed in a 4 L stirred container and heated to 170 ° C. A total of 1000 g of crude anthracene of the composition given in Table 1b are then added in portions and completely dissolved at 170 ° C. The solution is then cooled to 80 ° C. with stirring over a period of about 4 hours, an enriched crude anthracene crystallizing out. The entire crystal suspension is transferred to a centrifuge heated to 80 ° C., in which the crystal material from enriched raw anthracene is separated from the mother liquor. This gives 457 g of crystal material of the composition given in Table 1. Table 1a:

Table l:

II Discontinuous hydrogenation of enriched

Crude anthracene according to step 3 of process a) sulfidation of the hydrogenation catalyst

In Examples II-3, 7 and 8 below relating to the hydrogenation step, Co / Mo catalysts with 4% cobalt oxide and 14.5% molybdenum oxide are used on an aluminum oxide support. These are commercial products from BASF AG with the designations BASF M8-12 and M8-14. In Examples II-1, 2, 4, 5 and 6, a Ni / Mo catalyst with 1-10% cobalt oxide and less than 25% molybdenum on an alumina / silica support is used.

Before the hydrogenation catalysts are used, they are subjected to sulfidation in the presence of dimethyl disulfide subject. Here, the catalyst placed in a 2 L reaction tube with 1.5 kg of a 67% solution of dimethyl disulfide in 38 kg mineral oil at 225 to 300 ° C under a hydrogen atmosphere (240 L exhaust gas / h) at a throughput of 1.0 V / Vh ( Volume of liquid educt (enriched raw anthracene) / (volume of catalyst xh)) sulfurized over 15 hours. The temperature gradient between 225 and 300 ° C is 3 ° C per hour.

b) hydrogenation

The hydrogenation of the enriched crude anthracene is carried out batchwise in a stirred autoclave. The composition of the enriched crude anthracene used as the starting material is shown in Table 2. The enriched crude anthracene used in Example II-1 is the product obtained in the suspension crystallization described under point I.

First, the enriched raw anthracene present as crystal is introduced into the stirred autoclave. The hydrogenation catalyst is then added in suspended form and the mixture is melted while heating to 200.degree. The amount of catalyst used in the respective experiments and the other reaction conditions, such as reaction temperature, reaction pressure and reaction time, are shown in Tables 3, 4 and 5.

Table 3 -. Example II-1

Tabe.1 3; Examples II-2 and 3 (variation of the catalyst)

Table 4: Examples II-4-6 (variation of the reaction pressure)

Tab l 1 e: Example II-7 and 8 (variation of the reaction time)

III solvent crystallization of that obtained in II

Hydrogenation product of the enriched raw anthracene

100 g of the hydrogenation product of the enriched crude anthracene from Example II-1 with the composition given in Table 6 are dissolved in 400 mL toluene at 100 ° C. The solution is then cooled to 20 ° C. with stirring. The precipitated crystal is separated from the mother liquor by filtration, covered with 40 mL fresh toluene and then dried. The composition of the crystal is given in Table 6. It contains 97.4% carbazole.

Table 6

Claims

claims

1. Process for the isolation of carbazole and preparation of 9, 10-dihydroanthracene from crude anthracene, which contains anthracene, carbazole and phenanthrene, comprising

(3) partial hydrogenation of the separated crystal material from step (2) in the presence of a sulfur-resistant catalyst to obtain a hydrogenation product and

2. The method according to claim 1, characterized in that the raw anthracene 20-50 wt.%, In particular 30-40 wt.% Anthracene, 10-40 wt.%, Preferably 20-30 wt.% And in particular 20-25 wt. % Carbazole, 15-30% by weight, in particular 20-30% by weight of phenanthrene and 0-15% by weight, in particular 3-6% by weight, of fluorene.

3. The method according to claim 1 or 2, characterized in that the residue oil used in the suspension crystallization together with the crude anthracene of the pure naphthalene production 30 - 60 wt.%, in particular 40-50% by weight, naphthalene, 10-30% by weight, in particular 20-30% by weight, methyl indene, 1-10% by weight, in particular 1-5% by weight, methylnaphthalene and 1-10% by weight , In particular 4-8% by weight, contains indene.

4. The method according to one or more of claims 1 to 3, characterized in that in the suspension crystallization, the residual oil of pure naphthalene is first heated in a stirred tank to a temperature of 100-180 ° C, then the crude anthracene is added and at the temperature of 100- 180 ° C is stirred until the crude anthracene has gone into solution and then the solution is cooled to a temperature of 50-100 ° C, preferably 60-90 ° C within a period of 3-6 h.

5. The method according to one or more of claims 1 to 4, characterized in that the crystal material from enriched raw anthracene 35-60 wt.%, Preferably 50-60 wt.% And in particular 50-55 wt.% Anthracene, 15-40 wt .%, preferably 30-40% by weight and in particular 30-35% by weight carbazole, 1-25% by weight, preferably 1-10% by weight and in particular 1st

- 5% by weight phenanthrene and 1 - 8% by weight, preferably 1

- 5% by weight and in particular 1 - 3% by weight of fluorene.

6. The method according to one or more of claims 1 to 5, characterized in that sulfide-activated catalysts are used in the hydrogenation step (3), which contain oxides of metals from group VIII of the periodic table of tungsten or molybdenum oxide.

7. The method according to claim 6, characterized in that the catalysts are applied to alumina, silica or mixtures thereof as support material and contain basic promoter oxides which are selected from groups IA, IIA, the lanthanides and the actinides of the periodic table.

8. The method according to claim 6 or 7, characterized in that sulfided Co / Mo, Ni / Mo or Ni / W catalysts are used.

9. The method according to one or more of claims 1 to 8, characterized in that the hydrogenation of the enriched crude anthracene in step (3) continuously or discontinuously and at a reaction temperature of 150-300 ° C, preferably 240-290 ° C, and a reaction pressure of 40-100 bar, preferably 50-70 bar, hydrogen and a reaction time of 2-8 h, preferably 4-5 h.

10. The method according to one or more of claims 1 to 9, characterized in that the hydrogenation product for solvent crystallization in an aromatic solvent, preferably with increasing the temperature to 70 - 130 ° C, and then dissolved with stirring to a temperature of 0 - 30 ° C. is cooled.